S3 EP3: A Journey to the Blinking Nebula

Hello and welcome back to episode 3 of Season 3 of this astronomy podcast. Today, we are going on another adventure but this time it’s a journey to a Nebula called Blinking Nebula but before we dive into this, let’s talk about what is a nebula?

Nebula is a place where stars are born. They are usually called stellar nurseries where stars are born in a group. It’s like cultivating seeds of plants in a nursery but in terms of astronomy, stellar nursery is a place where stars are born in a group from a massive cloud of gas and dust. It’s also a place where stars die. In other words, nebula is a part of cycle in which the material gets recycled by the universe. If it still sounds complicated then let me start by giving you an example. Let’s take our Sun. What do you think about how it formed? Has it always been around revolving the supermassive black hole at center of our galaxy? Nebula can be of many types but this is not what we will dive into today. The kind of nebula that I will talk about is a Planetary Nebula. Yes, Blinking Nebula is a Planetary Nebula, also known as NGC 6826 in the NGC astronomical naming catalog. It is also known as Caldwell 15 in the Caldwell catalog. Now you might be wondering about what exactly is a Planetary Nebula. To put it into simple words, a planetary nebula is a nebula formed after the death of a star massive than our Sun in an explosion called Supernova. If a star’s mass is bigger than Chandrasekhar limit, then it will go and become either a black hole or a neutron star as a result of this explosion but since this isn’t a black hole or a neutron star, this is a planetary nebula. In other words, this was formed after a Star with mass less than that limit. To put it into much simpler words, a planetary nebula is an expanding shell of gas and dust into the outer space. It happens when the star runs out of fuel and collapses under the weight of its gravity and since the fate depends on the mass of a star, the star then ends its life in form of a explosion by expanding its shells outwards, leaving a core at the center, which in astronomical terms is called a white dwarf star. It is the third stage of fate for a main-sequence star like our Sun, which means our star too will someday face a death like this. It is the third stage since it comes after the Red Giant phase in which the star expands but doesn’t collapse and goes into explosion. It is after this phase the white dwarf stage arrives. Now that you know the basics, when I’m saying planetary nebula, I meant an expanding cloud of gas and dust after supernova, thus leaving the core of star at the center. Now back to Blinking Nebula.

Blinking Nebula is located about 2200 light years from Earth in the constellation Cygnus. It is referred as the Blinking Nebula because of its pattern of blinking from the observer’s view when viewed through the telescope. What I meant by that is if you were to take a small telescope and see at this nebula directly, the light from the white dwarf HD 186924 will obscure the colorful light of the surrounding nebula. To you, then it won’t appear as a nebula but rather a bright star. However, you can view it with an averted vision. This causes the blinking effect in the eyes of observer as his eyes wanders. It doesn’t actually blink in space. This nebula was discovered in the year 1793 by the astronomer William Herschel and is about only 1000 years old.

This is all from me for this episode. We will meet again with a new episode!

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S3 EP2: Iapetus, Moon of Saturn

Welcome back to episode 2 of Season 3 and today we are going on another adventure but this time it’s far beyond Moon to another Moon in our solar System. Today, I will tell you about a very fascinating moon of Saturn called Iapetus.

Saturn is the second biggest planet but with the largest number of Moons parked around its orbit. As of March 2025, there are a total of 274 known Moons orbiting around Saturn and there could be more in as more data is being processed which was gathered from previously sent missions like Cassini. Iapetus is one of many Moons of Saturn that is known to exist for more than 350 years to us. It was discovered on October 25, 1671 by an Italian astronomer Giovanni Cassini. It was discovered at the Paris Observatory and at the time of discovery was the second known moon of Saturn after Titan which was discovered in 1655. It was also the 6^th known moon found in our solar system. Now moving forward to the story of discovery, which is quite interesting and easy to understand if you know the meaning of the term “tidally-locked”. Okay let me help you recall. In Astronomy, when we say an object is tidally-locked, we mean that it is locked in the orbit of the object it is revolving around. In other words, a tidally locked object is something that only shows its one side towards the object it is facing. The other side remains facing outwards in opposite direction and we can’t see it from our point of view. Still confusing, pardon me for my English but let me try to make it even easier for you with an example. Our own Moon is tidally-locked with Earth because we only see its one side facing us. The other side is dark and facing towards the outer space. The same case is with Iapetus, which is tidally locked with Saturn. This has one of the huge role in the discovery of this moon.

Back in October 1671, when Giovanni Cassini pointed his refractive telescope at Saturn, he discovered an object appearing to be hanging in the orbit around Saturn. This was discovered in the western side of Saturn from our point of view. So when it was revolving around Saturn, it was in the western side and very clear from our point of view. To confirm his predictions, Cassini tried to look for it again few months later but this time it was nowhere to be found on the eastern side. Why was it happening? Did something swallow it? Obviously the concept of black hole was unknown at that time but he tried it again but this time with a much improved telescope. He pointed it again on the eastern side of Saturn and there it was in orbit around Saturn. It had not gone anywhere, it was there the whole time but the reason for it was very easy to understand. The side that was facing towards us on the western side is icy and reflects back a lot of light but on the other side, when it reaches on the eastern side of the planet, we were met with a much darker side that does not reflects any light. However, you must not forget that Iapetus is tidally-locked and only we can observe it’s both sides from our point of view but to anybody standing on the Saturn (only if it was possible), you can only see one side of the Moon.

Iapetus is the third largest moon of Saturn and 11^th largest in our Solar System. Unlike other moons like Europa, it does not have any ocean beneath its icy surface. This icy world is about 1469 km in diameter. A day here is about 79 Earth days long. Apart from these facts, there is one more feature about this Moon which makes it standout against other natural satellites discovered so far. Iapetus is a walnut shaped moon because of an equatorial ridge that runs along the equator for about 1300 km long and it is about 20 km wide and 13km high, much higher than the Mt. Everest on Earth. Because of this height of Ridge and its distance, this gives Iapetus a walnut like shape. Without any hypothesis, this wouldn’t be actually part of Astronomy. So yes there is one that I like the most which is that there used to have a ring system around Iapetus, which later fell around its equator. Thus, the equatorial ridge was formed.

Another question that rises here is have we ever visited this world before? And the answer is both yes and no. There has never been any specific mission to this Moon before but flyby have happened in the part as part of missions like Cassini. The first attempt to study Saturn and its moon happened with Pioneer-11 mission but it didn’t came that closer to it. The next series of mission Voyager-1 and Voyager-2 and with this Voyager-1 made history as it became the first ever spacecraft to ever send back a picture of Iapetus two tone surface. That is the picture gave us more details about its dark and icy sides surface. But the closer study of its surface wouldn’t happen till December 31, 2004 when Cassini spacecraft made its first targeted flyby around Iapetus. The closest and last flyby of Iapetus by Cassini happened in September 2007 and after that it never made any contact with the Moon. Data from Cassini showed that its surface is heavily cratered and has a massive impact basin about 580 km in diameter. This was from me for this month’s story. I will be back next month with another episode. Thank you!

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S3 EP1: NASA's Return to Moon with Artemis-II

What a great time to start the new season. Hi, I’m your host Maanvinder and today we’re going on a journey to the moon. Not physically but just use your imagination and let it run wild. I hope you have already gotten your boarding pass from NASA because I have already got mine. Today’s topic is the Artemis Mission. I have talked about this previously but it was for a blog I no longer contribute to. Sad, right? So, tight your seatbelts because it’s time to take off again.

With Artemis, NASA marks its return to the beautiful moon parked in the orbit of our planet Earth. This is a mission that is to be carried in 3 different programs: Artemis-I, Artemis-II, Artemis-III. Sadly, I was not here to talk about Artemis-I, which had already happened back in the year 2022. It was an uncrewed flight around the orbit of moon. But now I’m here at the right time for Artemis-II. The reason why this mission is called Artemis is because in the Greek mythology Artemis is the goddess of Moon and Apollo is the twin sister of Artemis. Since Apollo was a mission to Moon, NASA decided to call their new mission as Artemis, to keep remembering the contribution from Apollo missions. The main goal of the Artemis mission is to land the first woman and first person of color on the lunar South Pole to study the lunar surface. It is NASA’s first mission in more than 50 years that involves humans and lunar surface. To be exact, the first crewed mission since Apollo 17 in 1972. Before you understand what this Artemis-II mission is about, you need to understand what Artemis-I was about.

Artemis-I which was launched in November 2022 was an uncrewed mission to the Moon, in which NASA tested the Space Launch System- a rocket capable of carrying more than 180,000 kg of weight and Orion Module, which is the most important part related to Artemis-II. It is because this Orion is a spacecraft attached to the Space Launch System (SLS) that will carry the astronauts to the Moon. It will have life support system for the crew of the mission. So what really happened in the Artemis-I? When this mission was first launched, it was to test the SLS and Orion Spacecraft. What happened really was once it was launched into the space; SLS detached itself from Orion, then Orion went on a journey around the Moon and finally ended with its splashdown into the Pacific Ocean. It was a test flight, which means there were no humans onboard. This was a major step to guarantee the success of Artemis-II, since it involves a group of astronauts who will stay in orbit around Moon to study and gather flight data. You should not confuse Artemis-II with humans landing on Moon because it will take time. In simple terms, it is another test flight but with humans onboard. The landing of humans will only happen in Artemis-III program, which is yet to happen based on the results of Artemis-II. The initial date of launch for Artemis-II is February 6, 2026 which might change depending on weather conditions. The mission will last about 10 days by ending the flyby around Moon with a splashdown of Orion into pacific again, while carrying the crew.

Now you might think we are doing this all just to carry some humans into orbit around Moon who won’t even land on surface. But here is the real twist, with this mission NASA is aiming much higher that is a mission to Mars. That is why, after the success of Artemis-II mission, NASA plans to build a station around the orbit of Moon. It will be called “Lunar Gateway, and European Space Agency is working on it with NASA. The main work of this small space station will be to act like a platform for the missions to the Moon or possibly even to the Mars. In this, Astronauts will use Orion to fly and dock with the space station in the orbit and then later transfer into the Lunar Landing Module to get onto the surface of the Moon. Lunar Landing Module is basically a vehicle that will carry astronauts to the surface of the moon. This is basically how Artemis-III will happen. The landing module that was designed for Apollo missions was for only one journey to the Moon’s surface but this one will be used for multiple missions.

Back to Artemis-II, the four astronauts that are set to onboard this are: Reid Wiseman, Victor Glover, Christina Koch and Jeremy Hansen from the Canadian Space Agency. With this Christina will become the first woman to travel to the Moon and Glover will become the first person of color who traveled to Moon. Apart from carrying astronauts, Artemis-II will also be carrying 4 CubeSats from different countries. A CubeSat is a small satellite that is about the size of a shoe-box and is capable of studying the environment of space. The main goal is to deploy these into High Earth Orbit when SLS and Orion are separated.

To summarize this, Artemis-II will be the first mission of NASA in more than 50 years that will carry humans to the Moon. It will be a flyby around our natural satellite that will end with the splashdown into the Pacific Ocean. The success of this mission will decide the trajectory of Artemis-III, which involves landing on the surface of Moon. This is all I have to share with you now. Until we meet again. Stay tuned in.

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Season 3 Announcement

Hello folks,

As the title suggests i'm here to announce the Season 3 but its not just that. You see back in 2024, i had decided to end this podcast with Season 2. This was pretty much the case throughout the entire 2025 but something changed a few days ago. Tomorrow is an very important day in my life and i want to celebrate its arrival with something related and important to me. This is getting way too poetic but what can i do when i'm a poet. I'm here to announce the new season of my podcast "Astrophysics: Deep In The Space With Maanvinder Pilania". In terms of episode, it will be equivalent to Season 2 but with one less episode. In other words, there will be 10 episodes and one special episode. I cannot wait to share what i have in store for you all. 

Thank You

Maanvinder

Stream*

Spotify for Podcasters: https://podcasters.spotify.com/pod/astromaanvinder/

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Spotify Wrapped: 2025

Hey everyone, I'm your host Maanvinder. I'm here to share the Spotify wrapped of my podcast and thank to anyone who listened it. Thank you for sharing your time to listen my horrible voice. It was amazing considering i didn't released any episode this year because i decided not to record any. The top episode was obviously the second special episode from Season 2.

Special EP: Stellar Outcasts Rogue Planets

Hello and welcome back to the last episode of this podcast and as I promised in one of the earlier episodes, I’m back with an detailed episode on Rogue Planets but with that it is time to bid farewell. I’m uncertain whether I will record any new episodes in future or not however I shall continue my passion of being an amateur astronomer. That’s why I will be focusing on writing rather than recording. So with the end of this episode, the podcast will be halted for an uncertain time because I will be busy with my blog called “Astronomia Oggi”, which when translated from Italian means “Astronomy Today” in English. So before any further delay let’s dive into another adventure through cosmos.

Rogue planets are planets with no parent star. So in other terms, they are orphan planets which are drifting across the space without any host star to revolve around. It could happen due to various reasons. They are just like other planets which means they can be gas giant, terrestrial or any other type. The only thing they’re missing is the star from whose leftovers in a planetary disk they were formed. So what caused them to become rogue, leaving them in the eternal darkness of the space and will you be able to survive on such planet. Let’s talk about what made them lone exoplanets.

Now I’m going to tell you about the reasons that certainly explain the reason behind them floating across the vastness of space. First it could have been ejected from its star system due to gravitational interactions with passing star and even other planets in its own star system. The other reason could be they formed from the proto-planetary disk of a star and without getting bound to the star and eventually getting ejected from the star. Like I mentioned earlier about them being of any type, it also means their mass range is also different. They can range from Earth sized to several times the mass of our local neighbor Jupiter.

So the next question that arises here is will you be able to survive on such planet? The answer is simply no. There are two reasons that are related to absence of an host star. In episode 4 of this season, I talked about Neptune’s moon triton and how it is able to keep it slightly warm or just keeping it geologically active. In case of Triton, it is located in far reaches of solar system where Sun’s light is not enough to keep it warm, thus keeping a liquid ocean beneath its nitrogen surface. So it derives most of its heat from the tidal interactions with Neptune which keeps its geologically active by means of Cryovolcanoes on its surface. So the question I wanna ask you here is that is it possible in case of a planet, let’s say a terrestrial one? The simple answer is no. As a rogue planet does not have an companion, so it will be so cold. However, the case of Triton is possible if a rogue planet has its own natural satellite and normally as interstellar space is full of cosmic rays and all sorts of other rays, it would be stripped of its atmosphere meaning if it have any ice on its surface, will be sent into the space. Now let’s consider the other reason which is of course the absence of a host star, means the planet will be much colder and darker and if somehow the planet kept hold of its atmosphere, there is no chance for life to thrive at such a place. So are these two conditions the only way life can survive? Some rogue planets could have a subsurface ocean that is kept warm by internal heat or radioactivity of a planet, raising the possibilities of habitability. The universe is a wild place with possibilities that are beyond one’s imagination.

According to an estimate, there are about 20 rogue planets for every star in a galaxy and imagine putting this number in the total estimate of stars in our Milky Way alone which is more than 200 billion stars. The number of rogue planets are huge in the universe, it’s like they are seeds of an plant which failed to grow up scattered in a field along with the grow up ones that are now plants. And this brings me to the last question that is probably in your mind. How do we know they exist? Or how they are detected?

Since they don’t have any host star to orbit, you cannot detect them via transit method or radial velocity. They are dark due to the fact neither they nor they have any light of their own nor are visible against the backdrop of space. However, they can be detected via gravitational microlensing, a method which I explained in the episode about exoplanets. You might wanna check it out, in case you don’t have any clue about it.

In case you are wondering about future observations or detection of such planets, then NASA has come up with an answer to it with their new space telescope called The Nancy Grace Roman Space Telescope. It will use gravitational microlensing to detect new rogue planets in deep regions of the Milky Way. Its wide angle view is 100 times bigger than that of the Hubble Space Telescope. Imagine how this new telescope will revolutionize our understanding about these lone planets and if its combined with the James Webb Space Telescope, they might tell help us improve our understanding of them. In any case I take my leave here for an uncertain time but you can find my new work at Astronomia Oggi Blog.

S2 EP10: A Trip to Martian Moons

Hello and welcome back to the podcast! In today’s episode, we’re going to take an exciting trip to Mars—but not to the red planet itself. We’re heading to Mars’ moons, Phobos and Deimos. These two tiny moons are just as fascinating as Mars itself, and they’re full of mysteries waiting to be explored. So, let’s buckle up for a trip to Mars’ moons!

A Quick Introduction to Mars and Its Moons

Before we get into the details of Phobos and Deimos, let’s talk about Mars itself. As you probably know, Mars is the fourth planet from the Sun and is often called the "Red Planet" because of its reddish appearance, caused by iron oxide, or rust, on its surface. But what’s less known is that Mars has two small moons orbiting it—Phobos and Deimos. These moons are much smaller than our own Moon, and their shapes are irregular, almost like asteroids. In fact, they’re thought to be captured asteroids from the asteroid belt between Mars and Jupiter. So, let’s start by talking about Phobos, the larger of Mars' two moons.

Phobos: The Larger Moon

Phobos is the larger and closer of the two moons. It’s about 22 kilometers (or 13.6 miles) in diameter, which is tiny compared to our Moon, which is about 3,474 kilometers (2,159 miles) wide. Phobos orbits Mars so closely—only about 6,000 kilometers (or 3,700 miles) above the Martian surface—that it’s actually moving closer to Mars every year. In fact, Phobos is gradually spiraling in toward Mars, and in about 50 million years, it’s expected to either crash into Mars or break apart and form a ring around the planet. Pretty wild, right? One of the most interesting features of Phobos is its strange surface. It’s covered with craters, and the largest one, called Stickney Crater, is about 9 kilometers (5.6 miles) across—almost half the size of the moon itself! Phobos’ surface also has grooves and ridges that make it look like it’s been stretched or pulled by Mars’ gravity over time. It’s almost as if this moon is slowly being torn apart by the planet’s powerful gravitational pull.

Deimos: The Smaller Moon

Now, let’s move on to Deimos, the smaller and more distant of the two moons. Deimos is only about 12 kilometers (7.5 miles) in diameter, making it even smaller than Phobos. It orbits much farther from Mars—about 23,460 kilometers (14,580 miles) away—about six times farther than Phobos. Unlike Phobos, Deimos moves slowly away from Mars over time. Deimos has a much smoother surface than Phobos. It doesn’t have the deep craters that Phobos does, but it’s still covered with smaller ones. It’s thought that Deimos is made mostly of rock and ice, with its surface coated in a layer of fine dust. Because it’s so far from Mars and its gravity isn’t as strong, Deimos doesn’t experience the same stretching and pulling forces that Phobos does. Instead, it’s just quietly orbiting around Mars, with no big dramatic changes.

How Did Phobos and Deimos Form?

One of the biggest questions scientists have about Phobos and Deimos is how they came to be. Since they are much smaller than Earth’s Moon and have irregular shapes, scientists think they may have been captured by Mars’ gravity. They could have been asteroids floating around the solar system, and Mars’ gravity pulled them in, trapping them in orbit around the planet. This theory is supported by the fact that both moons are made of similar materials to objects found in the asteroid belt. However, there’s another theory that suggests that Phobos and Deimos may have formed from debris left behind by a huge impact on Mars. The impact could have blasted material into space, which then came together to form these moons. Although scientists don’t have a definite answer yet, both theories are still being studied.

Could We Visit Mars' Moons?

You might be wondering if humans could ever visit Phobos or Deimos. Well, while they’re both much smaller than Earth’s Moon, they do present some unique challenges for space travel. For one, gravity on both moons is so weak that astronauts would have a hard time walking around. If you tried to jump on Phobos, you could leap really high—like, really high! In fact, you’d probably just float off the surface and have to be tethered down. However, Phobos and Deimos both make for excellent places to study Mars from a different perspective. Phobos, in particular, would be an ideal spot for a space station. Since it orbits Mars so closely, it could be a great platform for launching missions to the Martian surface. It could also serve as a pit stop for future Mars explorers. In addition, Phobos and Deimos could provide valuable resources for space missions. For example, they might have water ice beneath their surfaces, which could be used for drinking water, oxygen, or even rocket fuel. Scientists are still researching whether these moons contain resources that could make them useful for future Mars missions.

Why Are Mars’ Moons Important?

Studying Phobos and Deimos is important for several reasons. First, understanding their origin and composition can help scientists learn more about the early solar system. By studying these moons, we can get clues about how the planets and their moons formed billions of years ago. Second, Phobos and Deimos might play a role in future missions to Mars. As we plan to send astronauts to the Red Planet, having a base on one of these moons could help reduce the cost and complexity of reaching Mars.

So, there you have it—a quick trip to Mars and its two fascinating moons, Phobos and Deimos. These tiny, mysterious worlds have a lot to teach us about our solar system’s history and the future of space exploration. Whether it’s studying their strange surfaces, understanding their origins, or planning future missions, Mars’ moons will continue to be an important part of space science for years to come. Thanks for joining me on today’s adventure! I hope you enjoyed learning about the Martian moons, and who knows—maybe one day, we’ll all be taking a trip there ourselves. See you in the next  and final episode of this season!

S2 EP9: Super Puff Planets

Hello and welcome back to my podcast! In today’s episode, we’re going to talk about one of the most mysterious and fascinating types of exoplanets out there: super puff planets. These planets might sound like they come straight out of a science fiction story, but they’re very real, and they’re even more interesting than you might think. So, let’s dive into the fluffy world of super puff planets!

Before we get into the details, you need to know that super puff planets are gas giants that have a surprising and unusual property: they’re incredibly light for their size. Despite being as large as, or even bigger than Jupiter, they have very low densities. These planets are often described as being "fluffy," kind of like a cotton candy version of a planet, which is why they’re called super puff planets. Now, let’s break down what makes these planets so special and what we know about them.

What Are Super Puff Planets?

Super puff planets are gas giants with unusually low densities, meaning they have very little mass compared to their volume. Picture this: these planets are sometimes two to three times the size of Jupiter, but their mass is only about the same as Jupiter’s. The result? A planet that’s light and fluffy, almost like a balloon filled with gas. This makes them much less dense than any other known planet, even lighter than water! But here’s the catch: although they might look big and puffy, they are still massive compared to Earth. So how do they stay so fluffy? Well, most scientists believe it's because their atmospheres are packed with hydrogen, helium, and lighter gases like water vapor, which creates that puffed-up appearance.

Where Are They Found?

Super puff planets are found orbiting stars outside our solar system, also known as exoplanets. Many of these planets orbit very close to their stars. Since they are so close to their stars, they’re often heated up, causing their atmospheres to expand, making them appear even larger and puffier. They also tend to have short orbital periods, meaning they complete a full orbit in just a few days. This is due to their proximity to their stars. One example is the Kepler-51 system, discovered by NASA's Kepler Space Telescope. This system contains three super puff planets—Kepler-51b, Kepler-51c, and Kepler-51d. These planets are located about 2,600 light-years away from Earth, and they’re some of the least dense exoplanets discovered. Their low density is so extreme that they almost appear to be made of nothing but gas.

What Makes Them So Fluffy?

Now, the real question is: why are these planets so light and fluffy? Well, the low density of super puff planets means they have a huge amount of gas in their atmospheres compared to their mass. Think of it like a balloon filled with helium—it can float in the air because it’s light, but it’s still pretty large in size. Similarly, super puff planets are mostly made up of light gases like hydrogen and helium, which are the two most abundant elements in the universe. Some scientists believe that these planets might have formed with a large amount of gas surrounding a solid core, and over time, this gas might have expanded, causing the planet to puff up. Another theory is that these planets could have originally had much more gas, but over time, they lost some of it, leaving them with the fluffy, low-density atmosphere we see today.

Why Are Super Puff Planets Important?

Super puff planets are important for understanding how planets form and evolve. Their unique characteristics challenge our ideas of how planets should behave. They give us clues about how gas giants like Jupiter and Saturn might have formed, and they also help us learn more about how different types of atmospheres can develop over time. They’re kind of like the “wild cards” in the planetary science world, and studying them could unlock new information about the entire process of planetary evolution. For example, the supermassive atmospheres of super puff planets are key to studying planetary climates, especially because these planets are often so close to their stars. Scientists believe that these atmospheres can give us insights into how planetary atmospheres behave under extreme conditions, such as high temperatures and intense radiation from a star.

To wrap things up, super puff planets are one of the most intriguing discoveries in recent exoplanet research. They’re huge but surprisingly light, thanks to their massive, puffed-up atmospheres. These planets help scientists understand more about how planets form, how atmospheres behave, and what kinds of conditions might be needed for life to exist elsewhere in the universe. Super puff planets might seem like a bizarre, almost impossible concept, but they’re real, and they’re helping us understand the incredible diversity of worlds out there in space. Thanks for tuning in to today’s episode! I hope you now have a better understanding of these fluffy exoplanets and what makes them so unique. Who knows? Maybe one day, we’ll find life on one of them! See you in the next episode!

S2 EP8: A Guide to Galaxies

Hello as this season is nearing to its end, welcome back to another episode of this podcast. I’m your host Maanvinder and in today’s episode we’re diving into the incredible world of galaxies and will talk about what they are, the different types, and some of the most famous galaxies in the universe. Join me as we uncover the secrets of these cosmic beauties. So, let’s dive right in!

Before we get into the details, you should know that galaxies are enormous collections of stars, gas, dust, and dark matter, all held together by gravity. Think of a galaxy like a giant cosmic city, where stars are like houses and planets, moons, and other objects are like the people and cars inside. The largest galaxy known, IC 1101, is so big it can fit over 100 galaxies like our Milky Way inside it! This galaxy is so massive that it's about 6 million light-years across, and it’s located around 1.04 billion light-years away from Earth in the constellation of Virgo.

Now that we know what a galaxy is, let’s talk about the different types. In general, there are four main types of galaxies: spiral, elliptical, irregular, and lenticular galaxies.

Spiral Galaxies are the most well-known. Our very own Milky Way is a spiral galaxy! These galaxies are shaped like a flat disk with a central bulge, surrounded by spiral arms that wind outward. The arms are packed with stars, gas, and dust, while the central bulge contains older stars. Spiral galaxies often have a lot of star formation happening in their arms, and that’s why they appear so bright and colorful. If you look at the sky, you might be able to spot some of the most famous spiral galaxies, like the Andromeda Galaxy. Andromeda is the closest spiral galaxy to us, and it’s about 2.5 million light-years away. You can even see it with the naked eye on clear, dark nights, and in the future, our Milky Way and Andromeda will collide in about 4.5 billion years to form a single, much larger galaxy, often called Milkomeda.

Did you know that the Milky Way is thought to have formed around 13.6 billion years ago? That’s almost as old as the universe itself! And when we talk about spiral galaxies, the Triangulum Galaxy is another great example of a spiral galaxy. It’s smaller than the Milky Way and Andromeda but still contains around 40 billion stars.

Moving on to Elliptical Galaxies, these are shaped more like ovals or spheres and have no obvious arms. They tend to have a lot of old stars and very little gas and dust, which means there’s not much star formation going on in them. These galaxies are more common in galaxy clusters, where many galaxies are packed closely together. The M87 Galaxy is a famous elliptical galaxy. It’s huge, with billions of stars, and it’s home to a supermassive black hole at its center! This black hole was even captured in the first-ever photograph of a black hole by the Event Horizon Telescope in 2019. M87 is about 53 million light-years away from Earth in the Virgo Cluster, and its black hole has a mass about 6.5 billion times that of our Sun. Another fun fact: Elliptical galaxies are often much older than spiral galaxies. Most of them have stopped forming stars and are just slowly fading over billions of years.

Next, we have Irregular Galaxies. As the name suggests, these galaxies don’t have any defined shape like the spiral or elliptical galaxies. They can look messy or asymmetrical, often due to gravitational interactions with other galaxies. The Large Magellanic Cloud is a great example of an irregular galaxy. It’s one of our closest neighbors, about 160,000 light-years away, and it orbits our Milky Way galaxy. Irregular galaxies can be full of young stars, and they often have lots of gas and dust, meaning new stars are being born all the time. The Small Magellanic Cloud is another nearby irregular galaxy, and together, they are known as satellite galaxies of the Milky Way. Irregular galaxies are often rich in star-forming regions, making them some of the most fascinating galaxies to study. They often appear bright in infrared wavelengths, which is a result of young stars being born in large clouds of gas.

Finally, we have Lenticular Galaxies, which are a mix between spiral and elliptical galaxies. They have a disk-like structure, but unlike spiral galaxies, they don’t have any spiral arms. They’re kind of in between—old, but not quite as old and passive as elliptical galaxies. A good example of a lenticular galaxy is NGC 5866, located in the Virgo Cluster. These galaxies are relatively rare but can be found in the outskirts of galaxy clusters. Lenticular galaxies are unique because they might have once been spiral galaxies, but after losing their gas and dust, they stopped forming new stars, giving them an elliptical appearance. Some astronomers think that galactic collisions might be responsible for their transformation.

Now that you know the main types of galaxies, let’s quickly touch on how galaxies form. Galaxies start off as clouds of gas and dust in space. Over time, gravity pulls these clouds together to form clumps, which eventually become stars. As these stars group together, they form galaxies. Some galaxies collide and merge, while others stay isolated, constantly growing and evolving. It’s fascinating how galaxies are constantly changing and interacting with one another!

Galaxies can also be classified by their size. Some galaxies are dwarf galaxies, which are small but still contain millions of stars. Others are giant galaxies, which can contain hundreds of billions of stars, like our Milky Way. In fact, the Milky Way is part of a collection of galaxies known as the Local Group, which includes around 54 galaxies, including Andromeda, the Large and Small Magellanic Clouds, and other dwarf galaxies. No matter their size, all galaxies are incredible in their own way. A fascinating fact is that galaxies can also contain enormous structures called supermassive black holes at their centers. These black holes can be millions or even billions of times the mass of our Sun! They play a crucial role in galaxy formation and evolution. For example, the supermassive black hole in the center of the Milky Way is called Sagittarius A*, and it has a mass of about 4 million times that of our Sun.

So, the next time you look up at the night sky, think about how many galaxies could be out there. There are estimated to be over 100 billion galaxies in the observable universe, and each one is unique in its own way. To wrap things up, galaxies are the fundamental building blocks of the universe. They come in all shapes and sizes, from the iconic spiral galaxies to the mysterious irregular ones. Whether they’re forming new stars or holding ancient ones, galaxies tell us the incredible story of the universe’s evolution.

Thanks for tuning in to today’s episode! I hope this guide to galaxies helped you understand just how vast and diverse the universe is. See you in the next episode!

Spotify Wrapped :2024

Hello everyone,

I'm here to share about my Spotify Wrapped and to thanks everyone who listened my podcast so far. This year, i waited for it to drop unlike last year when i accidentally discovered that there's a wrapped for podcast too haha. I want to thank everyone of you, who shared your precious time with me because it is something that i like to do. I'm grateful for your support and cannot wait to share the new episodes with you, which will bring the season 2 an end. Anyways, my top listeners were in The Netherlands. Once again, thank you so much.

Here's a list of upcoming episodes in December 2024.

1. A Guide to Galaxies
2. Super Puff Planets
3. Trip to Martian Moons
4. Special EP: Stellar Outcasts Rogue Planets

S2 EP7: A Guide to Nebulae

Hello and welcome back to the part 2 of season 2 of this astronomy podcast. I’m your host Maanvinder and I will be taking you on another journey through cosmos and this time we will wander through the stellar nurseries where stars are born and that magical place is called nebulae. Now that you have a basic understanding of what are they but what they really are? In this episode, I will be talking about it, their types and will try to tell you about some beautiful nebulae that are helping astronomers understand the life cycle of a star from its birth to death. In other words Nebulae are a place where a star rises from the dead. Let’s get started

Nebulae are vast cloud of dust, hydrogen, helium and other ionized gases. The singular for it is Nebula. You will certainly be surprised finding out how they are formed because it is very interesting and you will definitely find it to your like. They can be formed by two ways either it is from supernova explosions or in a molecular cloud. So what happens in the earlier case is that when a star dies in a supernova explosion, it blasts out its outer layers, thus ejecting all the material that includes gases, dust and elements. In the process, the material ejected forms a shell like structure, moving outwards from the site of explosion and is called a Supernova Remnant. What triggers the star formation or I say makes them a nebula is the shock wave from the explosion which compress the nearby gas and dust, forming new star making regions within the remnant. Now let’s talk about the later, which is as part of star formation in molecular clouds. A molecular cloud is also a kind of a nebula but it mainly consists of molecular hydrogen, along with carbon monoxide and ammonia. They are denser and colder regions where star formation is actively happening comparing with nebula such as a supernova remnant.

New I want to shed the light for you on types of nebulae in the universe.

• Planetary Nebula- When a star like our sun dies, it doesn’t explode into a black hole or a neutron star. Instead, it shed its outer layers, which forms a beautiful cloud of glowing gas and dust due to the heat from the star’s core which ends up becoming a white jewel at the centre of the nebula. The best example of such nebula is the Ring Nebula. Located in the constellation Lyra about 2000 light years from the Earth, it also known as Messier 57. It was created when a Sun like star died during its red giant phase, by shedding its outer layers, leaving only a white bejeweled core at the centre and forming a planetary nebula surrounding it. Remember, i talked about the red giant, white dwarf and black dwarf phase of a main sequence star by taking Sun as an example. You might wanna check those three episodes out if you don’t get it.  At the centre of this nebula is a white dwarf and is 200 times more luminous than the Sun.
• Dark nebula- A dark nebula or an absorption nebula is a dense cloud of interstellar dust and gas that completely blocks out the visible light from objects behind it. I can name few Nebulae that fall under this category but I will like to tell you about one of my favorite. When I saw its picture, I was amazed and shocked that despite being a dark nebula, it is so beautiful. Coalsack nebula or Caldwell 99 is a dark nebula located in the constellation Crux, about 600 light years from the Earth. It is so dark that it blocks out light from any object behind it and is about 100 light years across. On a clear night, it can be seen as a dark patch obscuring a part of the Milky Way in the sky.
• Emission Nebula- It is formed due to the high energy UV radiation from the newly born stars which ionize the surrounding gas. This type of emission nebula is known as HII region. The other type of emission nebula is the planetary nebula in which a dying star has blown off its outer layers and the hot core ionizes the surrounding gas. So you can include the planetary nebula I discussed earlier as one of the type of emission nebula. One of the best examples of HII region are the Heart Nebula and Soul Nebula, together which are known as Heart and Soul nebula. Both of them are located about 6000 light years from the Earth in the Perseus arm of our galaxy, in constellation Cassiopeia. Another example of emission nebula is the famous Bubble Nebula or NGC 7635. It is located about 8000 light years in the constellation Cassiopeia. It is called Bubble nebula because of a bubble created by the stellar winds from a young star known as SAO 20575. The star is located at its centre and is about 45 times massive than our Sun. The bubble nebula is a massive cloud of gas and dust that is about 10 light years across and is also an HII region because the stellar winds from the central star have ionized the gas in the nebula. The star is about 4 million years old and comparing it with the Sun which is 4.6 billion years old, its lifetime is very short because the more massive a star the faster it runs out of its fuel. That’s why Red Dwarf stars have an age of trillions of years because they are small compared to other stars and burns their fuel slowly. This star is now burning helium after losing all its Hydrogen and in about 10 to 20 million, the star will end its life in a supernova explosion. Emission nebula often appears reddish or pinkish due to the light emitted by the ionized Hydrogen gas.
• Reflection Nebula- A nebula which glows because of the light from an embedded star which illuminates its dust. Unlike other types of nebula, the Reflection nebula does not emit light of its own. The best example to explain this kind of nebula is NGC 1999. It is located in the constellation Orion at around 1500 light years from the Earth. What illuminates this nebula is a variable star called V380. A variable star is a star whose brightness changes with time and are used my astronomers to measure distances across the Universe. The star is located at the centre of this nebula and the light from it illuminates this nebula. Another interesting thing about this nebula is that there is a one more nebula present inside the same nebula. Near the centre of NGC 1999, there is a dark cloud which resembles letter ‘T’ from the English alphabets. This type of dark nebula is called Bok Globule and that means star formation is taking place in that dark cloud near the centre of NGC 1999. They often appear blue because they reflect more blue light than any other light. Fascinating is it not? Universe does surprise you in a way you never know whether it’s possible or not.
• Supernova Remnant- A Supernova remnant is a type of nebula which is result of a supernova explosion in which a star dies. They distribute heavy elements throughout the universe, they borrowed to form them and now the ejected material will contribute to the formation of new stars. One of my favorite supernova remnant is Cassiopeia A, located about 11,000 light years in the constellation Cassiopeia. It is a remnant of a dead star, which astronomers believe was about five times the mass of Sun before its brutal death. One fun fact, in 2013, Phosphorus was detected in it, confirming that this element is born inside a supernova.

This is all from me for this episode but hey I’ll be back with a new guide to guide you through this vast cosmos. thank you!!

S2 EP6: Journey to Exoplanets Beyond Our Solar Shore

Welcome back friends for another episode of this astronomy podcast, I’m your host Maanvinder and today we’re going on a new journey to the world of exoplanets that are way more complex than the planets in our solar system. 

Our universe is huge and expanding, with billions of galaxies which have billions of stars and so billions of planets in the universe. The only one that we know where life exist is our own home planet Earth. Earlier as you might know peoples used to believe that planets only exist in our solar system until Copernicus changed when he came up with his theory that Earth revolves around the Sun. Updating this same theory in sixteenth century Italian Philosopher Giordano Bruno put forward his idea stating fixed stars are also like the Sun which have their own planets. In Astronomy, there is a different term for such planets which do not revolve around the Sun and are called exoplanets, meaning planets outside our solar system. Later in the 20th century, astronomers knew that exoplanets exist but they were yet to be discovered. The first confirmed exoplanet was discovered in 1992. By 1 July 2024, 6660 exoplanets were discovered through various methods that I will later talk about in this episode. But first let’s talk about their formation.

Formation & Types

Exoplanets are no different from planets in our solar system when it comes to their formation. However, they might change from one type to another because of some extreme conditions. Exoplanets just like planets are born in a nebula where star formation takes place. They are formed from the leftovers of a star which has died and when a new star is born. The remaining dust and gas that could not accumulate into a star because they lack mass enough to turn into a star, end up becoming a planet or in this case an exoplanet. According to NASA, exoplanets can be categorized into gas giant, Neptunian, Super Earth and Terrestrial. However, they can also be sub categorized based on several factors and can also be categorized into other types but those four are the main. They come in different sizes and shapes like WASP-12b (an rugby ball shaped exoplanet, which is being devoured by its host star), exoplanets that orbit two stars like Kepler-16b (the stars it orbits are smaller than our Sun; one is 60%the mass of Sun and other only 20%). They can boil you easily if melting a metal and glass is easy for them and the best example is 55 Cancri-e. There are planets which are wandering alone in the vastness of space. Now I will tell you about those main 4 categories, astronomers divides exoplanets in to have a better understanding of their formation.

1. Gas Giant- These are planets that are the size of our local neighbors Jupiter and Saturn. In fact, they are also gas giants and it is true that gas giants are also found outside our solar system. They are gaseous. Now if I talk about the sub category, then Hot Jupiter’s are the best example of it. They are basically the gas giants that are tidally locked with their stars, they are gaseous and are scorching heat. They formed in the cold regions but later migrated into the system and are now tidally locked; meaning one side is burning hell and other chilling cold. I can also categorize it into another type, say Ultra Hot Jupiter. They are even hotter than Hot Jupiter’s are and are mostly being devoured by their host stars. For better understanding of our universe, astronomers divide them into different categories to understand more about them. One example of Gas Giant will be Kepler-16b. If you were paying attention then you would know I talked about it earlier. It orbits two stars and was discovered in 2011 using NASA’s Kepler Spacecraft by transit method. It is cold, gaseous and composed of rocks, located about 200 light years from the Earth.
2. Super Earth- They are massive than Earth but smaller than Neptune. They can be terrestrial or full of water. They become huge because they quickly attain the thick atmosphere of hydrogen and helium. The two best examples of Super Earth that comes in my mind are 55 Cancri-e and Kepler-22b. The earlier is tidally locked with its host star and it is so hot that it rocks gets vaporized only to rain back as lava on the night side while later is a water planet whose more than 95% surface is believed to be Ocean as it is located in its star’s habitable zone where liquid water can exist.
3. Neptunian Planet- They are similar in size to Neptune and Uranus and have thick hydrogen and helium atmosphere with a rocky core. They can be sub categorized into Mini-Neptunes, which are smaller than Neptune but larger than Earth. They can become super-earth if they loses their atmosphere. It might not seem case for other planets but it surely fits in the case of Neptunes. In a rare discovery in 2022, astronomers at W.M Keck Observatory and those using NASA’s Hubble Space Telescope discovered two different mini-Neptunes that were losing their atmospheres turning into super earth. I also talked about this discovery last season. As I mentioned earlier about super earth and mini-Neptune, there is one thing in common that they both are bigger than Earth but smaller than Neptune. That brings us to the conclusion that Super Earth can also form when a mini-Neptune loses its atmosphere due to radiation from their host star. In fact the smaller planets in many star systems are believed to be Mini Neptunes who lost their atmospheres due to their host star’s intense radiation.
4. Terrestrial- rocky planets who failed to have thick atmospheres of hydrogen and helium or if they had a thick atmosphere but lost it because they lost their magnetic field just like Mars in our solar system and do not confuse it with the case of mini-Neptune losing atmosphere to become super earth because they are smaller than the Super Earth.

Other types of these exoplanets include:

1. Puffy Planets- gas giants with a puffy appearance just like a cotton candy. I will tell you about these in more details in one of upcoming episode.
2. Rogue Planets- planets that do not orbit a star and drift through the space.

Detection Methods

There are many methods to detect the presence of an exoplanet. One of the best methods is called Transit Method in which astronomers uses the dip in the curve of light coming from a star to detect an exoplanet. Say there is a planet far from Earth orbiting its host star and we don’t know that there is a planet orbiting around that star. In order to find out, we will point our probe in this case let’s take NASA’s TESS mission, towards a star and we wait for the dip in the light that comes from the star. When an exoplanet passes in front of a star, it causes the light coming from the star to dip, which is then used to determine the size of the planet. This method is called transit method and is one of the most effectively used methods to discover an exoplanet by the science community.

Another method is Pulsar Timing. Actually this was the method which made the first detection of an exoplanet surrounding a Pulsar. In this method if a planet is orbiting a pulsar, then it will cause anomalies in the timing of observed radio pulses that is the radio waves that it emits regularly as it rotates. The next popular method after transit method is Radial Velocity or Doppler method. In this method, astronomers use the light coming from the star. Still didn’t understand it. Okay so think about the space time curvature and if you did the experiment or at least saw a video of it that how when planets move around a star, they causes the star to wobble. When a planet orbits a star, their gravity causes their star to wobble and this affects the light coming from the star. If a star is moving towards then the light will be blue and if moving away, then red. That’s the basic science of Doppler shift here. By noticing the color change in the star’s light spectrum, astronomers can detect the wobble thus the presence of an exoplanet.

There’s one other method that I want to talk about and it is called Gravitational Microlensing. You may have heard about it when James Webb Space Telescope released its first images which surprised everyone and in one of the image, gravitational lensing can be seen very clearly. The image is called Webb’s First Deep Field and shows many objects like stars, galaxy clusters, and distorted background galaxies behind the galaxy star. According to Einstein’s theory of general relativity, massive objects can bend light and it is called Gravitational Lensing. When a planet passes in front of a distant star, the planet’s gravity bends and magnifies the light from the background star. This causes the background star to temporarily brighten, which can be detected by telescopes. By studying the pattern and amount of brightening, astronomers can determine the presence, mass and even distance of the exoplanet. There are so many methods to discover exoplanets but these were one of the mostly used and successful ones.

NEWS: James Webb Detected Hydrogen Sulfide on an Exoplanet

What never fails to amaze me is the fact that there must be an exoplanet where life exists. In fact, 1 in 5 Sun like star have one Earth sized planet in their habitable zone. Okay now I will tell you about the recent news about an exoplanet called HD 189733b, located in the constellation Vulpecula about 64.5 light years from our solar system. Recently NASA’s James Webb Space Telescope has detected the presence of Hydrogen Sulfide, a gas which smells like an rotten egg. The gas is also an indicator of presence of life. However, in case of this planet it is not true. Wanna know why? Then close your eyes and imagine what I’m about to tell you. You are standing on a planet which is so close to its star that it is tidally locked. The dayside of the planet always faces the star and night side always faces out into the space. The dayside is hot enough to evaporate glass and when this happens, the high speed winds carries away that molten to night side where it condenses and rain down as glass. Would you be able to survive on a planet where instead of your normal rain like on Earth, rains glass that can pierce through your body. I would not dare to spend a minute on that planet. However, it will be totally impossible to stand on it as the planet is a gas giant and to be clearer it is a Hot Jupiter. Remember I told you earlier about this type of exoplanets. So in conclusion the discovery of Hydrogen Sulfide means the planet will smell an rotten egg. This gas makes most of the planet’s atmosphere and don’t get attracted towards its beautiful blue color because that comes from clouds of glass. This has however is also found on Jupiter but it is one of the first detection on an exoplanet which is crucial in understanding the atmosphere, and life of a planet. HD 189733 b was discovered in 2005 using a method called radial velocity that I talked about earlier in the episode. It has an orbital period of 2.2 days because of it being so close to its star.

S2 EP5: What if Our Sun became a White Dwarf Star?

Hello and welcome back to another episode of this astronomy podcast and I’m your host and it’s time to finally embark on another adventure through our cosmos. Last season, I told you guys about some scenarios regarding the future of Sun like what if our Sun became a black hole, red giant star and black dwarf. One scenario out of these three will never come true and that is the one about black hole because Sun does not have mass enough to become a black hole instead it will become a black dwarf, which is the last evolutionary stage for a main sequence star. Before that happens, Sun will become a red giant star by growing its outer layers, engulfing planets and moons, etc. It is after this stage that is a new stage called White Dwarf and in this episode we will be discussing about it.

What is white dwarf? It’s not that hard to understand if you can understand the common science behind it. Our Sun is a main-sequence star which means it burns hydrogen to helium in a process called fusion, which is how it produces energy and light. When it runs out of fuel, it begins to fuse helium and other heavy elements produced inside it and will take the charge to prevent the star from collapsing under its own gravity. In this stage, the Sun’s outer layers begin to expand outwards. It is balanced by the star’s own gravity and the outward pressure from ongoing thermonuclear process. Roughly 5 billion years from now the Sun will enter the Red Giant phase. There comes a time it will run out of it as well and shed its outer layers because there will be no more thermonuclear reaction to prevent it from collapsing under its own gravity. When it will shed its outer layers, it will form a planetary nebula such as Carina Nebula. It is just like a supernova however there is one difference. In the blast of outer layers, Sun will throw all the elements and stuff into the outer space making a nebula, leaving a small sparkling jewel. It will continue to shine due to thermal heat from the process going inside it. However, it does not mean the Sun’s mass will also reduce to that of the Earth. According to Dr. John from NASA’s Goodard Space Station, the Sun will lose its 50% mass affecting the entire solar system. The sun will become dense and it will have an intense gravitational pull due to the electron degeneracy pressure. In this process the electron gets squeezed together, the more the electron gets squeezed, the denser the star gets. This pressure prevents white dwarfs from collapsing however; it does set a limit on it.

Earlier it was believed that all main-sequence stars turns into white dwarf and does not undergo supernova. This was changed when an Indian-American astrophysicist Subrahmanyan Chandrasekhar discovered a limit called Chandrasekhar Limit. According to this limit, a white dwarf can also become a neutron star by undergoing a supernova called Type Ia Supernova if the mass of white dwarf is about 1.4 times that of the Sun. Another way to go supernova is if it gains mass and this is possible if it comes in a contact with a red giant star, which usually happens in a binary star system where one is in red giant phase and the other is in the white dwarf. As red giant has lower control on its outer layers due to it being only supported by the thermonuclear reactions pressure, the white dwarf will begin to collect or in other words steal the material from its companion red giant until it reaches a point called Chandrasekhar Limit where it will undergo a supernova explosion, resulting in a neutron star. This possibly leaves a white dwarf and a neutron star because the continues flow of material from red giant to white dwarf causes the process of the other red giant turning into white dwarf gets increases and it loses its outer layers before it has a chance to burst the layers on its own naturally.So is it possible in case of Sun? if you were paying attention you would know that our Sun will never undergo this process of becoming a neutron star let alone a black hole. First if its mass was 0.4 times more than it has, it would have certainly undergone a supernova. Another reason is that there is no close star for our sun to collect material to reach that limit. So yeah, its safe to say that deadly fate is not in our sun’s evolution stage.

With this thing I would like to draw your attention towards one more thing, when our Sun will be in its red giant phase, it will engulf everything till Jupiter according to latest models. That means our planet will be gone, the mars will be gone, the asteroid belt will be gone. The question that arises here is will life exist then? Then answer might be yes because when the Sun will be near Jupiter, its habitable zone will gets shifted beyond Jupiter’s orbit, somewhere around Pluto, Neptune and Kuiper Belt, possibly giving life a second chance to thrive. However, I’m not sure of the fate after that because when Sun will blow its outer layers, which mean it will blow up everything in its wake. Astronomers used to think that there will be no planets orbiting it until they discovered one white dwarf with planets. Now we know planets can still orbit an white dwarf. For example, WD 1586 b is a Jupiter sized exoplanet orbits the white dwarf every 34 hours. It was discovered by NASA’s Spitzer Space Telescope while analyzing data from NASA’s TESS mission in which transit method is used to discover new planets. I will explain about this in the next episode. Another such example is of SDSS J1228 which is just the metal core of a dead planet, revolving around a white dwarf. White dwarfs also have their own habitable zone. That means when our Sun becomes a white dwarf, the habitable zone will once again gets shifted back from Pluto to a new place, where if a planet survived the outburst of sun’s layers, the liquid water on it might exist if it is revolving inside this zone. That is for the future to decide. White dwarfs take billions of years to cool down and when they do, the last stage will be turning into a black dwarf if it is a white dwarf with mass no more than 1.4 or more than that. White dwarf has thin atmosphere of hydrogen and beneath it lies a thick surface of helium around 30 miles thick whose interior is made of super heated carbon and oxygen because it is these elements whose electrons gets squeezed to make a white dwarf denser. The surface temperature of a white dwarf can be as hot as half million degrees but over the course of billions of year, it will cool down to a point when it will be remain left as a cold dark ball lurking in the space and planets or any celestial body will still be orbiting around it except one thing that will change. It will be pure darkness and darkness for anyone to stand there, thus bringing an entire star system to its silent and dark death.

That is from me now until we meet again for the next episode. Stay tuned!!

S2 EP4: Neptune's Moon Triton

Welcome back everyone, to another exciting episode of this astronomy podcast, where we journey through the wonders of the universe. I'm your host, Maanvinder, and today, we're diving deep into icy depths of a fascinating celestial body or i say Neptune’s moon Triton.

Triton is the seventh largest natural satellite in the solar system and also the biggest moon of Neptune out of its 16 moons. Another fascinating thing about this moon is that it was discovered just 17 days after Neptune by a British astronomer William Lassell on October 10, 1846. Apart from galaxies and nebulas, natural satellites of planets in our solar system never fail to amaze me. I remember when I would write down the names of all moons in my science note book and dedicate a separate page for the particular moon just to add interesting facts about them and some of my favorite one include two moons of Mars, Saturn’s Moon Titan, Jupiter’s moon Io and many other small moons of Saturn. I’m sure you all are aware of that feeling where you just wanna know so much about this cosmos.

Do you know that Triton is believed to be an Kuiper belt object? If you don’t know then let me tell you why scientists thinks it’s one of those Kuiper belt objects. It is the only moon in the solar system that moves in an retrograde orbit, which means rotating opposite to the Planet’s rotation. According to current astronomical models, any moon that formed surrounding a planet will rotate in the same direction as that of the planet but in case of this moon, it’s the opposite case. That’s why scientists believe it is an Kuiper belt object that was captured by Neptune in its orbit. Another interesting thing related to its rotation is that it is tidally locked with Neptune due to its closer distance to the planet which means only one side of Triton always faces the planet and the other side remains hidden from point of view of someone who is standing on Neptune. Well you basically cannot stand on the planet but imagine that for your understanding. Okay let’s use the example of our moon. We never see the other side, the dark side of moon because it is tidally locked with the Earth.

Neptune is literally the death of this beautiful moon. You know why? Like I said earlier, Triton is tidally locked to its planet but the only difference between Triton and Earth’s moon is that Triton is way closer to its planet than our Moon is to the Earth. That is why, due to tidal interactions from Neptune, it is getting pulled into the Neptune’s orbit and once it crosses the Roche Limit of Neptune, Triton will begin to fall apart into pieces, colliding with the planet and making a new set of rings around the planet just like Saturn and this time it will be denser than the current ones. If you still don’t get it, remember the episode of previous season in which I talked about an exoplanet called WASP-12b which is being devoured by its host star as it is tidally locked and the tidal interactions from its host star continue to eat this planet. Okay so one thing I wanna make clear here is that this is not the fate of our Moon, even though it is also tidally locked. Our moon is drifting away from Earth. Scientific predictions suggests that in about 3.6 billion years, Triton will enter the Neptune’s Roche limit, thus beginning leading this moon towards its death. Another interesting thing I wanna tell you about this moon is it is one of the few moons with atmosphere in our solar system like Saturn’s moon Titan. It has a thin atmosphere composed primarily of nitrogen, smaller amounts of carbon monoxide and Methane. Carbon Monoxide was first detected back in 2010 through ground based telescopes and it was found that it is more abundant than Methane. NASA has proposed a future mission to study Triton and it is called Trident which will be launched in October 2025, arriving on the moon in 2038 to study it in more details. The last time a probe or mission to study was when Voyager 2 flew past it in August 1989 during its closest approach to Neptune, when it discovered that Nitrogen and Methane presence, confirming previous theories regarding their presence by astronomers. The atmosphere of Triton is sustained mainly due to the cryovolcanic activity on the surface of the moon, which means the eruption of gases, liquids and ice from the surface. Cryovolcanoes on the surface of Triton erupt nitrogen and other volatile liquids. This suggests the presence of a reservoir of liquid water and volatile compounds.

A day on Triton lasts for about 5.8 Earth days and due to it being tidally locked with the Neptune, there is no doubt in accepting the temperature difference between the two different sides of the moon. During its flyby Voyager 2 found the surface temperature to be -235 degree Celsius, however the temperature difference between two sides would be completely different if we take one side of the Triton that is always in dark. Even though Triton is one of the coldest objects in the solar system, it does have a heating system. Remember the tidal interactions I told you earlier about, it is because of these tidal interactions that the cryovolcanic activity is possible on this Moon, keeping liquid water beneath its frozen nitrogen surface. I asked planetary scientist & astrophysicist Sean Raymond about this to which he replied, “Tidal heating would be distributed evenly across Triton but solar heating would vary from one hemisphere to the next over Titan’s 5.9 days orbital period around Neptune. I Titan is very far away from the Sun so it’s not very warm anyways”. I recommend you guys to check out his blog planetplanet.net.

Triton is one of the few geologically active moons in our solar system thanks to its cryovolcanic activities due to the tidal interactions from Neptune. Also, the moon is larger than the dwarf planet Pluto at around 2710 km in diameter. It is also the largest retrograde moon in Solar System and comprises about 99.5% of total mass that orbit Neptune while the remaining moons and rings making only 0.5% of the total mass. I believe you have been surprised to know so many facts about the moon so far then let me tell you one more. Titan appears to be reddish in color. Why? Well it is because of the methane ice. That's all for today's journey through Triton. Join me next time as we embark on another cosmic adventure. Until then, keep gazing up at the stars!