Hello and welcome back to my podcast. In
this episode, I will tell you guys about the star clusters, their types and
will also tell you about some of the very famous clusters like the Pleiades
Star. So let’s get into it!
Before we start, you guys need to know the
process behind the formation of a star. Stars are formed in large cloud of gas
and dust called nebula. Gravity begins to form the clumps of the gas and dust,
pulling more and more material into it, until it gets massive enough to
collapse under their own gravity. Until then, they are proto-stars, and when
these collapses they forms a star which is producing light. The leftover from
the star formation becomes planets, asteroids, and comets just like what
happened when our solar system was born. Stars are born in groups in a nebula
and when all the proto stars collapses under their own gravity, they becomes
stars and become what is called by astronomers as “star clusters”.
Star Clusters are groups of stars, hold
together by their mutual gravity. There are hundreds of them in our galaxy.
When talking about their types, then the answer is three: Open, Globular &
Embedded Clusters.
Open Clusters are a group of a few to a few
thousand stars born from the same cloud of gas and dust. If you are a
astrophotographer, then they are a perfect target for you because you can see
every star within the cluster using your telescope and sometimes with unaided
eyes. The Pleiades is the best example of open star cluster. You can see them
looking like a small Ursa Major constellation in the sky. To be honest, at
first I literally had no idea what I was looking at until I realized that I was
looking at the Pleiades all the time.
Pleiades are also known as the “Seven Sisters” cluster because there are
7 stars in it. In fact, there are more than 7, around 1000 stars but these
seven are the brightest ones, which appear from the Earth.
Another interesting thing about these open
star clusters is that they will not be forever like this. With the passage of
time, they will get disperse in the space because of their gravitational
disruptions in the space. Our Sun- the star which is source of light and energy
was once a part of such cluster and was also separated from the other stars
because of such gravitational disruptions. Open clusters are young group of
stars and are found in the spiral arms of the spiral galaxies. There are more
than 1000 of them in the Milky Way galaxy.
Moving into the Globular Clusters, they are
more massive, older than the Open clusters. Globular clusters are a group of
thousands to millions of stars, gravitationally bounded by each other. Unlike,
the open star clusters they are not easy to photograph because the stars are so
densely packed that you cannot distinguish them from each other, not even using
the ground based telescopes. Powerful telescopes like Hubble and James Webb are
good at doing this job though. According to NASA, they are home to some of the oldest stars in the Universe. As
old stars tend to appear red, these globular clusters also appear to glow red.
There are around 150 globular clusters in the Milky Way while the neighbor
Andromeda has over 400 of these. They are much good at holding them together.
They don’t decay with the time and so their strong gravitational attraction
keeps all the stars together. The best example of a globular cluster is Messier
13 or M13- located in the constellation Hercules, about 25,000 light years from
the Earth. Sometimes, this cluster is also known as the Great Globular Cluster
or NGC 6205. The stars in the cluster are about 12 to 13 billion years old,
almost as the same ages as our universe.
