Hi I’m Alex McColgan, and you’re watching Astrum.
Hubble has released a zip file on their website containing the top 100 pictures Hubble has
ever taken.
What I will do over the course of this series is go through these pictures one by one and
explain what it is you’re looking at.
And believe me; some of these pictures REQUIRE an explanation!
Episode 4. For the episode playlist, click on the annotation here, or have a look in the description.
22. NGC 4449 At first glance, I thought this was one of
the Magellanic Clouds, but it’s actually a small, irregular galaxy in a galaxy group
called Canes Venatici, about 12 million light years away.
This means, like us, it is part of the Virgo Supercluster, otherwise known as the local
supercluster of galaxies.
It is similar to the Large Magellanic Cloud in that it has a general bar shape, but the
big difference is this is considered a starburst galaxy.
It is very active in producing new stars, as can be seen here in these pinkish regions.
Pink or red areas in a galaxy are generally a tell-tale sign of star formation, as stars
surrounded by hydrogen gas ionise the hydrogen to glow red with their intense radiation.
Another tell-tale sign of high rates of star formation is the many blue stars you see in
this picture.
Blue stars are extremely hot, young and often massive stars that will burn out quickly because
they get through their fuel so fast.
Because these stars can only live to a certain age, they must have only been produced within the last few million years.
And as we can see, there are many blue star clusters in this galaxy.
This starburst is thought to be because of galaxies interacting with NGC 4449.
If we zoom out a bit, we see this trail of red stars, perhaps the remains of a spheroid
galaxy passing through NGC 4449, stretched by a tidal effect.
Looking at the galaxy centre, we see a bright white group of stars with some dark clouds
of dust around it.
Stars can form within clouds like these.
This galaxy is 19,000 light years across.
23. HD 97950 This spectacular superstar cluster is found
within the NGC 3603 HII nebula.
It is incredibly pretty, and has been studied a lot because it is found in the Carina spiral
arm of the Milky Way; roughly 20,000 light years away.
NGC 3603 is interesting to astronomers because it is the most massive visible cloud of glowing
gas and plasma - known as an H II region - in the Milky Way, and the superstar cluster has
the densest concentration of stars known in our galaxy.
The UV radiation and stellar winds have carved into the surrounding dust, producing these
beautiful shapes, and also giving us an unobscured view of the super star cluster.
Stars of note in this cluster are Sher 25, a star 60 times the mass of our Sun and reaching
the end of its life.
It is expected to go supernova anytime now, as it’s already thrown off matter in a similar
manner to what has been seen in other supernovae.
We also have the three main stars in the heart of the cluster, barely distinguishable in
the centre of the image here.
All three are Wolf-Rayet stars each about 100 times the mass of the Sun and millions
of times more luminous.
Two of them are incredibly close together as part of a binary star system, taking only
3.5 days to orbit one another.
This means they are practically touching, no doubt exchanging a lot of mass as well
as having an incredible tidal influence on each other.
Zooming out a bit, we see that visually NGC 3603 is right next to another nebula, NGC
3576, but in actual fact this other nebula is about half the distance to us.
They just so happen to be visually aligned.
24. Messier 74 On first glance at this image, I thought it
was another viewpoint on the famous galaxy we’ve already looked at, the Whirlpool Galaxy.
And putting them side by side, these galaxies do look remarkably similar!
They are both grand design spiral galaxies for a start, and have similar dust patterns
weaving through their arms.
But putting them side by side, you can tell there are slight variations with these two galaxies.
M74’s arms are lined with hot blue stars, with pink and red star forming regions dotted
all over.
You may think the arms of galaxies like this are static arms rotating around the nucleus
of the galaxy, but actually they are the visual effect of density waves.
As gas and dust orbits the galaxy, they pass through the galaxy’s density waves, compressing
the gas and dust which causes stars to form.
Existing orbiting stars also clump up in these density waves.
A lot of these stars will be blue and only short lived, perhaps completing their life
cycle in only a few million years.
M74 is about 32 million light years away and has a low surface brightness, making it one
of the most difficult Messier objects for an amateur astronomer to observe and giving
it the nickname: The Phantom Galaxy.
It is probably just a little smaller than our own Milky Way galaxy, containing about
100 billion stars and is 95,000 ly across.
It sits in the M74 Group, a small, little, remote group of galaxies.
25. Arp 148 So, first impressions, what do you think this
could be?
Pause the video and take a guess in the comments if you want.
Well, this bizarre shape, found a staggering 500 million light years away from us, is a
galaxy and is nicknamed Mayall’s Object.
It is in fact most likely to be two merging galaxies, the initial collision theorised
to have created a shockwave which drew matter into the centre before it propagated out into
the ring you see.
The tail is a streamer of stars from one of the galaxies, further suggesting this is an
ongoing collision.
Interestingly and on a little side note, the Arp catalogue is the Atlas of Peculiar Galaxies.
26. Abell 2218 Now if you thought the last image was an impressive
distance away, have a look at this one.
Abell 2218 is an impressive cluster of galaxies 2.1 billion light years away.
Clusters like these are particularly scientifically interesting because these galaxies immense
gravity bends the light around them acting as a magnifying glass to see galaxies even
further behind them.
These old long arcs are actually distant galaxy’s light, stretched and warped by the gravity
of the nearer galaxy cluster.
In this image is perhaps the most distant galaxy known at an estimated 13 billion light
years away.
In this image it is barely visible, but an enhanced image we can make out its stretched
appearance.
Because of this lensing effect, the galaxy actually appears twice in the image, here
as well as here.
We see it from Earth as if it was only 750 million years after the Big Bang, meaning
we are looking back in time to the early universe.
There are around 10,000 galaxies in this image.
27. Abell 1703 This is another galaxy cluster, doing the
same lensing effect we looked at in the previous image.
I want to just explain in a little more detail how this works.
Firstly, we look at a distant, massive object.
Gravity is theorised to be able to warp spacetime, perhaps a topic I will come to in another
video.
Often elliptical galaxies are the biggest galaxies in existence, and the more massive
the galaxy, the bigger the warping effect on spacetime.
You can see this with the lensing effect around the big elliptical galaxy in the middle of
this image.
As spacetime is warped, light is bent around the galaxy, and if it aligned right it gives
us a magnified view of the other side of the galaxy.
A natural, handy magnifying glass floating in space.
And about this galaxy cluster, Abell 1703 is around 3 billion light years away.
Sadly we’ve come to the end of another episode, but hopefully you enjoyed it and learnt more
about some of the mysteries of our universe!
If you want more, don’t forget to subscribe as I’ll be making more in this series as
well as other space videos in the future!
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Thanks so much for watching, and see you next time.