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 5. For the episode playlist, click on the annotation here or have a look in the description.
Number 28 Doradus 30 or the Tarantula Nebula.
This image is a small section of what is known as the Tarantula Nebula.
The Tarantula Nebula is a huge, impressive nebula found in the Large Magellanic Cloud,
a satellite galaxy to our own.
Some may argue it isn’t as pretty as some of the other nebula we’ve looked at so far,
but I must say it does look good in its own right.
But if it isn’t its looks that make this nebula stand out, what is it that sets it
apart from anything we’ve looked at so far?
We’ll come back to that.
Let’s first of all give you some context.
So, where is it?
This is the Large Magellanic Cloud, the largest of the Milky Way’s satellite galaxies.
As you can see, it has a lot of nebulae.
The one we are focusing on, the Tarantula Nebula is the brightest and biggest nebula
in this galaxy.
And it really is bright.
I selected this image because it still shows some of its details; most other images show
it as this bright overexposed spot.
It’s so bright, that if this nebula was as close to us as the Orion Nebula in our
own Milky Way, it could cast shadows at night.
Let’s zoom in to find out why.
The Tarantula Nebula is currently undergoing extreme star formation, in fact it’s the
most active star forming region in the whole local cluster of galaxies.
To its centre is a region of stars known as NGC 2070, the central concentration of stars
known as R136.
It’s this star cluster that produces most of the energy to make this nebula visible.
It’s a really big cluster, with an estimated 450,000 solar masses contained within it.
Now, if you’ve ever wondered what the most massive and brightest known star was, look
no further.
One of the stars in this cluster, known as R136a1 is the most massive and brightest star
on record, with some pretty incredible statistics.
It is a Wolf-Rayet star, 315 times the mass of the sun, and 8.7 million times more luminous.
It is also one of the hottest stars, at 53,000c.
While it is the most massive star, it is not the biggest, although its size still dwarfs
the Sun.
As always with these massive stars; it will only be short lived, and it will almost certainly
become a black hole at the end of its life.
In the meantime, it is shedding its mass through its solar wind at a very fast rate.
Since its birth, it’s thought it has already lost 50 solar masses to space.
Overall, the R136 star cluster is thought to only be about 2 million years old.
It is currently merging with another close-by cluster, the two clusters together making
up NGC 2070.
You may not think there are enough stars in the image to make up 450,000 solar masses,
but these blue stars you are seeing in this image are only the very brightest O type stars
in the cluster.
Interestingly, there is a star that belongs to this cluster which isn’t found anywhere
in the area.
If we zoom out a bit, you’ll find this star over here.
It’s called 30 Dor #016 and the young star, only one million to two million years old,
may have travelled about 375 light-years from its suspected home in star cluster R136, and
it is still travelling about 400,000 kph.
But how did it get all the way out here?
The theory is that it could be that it was part of a binary star system, when another,
even more massive star entered the system and kicked out the now homeless star.
These other stars would have had to have been extremely massive as 30 Dor #016 is no minnow,
at a suspected 90 solar masses.
It now is an explorer, destined to travel to the far reaches of the LMC.
There is another, old star cluster found in the Tarantula Nebula, called Hodge 301.
It is roughly 20 million years old, with some stars ten times as old as those found in R136.
Within this star cluster, there are thought to have been at least 40 stars that have gone
supernova, whereas in R136, there have been none.
This is because of the age of Hodge 301; some of the shortest lived stars have already gone
through their entire life cycle.
More stars in this cluster are on the verge of exploding in a supernova too; so watch
this space.
The original image we looked at is further away still from the centre of the Tarantula
Nebula, although still part of it, in an area called NGC 2060, found over here.
It’s a star cluster too, although the stars here are much more loosely dispersed than
in R136 and Hodge 301.
In fact they are no longer gravitationally bound to each other and in a few million years
the stellar group will disperse completely.
It’s currently about 10 million years old, and there are some very interesting things
found in this area.
The first I’ll mention is that the whole of NGC 2060 is also a supernova remnant, about
165 light years across.
It is estimated that the supernova occurred about 4-5000 years ago, and consistent with
this theory, a pulsar neutron star is found in this area here around the same age as the
supernova.
It’s not really visible in visible light as it emits x-rays, which means you need the
x-ray telescope Chandra to see it, and it’s right in the centre of this bubble.
The bubble itself is the supernova remnant.
The pulsar rotates exceptionally fast, once every 16ms.
Interestingly, it’s not the fastest rotating star in this region, that accolade belongs
to this runaway blue supergiant, VFTS 102.
It is actually the fastest rotating star that we know of, rotating a speedy 2,000,000 kph.
This is 100 times faster than the rotation speed of our Sun.
It spins so fast the star is flattened, with an equatorial disk extending out due to centrifugal
forces.
It is suspected that this runaway star actually was part of the same system as the pulsar
and would have had a hand in the supernova explosion.
Before the supernova, they would have been two blue stars orbiting one another.
One would evolve into a red supergiant, and would have started feeding its mass into the
other star, speeding the rotation of the other.
Once the red supergiant explodes in a supernova, it ejects the other star at a tremendous speed
into space.
VFTS 102 fits this model as it is spinning rapidly while also hurtling through space
in relation to its stellar neighbourhood.
Zooming out further again, we are getting to the edge of the Tarantula Nebula.
At its longest points, the Tarantula Nebula is an incredible 1000 light years across.
I already mention this nebula is the most active star forming nebula - also known as
a HII region - in our local cluster of galaxies, but it is also the biggest.
If it was as close to us as the Orion nebula, it would be twice as big in the sky as the
Big Dipper, and because it’s so bright it would even be visible during the day.
At the far edge of this nebula is perhaps the most remarkable visual spectacle in the
whole Tarantula Nebula.
It is called SN1987A, and it is a supernova remnant.
It is a lot younger than any of the other supernova we’ve looked at so far; in fact
it is less than 30 years old.
The light from the supernova hit Earth in 1987 and was visible to the naked eye.
It was the first supernova observed since the 1600s, and the only supernova observed
using modern day telescopes.
When it exploded, it was a blue supergiant which means it was only about 1/10th of the
brightness of a red supergiant supernova.
Having had a chance to look at it, I bet you are now wondering what these rings could be.
Well they are mass thrown off by the star through stellar winds, coughing and spluttering
its innards out thousands of years before the supernova.
The initial flash from the explosion lit up the rings at first, but then when the supernova’s
shockwave hit them years later, they lit up again due to interactions with the rings and
the debris from the shockwave.
SN 1987A is now a true ‘supernova remnant’ in the vein of the Cassiopeia A, illuminated
not by the explosion of the star but by collisional processes between the debris of the supernova
and material beyond it.
This artist's illustration of Supernova 1987A is based on real data and reveals the cold,
inner regions of the exploded star's remnants (in red) where tremendous amounts of dust
were detected and imaged by the ALMA telescope.
It’s in this dust that the leftover pulsar could be hiding, because nothing has been
detected where the pulsar should be.
Another option is that it turned into a black hole!
Well that’s it for this week.
I hope you’ve enjoying learning all the interesting facts about the Tarantula Nebula.
I was going to do more than one subject in this episode but I just kept finding more
and more that I could talk about and I didn’t want to leave anything out.
If you enjoyed, it would mean a lot to me if you like and share the video.
Also I would like to give a big shout out to my first patreons Garthvater and Servando!
Thank you so much for your support, it’s hugely appreciated.
And to all my subscribers, thank you too!
And I’ll see you next time.