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To walk outside at night and peer into the glittering darkness of space
is a special experience - but one that doesn’t capture the true majesty of space,
and everything it contains. Light pollution, atmospheric distortion, and our limited eyesight
prevent us from truly exploring the universe and discovering its secrets. Thankfully, the Hubble
space telescope, from its position orbiting around 550km above the earth, allows us to
overcome these limitations and see deep into space - changing our understanding of astrophysics,
and shaping our knowledge of the universe while also dazzling us with remarkable images.
I’m Alex McColgan and you’re watching Astrum. Today, we’re going to look through the Hubble
telescope, take a journey billions of light-years into space, and explore and give context to the
furthest reaches of our galaxy, and far, far beyond, all the way to the most distant object
ever seen. What will we see along the way? And what will Hubble surprise us with in this episode?
Our first encounter is 3800 lightyears away, where we see vast blue wings stretching out into space.
But what is it? This is NGC 6302, otherwise known as the Butterfly Nebula. Lying within
our Milky Way galaxy, the Butterfly Nebula’s spectacular array of blue and turquoise colours
is actually the glowing gas that was once a star’s outer layer. The wing-like shape showcases the
expansive journey that this gas has taken over the last 2200 years - covering a distance of over two
light-years. Recent observations of the Butterfly Nebula have detected unprecedented
levels of intricacy in the gas jets and bubbles erupting from the star at the nebula’s centre,
all of which create rapid changes in the wing-shape you’re seeing now.
Travelling beyond, to 8000 light-years away, we find the star cluster Pismis 24.
This cluster contains a combination of remarkable phenomena. First, your eye will be drawn to the
core of a large emission nebula, rising up, and glowing. Second, you will notice the blue stars
lingering in and around the nebula. These blue stars owe their blue colour to their intensely
hot temperature, far hotter than our own Sun. This is due to their mass, which determines
the temperature of a star, with blue stars having at least 3 times the mass of our own.
These blue stars help to give Pismis 24 its signature colour and texture.
Their extreme ultraviolet radiation causes the gas surrounding the cluster to heat and bubble
around the star in remarkable clouds, which makes probing the region extremely difficult.
For a while, Pismis 24-1, a star in the Pismis cluster,
was thought to be the most massive star ever recorded - at almost 300 solar masses. However,
it is now thought to be at least three stars, each weighing in at almost 100 solar masses.
Much smaller than originally thought, but still some of the largest stars ever recorded.
Pismis 24 is part of the diffuse nebula NGC 6357 - a “cosmic nursery”, the nebula is home to many
proto-stars shrouded by dark gases. Proto-stars are the earliest stage of stellar evolution, where
stars gather mass from their parent molecular cloud. Alongside these proto-stars are many
young stars encased in expanding cocoons of gas - making the nebula feel like a living organism.
Now let’s go even further… Journeying 60,000 light-years away, we come across Palomar 12,
with its globular cluster of stars hanging in deep space. Lingering on the outskirts of the Milky
Way’s halo, these stars are around 30% younger than the other globular clusters in the Milky
Way galaxy. What is the secret to their young age? They were abducted! Palomar 12 isn’t actually from
the Milky Way galaxy, but from the Sagittarius Dwarf Elliptical galaxy. Around 1.7 billion years
ago, the Palomar 12 cluster was torn from its home galaxy by tidal interactions with the Milky Way.
In fact, Palomar 12’s home galaxy is currently being ripped apart by our galaxy. These tidal
forces are limited to the immediate surroundings of their respective galaxy, but when they collide
or pass nearby one another, the results are striking, creating strange distorted shapes,
or unique phenomena as demonstrated by Palomar 12, where clusters born in one galaxy end up
living in another. And our journey doesn’t end here. Hubble allows us to see much further. Let’s
continue our voyage outward, hopping more quickly between locations, starting with 30
million lightyears distance, where Hubble allows us to see a familiar view, from a new angle.
This is the Sombrero Galaxy. As we see it from the side, it shows us the flat,
“disk-like” shape of most galaxies - a view we don’t typically see. You might be wondering
why this flat shape is the norm - after all, planets, moons, and meteors tend to be spherical.
Shouldn’t all galaxies be the same? The reason for the more common flat shape found in galaxies
is that, as mentioned before, the universe is in constant motion, and gravitational forces caused
by the black holes at the centre of galaxies cause them to rotate, with the conservation of angular
momentum leading to an outward “disk-like” shape. The Sombrero Galaxy is notable for the blinding
white core at its centre, and the distinct lanes of cosmic dust, spiralling outwards,
the most pronounced of which linger at the rim, giving the galaxy its distinctive Sombrero Shape.
Continuing further - at 65 million light-years, we see the broad, elliptical galaxy NGC 1052-DF2.
Do you notice anything distinct? You might have spotted its particular,
diffuse texture - so diffuse in fact, that distant galaxies can be seen behind it.
This gives the galaxy a supernatural, almost ghostly appearance. But most strange of all
is the fact that this galaxy is possibly missing all of its dark matter. This was the first galaxy
of its kind to display such an absence. As for why - we’re not truly sure. Let’s go even further,
this time, just over 300 million light-years from Earth. This is the coma cluster,
a large gathering of more than 1000 galaxies, all linked together by gravity - a cluster
that also happens to be one of the first places where we discovered indications of dark matter.
In this image that you’re looking at, you can see thousands of intracluster globular clusters.
These are spherical groups of stars that are bound not to a galaxy, but to the coma cluster itself.
While that might seem far… we can still travel further. Over 9 billion years away,
is MACS J1149 aka Icarus. Once the furthest star we knew of in the universe.
In fact, light from Icarus takes so long to reach us, that it appears to us the same way it did when
the universe was 30% its current age. To give a sense of just how far away Icarus is, at the time
of its capture in the image, Icarus was at least 100 times further away from the nearest star. Yet
we can travel even further, to distances that seem beyond comprehension. Nicknamed Earendel,
WHL0137-LS is a star in the Cesus constellation, whose light took over 12.9 billion years to reach
us. However, due to the expansion of the universe, the distance between Earendel and ourselves is now
even greater - 28 billion light-years. We are just seeing it where it was almost 13 billion years
ago. Earendel is suspected to be 50 to 100 times the size of our sun, and due to its enormous mass,
is expected to explode as a supernova in a few million years from our perspective.
Nicknamed Earendel, after the old English name for ‘morning star’ or ‘rising light’,
the name is actually a reference to J.R.R. Tolkein’s character
Eärendil - who travelled through the sky carrying a jewel as bright as a star.
Outside of its interesting name and impressive size, Earendel also has an effective surface
temperature of at least 20,000k. Almost 4 times hotter than our sun. There is also a
small possibility that it is a population III star, which means it would contain almost no
other elements besides hydrogen and helium, and it would be far brighter than your average star.
We were able to see this star through an effect called gravitational lensing, where a cluster
of galaxies warped light from the star around them in just the right alignment so that they
act like a huge lens, allowing Hubble to see much further than it otherwise would have been able to.
Things are so unbelievably far away now, that even Hubble is reaching its limits.
But is there anything further we can see on our journey to the far reaches of space? Yes,
there is one more object Hubble can show us: the high-redshift galaxy known as HD1.
The earliest and most distant known object in the observable universe.
Although little more to us than a faint red dot, HD1 is actually 13.5 billion light-years away,
or at least it was, when the light was emitted. It is estimated to now be at a
distance of 33.4 billion light-years away, with the expansion of the universe taken into account.
While it lies at the very reaches of our perception - it has some telling details. Its
extremely luminous ultraviolet emissions suggest it could be a starburst galaxy, producing stars
at an unparalleled rate. It could also be home to the enormous Population III stars described
moments ago that are far more luminous than the stars we are familiar with. However, these and
any other theories are speculative due to the minimal amount of photons we are working with.
All we do know for sure is that something is out there, 33.4 billion light years away.
And for now, that’s the furthest thing we can see. To get more information, and perhaps,
even further views of the universe, we will need the James Webb Space Telescope - the most powerful
infrared telescope of all. But until then, let’s be thankful for the sights Hubble has shown us,
and the 33 billion light-year journey it has allowed us to take. And what a journey it is.
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Thanks for watching! If you want more from Hubble, check out the playlist here.
A big thanks as always to my patrons and members, your help goes a long way.
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and you can find additional links in the description. All the best, and see you next time.