Lois & Clark Forums Forums General Discussion Off Topic 20 Years of the Hubble Telescope

It's better than ever in its old age!



really cool
Artemis

Thanks, Artemis! I was going to post something about this myself!

So if you don't mind, I'm going to comment on what it is we see in these fantastic images. First of all, what are those pillars made of? Open the link that Artemis gave you and look at the topmost image. If I say that the pillars are a little bit like pillar-shaped raging sandstorms, can you see the turbulent "sand" in them?

The pillars aren't true sandstorms and not true storms at all, however. Let's start by comparing them with an earthly cloud.



An earthly cloud like this one is made of water droplets. Usually there are water molecules - H2O - spread in the atmosphere, where they will be quite invisible and indistinguishable from the rest of the blue sky. But if there are enough water molecules in the air they can "clump together" to form tiny water droplets in the air, which will be visible if there are enough of them. What helps the formation of clouds is that the water droplets will block out some of the sunshine and cast tiny shadows in the air, thereby lowering the temperature there. The lower temperature will make it easier for more water vapor molecules to condensate out of the air, thereby forming more water droplets and making the cloud grow.

So on the Earth, a cloud is made of larger particles than the surrounding atmosphere, and it is colder inside the cloud than in the clear atmosphere around it. It is exactly the same thing with the fantastic "pillars" that Hubble photographed - they are made of larger particles than the surrounding "interstellar medium", and the temperature inside the pillars is lower than the temperature outside them.

Earthly clouds are mostly made of water droplets. The pillars that Hubble photographed are mostly made of "the exhaust fumes of dying stars", which are tiny, tiny particles of carbon, silicon (rock) and various ices. When stars die, they produce such particles and "blow them out into space" like an erupting volcano!



Eyjafjallajökull on Iceland has been blowing large amounts of ash into the air. The ash consists of tiny particles of various rocks and other elements, mixed with water vapor and water droplets. A dying star puffs a mixture of particles out into space in much the same way as an earthly volcano.

In space, an "ash cloud" from a dying star will act like a large, shallow gravity well.



A gravity well. A concentration of matter will "weigh down" the fabric of spacetime, causing an indentation in it. Other objects in the vicinity of the well will feel the "downhill slope" and starting sliding down it. Space is mostly empty, but wherever you go in our galaxy there will be a few atoms of hydrogen gas nearby. So the hydrogen will start sliding down the gravity well which was made by the "ash could" of the dying star's "exhaust fumes". As hydrogen slides down the graity well to mix with the cloud, the gravity well will become deeper, and more hydrogen will be captured and "fall down" to mix with the cloud. Over time, a huge amount of hydrogen may be captured, and it will start contracting because of its own self-gravity.

What do you get when a large cloud of tiny dust particles and hydrogen gas really starts contracting? You get a new star, that's what. Or at least you do if the cloud is concentrated enough and cold enough on the inside. To form a new star, the gas cloud must be very still so that it can keep contracting without being blown apart by its own turbulence. And the tiny dust particles help shield the cloud from outside influences and help cool down the cloud.

The best birth places of massive stars are the massive "dark nebula". This dark nebula isn't very massive, and it isn't the birthplace of massive stars at all. But the nebula is indeed made of gas and dust and it is colder than its surroundings, and it gives you an idea of what it takes to form massive stars.



When a huge amount of gas and dust becomes very concentrated, it can lead to a runaway production of massive and blisteringly hot stars. This is cluster NGC 3603, of the the largest and most massive young clusters in our galaxy:



Please ignore the bright greenish and orangish stars here, because I can't tell you anything about them. But take a look at the purplish wisps of gas below and to the left of the cluster. Can you see that there is a "pillar" in the gas cloud below the cluster, and actually another, fainter pillar in the wisps of gas to the left?

The pillars near NGC 3603 are more visible in this Hubble picture. Here the pillars are to the right and lower right of the cluster:



In this picture you can also see a dying supergiant star to the upper left of the cluster. The star is surrounded by a blue ring, and it emits two jets out into space. You can see the ends of the jets as two bluish puffs of gas at opposite sides of the star.

But let's return to the pillars near NGC 3603. These pillars are the most concentrated parts of what is left of the once-massive gas cloud that has now been mostly used up in the production of the massive cluster. It is the same thing with the pillars you can see in teh new Hubble picture of the Carina region: the pillars are the leftovers of gas that has been mostly used up. For all of that, there is activity going on on the inside and the outside of the pillars!

On the inside, there are a few new stars born. Pillars never contain a lot of gas, so the stars that are born in them will be low-mass stars. Nevertheless, the fact that a new star is being born inside the pillar will certainly wreak a bit of havoc and cause a lot of turbulence in the pillar. Please open the link that Artemis gave you and take a look again. Surely you can see how the pillars seem to turn and twist as if in agony? Surely you can see how parts of the "surface" of the pillars seem to erupt from within? That is because of the new stars inside them. And the dramatic jets are the direct evidence of new stars being born, because stars emit jets to shed "angular momentum" (spin) as they accrete mass. If they didn't emit those jets as they grow in mass, they wouldn't be able to accrete enough mass to become stars in the first place.

But the pillars are also strongly affected by the bright, hot, massive stars in their vicinity, whose relentless ultraviolet light is pounidng down on them. Look at the pillar on the left. See how something is dramatically "evaporating" from its left side and glowing as it does so? What we are seeing is actually the pillar being slowly destroyed by a hot star on its left side. The pillar is being disintegrated by the ultraviolet light of a hot star, and it is glowing as it is disappearing.

Fascinating, isn't it?

Ann

Ah, the Carina Nebula. It's one of my all-time favorites. And, yes, Ann, I already knew about this star-formation stuff you mentioned. Well, most of it anyway.