Starship Asterisk*

NGC 604: Giant Stellar Nursery

Explanation: Stars are sometimes born in the midst of chaos. About 3 million years ago in the nearby galaxy M33, a large cloud of gas spawned dense internal knots which gravitationally collapsed to form stars. NGC 604 was so large, however, it could form enough stars to make a globular cluster. Many young stars from this cloud are visible in the above image from the Hubble Space Telescope, along with what is left of the initial gas cloud. Some stars were so massive they have already evolved and exploded in a supernova. The brightest stars that are left emit light so energetic that they create one of the largest cloud of ionized hydrogen gas known, comparable to the Tarantula Nebula in our Milky Way's close neighbor, the Large Magellanic Cloud.

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"Oooooo, Look at the Lit'ool baaaaybeees..."

Wow, this is a close up of a section in another GALAXY, this is a fantastic shot. Awesome.

Near the top, to the right, and just above the main star cluster, appears to be a SANTA HEAD... HE IS REAL!!! If you look at it just right, he appears to be bent over a little and zooming on SKIES!!!!

Nice Picture, the weather here has been one system after another since Early October, and haven't been able to get out to do anything.

:---[===] *

Amazing region of starbirth (and death)! IMO this version is better processed than the original, especially in regards to the colour. Hopefully Ann will love this!!

My question is this: per the description of this photo, spawned knots of gas are sufficient to collapse upon themselves gravitationally and thus birthing stars, what then causes these actual gravitational-collapsing knots of gas to form and how do they form in gas clouds? Do these massive knots form randomly?

Thanks in advance.

Two thumbs up for this beautiful APOD!

starsurfer wrote:Amazing region of starbirth (and death)! IMO this version is better processed than the original, especially in regards to the colour. Hopefully Ann will love this!!

I like it a lot! Very nice! Let me add that I think it's a great idea that people do their own processed versions of Hubble images. Some of the new versions do look better than the old ones, at least if you ask me...

Speaking about NGC 604, I must ask you to check out one of my favorite (and very blue!) pictures of NGC 604. The blue light in this picture is X-rays. You can see from the picture that the star formation in NGC 604 is concentrated to the upper right part of the nebula in this image, but the star-poor left part of the nebula is just as blue and just as full of X-rays as the star-rich part of it. The reason for all the blue light in the star-poor left part of NGC 604 is that it is full of X-rays from past supernovae, while the middle-right part of NGC 604 contains enough massive young binaries to generate the amount of X-rays that we see here.

Starbirth and star death, as you said, starsurfer!

Ann

SouthEastAsianSky wrote:My question is this: per the description of this photo, spawned knots of gas are sufficient to collapse upon themselves gravitationally and thus birthing stars, what then causes these actual gravitational-collapsing knots of gas to form and how do they form in gas clouds? Do these massive knots form randomly?

Thanks in advance.

Someone else should answer your question. For all of that, take a look at this picture of water and foam going down the drain. How do the patches of foam form in this swirling liquid system? Where do they form? Is the process completely random?

A galaxy isn't a system where everything is going down the drain. And patches of foam are not like molecular clouds collapsing under their own gravity to form stars. For all of that, I think there are similarities - fluid motions, interactions, random concentrations - which lead to patches of foam forming in some locations in a swirling liquid and not in others, and molecular gas becoming concentrated in some parts of a spiral galaxy and not in others.

Ann

Suppose we are in the middle of a nebula. Can we feel it? Is it in any way distinct from empty space to our human senses?

Sinan İpek wrote:Suppose we are in the middle of a nebula. Can we feel it? Is it in any way distinct from empty space to our human senses?

If we were in the middle of an emission nebula like this one, we'd see nothing. It would only be detectable instrumentally. If we were in the middle of a very dusty nebula, the attenuation would reduce the number of stars we could see. In either case, the density of material is extremely low- the densest nebulas are still hard vacuums. So they would have insignificant physical effects on the local environment. And the solar wind around an interior star keeps its own system even less dense.

Chris Peterson wrote:

Sinan İpek wrote:Suppose we are in the middle of a nebula. Can we feel it? Is it in any way distinct from empty space to our human senses?

If we were in the middle of an emission nebula like this one, we'd see nothing. It would only be detectable instrumentally. If we were in the middle of a very dusty nebula, the attenuation would reduce the number of stars we could see. In either case, the density of material is extremely low- the densest nebulas are still hard vacuums. So they would have insignificant physical effects on the local environment. And the solar wind around an interior star keeps its own system even less dense.

Thanks for the answer.

This is a lovely picture, much more attractive than the Hubble palette. Others have already commented on the wonder of seeing individual stars in another galaxy, red for Christmas and blue for Ann, and the physics of swirling foam and spiral galaxies. Perhaps because I went to the California Revels with friends on Sunday night, this particular apod seems very appropriate to the yuletide season. Ann, thanks for the X-ray picture, perhaps the lingering X-rays from supernovas are the ghost of Christmas past?

Apologies for my lack of understanding here, but where did such a large gas and dust cloud come from in the first place?

random wrote:Apologies for my lack of understanding here, but where did such a large gas and dust cloud come from in the first place?

There are others on the good ship Asterisk much better qualified than I am to answer your question in more detail, but I'll give it a try. So far as we know, all the matter in the universe was created in the big bang. The cosmic microwave background radiation shows us that the distribution of matter in the early universe was slightly uneven, with areas of slightly greater density and areas that were slightly less dense. Over the 13.7 billion year life span of the universe, the attractive force of gravity has accentuated the unevenness of matter at every observable scale. Galaxy clusters are surrounded by relatively empty voids, as are individual galaxies within clusters. The spiral arms of galaxies such as our own Milky Way and M33 are especially good at creating density variations including areas of relatively dense cool gas, such as this nebula, in which stars are born. The individual stars themselves are a further expression of the tendency of gravity to bring bits of matter closer to one another and to produce pretty and interesting things to look at.

Dark matter and dark energy are recently discovered plot twists in this overall story, but you don't need to understand them to understand why we see pretty nebulae in our galaxy and other nearby galaxies.

And please don't apologize for your lack of understanding -- you're in good company here! Your crewmates will only give you a hard time if you profess a false or unsubstantiated understanding.

random wrote:Apologies for my lack of understanding here, but where did such a large gas and dust cloud come from in the first place?

Anthony just explained how gas and dust were created in the first place. Perhaps you were asking how such a large clump of gas and dust could come into existence in this particular galaxy.

It is important to understand that some galaxies are gas-rich and others are not. If a galaxy is gas-poor, it is a virtual certainty that there will be no big local concentrations of gas and dust in it, a there will be only small amounts of star formation.

Take a look at this ESO image of the two galaxies that are bystander's avatar, NGC 4435 and NGC 4438. These galaxies are gas-poor for two reasons. They have probably been orbiting one another for quite a long time, and they are also members of a crowded part of the Virgo cluster of galaxies. For perhaps billions of years, all their interactions with each other and other galaxies have made them have undergo one bout of star formation after another, gradually using up most of the gas they were born with, and now they have converted most of their gas into stars. In this picture, you can see NGC 4435 and 4438 close to the center of the picture, surrounded by other galaxies.

Galaxies also lose mass to the space around them, and they don't always get this gas back. Some of it is just lost. Take a look at this picture of M82. There are tremendous outpourings of gas from this galaxy, likely due to a great number of supernovae near the center of it, and the galaxy isn't likely to get all of this gas back. And when the gas is lost, or mostly lost, there will be no more large clumps of gas and dust in this galaxy and no more massive star formation.

Take a look at this picture of Stephan's Quintet, an interacting group of galaxies. The largest blue galaxy is a foreground galaxy and not part of the action. You can see a large "arc" of individual pink knots near the center of the picture. These are all concentrated clumps of gas and dust undergoing tremendous star formation due to a mighty collision between two galaxies. The interaction here is pretty "fresh", and at least one of the galaxies had a lot of gas to "set fire to".

M101 , the Pinwheel galaxy, is very gas-rich. It is interacting with a few small dwarf galaxies. The interaction has spawned large-scale star formation in M101. You can see some really huge pink emission nebulae in this picture.

As for galaxy M33, host of NGC 604, it interacts with the large Andromeda galaxy. Andromeda could be a real bully and "suck M33 dry" pretty fast. It hasn't happened, though, probably because M33 is located at a safe distance from Andromeda. Compare M33 with hapless dwarf galaxies M32 and NGC 205 - Andromeda has stolen all the gas that originally belonged to M32, and there isn't much gas left in NGC 205. M32 is at upper left and NGC 205 at lower right in this picture.

Ann

random wrote:Apologies for my lack of understanding here, but where did such a large gas and dust cloud come from in the first place?

Some really good answers here. I think the gist of the "matter" (sorry) is that matter has gravity. Gas has existed since the Big Bang as the most basic form of matter once it formed. It is also released, now, from supernovae and other stellar explosions, along with a lot of dust. The basic concept is that mass is proportional to gravity. Anything that has mass has a gravitational pull on other things with mass. Even though the atoms/molecules in a gas cloud are very tiny, cumulatively, they have mass and thus gravity. This gravitational force is what causes the gas to condense into a cloud that can form stars in the most dense regions.

Interestingly, as the cloud condenses and forms stars, the radiant energy and light from the formation process and newly formed stars actually exerts force on the gas and dust, blowing it away from the very star that it formed. That's why so many nebula appear lit from the inside as this stellar wind has blown out a clearing around the star. It is somewhere in this balance of gravitational attraction and stellar wind that enough material can clump up around the new star, if it's the right kind, and begin to form planets!

On another note, the pretty pictures are nice but someone did bring up a good point! What would you actually see if you were flying through one of these regions of space??? I think we can digitally edit the pictures to show things we might not otherwise notice, such as using a false color to show X-Ray or Infrared sources. However, being a bit of a purist, I prefer, at most, a careful balance of the original filtered images to approximate the true colors, had we eyes with the f ratio of Hubble!

Ann wrote:

random wrote:Apologies for my lack of understanding here, but where did such a large gas and dust cloud come from in the first place?

Anthony just explained how gas and dust were created in the first place. Perhaps you were asking how such a large clump of gas and dust could come into existence in this particular galaxy.

It is important to understand that some galaxies are gas-rich and others are not. If a galaxy is gas-poor, it is a virtual certainty that there will be no big local concentrations of gas and dust in it, a there will be only small amounts of star formation.

... [words and pictures] ...

Ann

Ann, you are very kind and diplomatic. Thanks for the illustrated tour! You've made a big dent in my still quite massive ignorance!