Andromeda three times larger than thought

Firefox · Post by **Firefox** » 2005-05-30 03:59pm

Space.com wrote:MINNEAPOLIS, MN – We know less about our nearest galactic neighbor than thought, astronomers announced today. A map of the outer suburbs of the Andromeda galaxy finds that its rotating disk of stars is three times bigger than previously measured.

The Andromeda galaxy is a spiral galaxy similar to our own Milky Way. Although there are smaller dwarf galaxies nearer to us, Andromeda is the closest large galaxy – at about 2 million light-years from Earth. A light-year is the distance light travels in a year, about 6 trillion miles (10 trillion kilometers).

Under dark skies, Andromeda can be seen by the naked eye as a large fuzzy blob.

3 times bigger

Scott Chapman from the California Institute of Technology presented the results of a survey of Andromeda's stellar motions here at the 206th Meeting of the American Astronomical Society.

"What we have done is measured the radial velocity of stars in the outer regions – basically, how fast they are moving towards us or away from us," Chapman said during a press conference this morning.

Chapman was one of a team of astronomers using the Keck telescope to measure speeds of 5,000 stars in the outskirts of Andromeda. They were surprised to find that these suburban stars were actually rotating as if they were part of the galaxy's disk. Their paths had been expected to be more random.

"Finding all these stars in an orderly rotation was the last explanation anyone would think of," Chapman said.

The implication is that the disk is 220,000 light years in diameter, instead of the earlier estimates of 70,000 to 80,000 light years. In our sky, that means Andromeda stretches out over the length of 12 full Moons.

This periphery of Andromeda is faint – it accounts for about 10 percent of the light from the galaxy. Still, there are millions of stars presumably orbiting in this outer region

A bizarre fossil record

By looking at separate components of a galaxy one can try to piece together how the galaxy built up over time. The central region of a spiral galaxy is believed to have formed first, with the rotating disk coming later. The type and orbit of stars in certain regions provides a kind of fossil record for the evolutionary history.

Andromeda is an "ideal laboratory" because it is so close, and yet it is outside our galaxy.

"It is very hard to study this evolution in our own galaxy because we are stuck in the middle of it," Chapman said.

And yet this laboratory is full of puzzles as to how it came to be. Besides Andromeda's new size, the researchers are scratching their heads over the fact that the outer rotating stars are arranged into about 20 identifiable clumps. This would imply that they formed out of the merger of smaller galaxies with the main galaxy.

But rotating disks and clumps are not compatible in galaxy formation models.

"This giant disk discovery will be hard to reconcile with computer simulations of forming galaxies," said Rodrigo Ibata of the Observatoire Astronomique de Strasbourg in France. "You just don't get giant rotating disks from the accretion of small galaxy fragments."

Chapman said that if a merger is the correct explanation, it would have had to occur relatively recently – within the last 200 million years. Otherwise, the clumps should have been "washed out." We may, therefore, being viewing our big neighbor at a rare moment in its history – right after it has gobbled up one of its little neighbors.

Pretty cool.

CaptainChewbacca · Post by **CaptainChewbacca** » 2005-05-30 04:32pm

So, if its periphery is that large, it means there are more stars similar to Sol in their distance from the center, which is not a safe place to be.

Admiral Valdemar · Post by **Admiral Valdemar** » 2005-05-30 04:39pm

It's not much safer in the outer rim either in many respects, but beats being near the supermassive black hole that inevitably forms a part of the core and all the accumulated junk and radiation of there too.

Enforcer Talen · Post by **Enforcer Talen** » 2005-05-30 04:41pm

nowhere is safe. . .

wolveraptor · Post by **wolveraptor** » 2005-05-30 05:05pm

I've heard that galactic merging is a relatively safe process for hypothetical aliens on planets orbiting stars within the merging galaxies. The likelyhood of star collision is supposed to be quite low IIRC.

Enforcer Talen · Post by **Enforcer Talen** » 2005-05-30 05:05pm

arent we supposed to be crashing with a nearby galaxy at some point?

FedRebel · Post by **FedRebel** » 2005-05-30 06:09pm

Enforcer Talen wrote:arent we supposed to be crashing with a nearby galaxy at some point?

Andromeda is due to colide with us in about 3 billion years

SPOOFE · Post by **SPOOFE** » 2005-05-30 10:14pm

Andromeda doesn't exist. It's just a trick of the devil.

GrandMasterTerwynn · Post by **GrandMasterTerwynn** » 2005-05-30 10:42pm

wolveraptor wrote:I've heard that galactic merging is a relatively safe process for hypothetical aliens on planets orbiting stars within the merging galaxies. The likelyhood of star collision is supposed to be quite low IIRC.

Yes. The distance between stars, relative to their own diameters, is much, much, much greater than the relative distance between galaxies. It would be much akin to two clouds of smoke passing through each other.

Though it's not quite as safe as you're making it seem. Such collisions wreak havoc on the structures of the two galaxies involved, rearranging stellar orbits and the like. Once the merger is complete, you could find yourself in an orbit which carries your star through the densest inner regions of the new galaxy, where you'll be fried by the intense starburst and supernova activity that resulted from the galactic collision.

Worse still, if you plan to leave your solar system, your star could find itself on a very slow, but one-way trip out of the galaxy into intergalactic space.

Zero · Post by **Zero** » 2005-05-30 10:56pm

Even if the stars don't collide, I imagine there will be pretty decent gravitational effects which can really mess up the orbits of asteroids and things like that. Even if we didn't collide with anything, we could pass through some kind of dust cloud which could block out the sun for years, mess up our atmosphere, all kinds of crap. Of course, that's not very likely. The gravity thing is an issue, though. If gravitational effects are messy enough, we might not stay with our own galaxy. What I'm wondering is, what's so dangerous about entering intergalactic space?

Post by **Coyote** » 2005-05-31 01:24am

Isn't the Milky Way supposed to be 100,000 LY in diameter, give-or-take? Would this mean that to them, we are the dwarf galaxy?

Firefox · Post by **Firefox** » 2005-05-31 01:29am

I wish I could relocate the article, but I've heard the MW is slightly larger (approximately 120,000 ly across) than originally thought, based on research such as this.

As far as calling our galaxy a dwarf, not by a long shot. Galaxies such as irregulars and dwarf ellipticals (holding only a few billion stars) fit that category.

Dennis Toy · Post by **Dennis Toy** » 2005-05-31 02:38am

What I'm wondering is, what's so dangerous about entering intergalactic space?

outside the galaxies, radiation is so strong that it would destroy all life on a space craft.

Dooey Jo · Post by **Dooey Jo** » 2005-05-31 08:45am

That's odd. I'm pretty sure my astronomy book said Andromeda was about 160 000 LY in diameter. And I'm absolutely sure it said it was quite a bit larger than the Milky Way. And that book was printed in -94...

GrandMasterTerwynn · Post by **GrandMasterTerwynn** » 2005-05-31 09:33am

Dennis Toy wrote:
What I'm wondering is, what's so dangerous about entering intergalactic space?
outside the galaxies, radiation is so strong that it would destroy all life on a space craft.

That would be hard to do, given the relative distance you'd be from most major sources of radiation. The difficult thing about intergalactic space is that there's virtually nothing there. The vast majority of the universe's visible matter is clumped into galaxies. The night sky of a planet orbiting a star in intergalactic space would be perfectly black, except for the planets orbiting the star with you, and maybe a large fuzzy patch or two just bright enough for you to percieve . . . depending on how long ago the intergalactic collision was that pitched you into intergalactic space.

Zero · Post by **Zero** » 2005-05-31 12:19pm

Why would this be bad, or dangerous? I mean, the radiation thing just doesn't make much sense... if someone can explain a reason why this is, then I'll take a look. To me, it could be an advantage of sorts to be away from most matter in the universe. Less likely to have gravitational disturbances and impacts and such. If there's less around, I can imagine that less would hurt you.

wolveraptor · Post by **wolveraptor** » 2005-05-31 12:22pm

Sure, but it'll be a helluva lot harder to colonize other planets. Depending on the exit speed, you might have to hurry up the development of spacefaring technology, before it's too late (i.e. too far away).

GrandMasterTerwynn · Post by **GrandMasterTerwynn** » 2005-05-31 01:18pm

Zero132132 wrote:Why would this be bad, or dangerous? I mean, the radiation thing just doesn't make much sense... if someone can explain a reason why this is, then I'll take a look. To me, it could be an advantage of sorts to be away from most matter in the universe. Less likely to have gravitational disturbances and impacts and such. If there's less around, I can imagine that less would hurt you.

The problem being that the next closest star to you would be between several tens of thousands of lightyears away, to several million lightyears away. You would be trapped in your own solar system until you used it all up, or your sun leaves the main sequence.

Lord Zentei · Post by **Lord Zentei** » 2005-05-31 02:13pm

Coyote wrote:Isn't the Milky Way supposed to be 100,000 LY in diameter, give-or-take? Would this mean that to them, we are the dwarf galaxy?

~160000 light years, actually. Or galaxy is far larger than most, and structurally unlike dwarf galaxies, so "probably not".

Zero · Post by **Zero** » 2005-05-31 06:03pm

It doesn't seem like we've made any efforts at all to try and escape our solar system yet. What makes you think we will at all, ever? We all see it as a necessity, but it can really help very few things along, as far as earth goes. We couldn't leave in large enough quantities to stop an overpopulation problem, and many people want to stay here. Since many people are greedy, and most people wouldn't get to leave, any efforts to leave the solar system aren't likely to go so well, anyways. And so far, we haven't even found an earth-sized planet yet, even. What makes you think a viable goal outside of the solar system can ever be established and reached?

Firefox · Post by **Firefox** » 2005-05-31 06:09pm

Zero132132 wrote:We couldn't leave in large enough quantities to stop an overpopulation problem, and many people want to stay here.

Who said anything about alleviating any overpopulation problem? The point of colonizing other planets is to ensure the survival of our species. It would be far more difficult to wipe us out if we lived on a number of systems, versus sticking to one planet.

wolveraptor · Post by **wolveraptor** » 2005-05-31 06:46pm

Personally, I'm looking forward to a massive alien invasion of Earth, and I'll laugh at all you retards who said, "Well, let's NOT be adventurous and explore the galaxy. Let's just stay here."

Seriously: my optimistic side for the human race tells me that natural primate adventurousness will lead us to colonize other worlds, whether we need to or not.

Zero · Post by **Zero** » 2005-05-31 06:51pm

My point is that nobody will ever see any immediate reasons to leave, so the formulation of a long term project to colonize other planets isn't a likely situation. Since there's no way such things would improve our lives here on earth, I see it as quite likely that people simply won't leave. There will be no desire to, and people won't pay for it. We're going to stay here on planet earth until our sun leaves the main sequence. Of course, by then, we'll have killed each other off... or a new species will have risen to sentience. Perhaps several, at that point... who knows?

SirNitram · Post by **SirNitram** » 2005-05-31 07:02pm

Zero132132 wrote:My point is that nobody will ever see any immediate reasons to leave, so the formulation of a long term project to colonize other planets isn't a likely situation. Since there's no way such things would improve our lives here on earth, I see it as quite likely that people simply won't leave. There will be no desire to, and people won't pay for it. We're going to stay here on planet earth until our sun leaves the main sequence. Of course, by then, we'll have killed each other off... or a new species will have risen to sentience. Perhaps several, at that point... who knows?

You failed history, didn't you?

There have always been those who journey to new frontiers. It didn't matter if it was death and unprofitable. For their own unfathomable reasons they went.

Noble Ire · Post by **Noble Ire** » 2005-05-31 07:02pm

Firefox wrote:
Zero132132 wrote:We couldn't leave in large enough quantities to stop an overpopulation problem, and many people want to stay here.
Who said anything about alleviating any overpopulation problem? The point of colonizing other planets is to ensure the survival of our species. It would be far more difficult to wipe us out if we lived on a number of systems, versus sticking to one planet.

Beware of the Covenant.