Galaxy ate neighbour

mr friendly guy · Post by **mr friendly guy** » 2006-02-15 08:32pm

Scientists say galaxy ate neighbour
By Judy Skatssoon for ABC Science Online

Astronomers have released new evidence to show that a region of stars in our galaxy known as the Arcturus stream is the digested remains of what was once a neighbouring galaxy.

The evidence is among the first to come from the largest star study to date, with data from 25,000 stars just released at a US astrophysics workshop.

Dr Quentin Parker of Sydney's Macquarie University and the Anglo-Australian Observatory is head of data management at the international Radial Velocity Experiment (RAVE), which uses Australia's UK Schmidt telescope.

Dr Parker says the latest results provide a smoking gun for the argument that the Milky Way is a voracious cannibal that devours its neighbours.

"We've confirmed the Arcturus moving group as being a star stream, which indicates a disruptive galaxy spiralled into our own," he said.

"Ours is a large galaxy and it has been eating other galaxies; it's been hungry. We can see what it's eaten by the crumbs that are left over from its meal."

It is another bit of evidence for the now widely accepted cannibal, or accretion, theory of galactic evolution, Dr Parker says.

This theory says the gravitational pull of large galaxies sucks in smaller ones, making large galaxies like our own a sort of cosmic melting pot.

Dr Parker says the RAVE measurements show stars in the Arcturus group are travelling at a similar velocity and in a similar direction through space, indicating they were once part of a coherent system.

"Using ... star velocities it's possible for the first time begin to unravel the way our galaxy is constructed," he said.

The RAVE study is measuring the speed of a million stars in the Milky Way using radial velocity, or the motion of a star along the line of sight between the telescope and the star.

The huge scope of the survey has been made possible by the six degree field (6dF) spectrograph on the 1.2 metre UK Schmidt Telescope at the Anglo-Australian Observatory, which can obtain spectroscopic information for up to 150 stars at once.

The telescope splits light from the stars into a wide spectrum of colours and by looking at specific colours produced by calcium atoms astronomers can work out whether the colours have "shifted" in the spectrum.

This enables them to work out aspects of the star's movement.

"We're looking at the stars in our galaxy and measuring their velocity by measuring how their lines have shifted," Dr Parker said.

The survey has so far collected information about 90,000 stars and will release data on the remaining 65,000 as it is analysed.

FSTargetDrone · Post by **FSTargetDrone** » 2006-02-16 12:12pm

Fascinating! Even more so that it's the Milky Way.

Ah, the wonders of the universe. Just imagine, it all came about on its own, without any sort of mystical originator. For me, it makes things like this all the more amazing.

Bertie Wooster · Post by **Bertie Wooster** » 2006-02-16 12:22pm

I must say, this news makes me proud to be an inhabitant of the Milky Way.

Go Milky Way, UNDEFEATED!!!

On a serious note, what would happen if the Milky Way got eaten by a larger galaxy? Would out solar system be able to survive?

Post by **Surlethe** » 2006-02-16 12:25pm

Bertie Wooster wrote:On a serious note, what would happen if the Milky Way got eaten by a larger galaxy? Would out solar system be able to survive?

The Andromeda Galaxy is going to eat us in a few billion years, IIRC. The solar system is probably going to be fine; there's plenty of empty space in the galaxy for us to pass through.

Shinova · Post by **Shinova** » 2006-02-16 01:27pm

Curses! The Andromeda galaxy is undoubtedly harboring terrorists and weapons of mass destruction! We must initiate regime change!!!

wolveraptor · Post by **wolveraptor** » 2006-02-16 01:34pm

I still don't understand how Andromeda is moving away from us, yet is still getting closer.

ClaysGhost · Post by **ClaysGhost** » 2006-02-16 01:44pm

wolveraptor wrote:I still don't understand how Andromeda is moving away from us, yet is still getting closer.

What? It's moving towards us, not away (at about 300km/sec, IIRC)

GrandMasterTerwynn · Post by **GrandMasterTerwynn** » 2006-02-16 02:11pm

wolveraptor wrote:I still don't understand how Andromeda is moving away from us, yet is still getting closer.

It is closing in on us, not moving away. And neither galaxy will reallly "eat" the other. The result will be a large elliptical galaxy bearing relatively little trace of the original spirals.

Darth Servo · Post by **Darth Servo** » 2006-02-16 02:24pm

Shinova wrote:Curses! The Andromeda galaxy is undoubtedly harboring terrorists and weapons of mass destruction! We must initiate regime change!!!

shhhhhhh. Don't give Shrubby and company any ideas.

kheegster · Post by **kheegster** » 2006-02-16 02:25pm

How funny to see Quentin Parker being quoted in an article posted here, considering I first met him at Siding Spring where the 1.2m UK Schmidt telescope mentioned in the article is located.

He's one of the most comical characters I know of....

The UKST is the dome on the right...

Lord Zentei · Post by **Lord Zentei** » 2006-02-16 03:17pm

Darth Servo wrote:
Shinova wrote:Curses! The Andromeda galaxy is undoubtedly harboring terrorists and weapons of mass destruction! We must initiate regime change!!!
shhhhhhh. Don't give Shrubby and company any ideas.

Hey, if it would bring about research grants for advanced space travel technologies, I'm OK with it.

You need to be able to reach the bad guys to kick their asses, after all.

Ariphaos · Post by **Ariphaos** » 2006-02-17 02:32am

Surlethe wrote:The Andromeda Galaxy is going to eat us in a few billion years, IIRC. The solar system is probably going to be fine; there's plenty of empty space in the galaxy for us to pass through.

Latest estimate of Andromeda mass: 1.25 trillion Solar masses (quite the heavyweight, considering all the hoopla about finding a trillion solar mass galaxy a decade ago!)

.....

Latest estimate of Milky Way mass: 1.9+ trillion Solar masses. To my knowledge no larger spiral has been found.

Milky Way for the win!

Mange · Post by **Mange** » 2006-02-17 02:41am

Xeriar wrote:
Surlethe wrote:The Andromeda Galaxy is going to eat us in a few billion years, IIRC. The solar system is probably going to be fine; there's plenty of empty space in the galaxy for us to pass through.
Latest estimate of Andromeda mass: 1.25 trillion Solar masses (quite the heavyweight, considering all the hoopla about finding a trillion solar mass galaxy a decade ago!)

.....

Latest estimate of Milky Way mass: 1.9+ trillion Solar masses. To my knowledge no larger spiral has been found.

Milky Way for the win!

Well, the largest known spiral galaxy, UGC 2885, is 815,000 ly across and has a mass of over 2 trillion Solar masses...

Ariphaos · Post by **Ariphaos** » 2006-02-17 03:06am

Mange the Swede wrote:Well, the largest known spiral galaxy, UGC 2885, is 815,000 ly across and has a mass of over 2 trillion Solar masses...

Oooer. I thought it was still only considered to be 'over 1 trillion' a la:

http://www.nofs.navy.mil/about_NOFS/sta ... u2885a.pdf

Not that it's hard to doubt.

Even still, the Milky way is incredibly massive, despite its visible size being so small. The size of the dark matter halo is more competitive, and the Milky Way remains (for now) a barred spiral, and will remain such until Andromeda hits it.

Mange · Post by **Mange** » 2006-02-17 04:39am

Xeriar wrote:
Mange the Swede wrote:Well, the largest known spiral galaxy, UGC 2885, is 815,000 ly across and has a mass of over 2 trillion Solar masses...
Oooer. I thought it was still only considered to be 'over 1 trillion' a la:

http://www.nofs.navy.mil/about_NOFS/sta ... u2885a.pdf

Not that it's hard to doubt.

Even still, the Milky way is incredibly massive, despite its visible size being so small. The size of the dark matter halo is more competitive, and the Milky Way remains (for now) a barred spiral, and will remain such until Andromeda hits it.

Hmm, I've seen a figure of 2x10e12 M, but it's unimportant. You're quite right, the Milky Way is very massive.