Hyperfast Star proven to be from outside our Galaxy

[n2doc]

ScienceDaily (Jan. 29, 2008) — A young star is speeding away from the Milky Way so fast that astronomers have been puzzled by where it came from; based on its young age it has traveled too far to have come from our galaxy. Now by analyzing its velocity, light intensity, and for the first time its tell-tale elemental composition, Carnegie astronomers Alceste Bonanos and Mercedes López-Morales, and collaborators Ian Hunter and Robert Ryans from Queen's University Belfast have determined that it came from our neighboring galaxy, the Large Magellanic Cloud (LMC). The result suggests that it was ejected from that galaxy by a yet-to-be-observed massive black hole.

The star, dubbed HE 0437-5439, is an early-type star and one of ten so-called hypervelocity stars so far found speeding away from the Milky Way. "But this one is different from the other nine," commented López-Morales. "Their type, speed, and age make them consistent with having been ejected from the center of our galaxy, where we know there is a super-massive black hole. This star, discovered in 2005*, initially appeared to have an elemental makeup like our Sun's, suggesting that it, too, came from the center of our galaxy. But that didn't make sense because it would have taken 100 million years to get to its location, and HE 0437-5439 is only 35 million years old."

To explain the enigma, or "paradox of youth," the discoverers proposed that HE 0437-5439 was either a so-called blue straggler--a relatively young, massive star resulting from the merger of two low-mass stars from the Milky Way, or it originated from the Large Magellanic Cloud.

"We were intrigued by the conundrum and decided to take up the challenge to solve this," stated Bonanos. "Stars in the LMC are known to have lower elemental abundances than most stars in our galaxy, so we could determine if its chemistry was more like that galaxy's or our own."

The team confirmed results of the previous study concerning the mass, age, and speed of the star. It is about nine times the mass of our Sun, about 35 million years old, and it is zooming away from the Milky Way and Large Magellanic Cloud into intergalactic space at 1.6 million miles per hour (2.6 million km/hour).

more:
http://www.sciencedaily.com/releases/2008/01/080128113256.htm

[lurky]

1. Cool!

Sometimes I forget what a tumultuous place the universe is.

[damntexdem]

2. Good riddance -- we don't want them Magellanic stars on our turf!

Let them go back where they came from!

Err, well, I guess it's going too fast for that.

Forget Texas -- let's build a border fence around the Milky Way!

;-)

[htuttle]

3. 1.6 million miles per hour is about 0.2% the speed of light, right?

I wonder if time dilation has any effect on it's apparent age to us? It doesn't seem quite fast enough, but 35 million years (old) is a long time...

[caraher]

4. 35 million years is not a lot for a star

As for time dilation yes, that's about 0.002 c, which in turn implies that the time dilation factor is well under 1%. The age estimates are nowhere near that precise, so the effect you mention is real but not discernible given all the other uncertainties that go into that estimate.

The way I look at 35 million years for a star is that the mass dinosaur extinction was just over 60 million years ago. So bones of the last dinosaurs had already spent 25 million years or so lying lifeless before this star was born! And you can compare those times to the age of the Earth, the solar system, etc., measured in billions of years - the star's age is less than 1% of Earth's age!

[htuttle]

5. True

That is a very young star. I guess I hadn't ever thought of 35 million years as 'just the blink of an eye' before. :D

[tridim]

6. The galaxy is just playing baseball.

[krispos42]

7. Sounds a little like a Larry Niven short story

Rich guy wants an adventure, buy knowledge from the puppeteers of an "exciting" star to visit. An extra-galactic star shooting through our galaxy at a significant fraction of the speed of light. So he goes to visit it.

Turns out the entire star, with its attendant planets and such, was composed entirely of anti-matter. Found out when the positon and anti-proton solar wind from the star dissolved his hull.

Oopsie!