planet found in another galaxy

[dragon]

And some more news worthy astronomy news.

Astronomers believe they may have discovered the first planet ever detected in another galaxy. The new world was apparently glimpsed in the closest giant spiral galaxy to the Milky Way, Messier 31 in the constellation of Andromeda.

It lies an incredible 2.5 million light-years away - too far normally to be seen.

But it revealed itself thanks to a phenomenon called microlensing where the gravitational field of an object closer to Earth acts like a magnifying glass.

Amazingly, it has taken the astronomers five years to realise that they probably netted an extra-galactic planet. They observed a peculiar microlensing event while studying the Andromeda galaxy - which can be seen as a dim blur with the unaided eye - in 2004.

The international team, using the UK's Isaac Newton Telescope on the Canary Island of La Palma, thought at the time that they had recorded a pair of stars orbiting each other.

But computer simulations and other calculations have persuaded them that they actually observed a star with a smaller, planet sized companion about six times bigger than Jupiter.

More than 300 so-called exoplanets have been found orbiting other stars in our own galaxy. And NASA has launched a $595 million spaceprobe called Kepler to watch 100,000 stars for signs of world like Earth.

link

[Molyneux]

Is it reasonable to assume that if we spot one planet in another galaxy, then planets of that size are probably fairly common there (as they seem to be here)?

[Dave]

Is it reasonable to assume that if we spot one planet in another galaxy, then planets of that size are probably fairly common there (as they seem to be here)?

With a horrible quality sample of size n = 1, hell no.

The only reason we could see the thing was because there was something so big between us and the planet it caused a gravitational lensing effect to occur, coincidentally focusing the light on us.

So, we got extremely lucky just to see the thing, then we put it into the computer and it says "Eh, well, it kinda looks more like a planet than a star."

So we think we saw a planet, and we think it's six times the size of Jupiter.

Leaping to your assumption would be roughly akin to using a camera on the Moon to take a very blurry picture of a field of clover. The only one that stands still enough for you to make out with a magnifying glass has four leaves. "Thus," you say, "most clover have four leaves."


That being said, most of the other planets we have found are also "Hot Jupiters", however, that's because one of our early detection methods favors big planets really close to the star. (This method involves looking for the star wiggling due to gravitational pull of the planet. This favors massive, close-in planets due to the properties of gravity.)
It is still, however, unreasonable to assume that most planetary systems are like this, due to the inherent bias in our detection mechanism.

[Molyneux]

Is it reasonable to assume that if we spot one planet in another galaxy, then planets of that size are probably fairly common there (as they seem to be here)?

With a horrible quality sample of size n = 1, hell no.

The only reason we could see the thing was because there was something so big between us and the planet it caused a gravitational lensing effect to occur, coincidentally focusing the light on us.

So, we got extremely lucky just to see the thing, then we put it into the computer and it says "Eh, well, it kinda looks more like a planet than a star."

So we think we saw a planet, and we think it's six times the size of Jupiter.

Leaping to your assumption would be roughly akin to using a camera on the Moon to take a very blurry picture of a field of clover. The only one that stands still enough for you to make out with a magnifying glass has four leaves. "Thus," you say, "most clover have four leaves."


That being said, most of the other planets we have found are also "Hot Jupiters", however, that's because one of our early detection methods favors big planets really close to the star. (This method involves looking for the star wiggling due to gravitational pull of the planet. This favors massive, close-in planets due to the properties of gravity.)
It is still, however, unreasonable to assume that most planetary systems are like this, due to the inherent bias in our detection mechanism.

I figured that if it is unlikely for us to notice a planet if one exists, and we noticed one, then odds are that there are more planets that we didn't notice...

[Coyote]

It's nice to have confirmation that planets are indeed in existence even in other galaxies. I still recall when we had no real, dependable proof that there were planets outside our solar system at all.

But to hell with extragalactic stuff! We have, what, about 4 or so yellow main-sequence stars similar to the Sun within a 50 LY sphere of us, and another 4 or 5 red or blue phase stars that are still potential candidates for supporting life-bearing planets. I want to see results from examination of those. Something we might even get a probe to in under a century.