13-Billion-Year-Old Alien Worlds Discovered

astroengine writes "Two exoplanets have been discovered by scientists at the Max-Planck Institute for Astronomy orbiting the star HIP 11952. But according to conventional thinking, these worlds shouldn't exist. You see, HIP 11952 is a 'metal-poor star and planetary formation is hindered around stars with low metallicity (PDF). This isn't the only thing; as metal-poor stars were the first stars to form when the Universe was very young, these two worlds also formed around the same time. They are therefore the most ancient exoplanets discovered to date."

Re:Astronomers are so funny

[Progman3K]

Not to snark at you, but Sol is estimated to be 4-5 billion years old and it's only 8 light-minutes away.
But you've raised a really good question...
Off to read up on it.

Re:Astronomers are so funny

[rubycodez]

time has a very concise and hard definition, much more so than this word "mind" you invoke with your vague and nebulous words. Reality is not an illusion; jump from the roof of a skyscraper to the street, and even though you convince yourself some other event is happening, you will die when from the sudden stop regardless. Reality trumps all, and time is a very real component of reality.

Re:I'm confused

[Michael Woodhams]

Early supernovae wouldn't help - the star is formed from the same material as the planets would, and the star demonstrably has almost no metals. Early supernovae would just mean that this star didn't exist (in its current chemistry), or that it is even younger than currently estimated, so as to form before the supernovae.

Interstellar captures are very difficult. Generally speaking, you need three gravitationally interacting bodies to allow a capture, as you need one to carry away some energy. Basically this requires the wanderer planet to turn up just when the star is passing close to another one, and even then to get really lucky. (Most often it is the lowest mass object of the three which gains energy, but we need the planet to lose energy.) Another possibility is you could lose that energy through tidal losses, but this requires the wanderer has very small positive energy initially, and passes very close to the star. Either way, the odds of such a capture are very low.

In addition, we have the fact that this star has two planets, which makes the odds against capture polynomially* smaller. Finally, if two planets were captured, we'd expect them to have different orbital planes. Given that they were detected by the 'wobble' method, I'd expect this could be measured, and would be mentioned if it had been so. However I can't promise that there aren't gravitational interactions which would bring the orbital planes into alignment over 13Gyr. Captures would also initially have highly elliptical orbits, which again the wobble method should notice, and again I don't know if 13Gyr is long enough to circularize the orbits by tidal effects or planet-planet interactions.

* This word brought to you by the Committee Against The Misuse Of The Word 'Exponentially'

Av shown this page to a non-geeky friend...

[Nrrqshrr]

... And she was delighted. It's really natural for us to think that the universe is that old, and that our vision of it is like lag in an online game. But there is something utterly satisfying when you show this to someone who isn't that much into cosmic timetables and when you watch their reactions as they try to imagine the scale, and their faces when they realise just how meaningless this planet is.
News like this should really become mainstream. This kind of humbling, nihilistic conceptualisation of our lives and surroundings could, ironically, save mankind from whatever foolish suicide we'r preparing to ourselves.

Re:verb tense

[arth1]

So do we say that these planets "are" orbiting HIP 11952, or that they "were" orbiting HIP 11952?

Never mind that this star is in our neighborhood, but you make the mistake of thinking of time as a universal (no pun intended) thing. When the light from a distant star hits us, the star does exist, whether the star is billions of light years away or not. It is meaningless to think that the time that the light traveled has passed, because it hasn't. If you were riding the photons from that star, only a moment would have passed for you.
If we were to go backto the faraway star at the speed of light, we would find it 2*distance older.

Yes, it's difficult to wrap one's head around, so we make up the comfortable lie of considering distant stars being older proportionally to the distance light and radio waves travel as seen from a fixed point. But that point doesn't exist. Time is always subjective, as long as the speed of light in vacuum is considered constant.

And if you thought that makes your head hurt, consider that space itself is expanding, so the distance to a far away star is longer than the distance the light has traveled...

This may be a very bad sign- Great Filter?

[JoshuaZ]

While this discovery is very cool, it may be a very bad sign. One of the most plausible explanations for the Fermi paradox is that intelligent life almost always wipes itself out before it is able to engage in largescale space travel (as so-called Great Filter http://en.wikipedia.org/wiki/Great_filter [wikipedia.org]. One of the other more satisfying explanations is that the sun is one of the first stars to have enough metal to plausibly form planets. That now seems to be less likely. There are other explanations, such as the low metal systems not having enough carbon for life to form and prosper, or that complex life is very rare. However, this discovery potentially removes one of the more plausible possible explanations, and thus makes the possibility of a Great Filter in our future to seem more likely. This is disturbing.

Re:I'm confused

[tibit]

Well said about the capture. It's very interesting to run an N-body gravitational simulation where the initial state is a bunch of things with random masses and velocity vectors. A whole lot of stuff will be ejected as things settle down. Gravitational capture appears to be hard. That's what I learned, to my initial amazement, when I started playing with N-body simulations. I thought the code had bugs. And then I'd input some solar system ephemeris for the planets and a couple other large objects, and voila, it didn't blow up, things were nicely orbiting :)

Re:Can a star really last for 13 billion years ?

[Evil Pete]

Probably a red dwarf. They can fuse hydrogen for ages ... many billions of years. If I recall correctly the luminosity, and hence the lifetime, of a star is proportional to roughly M^3.5 (M is mass) so small mass stars will glow with much greater reduced luminosity and correspondingly much greater lifetime. Just so long as it is hot and dense enough in the core to keep fusion ticking over. This is pretty cool, wonder where the metals came for the planets to form? Is it a freak that picked up stuff from a nearby supernova during formation or what? Wonder if any life arose in that system, would have had a long time to advance by now. Just thinking.