13-Billion-Year-Old Alien Worlds Discovered 302
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 (Score:5, Informative)
Re:Can a star really last for 13 billion years ? (Score:4, Informative)
http://en.wikipedia.org/wiki/Red_dwarf#Description_and_characteristics
It's possible to have stars that can fuse material for as long as 10 trillion years. Yes, T-T-T-Trillion.
The articles I looked at regarding this planet though make no mention to what class of star they're orbiting, so YMMV.
Re:Can a star really last for 13 billion years ? (Score:5, Informative)
Can a star really last for 13-billion year and not running out of fuel?
Yes. Our own star is about 5 billion years, and probably only halfway through its life cycle.
Just like with dogs, the smaller ones live longer. Red dwarfs are expected to live for thousands of times the current age of the universe, and simply peter out as they exhaust their fuel, burning it slower and slower, but never having the gravity to cause helium fusion.
Re:Astronomers are so funny (Score:5, Informative)
Actually, it's unknown what it was like before the big bang.
Like the parent said, time itself did not exist until the big bang, therefor, there is no "before" the big bang. There is no such thing as before time, just as there is no such thing as negative mass or negative distance.
Re:maybe they dont exist (Score:4, Informative)
They're only 375 light years away.
Re:Astronomers are so funny (Score:4, Informative)
http://en.wikipedia.org/wiki/Main_sequence [wikipedia.org]
They can guesstimate the age of a star based on its light characteristics. Our current understanding is that stars tend to follow a set progression through their evolution, and by looking at the current characteristics of a star (mass, heat, spectral composition), they can guess roughly how old it is.
It's all guesswork, mind you, and it doesn't necessarily tell us that the planets themselves are as old as the star. They could be trapped planets from other solar systems that the stars came into contact with over the years, or even trapped proto-stars that never had enough mass to start fusion... current thinking is that the interstellar medium may have a lot of this type of planet.
Re:Astronomers are so funny (Score:5, Informative)
Didn't get one thing: the article says the star is 13 billions yo, but it's 375 ly from our solar system.
I always have thought that distance meant age. Which other technique there is to tell a star's age?
Distance is... well, distance. The number of light years something is away means that we are looking at what happened that many years ago. In this case, what we see happened 375 years ago. It has nothing to do with the age of the object. However, if we see a galaxy 13 billion light years away, we know that the galaxy is 13 billion years old since nothing is that much older, provided it still exists. We don't really know as we would be seeing it as it existed 13 billion years ago. To see how it looks today, we'll have to wait another 13+ billion years and look at it again.
As for judging the age of a star, I'll take a stab at it, although IANAA. If I recall correctly, there are several methods used to judge the age of a star. We know by looking at what the star is composed of which developmental stage it is currently at. We know by its size and energy output how fast it is burning its fuel. So, if we see a large, bright, hydrogen star, we know that it is fairly young since large hydrogen stars don't last long. We can be more accurate by figuring out how fast it burns its fuel and how much it has left (helium to hydrogen ratio). If we see that it is composed mostly of helium, we know that it is in its second stage. We can judge by its size how long it was in its hydrogen stage before it fused it all to helium.
I have not RTFA, but I believe they are judging that this star was one of the first out of gate judging by how much metal it has in its core, meaning that it is very, very old.
Take with salt. Like I said, I'm no astrophysicist.
What I don't understand is how do the scientist know that these were not rogue planets, formed much later and then became trapped by the star's gravity. Just because a star has planets orbiting it, doesn't mean that those planets formed along with the star.
Re:Astronomers are so funny (Score:5, Informative)
13.75 +/- 0.11 billion years
(The same age [wikipedia.org] as the universe)
Re:Can a star really last for 13 billion years ? (Score:4, Informative)
Lifetime=1/Mass^2.5.
Note that lifetime here is as a ratio of solar lifetime (so a Lifetime of 1=10 billion years) and mass is in solar masses. The paper gives the mass of HIP 11952 as about 0.83 solar masses, so an estimated main sequence lifetime would be 1/0.83^2.5= 15.9 billion years, after which it would become a red giant. Not liking the odds for its planets at that time, especially the one with a 7 day orbital period. So, it probably has a long while left, though there are wide bounds listed for mass and age, so if it is actually older and heavier, it might be living on borrowed time.
Re:Can a star really last for 13 billion years ? (Score:4, Informative)
It's possible to have stars that can fuse material for as long as 10 trillion years. Yes, T-T-T-Trillion.
10-100 short scale (U.S.) trillion, or 10-100 long scale (Euro) billion. A pretty long time, yes, considering that the universe is considered[*] to be less than 14 billion (short scale) / 14 milliard (long scale) / 14 thousand million (UK) years old.
[*]: It's hard to say with any certainty, because once you get really close to the Big Bang, time will have acted very strange from our perceptive, and what might have been a millisecond in one part of the small budding universe might have been a millions of years in another part.
Re:Alien mystery worlds... (Score:4, Informative)
Orbital dynamics and mr. Occam must be at odds today. Play with an N-body simulator and see how it goes. I don't think most people can claim any sort of common sense here unless they've been playing with one. It usually doesn't work the way one would expect. For example, one could naively think that gravity, as an attractive force, will cause eventual collapse if you start simulation with a random bunch of bodies having 0 relative velocity. To one's surprise, then, not only there will be no collapse, but a bunch of objects will get permanently ejected from such a system. Getting things cleanly orbiting one another in low-eccentricity orbits can be considered a lucky occurrence as well. That's what I remember from when I was in high school -- that's the first and last time I felt like coding up N-body (it's a pain -- naive algorithms don't work if you've not got a couple centuries to wait for the results), so feel free to correct me if I'm wrong.
Re:Astronomers are so funny (Score:5, Informative)
It is difficult for a body not already in orbit around a star to be captured by it unless there is a third body or something else (dust cloud, etc.) nearby to take away some of the kinetic/potential energy involved. If there is no third body then by a conservation of energy argument -- the small body falls toward the star, faster as it gets closer then slingshots around and back into interstellar space. Even if there are "third bodies" around it is just as likely they will transfer energy to the interstellar visitor and send it out with more speed than it came in with. Similar thing happens with the solar system comets -- they are technically in orbit around the sun way, way out there but occasionally one gets perturbed and comes in close -- unless it gets further perturbed by a planet it will fly a practically parabolic trajectory and go right back out to the far edges of the solar system.
Re:Astronomers are so funny (Score:4, Informative)
http://en.wikipedia.org/wiki/Shape_of_the_universe [wikipedia.org] :
The Wilkinson Microwave Anisotropy Probe (WMAP) has confirmed that the universe is flat with only a 0.5% margin of error.[1] Within the Friedmann-Lemaître-Robertson-Walker (FLRW) model, the presently most popular shape of the Universe found to fit observational data according to cosmologists is the infinite flat model,[2] while other FLRW models that fit the data include the Poincaré dodecahedral space[3][4] and the Picard horn.[5]
Re:Astronomers are so funny (Score:5, Informative)