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Author Topic: Alpha Centauri has a planet.  (Read 1453 times)

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Offline VekseidTopic starter

Alpha Centauri has a planet.
« on: October 16, 2012, 08:24:24 PM »
http://www.eso.org/public/news/eso1241/

Quote
European astronomers have discovered a planet with about the mass of the Earth orbiting a star in the Alpha Centauri system — the nearest to Earth. It is also the lightest exoplanet ever discovered around a star like the Sun. The planet was detected using the HARPS instrument on the 3.6-metre telescope at ESO’s La Silla Observatory in Chile. The results will appear online in the journal Nature on 17 October 2012.

Alpha Centauri is one of the brightest stars in the southern skies and is the nearest stellar system to our Solar System — only 4.3 light-years away. It is actually a triple star — a system consisting of two stars similar to the Sun orbiting close to each other, designated Alpha Centauri A and B, and a more distant and faint red component known as Proxima Centauri [1]. Since the nineteenth century astronomers have speculated about planets orbiting these bodies, the closest possible abodes for life beyond the Solar System, but searches of increasing precision had revealed nothing. Until now.

“Our observations extended over more than four years using the HARPS instrument and have revealed a tiny, but real, signal from a planet orbiting Alpha Centauri B every 3.2 days,” says Xavier Dumusque (Geneva Observatory, Switzerland and Centro de Astrofisica da Universidade do Porto, Portugal), lead author of the paper. “It’s an extraordinary discovery and it has pushed our technique to the limit!”

...

Phil Plait (Bad Astronomy) has his own blog here.

http://blogs.discovermagazine.com/badastronomy/2012/10/16/alpha-centauri-has-a-planet/



Easily today's most important event.

It's a bit more massive than Earth, orbiting about .04 AU from the star. Since this means it's not a hot jupiter (which would have been glaringly obvious decades ago), there's a good chance that it missed some terrestrial worlds as it makes its inward spiral into its parent star.

So, Alpha Centauri B may in fact have a star system. And it's highly suggestive that A may have one as well, though I doubt we'd detect it soon. Bigger star, and like our own Sun may have blasted some of the material away from its innermost planet during formation.

Offline Chelemar

Re: Alpha Centauri has a planet.
« Reply #1 on: October 17, 2012, 03:57:26 AM »
Gives one the chills, in both an awesome and yet a kind of spooky kewl way.

Offline TheGlyphstone

Re: Alpha Centauri has a planet.
« Reply #2 on: October 23, 2012, 08:46:53 PM »
Calling Sid Meier, calling Sid Meier...

Offline gaggedLouise

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Re: Alpha Centauri has a planet.
« Reply #3 on: October 24, 2012, 02:10:28 AM »
If we can sparkle he may answer tonight...

 - or at least in nine years time. Yes, very cool. The surface of this particular planet would be hotter than Mercury, but there's nothing excluding that Alpha - or some other star nearby - has a planet that would be more likely to allow for a variety of life. There is life out there, intelligent life too, that's something this particular human has never seen as unlikely in itself.

Offline NotoriusBEN

Re: Alpha Centauri has a planet.
« Reply #4 on: October 25, 2012, 01:01:18 AM »

Offline AllieCat

Re: Alpha Centauri has a planet.
« Reply #5 on: October 26, 2012, 02:26:45 AM »
but does the Alpha Centauri's planet have a Planet? (Video game reference)

Offline Whispered Truths

Re: Alpha Centauri has a planet.
« Reply #6 on: November 07, 2012, 08:03:17 PM »
Seems like it would make a good story about alternate, yet mirroring universes.

Offline gaggedLouise

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Re: Alpha Centauri has a planet.
« Reply #7 on: November 10, 2012, 10:27:23 AM »
A somewhat more promising candidate for an "earth-like" climate or environment (in a very broad sense)

This one is 42 light years away, it's in the "biologically likely belt" around its star and has around seven times the mass of the earth (which would mean it has a little less than twice earth's radius, if we suppose the mean density and makeup of its inner parts are similar) and its mother star is a stable one, some bit less powerful than the sun but not much less strong. The article says "dwarf star", but I reckon that means dwarf in relation to luminous giant stars and not a burnt-out white dwarf - the latter kind would not be able to provide near the amount of heat that would be needed for this kind of planet to be in a "likelihood zone" that would make it possible to expect biological life emerging there.
« Last Edit: November 10, 2012, 10:28:33 AM by gaggedLouise »

Offline VekseidTopic starter

Re: Alpha Centauri has a planet.
« Reply #8 on: November 10, 2012, 11:09:18 AM »
My guess is that many super-Earths in the habitable zone are going to be poseidons by nature.

Offline gaggedLouise

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Re: Alpha Centauri has a planet.
« Reply #9 on: November 10, 2012, 11:21:11 AM »
You mean water planets without land masses? Yes, that sounds likely. The idea of a planet that is entirely or largely composed of water, like Saturn is composed mostly of cold gas, is intriguing.

Offline VekseidTopic starter

Re: Alpha Centauri has a planet.
« Reply #10 on: November 10, 2012, 11:48:31 AM »
Not all water, but Earth's lack of water is actually somewhat unusual.

The bigger a planet is, the more water per unit of surface area is available, and the smaller the surface geographic defects will be (the planet will be flatter). In addition, less hydrogen will escape the planet's atmosphere.


Offline Lux12

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Re: Alpha Centauri has a planet.
« Reply #11 on: November 10, 2012, 10:14:55 PM »
So just how many planets are so consumed by water? I've honestly never heard of these "Poseidon" type planets before.

Offline VekseidTopic starter

Re: Alpha Centauri has a planet.
« Reply #12 on: November 10, 2012, 11:17:24 PM »
No idea.

Earth's primordial ocean was boiled off when Theia impacted the planet and formed the Moon. We don't know how much water that was, or how typical or atypical our situation is. However, it seems strange to assume that a star with sufficient metallicity to form a super-Earth in a habitable zone would lack commiserate ices. I'm sure it happens, but the first guess would be that bigger planet = more primordial water.

Not that that is the entire story. Venus for example, may have had its primordial water blown off during the protostellar phase. So that may be an alternate 'solution' to find a non-Poseidon without a moon.

So the presence of Earth's oceans is determined by several factors.

The first is that our water is water that was trapped inside the planet during accretion, and was slowly driven up over many aeons (there's a paper on this... it was actually calculated with the aid of He3 seepage, which we can safely assume to be primordial when found on Earth, for the most part). This is a volume metric, while the surface area of a planet is naturally an area metric. So bigger planet in habitable zone = deeper oceans.

The second is simply geological activity. While the planet is geologically active, the planet's surface is actually more like a fluid than a solid, if water gets trapped under the surface, it's going to try to boil its way out somehow. Once plate tectonics stops, however, water seeps back beneath the surface of the planet, and just sits there. This is part of why Mars is so dry - lots of water is most assuredly there. A bigger planet, of course, is going to have a more active geology, so the same factor applies.

Planets can also lose water. Occasionally, for innumerable reasons, a water molecule will get sapped, freeing the oxygen of its hydrogen. The smaller the planet, the more likely the hydrogen is to escape. This has had a somewhat meaningful impact on Earth, but the impact on Mars is more drastic. A large enough super-Earth might not ever allow hydrogen to escape in any meaningful quantity, so eventually it re-bonds with free oxygen again.

And then there's simple effects of greater gravity causing larger planets to have smaller features, less water getting tossed off in a giant impact even a-la the moon's formation, or even smaller impacts such as ice comets plowing into the surface.

So taking the above into consideration, even if we're to believe that Earth has more water than average, say, the tendency is going to be bigger planet = more of it covered in water.

Offline Missy

Re: Alpha Centauri has a planet.
« Reply #13 on: November 10, 2012, 11:55:39 PM »
How hard does something have to hit a planetoid for stuff to be cast away from it?

I mean I would assume it would have to hit hard enough that the velocity of stuff being cast upward from the impact would need to attain and sustain an appropriate velocity to counteract the effects of gravity for a minimum period of time.

I suppose hydrogen is a lot lighter though.

Offline VekseidTopic starter

Re: Alpha Centauri has a planet.
« Reply #14 on: November 11, 2012, 12:38:23 AM »
There's an equation for determining the rate of atmospheric loss based on the weight of the molecule (which governs how fast it moves at a given temperature), the escape velocity, and temperature. Earth can't hold onto hydrogen very well at all, and has trouble holding helium. Oxygen, water vapor, neon, etc. are much more likely to remain at normal temperatures.

When hit by something the size of Mars, even rock turns to vapor, and the temperature skyrockets, so lighter molecules are much more likely to escape over the next few thousand years while the surface cools.

Offline Lux12

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Re: Alpha Centauri has a planet.
« Reply #15 on: November 11, 2012, 11:19:29 PM »
Interesting.I knew impacts from other celestial bodies had shaped our planet in many ways, but I had no idea their effect on our geography and the planet's ability to sustain life was quite so vast.You almost make it sound as if we owe our existence to them

Offline gaggedLouise

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Re: Alpha Centauri has a planet.
« Reply #16 on: November 12, 2012, 12:34:25 AM »
Interesting.I knew impacts from other celestial bodies had shaped our planet in many ways, but I had no idea their effect on our geography and the planet's ability to sustain life was quite so vast.You almost make it sound as if we owe our existence to them

The entire planetary system we live in owes its existence to a supernova (or several). Only giant stars will produce heavier elements and only when those stars turn into supernovae* (most stars don't, of course) will they release these elements (metals and also coal, I think) into space, so without supernovae, no solid (rock or mantle) planets and no really advanced life forms, period - not the kind of biology we know from Earth anyway (other planets will likely have other kinds of foundations for their biospheres but it's hard to imagine really major life forms anywhere without some presence of metals, salts and so on in their bodies).

And I remember reading somewhere that astrophysicists now think a major supernova triggered the threshold step from a thin, spread out propto-nebula to the beginning of a true planetary system, as when a liquid crystallizes. We really are the children of the stars.


*Not sure if ordinary novae release any large amounts of heavy elements into space, but don't think so, as those elements are in the core of the star.
« Last Edit: November 12, 2012, 12:40:57 AM by gaggedLouise »

Offline Lux12

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Re: Alpha Centauri has a planet.
« Reply #17 on: November 12, 2012, 02:38:44 AM »
The entire planetary system we live in owes its existence to a supernova (or several). Only giant stars will produce heavier elements and only when those stars turn into supernovae* (most stars don't, of course) will they release these elements (metals and also coal, I think) into space, so without supernovae, no solid (rock or mantle) planets and no really advanced life forms, period - not the kind of biology we know from Earth anyway (other planets will likely have other kinds of foundations for their biospheres but it's hard to imagine really major life forms anywhere without some presence of metals, salts and so on in their bodies).

And I remember reading somewhere that astrophysicists now think a major supernova triggered the threshold step from a thin, spread out propto-nebula to the beginning of a true planetary system, as when a liquid crystallizes. We really are the children of the stars.


*Not sure if ordinary novae release any large amounts of heavy elements into space, but don't think so, as those elements are in the core of the star.

I've heard of this before. I've also heard that they've found amino acids out in space. In nebulas in particular. At least that's what I heard once before.

Offline gaggedLouise

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Re: Alpha Centauri has a planet.
« Reply #18 on: November 12, 2012, 03:00:57 AM »
When the Pistol Star goes off - soon, in astronomical terms - it will likely trigger the formation of many new planetary systems - and possibly kill off a few civilizations and biospheres too - not humanity though, in case we are still around on Earth by then. 

Offline payne

Re: Alpha Centauri has a planet.
« Reply #19 on: November 15, 2012, 07:38:49 PM »
They found my home planet O_o.

No, in all seriousness though, that is so fascinating. I always seem to enjoy stuff like this about planets and space. There probably is life on other planets, even if it is not exactly "intelligent" life.

Offline gaggedLouise

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Re: Alpha Centauri has a planet.
« Reply #20 on: November 16, 2012, 12:43:13 AM »
They found my home planet O_o.

No, in all seriousness though, that is so fascinating. I always seem to enjoy stuff like this about planets and space. There probably is life on other planets, even if it is not exactly "intelligent" life.

"E.T. phone home!"  ;D

I also find the cosmos, and our exploration of it, absolutely fascinating.

Offline NotoriusBEN

Re: Alpha Centauri has a planet.
« Reply #21 on: November 16, 2012, 04:50:44 AM »
The entire planetary system we live in owes its existence to a supernova (or several). Only giant stars will produce heavier elements and only when those stars turn into supernovae* (most stars don't, of course) will they release these elements (metals and also coal, I think) into space, so without supernovae, no solid (rock or mantle) planets and no really advanced life forms, period - not the kind of biology we know from Earth anyway (other planets will likely have other kinds of foundations for their biospheres but it's hard to imagine really major life forms anywhere without some presence of metals, salts and so on in their bodies).

And I remember reading somewhere that astrophysicists now think a major supernova triggered the threshold step from a thin, spread out propto-nebula to the beginning of a true planetary system, as when a liquid crystallizes. We really are the children of the stars.


*Not sure if ordinary novae release any large amounts of heavy elements into space, but don't think so, as those elements are in the core of the star.

your right that coal is released since its all carbon. but I doubt it's what people are thinking of in terms of graphite, shale, oil, and coal that you think of with briquettes. That kind of coal was created by organic material dying off millions of years ago and being subjected to (relatively low) heat and pressure in the earth's surface. Crank both those factors up and it becomes diamonds.


Offline TheGlyphstone

Re: Alpha Centauri has a planet.
« Reply #22 on: November 16, 2012, 11:25:26 AM »
They found my home planet O_o.

No, in all seriousness though, that is so fascinating. I always seem to enjoy stuff like this about planets and space. There probably is life on other planets, even if it is not exactly "intelligent" life.

I like to say that the surest sign intelligent life exists elsewhere in the universe is the fact that none of it has wanted to come visit us.

Offline payne

Re: Alpha Centauri has a planet.
« Reply #23 on: November 16, 2012, 01:42:52 PM »
GaggedLouise XD yup! Sadly, they won't take me back. Something about me being too insane -shrugs-

TheGlyphstone lol that sounds about right. They see us and just keep moving...or they create a reality show out of it like that episode of South Park haha

Offline Lux12

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Re: Alpha Centauri has a planet.
« Reply #24 on: November 16, 2012, 10:32:56 PM »
I like to say that the surest sign intelligent life exists elsewhere in the universe is the fact that none of it has wanted to come visit us.
I could not agree more,