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mithridates
Joined: 03 Mar 2003
Location: President's office, Korean Space Agency
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 Posted: Fri Sep 30, 2005 11:39 pm Post subject: Finding another Earth |
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You see headlines like this all the time:
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Six new planets reported
August 30, 2005
(PLANETQUEST) -- Scientists announced the discoveries of six new extrasolar planets during the latter half of August, found at distances ranging from 20 to 289 light-years from Earth, according to information posted on the Extrasolar Planets Encyclopedia website.
The largest is about 1.6 times as massive as Jupiter. The smallest is about as massive as Uranus, or about 14 times the mass of Earth. The planets orbit their parent stars at distances ranging from 10 million to 3 million miles (16 million to 5 million kilometers) -- much closer than the distance at which Mercury orbits our sun.
The new planets are described in papers submitted to the European journal Astronomy and Astrophysics. More details on these discoveries will be reported on this site as they become available. |
That's a new planet every two or three days. Over at the Keck Observatory they have a new technique that will be refined over the next year or so whereby they can block out the light from a star to see the planets orbiting it, so in two years' time we'll be able to see them directly.
I'm thinking that in the next decade we'll have discovered a few thousand Earth-sized planets in other solar systems, some not too far from here.
Will that cause any large shift in people's consciousness / way of thinking when all these planets are discovered? What if the nearest star system (Alpha Centauri) turns out to have one or more Earth-like planets? |
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mithridates
Joined: 03 Mar 2003
Location: President's office, Korean Space Agency
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| Posted: Fri Sep 30, 2005 11:43 pm Post subject: |
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| Computer models of planetary formation suggest that terrestrial planets would be able to form close to both Alpha Centauri A and B, but that gas giant planets similar to our Jupiter and Saturn would not be able to form because of the binary stars' gravitational effects. Given the similarities in star type, age and stability of the orbits it has been suggested that this solar system may hold one of the best possibilities for extraterrestrial life. However, some astronomers have speculated that any terrestrial planets in the Alpha Centauri system may be dry because it is believed that Jupiter and Saturn were crucial at directing comets into the inner solar system and providing the inner planets with a source of water. This would not be a problem, however, if Alpha Centauri B happened to play a similar role. |
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mithridates
Joined: 03 Mar 2003
Location: President's office, Korean Space Agency
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| Posted: Fri Sep 30, 2005 11:59 pm Post subject: |
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Alpha Centauri is a special place, because it may offer life conditions similar to our solar system. A star must pass five tests before we can call it a promising place for terrestrial life as we know it. Most stars in the Galaxy would fail. In the case of Alpha Centauri, however, we see that Alpha Centauri A passes all five tests, Alpha Centauri B passes either all but one, and only Proxima Centauri flunks out.
The first criterion is to ensure a star's maturity and stability, which means it has to be on the main sequence. Main-sequence stars fuse hydrogen into helium at their cores, generating light and heat. Because hydrogen is so abundant in stars, most of them stay on the main sequence a long time, giving life a chance to evolve. The Sun and all three components of Alpha Centauri pass this test.
The second test is much tougher, however, we want the star to have the right spectral type, because this determines how much energy a star emits. The hotter stars - those with spectral types O, B, A, and early F - are no good because they burn out fast and die quickly. The cooler stars - those with spectral types M and late K - may not produce enough energy to sustain life, for instance they may not permit the existance of liquid water on their planets. Between the stars that are too hot and those that are too cool, we find the stars that are just right. As our existance proves, yellow G-type stars like the Sun can give rise to life. Late (cool) F stars and early (hot) K stars may be fine too. Luckily, Alpha Centauri A passes this test with bravour, as it is of the same class as our Sun. Alpha Centauri B is a K1 star, so it is hotter and brighter than most K stars, therefore it may pass this test or it may not. And the red dwarf Proxima Centauri seems to be a hopeless case.
For the third test, a system must demonstrate stable conditions. The star's brightness must not vary so much that the star would alternately freeze and fry any life that does manage to develop around it. But because Alpha Centauri A and B form a binary pair there's a further issue. How much does the light received by the planets of one star vary as the other star revolves around it ? During their 80-year orbit, the separation between A and B changes from 11 AU to 35 AU. As viewed from the planets of one star, the brightness of the other increases as the stars approach and decreases as the stars recede. Fortunately, the variation is too small to matter, and Alpha Centauri A and B pass this test. However, Proxima fails this test, too. Like many red dwarfs it is a flare star, prone to outbursts that cause its light to double or triple in just a few minutes.
The fourth condition concerns the stars' ages. The Sun is about 4.6 billion years old, so on Earth life had enough time to develop. A star must be old enough to give life a chance to evolve. Remarkably, Alpha Centauri A and B are even older than the Sun, they have an age of 5 to 6 billion years, therefore they pass this test with glamour, too. Proxima, however, may be only a billion years or so old, then it fails this test, too.
And the fifth and final test: Do the stars have enough heavy elements - such as carbon, nitrogen, oxygen and iron - that biological life needs ? Like most stars, the Sun is primarily hydrogen and helium, but 2 percent of the Sun's weight is metals. (Astronomers call all elements heavier than helium "metals".) Although 2 percent may not sound a lot, it is enough to build rocky planets and to give rise to us. And again, fortunately, Alpha Centauri A and B pass this test. They are metal-rich stars.
Now to the final question. Do we find at Alpha Centauri warm, rocky planets like Earth, full of liquid water ? Unfortunately, we don't know yet whether Alpha Centauri even has planets or not. What we know is that in a binary system the planets must not be too far away from a particular star, or else their orbits become unstable. If the distance exceeds about one fifth of the closest approach of the two stars then the second member of the binary star fatally disturbes the orbit of the planet. For the binary Alpha Centauri A and B, their closest approach is 11 AU, so the limit for planetary orbits is at about 2 astronomical units. Comparing with our system, we see that both Alpha Centauri A and B might hold four inner planets like we have Mercury (0.4 AU), Venus (0.7 AU), Earth (1 AU) and Mars (1.5 AU). Therefore, both Alpha Centauri A and B might have one or two planets in the life zone where liquid water is possible. |
A distance of 11 - 80 AU is a bit further out than Saturn at closest approach, and twice as far away as Pluto at its greatest extent. |
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mithridates
Joined: 03 Mar 2003
Location: President's office, Korean Space Agency
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| Posted: Sat Oct 01, 2005 11:37 am Post subject: |
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| Wow, this is fascinating! I just hope this thread doesn't get out of control. |
Yeah, me too. You know how these space threads can sometimes get though. Something about the subject just makes everyone want to type something, and before you know it you're at page 15. |
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Leslie Cheswyck
Joined: 31 May 2003
Location: University of Western Chile
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| Posted: Sun Oct 02, 2005 1:45 am Post subject: |
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| Alpha Centauri is OURS! |
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rapier
Joined: 16 Feb 2003
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| Posted: Sun Oct 02, 2005 2:22 am Post subject: |
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We will need to desert this planet soon. But i don't think we'll get the time to find a new one.
Earth, 2030.
Out of control fires ravage a hotter and dimmer planet.
A little later:
earth is an inferno and a team of astronauts have escaped earth to cruise the galaxy looking for somewhere to live.
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EFLtrainer
Joined: 04 May 2005
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| Posted: Sun Oct 02, 2005 12:41 pm Post subject: |
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| M'thinks we shall be about terraforming or building space stations on Mars and Luna long before we seriously think about colonizing other star systems. After all, before the Sun goes the way of the Dodo it'll fry the Earth but then Mars will be as temperate as Earth is now. So, we've got quite a lot of time before we need to move on. Some billions of years, I'd think. |
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marlow
Joined: 06 Feb 2005
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| Posted: Sun Oct 02, 2005 3:40 pm Post subject: |
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Humans can't create fully functioning ecosystems yet. The Biosphere projects were failures.
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Finding new planets is of scientific interest, and if our space programs were more extensive, it would be of practical importance. |
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EFLtrainer
Joined: 04 May 2005
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| Posted: Sun Oct 02, 2005 3:46 pm Post subject: |
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| marlow wrote: |
Humans can't create fully functioning ecosystems yet. The Biosphere projects were failures.
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Finding new planets is of scientific interest, and if our space programs were more extensive, it would be of practical importance. |
Not really talking about today. |
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marlow
Joined: 06 Feb 2005
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| Posted: Sun Oct 02, 2005 4:07 pm Post subject: |
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| EFLtrainer wrote: |
| marlow wrote: |
Humans can't create fully functioning ecosystems yet. The Biosphere projects were failures.
....
Finding new planets is of scientific interest, and if our space programs were more extensive, it would be of practical importance. |
Not really talking about today. |
I was making general comments not necessarily directed at yours.
I certainly hope that we can master those technologies, and I assume we will in the distant future, but we must protect our planet, and not think of these technologies as viable near future escape routes. |
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igotthisguitar
Joined: 08 Apr 2003
Location: South Korea (Permanent Vacation)
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| Posted: Mon Oct 03, 2005 3:36 am Post subject: |
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Provided we're not forced to believe it's another FLAT orb i suppose the discovery of Earth_2 might be ok.
Just think of the scope of death & destruction we could wage down here before seeking to escape to the next distant planet ... out there. |
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Manner of Speaking
Joined: 09 Jan 2003
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| Posted: Mon Oct 03, 2005 3:46 am Post subject: Re: Finding another Earth |
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| mithridates wrote: |
You see headlines like this all the time:
| Quote: |
Six new planets reported
August 30, 2005
(PLANETQUEST) -- Scientists announced the discoveries of six new extrasolar planets during the latter half of August, found at distances ranging from 20 to 289 light-years from Earth, according to information posted on the Extrasolar Planets Encyclopedia website.
The largest is about 1.6 times as massive as Jupiter. The smallest is about as massive as Uranus, or about 14 times the mass of Earth. The planets orbit their parent stars at distances ranging from 10 million to 3 million miles (16 million to 5 million kilometers) -- much closer than the distance at which Mercury orbits our sun.
The new planets are described in papers submitted to the European journal Astronomy and Astrophysics. More details on these discoveries will be reported on this site as they become available. |
That's a new planet every two or three days. Over at the Keck Observatory they have a new technique that will be refined over the next year or so whereby they can block out the light from a star to see the planets orbiting it, so in two years' time we'll be able to see them directly.
I'm thinking that in the next decade we'll have discovered a few thousand Earth-sized planets in other solar systems, some not too far from here.
Will that cause any large shift in people's consciousness / way of thinking when all these planets are discovered? What if the nearest star system (Alpha Centauri) turns out to have one or more Earth-like planets? |
It sure seems to be a Golden Age for Planetary Astronomy, doesn't it? The discovery of KPOs and possible Oort Cloud objects, and the discovery of +150 planets in other solar systems is changing our whole conception of the solar system(s).
I'd be interested in knowing how different the emission spectra of Alpha Centuri A & B are from the Sun; it could have some influence on the possibilities for life in those solar systems. Too much gamma radiation would be nasty. |
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mithridates
Joined: 03 Mar 2003
Location: President's office, Korean Space Agency
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| Posted: Mon Oct 03, 2005 7:36 am Post subject: |
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| I'm quite sure it wouldn't be a problem. Alpha Centauri A is a G2 V star just like the sun, and only a bit bigger. The other one is K1 V which makes it a little smaller. They're both stable too and don't come close enough to each other to disrupt anything within 2 AU or so, which means that there would be no outlying gas giants but Earth-like planets would certainly be possible. The only question is whether they would have water because gas giants bring in comets all the time for that during the creation of a solar system. The second star might have done that though, who knows. And the third star is way too far out and way too dim to be in the equation; it's a few thousand AU out and you can't even see it from the other two stars...unless the night is really dark. I think. |
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jinglejangle
Joined: 19 Feb 2005
Location: Far far far away.
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| Posted: Mon Oct 03, 2005 2:56 pm Post subject: |
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| mithridates wrote: |
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| Wow, this is fascinating! I just hope this thread doesn't get out of control. |
Yeah, me too. You know how these space threads can sometimes get though. Something about the subject just makes everyone want to type something, and before you know it you're at page 15. |
Here's a question for you though.
Are they still speculating about a planet x in our own solar system based on observed gravitational anomalies with regards to other solar bodies?
Does my last sentance make any sense?
And, if they are still speculating, (they=serious astronomers who we should respect) why can we find all these planets in other systems and not in our own? |
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jinglejangle
Joined: 19 Feb 2005
Location: Far far far away.
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| Posted: Mon Oct 03, 2005 3:02 pm Post subject: |
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| EFLtrainer wrote: |
| M'thinks we shall be about terraforming or building space stations on Mars and Luna long before we seriously think about colonizing other star systems. |
As it happens, NASA currently has a program in the works to put a permanent base on the moon. I wonder if it isn't being spurred on by the development of the chinese space progrm, but anyway....
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Before the end of the next decade, NASA astronauts will again explore the surface of the moon. And this time, we're going to stay, building outposts and paving the way for eventual journeys to Mars and beyond. There are echoes of the iconic images of the past, but it won't be your grandfather's moon shot.....
......Once a lunar outpost is established, crews could remain on the lunar surface for up to six months. The spacecraft can also operate without a crew in lunar orbit, eliminating the need for one astronaut to stay behind while others explore the surface. |
http://www.nasa.gov/missions/solarsystem/cev.html
Thanks to Mith for getting me just enough interested in space travel to have read that article, thereby enabling me to post here sounding like I know something.
You can all expect that this will be my last worthwhile contribution to this thread however, as I have just shared with you pretty much my entire knowledge base regarding current NASA projects. |
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