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Extrasolar Planets: A Matter of Metallicity
Space Daily, SPX ^ | Oct 12, 2004 | Henry Bortman

Posted on 10/12/2004 12:52:50 PM PDT by tricky_k_1972

Extrasolar Planets: A Matter of Metallicity

by Henry Bortman for Astrobiology Magazine Moffett Field (SPX) Oct 12, 2004

Astronomers have discovered more than 130 planets orbiting nearby stars in our galaxy. Although the solar systems they have found are very different from ours, by studying the planets that have been found - their masses, their orbits and their stars - they are uncovering intriguing hints that our galaxy may be brimming with solar systems like our own.

According to Greg Laughlin, an assistant professor of astronomy and astrophysics at UC Santa Cruz, planet hunters can expect, over time, to find hundreds of nearby stars with Neptune-like planets circling them at about 5 AU. (One AU, or astronomical unit, is the distance between the sun and Earth. Jupiter orbits our sun at about 5 AU.) A solar system with a large planet at 5 AU, astronomers believe, is one in which a habitable terrestrial-sized planet could also safely exist.

Laughlin's prediction comes from studying a characteristic of stars that, until a few years ago, few paid much attention to: metallicity. New stars form when vast clouds of interstellar dust and gas collapse.

This dust and gas is mostly primordial hydrogen and helium, but it also contains a smattering of heavier elements, which astronomers call "metals" (even though non-astronomers don't normally think of all of these elements as metals). The metallicity of a star tells you what portion of its material is made of metals.

And, says Laughlin, "the one true indicator of whether a star is likely to have a detectable giant planet is its metallicity." These hot Jupiters and eccentric Jupiters, as they are known, are the easiest types of planets to detect; almost all the planets discovered to date are of these two types. And "the vast majority of extrasolar planets that are known so far are around metal-rich stars."

Here's why. When a metal-rich interstellar cloud collapses, it forms a metal-rich star. According to the core-accretion theory, the dominant theory of planetary formation, this abundance of heavy material also enables large rocky planetary cores to form relatively quickly, within a few million years.

Once these cores reach 10 Earth masses or more, they begin attracting hydrogen and helium gas from the collapsing cloud; they become gas giants. How big these giants get depends on how much gas they attract.

But the hydrogen and helium don't stick around forever. So timing is critical: only large rocky cores that form before the gas disappears become gas giants. Cores that grow too slowly - the lower the metallicity of the collapsing cloud, the more slowly the cores grow - can't grab any gas.

"If the disk lifetime is 4 million years and it takes you 5 million years to build a core, then you're out of luck," says Laughlin. "But if you can get that core buildup time down to 2.5 million years, say, then there's still plenty of gas available."

Both of these types of planets can be seen in our solar system. "The sun is a metal-rich star, but not dramatically so," Laughlin says. When our solar system was forming, there was enough heavy material around for Jupiter and Saturn to form their cores quickly. They got gas. Neptune and Uranus, however, didn't make it to the starting gate.

There is a strong correlation between high solar metallicity and hot Jupiters. The picture is fuzzier, though, for eccentric Jupiters, planets with elongated elliptical orbits that have been found out to an average distance of about 3 AU from their stars. And it is fuzzier still for planets with orbits like Jupiter's. Planets out at 5 AU take more than a decade to complete their trips around their stars; astronomers have only begun to confirm their presence.

But Laughlin thinks he knows what to expect once all the data are in: lots of Neptune-mass planets, with some as massive as Saturn, in Jupiter-like orbits.

Why Neptunes? Metallicity. The majority of the stars that U.S.-based planet hunters are studying have a bit more than half the metallicity of the sun. That's enough to form a large rocky planet like Neptune. There's no time limit on Neptunes. But it's not enough to form a core quickly; it's not enough to become a gas giant.

So what are the prospects of finding solar systems that contain Earth-like planets? Pretty good, according to Laughlin. The solar systems that have been found so far, the ones that contain hot Jupiters or eccentric Jupiters, probably don't contain habitable Earth-like planets.

The motions of these closer-in giants prevent terrestrial planets from forming stable orbits in the habitable zone. But a solar system with a large planet in a circular orbit at 5 AU - even a Neptune-sized planet - is a solar system in which a habitable Earth-like planet could exist quite comfortably.

Indeed, Laughlin believes that, when all the data are in, we'll have discovered hundreds of nearby stars with solar systems much like our own, although the majority of them will have a Neptune or a Saturn at 5 AU rather than a Jupiter. True, planet hunters haven't found any such planets yet.

But that doesn't mean they're not there. Astronomers just haven't been looking long enough to confirm their presence. With current planet-hunting techniques, Laughlin says, "it's not like you discover a planet - boom!" - in a single observation. "The planets emerge gradually," as a result of many, many observations over time.

So just how long will it take to find such worlds? Well, that's the unfortunate part of the story. Although astronomers have already begun to detect large planets in Jupiter-like orbits, it will take another 10 to 20 years to complete the census of planets orbiting at 5 AU around nearby stars.

"The amount of patience that you have to exercise to get a true Jupiter analog is really enormously more than the amount of patience that you need to find and detect a hot Jupiter or an eccentric giant," Laughlin says. But considering that 10 years ago no-one knew for sure whether there was even a single planet around a star other than our sun, perhaps another 10 or 20 years isn't such a long time to wait.


TOPICS: Culture/Society; Editorial; News/Current Events; Technical
KEYWORDS: xplanets
I think the techniques will continue to improve and we will eventually find likely Eart type planets and this eventually drive our space industry to develop the technology to get there.

Comments?

1 posted on 10/12/2004 12:52:50 PM PDT by tricky_k_1972
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To: Frank_Discussion; unibrowshift9b20; KevinDavis; RightWhale; KarlInOhio; El Sordo; SauronOfMordor; ..

Space Ping!


2 posted on 10/12/2004 12:53:21 PM PDT by tricky_k_1972 (Putting on Tinfoil hat and heading for the bomb shelter.)
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To: tricky_k_1972

I think the day when we get "good" images of these extrasolar planets is a lot closer than we realize. When classrooms have these images on the walls it will spark the minds of the children.

I think actually visiting extrasolar planets is several centuries in the future. On the other hand we could experience great leaps in technology that make it much sooner than we think.


3 posted on 10/12/2004 1:00:47 PM PDT by cripplecreek (The economy won't matter if you're dead.)
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To: longshadow; VadeRetro; balrog666; general_re; RadioAstronomer; js1138; whattajoke; Shryke; ...
Uranus ping list. (If you want on or off this list, don't tell me; let me guess.)
4 posted on 10/12/2004 1:00:59 PM PDT by PatrickHenry (Hic amor, haec patria est.)
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To: tricky_k_1972

Can space ship one make it that far? Gotta call Burt!


5 posted on 10/12/2004 1:01:53 PM PDT by Arkie2
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To: Arkie2

I plan to file a court case stating that Burt's brain must be downloaded into a computer on the grounds it is a National Treasure.


6 posted on 10/12/2004 1:11:54 PM PDT by tricky_k_1972 (Putting on Tinfoil hat and heading for the bomb shelter.)
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To: tricky_k_1972

John Kerry has A Plan to reach out toward the extrasolar planets and bring them back to the table


7 posted on 10/12/2004 1:11:56 PM PDT by NewJerseyJoe (Rat mantra: "Facts are meaningless! You can use facts to prove anything that's even remotely true!")
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To: tricky_k_1972

Does anyone have an idea how many light years away the planets in our solar system could be detected with current technology?


8 posted on 10/12/2004 1:13:10 PM PDT by KarlInOhio (If they couldn't stand up to ...Howard Dean..., how can we expect them to stand up to Al Queda?)
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To: Owl_Eagle; Mr. Mojo; Mudboy Slim
Extrasolar Planets: A Matter of Metallicity

Metallica really needs to get back to simple album titles or nicknames, like the "Black Album." This "Extrasolar" thing is going to really turn off the kids!

9 posted on 10/12/2004 1:14:41 PM PDT by HenryLeeII ("I own a lumber company? Didn't know that. ... ... Want some wood?" -GWB, Oct. 8, 2004)
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To: KarlInOhio; RadioAstronomer

Interesting question. I suggest you ask RadioAstronomer.


10 posted on 10/12/2004 1:15:18 PM PDT by tricky_k_1972 (Putting on Tinfoil hat and heading for the bomb shelter.)
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To: NewJerseyJoe
"John Kerry has A Plan to reach out toward the extrasolar planets and bring them back to the table"

Use of American military power must pass the Universal test.

11 posted on 10/12/2004 1:19:19 PM PDT by DannyTN
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To: tricky_k_1972

Silly me, I thought Neptune and Uranus where gas giants. Good thing this article set me straight </sarcasm>


12 posted on 10/12/2004 1:19:32 PM PDT by SengirV
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To: tricky_k_1972

When we do find an earth-like planet, let's ship all the liberals there!

Seriously, I sometimes wonder if there are some beings on a planet 100 lightyears away wondering if there's someone else out there.


13 posted on 10/12/2004 1:26:17 PM PDT by RockinRight (John Kerry is the wrong candidate, for the wrong country, at the wrong time)
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To: SengirV

Michael Moore is a gas giant.


14 posted on 10/12/2004 1:26:45 PM PDT by NewJerseyJoe (Rat mantra: "Facts are meaningless! You can use facts to prove anything that's even remotely true!")
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To: HenryLeeII

Actually, I think that would make a great album title!


15 posted on 10/12/2004 1:26:59 PM PDT by RockinRight (John Kerry is the wrong candidate, for the wrong country, at the wrong time)
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To: HenryLeeII

16 posted on 10/12/2004 1:28:06 PM PDT by fishtank
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To: RockinRight
> When we do find an earth-like planet, let's ship all the liberals there!

I must forcefully disagree! We should ship the liberals to harsh, inhospitable planets.

17 posted on 10/12/2004 1:28:18 PM PDT by NewJerseyJoe (Rat mantra: "Facts are meaningless! You can use facts to prove anything that's even remotely true!")
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To: tricky_k_1972; cripplecreek; PatrickHenry
I think I will mention Joss Whedon's vision of the future with the evil Alliance (when the U.S. and China merge) enforcing a "union" and subjugation of all inhabited planets -- when the lost hopes and dreams of the Independents (after their defeat at Serenity Valley on the planet Hera) are summed up in a small spaceship called Firefly.

Keep flyin'

18 posted on 10/12/2004 1:59:30 PM PDT by Siobhan (Work and pray to stop John Kerry.)
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To: HenryLeeII
"Metallica really needs to get back to simple album titles or nicknames, like the "Black Album."

LOL...MUD

19 posted on 10/12/2004 2:09:30 PM PDT by Mudboy Slim (Girleymen HATE Bush!!)
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To: KarlInOhio
John Kerry has A Plan to reach out toward the extrasolar planets and bring them back to the table

I think he called it "Plan 9".

20 posted on 10/12/2004 2:12:36 PM PDT by Spirochete
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To: tricky_k_1972

"hot Jupiters"

John Kerry has a plan to cool those planets down by enlisting the aid of the Intergalactic Council, most of whom support him for president.


21 posted on 10/12/2004 2:13:46 PM PDT by Larry Lucido
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To: PatrickHenry

add to ping list, please.


22 posted on 10/12/2004 2:18:14 PM PDT by Drammach (Freedom; not just a job, it's an adventure..)
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To: tricky_k_1972

IMO, it all depends on whether islam wins or islam loses. If islam wins, we won't be advancing much further and we'll go straight back to the Dark Ages, never to emerge from that darkness again.


23 posted on 10/12/2004 2:36:56 PM PDT by LibWhacker
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To: NewJerseyJoe
We should ship the liberals to harsh, inhospitable planets.

Personally, I'd just as soon leave them here, while we boldly go forth to plant the seeds of the American culture of liberty on the new worlds.

It's a win-win proposition. They will be more than happy to see us go, and we'll be more than happy to leave them to their own totalitarian socialist devices.

And won't their descendants be surprised, when 1000 years or so into the New Dark Ages (otherwise known as the "Radiant Socialist Future" LOL), our descendants return to the mother world in what will seem to the inhabitants of old Earth to be "magical fiery chariots".

I wonder if our descendants will take pity on the stay-at-homes living in the filth and squalor of a depleted world, and help them out. (Hopefully NOT)

Heh heh. I'm getting away from myself - this idea is actually the basis for a series of science fiction short stories I'm in the process of creating right now. Some of the fundamental details are different, but it's the gist of it.

24 posted on 10/12/2004 5:55:02 PM PDT by FierceDraka ("Support John Kerry - Or ELSE!" - The New Slogan of the Democratic Party)
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To: Tax-chick

later


25 posted on 10/12/2004 6:44:10 PM PDT by Tax-chick (If you stand very still, they may think you're a tree.)
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To: RightWhale; Brett66; xrp; gdc314; sionnsar; anymouse; RadioAstronomer; NonZeroSum; jimkress; ...
It is a matter of time that we find an Earth like planet..


26 posted on 10/12/2004 6:53:57 PM PDT by KevinDavis (Let the meek inherit the Earth, the rest of us will explore the stars!)
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To: SengirV
Someone mention gas giants?


27 posted on 10/12/2004 9:16:33 PM PDT by LibertarianInExile (The Fourth Estate is the Fifth Column.)
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To: KevinDavis
According to Big Bang theory we can see about 10-30 of the entire universe if we look all the way back 13.5 billion years to the Big Bang. That means there would be 1050 stars in the entire universe, most of which we can not see or interact with. That is about the root of a googol of stars, and probably also an equal number of planets.
28 posted on 10/13/2004 7:13:23 AM PDT by RightWhale (Withdraw from the 1967 UN Outer Space Treaty and establish property rights)
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To: tricky_k_1972; balrog666; PatrickHenry
Thought you and your ping lists might like to see this:
Did Our Sun Capture Alien Worlds?
It's a Univ. of Utah press release regarding this week's Nature Mag. article on the same. There's a link in this to the Smithsonian/Harvard Astrophysics press release on the same.

I don't know anything about it other than it's my brother's work, which I'll never understand... Thought you'd know what to make of it and who to show it to.

Regards,
Nicollo

29 posted on 12/01/2004 12:39:04 PM PST by nicollo
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To: KevinDavis

Pinging you to post no. 29.


30 posted on 12/01/2004 12:42:09 PM PST by nicollo
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To: tricky_k_1972

130 is a lot of planets considering that a decade ago there were about none. There are another 100 that have been detected even more indirectly. There could be a trillion in this galaxy, easily.


31 posted on 12/01/2004 12:44:34 PM PST by RightWhale (Destroy the dark; restore the light)
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To: RockinRight
When we do find an earth-like planet, let's ship all the liberals there!

Why not just send them to the Sun?
That more closely mirrors where many on this forum think liberals will go.

32 posted on 12/01/2004 12:56:45 PM PST by ASA Vet (Be very very quiet, I'm hunting for the rascally ... troll)
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To: nicollo; RadioAstronomer; longshadow; VadeRetro

Interesting. Maybe someone will post it as the lead article in a stand-alone thread. I'd do it, but I don't have the time right now.


33 posted on 12/01/2004 1:01:41 PM PST by PatrickHenry (The List-O-Links for evolution threads is at my freeper homepage.)
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this is from late 2004:
X-Planets FR 'blog

34 posted on 06/29/2006 12:23:37 AM PDT by SunkenCiv (updated my FR profile on Wednesday, June 21, 2006.)
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To: tricky_k_1972

Still sounds like our type of Solar System would be rare.


35 posted on 06/29/2006 12:51:57 AM PDT by Moonman62 (The issue of whether cheap labor makes America great should have been settled by the Civil War.)
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X-Planets
· join · view topics · view or post blog · bookmark · post new topic ·

36 posted on 06/18/2007 2:01:57 AM PDT by SunkenCiv (Time heals all wounds, particularly when they're not yours. Profile updated June 15, 2007.)
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http://www.freerepublic.com/focus/f-chat/1507383/posts?page=17#17


37 posted on 06/18/2007 2:17:51 AM PDT by SunkenCiv (Time heals all wounds, particularly when they're not yours. Profile updated June 15, 2007.)
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