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View Full Version : Earth-Sized Planets Could Be Nearby



Fraser
2006-Jul-24, 04:53 PM
Nearly all of the extrasolar planets discovered so far have been huge, Jupiter-sized and above. The question is: could smaller, Earth-sized planets last in the same star systems? Researchers created a simulation where tiny planets were put into the same system as larger planets to see if they could gather enough material to become as large as the Earth. They found that one nearby system - 55 Cancri - could have formed terrestrial planets, with substantial water in the habitable zone.

Read the full blog entry (http://www.universetoday.com/2006/07/24/earth-sized-planets-could-be-nearby/)

Eckelston
2006-Jul-24, 07:08 PM
Maybe even closer than that? Entry (http://oklo.org/?p=107) from the systemic site (http://oklo.org):


Given what we know about planet formation, itís extremely likely that there are terrestrial planets in orbit around both Alpha Centauri A and Alpha Centauri B. Simulations by Wiegert and Holman (1997) show that the habitable zones of both planets are likely dynamically stable. Elisa Quintana and her collaborators (2002) have carried out accretion calculations that indicate that terrestrial planet formation should proceed very easily around both stars (with 3-5 terrestrial planets expected for each). Because the metallicity of Alpha Centauri is higher than the Sun, the naive expectation is that these planets should contain of order two times as much mass as our own terrestrial planets.

firstcontact
2006-Jul-25, 02:27 PM
"Extrasolar planets have been discovered with increasing frequency in recent years because of techniques that detect giant planets by their gravitational effect on their parent stars. It is uncertain how the giant planets evolve, but they are thought to form far away from their host stars and then migrate inward, pushed by the gas discs from which they formed. If the migration occurs late in the systemís development, the giant planets might destroy most of the materials needed to build Earth-like planets, Raymond said. He noted that while the presence of giant planets is fairly well established, it will be some time before it is possible to detect much smaller Earth-sized planets around other stars."

I have always found it difficult to fathom how these Jupiter size bodies migrate inwards. how does the gas cloud from which thier born push them inward?

mickal555
2006-Jul-26, 08:28 AM
The steady discovery of giant planets orbiting stars other than the Sun has heightened speculation that there could be Earth-type worlds in nearby planetary systems capable of sustaining life.
http://www.spacedaily.com/reports/Model_Finds_Exoplanet_Capable_Of_Supporting_Life_9 99.html

Ronald Brak
2006-Jul-26, 08:51 AM
I don't know if I like this development. I mean if models want to become movie stars or singers, I won't stand in their way, but when models start finding exoplanets then they're starting to muscel in on astronomers turf and it's time to fight back. Perhaps by stocking the observatory fridge with lots of fatty food.

ToSeek
2006-Jul-26, 04:02 PM
ToSeeked by Fraser (http://www.bautforum.com/showthread.php?t=44743)

ToSeeked by Blob (http://www.bautforum.com/showpost.php?p=791557&postcount=4)

eburacum45
2006-Jul-26, 08:32 PM
The idea of an Earth-like planet sandwiched between the giant planets in the 55 Cancri system has been around a few years; it is nice to see a more detailed model that confirms the speculation (to a certain extent).

For instance I wrote a fictional description of this system with just such a planet way back in 2002;
http://www.orionsarm.com/worlds/Danzig.html
as I remember the idea was already current at that time.

PhantomWolf
2006-Jul-27, 02:52 AM
The idea of an Earth-like planet sandwiched between the giant planets in the 55 Cancri system has been around a few years; it is nice to see a more detailed model that confirms the speculation (to a certain extent).

sounds a little like Pitch Black.

eburacum45
2006-Jul-27, 09:11 AM
Actually the outermost gas giant in this system is several AU away, so would appear about as bright than Jupiter in the sky of an Earth-like planet. There would be three brilliant evening stars, though.

ToSeek
2006-Jul-28, 06:54 PM
Just friction, I assume. You keep running into stuff in your orbit, you're going to slow down. Brief writeup here. (http://www.daviddarling.info/encyclopedia/E/epijov.html)

homo_cosmosicus
2006-Aug-01, 04:43 PM
http://www.space.com/scienceastronomy/060801_science_tuesday.html




Only 55 Cancri consistently yielded a world similar in size and orbital distance to Earth. Our planet sits in what's called a habitable zone, just the right distance from the Sun to allow liquid water.

"Our simulations typically produced one terrestrial planet in the habitable zone of 55 Cancri, with a typical mass of about half an Earth mass," said Sean Raymond, a postdoctoral researcher at the University of Colorado who worked on the project while a doctoral student at the University of Washington. "In many of the simulations, these planets accreted a decent amount of water-rich material from farther out in the disk."


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ToSeek
2006-Aug-01, 06:10 PM
Three related threads merged.

Mungascr
2006-Dec-03, 11:03 AM
"Extrasolar planets have been discovered with increasing frequency in recent years because of techniques that detect giant planets by their gravitational effect on their parent stars. It is uncertain how the giant planets evolve, but they are thought to form far away from their host stars and then migrate inward, pushed by the gas discs from which they formed. If the migration occurs late in the systemís development, the giant planets might destroy most of the materials needed to build Earth-like planets, Raymond said. He noted that while the presence of giant planets is fairly well established, it will be some time before it is possible to detect much smaller Earth-sized planets around other stars."

I have always found it difficult to fathom how these Jupiter size bodies migrate inwards. how does the gas cloud from which thier born push them inward?

They migrate inwards because of the gravity of the disk of material from which they form. It also sets up a spiral density wave carved by the motion of the protoplanets in the disk.

Think of giant whirlpool of gravel with large clumps of muddy clay forming and sinking twoards acentral hub or hole as they get larger ...

Take into account too that a star is formed by collapse combine with rotation - stuff is falling together to form the central star(s). Also remember that it takes more energy to move outwards than inwards.

There are many other factors that may or may not come into play such as transfer of spin, T-Tauri wind outbursts, magnetic fields, planetary resonaces and amount of metals and mass available to begin with .. Its a very complicated equation that I think scientists are still struggling to fully understand.

But I hope that helps at least a bit.

publiusr
2006-Dec-22, 06:04 PM
I wonder about dark rogue planets, cast off by supernovae.