Posted on 02/02/2006 9:44:25 AM PST by SunkenCiv
Meanwhile, the Doppler discovery of extrasolar planets orbiting very close to their parent stars has raised a different problem. Many of the planets are so close to their stars (<0.1 AU), and so hot, that they cannot be supposed to have formed where we now observe them. By inference, they could have formed at larger distances (several AU) and then migrated inwards. What would cause this inward migration? As with the solar system case, the root cause may be an exchange of angular momentum with material surrounding the planets at their formation. In particular, if the extrasolar planets formed in massive disks, then torques between the planets and the disks could drive the former inwards.
Aha, you say, why did they stop? There are several possible answers to this question (including the most brutally honest one "we don't know"). Indeed, they might not have stopped, in the sense that the observed close-in extrasolar planets could be the survivors from a now-defunct armada of planets that plopped into their stars never to be seen again. In this case, what we see is what was left behind after the planetary accretion disk dissipated and the tidal torques disappeared. Another possibility is that inward migration stopped when the planets reached the inner edge of the planetary accretion disk, because then the torques acting to propel them inwards would vanish.
(Excerpt) Read more at ifa.hawaii.edu ...
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Scientists Find Extrasolar Planet With Atmosphere Much Like Jupiter[T]he planet is so close to the searing heat of its parent star that the dense atmosphere reaches temperatures of about 18,000 degrees Fahrenheit and is boiling off and evaporating at a rate of perhaps 10,000 tons a second. The escaping hydrogen was detected extending across 125,000 miles, trailing the planet like a comet's tail. The scientists said analysis of the observations showed that hydrogen atoms in the extended atmosphere had large velocities relative to the planet. Thus, they concluded, the hydrogen "must be escaping the planetary atmosphere." As a result, astronomers said, the planet may already have lost a considerable amount of its mass. Much of it may eventually disappear, leaving only a dense core about 10 times the mass of Earth... This particular planet -- with a diameter 1.3 times that of Jupiter, and two-thirds its mass -- orbits its star at a distance of only four million miles, so close that it makes a complete circuit every 3.5 days. By comparison, Mercury, the planet closest to the Sun, orbits at a distance of 36 million miles, completing the orbit in 88 days.
by John Noble Wilford
March 13, 2003
NYTimes
Newfound Planetary System Has 'Hometown' LookDr. Geoffrey Marcy, astronomy professor at the University of California, Berkeley, and astronomer Dr. Paul Butler of the Carnegie Institution of Washington, Washington, D.C., today announced the discovery of a Jupiter-like planet orbiting a Sun-like star at nearly the same distance as the Jovian system orbits our Sun.
NASA
June 13, 2002
55 Cancri simulation
55 Cancri comparisonJupiter-Like Planet Could Point to Another EarthThe primary discovery is a gas giant planet that circles a star called 55 Cancri every 13 years, comparable to Jupiter's 11.86-year orbit. The planet is between 3.5 and 5 times as heavy as Jupiter... The new planet orbits 55 Cancri at 5.5 astronomical units (AU). One AU is the distance from Earth to the Sun. Jupiter orbits at 5.2 AU. The same team had already spotted another planet around 55 Cancri, a place slightly less massive than Jupiter. It orbits so close to the star that it makes a complete orbit in just 14.6 days.
by Robert Roy Britt
13 June 2002
Rogue Planet Find Makes Astronomers Ponder TheoryEighteen rogue planets that seem to have broken all the rules about being born from a central, controlling sun may force a rethink about how planets form, astronomers said on Thursday... "The formation of young, free-floating, planetary-mass objects like these is difficult to explain by our current models of how planets form," Zapatero-Osorio said... They are not linked to one another in an orbit, but do move together as a cluster, she said... Many stars in our own galaxy, the Milky Way, may have formed in a similar manner to the Orion stars, she said. So there could be similar, hard-to-see planets floating around free near the Solar System.
by Maggie Fox
October 5, 2000
Building Planets in Record TimeWhile the problem of hot Jupiters has yet to be resolved, Quinn and his colleagues may have sorted out the discrepancy between disk lifetimes and the timescale of planet formation. Using complex computer models, this team showed that protoplanetary disks begin to fragment after just a few rotations -- after just about 350 years -- and these fragments build up into planets. If two clumps of material have similar orbits they eventually collide and form a larger planet.
by Pamela L. Gay
12/02/2002
A Family of GiantsUpsilon Andromedae is a bright star that is visible to the naked eye from the Northern Hemisphere, starting roughly in June. It is located about 44 light-years from Earth, and is roughly 3 billion years old, about two-thirds the age of the Sun.
American Astronomical Society
and San Francisco State University
Apr. 15, 1999
The innermost (and previously known) of the three planets contains at least three-quarters of the mass of Jupiter and orbits only 0.06 AU (8.9 million km) from the star... It traverses a circular orbit every 4.6 days. The middle planet contains at least twice the mass of Jupiter and takes 242 days to orbit the star once. It resides approximately 0.83 AU from the star, similar to the orbital distance of Venus. The outermost planet has a mass of at least four Jupiters, and completes one orbit every 3.5 to 4 years, placing it 2.5 AU from the star. The two outer planets are both new discoveries and have elliptical orbits, a characteristic of the nine other extrasolar planets in distant orbits around their stars.
No current theory predicted that so many giant worlds would form around a star... A computer simulation by Greg Laughlin of U.C. Berkeley suggest that these three giant planets could co-exist in stable orbits. One big question left to answer is how such a solar system arose... [T]hese observations cannot rule-out Earth-sized planets, as their signature would be too weak to detect with current instrumentation.
The ONLY thing that puzzles me about this behavior is how scientists can think there is anything abnormal about this. Theings are constantly in flux, but on galactic scales.
Out sun viewed in time-lapse photography probably sputters bright and dim all the time- we just dont see it because it takes thousands of years.
By the same token I bet our planets either move in and crash into the sun OR move away and fling out into space, ... eventlually.
The ONLY thing that puzzles me about this behavior is how scientists can think there is anything abnormal about this. Things are constantly in flux, but on galactic time scales.
OuR sun viewed in time-lapse photography probably sputters bright and dim all the time- we just dont see it because it takes thousands of years.
By the same token I bet our planets either move in and crash into the sun OR move away and fling out into space, ... eventlually.
"In this case, what we see is what was left behind after the planetary accretion disk dissipated and the tidal torques disappeared."
I think that explains it.
Two More Extrasolar Planets And Evidence Of A Mature Planetary SystemOne of the newly found extrasolar planets is the first whose average distance from its parent star is nearly the same as Earth's distance from the sun. The planet, however, is far heavier than Earth, at least 1.36 times as massive as Jupiter, and has a much more elongated orbit. The planet ventures closer to its host star than Venus' average distance from the sun and farther away than Mars' average distance. It orbits the star HD210277, which is 68 light-years away from Earth.
Ron Cowen
Science News
The other new planet orbits its parent star, HD187123, more closely than any other planet found so far. Its circular orbit lies at a distance less than one-ninth the average separation between the sun and Mercury, the solar system's innermost planet. HD187123 lies 156 light-years away from Earth. Both planets were detected by a team that includes R. Paul Butler of the Anglo-Australian Observatory in Epping, Australia, and Geoffrey W. Marcy of San Francisco State University and the University of California, Berkeley. The team will report the discovery of the closely orbiting planet in an upcoming "Publications of The Astronomical Society of the Pacific".
Wholeheartedly agree -- knowledge is never complete.
Swiss Team Discovers Third Extrasolar PlanetA Swiss team of astronomers has discovered its third extrasolar planet in less than a year. Using the 1.2-meter Euler Swiss telescope at the La Silla Observatory in La Serena, Chile, they have found a Jupiter-size planet orbiting in a near circle around the 8-th magnitude star HD 130322 in the constellation Virgo.
by Jeff Kanipe
Sep 09 1999
Lying at a distance of only 7.4 million miles from its parent star (Mercury orbits the Sun at a mean distance of 36 million miles) the planet completes an orbit in only 10.7 days.
Astronomers classify the new planet as a "hot Jupiter" type with a surface temperature of about 1,000 kelvins (1340 degrees fahrenheit).
The star, which lies below naked-eye limit, is similar to the Sun in composition but is only about half as bright. It lies some 100 light-years away and, aside from its planetary companion, is otherwise unremarkable.
Astronomers glimpse atmosphere of extra-solar planetBrown has been studying one planet with an orbit that takes it directly between us and its star, HD 209458. The giant planet is a hot Jupiter or "roaster", only around 7.5 million kilometres from its sun. It passes in front of the star every 3.5 days, and when it does it blocks around 1.6 per cent of the star's total light, meaning its diameter must be about 30 per cent larger than Jupiter's.
by Jeff Hecht
27 November 01
try the web archive
The theory (which actually makes sense) is that when the sun becomes a red giant, it will either vaporize Mercury and Venus (maybe Earth and Mars) and Earth and Mars will be scorched, but actually move somewhat away from the sun as it will have less mass at that time to hold onto the planets with.
That doesn't take into account the possibility of another star or alien body entering our solar system and throwing things off a bit...
Astronomers Announce the Most Earth-Like Planet Yet Found Outside the Solar SystemThe newly discovered "super-Earth" orbits the star Gliese 876, located just 15 light years away in the direction of the constellation Aquarius. This star also possesses two larger, Jupiter-size planets. The new planet whips around the star in a mere two days, and is so close to the star's surface that its dayside temperature probably tops 400 to 750 degrees Fahrenheit (200 to 400 degrees Celsius)--oven-like temperatures far too hot for life as we know it... The team measures a minimum mass for the planet of 5.9 Earth masses, orbiting Gliese 876 with a period of 1.94 days at a distance of 0.021 astronomical units (AU), or 2 million miles... Gliese 876 is a small, red star known as an M dwarf--the most common type of star in the galaxy. It is located in the constellation Aquarius, and, at about one-third the mass of the sun, is the smallest star around which planets have been discovered. Butler and Marcy detected the first planet there in 1998; it was a gas giant about twice the mass of Jupiter. Then, in 2001, they reported a second planet, another gas giant about half the mass of Jupiter. The two are in resonant orbits, the outer planet taking 60 days to orbit the star, twice the period of the inner giant planet... Lissauer also is excited by another feat reported in the paper submitted to the journal. For the first time, he, Rivera and Laughlin have determined the line-of-sight inclination of the orbit of the stellar system solely from the observed Doppler wobble of the star. Using dynamical models of how the two Jupiter-size planets interact, they were able to calculate the masses of the two giant planets from the observed shapes and precession rates of their oval orbits. Precession is the slow turning of the long axis of a planet's elliptical orbit. They showed that the orbital plane is tilted 40 degrees to our line of sight. This allowed the team to estimate the most likely mass of the third planet as seven and a half Earth masses.
NSF Press Release 05-097
June 13, 2005
The theory (which actually makes sense) is that when the sun becomes a red giant, it will either vaporize Mercury and Venus (maybe Earth and Mars) and Earth and Mars will be scorched, but actually move somewhat away from the sun as it will have less mass at that time to hold onto the planets with.Quibble -- the solar mass won't suddenly be reduced by expansion; also the expansion (if such occurs) will place part of the solar mass closer to the Earth, and as you know, distance is more important than mass. :')
What we need is a functional technique whereby we can change the orbits of planets.
Did Jupiter Bully Other Planets in Sibling Rivalry?One possible explanation, discussed in Thursday's issue of the journal Nature, is that Uranus and Neptune formed much closer to the center of the action than their current positions might indicate. In this scheme, Jupiter and Saturn were bullies of a protoplanetary playground, shoving the other two future giants out of the way.
by Robert Roy Britt
8 December 1999Jupiter gave birth to Uranus and NeptuneNot too long ago, scientists regarded the orbits that the planets circle our Sun as being the ones they were born in. Now they are realising that this is not the case. Uranus and Neptune may have migrated outwards and Jupiter may have come in from the outer cold. Scientists have always been slightly puzzled by the positions of Uranus and Neptune because in their present locations it would have taken longer than the age of the Solar System for them to form. Scientists from Queen's University suggest that the four giant planets started out as rocky cores in the Jupiter-Saturn region, and that the cores of Uranus and Neptune were tossed out by Jupiter's and Saturn's gravity.
by Dr David Whitehouse
8 December 1999Jupiter's Composition Throws Planet-formation Theories into DisarrayExamining four-year-old data, researchers have found significantly elevated levels of argon, krypton and xenon in Jupiter's atmosphere that may force a rethinking of theories about how the planet, and possibly the entire solar system, formed. Prevailing theories of planetary formation hold that the sun gathered itself together in the center of a pancake-shaped disk of gas and dust, then the planets begin to take shape by cleaning up the leftovers. In Jupiter's current orbit, 5 astronomical units from the sun, temperatures are too warm for the planetesimals to have trapped the noble gases. Only in the Kuiper belt -- a frigid region of the solar system more than 40 AU from the sun -- could planetesimals have trapped argon, krypton and xenon.
by Robert Roy Britt
Nov 17 1999
While lead researcher Tobias Owen does not put much stock in the idea that Jupiter might have migrated inward to its present position, other scientists on the team say the idea merits consideration. Owen expects the probes will find similarly high levels of noble gases in Saturn, Uranus and Neptune. Hints of these gases have even been found in the thick atmosphere of Venus, another planet now begging more study.Newfound Moons Tell Secrets of Solar SystemThe fact that most of the satellites' orbits are retrograde and eccentric speaks volumes about their origins: They had to have come from elsewhere, and been captured by the planets at some point. If they formed at the same time as the planets, from the spinning nebular disk, their orbits would be nearly circular and in the same direction as the planets' rotation, like the "regular" moons... In the case of the irregular satellites, they could not have shifted from an orbit around the Sun to an orbit around one of the giant planets without slowing down -- through friction in an atmosphere, perhaps; the influence of gravity; or a collision with another object... But there are two other possibilities for capture, Dr. Nesvorny said. One is that rapid growth of the core led to a corresponding increase in gravity, enough to pull down a nearby object. The other is that captured objects were a result of a collision between two planetesimals, the force of the collision being enough to dissipate the energy of at least one of them. Either of these two theories may be a more likely explanation for the satellites of Uranus and Neptune, which formed differently from Jupiter and Saturn, without the large amounts of gas.
by Henry Fountain
August 12, 2003
For terraforming? To create a "string of pearls"?
That's right. Mercury and Venus are going to waste.
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