Are Jupiters Hard to Come By?

Sky and Telescope 'blogs ^ | July 11, 2008 | Camille M. Carlisle

[SunkenCiv]

Using the new Combined Array for Research in Millimeter Astronomy (CARMA), Eisner and his colleagues observed more than 250 stars in Orion's central region and found that less than 8% had dust disks thought massive enough to create a Jupiter. The radiation from hot, massive stars in the cluster probably clears out a lot of surrounding material and keeps high-mass disks from forming, explains co-author John Carpenter (Caltech). In all, about 10% of the observed stars emit radiation associated with warm dust disks.

The results agree almost perfectly with findings by Geoff Marcy (UC Berkeley) and his colleagues, who conclude that about 10% of nearby stars have Jupiter-mass planets orbiting within 5 astronomical units (Jupiter's distance from the Sun). "This is an extraordinary moment in astronomy," Marcy says. Gas giants must form out of disks sufficiently massive to give birth to them, and "here we see that the numbers of such disks and of such planets agree."

The results do not mean, however, that only 10% of stars have planets. In fact, more than 10% of stars in Orion are known to possess disks massive enough to create a Saturn, and the average disk that the team found easily has enough material to make Neptune. CARMA isn't sensitive enough to detect the disks that would form smaller planets like super-Earths, but as Eisner explains, "With the average disk mass that we find, there seems to be adequate material there for terrestrial planet formation around a large percentage of stars."

[SunkenCiv]

An artist's concept shows a very young star encircled by a disk of gas and dust. The material in this protoplanetary disk will eventually form rocky planets. -- NASA / JPL-Caltech

[SunkenCiv]

most or all are dead links, but I didn't check 'em.

Did Jupiter Bully Other Planets in Sibling Rivalry?
by Robert Roy Britt
8 December 1999

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.

Jupiter gave birth to Uranus and Neptune
by Dr David Whitehouse
8 December, 1999

Not 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.

Jupiter's Composition Throws Planet-formation Theories into Disarray
by Robert Roy Britt
Nov 17 1999

Examining 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.

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.

[SunkenCiv]

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[Flycatcher]

You think Jupiters are hard to come by? Try removing the gas from Uranus.

[wastedyears]

To cruise by that in a spaceship...

[Rick.Donaldson]

Ummmm no. Nearly every extra-solar planet discovered thusfar are “Jupiter-like”.

[editor-surveyor]

"The material in this protoplanetary disk will eventually form rocky planets."

Using what for glue?

Its nonsense; the stuff will slowly fall into the star, as it visibly does in our solar system.

Liberals love to believe in artist's conceptions in all things.