A Giant Surprise about Extrasolar Planets

Giant stars with planets often have smaller amounts of heavy elements than
the Sun, say astronomers in the United States and Germany. This trend is
surprising: it is opposite the one seen in planet-bearing main-sequence
stars and suggests stars more massive than the Sun may give birth to planets
in a different way.

The full story is at http://KenCroswell.com/AGiantSurprise.html .

Correct email: MagnificentUniverse "at" yahoo "dot" com.

On Mon, 12 Sep 2005 23:39:25 GMT, "Magnificent Universe"
wrote, in part:

Giant stars with planets often have smaller amounts of heavy elements than
the Sun, say astronomers in the United States and Germany. This trend is
surprising: it is opposite the one seen in planet-bearing main-sequence
stars and suggests stars more massive than the Sun may give birth to planets
in a different way.

One question that should be answerable right now: is the metallicity of
giant stars *in general* lower than that of main-sequence stars *in
general*? If so, and given that the distribution of metallicities for
giant stars with extrasolar planets is fully overlapped by that for
main-sequence stars with extrasolar planets, as shown in the diagram on
your page, then, instead of forming planets "in a different way", the
phenomenon might simply be due to the giant stars with extrasolar
planets having to exist as giant stars in the first place.

Not that a more massive protoplanetary disk wouldn't help.

John Savard
http://home.ecn.ab.ca/~jsavard/index.html
http://www.quadibloc.com/index.html
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Magnificent Universe wrote:
Giant stars with planets often have smaller amounts of heavy elements than
the Sun, say astronomers in the United States and Germany. This trend is
surprising: it is opposite the one seen in planet-bearing main-sequence
stars and suggests stars more massive than the Sun may give birth to planets
in a different way.

The full story is at http://KenCroswell.com/AGiantSurprise.html .

Correct email: MagnificentUniverse "at" yahoo "dot" com.




Extrasolar Planets: A Matter of Metallicity
http://www.spaceref.com/news/viewpr.html?pid=15261

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."




Extrasolar Planets and Metallicity
http://www.aas.org/publications/baas...aas193/150.htm

Results of spectroscopic analyses of the parent stars of extrasolar
planets are summarized. The metallicities of stars with planets are
compared to those of field stars and shown to be larger on average.
The stars with close-in planets are particularly metal-rich. Two
possible explanations of the observed trends a 1) primordial,
2) self-enrichment via accretion of H-poor material. Observational
tests of these two hypotheses are suggested.