[meteorite-list] A Bucket Full of Exoplanets

From: Sterling K. Webb <sterling_k_webb_at_meteoritecentral.com>
Date: Wed, 16 Jun 2010 03:33:31 -0500
Message-ID: <CB08788AEBF74C1A9FD0709742A308D3_at_ATARIENGINE2>

Dear List,

The Kepler spacecraft started observing stellar transits
to detect extrasolar planets on May 15, 2009. By Jan. 4,
2010, they released data on the first five planets found
(all SuperJupiters):
http://www.sciencedaily.com/releases/2010/01/100104131643.htm

They have now obtained data on 706 more "candidates"
or potential exoplanets, virtually doubling the number of
discovered exoplanets. If they pan out (some may be unusual
binary stars), this would push the number of exoplanets
to over 1,000!:
http://arstechnica.com/science/news/2010/06/latest-kepler-data-includes-over-700-expolanets.ars

Another news story:
http://www.sciencenews.org/view/generic/id/60302/title/Kepler_craft_reports_apparent_planetary_bonanza

This press release story shows a small scatter graph of
100 of the larger "potentials." This is enough data to say
something about the general character of solar systems
in our neck of the galaxy.
http://www.sciencedaily.com/releases/2010/06/100615192010.htm

It shows the tight cluster of "hot Supers and Jupiters" that we
expect, having found so many, but a much bigger clump of
more large planets at distances that correspond to the distance
from the Earth through the Asteroid Belt in our system, out
to Jupiter's distance. Jupiter would plot on the low right of
that clump.
http://www.sciencedaily.com/images/2010/06/100615192010-large.jpg

This selection is still biased toward larger, nearer exoplanets,
but it seems that the clump of giants between 2 and 5 AU is
a seriously major class of planets in the general sense. This
essentially defines a numerous type of solar system that is
NOT like ours, just as the less numerous hot Supe's and
Jupe's are NOT like us.

Planets with our mass will be the last to show up at the data
party. These 706 potentials are from only 43 days of observing
156,000 stars, and all the small potentials have been excluded
from the list of 400 by NASA, including (reportedly) some with
radii of less than 1.5 Earth radii (or less than 3 Earth masses).
No official release of data is promised until February, 2011.

One thing that is demonstrated is that there are more small
planets than large ones, news sure to get a cheer from all
us small planet critters:

"...for a substantial range of planet sizes, a 1/(R^2) curve
fits the Kepler data well. Assuming the false positive
rate and other biases discussed above are independent
of planet size for planets larger than two Earth radii,
this implies that the frequency of planets decreases
with the area of the planet."

In other words, more little planets than big ones. The
neighborhood could be lousy with Earths. The quote
is from the draft paper on the 706 candidate objects:
http://lanl.arxiv.org/ftp/arxiv/papers/1006/1006.2799.pdf

Paper on the five observationally confirmed big planets:
http://lanl.arxiv.org/PS_cache/arxiv/pdf/1006/1006.2763v1.pdf

Having pushed the number of exoplanets to over 1,000
in 43 days of observation and with 2.5 operational years
to go, how many exoplanets could Kepler end up finding?

Can't tell, but I'm betting on a LARGE number.



Sterling K. Webb
Received on Wed 16 Jun 2010 04:33:31 AM PDT