Re: Solar System around 55 Cancri

On Thu, 8 Nov 2007 20:46:25 -1000, "Alvin E. Toda" <aet@xxxxxxxx>
wrote:

On Thu, 8 Nov 2007, Rumpelstiltskin wrote:

Lehrer's newshour yesterday had an unusual segment
about a nearby solar system around a star 40 light
years away, in the constellation Cancer. The
interesting thing is that there are apparently five
planets so far around this star, which is evidence
supporting the idea that solar systems are common.
The planets around 55 Cancri are huge by our solar
system's standard, the four smaller ones being about
the size of Neptune and the more distant large one
being four times the size of Jupiter, or we wouldn't
be able to detect them yet. We haven't actually
"seen" the planets, we just know they're there by
analyzing the wobble of the star that we can see.
Similarly, our own sun would move slightly back and
forth as see from a distance, because Jupiter pulls
on the sun as it orbits around it.
http://www.sciencedaily.com/releases/2007/11/071106133058.htm
Analyzing the components of the wobble of 55 Cancri
based on five large planets pulling on it seems to me
quite a difficult project, because of the exactness
required about the change of position of the star
over a period of time needed to allow multivariate
analysis of what components would be contributing to
its complex resultant pattern of motion.

55 Cancri is a yellow dwarf like our sun, and in
addition to its planetary system it has a red dwarf
companion 1000 AU away:
http://en.wikipedia.org/wiki/55_Cancri

40 light years is fairly close to us. The closest
star system to Sol is the Alpha Centauri system four
light years away, so there are (ball-park) only about
(40/4) cubed = 1000 stellar systems that close to us.

Hope we get to communicate with one of these one of
these days!

If the orbits are as large as in our system, then I
agree that it's a difficult job to identify the planets
from the wobble. But it may be that the peculiar wobble
is just a way to identify stars which are different
from binary star wobble which is when two stars revolve
arround each other. Some of the distant planet orbits
may be decades long.

I would guess that spectroscopic data would show
multiple light sources at different temperatures-- all
at a lower temperature than the sun of course. And the
intensity of the sources would be an indication of
their size. Look to the infrared spectrum and a way to
block out the solar infrared-- with good enough optical
resolution I guess. To close the question, a
calculation to show that there exists a given set of
orbits such that the observed planets are sufficient to
explain the peculiar wobble.


We can tell the mass of the planets from the mass
of the star, and the orbit from the period of the wobble.
As I've noted before, if we can detect oxygen in a
planetary atmosphere, that would be a very strong
indication there was life there. Oxygen is so reactive
that it couldn't remain long in an atmosphere before
combining with something, so for it to be in an
atmosphere it would have to be getting continually
pumped in. The only major thing we know that can
do that on a planet is life.

Even without "seeing" the planets, we could still
detect oxygen-bearing planets with data refined
enough that we could cancel out the Fraunhofer
lines from the star, leaving us with just those from
the planet(s). That sounds to me like an awfully
demanding task, and I suppose we're not there
yet, but we should get there.

I've read that because of radio and television
transmissions, the earth at those wavelengths is
now "hotter" than the sun, which is another thing
extraterrestrials looking to see if there was life in
our solar system might be trying to check out.
If they have high technology they must have
radio and television too, and, since the physics is
the same, they'd know that the wavelength range
we'd use would be the same as what they use.


.

Relevant Pages

  • Re: Switch to E85
    ... our own local solar system. ... some of us could name the nine planets of our ... we now know of at least 100 planets orbiting other ... orbiting a dying pulsar star. ...
    (misc.survivalism)
  • Re: Solar System around 55 Cancri
    ... about a nearby solar system around a star 40 light years away, ... The interesting thing is that there are apparently five planets so far around this star, which is evidence supporting the idea that solar systems are common. ... We haven't actually "seen" the planets, we just know they're there by analyzing the wobble of the star that we can see. ...
    (soc.retirement)
  • Pizza Gram
    ... Is Earth the only place that delivers Pizza? ... to confirm that one is not alone when eating pizza at a Star Party! ... fp is the fraction of those stars with planets (thought to be ...
    (sci.astro.amateur)
  • Astronomers Discover Dusty Remains of Two Terrestrial Planets
    ... Two terrestrial planets orbiting a mature sun-like star some 300 ... light-years from Earth recently suffered a violent collision, ... astronomers at UCLA, Tennessee State University and the California ...
    (sci.space.news)
  • NASAs Spitzer Spots Clump of Swirling Planetary Material
    ... NASA's Spitzer Spots Clump of Swirling Planetary Material ... Something, perhaps another star or a planet, appears to be ... Planets form out of swirling disks of gas and dust. ... grains swirling around a star in a disk. ...
    (sci.space.news)