From: Karee Swift (email@example.com)
Date: Fri Aug 04 2000 - 10:56:50 PDT
--- In BiTTS@egroups.com, "Karee Swift" <karee@t...> wrote:
Jupiter-sized Planet Discovered Orbiting Epsilon Eridani
Thursday, August 03, 2000
On Monday 7 August 2000, an announcement will be made at a meeting
of the IAU (International Astronomical Union) that a Jupiter-sized
planet has been discovered orbiting the nearby star Epsilon Eridani.
The announcement will be made by Dr. William Cochran of the McDonald
Observatory in conjunction with a presentation at the IAU Symposium
on "Planetary Systems in the Universe" being held next week in
Epsilon Eridani is a sun-like (K2V) star located in the constellation
Eridanus 10.5 light years from Earth. Epsilon Eridani is much younger
than our sun with an age estimated at less than one billion years.
This star has only 79% the mass of our sun and is only about half as
The newly-discovered planet is in an elliptical and somewhat
eccentric orbit with an average distance estimated to be 478 million
kilometers (297 million miles) from its parent star - a distance
roughly equivalent to the distance that the asteroid belt is from our
own sun. The planet is suspected of being a gas giant and takes
approximately 7 years to complete one orbit.
The discovery was made by astronomers at the McDonald Observatory at
the University of Texas at Austin in collaboration with other
astronomers around the world.
This discovery follows upon an earlier discovery in July 1998 by the
Joint Astronomy Centre, the University of California at Los Angeles,
and the Royal Observatory in Edinburgh, of a large dust cloud
orbiting Epsilon Eridani at roughly the distance one would expect for
a belt of comets. Images obtained at that time (right) included a
large prominent bright spot which was thought to be indicative of a
possible large planet.
News of this impending announcement first emerged on 31 July 2000
when space.com posted a brief article - one that was pulled offline
just a few hours later. Information regarding this discovery was
released to reporters by the IAU in advance under conditions of a
strict embargo which expires on 7 August 2000. SpaceRef has been able
to obtain independent confirmation of this discovery.
In a SpaceRef story earlier this year, "Hot Jupiters and Rare Earths:
Planets are common. Are we?", the effect of the formation (and
location) of large jovian class planets and the formation of
habitable Earth-like worlds was examined:
According to one model, giant gas planets may push each other around.
If, for example, you have 3 large gas planets forming in a solar
system out in regions where ices are abundant, they will excite each
other's orbital eccentricities. Over time this will cause orbits to
shift around. Eventually planets will actually swap their relative
order with respect to one another and their parent star. As this
happens, the inner most planet moves outward, the outermost planet
moves inward, and the planet in the middle is ejected from the solar
system altogether While this model tends to explain why many of the
hot Jupiters discovered thus far have high orbital eccentricities,
this is not the leading explanation.
The other, more accepted model involves interactions between forming
planets and with the dust disk from which they are forming. An analog
to this process has been observed in Saturn's giant ring system.
Small saturnian moons orbiting close to the rings tend to disrupt the
organization of the rings. In so doing, spiral density waves are
produced. These perturbations result in movement of the moons
themselves via gravitational interactions. On the larger scale of a
solar nebula, so the theory goes, spiral density waves clear out a
space within the developing dust disk and locks the planet into a
position in the cleared space. Later, as nebula moves inward and
material falls into the sun, the planet moves inward, hence closer to
the local star.
As is always the case with the universe one thing always affects
another. The closer a large Jupiter-sized planet is to its local star
during planetary formation, the smaller the chance that Earth-like
planets will form. Evidence of this effect can be seen in our own
solar system in the asteroid belt between Mars and Jupiter where
Jupiter's gravitational influence has either hindered planetary
formation or caused objects to collide and fragment before they
achieved planetary size. As such, if the object is to find more
potential Earths, then the emphasis should be to search within solar
systems wherein large gas giants form further out than those
--- End forwarded message ---
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