Geneva Observatory astronomers Study spectral lines in the visible spectrum and detect a planet thefirst to be observed outside our own planetary system - orbiting a sun-like star. The finding might lead to inflow of fresh data on planetary evolution
IN THE vast expanses of the universe, the
fact that we are the only planetary system around a star would stand out to be
against all laws of probability. The
chances are that there are many such
extrasolar planets in the numerous
galaxies which make up the universe.
The rub is that since they are so small
and so far, their detection is extremely
difficult, while imaging them is almost
always out of question. Consequently,
when two astronomers reported some
evidence of such a planet near a sun-like
star, it generated much excitement in
the community (Science, Vol 270,
October 20, 1995).
Michel Mayor and Didier Queloz at
the Geneva Observatory have reportedly
found the first planet - outside our
own solar system - which orbits a sun-
like star (in 1994 a planet was found in
orbit around a pulsar). The planet is
almost half the mass of Jupiter, and is in
a tight orbit around the star 51 Pegasi,
Just outside the Great Square of
Pegasus (a square formed by the stars
of the Pegasus constellation). The
orbital radius is only about a sixth of
that of Mercury, with orbiting period of
4.2 days.
The technique of looking for such
small objects is an indirect one. The
planet which orbits the star produces a
wobble in the orbit of the star. The wobble is detected by the shifting in wavelength of the light emitted from the
star's surface. The light from the parts
moving towards us is blue shifted, while
the light from the portions moving away
is red shifted. Mayor and Queloz
analysed about 5,000 spectral lines in
the visible spectrum and detected the
wobble and the presence of the planet.
Another group at the Lick
Observatory in the US, headed by Geoff Marcy and Paul Butler, has provided
independent confirmation of the wobble in 51 Pegasi. Although any conclusive evidence for the planet is still missing, there is considerable excitement
among the planetary scientists. Several
effects which could also have caused the
wobble are being studied - from an
unknown type of stellar pulsation to an
unseen binary companion. There is a
possibility that standard models of planetary evolution are going to be modified
in the light of the data recieved in
the course of the discovery of this new
planet.
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