With time it was realized that the Earth was just one of the
solar planets orbiting the sun, but skepticism that planets existed outside the
solar system remained strong. However, with the advent of new techniques
and more power telescopes researchers began to discover
extrasolar planets at a rapid
pace, starting in the 1988, with the discovery of planets orbiting the star
Gamma Cephei. Meanwhile a large new orbiting body was discovered
on the fringes of our own system, while Pluto was downgraded
to a mere "Plutoid".
Some of these planets were deemed somewhat
Earth-like in that they were smaller than gas giants, might have water, and
could be made to be habitable. Other extrasolar planets were similar in
size to Earth, but were way
to hot to inhabit with current technologies.
Now European astronomers have continued the run of discoveries of smaller
planets with the discovery of a trio of "super-Earths" rotating around
the star HD 40307, located 42 light-years from Earth towards the southern
Doradus and Pictor constellations. The new planets have masses of 4.2,
6.7, and 9.4 times the mass of Earth and orbits of 4.3, 9.6, and 20.4 days
The star they orbit is a normal star, approximately the same size as our
sun. According to Didier Queloz and Michel Mayor, expert planet hunters
who led the discovery team, the planets are too hot to support life as we know
However, despite this slight disappointment, the discovery raises the
intriguing possibility of a so-called "crowded universe" teeming with
undiscovered planets. HD 40307 was long thought to hold no planets -- it
is clear now that the discovery was only possible with the advances in
detection. There are likely many smaller planets that have yet to be
detected. In total 270 extrasolar planets have already been found.
Stéphane Udry, a colleague of Mayor, describes the advance stating, "With
the advent of much more precise instruments such as the HARPS spectrograph on
ESO's 3.6-m telescope at La Silla, we can now discover smaller planets, with
masses between 2 and 10 times the Earth's mass."
Mayor who works at the Geneva Observatory states, "Does every single star
harbour planets and, if yes, how many? We may not yet know the answer but
we are making huge progress towards it. Clearly these planets are only
the tip of the iceberg. The analysis of all the stars studied with HARPS
shows that about one third of all solar-like stars have either super-Earth or
Neptune-like planets with orbital periods shorter than 50 days."
The slowly unfolding picture of a universe full of planets brings two key
possibilities. First, the possibility of expansion
and colonization outside the solar system, and secondly, the possibility
of extraterrestrial life.