For a long time astronomers and laymen alike have speculated that worlds like those found
in the Solar system might be found orbiting other stars.
Even if there has been indications that such worlds exists elsewhere noone have been
able to prove that conclusively until a few years ago.
The first planets which was discovered by US scientist Alex Wolszczan did not orbit an
ordinary star however, but a remarkable object called a millesecond pulsar*.
One of the planets probably have a mass of at least 3.4 times of earth and the other
might be 2.8 times more massive both orbiting at about the same distance from the pulsar as the
planet Mercury orbits the Sun.
Later refined studies revealed a third planet with the size of earth's moon that orbits even closer to the pulsar and in the spring of 1997 a fourth planet with a mass between of about 1/3 of Jupiter have been detected in the outskirts of this planetary system at about the same distance as Pluto or Neptune are from the Sun.
In 1994 it was proven that this planetary system is for real, yet the debate is still going on over the question if these planets have been orbiting this pulsar since it was an ordinary star or if they might have formed later from the material blasted into sppace when the star exploded.
The second explanation is favoured by most astronomers, and they think that the discovery of this planetary system doesn't tell us anything about the formation of planetary systems like our own. But since then astronomers have found more planets around ordinary stars elsewhere in the galaxy than what we have here in our own solar system. So overall, it seems that planetary systems are quite common.
It must be noted that all these planets are big and massive, and that the instruments can't detect planets of Earth's size.
(The pulsar planets is a special case, smaller planets have been detected there since the spin of the millisecond pulsar in that case is used as the detector. The rotation is usually as exact as an atomic clock, and the small disturbances caused by the planets is the proof of their existence. )
Yet the presence of the worlds found is an indication that smaller planets might exist at the other stars. And again, even if there is no earth type planets some of those already found might have large moons and if these in turn have an atmosphere they might be hospitable for life.
Even though the claim of discovery for a few of the most oddball planets, called "hot Jupiters" have been questioned by some astronomers, most accept the fact that these findings are for real.
Some researchers are optimistic and hope to be able to imagine some of the largest and closest planets in the next year or so using new technology which is in developement. This doesnt mean we will have a closer look, but only as a way of confirming that one such planet are for real. And now in August 2001 Geoffrey Marcy and Debra Fischer announced they found a second planet circling 47 Ursae Majoris, this a planet of Jupiters size.
Even though there's some differences, their circular orbits and the ratio between the planets mass makes this system resemble our own Jupiter and Saturn. So at the moment we can say that 47 Ursae Majoris is the stellar system which most resembles our own solar system.
Big planets have also been found at Rho Cancri and Tau Bootis, the later planet orbits very
close to it's sun which makes it similar to the 51 Pegasi system shown in the illustration.
The latest planet that was added to the list in 1997 is one of at least Jupiters mass, orbiting the
star Rho Coronae Borealis. In addition to these Lalande 21185, at a distance of 8.25 lightyears might be orbited by two
planets the size of Jupiter and Saturn making it the closest known planetary system
to date. (The report that the Hubble space telescope might have found a possible planet at Proxima Centauri ~4.21 light years away remains unconfirmed and is in doubt by some scientists as of February 1998).
The object orbiting 70 Virginis is shown smaller than Jupiter even though it has more mass, this is correct since such an object would have a much powerful gravitation that would make such a world more compressed, that it would be so hot from this compression that it would glow like a faint star is a speculation of our artist.
A millisecond pulsar is a neutron star a stellar corpse after a star who have aged and consumed all the nuclear fuel which once made it shine. Some neutron stars are called pulsars since they send out radio energy which can be detected with radiotelescopes, they arn't really pulsating but appear to send out pulses when the radioemitting parts of these small stellar corpses points in our direction during their rotation, a few of these are called millisecond pulsar because they spins so fast that the radiopulses arrvives many times each second.
The one described here spins 161 times each second.
While we was writing the page we was reached by the news that the the two red dwarf stars CM Draconis 50 light-years away might be orbited by a planet 85% of Jupiters size. If this finding is confirmed it would be the first planet found who orbits two stars at the same time.
Some astro related rants in a lighthearted vein.....
More on this subject at Mr Bill Arnetts webpage "Other Planetary Systems?"