Explanation:
Is our Earth unique?
In continuing efforts to answer this question, astronomers have
now discovered an Earth-like planet orbiting a distant normal star.
Previously
over 150 gas-giant
planets like
Jupiter
had been so discovered.
Slight, fast, but regular
wobbles of nearby small
M-dwarf
star Gliese 876 showed evidence for a planet
with a likely mass slightly higher than a minimum six
times the mass of Earth.
The planet's small mass indicates that it is likely
terrestrial in nature,
similar in composition to the inner planets of
our Solar System.
If indeed made predominantly of rock, the planet's
surface gravity would not even be able to contain the
gasses of a Jupiter-like planet.
The newly discovered planet would not make a
good vacation spot
for humans, however, as it orbits so close that the surface
temperature probably tops a searing 200 degrees
Celsius.
The system is illustrated in the
above drawing as seen from a hypothetical moon orbiting
one of the two Jupiter-like planets
already known.
The newly discovered terrestrial-like planet is depicted in the insert.
Gliese 876 lies only 15 light-years away and is visible with binoculars toward the constellation of Aquarius.
