Science News - September 24, 2011

NEWS BRIEFS Earth not so special Recent observations have burst the idea that the Earth occupies a special spot in a gigantic cosmic bubble. The work counters proposals to explain the apparently accelerating expansion of the universe without a mysterious force known as dark energy. Such proposals reject the Copernican principle, which holds that the Earth occupies a typical location in the cosmos. If instead Earth occupies a sparsely populated bubble, galaxies within it would zip away rapidly, pulled by the gravity of the denser stuff outside, mimicking an accelerating cosmic expansion. But such galactic motion should leave imprints in microwave radiation from the Big Bang. Telescopes in Chile and Antarctica ;nd no such evi-

330 exoplanets

dence, astrophysicists from China and the United States report in the July 22 Physical Review Letters. — Devin Powell

Pulsar’s diamond planet
Astronomers have discovered the
densest exoplanet yet —they call it
a diamond planet —orbiting a whirl-
ing pulsar. Though the ;rst exoplanet
system found circles one of these
spinning stellar cores, no other pulsar
planets have been spotted since.
The new exoplanet is comparable in
mass to Jupiter but 20 times denser,
an international team reports online
August 25 in Science. The planet may
be made of carbon and oxygen instead
of the hydrogen and helium that are
found in run-of-the-mill gas giants; it
Discovered
up to end
of 2008

269 exoplanets

Discovered
2009–
Sept. 6, 2011

could be an über-lightweight dead star called a white dwarf that became a planet when its mass was stolen by the pulsar. — Camille M. Carlisle

Earthy exoplanets
Scientists have created rap sheets for
six planets beyond the solar system,
orbiting three distant stars. One star
hosts a system with three super-Earth
planets, heavier than Earth but lighter
than gas giants. Another harbors a
3.6-Earth-mass planet within its hab-
itable zone, scientists from Europe
report online August 17 at arXiv.org.
That planet, HD 85512b, described in
a second paper at arXiv.org, could be
habitable if clouds cover more than
half its surface. — Nadia Drake