Bizarre cometlike alien planet is first of its kind

[IceWizard]

Http://foxnews.com/science/2015/06/25/bi...-its-kind/


A Neptune-size planet appears to be
masquerading as a comet, with a gargantuan stream of gas flowing behind it like a comet's tail.

The bizarre find is the first of its kind ever
discovered by astronomers. The strange,
cometlike planet, known as GJ 436b, is
orbiting a red dwarf star and is about 22
times as massive as Earth. Astronomers
detected the giant gas cloud around the planet using NASA's Hubble Space Telescope and Chandra X-ray Observatory.

"I was astonished by the mere size of the
cloud of gas escaping from the planet," said
study lead author David Ehrenreich, an
astronomer at the observatory of the
University of Geneva in Switzerland.
[The Strangest Alien Planets] GJ 436b, located about 33 light-years from Earth in the constellation Leo, is a kind of world known as a warm Neptune.

Such planets, at about 10 to 20 times the
mass of Earth, are about the mass of "cold
Neptunes" such as Uranus — and, naturally, Neptune — but they are as close, or closer,
to their stars than Mercury is to our sun.
With an orbit of only about 3 million miles,
"GJ 436b is 33 times closer to its star than
Earth is to the sun, and 13 times closer than
Mercury," Ehrenreich told Space.com.

The cloud of gas around GJ 436b, made up
mostly of hydrogen, has a circular head that
surrounds GJ 436b, and a tail trailing behind
the planet. The diameter of the head is
about 1.8 million miles, or five times the
width of the host star, which is about half that of the sun, Ehrenreich said.

The length of the tail is uncertain, because the
research team's observations do not cover
it entirely, but their computer models suggest it could be about 9.3 million miles long.

Although prior research has predicted that
other gas giants should be blowing off
cometlike tails, based on how hot they must
be due to their proximity to their stars, "GJ
436b is the first planet for which a cometlike
tail is confidently detected," Ehrenreich said. (A previous study revealed indirect evidence of a rocky world that appears to be disintegrating around its host star, creating a cometlike tail of material behind the planet. That study used data from NASA's Kepler space telescope, which observed scattering of the light from the planet's host star.)

The scientists estimated that GJ 436b is
currently blowing off up to 1,000 tons of gas
per second. This means that GJ 436b is
currently losing about 0.1 percent of its
atmosphere every billion years, which is far
too slow a rate to deplete its atmosphere in the lifetime of its parent red dwarf star.

However, when the star was more active in
its infancy, the researchers estimated that
GJ 436b could have lost 10 percent or more
of its atmosphere during its first billion
years.

Recently, another team of researchers
suggested that GJ 436b might possess a
helium-rich sky depleted of hydrogen.
"However, in order to be really hydrogen-
poor and helium-rich, the atmosphere of GJ
436b should have represented a very small fraction of the planet['s] initial mass, around
one-thousandth," Ehrenreich said. "In such
a case, the whole atmosphere would have
been gone today, which as we measure is
not the case."

Ehrenreich noted that the Kepler spacecraft, as well as NASA's upcoming TESS space mission and the European Space Agency's future CHEOPS and PLATO spacecraft "are poised to find thousands of system like GJ 436 in the coming years."

This suggests that many other planets with cometlike tails could soon be discovered. The scientists now plan to investigate less massive planets, such as "super-Earths" and "mini-Neptunes" to see if they might also have puffy atmospheres and cometlike tails.

"We're going to study one such object in the
course of next year with Hubble, and have
proposed to observe several more,"
Ehrenreich said. The scientists detailed their findings online June 24 in the journal Nature.