Top 10 Exoplanets: Weird Worlds in a Galaxy Not So Far Away
A look at some of our extreme planetary neighbors right here in
the Milky Way Galaxy
11, 2008 |
Hoth. Coruscant. Endor. These names will ring
familiar to fans of that galaxy far, far away—the setting for
including the new animated feature Star
Wars: The Clone Wars. Now what about
V391 Peg b? GJ 3021 b? WASP-15 b? If you guessed Star
you're wrong. They're the names of actual planets found around
other stars in our own Milky Way Galaxy.
Slowly but surely researchers are learning that our stellar
neighborhood is filled withextrasolar
better known as exoplanets. Many of them are just as, if not far
more, exotic as anything in the Star
And someday they may have names that are equally memorable.
View the Top Ten Exoplanets Slide Show
Scientists have found over 300 exoplanets since
1991, and they hope to find a great deal more. David Bennett, an
astrophysicist at the University of Notre Dame and a dedicated
planet hunter, says that current estimates peg the number of
stars bearing planets at about 30 percent, though he thinks this
figure is closer to 50 percent, as researchers believe that
current technology is not yet up to the task of spotting certain
categories of planets such as small, Earth-size ones. With 100
billion stars populating the Milky Way galaxy, that means some
50 billion planetary systems may await discovery, many of which
may hold multiple planets resembling our eight-planet
"We think there are actually more planets out there than stars,"
Unlike the livable worlds in Star
of the exoplanets discovered thus far are sufficiently
Earth-like in either size or distance from their star to be
deemed good candidates for life. The vast majority of known
exoplanets are so-called "hot Jupiters" (or "hot Yavins," in Star
large, gaseous bodies orbiting close to their host stars. The
apparent preponderance of inhospitable places stems from the
limitations of currently available detection methods.
Ground-based telescopes gatherindirect
an exoplanet's presence around a star, in the form of regular
variations of starlight, and smallish planets like Earth have
tiny, hard-to-discern effects on their massive hosts.
But NASA and other space organizations have
launched or are planning new missions to better identify
Earth-like planets. A European satellite called COROT (COnvection
ROtation and planetary Transits) has been successfully hunting
exoplanets since 2007, and early next year NASA plans to power
Kepler space telescope. This device will spy on 100,000 stars
simultaneously from solar orbit over four years to try and suss
out the miniscule signatures of Earth-like planets.
For now, we must rely
on artist's impressions to
get a sense of what all these extrasolar worlds may look like.
But getting actual pictures of exoplanets should become possible
in the coming years. The New Worlds Observer project,
tentatively scheduled to start up late next decade, will use a
to block out a star's overwhelming, planet-obscuring glare.
Scientists then hope to snap direct images of exoplanets and
study their atmospheres for telltale signs of life such as
oxygen and water vapor.
"The New Worlds Observer will allow us to look for evidence of
oceans and even continents on exoplanets whose stars are close
to Earth," says Webster Cash, the developer of the starshade and
an astrophysicist and planetary scientist at the University of
Colorado at Boulder.
1. PRIMORDIAL PLANET:
PSR B1620-26 b is believed to have formed an incredible 13
billion years ago, less than a billion years after the big bang
. Aptly nicknamed Methuselah, this probable gas giant resides in
an ancient type of galaxy known as a globular cluster, where it
orbits two stellar hosts, a white dwarf star and a pulsar, both
remnants of larger stars.
2. EARTH TIMES THREE:
The exoplanet MOA-192 b , which orbits a purplish star in this
artist's impression, is the smallest discovered so far,
measuring about 3.3 Earths in mass
3. IT'S A SMALL(ER) WORLD:
Besides being the first exoplanet ever directly observed from
Earth as it transited in front of its host star, exoplanet HD
209458 b (aka Osiris) is also shrinking
HD 149026 b ranks as one of the hottest known exoplanets, with a
lead-boiling surface temperature of around 3,700 degrees
Fahrenheit (2,000 degrees Celsius).
5. NOT TOO HOT OR TOO COLD?:
When astronomers spotted Gliese 581 c , it set off a flurry of
reports that this exoplanet fell within the so-called
"Goldilocks" zone where liquid water can exist on the planet's
6. FREAKISHLY FROZEN WORLD:
Scientists think Gliese 436 b (aka GJ 436 b), a Neptune -size
exoplanet, is too heavy to be all gas but not heavy enough to be
entirely rock. They surmise that in addition to gas and rock, it
also contains a kind of pressurized, high-temperature ice that
only exists on Earth in laboratories, where it goes by names
like "ice VII" and "ice X." The high pressures deep inside the
planet may stabilize this alternate solid state of water,
similar to the way intense pressures in Earth's crust can
squeeze carbon atoms into crystalline diamond .
7. POTPOURRI OF PLANETS:
Astronomers discovered a fifth planet around the sunlike star 55
Cancri in 2007, lending a familiar feel to this solar system and
making it the most planet-populated one outside our own--so far.
8. SURVIVOR OF APOCALYPSE:
V391 Pegasi b distinguishes itself as the only planet known to
orbit a star that has passed through its red giant phase . As
stars like our sun age, they run low on nuclear fuel in their
cores and swell to hundreds of times their original sizes.
9. TYPICAL STAR; EXTRAORDINARY PLANET:
The first exoplanet spotted around a typical or " main sequence
" star similar to our sun, gaseous 51 Pegasi b completes an
orbit around its host star every four days.
10. FIRST EXOWORLD:
The first solid evidence for an exoplanet (extrasolar planet)
came in 1992 when scientists calculated that two bodies must be
orbiting the pulsar PSR 1257.
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