By: SPACE.com Staff
Published: 02/21/2012 11:33 AM EST on SPACE.com
Scientists have discovered a new type of alien planet — a steamy waterworld that is larger than Earth but smaller than Uranus.
The standard-bearer for this new class of exoplanet is called GJ 1214b, which astronomers first discovered in December 2009. New observations by NASA's Hubble Space Telescope suggest that GJ 1214b is a watery world enshrouded by a thick, steamy atmosphere.
"GJ 1214b is like no planet we know of," study lead author Zachory Berta of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass., said in a statement. "A huge fraction of its mass is made up of water."
Adding to the diversity
To date, astronomers have discovered more than 700 planets beyond our solar system, with about 2,300 more "candidates" awaiting confirmation by follow-up observations.
These alien planets are a diverse bunch. Astronomers have found one planet as light and airy as Styrofoam, for example, and another as dense as iron. They've discovered several alien worlds that orbit two suns, like Luke Skywalker's home planet of Tatooine in the "Star Wars" films. [The Strangest Alien Planets]
But GJ 1214b, which is located 40 light-years from Earth in the constellation Ophiuchus (The Serpent Bearer), is something new altogether, researchers said.
This so-called "super-Earth" is about 2.7 times Earth’s diameter and weighs nearly seven times as much as our home planet. It orbits a red-dwarf star at a distance of 1.2 million miles (2 million kilometres), giving it an estimated surface temperature of 446 degrees Fahrenheit (230 degrees Celsius) — too hot to host life as we know it.
Scientists first reported in 2010 that GJ 1214b's atmosphere is likely composed primarily of water, but their findings were not definitive. Berta and his team used Hubble's Wide Field Camera 3 to help dispel the doubts.
Hubble watched as GJ 1214b crossed in front of its host star, and the scientists were able to determine the composition of the planet's atmosphere based on how it filtered the starlight.
"We’re using Hubble to measure the infrared color of sunset on this world," Berta said. "The Hubble measurements really tip the balance in favor of a steamy atmosphere."
Berta and his colleagues report their results online in the Astrophysical Journal.
A watery world
Since astronomers know GJ 1241b's mass and size, they're able to calculate its density, which turns out to be just 2 grams per cubic centimeter (g/cc). Earth's density is 5.5 g/cc, while that of water is 1 g/cc.
GJ 1214b thus appears to have much more water than Earth does, and much less rock. The alien planet's interior structure is likely quite different from that of our world.
"The high temperatures and high pressures would form exotic materials like 'hot ice' or 'superfluid water,' substances that are completely alien to our everyday experience," Berta said.
GJ 1214b probably formed farther out from its star, where water ice was plentiful, and then migrated in to its current location long ago. In the process, it would have experienced more Earth-like temperatures, but how long this benign phase lasted is unknown, researchers said.
Because GJ 1214b is so close to Earth, it's a prime candidate for study by future instruments. NASA's James Webb Space Telescope, which is slated to launch in 2018, may be able to get an even better look at the planet's atmosphere, researchers said.
Keep clicking for artists' conceptions of more planets discovered outside our solar system:
In this handout illustration made available on December 5, 2011 by NASA, the Kepler-22b, a planet known to comfortably circle in the habitable zone of a sun-like star is digitally illustrated. For the first time NASA's Kepler mission has confirmed a planet to orbit in a star's habitable zone; the region around a star, where liquid water, a requirement for life on Earth, could persist. The planet is 2.4 times the size of Earth, making it the smallest yet found to orbit in the middle of the habit. Clouds could exist in this earth's atmosphere, as the artist's interpretive illustration depicts. (Photo Illustration by Ames/JPL-Caltech/NASA via Getty Images)
In this handout illustration made available on December 5, 2011 by NASA, a diagram compares our own solar system to Kepler-22, a star system containing the first 'habitable zone' planet discovered by NASA's Kepler mission. The habitable zone is the sweet spot around a star where temperatures are right for water to exist in its liquid form. Liquid water is essential for life on Earth. The diagram displays an artist's rendering of the planet comfortably orbiting within the habitable zone, similar to where Earth circles the sun. Kepler-22b has a yearly orbit of 289 days. The planet is the smallest known to orbit in the middle of the habitable zone of a sun-like star and is about 2.4 times the size of Earth. (Photo Illustration by Ames/JPL-Caltech/NASA via Getty Images)
Artist's conception released by NASA of extrasolar planet HD 209458 b, also known as Osiris, orbiting its star in the constellation Pegasus, some 150 light years from Earth's solar system. Scientists have used an infrared spectrum -- the first ever obtained for an extrasolar planet -- to analyze Osiris' atmosphere, which is said to contain dust but no water. The planet's surface temperature is more than 700 Celsius (1330 Fahrenheit).'
Picture released 04 October 2006 by the European Space Agency shows an artist's impression of a Jupiter-sized planet passing in front of its parent star. Such events are called transits. When the planet transits the star, the star's apparent brightness drops by a few percent for a short period. Through this technique, astronomers can use the Hubble Space Telescope to search for planets across the galaxy by measuring periodic changes in a star's luminosity. The first class of exoplanets found by this technique are the so-called 'hot Jupiters,' which are so close to their stars they complete an orbit within days, or even hours. A seam of stars at the centre of the Milky Way has shown astronomers that an entirely new class of planets closely orbiting distant suns is waiting to be explored, according to a paper published 04 October 2006. An international team of astronomers, using a camera aboard NASA's Hubble telescope, delved into a zone of the Milky Way known as the 'galactic bulge', thus called because it is rich in stars and in the gas and dust which go to make up stars and planets. The finding opens up a new area of investigation for space scientists probing extrasolar planets - planets that orbit stars other than our own. AFP PHOTO NASA/ESA/K. SAHU (STScI) AND THE SWEEPS SCIENCE TEAM
Picture released 04 October 2006 by the European Space Agency shows an artist's impression of a unique type of exoplanet discovered with the Hubble Space Telescope. This image presents a purely speculative view of what such a 'hot Jupiter' (word dedicated to planets so close to their stars with such short orbital periods) might look like. A seam of stars at the centre of the Milky Way has shown astronomers that an entirely new class of planets closely orbiting distant suns is waiting to be explored, according to a paper published 04 October 2006. An international team of astronomers, using a camera aboard NASA's Hubble telescope, delved into a zone of the Milky Way known as the 'galactic bulge', thus called because it is rich in stars and in the gas and dust which go to make up stars and planets. The finding opens up a new area of investigation for space scientists probing extrasolar planets - planets that orbit stars other than our own. AFP PHOTO NASA/ESA/K. SAHU (STScI) AND THE SWEEPS SCIENCE TEAM
Scientist have found a new potentially habitable planet.
From the Spitzer Science Center. While astronomers have identified over 500 planets around other stars, they're all too small and distant to fill even a single pixel in our most powerful telescopes. That's why science must rely on art to help us imagine these strange new worlds. From Spitzer Space Telescope. Even without pictures of these exoplanets, astronomers have learned many things that can be illustrated in artwork. For instance, measurements of the temperatures of many "Hot Jupiters," massive worlds orbiting very close to their stars, hint that their atmospheres may be as dark as soot, glowing only from their own heat. While "Hot Jupiters" would be relatively dark in visible light, compared to their stars, their brightness is proportionally much greater in the infrared. Illustrating this dramatic contrast change helps explain why the infrared eye of NASA's Spitzer Space Telescope plays a key role in studying exoplanets. As our understanding evolves, so must the artwork. Astronomers found a blazing hot spot on the exoplanet Upsilon Andromedae b that at first, appeared to face towards its star. More data has revealed that the hottest area is actually strangely rotated almost 90 degrees away, near the day/night terminator. WASP 12b is as hot as the filament in a light bulb, and would be blazing bright to our eyes. Most interestingly, if it proves to have a strongly elliptical orbit, as first thought, calculations show it would be shedding some of its outer atmosphere ...
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