Waterworld

This week, an international team of scientists announced the discovery of a new type of exoplanet, or planet outside our own solar system. The results were published earlier this month in The Astrophysical Journal.

The planet, which is formally known as GJ1214b, is believed to be a massive, steamy planet, with an estimated temperature of 232 degrees Celsius (450 degrees Fahrenheit). The possibly water-logged planet is located about 40 light-years away from Earth, and was discovered in 2009. Astronomers have calculated its diameter to be 2.7 times bigger than Earth's, and that its mass is nearly seven times Earth's.

"GJ1214b is like no planet we know of," said Zachory Berta of the Harvard-Smithsonian Center for Astrophysics, in a statement. "A huge fraction of its mass is made up of water."

Since the team has been able to calculate the planet's mass and size, it is very easy to calculate its average density -- a figure of about 2 grams per cubic centimeter. Earth, by comparison is about 5.5 grams per cubic centimeter, while liquid water is about one gram per cubic centimeter, suggesting that GJ1214b is closer to water than Earth's rocky nature.

But that could also mean that the structure of the exoplanet may be unlike any other known planet.

"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 added.

Planetary scientists suspect that GJ1214b was formed far away from its star, gathering into a ball of ice, but then was drawn in closer due to gravitational forces.

Water or clouds?

However, not all scientists are convinced that the data show that the planet definitively contains water.

Frederic Pont, a senior lecturer in astrophysics at the University of Exeter in the United Kingdom, notes that the authors of the paper described some details of which a water-heavy atmosphere is only one possibility to explain their observed data, “the other being clouds.”

“Such clouds are not too unlikely, actually they are observed in one of only two cases were we can do these kind of observations in detail, HD 189733b,” Pont wrote in an e-mail sent to DW. “The authors explain that in the case of GJ1214 the clouds would need to be made of bigger particles than for HD 189733b, but that's not particularly implausible. Also, note that a water-vapor atmosphere is an inference. What the data requires is an atmosphere made of something heavier than hydrogen, the water hypothesis comes from theoretical arguments.”

That being said, further study may throw a wrench into existing planetary formation theory.

“If the atmosphere of this planet contains no hydrogen, then its size becomes very difficult to explain,” Pont added. “It seems a bit too large for its mass to be devoid of an hydrogen atmosphere. So that would be a challenge for planet formation and structure models.”

Still, scientists who study exoplanets have been excited by these new results, particularly given that the planet was discovered and observed with the Hubble Space Telescope - a less sophisticated tool given that it's been in use for over two decades now.

Since the first discovery of an exoplanet in 1992, scientists have now found more than 700 such planets. The goal, of course, remains to find an Earth-like planet with life that resembles something that we are familiar with, and can understand.

“However, planets like our Earth are difficult to find - so finding water on a planet that is a bit more massive than Earth is naturally going to happen first,” wrote Anders Johansen, a lecturer in astronomy at Lund University in Sweden, in an e-mail sent to DW. “In the future we may see detection of water on many other massive planets. Whether such planets can host life it not known. That is going to be an important question for astrobiologists to answer.”

Author: Cyrus Farivar
Editor: Stuart Tiffen