Astronomers find super-Earth using amateur, off-the-shelf technology

December 16, 2009

Astronomers announced today that they have discovered a "super-Earth" orbiting a red dwarf star 40 light-years from Earth. They found the distant planet with a small fleet of ground-based telescopes no larger than those many amateur astronomers have in their backyards. Although the super-Earth is too hot to sustain life, the discovery shows that current, ground-based technologies are capable of finding almost-Earth-sized planets in warm, life-friendly orbits.

The discovery is being published in the December 17 issue of the journal Nature.

A super-Earth is defined as a planet between one and ten times the mass of the Earth. The newfound world, GJ1214b, is about 6.5 times as massive as the Earth. Its host star, GJ1214, is a small, red type M star about one-fifth the size of the Sun. It has a surface temperature of only about 4,900 degrees F and a luminosity only three-thousandths as bright as the Sun.

GJ1214b orbits its star once every 38 hours at a distance of only 1.3 million miles. Astronomers estimate the planet's temperature to be about 400 degrees Fahrenheit. Although warm as an oven, it is still cooler than any other known transiting planet because it orbits a very dim star.

Since GJ1214b crosses in front of its star, astronomers were able to measure its radius, which is about 2.7 times that of Earth. This makes GJ1214b one of the two smallest transiting worlds astronomers have discovered (the other being CoRoT-7-b). The resulting density suggests that GJ1214b is composed of about three-fourths water and other ices, and one-fourth rock. There are also tantalizing hints that the planet has a gaseous atmosphere.

"Despite its hot temperature, this appears to be a waterworld," said Zachory Berta, a graduate student at the Harvard-Smithsonian Center for Astrophysics (CfA) who first spotted the hint of the planet among the data. "It is much smaller, cooler, and more Earthlike than any other known exoplanet."

Berta added that some of the planet's water should be in the form of exotic materials like Ice VII (seven) - a crystalline form of water that exists at pressures greater than 20,000 times Earth's sea-level atmosphere.

Astronomers found the new planet using the MEarth (pronounced "mirth") Project - an array of eight identical 16-inch-diameter RC Optical Systems telescopes that monitor a pre-selected list of 2,000 red dwarf stars. Each telescope perches on a highly accurate Software Bisque Paramount and funnels light to an Apogee U42 charge-coupled device (CCD) chip, which many amateurs also use.

"Since we found the super-earth using a small ground-based telescope, this means that anyone else with a similar telescope and a good CCD camera can detect it too. Students around the world can now study this super-earth!" said David Charbonneau of CfA, lead author and head of the MEarth project.

MEarth looks for stars that change brightness. The goal is to find a planet that crosses in front of, or transits, its star. During such a mini-eclipse, the planet blocks a small portion of the star's light, making it dimmer. Using innovative data processing techniques, astronomers can tease out the telltale signal of a transiting planet and distinguish it from "false positives" such as eclipsing double stars.

NASA's Kepler mission also uses transits to look for Earth-sized planets orbiting Sun-like stars. However, such systems dim by only one part in ten thousand. The higher precision required to detect the drop means that such worlds can only be found from space.

In contrast, a super-Earth transiting a small, red dwarf star yields a greater proportional decrease in brightness and a stronger signal detectable from the ground. Astronomers then use instruments like the HARPS (High Accuracy Radial Velocity Planet Searcher) spectrograph at the European Southern Observatory to measure the companion's mass and confirm it is a planet, as they did with this discovery.

When astronomers compared the measured radius of GJ1214b to theoretical models, they found that the observed radius exceeds the model's prediction, even assuming a pure water planet. Something more than the planet's solid surface may be blocking the star's light - specifically, a surrounding atmosphere.

The team also notes that, if it has an atmosphere, those gases are almost certainly not primordial. The star's heat is gradually boiling off the atmosphere. Over the planet's multiple-billion-year lifetime, much of the original atmosphere may have been lost.

The next step for astronomers is to try to directly detect and characterize the atmosphere, which will require a space-based instrument like NASA's Hubble Space Telescope. GJ1214b is only 40 light-years from Earth, within the reach of current observatories.

"Since this planet is so close to Earth, Hubble should be able to detect the atmosphere and determine what it's made of," said Charbonneau. "That will make it the first super-Earth with a confirmed atmosphere - even though that atmosphere probably won?t be hospitable to life as we know it."

Harvard-Smithsonian Center for Astrophysics

Related Atmosphere Articles from Brightsurf:

ALMA shows volcanic impact on Io's atmosphere
New radio images from ALMA show for the first time the direct effect of volcanic activity on the atmosphere of Jupiter's moon Io.

New study detects ringing of the global atmosphere
A ringing bell vibrates simultaneously at a low-pitched fundamental tone and at many higher-pitched overtones, producing a pleasant musical sound. A recent study, just published in the Journal of the Atmospheric Sciences by scientists at Kyoto University and the University of Hawai'i at Mānoa, shows that the Earth's entire atmosphere vibrates in an analogous manner, in a striking confirmation of theories developed by physicists over the last two centuries.

Estuaries are warming at twice the rate of oceans and atmosphere
A 12-year study of 166 estuaries in south-east Australia shows that the waters of lakes, creeks, rivers and lagoons increased 2.16 degrees in temperature and increased acidity.

What makes Saturn's atmosphere so hot
New analysis of data from NASA's Cassini spacecraft found that electric currents, triggered by interactions between solar winds and charged particles from Saturn's moons, spark the auroras and heat the planet's upper atmosphere.

Galactic cosmic rays affect Titan's atmosphere
Planetary scientists using the Atacama Large Millimeter/submillimeter Array (ALMA) revealed the secrets of the atmosphere of Titan, the largest moon of Saturn.

Physics: An ultrafast glimpse of the photochemistry of the atmosphere
Researchers at Ludwig-Maximilians-Universitaet (LMU) in Munich have explored the initial consequences of the interaction of light with molecules on the surface of nanoscopic aerosols.

Using lasers to visualize molecular mysteries in our atmosphere
Molecular interactions between gases and liquids underpin much of our lives, but difficulties in measuring gas-liquid collisions have so far prevented the fundamental exploration of these processes.

The atmosphere of a new ultra hot Jupiter is analyzed
The combination of observations made with the CARMENES spectrograph on the 3.5m telescope at Calar Alto Observatory (Almería), and the HARPS-N spectrograph on the National Galileo Telescope (TNG) at the Roque de los Muchachos Observatory (Garafía, La Palma) has enabled a team from the Instituto de Astrofísica de Canarias (IAC) and from the University of La Laguna (ULL) to reveal new details about this extrasolar planet, which has a surface temperature of around 2000 K.

An exoplanet loses its atmosphere in the form of a tail
A new study, led by scientists from the Instituto de Astrofísica de Canarias (IAC), reveals that the giant exoplanet WASP-69b carries a comet-like tail made up of helium particles escaping from its gravitational field propelled by the ultraviolet radiation of its star.

Iron and titanium in the atmosphere of an exoplanet
Exoplanets can orbit close to their host star. When the host star is much hotter than our sun, then the exoplanet becomes as hot as a star.

Read More: Atmosphere News and Atmosphere Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to