It is the second time a transiting super-Earth has been detected, after the recent discovery of the planet Corot-7b . A transit occurs when the planet's orbit is aligned so that we see it crossing the face of its parent star. The newly discovered planet has a mass about six times that of our terrestrial home and 2.7 times its radius, falling in size between the Earth and the ice giants of the Solar System, Uranus and Neptune.
Although the mass of GJ1214b is similar to that of Corot-7b, its radius is much larger, suggesting that the composition of the two planets must be quite different. While Corot-7b probably has a rocky core and may be covered with lava, astronomers believe that three quarters of GJ1214b is composed of water ice, the rest being made of silicon and iron.
GJ1214b orbits its star once every 38 hours at a distance of only two million kilometres — 70 times closer to its star than the Earth is to the Sun. "Being so close to its host star, the planet must have a surface temperature of about 200 degrees Celsius, too hot for water to be liquid," says David Charbonneau, lead author of the paper reporting the discovery.
When the astronomers compared the measured radius of GJ1214b with theoretical models of planets, they found that the observed radius exceeds the models' predictions: there is something more than the planet's solid surface blocking the star's light — a surrounding atmosphere, 200 km thick. "This atmosphere is much thicker than that of the Earth, so the high pressure and absence of light would rule out life as we know it," says Charbonneau, "but these conditions are still very interesting, as they could allow for some complex chemistry to take place."
"Because the planet is too hot to have kept an atmosphere for long, GJ1214b represents the first opportunity to study a newly formed atmosphere enshrouding a world orbiting another star," adds team member Xavier Bonfils. "Because the planet is so close to us, it will be possible to study its atmosphere even with current facilities."
The planet was first discovered as a transiting object within the MEarth project, which follows about 2000 low-mass stars to look for transits by exoplanets . To confirm the planetary nature of GJ1214b and to obtain its mass (using the so-called Doppler method), the astronomers needed the full precision of the HARPS spectrograph, attached to ESO's 3.6-metre telescope at La Silla. An instrument with unrivalled stability and great precision, HARPS is the world's most successful hunter for small exoplanets.
"This is the second super-Earth exoplanet for which the mass and radius could be obtained, allowing us to determine the density and to infer the inner structure," adds co-author Stephane Udry. "In both cases, data from HARPS was essential to characterise the planet."
"The differences in composition between these two planets are relevant to the quest for habitable worlds," concludes Charbonneau. If super-Earth planets in general are surrounded by an atmosphere similar to that of GJ1214b, they may well be inhospitable to the development of life as we know it on our own planet.
 A super-Earth is defined as a planet between one and ten times the mass of the Earth. An exoplanet is a planet orbiting a star other than the Sun.
 The star GJ1214 is five times smaller than our Sun and intrinsically three hundred times less bright.
 Corot-7b is the smallest and fastest-orbiting exoplanet known and has a density quite similar to the Earth's, suggesting a solid, rocky world. Discovered by the CoRoT satellite as a transiting object, its true nature was revealed by HARPS (ESO 33/09).
 The MEarth project uses an armada of eight small telescopes each with a diameter of 40 cm, located on top of Mount Hopkins, Arizona, USA. 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. 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 that is detectable from the ground.
This research was presented in a paper appearing this week in Nature ("A Super-Earth Transiting a Nearby Low-Mass Star", by David Charbonneau et al.).
The team is composed of David Charbonneau, Zachory K. Berta, Jonathan Irwin, Christopher J. Burke, Philip Nutzman, Lars Buchhave, David W. Latham, Ruth A. Murray-Clay, Matthew J. Holman, and Emilio E. Falco (Harvard-Smithsonian Center for Astrophysics, Cambridge, USA), Christophe Lovis, Stephane Udry, Didier Queloz, Francesco Pepe, and Michel Mayor (Observatoire de l'Université de Genève, Switzerland), Xavier Bonfils, Xavier Delfosse, and Thierry Forveille (University Joseph Fourier — Grenoble 1/CNRS, LOAG, Grenoble, France), and Joshua N. Winn (Kavli Institute for Astrophysics and Space Research, MIT, Cambridge, USA).
ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world's most advanced visible-light astronomical observatory, and VISTA, the world's largest survey telescope. ESO is the European partner of a revolutionary astronomical telescope ALMA, the largest astronomical project in existence. ESO is currently planning a 42-metre European Extremely Large optical/near-infrared Telescope, the E-ELT, which will become "the world's biggest eye on the sky".
- More info: Exoplanet Media Kit: http://www.eso.org/outreach/products/publ/brochures/pdf/exoplanet_lowres.pdf
Dr. Henri Boffin | EurekAlert!
New NASA study improves search for habitable worlds
20.10.2017 | NASA/Goddard Space Flight Center
Physics boosts artificial intelligence methods
19.10.2017 | California Institute of Technology
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
17.10.2017 | Event News
10.10.2017 | Event News
10.10.2017 | Event News
20.10.2017 | Information Technology
20.10.2017 | Materials Sciences
20.10.2017 | Interdisciplinary Research