|An artist’s conception shows the size of super-Earth 55 Cancri e compared to Earth. A ground-based telescope in Spain was able to identify 55 Cancri e, which suggests that telescopes on the ground help in the search for habitable planets around other stars.|
Excerpt from csmonitor.com
A telescope on the Canary Islands has spotted a planet twice the size of Earth as it passed in front of a star, the first time a planet in this category has been detected by a ground-based telescope.
Finding Earthlike planets beyond our solar system has largely been the work of space-based telescopes, but new observations from a remote island suggest that could change.
The Nordic Optical Telescope on La Palma — one of the Canary Islands off the west coast of Africa — observed 55 Cancri e, a planet twice the size of Earth, as it passed in front of its parent star and caused a dip in the star’s brightness, according to a new study. This is the first time a planet in this “super-Earth” size category orbiting a sunlike star has been observed by a ground-based telescope using this detection method, the researchers say.
First identified in 2004 by a space-based telescope, 55 Cancri e has a diameter of about 16,000 miles (26,000 kilometers) — about twice that of Earth. The alien world is eight times as massive as Earth, making it a so-called super-Earth, a planet more massive than Earth but significantly smaller than gas giants like Neptune and Uranus. While not habitable, the planet’s size and position around a sunlike star make it similar to planets that might support life, researchers say.
The planet’s detection with the Nordic telescope shows that observatories on the ground could use what’s called the transit method — watching for dips in the brightness of a star to indicate a planet passing in front of it — to assist space-based telescopes in follow-up studies of super-Earths or Earthlike exoplanets, scientists say.
Nearly 2,000 exoplanets have now been confirmed, and upcoming exoplanet searches promise to expand that catalog.
“We expect these surveys to find so many nearby terrestrial worlds that space telescopes simply won’t be able to follow up on all of them. Future ground-based instrumentation will be key, and this study shows it can be done,” Mercedes Lopez-Morales, co-author of the new research and a researcher at the Harvard-Smithsonian Center for Astrophysics (CfA), said in a statement.
Five exoplanets orbit the star 55 Cancri, which is located 40 light-years from Earth and is visible to the naked eye. The closest-orbiting of those five is 55 Cancri e, which completes one lap around the star every 18 hours. When the planet passes between Earth and the parent star, 55 Cancri appears to dim by 1/2000th (or 0.05 percent) for almost 2 hours, researchers said.
Daytime temperatures on 55 Cancri e likely reach higher than 3,100 degrees Fahrenheit (1,700 degrees Celsius) — hot enough to melt metal and much too hot to support life. But scientists involved with the study say this approach could help characterize the atmosphere of more hospitable Earthlike or super-Earth planets.
After its initial detection, 55 Cancri e also became the first super-Earth seen by NASA’s Spitzer Space Telescope, using light directly from the planet. Thus, it has now served twice as a litmus test for super-Earth detection methods.
In addition to the wealth of planets identified by NASA’s Kepler Space Telescope, the space agency’s Transiting Exoplanet Survey Satellite (TESS) mission, scheduled for launch in 2017, is expected to “discover thousands of exoplanets in orbit around the brightest stars in the sky,” according to the TESS website. The European Space Agency’s Planetary Transits and Oscillations of stars (PLATO) mission, planned for launch in 2024, will also search for a large number of exoplanets.