Super-Earth Alien Planet Spotted by Ground-Based Telescope, a First 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 stars 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 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 planets size and position around a sunlike star make it similar to planets that might support life, researchers say. The planets detection with the Nordic telescope shows that observatories on the ground could use whats 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 wont be able to follow up on all of them. Future ground-based instrumentation will be key, and this study shows it can be done, said Mercedes Lopez-Morales, a researcher at the Harvard-Smithsonian Center for Astrophysics (CfA). 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. Detecting such subtle changes is difficult for telescopes on the ground because of the blurring effect of Earths atmosphere. Space-based telescopes escape this problem completely, but technologies exist to help ground-based telescopes adapt to this challenge. Daytime temperatures on 55 Cancri e likely reach higher than 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. With this result, we are also closing in on the detection of the atmospheres of small planets with ground-based telescopes, Lopez-Morales said. We are slowly paving the way toward the detection of biosignatures in Earthlike planets around nearby stars. Another super-Earth called GJ 1214b, located 42 light-years from Earth, was previously detected by ground-based telescopes using the same transit method, researchers said. GJ 1214b is larger than 55 Cancri e, with a diameter about 2.7 times that of Earth and a mass seven times greater than Earths. GJ 1214b orbits a red dwarf, a class of stars that are significantly smaller and dimmer than Earths sun. 55 Cancri e was the first super-Earth detected around a main sequence star, similar to our sun. After its initial detection, 55 Cancri e also became the first super-Earth seen by NASAs 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 NASAs Kepler Space Telescope, the space agencys 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 Agencys Planetary Transits and Oscillations of stars (PLATO) mission, planned for launch in 2024, will also search for a large number of exoplanets. Our observations show that we can detect the transits of small planets around sunlike stars using ground-based telescopes, Ernst de Mooij of Queens University Belfast and lead author of the study, said in the statement from CfA. This is especially important because upcoming space missions, such as TESS and PLATO, should find many small planets around bright stars, and we will want to follow up the discoveries with ground-based instruments.
Posted on: Sat, 03 Jan 2015 01:56:20 +0000
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