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Remote Sensing Of Small Exoplanets Using Ground-Based Telescopes
April Flowers for redOrbit.com – Your Universe Online
An international group of astronomers is the first to measure the passing of a super-Earth exoplanet in front of a bright, nearby Sun-like star using a ground based telescope
The study, published in The Astrophysical Journal Letters , reveals that the transit of 55 Cancri e is the shallowest detected from the ground to date. Detecting an exoplanet’s transit is the first step to analyzing the atmosphere, therefore, these findings have important implications for characterizing the many small planets which upcoming space missions are expected to discover in the next few years.
The researchers used the 2.5-meter Nordic Optical Telescope at the Observatorio del Roque de los Muchachos on the Island of La Palma in the Canary Islands. Prior to this study, observations of this planet’s transit relied on space-borne telescopes.
Just 40 light-years from our own planet, the host star 55 Cancri is visible to the naked eye. The planet, 55 Cancri e, crosses the host planet during its transit and blocks a tiny fraction of the star’s light. The light is dimmed by 0.05 percent for almost two hours, which reveals that the exoplanet is roughly twice the size of Earth — approximately 16,000 miles in diameter.
“Our observations show that we can detect the transits of small planets around Sun-like stars using ground-based telescopes,” said Ernst de Mooij of Queen’s University Belfast in the United Kingdom. “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.”
NASA’s TESS (Transiting Exoplanet Survey Satellite) mission is scheduled to launch in 2017. The European Space Agency’s (ESA) PLAnetary Transits and Observations (PLATO) mission is scheduled for 2024. Both missions will search for transiting exoplanets around nearby bright stars.
“With this result we are also closing in on the detection of the atmospheres of small planets with ground-based telescopes,” said Mercedes Lopez-Morales of the Harvard-Smithsonian Center for Astrophysics (CfA). “We are slowly paving the way toward the detection of bio-signatures in Earth-like planets around nearby stars.”
“It’s remarkable what we can do by pushing the limits of existing telescopes and instruments, despite the complications posed by the Earth’s own turbulent atmosphere,” said Ray Jayawardhana of York University in Canada. “Remote sensing across tens of light-years isn’t easy, but it can be done with the right technique and a bit of ingenuity.”
A super-Earth is any exoplanet that has a mass greater than the Earth’s, but smaller than our solar system’s gas giants. 55 Cancri e fits that bill, being about twice as big and eight times as massive as our own planet. Those are not the only differences, however. 55 Cancri e is the innermost of five planets in the system, with a period of 18 hours. The surface, dayside temperature can reach upwards of 3,100 degrees Fahrenheit, which is hot enough to melt metal. Conditions on the planet, which was identified over a decade ago through radial velocity measurements, are inhospitable to life.
Prior to this study, only one other super-Earth transit had been observed with ground-based telescopes — that of GJ 1214b, which circles a red dwarf star. Ground-based observations are hindered by the roiling air of Earth’s atmosphere. The new study, however, suggests the possibility of characterizing dozens of super-Earths likely to be revealed by upcoming surveys.
“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,” added Lopez-Morales.
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Source: http://www.redorbit.com/news/space/1113290555/remote-sensing-of-small-exoplanets-using-ground-based-telescopes-120214/
