Astronomers Detect Super-Earth Using Ground-Based Telescope

Categories: New Planets News Brief

This artist's conception shows the super-Earth 55 Cancri e (right) compared to the Earth (left). Credit: NASA/JPL

This artist’s conception shows the super-Earth 55 Cancri e (right) compared to the Earth (left). Credit: NASA/JPL

For the first time, a team of astronomers has detected a super-Earth around a Sun-like star using a ground-based telescope.

Using the Nordic Optical Telescope in La Palma, Spain, the international team measured two transits of the exoplanet 55 Cancri e, in 2013 and 2014. The findings will be published in the Astrophysical Journal Letters. (A pre-print is available here.)

The super-Earth was first detected ten years ago with radial velocity measurements, and was later confirmed using the MOST and Spritzer space telescopes.

Super-Earths are relatively small and harder to detect than large, Jupiter-size planets. “We’ve now shown that we can study these planets from the ground,” says lead author Dr. Ernst de Mooij of Queen’s University in Belfast, UK.

Ground-based telescopes have several advantages over space-based telescopes.

The Nordic Optical Telescope in La Palma, Spain. Credit: Diana Juncher

The Nordic Optical Telescope in La Palma, Spain. Credit: Diana Juncher

“They are more numerous and there is a wider variety of instruments available,” de Mooij says. “In principle, you can study more planets and in more details. But that’s if you can correct for the Earth’s atmosphere, which makes observations from the ground more difficult.”

The team’s success bodes well for characterizing the many small terrestrial planets likely to be revealed by upcoming space missions.

NASA’s TESS mission, scheduled for launch in 2017, will monitor more than half a million stars over two years and is expected to find more than 3,000 new exoplanets. The PLATO mission, to be launched by the European Space Agency in 2024, will identify thousands of planetary systems around up to a million stars.

“Our results highlight the great potential of using ground-based telescopes for follow-up studies,” de Mooij says.

The planet 55 Cancri e orbits a Sun-like star 40 light-years away from Earth in the constellation of Cancer. It is twice as large and eight times as massive as Earth. It is the innermost of five planets in the 55 Cancri system, and its dayside temperature reaches over 1,700° Celsius (more than 3,092 Fahrenheit), hot enough to melt metal. The planet takes 18 hours to revolve around its star.

Until now, one other super-Earth, GJ 1214b, had been detected from the ground. But the planet orbits a smaller star, a red dwarf.

Artist rendition of the Transiting Exoplanet Survey Satellite, or TESS. Credit: NASA

Artist rendition of the Transiting Exoplanet Survey Satellite, or TESS. Credit: NASA

The upcoming surveys will mainly target larger Sun-like stars. To detect exoplanets, scientists measure the dip in brightness as the planet crosses in front of its star. Because less light is blocked when planets cross larger stars, the signal is much weaker.

So the team’s success with 55 Cancri e raises the prospects of characterizing many worlds likely to be revealed by the upcoming missions.

The team now plans to study the planet’s atmosphere. One goal with the characterization of exoplanet atmospheres is the detection of potential bio-signatures. For instance, the combination of unstable elements like as oxygen and methane could be indicative of a vibrant biosphere.

“But again, that’s only if you’re looking for Earth-like life,” de Mooij says. “No one knows what life based on different principles might look like.”