July 2, 2013
New Super-Earth Discovered In Our Galactic Neighborhood
Brett Smith for redOrbit.com - Your Universe Online
Using the Canadian Microvariability & Oscillations of Stars (MOST) telescope, an international team of researchers has uncovered new details about a relatively close Earth-sized planet, according to a new report in the Astrophysical Journal Letters.
The star, known as HD 97658, sits just 70 light-years away from Earth and can almost be seen with the naked eye. In 2011, astronomers first discovered a planet orbiting the nearby star, known as an exoplanet. However, they weren't able to determine anything about its size.
To learn more about the planet, the astronomers used MOST to watch for its transit, when the planet passes in front of its star relative to our point-of-view. A transiting planet slightly reduces the amount of light being sent to Earth and the slight dimming can be detected and analyzed using space telescopes like MOST.
Astronomers first thought they spotted a transition in the HD 97658 system in 2011, which eventually proved to be a false alarm. However, astronomers on the project persisted and were able to prove the presence of a planet in the year's last possible viewing window.
The following year, MOST observed the system again - gleaning even more details from the planet's transits. These 2012 observations allowed the team to calculate the planet's approximate size and mass.
"Measuring an exoplanet's size and mass leads to a determination of its density, which in turn allows astronomers to say something about its composition," said study co-author Diana Dragomir, a postdoctoral astronomer with UC Santa Barbara's Las Cumbres Observatory Global Telescope (LCOGT) network. "Measuring the properties of super-Earths in particular tells us whether they are mainly rocky, water-rich, mini gas giants, or something entirely different."
The team determined the average density of the exoplanet, dubbed HD 97658b, is about four grams per cubic centimeter, or about 70 percent of the average density of our planet. The researchers said that finding was significant as it meant the exoplanet's gravity could hold onto a thick atmosphere.
However, because the planet was found to orbit its sun every 9.5 days, it's most likely too close to HD 97658 to host intelligent life as we know it. Whenever astronomers discover an Earth-like planet, they look to see if it orbits in the so-called Habitable Zone. Also referred to as the Goldilocks Zone, when a planetâ€™s distance from its sun is just right, it is capable of holding liquid water oceans like the ones that gave birth to life on Earth.
Despite not finding an exoplanet orbiting in the ideal radius from its sun, researchers said they were still able to cull significant information from their discovery.
"This discovery adds to the still small sample of transiting super-Earths around bright stars," said Dragomir. "In addition, it has a longer period than many known transiting exoplanets around bright stars, including 55 Cnc e, the only other super-Earth in this category. The longer period means it is cooler than many closer-in exoplanets, so studying HD 97658b's properties is part of the progression toward understanding what exoplanets in the habitable zone might be like."