Scientists Discover Star With Three Earth-Sized Planets

By Chris Jasurek

The Instituto de Astrofísica de Canarias (IAC) and the University of Oviedo announced their latest discovery: a star system with three planets about the same size as planet Earth.

The June 6 announcement by IAC is based on data collected from NASA’s Kepler satellite. Two planetary systems were discovered in the same general area of space.

The first system is located in the constellation Sextant, about 160 light-years from Earth. Named K2-239, this star is a red dwarf, only about half as hot as the Sun. Data from the Gran Telescopio Canarias reveals it to be an M3V type, with about a third of the mass and one percent of the light output of the Sun.

The three rocky planets are all about the same diameter as the earth. Researchers say that even though the star is cooler than the Sun, the temperatures on the surfaces of these planets are probably some tens of degrees higher than the average surface temperature on Earth, because the planets are much closer to their sun.

This is important to scientists because it puts these planets in what is called “the habitable zone”—a range of conditions which allow liquid water to exist on the planet’s surface (pdf).

These planets are traveling a lot faster than Earth. Where a trip around the Sun takes Earth 365 days, the “years” of these three planets range between 5.24 and 10.1 days.

The second system discovered is called K2-240. It is also based around a red dwarf, and has two rocky planets, each about twice the size of the Earth. These two planets orbit their star in 6.03 and 20.5 days.

These planets will be investigated further by the new James Webb space telescope, which is scheduled to launch in 2020.

The research team, led by Javier de Cos at the University of Oviedo, and Rafael Rebolo at the IAC, included staff from the University of Geneva and the Gran Telescopio Canarias (GTC).

These scientists detected the planets by observing how they blocked the light of their suns as they orbited—the eclipse of their stars from the point of view of Earth.

By calculating how the passing planets affected the transmitted light, these scientists were able to gather data on the them, which not even the most powerful telescopes can see directly.