An international team of astronomers have uncovered a treasure trove of exoplanet discoveries in an old NASA Kepler satellite dataset from November 2013.
The researchers tracked two red dwarf star systems with a number of rocky planets calculated to be similar in size or larger than Earth.
The first system of three exoplanets orbits the star K2-239 – a relatively cool star much smaller in mass than our sun.
K2-239 was observed by the Gran Telescopio Canarias (GTC) at the Roque de los Muchachos Observatory on the island of La Palma, in the Canaries.
The red dwarf sits roughly 50 parsecs or 163 light years from the sun and is home to three, Earth-sized rocky planets.
The three exoplanets zoom around their small star with orbital times of 5.2, 7.8 and 10.1 days respectively.
The second red dwarf star, dubbed K2-420, is meanwhile home to a duo of so-called Super-Earth-like planets.
Super-Earths are our home world’s giant stellar cousins – the planets’ mass is higher than that of Earth but lower than those of gaseous ice giants like Neptune.
NASA’s Kepler satellite found three exoplanets around a brown dwarf
It takes the two Super-Earth’s 6.03 and 20.05 days respectively to orbit their star.
We present two new planetary systems found around cool dwarf stars
In a paper presented to the Monthly Notices of the Royal Astronomical Society, the scientists wrote: “We present two new planetary systems found around cool dwarf stars with data from the K2 mission.
“The first system was found in K2-239 (EPIC 248545986), characterised in this work as M3.0V and observed in the 14th campaign of K2.
“It consists of three Earth-size transiting planets with radii of 1.1, 1.0 and 1.1, showing a compact configuration with orbital periods of 5.24, 7.78 and 10.1 days, close to 2:3:4 resonance.”
Could the newly discovered exoplanets host alien life?
It appears as though the planets orbit their brown dwarf stars too closely for any real possibility of alien life.
In order for scientists to get their hopes up about an exoplanet discovery, the planet in question has to sit within the so-called Goldilocks zone, or habitable zone.
The Goldilocks zone is a narrow orbital area neither too close nor too far from the sun but just perfect for liquid water to pool on the planet’s surface.
The researchers estimate the two Super-Earths revolve around a red dwarf burning at temperatures of 3,450 to 3,800 Kelvin in a matter of days.
The exoplanets are too close to their stars to have liquid water and be habitable
The NASA Kepler space telescope combs the Milky Way for signs of exoplanets across space
In comparison, it takes Earth 365 days tor orbit the sun which burns at 5,778 K at a distance of 149.6 million km from the planet.
The astronomers believe temperatures on all five of the exoplanets are tens of degrees higher than those on Earth due to their close proximity to the stars.
The scientists said: “Transiting Earth-size planets induce deeper dimming in the light-curve of low mass stars and stronger radial velocity signals than in more massive stars.
“Temperate planets orbit closer and have shorter orbital periods, so it is easier to detect planets in the habitable zone – orbital range in which a planet’s atmosphere can warm the surface to allow surface liquid water.”
What is the Kepler space telescope?
NASA’s Kepler space telescope is a grand orbital observatory launched in 2009 to comb the stars for signs of Earth-like planets in the deep corners of space.
Named after astronomer Johannes Kepler, the space telescope uses a sensitive photometer to scan portions of the Milky Way.
As of April 12, 2018, the Kepler mission has uncovered and confirmed the existence of 2,343 exoplanets.
NASA said: “The ultimate goal of the Kepler mission is to measure the fraction of stars with Earth-size planets as well as the fraction of stars harbouring Earth-size planets in the Habitable Zone, work which is still in progress by the Kepler Science Office.”