A new “super-Earth” has been discovered and added to the growing list of potentially habitable exoplanets, it was announced yesterday. The planet, HD 40307g, orbits the star HD 40307, which is about three-quarters the size of the Sun and 42 light years away, in the constellation Pictor.
HD 40307g is about seven times as massive as Earth and orbits within the “habitable zone” of its star, meaning that it could possibly have liquid water on its surface. It is one of six known planets in this planetary system and is the farthest one out from the star, taking about 200 days to complete an orbit.
According to Mikko Tuomi of the University of Hertfordshire, “We pioneered new data analysis techniques including the use of the wavelength as a filter to reduce the influence of activity on the signal from this star. This significantly increased our sensitivity and enabled us to reveal three new super-Earth planets around the star known as HD 40307, making it into a six-planet system.”
The physical composition of HD 40307g isn’t known yet, but if it is a rocky world, as seems likely, it would be at just the right distance where temperatures could allow liquid water to exist on its surface. Super-Earths are generally thought to be mostly rocky planets like Earth, but up to a few times larger and smaller than ice giants like Neptune or Uranus.
As astronomer Hugh Jones of the University of Hertfordshire in England explains, “It’s the position of the planet in its orbit that’s important. The planet orbits close enough to its sunlike star that it could have similar temperatures to Earth. The planet is not putting the same face to its star all the time, like the moon, so it should have cycles of day and night.” Jones is a co-author of the research paper to be published in an upcoming issue of Astronomy & Astrophysics.
Hugh Jones of the University of Hertfordshire, adds: “The longer orbit of the new planet means that its climate and atmosphere may be just right to support life. Just as Goldilocks liked her porridge to be neither too hot nor too cold but just right, this planet or indeed any moons that is has lie in an orbit comparable to Earth, increasing the probability of it being habitable.”
The current list of known potentially habitable exoplanets can be seen in The Habitable Exoplanets Catalog. This list will continue to grow as more smaller planets like these are discovered. The number of confirmed exoplanets so far is now in the hundreds and additional candidates (awaiting confirmation) are in the thousands; only planets which may possibly be suitable for life (“as we know it”) are currently listed in the catalog.
The original press release is available here.