Super-Earth in Six-Planet System May Be Just Right to Support Life

A new super-Earth planet that may have an Earth-like climate and be just right to support life has been discovered around a nearby star by an international team of astronomers, led by Mikko Tuomi, University of Hertfordshire, and Guillem Anglada-Escude, University of Goettingen.
The new super-Earth planet exists in the habitable zone of a nearby star and is part of a six-planet system. The system was previously thought to contain three planets in orbits too close to the star to support liquid water. By avoiding fake signals caused by stellar activity, the researchers have identified three new super-Earth planet candidates also in orbit.

Mikko Tuomi said: “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.”

Of the new planets, the one of greatest interest is the one with the outermost orbit from the star — with a mass at least seven times of the Earth. Its orbit around the host star is at a similar distance to Earth’s orbit around our Sun, so it receives a similar amount of energy from the star as the Earth receives from the Sun – increasing the probability of it being habitable. This is where the presence of liquid water and stable atmospheres to support life is possible and, more importantly, the planet is likely to be rotating on its own axis as it orbits around the star creating a daytime and night-time effect on the planet which would be better at creating an Earth-like environment.

Guillem Angla-Escude said: “The star HD 40307, is a perfectly quiet old dwarf star, so there is no reason why such a planet could not sustain an Earth-like climate.”

Hugh Jones, University of Hertfordshire, added: “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.”

Earlier this year, the Kepler spacecraft found a planet with a similar orbit. However, Kepler 22d is located 600 light years from Earth, whereas this new super-Earth planet known as HD 40307g is much closer being located at forty-two light years from Earth.

Mikko Tuomi carried out this work as a member of the European science network RoPACS (Rocky Planets Around Cool Stars) – an initiative with a research focus on the search for planets around cool stars. RoPACS has pan-European membership and is led from the University of Hertfordshire by David Pinfield, who commented: “Discoveries like this are really exciting, and such systems will be natural targets for the next generation of large telescopes, both on the ground and in space.”

Text, images and videos:
http://star-www.herts.ac.uk/~hraj/hd40307/

Contact:
Julie Cooper
01707 284095
Email: j.cooper5@herts.ac.uk

Additional Information on the Images and text:

HD40307_MedRes.wmv (and a lower resolution version HD40307_LowRes.wmv)

This shows a fly-through video of the HD 40307 system. The video is physically realistic though the rings and atmospheres are speculative and are not detected or constrained by this work. Credit: Guillem Anglada-Escude at the University of Gottingen.

super_earth_HZ.png

This artist’s impression shows HD40307g in the foreground (on the left hand side), with its host star HD40307 and two other planets in the system (on the right-hand side). The depicted atmosphere and continents are not detected or constrained by this work. Credit: J. Pinfield, for the RoPACS network at the University of Hertfordshire.

The paper “Habitable-zone super-Earth candidate in a six-planet system around the K2.5V star HD 40307” is accepted for publication in the journal Astronomy & Astrophysics and is available at
http://star-www.herts.ac.uk/~hraj/hd40307/hd40307_final.pdf

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About the Research Team

The international research team was led by Mikko Tuomi (Hertfordshire University) and Guillem Anglada-Escude (University of Goettingen).  The presented work also contains significant contributions from E. Gerlach (Technical University of Dresden), Hugh R. A. Jones (University of Hertfordshire), A. Reiners (University of Goettingen), S. Vogt, E. Rivera (UCO-Lick Observatory) and R. P. Butler (Carnegie Institution for Science).

RoPACS (Rocky Planets Around Cool Stars) is a Marie Curie Initial Training Network funded by the European Commissions Seventh Framework Programme.
 
The research of G. Anglada-Escude is being supported by the German Ministry of Education and Research under 05A11MG3. E. Gerlach is supported by the DFG research unit FOR584. A. Reiners acknowledges research funding from DFG grant RE1664/9-1. S. Vogt gratefully acknowledges support from NSF grant AST-0307493 and R. P. Butler thanks the Carnegie Institution for Science for providing continued support to his research activities.

The result is based on reanalysis of spectra taken with the HARPS spectrograph and available through the European Southern Observatory public archive. This work would have not been possible without the ESO public data policies and the excellent work of the ESO Software development division and the ESO Science Archive Facility.

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