By John Kerr 25/08/2016


The astronomy world is abuzz following the discovery of a planet in a neighboring star system, sitting in just the right position to – theoretically – host liquid water. 

It is still over four light years away, but the planet Proxima b in the Alpha Centauri system is the closest Earth-like planet we’ve found. The discovery is published today in the journal Nature.

The planet has an estimated mass of at least 1.3 times that of the Earth and its orbit sits right in the ‘Goldilocks Zone‘ where the temperature is within the range where water could theoretically be liquid on its surface.

Read more about the discovery of Proxima b on Scimex.org.

With liquid water being one of the key components of life – as we know it – there has been understandable excitement about the discovery.

“Many exoplanets have been found and many more will be found, but searching for the closest potential Earth-analogue and succeeding has been the experience of a lifetime for all of us,” said lead author Guillem Anglada-Escudé, from Queen Mary University of London.

“Many people’s stories and efforts have converged on this discovery. The result is also a tribute to all of them. The search for life on Proxima b comes next…”

Is there life on Proxima b?

Two separate studies, which have just been submitted for publication to the Astronomy & Astrophysics journal, take what little is known about Proxima b to examine possibilities of life-supporting atmosphere and water on the planet.

Proxima b is exposed to 60 times more high-energy radiation than the Earth, and may have lost its atmosphere and water from the planet’s surface, becoming a dry, sterile rock. Or it may have been able to keep most of its atmosphere and preserve liquid water on the surface and therefore be hospitable to life as we know it. Both possibilities are still open according to the information currently available about the research:

“Much research is still due, but the studies conclude that the presence of liquid water on the surface today cannot be ruled out and thus Proxima b can be considered a viable candidate habitable planet.”

This artist’s impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image between the planet and Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface.
This artist’s impression shows the planet Proxima b orbiting the red dwarf star Proxima Centauri, the closest star to the Solar System. Credit: ESO/M. Kornmesser

 

In the coming centuries, robotic exploration of Proxima b may become possible. “Proxima Centauri will exist for several hundreds or thousands of times longer than the Sun,” says German astronomer Artie Hatzes in an accompanying News & Views Nature article. “Any life on the planet could still be evolving long after our Sun has died.”

New Zealand researchers react

Professor Richard Easther, cosmologist and head of the Physics Department, University of Auckland, described Proxima b as “a fascinating discovery.”

“It extends the range of planets we have seen in the universe, and marks the detection of a roughly Earth-sized planet in the ‘Goldilocks zone’ of another star — one that is close enough to its sun that it would not be frozen solid, but not so close that water would boil,” he told the Science Media Center.

“The excitement about planets that can support water is that water is one of the key ingredients for ‘life as we know it’. That said, this planet is very different from the Earth; the host star Proxima Centauri is a red dwarf, and a much fainter star than the sun.”

This infographic compares the orbit of the planet around Proxima Centauri (Proxima b) with the same region of the Solar System. Proxima Centauri is smaller and cooler than the Sun and the planet orbits much closer to its star than Mercury. As a result it lies well within the habitable zone, where liquid water can exist on the planet’s surface. : Credit: ESO/M. Kornmesser/G. Coleman
This infographic compares the orbit of the planet around Proxima Centauri (Proxima b) with the same region of the Solar System. Proxima Centauri is smaller and cooler than the Sun and the planet orbits much closer to its star than Mercury. As a result it lies well within the habitable zone, where liquid water can exist on the planet’s surface. Credit: ESO/M. Kornmesser/G. Coleman

 

Dr Nicholas Rattenbury, also from the University of Auckland Physics Department, welcomed the discovery but warned that more research would be needed to confirm the exact mass of the planet.

“Ideally we’d like to see transit observations of the planet — to see if Proxima b passes between us and its host star Proxima Centauri,” he said. “This would cause a dip in the amount of light we see coming from Proxima Centauri, and would give us the radius of the planet. More importantly, such transit observations would get rid of that pesky word “minimum” in front of the phrase in the paper that the planet has a “minimum mass of about 1.3 Earth masses.”

“As it stands, the planet could be even more massive than Jupiter — and correspondingly be a planet very different to Earth — we simply don’t know yet. Further observations will hopefully resolve this issue.

“For now, it is an exciting discovery, mainly because we have found evidence of a planet orbiting the star nearest to our own Sun.”

“If we choose to design a space probe mission to explore other planetary systems, then the Proxima Centauri system no doubt will be top of the list of systems to investigate.”

Featured Image: Anglada-Escudé et al. have discovered an Earth-like planet in orbit around the closest star to our Sun, Proxima Centauri. The planet’s surface temperature should allow it to support liquid water, and its mass suggests that it might have a rocky surface. In this artist’s impression, the planet is assumed to have an Earth-like atmosphere. Credit: ESO/M. Kornmesser