An international research team of scientists may have found a habitable planet at Alpha Centauri, a star very close to the Sun. It could forever change the hunt for “other Earths.”
Although it needs confirmation and is thus only a “candidate planet” for now, researchers believe they have found a “warm Neptune” planet around Alpha Centauri A. The possible discovery was reported recently in the journal Nature Communications and last week more details were revealed of the team’s new method for directly imaging smaller planets in the habitable zone of neighbouring star systems.
Alpha Centauri is the nearest star system to Earth at just 4.37 light-years. It’s a very bright triple star system consisting of three stars: the Sun-like Alpha Centauri A (also called Kentaurus) and Alpha Centauri B (Toliman) stars and a tiny red dwarf star called Proxima Centauri.
Proxima Centauri is known to have planets and is the subject of intense research—and was recently the source of a mystery radio signal— but this is the first time that any planets have been detected around Alpha Centauri A.
Part of a Breakthrough Watch/NEAR (New Earths in the Alpha Centauri Region study, the team uncovered a signal of an exoplanet located in a zone that may offer suitable conditions for life.
The signal was weak—hence the uncertainty—but the team was only able to collect the data because of a new ultra-sensitive technique that could make it easier to find planets around close stars.
MORE FOR YOU
Most exoplanets are found by astronomers looking for dips in a star’s light as a planet transits it, but that only works in star systems that are side-on as seen from Earth.
What scientists really want to be able to do is directly image exoplanets, but so far that technique—using near-infrared light—has only been able to uncover giant Jupiter-sized exoplanets on wide orbits. All such planets exist well outside the habitable zone of a star where liquid water could exist.
This possible “warm Neptune” exoplanet found around Alpha Centauri A was detected much closer in by searching in mid-infrared light.
Mid-infrared light is thought to be where Earth-like planets are at their brightest because it’s exactly there that Earth and its atmosphere are at their brightest. Which makes using a telescope on Earth to look for mid-infrared light intrinsically difficult and subject to a lot of interference. Consequently, the faint signals of exoplanets get lost in a huge amount of background noise.
So the researchers used a new deformable secondary telescope mirror on the Very Large Telescope at the European Southern Observatory in Chile to correct for distortions in the light coming through the Earth’s atmosphere.
They also blocked the light from Alpha Centauri A and the other stars in the system using a coronagraph.
Despite the sophisticated measurement techniques the study still involved 100 hours of observations of Alpha Centauri A and Alpha Centauri B. “Keeping the telescope pointed at the same star for such a long time is highly unusual,” said Anna Boehle, a postdoc at ETH Zurich and second author of the study. “We assessed more than five million images,” she says.
It could forever change the hunt for Earth-like exoplanets. “Our findings indicate that in principle, this process enables us to discover smaller terrestrial planets capable of hosting life and it represents a clear improvement over previous observation methods,” said Boehle.
The search for planets capable of sustaining life may have taken a significant step forward.
Wishing you clear skies and wide eyes.