Alpha Centauri is the closest stellar system to our sun. The inserted image shows the two main stars, A and B (a third star, Proxima, is at a certain distance). A new study shows that a planet could be in the habitable zone of Alpha Centauri A. Images by Zdenek Bardon and NASA / CXC / Univ. from Colorado / T. Ayres et al.
Astronomers have imagined something near the star Alpha Centauri A, in the stellar system next to our sun, just 4.4 light-years away. It’s an asteroid, or dust, or an image error or … the planet? If it is a planet, it is the first known planet that was made directly in the habitable zone of a star, the region of a stellar system in which liquid water can exist and, therefore, in which life could occur as we know it.
The team of astronomers calls the object they imagined a “candidate for the planet.” This team is part of the Alpha Centauri (NEAR) Near Earth experiment, with the specific goal of imagining low-mass (Earth-like) planets in the habitable zones of stars. The group made the observations in May and June 2019 and reported them in the journal Communications about nature on February 10, 2021.
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Because it is so close (only 26 trillion miles, or 42 trillion km), Alpha Centauri A is a logical target for search. Alpha Centauri A is one of the two large stars in this system, and the two stars – A and B – orbit each other in an orbit about the size of Saturn. The stars are similar in size and temperature to our sun. The habitable zone, where liquid water is possible, will be at a distance similar to that of the habitable zone of the Earth.
Astronomers have used Chile’s very large telescope to search for planets in the mid-infrared range of the electromagnetic spectrum. Earth-like temperate planets shine brightest at this wavelength. But the imagery was still challenging, because 4.4 light-years away, any planet in the habitable zone of Alpha Centauri A would be just 1 arc second from its home star. Thus, the team compiled 100 hours of observation to obtain the most sensitive image ever made on the habitable zone of the Alpha Centauri stellar system.
With this remarkable improvement in imaging capabilities, the team believes it can detect planets the size of Neptune in the habitable zone of the star. The astronomers’ goal was to see if the planets around the habitable zones of the stars could to be imagined directly, and now you may have already found their first proof.
In image b on the right – an enlarged image aa on the left – the white dotted circle represents the inner edge of the living area. The luminous zone labeled C1 is the candidate of the planet. Image via Nature Communications / NEAR.
The spot of light they detected is between the size of Neptune and Saturn and is about 1 astronomical unit, or the distance between the Earth and the sun, far from its own star. Astronomers know that the planet’s candidate may turn out to be as eventless as a defect or data artifact, but they are excited that they may have found one in their test to see if it could even realize. They also hope to soon be able to imagine smaller planets closer to the size of Earth.
Team member Kevin Wagner of the University of Arizona posted the video below, which provides a summary of the ambitions of the NEAR experiment and the methods he used to find the candidate planet.
Their discoveries will have to be confirmed before a new planet can be definitively proclaimed.
At least 50 planets around other stars have been directly imagined, except that none of this habitable area “Goldilocks” is close (but not too close) to its home star. The same telescope used in this study also made the first image of an exoplanet in 2004, when a spot was seen around a brown dwarf. Last year, the telescope saw the first multi-planet system around a star.
So far, direct imaging has worked best for planets that are far from their parent stars. It was also easier to see planets that do not pass in front of or behind the star from our point of view. The new medium-infrared imaging method can change this and open up new avenues for finding planets that could support water and life.
Conclusion: Astronomers may have directly imagined the first planet in the habitable zone of a star. The star is Alpha Centauri A, just 4.4 light-years away, in the stellar system closest to our sun.
Source: Imagination of low-mass planets in the habitable zone of Alpha Centauri
