Alpha Centauri is the closest galaxy to our sun. The inserted image shows the two primary stars, A and B (a 3rd star, Proxima, lies some distance away). A new study shows that a planet may lie in the habitable zone of Alpha Centauri A.. Images via Zdenek Bardon and NASA / CXC / Univ. of Colorado / T. Ayres et al.
Astronomers made it something near the star Alpha Centauri A, in the galaxy next to our sun, just 4.4 light-years away. Is it an asteroid, or dust, or an image disorder, or … a planet? If it is a planet, it is the first known planet to be imaged directly in the habitable zone of a star, the region of a star system in which liquid water can exist and thus in life as we know it.
The team of astronomers calls the object they imaged a ‘planetary candidate’. This team is part of the Near Earth Experiment in the Alpha Centauri Region (NEAR), with the specific goal of imaging 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 Nature communication on February 10, 2021.
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Because Alpha Centauri A is so relatively close (only 26 trillion miles, or 42 trillion km), it is a logical target for the search. Alpha Centauri A is one of two large stars in this system, and the two stars – A and B – orbit each other in an approximate Saturn-sized orbit. The stars are similar in size and temperature to our Sun. The habitable zone, where liquid water is possible, will be at a similar distance as where the earth’s habitable zone lies.
The astronomers used the Very Large Telescope in Chile to search for planets in the middle-infrared region of the electromagnetic spectrum. Moderate planets similar to Earth shine the brightest in this wavelength. But the imagery was still challenging, because at 4.4 light-years away, any planet in the habitable zone Alpha Centauri A would be just 1 arc second from its home star. The team therefore compiled 100 hours of observation time to achieve the most sensitive image ever taken of the habitable zone of the Alpha Centauri galaxy.
With this remarkable improvement in imaging capabilities, the team believes they can locate Neptune-sized planets within the star’s habitable zone. The goal of the astronomers was to see if planets existed around the habitable zones of stars. could directly depicted, and now they may have already found their first proof of it.
In image b on the right – a zoomed-in image of a on the left – the white dotted circle represents the inside of the habitable zone. The bright area marked C1 is the planetary candidate. Image via Nature Communications / NABY.
The spot of light they detected is between the size of Neptune and Saturn and lies about 1 astronomical unit, or the distance between the earth and the sun, away from its own star. The astronomers know that the planetary candidate could turn out to be something as contagious as a defect or artifact in the data, but they are excited about the possibility that they found one in their test to see if it could even be done. They hope to soon be able to image smaller planets, closer to the size of the earth.
Team member Kevin Wagner of the University of Arizona posted the video below, which gives a summary of the ambitions of the NEAR experiment and the methods to find the candidate planet.
Their findings will have to be confirmed before definitive proclamation of a new planet can be made.
At least 50 planets around other stars are directly imaged, and no one in this habitable zone “Goldilocks” (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 multiple planetary system ever around a star.
So far, direct imaging has worked best for planets that are very far from their parent stars. It was also easier to see from our point of view planets that do not pass in front of or behind the star. The new middle-infrared imaging method can change that and open up new ways to find planets that can support water and life.
In short: Astronomers have directly mapped the first planet ever within the habitable zone of a star. The star is Alpha Centauri A, just 4.4 light-years away, in the galaxy closest to our sun.
Source: Image of low-mass planets within the Alpha Centauri habitable zone
