Alpha Centauri is the closest galaxy to our sun. The inset image shows the two primary stars, A and B (a third star, Proxima, is some distance away). A new study shows that a planet could be within the habitable zone of Alpha Centauri A. Images via Zdenek Bardon and NASA / CXC / Univ. from Colorado / T. Ayres et al.
Astronomers have brought the picture something near the star Alpha Centauri A, in the galaxy next to our sun, only 4.4 light-years away. Is it an asteroid, or dust, or an error in the image, or … a planetIf it is a planet, it is the first known planet to be directly imaged in the habitable zone of a star, the region of a galaxy in which liquid water can exist and thus life as we know it can occur .
The team of astronomers call the object they imaged a “planet candidate.” This team is part of the Near Earths in the Alpha Centauri Region (NEAR) experiment, which specifically aims to image 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 magazine Nature Communications on February 10, 2021.
The lunar calendars of 2021 are here. A few left. Order yours before they are gone!
Because it is so relatively close (just 26 trillion miles or 42 trillion km), Alpha Centauri A is a logical target for the quest. Alpha Centauri A is one of the two major stars in this system, and the two stars – A and B – orbit each other about the size of a Saturn. The stars are comparable in size and temperature to our sun. The habitable zone, where liquid water is possible, is at a similar distance to the habitable zone from Earth.
The astronomers used the Very Large Telescope in Chile to search for planets in the mid-infrared range of the electromagnetic spectrum. Temperate planets similar to Earth shine brightest in this wavelength. But imaging was still challenging, as at 4.4 light-years away, every planet in Alpha Centauri A’s habitable zone would be just 1 arc second from its home star. That’s why the team put together 100 hours of observation time to get the most sensitive image ever of the habitable zone of the Alpha Centauri galaxy.
With this remarkable improvement in imaging capabilities, the team believes it can detect Neptune-sized planets within the star’s habitable zone. The astronomers’ goal was to see if planets lie around the habitable zones of stars could directly into the picture, and now they may have already found their first evidence of it.
In image b on the right – a zoomed in image of a on the left – the white dotted circle represents the inner edge of the habitable zone. The bright area labeled C1 is the candidate for the planet. Image via Nature Communications / NEAR.
The speck of light they observed is between the size of Neptune and Saturn and is about 1 astronomical unit, or the distance between the Earth and the sun, away from its own star. The astronomers know that the planet candidate could turn out to be something as boring as a defect or artifact in the data, but they’re excited about the possibility that they might have found one in their test to see if it could be done at all. They also hope to soon be able to photograph smaller planets closer to the size of the Earth.
University of Arizona team member Kevin Wagner posted the video below, which summarizes the NEAR experiment’s ambitions and the methods it used to find the candidate planet.
Their findings will have to be confirmed before a final declaration of a new planet can be made.
At least 50 planets orbiting other stars have been directly imaged, but none in this “Goldilocks” habitable zone near (but not too close) to its home star. The same telescope used in this study also captured the very first image of an extrasolar planet in 2004, when a dot was seen around a brown dwarf. Last year, the telescope saw the very first multi-planet system around a star.
Until now, direct imaging has worked best for planets very far from their parent star. From our point of view, it was also easier to see planets that are not passing in front of or behind the star. The new mid-infrared imaging method could change that and open new ways to find planets that can support water and life.
In short, astronomers may have directly captured an image of the very first planet within a star’s habitable zone. The star is Alpha Centauri A, just 4.4 light-years away, in the galaxy closest to our sun.
Source: Imaging low-mass planets in the habitable zone of Alpha Centauri
