Using a newly developed system for mid-infrared images of exoplanets, astronomers at the Breakthrough Watch Initiative say they can now use ground-based telescopes to directly capture images of exoplanets about three times the size of Earth in the habitable zones of nearby stars. Their first observations, conducted with ESO’s Very Large Telescope at the Paranal Observatory in Chile as part of the NEAR (New-Earths in the AlphaCen Region) program, resulted in the detection of a warm sub-Neptune-sized planet in the habitable zone of Alpha Centauri A, part of the galaxy closest to Earth.
Middle infrared images from Alpha Centauri AB: (a) high pass filtered image with no point spread function (PSF) subtraction or removal of artifacts; the Alpha Centauri B on-coronagraph images have been subtracted from the Alpha Centauri A-on-coronagraph images, resulting in a central residue and two off-axis PSFs from the SE and NW of Alpha Centauri A and B, respectively; systematic artifacts labeled 1-3 correspond to detector persistence from Alpha Centauri A, Alpha Centauri B, and an optical ghost from Alpha Centauri A. (b) zooming in on the innermost regions after artifact removal and PSF subtraction; areas affected by detector persistence are masked for clarity; the approximate inner edge of the habitable zone of Alpha Centauri A is indicated by the dotted circle; a detection of a candidate planet is designated “C1”. Image credit: Wagner et al., doi: 10.1038 / s41467-021-21176-6.
Alpha Centauri, also known as Rigil Kentaurus, Rigil Kent, and Gliese 559, is the closest galaxy to Earth.
This triple system consists of the bright binary star formed by Alpha Centauri A and B, plus the faint red dwarf star Alpha Centauri C.
The two brighter components are about 4.35 light-years away. Alpha Centauri C, more commonly known as Proxima Centauri, is slightly closer, at 4.23 light years.
Compared to our sun, Alpha Centauri A is of the same stellar type G2, but slightly larger. Alpha Centauri B, a K1-type star, is slightly smaller and less bright.
Alpha Centauri A and B revolve around a common center of gravity once every 80 years, with a minimum distance of about 11 times the distance between the Earth and the Sun.
“We achieved the ability to directly image planets about three times the size of Earth in the habitable zone of Alpha Centauri A,” said Dr. Olivier Absil, director of the PSILab (STAR Research Institute / Faculty of Science) at the Université de Liège.
In 2016, Breakthrough Watch and ESO launched a partnership to build a thermal infrared section, designed to block out most of the star’s light and optimized to capture the infrared light emitted from the warm surface of an in orbit planet orbiting the earth.
The coronagraph not only helps to dramatically reduce the light from the target star and thereby reveal the signatures of potential terrestrial exoplanets, but also adapts existing instruments to optimize its sensitivity to infrared wavelengths, allowing it to detect potential heat signatures similar to those from the earth.
Building on these advancements, as of 2019, astronomers have conducted more than 100 hours of observations to hunt exoplanets in the habitable zones of Alpha Centauri A and B.
This artist’s conception shows a hypothetical rocky exoplanet in the Alpha Centauri system. Image credit: Michael S. Helfenbein.
“We were amazed to find a signal in our data,” said Dr. Kevin Wagner, an astronomer at the University of Arizona.
“While the detection meets all the criteria for what a planet would look like, alternative explanations should be ruled out.”
“Verification can take time and requires the involvement and ingenuity of the wider scientific community.”
“Just a few years ago, we started looking for possible Earth-like planets orbiting Alpha Centauri A and B,” says Dr. Pete Worden, Executive Director of the Breakthrough Initiatives.
“We built the machine that could do the job, and now a candidate planet has revealed itself. The power of coordinated global scientific collaboration is astonishing. “
“When we work together on a global scale, we discover new worlds and keep moving forward,” said Yuri Milner, founder of the Breakthrough Initiatives.
“Identifying a candidate habitable zone planet in our heavenly backyard will continue to stimulate our curiosity.”
The team’s paper was published in the journal Nature Communications
K. Wagner et al2021. Imaging low-mass planets in the habitable zone of α Centauri. Nat Common 12,922; doi: 10.1038 / s41467-021-21176-6