Despite the abundance of newly discovered planets outside of our solar system, we still haven’t directly seen worlds that have the potential to harbor life. Now that may have changed. A new technique would allow us to see a small subset of the worlds we are looking for, and on its first outing, one of the sun’s closest neighbors may have been circling.
Most of the planets around other stars (exoplanets) have been found by their effect on their parent star, either by blocking a little light or by slightly changing the movements. Direct detection has been limited to rare instances, such as planets so young they are still hot enough to be seen in the infrared. Even then, we are still limited to large worlds far enough from their sun that their light is not lost in the brilliance. Not the places we go to find life.
However, University of Arizona graduate student Kevin Wagner says this is partly because we looked in the wrong part of the spectrum. Attempts to spot exoplanets directly have been made in the near infrared, with wavelengths less than 10 microns. Still, the planets we’re looking for are probably brightest at slightly longer wavelengths.
Self-destructive as this may seem, Wagner noted in a statement; “There is a good reason for that [these choices] because the Earth itself shines to you at those wavelengths. After all, it makes sense that Earth would be brightest at the same wavelengths as the Earth-like planets we’re trying to find, but it doesn’t make it easy. “Infrared emissions from the sky, the camera, and the telescope itself essentially drown out your signal” Wagner added.
In Nature Communications, Wagner describes the use of a combination of instruments to enable the Very Large Telescope (VLT) to observe the Alpha Centauri system at wavelengths of 10-20 µm, reducing the radiation from both Earth and the twin stars. blocked.
“We move one star up and one star from the coronagraph every tenth of a second,” Wagner said. “That allows us to observe each star half the time, and, most importantly, it also allows us to subtract one frame from the next, eliminating everything that’s essentially just noise from the next. camera and telescope will be removed. “
Wagner and co-authors captured more than 5 million images in nearly 100 hours, stacking them on top of each other and removing unwanted contributions in a way that he compares to noise canceling headphones.
In the process, Wagner found a light source he named C1 that appears to be in the habitable zone of Alpha Centauri A. There is still more to do to rule out instrumental errors or dust clouds, but C1 could also be the real deal.
“There is a point source similar to what we would expect a planet to look like that we cannot explain with any of the systematic error corrections,” Wagner said.
The team hopes to verify the existence of C1, both with follow-up observations on the VLT and through alternative methods of planetary hunting, and to apply the same method to other stars. Still, the approach has its limitations. In addition to taking a huge amount of time on one of the world’s most expensive telescopes, targets are limited to nearby stars. In addition, Wagner’s technique could not find a planet the size of Earth until now. The smallest object, it would be about 3-5 times the radius of Earth, almost certainly making it a Neptune-style gas planet than a super Earth.