Astronomers find a way to directly “see” habitable planets orbiting other stars

Despite the abundance of newly discovered planets beyond our solar system, we still haven’t seen any worlds that could potentially harbor life directly. Now that may have changed. A new technique could allow us to see a small subset of the worlds we are looking for and, on its first release, found a possible circle around one of the Sun’s closest neighbors.

Most of the planets around other stars (exoplanets) were found through their effect on their parent star, either blocking a little light or slightly altering its movements. Direct detection has been limited to rare cases, such as planets so young that they are still hot enough to be observed in the infrared. Even then, we are still limited to large worlds far enough away from their Sun that their light is not lost in glare. Not the places we go to find life.

However, University of Arizona graduate student Kevin Wagner says part of it is because we looked on the wrong end of the spectrum. Efforts to directly spot exoplanets have been carried out in the near infrared, with wavelengths less than 10 microns. Still, the planets we’re looking for are likely to be the brightest at slightly longer wavelengths.

As self-defeating as it sounds, Wagner noted in a statement; “There is a good reason for [these choices] because the Earth itself is shining on you at these wavelengths. It makes sense, after all, for Earth to be the brightest at the same wavelengths as the Earth-like planets we’re trying to find, but that doesn’t make it any easier. “The infrared emissions from the sky, the camera, and the telescope itself essentially choke off your signal,” Wagner added.

In Nature Communications, Wagner describes the use of a combination of instruments to allow the Very Large Telescope (VLT) to observe the Alpha Centauri system at wavelengths of 10-20 µm, blocking radiation from Earth and twin stars.

“We move a star on and a star off the coronograph every tenth of a second,” Wagner said. “It allows us to observe each star for half the time and, most importantly, it also allows us to subtract one frame from the next frame, which removes anything that is essentially just camera noise and noise. telescope.”

Wagner and his co-authors took over 5 million images in nearly 100 hours, stacking them on top of each other and removing unwanted contributions in a way he compares to noise-canceling headphones.

In the process, Wagner found a light source he called C1 that appears to be in the living area of ​​Alpha Centauri A. There is still a lot to be done to rule out an instrumental error or a cloud of dust, but C1 could also be the real thing.

“There is a point source that looks like what we would expect from a planet, which we cannot explain with any of the systematic error corrections,” Wagner said.

The team hopes to verify the existence of C1, both through follow-up observations on the VLT and through alternative planet-hunting methods, and apply the same method to other stars. However, the approach has its limits. In addition to taking a huge amount of time on one of the world’s most expensive telescopes, targets are limited to nearby stars. Moreover, Wagner’s technique could not yet find a planet the size of Earth. The smallest object would likely be around 3 to 5 times the radius of Earth, which almost certainly makes it a Neptune-style gaseous planet than a super-Earth.