Astronomers using a new technique may not only have found a super-earth on a neighboring star, but they may have imaged it directly. And it could be nice and cozy in the habitable zone around Alpha Centauri.
It is much easier to see giant planets than Earth-sized planets. Whichever detection method is used, larger planets are simply a larger needle in the cosmic haystack. Overall, however, astronomers are very interested in Earth-like planets. And finding them is much more difficult.
We thought we would have to wait for the ultralight telescopes currently being built before we can image exoplanets directly. Facilities such as the Giant Magellan Telescope and the European Extreme Large Telescope will bring enormous observational power to the task of exoplanet imaging. However, a team of researchers has developed a new technique that could accomplish this task. They say they envisioned a possible sub-Neptune / Super-Earth size planet orbiting one of our closest neighbors, Alpha Centauri A.
The team presented their observations in an article in Nature Communications entitled “Mapping Low Mass Planets in the Habitable Zone of? Centauri. “The lead author is Kevin Wagner, an astronomer and Sagan Fellow at the University of Arizona.
“These results demonstrate the feasibility of imaging exoplanets in rocky habitable zones with current and upcoming telescopes.”
From “” imaging of low mass planets in the habitable zone of? Centauri. ”
While astronomers have found low-mass exoplanets before, they never felt their light. You have watched the planets reveal themselves by pulling on their stars. And they have observed how the light from the stars that host these planets fades as the planet passes in front of the star. But they have never mapped one directly. Until now maybe.
This new detection method depends on the infrared. One of the challenges of imaging Earth-sized exoplanets in infrared is recognizing the light coming from an exoplanet when that light is washed out by all of the star’s background infrared radiation. Astronomers can search for exoplanets in wavelengths where the background infrared is diminished, but at the same wavelengths, temperate Earth-like planets are faint.
One method is to look in the near infrared (NIR) of the spectrum. In NIR the thermal glow of the planet is not washed out by the star. But the starlight is still dazzling and a million times brighter than the planet. So just looking into the NIR is not a complete solution.
Artist’s impression of a sunset as seen from the surface of an Earth-like exoplanet. Credit: ESO / L. Calçada
The solution could be the NEAR (New Earths in the AlphaCen region) instrument used in this research. NEAR is mounted on the Very Large Telescope (VLT) of ESO (European Southern Observatory) in Chile. It works with the VISIR instrument, also on the VLT. The group behind NEAR is Breakthrough Watch, part of Yuri Milner’s Breakthrough Initiatives.
The NEAR instrument not only observes the desired part of the infrared spectrum, but also uses a coronagraph. The Breakthrough Group believed that the NEAR instrument, used in an 8-meter ground telescope, would allow for better observation of the Alpha Centauri system and its planets. So they built the instrument in collaboration with ESO and installed it on the Very Large Telescope.
A number of advanced instruments have recently been added to ESO’s Very Large Telescope (VLT). On May 21, 2019, the newly modified VISIR (VLT imager and mid-infrared spectrometer) made its first observations since its modification in order to search for potentially habitable planets in the Alpha Centauri system, the star system closest to Earth facilitate. This stunning image of the VLT is painted in the colors of the sunset and is reflected in the water on the platform. While bad weather at Cerro Paranal is unfortunate for the astronomers who use it, we can see ESO’s flagship telescope in a new light. Photo credit: ESO / VLT
This new finding resulted from 100 hours of cumulative observations with NEAR and the VLT. “These results,” the authors write, “demonstrate the feasibility of imaging exoplanets in rocky habitable zones with current and upcoming telescopes.”
The 100 hour commissioning run was intended to demonstrate the capabilities of the instrument. The team says the NEAR instrument is an order of magnitude better than other methods of observing “… warm sub-Neptune-sized planets in much of the habitable zone of? Centauri A. “
They may also have found a planet. “We are also discussing a possible detection of exoplanets or exozodic disks? Centauri A “, they write. “However, an instrumental artifact of unknown origin cannot be ruled out.”
A figure from the study. Panel (a) on the left shows artifacts 1 and 2, which are referred to as “detector persistence”. 3 is an “optical ghost” from Alpha Centauri A. Panel (b) at right is an enlargement of the interior areas of the (a) image. The candidate exoplanet is labeled C1. Photo credit: Wagner et al., 2021.
This is not the first time astronomers have found exoplanets in the Alpha Centauri system. There are a few confirmed planets in the system and there are other candidates as well. But none of them have been directly mapped like this new potential planet, which bears the placeholder name C1 and represents the first potential detection around the M dwarf in the system, Proxima Centauri.
Follow-up observations must confirm or cancel the discovery. The researchers say there is a chance the signal is an instrumental artifact. “We are also discussing a possible detection of exoplanets or exozodic disks? Centauri A “, they write. “However, an instrumental artifact of unknown origin cannot be ruled out.”
It’s exciting to think that a Warm Neptune-class exoplanet could orbit a Sun-like star in our closest star system. One of the goals of Breakthrough Initiatives is to send a light sail spaceship to the Alpha Centauri system and take a closer look at it.
The foreground of this image shows ESO’s Very Large Telescope (VLT) at the Paranal Observatory in Chile. The rich star background of the image includes the bright star Alpha Centauri, the closest star system to Earth. In late 2016, ESO signed an agreement with the Breakthrough Initiatives to adapt the VLT instrumentation to the search for planets in the Alpha Centauri system. Such planets could be the target for an eventual launch of miniature space probes by the Breakthrough Starshot Initiative. Photo credit: ESO
But this prospect is currently unattainable. In a way, this discovery is not so much about the planet as it is about the technology that was developed to recognize it.
The vast majority of the exoplanets discovered are gigantic planets with a mass similar to Jupiter, Saturn, and Neptune. They are the easiest to find. But as people from Earth, we are mostly interested in planets like ours. Earth-like planets in the habitable zone of a star excite us about the prospects of life on another planet. But they can also tell us a lot about our own solar system and how solar systems in general form and develop.
If C1 turns out to be a planet, the Breakthrough Group has managed to create a pivotal endeavor. You will be the first to recognize an Earth-like planet through direct imaging. Not only that, but also with an 8-meter ground telescope and an instrument specially designed to detect these types of planets in the Alpha Centauri system.
The authors are confident that NEAR can perform well even when compared to much larger telescopes. The paper’s conclusion contains a description of the overall sensitivity of the instrument. Then they write: “In principle, this would be sufficient to discover an earth-analog planet in the vicinity? Centauri A (~ 20 µJy) in just a few hours, which is what is expected for the ELTs. “
The E-ELT will have a 39 meter primary mirror. One of its capabilities and design goals is to directly image exoplanets, especially smaller, Earth-sized ones.
The ELT should see the first light in 2024. This illustration shows the scale of the telescope and its segmented primary mirror with a diameter of 39.3 meters. Photo credit: ESO
Of course, the E-ELT will be a hugely powerful telescope that will undoubtedly drive scientific discovery for a long time, not just in exoplanet imaging but in a variety of other ways. And other gigantic ground-based telescopes will change the exoplanet imaging game too. What took hours for NEAR can only take minutes for the E-ELT, the 30-meter telescope or the giant Magellan telescope.
NEAR cannot and was never designed to compete with these telescopes.
However, if these results are confirmed, NEAR will succeed where no one else has done it, at a fraction of the price of a new telescope. In any case, what NEAR has achieved probably represents the future of exoplanet research. Instead of broad-based studies like Kepler and TESS, scientists will soon be able to concentrate on individual planets.
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