To find life in other worlds, NASA will look at the light of a star

A NASA rocket will monitor a nearby star to find out how stellar light affects the atmosphere of extraterrestrial life, which is important information for life in space.

Using an updated tool that was first launched in 2019, the mission has a new goal: Procyon A, the brightest star in the Canis Minor galaxy.

SISTINE-2 (Exoplanet Host Stars near Suborpital Imaging Spectrograph for Transition Region Radiation) will have the first opportunity to launch from the White Sands missile range in New Mexico on November 8.

Answering the question of whether there is life anywhere else in the universe is fraught with technical challenges. We can no longer travel to the planets around other stars called exoplanets. Our telescopes are not powerful enough to see their surface either.

Instead, astronomers look at the atmosphere of an extraterrestrial and look for traces of chemicals associated with life. The so-called water, methane, oxygen, ozone and biomarkers create unique light patterns that telescopes can detect remotely. But to interpret them correctly, astronomers need to look at the planet’s star.

“The relationship between the planet’s atmosphere and the host star’s ultraviolet light determines which gases act as the best biomarkers,” said Kevin France, astronomer at Boulder University in Colorado and chief researcher on the mission.

Some ultraviolet (UV) wavelengths, for example, break down carbon dioxide and combine with one oxygen atom to form molecular oxygen (made up of two oxygen atoms) or ozone (made up of three). Stars that emit enough light will create fake biomarkers on their planets and send astronomers to the wrong places.

The SISTINE team aims to avoid this dilemma by developing a guide for the wavelengths emitted by each type of star. There are different types of stars, and we do not yet have a complete picture of their light output or how it changes over time. Using a starlight list, scientists can assess whether the detected biomarker is a possible sign of life or a false signal generated by annoying starlight.

In its next flight, SISTINE-2 will observe Procyon A at a distance of about 11.5 light-years. Procyon A is an F-type star that is slightly larger than our Sun, hotter and brighter. Although there are no extraterrestrials, studying Procyon A will help us understand the F-type stars around the universe and their orbits.

“Knowing the ultraviolet spectrum of these stars will help us find the most promising star-planet environments with future NASA observatories,” France said.

SISTINE-2 consists of a telescope and an instrument called a spectrograph, which separates light into its individual colors. SISTINE-2 targets ultraviolet light from 100 to 160 nanometers, a range that includes wavelengths that produce false positive biomarkers. The team hopes to gather a reference spectrum to help astronomers interpret biomarkers on exoplanets orbiting F-type stars by combining their data with the visible light observations of existing X-rays, ultraviolet and other F-type stars.

Also tests SISTINE-2 hardware. Prior to its 2019 flight, the team applied an enhanced lithium fluoride optical coating to the instrument glass to enhance their UV reflectivity. The results, after some three years, help to assess whether this special coating is suitable for large and long space missions.

Five minute mission

Like its 2019 aircraft, the instrument will be launched on a probe rocket, which is a small sub-orbital rocket that makes brief observations in space before returning to Earth. Climb to an altitude of approximately 280 km to access the ultraviolet light absorbed by our atmosphere and observe SISTINE-2 Procyon A for about five minutes. The instrument will then fall back to earth and the parachute will fall down for recovery and reconstruction.

The team expects a smooth landing ready for a third launch in July 2022 from the Arnhem Space Center in Nhulunbuy, Australia, for a quick turnaround. There, the updated SISTINE instrument will track the alpha Centauri stars A and B, G and K, respectively, which are similar and slightly cooler than our Sun, and the stars closest to us.

The system is also the location of Proxima Centauri, a cool red dwarf star orbiting the closest proximal proxima B. These observations will add additional entries to the rising table of stars – small but important steps in the search for life.