How Many Planets Orbit Our Nearest Neighboring Star?

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Some of the most promising places to look for extraterrestrials have remained, so far, mostly hidden from astronomers. Now a game-changing instrument called NIRPS (Near-Infrared Planet Searcher) is leading the search for the most tantalizing targets in the cosmos: potentially Earth-like worlds around nearby red dwarf stars.

Red dwarfs, or M dwarfs, are the most tempting places to seek alien Earths because they're the most abundant and enduring stars . They make up the majority of the stars in the Milky Way and shine with a slow thermonuclear simmer that should allow them to live exponentially longer than most—even, say, for 14 trillion years , or 1,000 times the current age of the universe.

But M dwarfs are also the smallest, dimmest stars, so they and their planets can be difficult to detect and inspect. Enter NIRPS, an instrument custom-built to tease out subtle signs of otherwise hidden worlds by making unmatched high-precision measurements of M dwarfs, which emit most of their light in infrared and near-infrared wavelengths.

"I think we are in the golden age of M dwarfs, where they offer a huge amount of possibility—they are the best place to detect small Earth-sized planets," says Natalie Hinkel, a planetary astrophysicist at Louisiana State University, who is not a member of the NIRPS team.

René Doyon, a professor at the University of Montreal and co-principal investigator of NIRPS, contextualized the breakthrough in a press release : "For the first time, we can reach sub-meter-per-second radial velocity precision in the infrared." This means that NIRPS can view a distant star zooming through space and discern a change in its velocity that's equivalent to the speed of a leisurely stroll through the park.

NIRPS and other RV-based projects are spectrographs, akin to prisms attached to existing telescopes. Much like a prism spreads white light into a rainbow of colors, a spectrograph splits incoming starlight into its constituent wavelengths, producing a rainbowlike spectrum. " Fingerprints " of different atoms and molecules in a star's atmosphere can be imprinted on its spectrum, and they serve as reference marks to planet-hunters looking for minuscule velocity shifts.