A combination of three independent studies has confirmed the existence of a second planet around our Sun’s nearest stellar neighbor, Proxima Centauri.
Situated more than 4 light-years away, this red dwarf was first proposed to harbor an Earth-like exoplanet back in 2016. Proxima Centauri b, as it is known, was very recently confirmed by ESA’s ESPRESSO instrument, putting to bed previous reports that its original detection was an error. But the closest exoplanet to Earth is not alone.
Earlier this year, a larger planet in a colder and more distant orbit, dubbed Proxima Centauri c, was hinted at by astronomers, led by Dr Mario Damasso of Italy's National Institute for Astrophysics (INAF). Combing through 17.5 years of data, the team had been investigating the nature of the star’s wobble, and whether this was caused by internal processes or the pull of a nearby planet. This report triggered Fritz Benedict, an emeritus Senior Research Scientist with McDonald Observatory at the University of Texas at Austin, to re-visit data of the planetary system he gathered over two decades ago with the Hubble Space Telescope.
Using the telescope’s Fine Guidance Sensors (FGS), Benedict and his research partner, Barbara MacArthur, gained precise measurements of Proxima Centauri’s movement across the sky, caused by the tugging of possible “hidden” planets, back in the 1990s. At the time, they only checked the data for planets with an orbital period of 1,000 days or less. However, when Benedict recently reanalyzed the data, he found a planet with an orbital period of 1,907 days – Proxima c.
New images of Proxima c along its orbital path, taken with the SPHERE instrument on the Very Large Telescope in Chile, and published by a team from INAF, have added to this growing body of research on the planet. Indeed, these images, coupled with Benedict’s Hubble measurements and Damasso’s star wobble studies, have proven enough to confirm the existence of Proxima c, and have refined its mass to 7 times that of Earth.
“Basically, this is a story of how old data can be very useful when you get new information,” Benedict, who presented his findings during this year's virtual meeting of the American Astronomical Society, said in a statement. “It’s also a story of how hard it is to retire if you’re an astronomer, because this is fun stuff to do!”