Free Astronomy Magazine November-December 2018

32 NOVEMBER-DECEMBER 2018 SPACE CHRONICLES tions of the stellar atmosphere. When the tangling gets too intense, the fields break and reconnect, un- leashing tremendous amounts of energy. The team has found that the flares from the youngest red dwarfs they surveyed — just about 40 million years old — are 100 to 1,000 times more energetic than when the stars are older. This younger age is when terrestrial planets are form- ing around their stars. App r o x i ma t e l y three-quarters of the stars in our galaxy are red dwarfs. Most of the galaxy’s “habit- able-zone” planets — planets orbiting their stars at a distance where temperatures are moderate enough for liquid water to exist on their surface — likely orbit red dwarfs. In fact, the nearest star to our Sun, a red dwarf named Proxima Centauri, has an Earth-size planet in its habitable zone. However, young red dwarfs are active stars, producing ultra- violet flares that blast out so much energy that they could influence at- mospheric chemistry and possibly strip off the atmospheres of these fledgling planets. “The goal of the HAZMAT program is to help understand the habitabil- ity of planets around low-mass stars,” explained Arizona State University’s Evgenya Shkolnik, the program’s principal in- vestigator. “These low- mass stars are critically important in under- standing planetary at- mospheres.” The results of the first part of this Hubble pro- gram are being pub- lished in The Astrophys- ical Journal . This study ex- amines the flare frequency of 12 young red dwarfs. “Getting these data on the young stars has been especially important, because the difference in their flare activity is quite large as compared to older stars,” said Arizona State University’s Parke Loyd, the first au- thor on this paper. The observing program detected one of the most intense stellar Superflares from young red dwarf stars imperil planets by NASA/ESA T he word “HAZMAT” describes substances that pose a risk to the environment, or even to life itself. Imagine the term being ap- plied to entire planets, where violent flares from the host star may make worlds uninhabitable by affecting their atmospheres. NASA’s Hubble Space Telescope is observing such stars through a large program called HAZMAT — HAbit- able Zones and M dwarf Activity across Time. “M dwarf” is the astro- nomical term for a red dwarf star — the smallest, most abundant, and longest-lived type of star in our galaxy. The HAZMAT program is an ultraviolet survey of red dwarfs at three different ages: young, interme- diate, and old. Stellar flares from red dwarfs are particularly bright in ul- traviolet wavelengths, compared with Sun-like stars. Hubble’s ultravi- olet sensitivity makes the tele- scope very valuable for observing these flares. The flares are be- lieved to be pow- ered by intense mag- netic fields that get tangled by the roiling mo-