Red Dwarfs May Be Unfit Parent Stars

Red dwarf stars are the smallest true stars dancing around in our Galaxy, as well as the most abundant. Because of their small size–by star standards, that is–they can “live” for trillions of years on the hydrogen-burning main-sequence, and the Universe itself is “only” about 13.8 billion years old. For these reasons, many astronomers have suggested that most of the exoplanets in our Milky Way Galaxy circle “tiny” red dwarf stars–making these planetary systems prime targets in the hunt for life on other, distant worlds. However, a team of astronomers announced in June 2014 that life in the Universe may be rarer than previously believed, because their study found that harsh space weather might tear the atmosphere off any rocky world circling within a red dwarf’s life-friendly habitable zone. The team of astronomers announced their discovery during a press conference at the 2014 summer meeting of the American Astronomical Society (AAS) held in Boston, Massachusetts. mykindredlife

“A red dwarf planet faces an extreme space environment, in addition to other stresses like tidal locking,” commented Dr. Ofer Cohen to the press on June 2, 2014. Dr. Cohen is of the Harvard-Smithsonian Center for Astrophysics (CfA) in Cambridge, Massachusetts.

Our own planet is protected from violent solar eruptions and space weather by its magnetic field, which essentially works like the shields of the Starship Enterprise of Star Trek. Earth’s magnetic field serves to deflect approaching–and potentially destructive–blasts of energy. Our planet is also protected by its distance from the Sun, since it circles it at a comfortable 93 million miles!

Because a red dwarf’s habitable zone is much further in towards its seething star than the Earth’s distance from the Sun, any planet circling it would be subjected to more powerful and destructive space weather originating from its fiery stellar parent. The habitable zone of a star is that comfortable “Goldilocks” distance where the temperature is not too hot, not too cold, but just right for water to exist on its surface in a life-sustaining liquid state. Where liquid water exists, the potential for life as we know it, also exists.

Red Dwarfs

Relatively small red dwarf stars compose the vast majority of stellar inhabitants of our large, majestic, barred-spiral Galaxy, the Milky Way–which sparkles with the fires of at least 100 billion stars. There are approximately 100 red dwarf systems dwelling within 25 light-years of Earth. These tiny stars are very faint, and because they emit such a comparatively puny amount of radiation, they can lurk in interstellar space quite secretively, well-hidden in our Galaxy, where they cannot be easily detected by the prying eyes of curious astronomers. diagnozujmy

Red dwarfs are, therefore, the coolest, tiniest, and most common type of star. Estimates of their abundance range from 70% of all the stellar denizens of a spiral galaxy to more than 90% of all stars dwelling in elliptical galaxies. Usually, the median figure quoted is that red dwarfs account for 73% of all the stars dancing around in our Milky Way. Because of their relatively feeble energy output, these faint stars are never visible with the unaided human eye from Earth. The closest red dwarf to our Star, the Sun is Proxima Centauri, and it is a glittering member of a triple system of sister stars. Proxima Centauri (which is also the Sun’s nearest stellar neighbor), is much too dim to be viewed from Earth with the naked eye–as is the closest solitary red dwarf named Barnard’s star.

In recent years, astrobiologists and astronomers have been considering the possibility of life dwelling on alien worlds circling these tiny and very dim stars. A red dwarf sports the relatively small mass of only about one-tenth to one-half that of our Sun, and determining how their various characteristics affect the potential habitability of the planets that circle them may reveal to scientists the frequency of extraterrestrial life and intelligence.


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