Twinned Newborns only 20 Light Years from Earth. Ken Croswell, @scientificamerican



(Photo: Artist's impression of a M dwarf star surrounded by planets. Image credit: NASA/)

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Newborn only 20 Light Years from Earth. Ken Croswell, @scientificamerican

"...The discovery was an accident. Zuckerman was studying more distant young stars and noticed that EQ Pegasi might be moving with them. Then he saw that both stars were abnormally luminous—a sign of their youth.

A star forms when an interstellar cloud of gas and dust collapses under its own weight. As gravity squeezes the gas, it heats up, as compressed gas will do, until it shines—and a new star is born, but one that owes most of its light to gravity rather than to nuclear reactions. During this so-called pre–main-sequence phase, the star is larger and therefore brighter than it will be when it is more mature. The star slowly shrinks and fades until it reaches the main sequence, the stage when nuclear reactions at the stellar core convert protons into helium and supply the star with all of its energy.

Earth’s sun shone for 50 million years as a pre–main-sequence star. EQ Pegasi consists of two red dwarfs, stars that are much cooler, fainter and smaller than the sun. Such stars outnumber all other stellar types put together but are so dim that not a single one is visible to the naked eye. A red dwarf evolves slowly and lingers in the gravity-powered pre–main-sequence phase for more than 100 million years, outshining main-sequence stars of the same color. "The two stars in the EQ Pegasi system seem to be sitting above the luminosity that they would have if they were just ordinary main-sequence stars," Zuckerman says. As he and his colleagues report in the November 20 issue of The Astrophysical Journal, EQ Pegasi sports the nearest pre–main-sequence stars to Earth...."

Jul 16, 12:00 AM
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