20:21
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Washington: For some time now, astronomers have believed that ancient elliptical galaxies do not give birth to new stars anymore, but new images captured by NASA’s Hubble Space Telescope indicate otherwise. The new study helps bolster the emerging view that most elliptical galaxies have young stars, bringing new life to old galaxies.
Images of the core of NGC 4150 reveal streamers of dust and gas and clumps of young, blue stars that are believed to be less than a billion years old rotate with the galaxy. According to NASA report, evidence shows that a merger with a dwarf galaxy sparked the star birth. The Hubble images reveal turbulent activity deep inside the galaxy’s core.
“Elliptical galaxies were thought to have made all of their stars billions of years ago,” said astronomer Mark Crockett of the University of Oxford, leader of the Hubble observations. “They had consumed all their gas to make new stars. Now we are finding evidence of star birth in many elliptical galaxies, fueled mostly by cannibalizing smaller galaxies. These observations support the theory that galaxies built themselves up over billions of years by collisions with dwarf galaxies,” he added.
“NGC 4150 is a dramatic example in our galactic back yard of a common occurrence in the early universe,” said Crockett. Based on Hubble analysis of stars’ colors, the star formation started about a billion years ago and the galaxy’s star-making factory has slowed down since then.
Crocket and his team, however, observed that most massive stars were already gone and that the youngest stars are between 50 million and 300 to 400 million years old. They also believe that the star birth came from a merger with a small, gas-rich galaxy around one billion years ago, which had the capability to fuel the star formation.he team selected NGC 4150 for their Hubble study because a ground-based spectroscopic analysis gave tantalizing hints that the galaxy’s core was not a quiet place.
The ground-based survey, called the Spectrographic Areal Unit for Research on Optical Nebulae (SAURON), revealed the presence of young stars and dynamic activity that was out of sync with the galaxy. The astronomers hope to study other elliptical galaxies in the SAURON survey to look for the signposts of new star birth. The study will be published in The Astrophysical Journal.source(ANI)
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