Combinando le osservazioni del telescopio spaziale Hubble con i dati ottenuti col radiotelescopio VLA (Very Large Array) un team di astronomi guidato da Benjamin Williams รจ riuscito a ricostruire the history of star formation in NGC 2976, a small irregular galaxy 12 million light-years away in the constellation Ursa Major. The galaxy has some morphological characteristics and, as it is devoid of spiral arms, is evolving, presenting a very low rate of star formation, with other processes for concentrated almost exclusively in a region of no more than 5 thousand light years in diameter around the central black hole. Due to the sensitivity of the Hubble, astronomers were able to study individual stars within the galaxy, determining the physical characteristics and age. From here the discovery that the processes of star formation were virtually absent in the outer regions and very low in the inner ones. The explanation can be sought by the gravitational interaction that the galaxy has been with the members of the larger of storage which also belongs to M81. As a result of close encounters, the outer regions of the gas was stripped away, while inside the disk was pushed toward the center to feed the greed of the central black hole. The activity of star formation in the interior is still very low, and estimates of the astronomers, that will not last for another 500 million years. Such a process has been described by theoretical models and recent observations of NGC 2976 appear to confirm them.
Credit: NASA, ESA, and J. Dalcanton and B. Williams (University of Washington, Seattle)
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