Also known as the Cigar Galaxy for its elongated visual appearance, M82 is a starburst galaxy with a superwind.
In fact, through ensuing supernova explosions and powerful winds from massive stars, the burst of star formation
in M82 is driving a prodigious outflow. Evidence for the superwind from the galaxy's central regions is clear in
this telescopic snapshot. The composite image highlights emission from long outflow filaments of atomic hydrogen
gas in reddish hues. Some of the gas in the superwind, enriched in heavy elements forged in the massive stars,
will eventually escape into intergalactic space. Including narrow band image data in the deep exposure has
revealed a faint feature. Perched about 35,000 light-years above the galaxy at the upper right,
the cap appears to be galactic halo material. The material has been ionized by the superwind shock or intense
ultraviolet radiation from the young, massive stars in the galaxy's core. Triggered by a close encounter with
nearby large galaxy M81, the furious burst of star formation in M82 should last about 100 million years or so.
M82 is 12 million light-years distant, near the northern boundary of Ursa Major.
[Text adapted from APOD]