The constellation of Ursa Major (The Great Bear) is home to Messier 101, the Pinwheel Galaxy. Messier 101 is one of the biggest and brightest spiral galaxies in the night sky. Like the Milky Way, Messier 101 is not alone, with smaller dwarf galaxies in its neighbourhood. NGC 5477, one of these dwarf galaxies in the Messier 101 group, is the subject of this image from the NASA/ESA Hubble Space Telescope. Without obvious structure, but with visible signs of ongoing star birth, NGC 5477 looks much like an typical dwarf irregular galaxy. The bright nebulae that extend across much of the galaxy are clouds of glowing hydrogen gas in which new stars are forming. These glow pinkish red in real life, although the selection of green and infrared filters through which this image was taken makes them appear almost white. Read more
Nearby dwarf galaxy and possible protogalaxy discovered Optical and radio telescopes lead to finds, reconstruction of intergalactic traffic jam
Peering deep into the dim edges of a distorted pinwheel galaxy in the constellation Ursa Major (the Great Bear), astronomers at Case Western Reserve University and their colleagues have discovered a faint dwarf galaxy and another possible young dwarf caught before it had a chance to form any stars. Within the faint trails of intergalactic traffic, the researchers also found more evidence pointing to two already known dwarf galaxies as probable forces that pulled the pinwheel-shaped disk galaxy known as M101 out of shape. M101 is the dominant member in a group of 15 galaxies in Ursa Major. Most galaxies reside in such small-group environments, which means the factors shaping M101 are likely the same shaping most galaxies throughout the universe, the researchers say. Read more