M82 in LHaRGB (Ursa Major) , May 17,18,19 & 24 2023
Planewave CDK12.5″ telecope and A-P 1100GTO AE mount; ASI6200MM Camera, Antlia Pro BB & 3nm Ha Filters
L (37 x 200s exposures, Bin 2×2, Gain 100); R,G,B (20,24,25 x 240s exposures, Bin 2×2 Gain 100); Ha (23 x 400s exposures, Bin 2×2, Gain200); Total Integration Time = 9.2 hours
View/download full resolution from RASC Zenfolio or Astrobin
M82, The Cigar Galaxy, is quite the hotbed of star formation, as noted by the red H2 emissions combing out of the galactic plane. The statistics are quite impressive, with the equivalent of a sun-like star being created every day here – a rate that is ten times faster than all of the star forming regions in the Milky Way, despite being 20% smaller.
The whole rapid star formation process is believed to have been triggered by a relatively close encounter with M82 (Bodes Galaxy) when tidal forces distorted M81 some 200 to 500 million years ago when it was a quiet galaxy minding its own business. The gravity forces gave the pot a stir, as it were, creating what we call a “Starburst” galaxy. (Another, less dramatic starburst galaxy, can be seen in images of M106, where two extra spiral arms of H2 emitting regions seem to leave the galactic plane.) Stirring the pot involved creating a lot of turbulence within the molecular clouds of a galaxy and turbulence is just what is needed to nucleate (conceive?) new stars. Turbulence causes high pressure zones that can cause a cold gaseous mixture of hydrogen molecules and dust to condense to a protostar.
Newborn stars will emit lots of UV radiation, energizing the molecular clouds around them and making them shine the red Ha evident in the Cigar Galaxy. After imaging lots of galaxies, one can tell how active they are in star formation by how much red hydrogen alpha (Ha) light they emit. Usually, the telltale signal of red Ha light shows stars being formed around the turbulent sides of spiral arms. Here tidal forces have pulled apart the spiral arms out of the disk substantially, while creating the turbulence needed to create the stars that light them up.
Initially, M82 was thought to be an “irregular” shaped galaxy, but infrared data has shown that it is indeed a spiral. With some imagination, spirals can be made out here, but the abundance of new stars makes the galaxy so bright that it largely obscures its structure. As a result of all those new stars, M82 is very bright, about five times brighter than the Milky Way and its core is 100 times more so.
An abundance of new stars (especially fast burning, large blue ones) also results in an abundance of supernova, the last one recorded in 2014, after several were noted in the previous decades. These supernovae dramatically increase the solar winds that help push molecular clouds away from their regular “dust lane” positions. Other than that, the clouds march through their cycles of collapse to create stars, followed by being blown apart by those same stars.
The molecular clouds that create those stars is also being consumed at a very high rate in M82. In a few tens of millions of years, star formation will slow as the material becomes used up and more disperse.
M82 is also notable as it contains the brightest pulsar yet discovered – M82 X-2. M82 lies 12 million ly away from us, yet only 300,000 light years from M81 (with big error bars).