This is Bode’s galaxy (M81), an easily accessible island universe in Ursa Major that’s visible all year round from mid to high northern latitudes. It contains approximately 250 billion stars.
It lies over 10 million light years away and has a relatively close galactic companion – the M82 Cigar galaxy. Both of these galaxies can be framed in a low power telescopic eyepiece, and you can even see them very faintly in binoculars if your skies are suitably dark.
I thought I’d use this galaxy to highlight how astronomers use the full electromagnetic spectrum of light to study galaxies and their evolution. Pictured below, therefore, are images of M81 viewed in different wavelengths of light – from X-rays to radio waves (spanning short to long wavelengths). I’ve provided a very brief description of some of the galactic features revealed by each band of light.
X-rays: a central bright patch is revealed, suggestive of a supermassive black hole within the galactic nucleus. The other bright patches correspond to X-ray binary systems.
Ultraviolet: highlights young hot stars and therefore areas of active star formation within the spiral arms of the galaxy.
Optical and Infrared: Shows the bulk of the stellar population and areas of obscuring dust and nebulosity that will seed ongoing star formation.
Radio: Reveals supernova remnants and large H2 regions of ionised gas in the vicinity of very active stellar populations.
As humans our eyes have evolved to see a very narrow band of the full EM spectrum. This evolution is tied to the fact our particular star (the Sun) releases its peak energy in these wavelengths. I always like to imagine how other species, perhaps evolving next to giant sources of x-rays, might have sensory apparatus totally blind to visible light.
A lovely crescent Moon hung in the West for most of the evening
We enjoyed another superb evening of stargazing and storytelling up at Abriachan Forest last Saturday – the last dark sky session until stargazing returns in October 2019.
There were beautiful crisp skies all evening long, allowing me to guide both groups outside for views of the Milky Way and numerous open star clusters like the Hyades, Pleiades, Beehive and the stunning double cluster in Perseus.
We also studied the Orion star forming nebula, the great spiral galaxy in Andromeda and some fainter galaxies in Ursa Major (M81 and M82), and even had a go at sighting the triplet of galaxies in Leo, which some of the keen eyed youngsters successfully glimpsed in the 8×40 binoculars.
Clelland was also back in action with the story of Arden and the birth of Merlin in the roundhouse.
Thanks to everyone who came along. Please check my Facebook site for details of future summer events.