An Astronomical Tour in the Realm of Galaxies
A Hubble Space Telescope view of the irregular galaxy M82, an astronomical object that can be spotted in summer skies with the help of binoculars. NASA, ESA, The Hubble Heritage Team, (STScI / AURA)
The summer skies aren't always the obvious time to go galaxy hunting because the combination of faint objects, bright skies and longer days can make finding them a little tricky.
However, those of you in the Northern Hemisphere prepared to stay up late until the sky properly darkens will be treated to a few galactic treasures in the skies of July and August.
Obviously placed due south during local midnight is our own galaxy, the Milky Way, making a excellent place to start our tour of deep space. We live inside the Milky Way at a distance of around 30,000 light-years from the galactic core — this is why our galaxy appears in our sky as a band of light.
The Milky Way is believed to be a "barred spiral galaxy" around 100,000 light years across with up to 400 billion stars. Because of the obscuring dust and foreground stars, it's not easy to spot galaxies in the direction of the Milky Way so we have to look due east and west ("up" and "down" from the galactic disk) to see external galaxies.
Over in the far west are the constellations of Virgo, Coma Berenices and Canes Venatici that are home to some great galaxy clusters. There are three bright galaxies to look out for in the western sky and they can be found from the easily recognizable Plough (or "Big Dipper"), part of the much larger Ursa Major constellation.
Starting from Alkaid, the end star of the Big Dipper's handle, head no more than 5 degrees (a clenched fist at arm's length measures 10 degrees, so its half that distance) in the same direction that takes you parallel with the nearest two stars of the bowl and you will find a beautiful example of interacting galaxies called the Whirlpool Galaxy and NGC5195. From a dark site it can be just about detected in binoculars, but telescopes with 10 centimeter (4 inch) aperture or more are needed to be able to detect the spiral arms. Anything larger should show the two galaxies with ease with an increasing level of detail.
Now identify the stars at the bottom left of the bowl, Phecda and Dubhe at the upper right. Imagine a line between them and extend the line on further due north for about the same distance. There are two galaxies here; M81, which is a bright spiral galaxy easily detectable in binoculars and any telescope larger than 15 cm (6") will pick out its spiral arms. It's estimated to be 12 million light years away and is gravitationally bound with its neighbour M82. This irregular galaxy is fainter than M81 but can still be seen in binoculars in the same field of view as M82.
Turning to the north-east now and the great square of the constellation Pegasus is rising. Its north-east corner star is also the starting point for the constellation of Andromeda. Move further east by Delta Andromedae and Mirach and then up by another two fainter stars and just to the north west of Nu Andromedae is the famous Andromeda Galaxy. An easy target for the naked eye under dark skies it's the nearest major galaxy to our own. Even small telescopes reveal its two companion galaxies M32 and M110.
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To the south of Andromeda is a bright orange star that is prominent in an otherwise sparse sky called Hamal in Aries. Between the two is a faint constellation called Triangulum, which, unsurprisingly, represents a triangle pointing to the west. Off to the west of the triangle and almost half way between Mirach and Hamal is the Pinwheel Galaxy of M33. At 3 million light years away its the most distant object that can be seen with the naked eye under exceptionally dark conditions. Due to its size, it's better to use a good pair of binoculars.