Our Milky Way galaxy is a treasure trove of cosmic wonders including star clusters, various types of nebulae, stars of all sizes and ages, and more. Despite all that it offers us, our galaxy hinders our view of objects outside its realm. The vast amounts of dust, gas, and even then stars themselves get in the way of our views of extra-galactic space. Thankfully, the Milky Way’s shape helps us out. Spiral galaxies like ours resemble relatively thin disks. During the summer and winter, we can see this disk as a mottled, faint band traversing the sky. If we try to observe through the plane of our galaxy in visible light, our view doesn’t go very far; however, if we observe in a direction perpendicular to the disk, we can peer out into the universe more easily. This view comes around during spring and autumn when the Milky Way band appears near the horizon, making these prime times to view other galaxies near and far.
For those in the Northern Hemisphere, the constellation Ursa Major (home to the Big Dipper asterism) has several delightful galaxies that can be spotted telescopically even in somewhat light-polluted skies. Two of the easiest to see are known as Bode’s Galaxy and the Cigar Galaxy. These two galaxies showed up as the 81st and 82nd entries on 19th-century astronomer Charles Messier’s list of “non-comets,” so they are commonly referenced as “M81” and “M82.”
M81 is a beautiful example of a grand design spiral galaxy due to its well-defined spiral arms. Its circular structure appears somewhat elongated thanks to its slight inclination away from our line of sight. Around the size of our own Milky Way galaxy, M81 lies a mere 12 million light-years away, making it one of our closer galactic neighbors. It also harbors a supermassive black hole at its center that weighs in at around 70 million solar masses, a mass about 15 times greater than that of our galaxy’s behemoth, Sagittarius A*.
M82 at first looks like an irregular galaxy, a galaxy that doesn’t fall into the category of a spiral or an elliptical; however, roughly two decades ago, infrared observations detected the presence of spiral arm structure. The galaxy has a high surface brightness and boasts an extremely high rate of star formation, making this a “starburst” galaxy. Becoming a starburst galaxy is often the result of interactions between galaxies that compress clouds of gas and dust within, triggering star formation. M82 has interacted gravitationally at least once with neighboring M81, which is currently only about 300,000 light-years away. The high rate of star formation also leads to an elevated rate of supernovae, the explosive ends to short-lived massive stars. During their lives, stars produce stellar winds composed of electrons, protons, and even atoms with the more massive stars producing the strongest winds. With so many stars crowded within M82, a galactic “superwind” is produced that is also amplified by the numerous supernovae. Images highlighting the distinctive red glow of hydrogen (a key component of the wind) show M82 sporting tremendous red plumes of gas that extend out about 10,000 light-years.
To find M81 and M82 on your own, it helps to use some brighter stars as guide posts to “star hop.” First, locate the bright stars of the Big Dipper by looking toward the northern sky. In late spring/early summer, the Big Dipper appears upside down almost directly overhead by the time dusk fades. Find the bright bowl stars Phecda and Dubhe and connect them with a line. As you extend the line onward and are about to reach the moderately bright star 24 Ursae Majoris, you’ll come across two fuzzy patches separated by about a full moon’s width. Even in small telescopes, you’ll be able to notice their difference in shape to allow you to figure out which is which. Though they may not look like much in the eyepiece, keep in mind the light you’re seeing finally arrived at your telescope after starting a journey 12 million years ago!