Summer doesn’t begin for another month, but with the Fort Lewis College semester over and the Animas River flow rate increasing, it is hard not to think of summer-type recreational activities. Maybe you can include a star party in your list of things to do.
This is also the time of year when the asterism of the Big Dipper is very high in the northern evening sky. Asterisms are “easily recognizable patterns of stars,” and they may or may not correspond to a constellation. In the case of the dipper, this asterism is actually only part of the much larger constellation Ursa Major. Ursa Major, or Great Bear, is one of the largest constellations in the sky. Because it is so easily recognizable, I use it as a starting point to find other neighboring constellations.
Although the dipper is sometimes seen as a plough, or hunters following prey, many stories involve a bear. Not only does this constellation represent a bear in European mythology, but several Native American traditions are among those around the world that also associate the constellation with a bear. It is pure speculation, but I think these stars could have represented a bear even before humans lived in the Americas.
Merak and Dubhe, the two stars at the end of the dipper, are called the pointer stars because a line drawn through them will point to Polaris, the north star. This is a great navigational aid to anyone living in the northern hemisphere.
Mizar, the second star in the handle of the dipper, was the first telescopic binary star discovered. Mizar’s faint companion Alcor, a star that has been used as an “eye test” star, is not that double. (Interestingly, Alcor was recently determined to be gravitationally bound to Mizar, so is a part of that system of stars.)
With a small telescope, you can see that Mizar itself is a pair of stars. The brighter of the pair was also the first spectroscopic binary to be discovered. A spectroscopic binary is one where you can only tell that it is a binary star by looking at the spectrum of the star and observing the spectral lines moving back and forth as the stars orbit each other.
Since Ursa Major is not close to the path of the Milky Way in the sky, numerous galaxies can be seen. A few prominent ones can even show some detail besides just being a faint fuzzy smudge in the eyepiece. The pair of galaxies M81 and M82 are gravitationally bound and can often be seen together through a low-power eyepiece. They are nice because they are relatively bright, and you can see differences in their shapes, even through a very small telescope. M101, near the end of the handle, is one of the largest galaxies visible. With a little practice and a dark night, you can see these galaxies through binoculars.
This monthBesides the numerous deep sky objects in Ursa Major, the planets Jupiter, Mars and Saturn are great to look at this month.
Jupiter will be at its highest just after dark, and the orientation is good for catching eclipses and transits of the Galilean moons. Mars will be at opposition on May 22. Saturn, slightly to the east, will be at opposition on June 3.
At opposition, a planet is the closest it will get to the Earth during that orbit, so look for it at its highest point at midnight.
Charles Hakes is a visiting assistant professor in the physics and engineering department at Fort Lewis College and is director of the Fort Lewis Observatory. Email him at firstname.lastname@example.org.