Skywatch Line for Friday, August 18, through Sunday, August 20, 2023
This is Dudley Observatory’s Skywatch Line for Friday, August 18, through Sunday, August 20, written by Sam Salem.
On Friday, Sun rises at 6:05am and sets at 7:53pm; Moon rises at 8:03am and sets at 9:08pm.
The waxing crescent Moon will pass by Mars on Friday and Saturday nights. It’ll be closest to Mars on Friday evening. At their closest, the Moon will be two degrees, the width of four full moons, apart. Mars has a roughly two-year cycle of visibility in our sky. For much of that cycle, it’s faint and inconspicuous. But, for a period of about six months, every couple of years, Mars brightens and appears quite red. It happens around the time Earth passes between Mars and the Sun. That happened in December 2022, when Mars reached opposition. Now, we’re about as far away from Mars as we can get, in our smaller, faster orbit. Right now, Mars is on the opposite side of the solar system from us and has faded from its recent opposition of magnitude -1.9 to its current magnitude +1.77. While Mars is still brighter than most stars, it’ll remain faint until it begins to slowly brighten again later next year.
The best time to see the constellation of Aquila the Eagle in the evening sky is from July to November as it soars along the Milky Way. Because our galaxy provides a starry backdrop, many clusters and nebulae lie within its borders. Aquila’s brightest star, Altair, is the southernmost corner star in the Summer Triangle. In mythology, Aquila carried Zeus’ thunderbolts for him. Altair, or Alpha Aquilae, at magnitude 0.76, is one of the three bright stars that mark the corners of the Summer Triangle. Deneb, in the constellation of Cygnus the swan, and Vega, in the constellation of Lyra the lyre, are the other two and they lie higher in the sky, closer to the zenith on summer evenings.
Two moderately bright stars lie on either side of Altair. To the southeast is Beta Aquilae, or Alshain. To the other side of Altair is Gamma Aquilae, or Tarazed. These stars are usually considered the tail feathers of the Eagle. Then, the star marking Aquila’s back is Delta Aquilae. Theta Aquilae marks the wing that points to the east-southeast. The wing that points to the north, and Vega, holds Zeta Aquilae. Lastly, the star that marks the head of the Eagle is Lambda Aquilae.
61 Cygni is a double star in the constellation Cygnus the Swan. It’s not a standout in brightness. This double star is interesting to stargazers because it has one of the highest proper motions of any visible star. That’s its sideways movement across the dome of the sky. If you took photos of 61 Cygni over the course of several years, you’d see it shift position in the sky with respect to the more distant stars around it. This unusual motion across our sky earned 61 Cygni the nickname Flying Star.