This is Dudley Observatory’s Skywatch Line for Wednesday and Thursday, November 23 and 24, written by Alan French.
The Sun rises at 6:57 A.M. on Wednesday and sets at 4:26 P.M. On Thursday it rises at 6:58 and sets at 4:25. This Thursday has 13 ½ minutes less daylight than last Thursday. As the Sun continues to move south our days continue to grow shorter, but at a slower rate. We still have another 25 ½ minutes to lose before the days start getting longer again.
The Moon reaches new late Thursday afternoon so the night sky is moonless and dark.
There is concern among professional and amateur astronomers and those who simply enjoy the beauty of the night sky about pollution from the many satellites being orbited for global communications. Back on September 11 BlueWalker 3 was launched. Like many satellites, it was launched in a folded configuration. Recently unfolded, it is large, about 8 meters square, and large satellites reflect a lot of sunlight and appear bright. (The ISS shines brightly because it is the largest manmade object now in orbit.) Recent reports say BlueWalker 3 is now 1st magnitude, about the brightness of Deneb, the brightest star in Cygnus, the Swan, or Altair, the luminary of Aquila, the Eagle.
On Wednesday and Thursday nights, BlueWalker 3 will be visible from our area, and we can check its brightness. Both passes cross our skies high toward the northwest and move into the Earth’s shadow, fading from view, before reaching the horizon.
On Wednesday evening look for BlueWalker 3 low in the west southwest moving up from the horizon and headed northward at 6:26. Just after 6:28 it will be 35-degrees above the western horizon. Just before 6:29 it will pass close the bright Vega, which shines at magnitude 0, brighter than the claimed magnitude 1.0 of BlueWalker 3. Which do you see as brighter?
At 6:29:35 (HH:MM:SS) the satellite will reach its highest point in the sky, 55-degrees above the north northwestern horizon. Just under 20 seconds later it will move into the Earth’s shadow and fade from view.
Thursday night’s pass of BlueWalker 3 follows a similar, but slightly lower, path across our sky, and is earlier.
Look for BlueWalker 3 coming up in the west southwest at 6:08 P.M., its path angled upward toward the north. By 6:10 the satellite will be due west and 31-degrees above the horizon. By 6:10:30 it will be passing near bright Vega. Which appears brighter to your eyes?
After passing below Vega, BlueWalker 3 will pass through Draco, the Dragon, and then above, Ursa Minor, the Little Bear, familiar to most as the Little Dipper, with Polaris, the North Star, marking the end of the dipper’s handle. BlueWalker 3 will pass just above the North Star just before 6:12 and will enter the Earth’s shadow and begin fading from view at 6:12:28.
The company that launched and is testing BlueWalker 3 plans to launch 100 larger communications satellites, called BlueBirds. They are expected to be about twice the size of BlueWalker 3, and brighter as they cross our skies.