This is Dudley Observatory’s Skywatch Line for Friday, June 24, through Sunday, June 26, written by Sam Salem.
The Sun rises at 5:18am on Friday and sets at 8:38pm. The Waning Gibbous Moon is 78% illuminated on Friday. In the next days the Moon rises after nightfall and sets westward direction after sunrise. On Sunday, the moon rises at 12:03am and sets at 11:48am. This weekend, look at the Moon, at the same time every day, and watch it climbing higher and higher up into the morning sky. The last quarter occurs on Monday at 2:19pm.
Mercury rises at 4:22 am on Friday. Mercury is having a very low partition in the dawn. Look for it above the east-northeast horizon 30 or 20 minutes before sunrise.
Jupiter appears high in the west as the darkness falls and remains in the sky until midnight. Jupiter shines at magnitude -1.9 in Leo the Lion.
Mars and Saturn rise before sunset. Mars, now of -1.6 magnitude in Libra, is still an attractive object to observe even with a small telescope. Saturn, of +0.1 magnitude, is about 20 degrees left of Mars at dusk with Antares to its lower right. Mars sets around 2:45am and Saturn sets around 4:09am on Saturday morning.
Sunday night is a good time to look for Pluto. The distant dwarf planet passes south of the third magnitude star Pi (p) Sagittarii in northeastern Sagittarius. You will need an 8-inch telescope or larger to spot the +14.1 magnitude dim world.
It’s summer time. Late sunsets combined with the long summer twilights reduce the time for dark sky observation. Darkness begins when the Sun dips 18 degrees below the horizon. The Sun’s position in the sky is defined by its declination and right ascension, which are similar to the latitude and longitude. After sunset, the Sun continues to move along its line of declination. The circles of declination intersect the horizon at a shallow angle around the solstice. Leading to longer twilight, as Earth must spin a while longer before the sun reaches the -18 degrees. The lines of declination curve upward as the Sun moves back toward dawn after a few hours of darkness.
June 26, 1730 is the birth date of Charles Messier. The French astronomer is best known for his famous astronomical catalog known as the “110 Messier Objects”. Messier’s job as a comet hunter led him to continually come across fixed fuzzy objects in the night sky which could be mistaken for comets. He compiled the list in collaboration with his assistant to help comet hunters distinguish between the comets they were looking for and the non-comet, permanent fuzzy objects, in the night sky. The catalogue consists of star clusters, nebulae, and galaxies. Messier did his observing with a 4-inch refracting telescope from a hotel in downtown Paris. Messier designations of celestial objects, from M1 to M110, are still used by astronomers today. The relative brightness of the Messier objects makes them popular objects for amateur astronomers.