This is Dudley Observatory’s Skywatch Line for Friday, July 14, through Sunday, July 16, written by Sam Salem.
On Friday, Sun rises at 5:30am and sets at 8:33pm; Moon sets at 11:44pm. Last quarter Moon occurs on Sunday at 3:26pm but doesn’t rise until after 1:00am on Monday.
Mercury hangs very low in the west in bright twilight at magnitude –0.3. The fast-moving little planet will climb higher in the coming weeks. Jupiter at magnitude –2.0 is well past the meridian at sunset. Saturn doesn’t culminate until around 11:15pm. At magnitude 0.1, Saturn is easy to identify low in the south, almost 14 degrees east of first-magnitude Antares. Venus, at magnitude –4.1, rises in the east at dawn. The “morning star” rises around 3am and climbs to an altitude of almost 25 degrees by sunrise. Venus is 3 degrees upper left of Aldebaran on Friday morning.
Try to locate the faint constellation Ophiuchus, the Serpent Bearer. Look southward at mid-to-late evening. Ophiuchus is sometimes called the 13th or forgotten constellation of the zodiac. The Sun passes in front of Ophiuchus from about November 29 to December 17. However, Ophiuchus is a constellation, not a sign of the zodiac. The 12 signs of the tropical zodiac represent equal 30- degree divisions of sky. Saturn and the bright star Antares in the constellation Scorpius, the Scorpion, can help you find Ophiuchus in the night sky. Saturn shines in front of Ophiuchus this year. Find Ophiuchus to the north of Antares.
Take advantage of the moonless evenings this weekend to do some deep-sky observing. Constellations Sagittarius and Ophiuchus harbor seven globular clusters each, which is nearly half the total in the entire Messier catalogue. M22, in Sagittarius, is an interesting cluster in any size telescope. The glowing M22, at magnitude 5.1, is the brightest Messier globular. It can be easily spotted in 10×50 binoculars. Find M22 about 2.5 degrees northeast of Lambda (λ) Sagittarii, the star marking the top of the Sagittarius Teapot.
The Great Rift of Milky Way passes through the constellation Cassiopeia and the Summer Triangle, between the stars Vega and Altair. The Great Rift is a series of overlapping, non-luminous, molecular dust clouds that are located between the Solar System and the Sagittarius Arm of the Milky Way Galaxy. To the naked eye, the Great Rift appears as a dark lane that divides the bright band of the Milky Way lengthwise, through about one-third of its extent, and is bordered by lanes of numerous stars. Starting at the constellation of Cygnus, where it is known as the Cygnus Rift, the Great Rift stretches to Aquila, to Ophiuchus, where it broadens out, to Sagittarius, where it obscures the Galactic Center, and finally, to Centaurus.
Saturday marks the 74th birthday of British astronomer, Jocelyn Bell Burnell who discovered the first four pulsars. Jocelyn was a Cambridge University graduate student searching for quasars in 1967, when she noticed an unusual stellar radio signal with a rapid series of pulses repeating every 1.337 sec. In the next few months, she found three more sources of radio pulses. The interstellar signals were not man-made. Therefore, the signals were nicknamed LGM (Little Green Men). These signals were emitted by a new class of celestial objects, Pulsars, which astronomers associated with superdense matter in the final stage of the evolution of massive stars.