Friday, March 20Its officially spring in the Northern Hemisphere. To celebrate, Mars and Jupiter meet up in the morning sky in the first of two planetary conjunctions this month. Look for the glittering stars of Sagittarius the Archer in the southeast in the two hours or so before sunrise. There, magnitude 0.9 Mars is a mere 0.7 south of magnitude 2.1 Jupiter.

About 7 east of Jupiter, magnitude 0.7 Saturn waits its turn for a close-up with the Red Planet. Mars will soon tango with the ringed world, coming closest on March 31.

Saturday, March 21Today is the perfect day to seek out our solar systems speediest planet. The Moon passes 4 south of Mercury at 2 P.M. EDT, but youll want to catch the pair in the morning before sunrise. At that time, the two will stand 5 apart, with Mercury glowing at magnitude 0.2 in the east-southeast 30 minutes before the Sun crosses the horizon.

Saturday is also Galactic Tick Day. The holiday is celebrated every 633.7 days (1.7361 years) to mark one galactic tick, which represents 1/100 of an arcseconds worth of the orbit our Sun and solar system make around the Milky Way. (It takes 225 million years to complete a full orbit.) You can learn more about the origins of this quirky and humbling holiday on the Galactic Tick Day homepage.

In honor of our journey through the galaxy, step outside from a dark site to see if you can spot the Milky Way running overhead. The plane of our galaxy runs through Cygnus the Swan, setting in the northwest as the sky grows darker after sunset. In the east, Orion the Hunter rises with the Milky Way at his right shoulder, which is marked by the bright red star Betelgeuse.

Sunday, March 22The fast-fading Moon is just 3 percent lit and rises shortly before the Sun, making tonight an excellent night to search out some of the skys fainter objects. Consider trying for M81 and M82, also known as Bodes Galaxy and the Cigar Galaxy, respectively. Both in the constellation of Ursa Major, these two galaxies appear only 37' apart on the sky and are easy to catch in the same field of view through binoculars or a telescope at low magnification. M81 has an active supermassive black hole in its center, while M82 is undergoing a massive burst of star formation hence its classification as a starburst galaxy. Astronomers believe this flurry of activity was actually caused by gravitational interactions with M81. Through a scope, M82 appears long and thin like a cigar while M81 has a rounder shape.

Monday, March 23Mercury reaches greatest western elongation (28) at 10 P.M. EDT, several hours before it rises ahead of the Sun. At sunrise, the tiny magnitude 0.3 planet is 10 above the horizon in the east-southeast, and its 7"-wide disk is just over half lit.

Today also marks the 180th anniversary of the first photograph ever taken of the Full Moon. John Draper captured the daguerreotype on this date from his observatory in New York after several previous attempts.

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The Sky This Week from March 20 to 27 - Astronomy Magazine