Sky-watchers can rejoice at the change of seasons this week, seeing the moon join forces with Mars and Saturn, just as one of the sky’s most brilliant stars is eclipsed.
Moon joins Spica. Late at night on Monday, March 17, look for the waning gibbous moon to rise in the eastern sky with two bright celestial companions. The brighter starlike object to its left is, in fact, the planet Mars, and the fainter object next to it is the bright star, Spica.
By Tuesday night, the moon will have slid lower between the cosmic duo, creating a stunning conjunction. Luna will be especially close to the 263 light-year-distant Spica, which is the lead star in the constellation Virgo.
The pair will appear separated by less than 2 degrees, equal to only four lunar disks set side by side in the sky.
Asteroid eclipse. Very early on Thursday, March 20, lucky sky-watchers along a narrow strip of land across North America will see an extremely rare event as an asteroid passes in front of the bright star Regulus, visible to the naked eye.
At 2:07 a.m. EDT, the faint asteroid 163 Erigone will whiz in front of the brightest star in the springtime constellation, Leo, the Lion, making it disappear from view for up to 12 seconds.
The special stellar occultation will be visible to millions of people along a 45-mile-wide corridor that runs southeast to northwest from New York City to Oswego, New York, and continue northwest into Ontario, Canada.
Equal day and night. The spring equinox arrives at 4:44 p.m. ET on Thursday, March 20. The event officially marks the time of year that we kick off the spring season in the Northern Hemisphere and the start of autumn in the southern one. The word “equinox” comes from Latin meaning “equal night” and refers to its 12-hour-long day and night, which occurs twice a year.
Compared with the midday position of the sun during the winter season, Northern Hemisphere sky-watchers will notice that the sun has been slowly rising higher in the southern horizon and creating shorter shadows.
It’s only on the spring and autumnal equinoxes that the sun rises due east and sets due west.
Astronomically speaking, the spring equinox marks one of the four major turning points in the cycle of seasons. The Earth spins on its axis, which is tilted at 23.5 degrees with respect to its orbital plane. On these days, however, the Earth’s axis is tilted neither away nor toward the sun, but has both Northern and Southern Hemispheres experiencing equal amounts of sunshine.
Moon and Saturn. After midnight on Friday, March 21, the silvery moon and the ringed planet, Saturn, will be rising together in the east. The pair will appear to have a very close encounter, less than 2 degrees apart. Of course, their proximity will be an illusion. While the moon is only 236,120 miles (380,000 kilometers) from Earth, Saturn is a whopping 857.5 million miles (1.38 billion kilometers) away.
The Lord of the Rings is so far away from us that the sunlight beams reflecting off its cloud-tops takes some 77 minutes to travel through interplanetary space to reach our eyes.
Neptune encounter. Sky-watchers in the Southern Hemisphere can get a telescope-observing challenge by hunting down the ice-giant planet, Neptune, in the morning twilight on Saturday, March 22.
Nearby Mercury, a faint object (but easily visible through binoculars), will help locate Neptune, which is about 1 degree north of the inner planet. Observers should use a low telescope magnification when scanning the sky above Mercury to locate the faint, blue point of light that is the distant ice giant.
Join me, along with National Geographic Explorers, an astronaut, and questions from you, for our National Geographic Google+ Hangout to Explore the Wonders of the Universe. Post your questions to social media using #LetsExplore, and join us Thursday, March 20 at 2:30pm ET (6:30pm UTC).