The month of March is named after the Roman god of war, Mars. It also used to be the first month of the year. For us in the northern hemisphere, March always marks the beginning of spring. This year, that will happen at 6:45 p.m. on Friday the 20th.
That important moment can be further defined by the sun on the ecliptic crossing over the celestial equator on an upward path. That is also called the vernal equinox. That word means “equal night,” which is when the days and nights are both equal to 12 hours. That day actually happens two days before the equinox, on the 18th, because the earth orbits the sun in ellipses and not perfect circles.
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The vernal and autumnal equinoxes are the only two days each year when the sun rises due east and sets due west for everyone on Earth except for the North and South Pole. Near the equator, within the region of the tropics that reaches up to 23.5 degrees north and south of the equator, the days are always about 12 hours long, not just during the equinoxes.
So those two configurations at the equinoxes can be seen as a unifying principle of experience for the nearly 7.3 billion people that now share this fragile planet.
The earth will have to warm up a little this month as it slowly tilts back toward the sun again. There will be several interesting highlights to see as more people venture outside again after a long, cold and snowy winter: Jupiter will still be close to its best; more mutual occultations and eclipses of Jupiter’s four large Galilean moons; Venus and Mars slowly drift apart again; nice conjunctions of crescent moons with Mars and Venus; Saturn rising around midnight; and a challenge to see the famous white dwarf star that’s the companion star for Sirius. If you are willing to travel a little, there is even a total solar eclipse coming up in the North Atlantic just 12 hours before spring starts.
Jupiter is still close to its best and brightest for the year. It rises around one hour before sunset and will reach its highest point in the sky, which is defined as transiting the meridian around 10:30 p.m. starting this month. Notice that the king of the planets is still in retrograde motion westward toward the Beehive Star cluster in Cancer, but it will not reach it before it returns to its normal eastward or prograde motion again next month. A nearly full moon will pass just to the right of Jupiter on the evening of Monday the 2nd.
There are many more mutual occultations and eclipses happening between the four large Galilean moons of Jupiter every night this month. Check out a detailed schedule if you would like to observe some of them through a telescope to attain a better understanding of how this miniature solar system really works.
Our two nearest planetary neighbors, Venus and Mars, are slowly drifting apart again after a close conjunction last month. Notice that Venus is just over 5 magnitudes, or 100 times brighter than orange Mars. Venus keeps rising higher and setting later. It will not set until after 9 p.m. by the end of this month. Mars is doing just the opposite, setting earlier and slowly sinking out of view by the end of the month after it matched our rate of revolution around the sun at one constellation per month for the last half-year. The net result was Mars always set at about the same time, a few hours after sunset.
If you have a good pair of binoculars or a telescope, you can spot a much fainter planet that has been hanging out near the pair for a month or so. Uranus is closest to Venus on March 4, less than one-tenth of a degree away. Notice that it will be fully 10 magnitudes, or 10,000 times fainter than Venus. On March 11, Uranus will pass less than one third of a degree below Mars. Since its discovery on March 13, 1781; by Sir William Hershel, Uranus hasn’t even completed three of its 84-year orbits around the sun.
The gap between Mars and Venus will be increasing at the rate of about half a degree per day. By March 21, right after spring starts, they will be about 12 degrees apart, which can be measured in the sky by just over one fist at arm’s length. That is also the distance the moon moves each day. It moves eastward its own width – which is half a degree – each hour against the fixed background of stars. On the evening of Saturday the 21st, the slender waxing crescent moon, only about a day and a half old after creating a total solar eclipse over the North Atlantic by having its shadow cone sweep over a small part of the earth, will be less than half a degree to the left of Mars. The next evening, the moon will appear 7 percent larger and about one degree to the left of Venus.
Saturn is getting a little closer and brighter each night, and will be rising a little earlier. The ringed planet will end its eastward motion on March 14, which also happens to be Albert Einstein’s birthday. Then it will reach opposition on May 22 and end its retrograde motion about two months after that.
The brightest star in our sky is named Sirius and can easily be seen in the constellation of Canis Major. It also has a companion star called Sirius B, which is a white dwarf. It makes an elliptical orbit around Sirius every 50 years. The last time it was as far away from Sirius as it is now was in 1979. It will not reach its maximum separation of 11.3 arc seconds until 2022, but now it is already separated by 10.7 arc seconds, which means it should be possible to see it in a good telescope.
MARCH HIGHLIGHTS
March 5: Full moon is at 1:05 p.m. This is also called the Sap, Crow, Worm or Lenten Moon
March 6: The Dawn spacecraft is scheduled to arrive at Ceres, our largest asteroid.
March 8: Daylight-saving time starts at 2 a.m.
March 12: The waning gibbous moon is just 3 degrees from Saturn and 9 degrees from Antares in Scorpius this morning.
March 13: In 1781, William Herschel discovered the planet Uranus. The last-quarter moon is at 1:48 p.m.
March 14: Albert Einstein was born in 1879. His general theory of relativity, published in 1915, completed redefined gravity as simply the curvature of the fourth dimensional space-time continuum.
March 20: New moon is at 5:36 a.m. There will be a total solar eclipse over the Faroe Islands and parts of the North Atlantic. A partial solar eclipse will be seen over a much larger part of the world, but not for us on the East coast of the U.S. Spring starts at 6:45 p.m.
March 21: The waxing crescent moon is near Mars.
March 22: In 1997, Comet Hale-Bopp made its closest approach to Earth. This was a once-in-a-lifetime comet whose distinct double tail stretched over 20 degrees through the sky for over a month. It sparked a serious interest in astronomy for thousands of people.
March 24: The moon crosses over the Hyades star cluster this evening and occults Aldebaran in Taurus for observers in Alaska and northwestern Canada.
March 25: In 1655, Christian Huygens discovered Titan, the largest moon of Saturn.
March 27: The first-quarter moon is at 3:43 a.m.
Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England.
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