The month of March is named for Mars, the Roman god of war, but it is also known as the guardian of agriculture and as an ancestor of the Roman people. March was also the first month of the year on the early Roman calendar.

For us in the northern hemisphere, March always marks the beginning of spring. This year that will happen on Tuesday the 20th at 12:15 p.m. The vernal equinox is further defined as the sun on the ecliptic crossing over the celestial equator on an upward path, also called an ascending node. This will be one of only two days each year when the sun will rise due east and set due west for everyone on Earth, except for the poles. The days also will be 12 hours long for everyone within a few days of that date, except for the poles.

There will be some warmer days and nights now that spring will have arrived, so it’s time to get outside more often to look up and enjoy the night sky and some of its myriad phenomena. The highlights for this month include a great conjunction of Venus and Mercury in the evening sky, a close conjunction of Mars and Saturn in the morning sky, several nice conjunctions of various phases of the moon with planets, and Mercury’s best evening appearance of the year.

This month starts out with Venus and Mercury less than 2 degrees apart low in the western evening sky just 20 minutes after sunset in the constellation of Pisces the Fish. On Saturday evening the 3rd, brilliant Venus will be just 1.1 degrees to the left of Mercury. That can be measured by holding up one finger at arm’s length. They will still be very close the next evening, but Mercury will be a little above Venus by then.

Through a telescope you will see that Venus is 97 percent full at the beginning of March but that it’s getting less illuminated by the sun as it gets closer to us again. Mercury also goes through phases like the moon for the same reason, but it will be 90 percent lit at the beginning of March and down to just a few percent as it disappears again toward the end of the month.

Even without a telescope or binoculars, you will notice that Venus is about eight times brighter than our first planet as March begins, but then Venus will be fully 100 times brighter than Mercury by the time it disappears again around the time that spring starts on the 20th. Watch for three nights in a row as a slender waxing crescent moon joins the pair of our first two planets from the 18th to the 20th.

Many people have never seen Mercury because it always stays close to the sun and therefore never gets very high in our sky. Now is your chance. Mercury is a strange planet, without any moons, that orbits the sun very fast at 30 miles per second every 88 days and takes 59 days just to rotate once on its axis. That is a 3-to-2 ratio. It is also very dark and reflects even less sunlight than the moon, which only reflects about 8 percent of the sunlight that hits it back into space, absorbing the remaining 92 percent. The Earth reflects just over one third of sunlight back into space.

Named for the Roman god of commerce and thieves, Mercury has no atmosphere and is so close to the sun that it has the widest temperature range of any planet in the solar system. It will reach more than 800 degrees on the sun side and drop down to minus 300 on the night side every day, a difference of 1,100 degrees.

The last mission we sent there was appropriately called Messenger, and it solved some mysteries but raised many more about this enigmatic first planet. Mercury has a very heavy metal core that is 60 percent of its mass, twice that of any of the other terrestrial planets.

Jupiter will have just switched into an evening planet as March begins, and it will be rising an hour earlier by the end of March. The king of the planets is in Libra the Scales now, and will continue to get a little higher and brighter each night as it gets closer to us, approaching its opposition on May 6, when it will rise at sunset and remain in the sky all night long.

Jupiter will end its normal, direct, eastward motion through our sky on March 9, thereby beginning its 4-month-long retrograde loop, the midpoint of which is its opposition. Notice that you can see several of its large Galilean moons just in a pair of binoculars.

The remaining bright planets are still morning planets this month. Mars begins the month rising around 2 a.m. and Saturn begins by rising at 3 a.m., but Mars catches up rapidly, and they both rise just after 1 a.m. by the end of March, in Sagittarius. They will be less than 2 degrees apart by then, having started the month 17 degrees apart. Notice that they both start at about the same brightness but that Mars will get brighter much faster than Saturn. It is still too early to discern any features on Mars in a small telescope, but be aware that Mars is getting closer and brighter every day, and it will be at its best on July 29, which will be one of its closest oppositions in many years.

Notice that the waning crescent moon will pass just above Mars and then Saturn one hour before sunrise on the mornings of Saturday the 10th and Sunday the 11th, creating a good photo opportunity.

MARCH HIGHLIGHTS

March 1: Full moon is at 7:52 a.m. This is also called the Worm, Crow, Sap or Lenten moon.

March 2: Notice that the moon, Jupiter, Mars and Saturn are nicely spaced in a giant celestial arc on the ecliptic in the morning sky.

March 3: Venus and Mercury are only one degree apart low in the western evening sky right after sunset in Pisces.

March 5: The zodiacal light might be visible for a couple more weeks, low in the western sky about 90 minutes after sunset. Challenge yourself to find this tall, hazy pyramid of subtle light caused by reflected sunlight off comet dust and debris forming a torus all along the ecliptic plane of our solar system. I have seen it twice.

March 7: Jupiter and the waning gibbous moon are less than 4 degrees apart just before midnight as they both rise together.

March 9: Last-quarter moon is at 6: 21 a.m.

March 11: Daylight-saving time starts at 2 a.m.

March 13: Sir William Herschel discovered the planet Uranus on this day in 1781. He first named it George in honor of the king but it was soon renamed after the Greek father of the Titans, whose name also means “the heavens.” This planet will be about 4 degrees above and to the right of Venus on March 28, but the twilight will be too bright to see it without a telescope or good pair of binoculars.

March 14: Albert Einstein was born in 1879. He discovered general relativity in 1915 but couldn’t develop a unified field theory that links the world of the very small, quantum mechanics with the world of the very large.

March 16: Caroline Herschel was born in 1750. She discovered eight comets and worked closely with her brother, William, throughout her career.

March 17: New moon is at 9:13 a.m.

March 20: Spring starts at 12:15 p.m.

March 22: The moon is less than 1 degree from Aldebaran this evening, occulting it for parts of this country.

March 24: First-quarter moon is at 11:36 a.m.

March 29: Mars and Saturn are only 2 degrees apart in the morning sky. Look for the globular cluster M22, with about 100,000 stars about 1 degree below the pair of planets.

March 31: The second full moon this month is at 8:38 a.m.

Bernie Reim of Wells is co-director of the Astronomical Society of Northern New England

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