During its annual trip around the Sun, our earthly spaceship is once again taking us through the spring constellations Cancer, Leo, Virgo, Boötes, and Ursa Major, shining high overhead in the middle of the night. But don’t miss the real show happening right in our celestial backyard, also known as the Solar System.
Take Venus, for example. The Evening Star dominates the western sky all month long, shining like a spotlight for three hours after sunset. The favourable tilt of the Earth’s axis relative to the plane of the Solar System provides a particularly clear and spectacular view of the sulfurous planet in the evening sky. Venus reaches its greatest elongation, 46 degrees to the left of the Sun, on March 24, allowing it to rule the dark sky alongside the stars of the constellation Aries as it heads toward a spectacular meet-up with the Pleiades cluster and Taurus in early April. And if the weather cooperates on the evening of March 28, we’ll be treated to an especially pretty scene, when a thin, four-day crescent Moon meanders a mere 7 degrees from Venus and the distant star cluster.
Mars overtakes Jupiter in pursuit of Saturn
In March, you’ll see Mars (both the month and the planet were named after Mars, the Roman god of war) moving quickly through the constellation Sagittarius, where it encounters Jupiter before rendezvousing with Saturn as dawn breaks in the spring sky. The three planets are clearly separate at the start of the month, forming a symmetrical pattern on the morning of March 4 and 5, with Jupiter sitting 8 degrees from Mars to its right and from Saturn to its left and outshining both by three magnitudes.
Even more striking will be the planets emerging into view before sunrise on March 18: Mars and Jupiter, a mere 1.3 degrees apart, will rise as one above the eastern horizon starting at 4:20 a.m. EDT. Minutes later, they will be followed by a magnificent lunar crescent less than 2 degrees beneath the planetary duo. If you don’t have a perfectly clear view of the horizon, wait a few minutes for the Earth to rotate so you can catch a better glimpse of this breathtaking sight.
And that’s only the first of many lovely encounters Mars will have before the month wraps up. On March 20, the Red Planet catches up to giant Jupiter and the two will be just 0.7 degrees from each other! On March 23, experienced observers equipped with a good telescope can take advantage of a very close Mars-Pluto conjunction (only 0.11 degrees apart) to spot the distant dwarf planet. Then on March 31, it’s finally Saturn’s turn to get a visit from Mars, less than 1 degree away. The two planets are easily visible to the naked eye and shine at about the same magnitude, a rather rare sight that will doubtless be immortalized by many amateur astrophotographers!
Remember that as the planets revolve around the Sun, we see all these close encounters from a constantly changing perspective from our vantage point on Earth. Mars (about 230 million kilometres from Earth by mid-month) won’t really be closer to Jupiter (~820 million kilometres), Saturn (~1.5 billion kilometres) or Pluto (~5.1 billion kilometres), nor will it be aligned in their respective orbits.
The equinox, or the start of a new cycle
Many calendars—Mesopotamian, Roman, Persian, Indian, among others—have used or still use the spring equinox (also called the March or vernal equinox) as the date of the New Year, as do modern astronomers, to some degree.
The tilt of the Earth’s axis causes the Sun’s rays to align with or shine directly over the Earth’s equator only two times in the year. Of those two dates, ancient astronomers chose the spring equinox as the reference for establishing the astronomical coordinate system, also called the equatorial system, which is still used today. This year, at exactly 11:50 p.m. (EDT) on March 19, 2020, the Sun will be directly above the equator, east of the Indonesian island of Sulawesi, when it crosses the starting line and returns to the zero-point for right ascension in the equatorial system.
Those two moments in the year are also when the Sun spends the same amount of time above the horizon as below, hence the term “equinox” derived from the Latin words aequus and nox, meaning equal and night, respectively. However, given that the Sun is already up when the centre of the disc becomes visible above the horizon, and that the Earth’s atmosphere refracts sunlight, it is not entirely true that day and night are exactly equal on the equinox. This spring, the exact—or nearly exact—division of day and night in southern Québec actually happens two days earlier, on March 17.
Finally, daylight savings time begins the night of March 7-8: Remember to set your clocks ahead by one hour so you don’t miss the start of the new cycle!