What’s Up in the Night Sky? – March 2020

Fred Barrett | Mar 04, 2020

Did you know that the Moon is slowly moving away from the Earth? Planetary scientists are pretty sure that the Moon is the result of a glancing collision with another huge planetary body some 4.5 billion years ago. The debris from that glancing blow coalesced over a few million years into the Moon that we know now. At that time the Moon orbited Earth at a distance of about 80,000 kilometers (50,000 miles). When Apollo astronauts landed on the Moon, they left reflectors on its surface and then measured the time it took for a laser pulse to travel there and back. Since the speed of light is constant and you know the time it took the pulse to go to and from the moon, the distance can be calculated with high accuracy. When you take measurements over a few years, you can then see the rate at which the Moon is moving away. That movement away is about 3.8 centimeters (1.5 inches) per year. The moon is now at a distance, on average, of about 380,000 Kilometers (237,000 miles). It’s moved pretty far in 4.5 billion years! It’s a fortunate coincidence that we have total solar eclipses because at its current distance, the Moon appears the same size as the Sun as it passes between us and the Sun and therefore covers it perfectly. This allows scientists to study the Sun’s atmosphere - the corona. It provides the rest of us, lucky enough to be in the right place, a beautiful natural wonder. Of course, the egghead scientists likely find it beautiful too! The question is: why is happening? Well, the Earth and the Moon pull on each other due to their mutual gravity and this causes the ocean tide that occurs twice every day. Because the Earth rotates, the bulges (high tide) that form in the ocean due to gravitational attraction, actually occur slightly ahead of the Moon and not directly beneath it. The Moon, as a result, is attracted by the increased mass of water in front of it and this very, very slightly increases the speed of its orbit. The faster the Moon moves, the larger its orbit around Earth becomes. Thus it continues to move a miniscule distance away.

Another consideration enters the mix. The Moon also attracts the Earth. The tide it causes creates friction and this slowly reduces the rotation rate of the Earth. Way back, not only was the Moon much closer to our planet, but the Earth was rotating much faster. The rotation rate will continue to slow as the Moon moves slowly away. Eventually the time it takes the Moon to orbit the Earth will be the same as the Earth takes to make one rotation and at that time, it will be about 47 of our current days. This will happen in roughly 50 billion years. But not to worry, the Sun’s life span will end in about 5 billion years and we’ll have been long swallowed up by a Red Giant Sun. I don’t suppose we should be overly worried about that distant fate.

Venus still dominates with its brilliance in the western sky for about 3 hours after sunset. Here’s a chance to attempt an easier observation of distant Uranus. Pull out your binoculars and look about 2 degrees southeast of Venus on March 7th and 8th. Uranus is roughly 1.9 billion miles away and that’s 24 times the distance to Venus. Looking west on March 24th the sky will present a stunning view of the constellation Orion and down to the right, the Hyades star cluster, the Pleiades and the constellation Perseus. Star looking about an hour after sunset. If you have a telescope, keep track of Venus. Its disk increases in size as the month progresses, it goes from19 second width to 26 seconds; a large increase. Before dawn (about 5 am) in early March, you can observe Mars, Jupiter and Saturn along the elliptic in the southeast. If you check every few days, you will note that Mars moves past both during the month. On the 24th Mars sits about half a degree south of Jupiter. The 3 planets are clustered together March 25th and 26th and this hasn’t happened in 20 years. Also note that Mars will be right between Jupiter and Saturn. There’s eye candy for during all in the evenings and early pre dawn mornings. Don’t forget to watch for the cone shaped Zodiacal light above the western horizon during March. Since the Full Moon this month is on March 9th, the best time to view the light is after March 14th or so and before the Moon rises.

Monthly highlights:

March 2nd: First quarter Moon.

March 7th and 8th: Uranus is 2 degrees southeast of Venus.

March 8th: Daylight Savings time begins at 2 am.

March 9th: Full Moon. This is the Full Worm Moon. As spring springs, hopefully early this year, watch out for worms underfoot. Robin Redbreast shows up too. It’s also called the Full Sap Moon. No, I’m not referring to anyone in particular. It’s the time to get your sproules and buckets out and ready yourself for the Maple tree sap to flow.

March 10th: The Moon is at perigee – 355,000 Kilometers.

March 16th: Last Quarter Moon.

March 17th: Saint Patrick’s Day. Some people will be seeing stars the next day!

March 18th: Moon is 0.7 degrees south of Mars - 4 am. Moon is 1.5 degrees south of Jupiter – 6 am. Moon is 2 degrees south of Saturn – 8 pm.

March 19th: Spring or Vernal equinox.

March 20th: Mars is 0.7 degrees south of Jupiter.

March 21st: Moon is 4 degrees south of Mercury; an observing challenge.

March 24th: New Moon. Moon is at apogee – 404,300 Kilometers. Mars sits about half a degree south of Jupiter.

March 26th: Observing challenge: Moon passes 4 degrees south of Uranus at 5 pm EDT.

March 28th: Earth Hour – 8:30 to 9:30 pm. www.earthhour.org . Moon passes 7 degrees south of Venus – 7 am EDT.

March 31st: Mars is 0.9 degrees south of Saturn – 7 am EDT.

That’s a wrap. Keep looking up! Jupiter and her dancing moons – Callisto, Io, Europa and Ganymede are a treat in the early morning!

“The Beginner’s Observing Guide by Leo Enright is an invaluable companion for adventures in the sky. It also contains useful star charts. It can be ordered from the Royal Astronomical Society of Canada at www.rasc.ca/publications. A subscription to our very own excellent Canadian astronomy magazine “SkyNews” can be arranged at the RASC website as well.

Let me know how your observing has gone this month, especially anything unusual. I enjoy the feedback. If you have any questions or suggestions you can contact me through this paper or email me at This email address is being protected from spambots. You need JavaScript enabled to view it. . Clear Skies! Fred.