~ St. Maarten’s Backyard Astronomy for March 10 & 11 ~
Sun rises at 6:24am
Sun sets at 6:20pm
Moon phase: third quarter, crescent, waning
Moon sets at 12:35pm, Saturday
Moon rises at 2:14am, Sunday
We had a gorgeous full moon last weekend, and even through the early week, it rose over the eastern horizon with breath-taking largesse. This weekend, we will enjoy seeing a bold, late-rising “half-moon” and she will make a series of visits to some of the visible planets as she crosses the night sky. On Thursday, March 7, the moon passed Jupiter at midnight, and tonight (Saturday) she heads for a close encounter with Mars then on Sunday, she brushes by Saturn.
Jupiter is a brilliant star-like object, the fifth planet outward from the sun and the second-brightest celestial object (after the moon) to light up the morning sky. Venus is a brighter planet than Jupiter, but Venus is now in the early evening sky and will remain an evening “star” until October.
Jupiter, meanwhile, comes up around midnight this weekend, and it shines high in the sky at dawn. Jupiter is bright because it’s so big. It’s the most massive planet in the solar system, and it’s covered with a thick and very reflective cloud cover.
All the planets tend to “wander” across the celestial sphere of the night sky. While the true stars are “fixed” in place on the sphere, the planets take a path amid the stars. The word “planet” actually means “wanderer.” Sometimes, the planets will switch direction for a while, this is what astronomers call “retrograde motion.” Jupiter’s retrograde phase is just beginning.
Yesterday, March 9, Jupiter was stationary in front of the constellation Libra, signalling the beginning of its backtracking period. Why do they do this? It took early stargazers centuries to figure it out. It’s because of how each planet orbits the sun, like runners on a track. The inside runners have a shorter path, and will sometimes overtake the outer runners, even if the outer runners are going faster. Our view is that of the earth’s position, the third planet out from the sun. As we come around in our orbit; for a short time, we pass Jupiter so relative to our point of view; Jupiter appears to be moving backwards. The beginning of Jupiter’s retrograde motion on March 9 marks the beginning of this special time!
Mars and Saturn also shine brilliantly. Look for them now well after midnight, or, perhaps easier, any morning before dawn. This weekend is a great time to look for them, when the moon is sweeping past.
You can discern Saturn from Mars by colour. Saturn appears golden while Mars glows red. If you have difficulty distinguishing colour with the eye alone, try looking at these colourful celestial gems with binoculars. Or, if you have a telescope, you can easily tell which one is Saturn because of its majestic rings, which are quite visible in even a modest backyard telescope. Saturn is the most distant world you can easily see with the unaided eye.
By the way, 2018 is set to be a banner year for Mars; but this year, Mars will outshine Jupiter for roughly two months, from early July to early September. Why? Because the earth will be passing between Mars and the sun during that time.
Thank you for keeping up with the Night Sky articles. If you are out later on in the week, each star rises about four minutes earlier each day than written here, and the moon rises 50 minutes later. Night Sky is researched and compiled by Lisa Davis-Burnett. Earthsky.org is a key resource for information and images. Questions or comments? Email This email address is being protected from spambots. You need JavaScript enabled to view it.
