~ St. Maarten’s Backyard Astronomy for September 1 & 2 ~
Sun rises at 5:58am
Sun sets at 6:27pm
Lunar phase: 3rd qtr. - waning gibbous
Moon rises at 10:52pm
Moon sets at 11:04am
Break out those telescopes or binoculars! We are being visited by a comet! It is in our sky right now! Don’t be fooled by cartoon images of comets swooshing through the sky like a shooting star; comets only seem to move if you study their location relative to the background stars over a period of time, several nights, even weeks! Looking at one for entire night is like watching grass grow; it will not appear to move at all. However, using a small telescope, if you carefully observe which stars are close to the comet’s head, and then compare the view just 15 or 30 minutes later; you will be able to detect its motion. Comet 21P is travelling through space at 50,555 miles per hour (81,360 km/h) relative to the Earth.
Comet 21P/Giacobini-Zinner is currently being viewed by small backyard telescopes and it’s about to come closer to Earth than it has in 72 years! If that isn’t enough, there is another comet on its way and it will come even closer later this year. It’s Comet Wirtanen, and it will venture so close to the Earth that by December, it might even become visible to the unaided eye.
Comet 21P/Giacobini-Zinner – called simply 21P by astronomers – is currently approaching the Earth and sun at incredible speeds (about 14 miles/second, or 23 km/s). Its closest approach to both the Earth and the sun takes place on the same day – September 10 – when this comet will sweep past Earth at a completely safe distance of 36 million miles (58 million km) from our planet. That’s nearly as far from us as the next planet outward in orbit – Mars – is right now. But, for a comet, it’s relatively close.
During the first half of September, comet 21P will be visible with binoculars. Around this time, 21P will be passing in front of the constellations Camelopardalis, Perseus, and Auriga. Because 21P’s closest approach to Earth is the night of September 9-10, this would be a great night to get a glimpse of it. On that date, it will be visible in front of the constellation Auriga (see image). Using binoculars or a small telescope, you should be able to find the comet as a fuzzy patch of light.
Although the nucleus of comet 21P is estimated to be just over a mile wide, it has an atmosphere about twice the diameter of Jupiter! Some images show the comet’s coma as a green colour, which indicates the comet has cyanogen and diatomic carbon, gases that glow green when they’re illuminated by sunlight.
Comet 21P was discovered on December 20, 1900, by Michel Giacobini from France, and then was seen again or recovered by Ernst Zinner from Germany in October 1913. It is a frequent visitor to Earth, with an orbit around the sun lasting 6.6 years.
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.
