Sun rises at 6:45am
Sun sets at 5:51pm
Moon phase: third quarter, waning
Moon rises at 10:48pm, Saturday
Moon sets at 11:05am, Sunday
Star gazing is always good during January evenings as the stars seem brighter than in the summer nights. Why is that? The reason, in part, has to do with our planet’s window on the galaxy. During the winter months, especially these lovely January evenings, the part of Earth you’re standing on is facing out (or away from) the centre of the Milky Way galaxy.
Summer evenings, the sky seen from the entire Earth is facing toward the centre of the Milky Way galaxy. The galaxy is about 100,000 light-years across, and its centre is some 25,000 to 28,000 light-years away. We don’t see into the exact centre of the Milky Way, because it’s obscured by galactic dust. But during those Northern Hemisphere summer months (Southern Hemisphere winter months) as we peer edgewise into the galaxy’s disk, we’re gazing across some 75,000 light-years of star-packed space, thus – on June, July and August evenings – we’re looking toward the combined light of billions upon billions of stars.
But at this time of year, we’re looking the opposite way – towards the spiral arm of the galaxy. And as luck would have it, there are some gigantic stars located in this direction, and they are relatively close to us – in our own neighbourhood, so to speak.
Our spiral arm of the galaxy is called the Orion Arm, or sometimes the Orion Spur. It’s not one of the primary spiral arms of the Milky Way, only a “minor” spiral arm. Our sun, the Earth, and all the other planets in our solar system reside within this Orion Arm. We’re located close to the inner rim of this spiral arm, about halfway along its length.
The stars of the familiar Orion constellation also reside within the Orion Arm of the Milky Way. In fact, our arm of the galaxy is named for this constellation.
Look for the constellation Orion the Hunter in the east, as soon as the sky is dark. It’s probably the easiest to pick out his “belt,” three medium-bright stars in a short, straight row located at the mid-section of the Hunter. These stars are named Mintaka, Alnilam, and Alnitak and each of these is actually a double star, as seen when viewed through a powerful scope. There’s plenty more to see in Orion, too, and it’s easy to find. The two brightest stars in Orion are Betelgeuse and Rigel. If you imagine Orion facing you, then Betelgeuse is his right shoulder, and Rigel is his left foot. One of the most studied spots in the sky is a nebula located below the belt, in a smaller alignment of three “stars.” These are often thought of as a knife hanging from his belt, and this is easily observed to be a gas cloud rather than a true star with a fair pair of binoculars.
Stars in distinct constellations like Orion look connected, perhaps even gravitationally bound, but usually they aren’t. Certainly Orion’s stars aren’t bound to each other by anything but their general location near one another along a single line of sight from Earth. The stars of Orion just happen to make an easy visual pattern on our sky’s dome.
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.
