Just after it gets dark, check out the two planets hanging in the southwest twilight glow. The bright one is Jupiter and its dimmer companion to the left is Saturn. If you look at the night sky a lot like I do, you might notice that over the past few months, they have been getting closer together. What does it mean? They are headed for a grand conjunction when the two largest planets in our solar system appear close together in the sky.
An event like this happens about every 20 years. This year on Dec. 21, the night of the winter solstice, we will be treated to a very special conjunction when the two planets are closer than they have been since the year 1623. Do not worry, they will not run into one another. They are not particularly close in space, but just happen to line up in our line of sight, so to speak. Jupiter is about 513 million miles from earth and Saturn about 964 million miles distant so there is plenty of room between the two.
Historically, grand conjunctions garnered a lot of attention since they were thought to be celestial omens. The early astronomer Johannes Kepler, who was the first to really figure out the motions of the planets, postulated that the Star of Bethlehem was a grand conjunction of Jupiter and Saturn that appeared in the sky about the time of the birth of Jesus. Maybe with all the turmoil in our country right now it is an omen for us too.
To witness this event you will need to find a place with a clear view low into the southwest. Start looking not long after sunset, maybe about 45 minutes or so, before the sky is completely dark. You will probably not be able to distinguish the two planets separately so bring your binoculars or better yet, a small telescope. They will both fit simultaneously in the same field of view. If you do not want to miss it, start looking a week or two ahead of time when Jupiter and Saturn will not be so low to the horizon but still pretty close together.
Back to Betelgeuse
Over in the east, the constellation Orion is rising after a long summer nap. In his upper left-hand corner, the star Betelgeuse shines with an easily noticeable orange-reddish light. You may remember last winter when everybody was talking about this peculiar star and its strange antics. Betelgeuse is a star in the last stages of its life and is expected by astronomers to blow up at any time. You should probably know that astronomers may use the word “anytime” somewhat differently than we do. They are talking about tens of thousands of years from now which in the life of a star is just a heartbeat.
Last winter, Betelgeuse suddenly and inexplicably grew considerably dimmer over the period of a few weeks. We all held our breaths in expectation of a spectacular show perhaps a fireball exploding in the sky. Now the star has resumed its normal brightness and astronomers blame the dimming on a giant cloud of dust belched out of Betelgeuse, not nearly as exciting as a supernova explosion. I will keep an eye on it for you, and let you know if anything exciting is happening.
Do you want to see some really far away stars? Take a look at the three bright stars of Orion’s Belt. Find them to the right and below Betelgeuse. They are easy to spot because they are all in a row and of equal brightness. All of them are so far away that their light has been traveling to us for over a thousand years. The middle one, known as Alnilam, takes the prize. It is so far away that no one knows for sure how bright it is or how far away it is. It shines possibly as bright as almost a million of our suns and its light that you are seeing may have started its journey towards us at about the time of the Trojan War. Now that was a long time ago!
After the winter solstice, and after what seems like forever, the days will start to get longer again. I promise.