By David Ward
I am going to give you something easy this month. See if you can find the brightest star in the sky.
How hard could that be? If that sounds too difficult, however, then stay inside and spend the rest of the winter watching TV. If you are game, go out early in the evening and look southeast for a bright white star. It will probably be furiously twinkling.
If there is a hill or your garage in that direction, your view of it may be blocked. Try going someplace else. Want to make sure you are seeing the right star? Look above and to the right for Orion’s Belt, three bright evenly spaced stars all in a row. There is nothing else in the sky quite like it. Extend the line of those three stars down and to the left. They point right to the brightest star in the sky. It is called Sirius.
Some stars appear bright to us because they are very luminous and some because they are close by. Sirius is a bright star, 25 times brighter than our sun, but that is not unusual. Almost every star you can see up there with your naked eye is brighter than our sun, some spectacularly so.
The main reason Sirius looks bright is because it is close. Actually, it is the nearest bright star up there. It is not our next-door neighbor but just down the block, so to speak. How close is it? We measure the distance to the stars in light-years, the distance that light travels in a year. Light is no slowpoke. It cruises along at 186,000 miles a second. In a year it covers a lot of ground, about 6 trillion miles.
Imagine a trillion
Even though the number trillion is tossed around quite a bit, like in reference to the national debt, it is hard for us to really grasp what a large number it is. Here is an example: A billion seconds ago happened in the year 1985. A trillion seconds ago happened in the year 29,692 B.C. Sirius is 8.6 light years away, which translates to about 51 trillion miles. If you were going to take a non-stop Alaska Airlines flight there, it would take about 10 million years. Better bring a good book to read!
Remember, Sirius is about the closest bright star we can see. It is really two stars in one, and there is nothing unusual about that. Most of the stars we see in the sky are two, three or four stars together. It takes a telescope to reveal their multiplicity. There is another tiny star revolving around Sirius known as a white dwarf. It is only about the size of the earth and it is almost at the end of its life cycle.
Our sun will morph into one of these billions of years from now. Too dim and too close to Sirius to be seen, it is really heavy. Scoop up a teaspoon of it and bring it to earth and it would weigh as much as an elephant, about five and a half tons.
When you look at the stars, it is like having your own personal time machine, because you are actually looking back in time. Looking at Sirius you are looking 8.6 light-years in the past. That is how long its light takes to get here. Does it look the same right now? Almost certainly so, as stars do not change very much in the short term.
Where we’ve been
Another interesting thing about looking at Sirius is that you are looking at where you have been. Our sun is traveling through space at about 500,000 miles an hour, dragging the earth and the other planets along for the ride, headed for the star Vega. Sirius is opposite Vega in the sky, so looking at the brightest star in the sky is like looking out the rear window of your car.
Look west during the evening twilight for the brilliant planet Venus, even brighter than Sirius. Notice that it is not twinkling like the bright stars. If it is shining steady and bright, it is probably a planet. Twinkling is not an attribute of the stars themselves, but is caused by our atmosphere refracting the light of the stars.
Just above and to the left of Venus look for much dimmer and slightly reddish Mars. On the evening of Feb. 1, Venus, Mars and a slim crescent moon will be close together, all in a row, in the west during the evening twilight.
In early February the planet Jupiter rises just before midnight. Look for it high in the south if you are up before dawn. Also you might catch a glimpse of Saturn low in the east before sunrise.
In case you missed it, another asteroid buzzed us in January. This one was close, too close for comfort. It missed us by a hairbreadth, astronomically speaking, closer than the moon. It was big too, the size of a 10-story building. They are supposed to be watching out for things like that but they only saw it two days in advance. It would have probably flattened the state of Washington if it had hit anywhere near here. If you do not have enough to worry about these troublesome days, you can add asteroids to your list.