By David Ward
One of these fine October evenings, look straight up over head for one of the most amazing stars in the sky, Deneb. It belongs to three different star groupings – the head of the Northern Cross, the tail of Cygnus the Swan, and one of the three points of the Summer Triangle. Its Arabic name means “the tail of the hen.”
Deneb’s claim to fame is its brightness. It is by far the most luminous star visible in the sky, shining at a whopping 200,000 times brighter than our sun. So why does it not appear to be the brightest star up in the sky?
That is because it is a long ways out there. No one really knows for sure how far away it is because its distance is at the limit of triangulation, a simple method of trigonometry that astronomers use to calculate the distance to the closer stars. Some of the latest estimates place it at a distance of 2,600 light years away. That means if you are out gazing at Deneb, those little photons hitting your eyeballs left that star 500 years before Julius Caesar of Rome was born! Remember that those photons travel so fast they can buzz around the Earth seven-and-a-half times in one second. So Deneb is not only the most luminous star we can see, it is also far, far farther away than all the other stars that up there.
Take a look at the bright stars Vega just west of Deneb and Altair to the southwest. These are the other two stars in the large star grouping known as the Summer Triangle. They are in our stellar neighborhood, not right next door but just down the block a piece, you might say. If Deneb were as close as either Vega or Altair, it would shine 15 times as bright as the planet Venus and cast shadows by its light!
Deneb is a big star and big stars gobble up their fuel as voraciously as pigs at the sty. Our smallish sun conserves its fuel to last billions of years, which is one of the many reasons we happen to find ourselves on this little planet. There has been time enough for advanced life to develop here.
Deneb is much younger than our sun and in a few million years it will blow itself to smithereens in a supernova explosion. When that happens it may briefly shine brighter than all the 200 billion to 300 billion other stars in our galaxy put together. If Deneb had any planets circling around it, life would not have had time to develop anything more complex than a microbe there.
Have you ever wondered where you are going in life? Maybe you are driving down to Costco in Wenatchee this weekend or catching a plane to Hawaii for a vacation. In the big picture the answer to that question lies in the stars. Guess what? You are really going to Deneb!
Our sun is revolving around that giant merry-go-round of stars in the sky we call the Milky Way Galaxy headed toward that very distant, very luminous star, dragging Earth along with it. When will we get there? You would think that traveling at a speed of over 500,000 miles per hour we might arrive at some point in the foreseeable future. Actually, the answer is “never” because Deneb is not sitting still either. It is cruising along also, forever ahead of us and out of our reach.
If all these big numbers are making your head spin, try looking for something a lot closer to home. Low in the southwest just after sunset, the planet Venus shines brighter than anything else up there besides the sun and moon. At only 40 million or 50 million miles distant from us it is practically a stone’s throw away! Watch a small crescent moon dance with the goddess of love on the nights of Oct. 7 and 8.
If you are up late the planet Jupiter shines brightly in the stars of the constellation Gemini the twins in the east. Jupiter will be a beautiful addition to the bright stars of winter again this year.
Do not forget to look up every now and then from our tiny little world and gaze at the wonders of the big amazing universe in which we live.