Astronomical summer kicks off
This is the last weekend of spring 2017.
Just as Steve Miller sang in the rock classic “Fly like an Eagle” in 1976: “Time keeps on slipping, slipping, slipping into the future.”
Arguably, weather-wise it has already begun but astronomically summer officially kicks off at 11:24 p.m. Tuesday.
We can't exactly observe that directly this year because it'll happen after sundown. The sun reaches its most northern position in our celestial dome. Because of that the sun takes the longest, highest arc across our sky providing us with a maximum 15 hours and 7 minutes of official daylight from sunrise to sunset.
On Wednesday at midday, the sun will achieve a maximum altitude of a little more than 72 degrees above the southern horizon. At that time as you stand in the sun (if clouds don't photo bomb it) you'll cast the shortest shadow of the year. That'll actually happen around 1 p.m. because of daylight-saving time and our particular longitude in Butler. I know you don't want to hear this but from now until the winter solstice in late December our daylight hours begin their gradual decline. Sorry.
The longest days of the year obviously translate to the shortest nights, making it really tough on ardent stargazers. It's a late-night affair that's compounded with longer evening and morning twilights in our neighborhood of the northern latitude.
So summer stargazing requires an afternoon nap, at least for old star-geezers like me.
Once it finally gets dark, what's left of the spring constellations are hanging in the western sky. They aren't exactly all that flashy, at least compared to the winter constellations. There are a few decent ones though.
There's Leo the Lion, that kind of resembles the profile of a lion on his haunches but looks more like a backward question mark tipping over to the right.
Bootes the Farmer actually looks much more like a giant kite with the very bright star Arcturus adorning the tail.
This year, there's at least one superbright “star” among the spring constellations, the planet Jupiter. The big guy of our solar system and spring stars are gradually pushing to the west from night to night. By mid-to-late July most of them will already be below the western horizon before darkness sets in. Earth is turning away from that part of space as we orbit the sun.Meanwhile, in the early evening eastern skies the more compelling constellations of summer are on the rise and from week-to-week, they'll start out each evening a little higher in the sky.Among them are the three bright stars that make up what's known as the “Summer Triangle.” It's easy to spot. Just look in the northeastern quarter of the sky for the three brightest stars you can see and that's it.This giant triangle is really a great tool for getting acquainted the with the summer night sky because each of the stars is the brightest member in its respective constellation.The highest and brightest is Vega in the constellation Lyra the Harp. The second-brightest star is Altair on the lower right side of the triangle that is the brightest star in Aquila the Eagle. The third-brightest on the lower left of the triangle is Deneb, the brightest star in Cygnus the Swan, also known as the Northern Cross.Even though Deneb appears to be the dimmest summer triangle star, that's deceiving. In reality it's one of the biggest and most power stars in this part of our Milky Way galaxy.Our sun is a little less than a million miles in diameter, but Deneb may be as large as 200 million miles in girth. Deneb appears as the faintest star in the summer triangle because it's incredibly far away, at least 1,500 light years away.Just one light-year equates to almost six trillion miles, the distance that light travels in a year's time. That would make Deneb about 8,700 trillion miles away. Also because it's 1,500 light years away the light we see from it these warm summer evenings left Deneb around AD 500.If you're an early morning riser this first part of astronomical summer, the superbright planet Venus plays as the advance act for the sun as is rises in the eastern sky before and during morning twilight. The reason for its brilliancy is twofold.Our solar system's next door neighbor planet is only about 78 million miles away and its extremely thick and poisonous atmosphere is reflecting sunlight like crazy.Another cool thing about Venus is that even through a pair of binoculars it'll resemble a tiny half moon. Since Venus orbits the sun within Earth's orbit it goes through phase shape changes just like our moon.Make the stars your old friendsIf you have any astronomical questions or want me to write about something you're seeing in the night sky, drop me a line at mikewlynch@comcast.net.<em>Mike Lynch is an amateur astronomer and professional broadcast meteorologist for WCCO Radio in Minneapolis/St Paul and author of “Stars: a Month by Month Tour of the Constellations” published by Adventure Publications and available at bookstores and at http://www.adventurepublications.net.</em>
