Crazy June bugs are banging against the door at night, landing on their backs, then sputtering back into the air with a heavy buzz. My dad’s side of the family hails from Kentucky and Tennessee. As a kid, my cousins in Pineville, Kentucky showed me how to tie a string to a June bug and spin it in a circle to start it buzzing. Fireflies and long twilights are back as well, so yes, it must be June.
Deneb, Vega and Altair describe one of the sky’s most familiar patterns — the Summer Triangle. This map shows the sky as you face east around 10:30 p.m. Created with Stellarium.
As summer edges in, so do the constellations of the season. We looked at Scorpius last week, the claws and head of which are pushing up in the southeast as steadfastly as dandelions in my yard. Not far behind is the Summer Triangle, a familiar pattern of three bright stars enclosing a substantial piece of triangular skyscape.
A bright portion of the Milky Way passes between the three stars at the apices of the Summer Triangle. Deneb (at left) is smack in the middle of the Milky Way band while Vega and Altair lie above and below it. Photo: Bob King
My younger daughter noticed the trio as we sat around the bonfire this weekend. As the moon continues to fill out in the coming nights, the fainter stars will fade in its light but not Vega, Deneb and Altair. They stand out all the better without the competition of their dimmer brothers and sisters. In the photograph you’ll notice that the Milky Way courses directly down the middle between the three stars. It’s a small section of the Milky Way galaxy, home to all the stars we can see. The sun and its family of planets are located in the thick part of the flattened disk of the galaxy and orbit about its center every 220 million years.
This is a 360 picture of the entire Milky Way galaxy taken by the COBE satellite. The sun (yellow dot) is located a little more than halfway from the center to the edge of the galaxy. I’ve greatly exaggerated the sun’s size and the size of Earth (blue dot) and its orbit so you can see how we’re tipped in relation to the Milky Way’s disk. Image credit: NASA
What’s perhaps less well known is that the orbits of the planets are tipped about 60 degrees in relation to the disk. Since the plane of the planet’s orbits defines the zodiac, and that plane is tipped almost vertically to the galaxy’s pancake-like disk, we see the Milky Way band tipped at a steep angle to the zodiac constellations. It’s funny to think that Earth moves through the galaxy on an orbit tilted at such a steep pitch. We’re so used to seeing the solar system laid out nice and flat we rarely think about it in relation to the galaxy.
The Milky Way (right) and the zodiacal light (left), which lies along the zodiac, intersect near Sagittarius in this photo taken from the southern hemisphere. Credit: Yuri Beletsky / ESO
The ecliptic or zodiac — the path the planets, sun and moon take through the sky — and the Milky Way describe two great circles in the heavens that intersect at Gemini and Sagittarius. Such grand forms played about our heads as my daughter and I pulled our chairs closer to the fading fire.