EYES TO THE SKY: Summer nightlife, Summer Triangle, Jupiter’s triangles, Mercury
June 24 – July 7, 2019
Mount Washington — Upon opening the door and stepping over the threshold into the darkness at solstice time, this stargazer is bathed in wild sounds of trilling toads and tree frogs. A universe of musical sounds coming from a nearby pond fills the airwaves around me. Simultaneously, star-like flashes, brilliant pulses emitted by insects – fireflies, lightning bugs – are blinking on and off above the ground and up to the treetops. Waves of light and incandescent streamers float on the air and vanish. I am in the midst of communities of animals communicating with each other, loudly. All of us are at the edges of wildlife habitat that is inside and beside human neighborhoods. I had yet to look up to find my bearings in our solar system and the starry cosmos.
Stargazing begins about four hours later at summer solstice time than around the winter solstice! Sunset, now the latest of the year, 8:34 p.m. in our locale, is followed by long, lingering twilight. Nightfall is not until around 10:45 p.m. In between, about an hour to an hour and a quarter after sundown, the brightest stars and planets are visible.
Within 60 to 75 minutes of sunset, let us look close above the west-northwest skyline for planet Mercury. It is the smallest planet in our solar system and closest to the Sun. Observe from a location with a view to the horizon and bring binoculars. Know that Mercury sets at 10:08 p.m. tonight. The planet’s current apparent magnitude is 0.64, bright as a first magnitude star like Altair, 0.75m, in the Summer Triangle. Whereas Altair’s magnitude remains constant going forward, Mercury dims and, of more significance, sets a minute or two earlier every night this week. It is a challenge to spot Mercury and a triumph when we do.
Turning to the southwest, to the left, look up to locate the bright orange star, Arcturus, close to zenith. Below Arcturus, brilliant Jupiter shines 22 degrees above the horizon. To the planet’s left, Altair marks the base of the Summer Triangle. As darkness gathers, see Deneb above and to the left, at the northeast corner of the great Triangle. To its right, find brighter Vega.
Note the large equilateral triangle shaped by Vega, Arcturus and Jupiter. This triangle is not a fixed constellation or asterism, given that Jupiter does not keep its position in relation to the stars. I made it up and trust that you will find other shapes prompted by the addition of Jupiter to the layout of the familiar stars.
Light pollution map
Lamps and lighting – http://galileo.graphycs.cegepsherbrooke.qc.ca/app/en/home
Opportunities to participate
July 26 – August 4, Summer Star Party, overnight camping in Plainfield, Massachusetts