Bakersfield Night Sky – June 18, 2011
By Nick Strobel
The soonest interesting astronomy event will be the summer solstice when the Sun's position on our sky is as far north of the celestial equator as it will be all year. This happens on June 21st (Tuesday), at 10:16 AM Pacific Daylight Time to be more precise. People at the latitude of the Tropic of Cancer (23.5 degrees North) will see the Sun directly overhead (at the zenith) at their local noon. We are too far north to ever see the Sun ever get directly overhead at the zenith but on this day the Sun will get at its highest point at mid-day all year. The summer solstice also officially marks the beginning of the season of summer, even though the daytime temperatures may tell us that "summer" began a lot sooner than that!
During the spring and summer, our part of the Earth is tipped toward the Sun so the Sun's energy hits our part of the Earth more directly and the Sun is above the horizon for a longer time than during the fall and winter. With more concentrated solar power and longer daylight, our part of the Earth will get a bit warmer. All this despite the fact that the Earth (even our part of the tipped over Earth) is farthest from the Sun in the summer. The Earth reaches the farthest point of its orbit from the Sun on July 4th (at about 8 AM Pacific time this year). No, variable distance is NOT the reason for the seasons—it all has to do with the angle of the Sun. To explore more about the seasons (and view helpful graphics), see my freely available astronomy textbook, Astronomy Notes, at www.astronomynotes.com and go to the third chapter in it.
In tonight's sky, Saturn, Spica, and Arcturus still form a nice isosceles triangle in the southern sky at around 9:30 PM that I described in my previous column --- see the second chart below. The Summer Triangle formed by the brightest stars of Lyra, Cygnus, and Aquila will be visible low in the east-northeast at that time. The Waning Gibbous Moon will be visible after 11 PM. When the Moon rises it will be almost directly below the lowest point of the Summer Triangle, the star Altair of Aquila. The Moon will be among the stars of Capricornus all tonight. See the third star chart below for this view.
In the morning pre-dawn sky look for Mars near the Pleiades star cluster low in the east. They are close enough together that should appear in the same field of view of your binoculars. You will probably need to use the binoculars for Mars in the dawn twilight. The bright star left (north) of the Pleiades at the same altitude is Capella. The next interesting astronomy event after the summer solstice will be when the very thin sliver of the Waning Crescent Moon passes between the Pleiades and Mars on June 28th. The Moon and the Pleiades will be within the same field of view of your binoculars—a very pretty sight! The first star chart belowshows the Moon's motion at the end of the month. The following morning, an even thinner Moon will be to the left of the eye of Taurus, the orange-red star Aldebaran. The end of the month will also see the return of Mercury to the evening sky—look for it low in the west shortly after sunset. Although it will be the brightest starlike object in the evening sky, the dusk twilight will probably make it difficult to see without binoculars.
Want to see more of the stars at night and save energy? Shield your lights so that the light only goes down toward the ground. See www.darksky.org for how.
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com