Bakersfield Night Sky - May 18, 2013

photo of Planetarium

By Nick Strobel

The academic year at Bakersfield College is now finished and the William M Thomas Planetarium is closed for the summer break. I just finished the revisions for the new edition of my astronomy textbook, Astronomy Notes, early this morning (3:30 AM) as I write this, so hopefully my brain is still sharp enough to write coherently in this column. The content of the hardcopy textbook is also freely available online and the website is continually updated. However, creating a hardcopy book version forces one to take a more careful look at ALL of the materials to make sure the presentation is clear, accurate, and it all "hangs together". That more thorough review of the hardcopy then translates to more revisions of the website. Take a look at my "Astronomy Notes" website and let me know what you think, even for those parts that need fixing.

By the time this appears in print, the National Student Solar Spectrograph Competition in Bozeman, MT (that's Montana) will have finished. I talked about the competition in my previous column. Whether or not any of the three teams of student scientists and engineers from Bakersfield College win the competition is besides the point. My hope for the BC students is that they will make connections with other student scientists and engineers from around the country and learn their own strengths as well as what they need to improve upon as they compare their abilities with other sharp students from other colleges and universities.

After the competition I head to University of Dayton for a couple of short courses on energy sustainability and climate change. There is a section about what affects a planet's or a region's climate and what can change a planet's climate in the Astronomy Notes textbook and website. Studying other planets atmospheres and climates helps us better understand how our own planet's climate system works and what can change a planet's climate including solar brightening, changes in reflectivity (clouds, ice, etc.), changes in the amount of greenhouse gases (water vapor, carbon dioxide, methane, etc.), and changes in the tilt of the axis and shape of the orbit. Mars and Earth have undergone several swings in climate from long ice ages to briefer warm interglacials that were triggered by changes in the tilt of the axis and shape of their orbits. The length of time for these sorts of climate swings are measured in many tens of thousands of years. The fellow who first quantified the changes and developed the mathematical theory behind the axis and orbit variations for the Earth was a Russian mathematician named Milutin Milankovitch about a century ago, so these cycles are called "Milankovitch cycles" in his honor. The theory behind the axis and orbit variations has, of course, been refined and improved since then. The axis tilt and orbit variations cannot by themselves, explain the magnitude and quickness of the temperature changes between the ice ages and the interglacials. One has to include the effects of reflectivity changes and greenhouse gas abundance changes---the positive and negative feedback effects of them---to explain the magnitude and quickness of the temperature changes fully. In the exoplanet realm of astronomy, the climate research enables us to determine which exoplanets are in a star's habitable zone. On shorter timescales of decades, other things such as volcanoes, solar activity, and humans play a greater role.

This evening is the free monthly public star party with the Kern Astronomical Society that takes place from 8 PM to 10 PM or so, depending on foot traffic, at Russo's Books in The MarketPlace. Telescopes will be set up on the paved pedestrian area just west of Russo's and just east of the outdoor dining area. The Waxing Gibbous Moon (one day past First Quarter) and Saturn along with some bright clusters are on tap for tonight. Being just one day past First Quarter, the craters will stand out particularly well, especially right along the boundary between the day and night where the shadows make the rugged terrain pop out. At the boundary between day and night for the waxing phases, the Sun is rising above the horizon for those locations, beginning its two-week trek across the lunar sky. In our sky the Waxing Gibbous Moon is just past the due South position when the free public star party begins. The Moon will be below the Sickle part of Leo with bright Regulus at the end of the backward question mark.

Saturn will be rising in the East about a quarter of the way up in the sky at the start of the star party. The rings will be opened up by quite a bit, being their most open since 2006, so they should be quite impressive at the monthly public star parties throughout this summer and fall. Saturn and the two bright stars in the east, Spica and Arcturus will make an easily noticeable right triangle in the southeastern sky. The triangle is elongated toward the left (north) and tipped up by about 45 degrees in the early evening. Saturn is the lowest point of the triangle, Spica will be in the upper right corner and Arcturus is at the elongated point farthest north. From Saturn or Spica to Arcturus, the triangle is over a hand width (fingers spread out) held out at arm's length across. Saturn and Spica are about a fist width apart from each other. The Hercules Cluster (M13), a nice jewel of a globular cluster about 25,000 light years away, will be another thing to see through the telescopes. It is at the right edge of the Keystone part of Hercules, rising in the northeast at 8 PM.

By 10 PM, when the public star party ends, the Moon and Leo will be in the southwest about halfway up in the sky. Spica will be almost due South halfway up in the sky and Saturn will be due left of Spica at the same height as Spica as the elongated triangle has rotated with the sky, so Arcturus will also be almost due South about three-quarters of the way up in the sky (right above Spica). Hercules will be about halfway up in the eastern sky. A star chart to use for the public star party is the second chart below.

A bit earlier in the evening just after sunset, look low in the west to spot Jupiter. Closer to the horizon you might be able to spot Venus. Mercury is still too close to the Sun on our sky to spot it but at the end of May, Jupiter will make an interesting dance with Venus and Mercury as shown in the first star chart below. The first chart below shows the sky 30 minutes after sunset. Next Friday May 24th, Mercury and Venus will be closest together and all three planets will fit within the field of view of your binoculars low in the west about half an hour after sunset. All three are most closely packed on Sunday, May 26th. On May 28th, Venus and Jupiter are closest together and all three will fit within the same field of view of your binoculars. By May 31st the dance is over as Mercury, Venus, and Jupiter (in that order) form a diagonal line low in the west shortly after sunset and Mercury and Jupiter will be too far apart to fit within your binoculars field of view.

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. Visit the Dark Sky International website for more info.