Bakersfield College

August 4, 2012

Bakersfield Night Sky – August 4, 2012
By Nick Strobel

Tomorrow evening (August 5th) at 10:31 PM we will know if the largest, most advanced spacecraft sent to Mars' surface, the Mars Science Laboratory, aka "Curiosity" arrived safely. It will use a sky crane in the final descent to put the rover on the surface. It is much too large to use the airbags technique that was used with previous rovers. Curiosity has already been observing space conditions on its transit to Mars, investigating the amount of radiation and other environmental hazards a manned mission to Mars would have to protect itself from during the minimum seven-month voyage to Mars. While on Mars, Curiosity will determine if Mars ever had an environment able to support any kind of life by investigating the rocks and soil in Gale Crater. The mission length will be at least a full martian year (687 Earth days) and operate all year long, not just during the warmer and sunnier spring and summer seasons like the other rovers. The other rovers were solar-powered but Curiosity will use the same sort of power supply used on the Viking, Pioneer, Voyager, Cassini missions, a sort of atomic power called "Radioisotope Thermoelectric Generator" (RTG for short).

NASA will broadcast all of the landing events and news briefings on the following several days on NASA TV.

The Mars Science Laboratory will be the last spacecraft NASA will be able to send to Mars' surface for a LONG time. Because of budget cuts over the past several years, no other Mars surface mission is in the pipeline. It takes a decade or more to develop a mission because so much new technology has to be invented and then tested repeatedly (new technology that, by the way, finds its way into other areas of our lives—"spinoffs"). Mars exploration is not the only place in the NASA budget that has taken a hit. The pipeline for any new Earth-observing science missions used to study how the Earth works as a system and the changing natural resources has been pretty much cut completely off, so once the current crop of satellites has been launched, that will be it for at least a decade or more. Although NASA funding amounts to only half a percent (so for every two dollars spent by the government, just one penny goes to NASA), it is among the first things to be cut during tight budget times. Most people also don't realize that every dollar spent developing the new technology for space exploration leads to a boost in the economy by more than seven dollars from the spinoffs, not to mention the incalculable but certainly huge long-term dividend of inspiring students to go into one of the STEM (Science, Technology, Engineering, and Mathematics) fields that will be absolutely critical and necessary for the economic future of our nation.

The other major astronomy event of the month is the Perseids meteor shower. The meteor shower is expected to peak the night of August 11th/12th after midnight. The Perseid meteor shower happens when the Earth runs into the dust trail left behind by the Comet Swift-Tuttle. The bits of comet debris hit our atmosphere at 38 miles/second (61 kilometers/second) and burn up above the stratosphere several tens of miles above the ground. Because the Earth is plowing into Comet Swift-Tuttle's dust trail, the meteors appear to streak out of a particular direction in space in the constellation Perseus. That point in Perseus will rise around 9:45 PM but more meteors should be seen after midnight because the California part of the Earth is facing the direction of the Earth's orbital motion around the Sun. Comet bits moving at any speed can hit our atmosphere. Before midnight, the California part of the Earth is facing away from the direction of orbital motion, so only the fastest moving comet bits can catch up to the Earth and hit the atmosphere. The same sort of effect explains why your car's front windshield will get plastered with insects while the rear window stays clean.

The best viewing instrument for observing meteor showers are just your eyes—no binoculars or telescope because the meteor streaks cover a far wider stretch of sky that can be viewed with even low-power binoculars. You'll probably find you see more meteors out of the corner of your eye than right where you're looking. That's because your eyes have greater light sensitivity around the periphery of your vision than in the center. This year we'll have just a Waning Crescent Moon to contend with on the night of August 11th/12th and it will rise at about 2 AM. Above the Moon will be very bright Jupiter and to the right of Jupiter, the orange-red eye of Taurus, the star Aldebaran—see the second chart below. Can't do the night of August 11th/12th? No worries! The dust trail of Comet Swift-Tuttle is pretty broad so the number of meteors/hour will increase for several nights before the 11th and will gradually fall off over the next several nights after the 12th.

In tonight's evening sky you will see Mars and Saturn and the bright star, Spica, all shining with about the same brightness in the western sky. As shown in the first chart below, they'll form a small triangle on the sky with Saturn at the top and Mars at the bottom right point. The triangle is probably too large to fit within the field of view of your binoculars but watch that triangle shrink over the following nights as Mars threads the gap between Saturn and Spica. By the night of August 6th, the triangle will be small enough to fit within your binoculars and a couple of nights after the Perseid meteor shower peak (i.e., August 13th), all three will be lined up. By the night of August 21st, the trio will make a triangle (with Mars now at the left point) that will probably just barely be too large to fit within your binoculars but a thin Waxing Crescent Moon just left of Spica will make a gorgeous arrangement of nearby and distant objects to look at with your binoculars. In order of distance they will be the Moon at almost 230,000 miles away, Mars at almost 163 million miles away, Saturn at over 950 million miles away, and Spica at 250 light years away. If you want to find the number of miles for Spica, then multiply its distance by 6 trillion.

I have used a couple of terms to describe the crescent Moon: "waxing" and "waning". "Waxing" means the Moon's light is getting larger with time due to fact that an increasing amount of the Moon's sunlit side faces the Earth as the Moon orbits the Earth. "Waning" means the Moon's light is getting smaller with time as less and less of the Moon's sunlit part faces the Earth (or an increasing amount of the Moon's night side faces us). To remember which is waxing and which is waning, I think of beeswax and Dwayne. The lowercase letter "b" has the rounded part facing to the right just like the rounded part of the waxing Moon faces to the right, so "beeswax". Similarly, the lowercase "d" has the rounded part facing to the left just like the rounded part of the waning Moon faces to the left, so "d-wane" or "Dwayne" for the usual spelling of the name.

The inner planets Mercury and Venus will make their best appearances in the pre-dawn sky just one day apart from each other. Venus will rise at around 3 AM all during August but on the morning of August 15th, it will be at its greatest angular distance from the Sun on our sky, rising about 3.5 hours before the Sun does. Speedy Mercury becomes visible in the pre-dawn sky in the second week of the month and zips on up for its greatest angular distance from the Sun on the morning of August 16th. It will rise an hour and a half before the Sun does on that morning. It will hover there for another couple of days and then plunge back toward the Sun in the last week of August. See the second chart below for the pre-dawn sky.

On the morning of August 13th, the very thin Waning Crescent Moon will be just above Venus almost touching it. If you keep track of where the Moon is on that day, you'll see the Moon cover up Venus (an "occultation") later in the day. The occultation will happen between 1:35 PM and 2:45 PM. Yes, that's during daylight but a good pair of binoculars and certainly a telescope will enable you to see it. The thin crescent Moon will be about four or five fist-widths at arm's length to the right of and down from the Sun (in the southwest). You'll probably be able to spot the bright point of Venus easier than the thin crescent Moon on the blue sky but be sure to locate it before the 1:35 PM occultation time.

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.
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Nick Strobel
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com

Kern Community College District