Bakersfield Night Sky – May 19, 2012
By Nick Strobel
The William M Thomas is now closed for the summer break but there are a couple of daytime astronomy events in the early summer that you should check out. The first is the solar eclipse that happens tomorrow! The Moon will begin to cover the Sun at 5:22 PM and the maximum eclipse for Bakersfield will happen at 6:36 PM when the Sun is 81% covered up. The Moon will be all off the Sun by 7:41 PM (see the first chart below). North of Yuba City, people will be able to see the annular solar eclipse in which the perfectly lined up Moon is too far away from the Earth in its elliptical orbit around the Earth to totally cover up the Sun. In such an eclipse, there is an annulus (ring) of Sun around the dark Moon as shown in the first chart below. As of the time of writing this, it looks like all of the solar observers from the Kern Astronomical Society will be heading north to see the annular solar eclipse, so there will not be an "eclipse party" in Bakersfield. Only special solar filters are safe enough for directly looking at the Sun—dark sunglasses, even several put together, are NOT safe for your eyes!
I have been practicing photographing the Sun with a solar filter on my telephoto lens and I've been able to image the large sunspot group that was associated with some major solar flares about two weeks ago by the time this column appears in print (see pictures above—select the images to bring up a full-size version). The largest sunspot was roughly the size of Saturn without the rings. Sunspots are cooler regions of the Sun, "only" about 4500 K instead of 6000 K like the rest of the brighter surface. The strong magnetic fields in the sunspot area inhibit the flow of energy through the surface at the place of the sunspots. Dark spots require magnetic fields at least 1500 times stronger than Earth's surface magnetic field. Less energy flowing through the sunspot area means cooler temperatures and that means the area is less bright or darker in comparison to the rest of the Sun. Solar flares happen when the magnetic field above a sunspot gets all tangled up and snaps, releasing a flood of charged particles moving at up to 80% the speed of light. Most flares will also include violent releases of bubbles of gas called coronal mass ejections (CMEs for short) in which up to a billion tons of matter is accelerated up to several million miles per hour (no CMEs occurred with the solar flares of two weeks ago). Those particles will take two to three days to reach us. Our atmosphere and magnetic field shield us from the burst of particles in a flare or bubble of gas in a CME, but they can fry the electronics of satellites and powerful flares can cause voltage surges in power and telephone lines that could lead to power outages.
With so much of modern society depending on technologies that are sensitive to solar particle bursts, we need to understand how the magnetic field of the Sun works so that we can prevent damage to the technologies we rely on. There is still a lot more we need to learn about the Sun before we can make long-term "space weather" forecasts. More observations and time for the creative powers of humans to figure out what's going on are needed. We do know enough about the Sun to know when a CME is heading our way in enough time to put satellites in a safe mode, lessening the likelihood of losing a multi-million dollar piece of hardware. We also know enough about the Sun that we can say without a doubt that there will be no solar flare or CME powerful enough to wipe out the Earth this year or any year in the future.
Perhaps today's Sun will have some other sunspots appearing. The number of sunspots should continue to increase throughout all of this year and peak near the end of 2013. However, this sunspot maximum is expected to be weak and there are even indications from three different lines of research that the normal 11-year sunspot cycle may be shutting down for a while.
All of the techniques and equipment you use for viewing the eclipse or sunspots will be essential for observing the once-in-a-lifetime event of Venus crossing in front of the Sun on June 5th. On that date Venus will cross the face of the Sun from 3:06 PM to 9:45 PM as seen from Bakersfield—see the first chart below. Of course, the Sun will set before 9:45 PM so we'll be able to see just the first half of the total transit. Do try to observe this event since it won't be until 2117 that Venus's orbit is exactly lined up with the Earth-Sun line again with Venus is right between us and the Sun. Yes, that's 105 years! What the Venus transit loses in frequency it makes up for in visibility locations—all of North America, all of Central America and northwestern South America will be able to view the transit in our hemisphere during our afternoon of June 5th. Most of Europe, eastern half of Africa, all of Asia and Australia will be able to see it during their morning of June 6th (remember that they are many timezones ahead of us). I fully expect that there will be a Venus Transit observing party in Bakersfield. Details will be posted on the Kern Astronomical Society's website at www.kernastro.org .
In tonight's sky Venus is still the bright star in the western sky in the evening. At the beginning of the month it set around 10:30 PM, but now it is making its rapid fall back toward the Sun heading toward the June 5th transit. It will set at about 9:30 PM tonight and at the end of the month it will set shortly after sunset. Mars is high up in the south next to Leo as the Sun sets. Saturn is in the southeast at sunset on the left side of Virgo near the bright star Spica. The second chart below shows the view at 9 PM. Saturn and Spica will be like a pair of bright eyes in the sky with Saturn on the upper left. In the patch of sky between the Virgo and Leo is the closest major cluster of galaxies to us, the Virgo Cluster, made of a few thousand galaxies, some much larger than our home galaxy, the Milky Way. The Milky Way is part of a group of galaxies with too few galaxies to be called a cluster, so it is given the very creative name "Local Group".
Further north (left) and a bit higher up you will see the very bright star, Arcturus at the end of the kite-shaped Bootes—see the third chart below. Nearer the horizon below Bootes at 9 PM is the bowtie or butterfly shape of Hercules. On one side of the keystone part of the bowtie is the Hercules Cluster, a cluster of several hundred thousand stars nearly as old as the Milky Way, all gravitationally bound together as they orbit the galactic center. Those of you with very good eyes under a very dark sky can just pick it out. Binoculars and, of course, a telescope provide a much better view. Just beginning to come up at 9 PM is the bright star Vega of Lyra in the northeast.
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