Bakersfield Night Sky — May 19, 2024
We had a record number of students walking across the stage at the BC Commencement two Fridays ago with a spectacular fireworks display at the end. It seemed like the sun joined the celebration by sending out several coronal mass ejections (CMEs) in the direction toward Earth from a gigantic sunspot region labeled “3664”. Those CMEs reached Earth that Friday night and lit up the sky with aurorae visible in much of the United States. There were even pictures posted online that were taken from just outside of Bakersfield!
The sun is constantly spewing out a stream of charged particles called the “solar wind”. These solar wind particles are deflected around a planet if a planet has a magnetic field; otherwise, the particles will directly hit the planet’s atmosphere and erode away the atmosphere. Fortunately, Earth has a significant global magnetic field protecting its atmosphere. Mars doesn’t have that protective shield, so most of its atmosphere was blasted away over the past few billion years.
Fluctuations in the solar wind can give energy to other charged particles trapped in the radiation belts surrounding Earth. Particles with enough energy can leave the belts and spiral down to the atmosphere to collide with molecules and atoms in the very rarefied top atmosphere layer called the thermosphere. These collisions cause the oxygen and nitrogen molecules to glow.
The thermosphere layer is many tens of miles above the surface. The magenta colors of aurorae are produced by nitrogen molecules at the lower end of the aurorae (down to 60 miles above the surface). Between 60 and 120 miles above the surface, excited oxygen atoms produce the green colors and ionized nitrogen atoms produce the blue colors. Greater than 120 miles above the surface, oxygen atoms produce the deep red colors. In the northern hemisphere, the aurorae are called aurora borealis or “the northern lights” and in the southern hemisphere, they are called aurora australis or “the southern lights.”
Usually, the auroral oval centered on the magnetic poles is small and much farther north of northern Canada and Alaska. A large outburst from the sun like we had on May 10 can increase the diameter and thickness of the auroral oval, so people in the lower 48 states can see aurorae. Those in the northern states will see more of the colors while those in southern California, Arizona, etc. will usually see just the red colors from the highest altitude aurorae. Most aurorae will appear much paler than the pictures of them you see in books or posted online because our eyes have an exposure time of about a tenth of a second but a camera can accumulate a lot more light with a longer exposure. My iPhone’s camera, for example, can take up to a ten-second exposure on the night photo setting. The sun is nearing the peak of its cycle of magnetic activity, so we may see some more aurorae in California this year! Go to Government Space Weather Predictor website to see the latest updates on the sun’s activity and get aurora predictions from NOAA’s Space Weather Prediction Center.
We’re finished with planets in the evening sky for a while. Jupiter is now behind the sun. It’ll reappear in the early morning pre-dawn sky in mid-June but it won’t be until early July before it’s easily visible. The star chart shows the evening sky at 9:30 p.m. looking southeast. Leo with its distinctive sickle (backward question mark) and the bright star Regulus at the end is high overhead in the south-southwest at right. Due south is Virgo. A waxing gibbous moon will be near Virgo’s bright star, Spica. The moon will be a full phase on the night of May 22/23 but will be between the stars of Libra and Scorpius by then. Near the end of the month, on the night of May 29/30, the moon will be at third (last) quarter phase and it will not be above the horizon until well after 1 a.m.
In the southeast, kite-shaped Bootes with the very bright star Arcturus at the tail end will be rising. The backwards “C” of Corona Borealis is below Bootes and the bow-tie pattern of the main part of Hercules will be just above the eastern horizon.
The inset of the star chart shows the view in the early pre-dawn morning about an hour before sunrise. Mars and Saturn will be about three fists at arm’s length apart from each other with Saturn on the right and Mars on the left. They will be almost the same brightness with Mars the slightly brighter of the pair. On the last day of May, a waning crescent moon will be next to Saturn, just slightly left of Saturn. That should be a nice view in your binoculars!
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Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com
