Bakersfield Night Sky - June 2, 2019

Bakersfield Night Sky - June 2, 2019 By Nick Strobel

May 2019 was certainly a cooler and cloudier May than we're used to in Bakersfield. That put a crimp in our night sky observing. Skies should be clearer in June and on Saturday, June 8, the Kern Astronomical Society will have their telescopes out at Panorama Park near Bakersfield College for the public to view the heavens. Telescopes will be set out just west of Greenlawn Mortuary & Cemetery near where Linden intersects Panorama Drive. Observing will begin with the waxing crescent moon shortly before sunset and then go to other objects when the sky gets darker. The free public star party will end at around 10 PM, depending on foot traffic. See the KAS website for maps to the star parties this summer.

One object to definitely check out is the king planet, Jupiter. Jupiter will be at opposition on June 10, when it will appear 180 degrees opposite the sun and be up highest in the south at around 1 AM For the star party Jupiter will be the bright point low in the southeast between Ophiuchus and Scorpius (see the star chart below). Jupiter will be better placed for evening viewing when KAS returns to the Park at Riverwalk for the free public star party on July 13.

Jupiter's reflective clouds, large size and proximity to us make it appear three times brighter than Sirius, the brightest true star in the night sky. Because Earth is overtaking Jupiter in our faster, inner orbit, Jupiter appears to be retrograding, i.e., moving backward among the stars compared to its usual west-to-east motion. If our air is clear and steady enough, you'll be able to see the clouds bands on Jupiter but you won't be able to see Jupiter's largest storm, the Great Red Spot because it will have rotated out of view by the time of the star party. The Great Red Spot will come into view at around midnight on the night of the star party. It will be at the far western edge of Jupiter for the July 13 star party.

The Great Red Spot is a high-pressure hurricane system that has been raging for centuries. Its clouds are higher than most of the other clouds but its temperature is also higher than the other clouds, so it is a site where heat is being brought up from deep in Jupiter's much warmer interior. The Great Red Spot has been shrinking over the past several decades. When Voyager flew by Jupiter in the late 1970s, you could fit all of the inner four planets comfortably inside the storm system. Now you can only fit Earth inside the Great Red Spot. The shrinking has been more noticeable along the horizontal axis, so its shape has gone from an elliptical shape to a more circular shape.

The Great Red Spot's color has also been deepening over the past several years, becoming more intensely orange-red than before. That may be because the compounds that give the storm its color are being carried higher up than before and thereby being exposed to more UV radiation from the sun than before. Surprisingly, the winds inside the system have been slowing down instead of speeding up as the system contracts through the conservation of angular momentum. The conservation of angular momentum is why when an ice skater pulls in her arms and legs closer to her centerline as she spins, her spin rate increases to keep the combination of spin speed times size the same value. Objects will spin faster as they shrink.

That's not happening with the Great Red Spot. Instead of spinning faster, the storm is getting taller. We're still trying to figure out why. A new development is that parts of the Great Red Spot are being peeled off by the South Equatorial Belt, a band of white clouds south of the Great Red Spot. The bands of Jupiter are caused by the huge Coriolis effect arising from Jupiter's very rapid rotation (less than 10 hours to make one complete rotation) that deflects the jet streams so they move parallel to the equator. Could the shrinking and peeling off of the Great Red Spot spell the end of the storm system? We're not sure, so we continue to monitor the developments.

The four large Galilean satellites of Jupiter will be visible on the night of the star party. The largest one, Ganymede, is even bigger than the planet Mercury. Ganymede will be on the east side of Jupiter while the other three Galilean satellites, Io, Europa, and Callisto will be strung out on the other side in that order.

On the night of the public star party, the moon will be to the left of Regulus, the bright star at the bottom end of the sickle (backward question mark) part of Leo. The following night will be first quarter phase and the moon will pass by Jupiter between the nights of June 15 & 16 in the waxing gibbous phase. It will be at full phase on June 17.

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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