Bakersfield Night Sky – July 7, 2018
By Nick Strobel
July 2018 is the month for Mars. Those of you who stay up past 11 p.m. will see a bright orange-red “star” rising that is even brighter than the king planet, Jupiter, you see in the south at sunset (see the star chart below). That star is actually Mars on its way to its closest approach to Earth since 2003. Mars has an elliptical orbit that is almost nine times more eccentric than our orbit around the sun. Usually, we pass by Mars when Mars is at a farther point in its orbit. Not this time. We’ll pass by Mars when Mars is near its perihelion point (when it is closest to the sun). Also, yesterday, July 6, was aphelion day for Earth, when we’re farthest from the sun (at a distance of 94.51 million miles). Put those two things together and it means a close approach this time around. Mars will be closest to Earth at the end of July.
If the closest approach is July 30/31, then why did we launch the Mars InSight mission during the first week of May? Unlike Hollywood, NASA (and other space agencies) work in the realm of reality where solar system travel distances are measured in many millions of miles, where rockets have a finite fuel supply and where the planets are always moving with respect to each other. Our spacecraft must be sent in orbit around the sun and coast most of the way, letting the sun’s and planets’ gravity guide the craft to its destination. We have to time things just right, so this coasting path makes the spacecraft and Mars arrive at the same point in Mars’ orbit at the same time.
I hope the global dust storm now raging on Mars is cleared up by the time InSight reaches Mars in November. The dust storm has been going on for over a month now (reaching “global scale” a few weeks ago). The dust storm has blocked so much of the sunlight that the long-running Opportunity rover has been in sleep mode to conserve power for just the heaters, so the electronics don’t freeze (and “kill” the rover) and so its clock can continue running. The clock needs to keep running, so Opportunity knows when to wake itself up every few days and check the power levels. If the power levels are too low, it goes back to sleep.
Unlike the Curiosity rover, Opportunity is solar-powered and is now running on just its batteries. If the storm deposits too much dust on its panels, then Opportunity might not be able to wake up again. The original 90-day estimate for the Opportunity’s lifetime was based on estimates of how quickly the martian dust would cover its solar panels. Fortunately, it has had some occasional dust devils blow its panels clean, so it has been able to continue investigating its part of Mars since 2004.
Curiosity is nuclear-powered, so it’s less affected by the reduction in sunlight. We don’t have to worry about global dust storms here on Earth because of several factors that include: a thicker (denser) atmosphere, stronger gravity, vegetation covering the land that binds the soil with its roots and blocks wind sweeping across the surface, and rain that washes dust out of the air.
Notice that I said yesterday was aphelion day—right in the middle of our summer. Our hot temperatures during the summer are caused by the more direct angle of sunlight hitting our part of the earth (the sun gets up higher in our sky) and the longer daylight hours. The more direct angle of sunlight gives the sun greater cooking power for us and the longer daylight means more cooking time. Both things result in us baking in Bakersfield’s summers.
Tuesday evening, July 9, after sunset you’ll see Venus less than 1 degree (thumb width at arm’s length) from the brightest star of Leo, Regulus. The following morning (July 10), early risers will see a thin sliver of a waning crescent moon right next to the brightest star of Taurus, Aldebaran. Those in parts of Canada will see the moon cover up http://stars.astro.illinois.edu/sow/aldebaran.html">Aldebaran. The night of July 10 will see Jupiter stop its retrograde motion westward and start its usual eastward drift among the stars. In the early evening of July 15, shortly after sunset, a thin sliver of a waxing crescent moon will be less than 2 degrees from bright Venus—a beautiful sight through binoculars!
On Saturday, June 21, the Kern Astronomical Society will be back at the Park at Riverwalk for a free public star party. Put it on your calendar now and come by for a look through the telescopes!
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website www.astronomynotes.com