Bakersfield College

October 16, 2010

Bakersfield Night Sky – October 16, 2010
By Nick Strobel

Tonight is the last public star party for this season held by Bakersfield's astronomy club, the Kern Astronomical Society, at Barnes and Noble from sunset to 10:00 or 10:30 depending on foot traffic. Come take a look through one of the telescopes set up for you! Of course, the event will depend on the weather. As the rains last week reminded us, we're in the fall season with its occasional cloudy skies. What sorts of things will we be able to see tonight (weather permitting)?

Venus is now too close to the Sun from our viewpoint on Earth. It will set just 18 minutes after the Sun does. We will have to wait until early November to see it in the pre-dawn sky. Mars is also probably too close to the Sun to see without binoculars. It will set about an hour after the Sun does. You can try to find it low in the southwest in the constellation Libra. Another newsworthy planet is in the constellation Libra too but this one is an exoplanet—orbiting a dim star called Gliese 581 just 20 light years away off the top of the scales that make up Libra. I've included its location in the inset of the first chart below. Gliese 581 has six planets orbiting it all in nearly circular orbits like the orbit shapes of the planets in our solar system. All of them have very original, clever names: "a", "b", "c", "d", "e", "f", and "g". (Now you can see why astronomers did not go into creative writing as a profession.) Well, Gliese 581g is the one that has been in the news because it orbits at just the right distance from the star to be within its habitable zone. The habitable zone is where the surface temperatures on a planet would be "not too hot and not too cold but just right" for liquid water to exist on the surface. Because Gliese 581g is only a third of the Sun's mass, it puts out just 1.3% of the Sun's energy. Therefore, Gliese 581g has to orbit at less than half (38% to be more precise) of what Mercury orbits our Sun to be warm enough for liquid water to be on its surface. If there's liquid water, there could be life. Well, is there liquid water? We don't know yet. Sigh!

Gliese 581g has between 3.1 and 4.3 Earth masses, so it should have a reasonably thick atmosphere. If the atmosphere doesn't have too much of a greenhouse effect (like Venus), then it should be comfortable. We need to take the spectrum of the planet's atmosphere to find its composition. The spectrum is the light from the planet spread out into its individual colors. This will be done in the infrared, so it will be an infrared rainbow. That rainbow will have a pattern of dark lines in it that will tell us its composition. Unfortunately, we will probably have to wait until NASA's Terrestrial Planet Finder mission comes on line before we have the capability to take Gliese 581g's spectrum with sufficient detail to see the dark lines.

Now back to the star party: the Moon, Jupiter, Uranus, and Comet Hartley 2 will be solar system objects to check out in the telescopes. A Waxing Gibbous Moon will be reflecting a lot of sunlight tonight. It is on the left side of Capricornus (see the attached star chart). You will see well-defined craters near the day-night boundary because the Sun will appear at a low altitude in the lunar sky near the day-night boundary so the shadows will be long. Further left (more east) will be Jupiter and Uranus. Both of them are in Pisces but you'll have an easier time locating them with respect to the brighter Great Square of Pegasus (see the attached star chart). Through the telescopes, you'll be able to see the bands of Jupiter and some of its larger moons, including Europa that very likely has a deep ocean of liquid water below its ice surface. Uranus will look like a small greenish dot through the telescopes. Between the Moon and Jupiter but closer to the horizon is the bright star Fomalhaut, another star known to have at least one planet orbiting it. (Sorry, you cannot see the planet with the KAS telescopes—that requires the Hubble Space Telescope!)

Further to the left in the northeast near bright star Capella is Comet Hartley 2. I have a finder chart below for the next eight days. Comet Hartley 2 will approach within just 11 million miles of the Earth on October 20th. Okay, now that's close astronomically speaking—Comet Hyakutake was slightly closer in 1996 and it was quite spectacular! While we don't expect Comet Hartley 2 to be as spectacular as Comet Hyakutake, it may be visible without a telescope tonight under dark skies and easily visible in the KAS telescopes. Tonight will probably be better than October 20th to view the comet because the almost full Moon will be much closer to the comet on the 20th. Two weeks later, on November 4th, NASA's Deep Impact spacecraft will fly to within 600 miles of the comet nucleus to give us a close-up look. Deep Impact was the one that smashed a projectile into a Comet Tempel 1's nucleus back in July 2005. The spacecraft's mission has been renamed "EPOXI" so use that name when doing a search on the NASA website.

The night after Comet Hartley 2's closest approach (i.e., October 21st), the William M Thomas Planetarium will be showing "Dawn of the Space Age". This is a popular show. Last month's show for the general public was sold out a few days before show time, so if you want to see the October show, get your tickets as soon as you can from the BC Ticket Office. Dawn of the Space Age begins with the launch of Sputnik in 1957 and covers the history of the race to the Moon, exploration of the Moon and the planets, the Space Shuttle, the International Space Station, and the first steps to space tourism right in our back yard—Spaceship One from Mojave. The visuals are excellent. One of the Russian cosmonauts interviewed at the end of the show says that the show so accurately portrayed what space flight is like, he felt like he was back in space.

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