Bakersfield Night Sky - August 1, 2015

Bakersfield Night Sky - August 1, 2015
By Nick Strobel

August has arrived, so many teachers are now fully back into "school mode" taking care of getting things set up for the next school year. Bakersfield College will be welcoming thousands of new students of all ages to start their higher education at a place that according to a recent national research study will give them on average a 17% boost in annual earnings. Many hundreds of them have received an extra special head start on their college studies this summer through the BC Summer Bridge headed by faculty member Kimberly Bligh to help them make the transition from high school to college. 

Also coming in a few weeks will be the fall schedule of evening shows for the general public at the William M Thomas Planetarium. Some K12 teachers have already sent in their reservations for the morning field trip shows but I'll be getting plenty more field trip requests over the next several weeks. If you have a child or grandchild who wants to come to the planetarium or know someone who does, see if their teacher knows about reserving a field trip online through the planetarium's website. There's a large "Field Trips" button on the left side that will get them to the reservation page.

Astronomy discoveries continued during the summer break. Two recent major discoveries are the surprising amount of geologic activity on Pluto and the recent batch of new exoplanets from the Kepler spacecraft. As happens when we explore a new place, we have found several unexpected things on Pluto that are a bit baffling. Reality is so much cooler than what we can program in our virtual worlds because nature is far more creative than we are. On Pluto we have found flowing ices, mountain ranges, exotic surface chemistry, and an atmosphere with a haze layer that extends out farther than we thought possible. You can't make this stuff up because we didn't think Pluto could be this geologically interesting.

It is a basic physical principle that smaller objects will cool off quicker than bigger objects because they have proportionately more surface area to volume than a bigger object. For example, if I were to throw a bucket of boiling water on you from several feet away, it'd cause severe burning of your skin. But if I sprayed that same boiling water through an atomizer nozzle on you from the same distance, the fine droplets would have cooled off enough to not burn you. Pluto is so small, just 1474 miles in diameter, that it should have cooled off since it formed 4.56 billion years ago and be essentially geologically dead. Therefore, we were expecting to work on determining Pluto's past geologic history, not to be confronted with current activity. The New Horizons team says that the heat driving the geologic activity must be radioactivity but the question remains of how there can be that much radioactivity left in such a small world after 4.56 billion years. 

The nitrogen ice in Pluto's Tombaugh Regio (the feature that looks like a valentine heart to our human eyes) appears to be flowing around mountain ranges and into depressions such as impact craters just like glaciers do on the Earth and seem to have done on Mars. Whoa! There are now three places in the solar system where glacial flows are seen but who would have guessed that Pluto would be that third place? 

It appears that Pluto's atmosphere is rapidly decreasing. Since its closest approach to the Sun in 1989, Pluto's nitrogen-methane atmosphere has actually increased in amount, possibly a seasonal effect as the nitrogen ice at its north pole were finally exposed to the Sun so that they could sublimate. Eventually, the atmosphere is expected to freeze out and disappear as Pluto moves away from the Sun. Using data from a radio pulse beamed from Earth timed to reach Pluto just as Pluto went between the Earth and New Horizons (another ridiculously accurate engineering feat from NASA), the New Horizons team found that the surface pressure was about half of what earlier ground-based measurements found. The ground-based measurements do NOT appear to be in error, so the drop in Pluto air pressure to half of what it was just a couple of years ago appears to be real.

At the end of June, the SOFIA airborne observatory, an infrared telescope installed on a 747 aircraft, flew into the perfect position to see Pluto pass in front of a distant star. That enabled us to get data that will help us understand the density and structure of Pluto's atmosphere. Combining this data with what New Horizons saw up close just a few weeks later will greatly enhance future analysis of Pluto's changing atmosphere as SOFIA observes it in the years to come. Perhaps the New Horizons spacecraft arrived at Pluto to see the first stages of the atmosphere freezing out, in which case, they arrived just in the nick of time! More answers will come as the rest of the data from the flyby encounter are beamed back to Earth over the coming months. As of the news conference on July 24th, we had received just 4 to 5% of the data. See the New Horizons website for updates (and some incredibly beautiful shots of the Pluto atmosphere).

The day before the Pluto news conference was a news conference about the latest batch of exoplanet discoveries from the Kepler mission that included the most Earth-like system yet: Kepler-452 and its planet Kepler-452b. Kepler-452b is the first exoplanet that is about the size of the Earth discovered in the habitable zone of a star like our Sun. The other near-Earths in habitable zones confirmed so far are orbiting stars significantly dimmer than the Sun. Now life on a planet orbiting in the habitable zone of a dimmer star doesn't care how the star compares to our Sun---as long as the temperature is nice, life will do just fine. However, we here on Earth are especially interested in finding one that matches our situation.

When I first heard about Kepler-452b, I was a bit skeptical of the claim about it being the closest thing to an Earth analog because of its larger size. With a diameter that is 60% larger than the Earth, it has only a slightly better than 50-50 chance of being a rocky planet. I thought that Kepler-186f was a better Earth-twin candidate because it is just 10% larger than the Earth---much more likely to be a rocky world.

However, reading through the "Finding Another Earth" report on the Kepler website, I grudgingly acknowledge that they make a good point about Kepler-452b (possibly) being a better Earth analog. My favorite Kepler-186f orbits on the outer edge of its star's habitable zone while Kepler-452b is comfortably in the middle of its star's habitable zone. But that 60% larger size for Kepler-452b is still a bit unsettling. 

Included in the latest batch of exoplanets were nine exoplanet candidates orbiting stars like the Sun with diameters between one to two times that of the Earth. If candidate K04878.01 turns out to be a true planet, it will be a much closer twin to Earth than Kepler-452b. It is just 4% larger than the Earth, its star is just 4% hotter than the Sun and the planet receives just 4% more energy from its star than the Earth does. The exoplanet candidate selection process is very good with about 95% confirmation rate, so I'm expecting a news conference about a true Earth 2.0 within the next several months.

Back home in Bakersfield, the evening sky belongs to Saturn. The other two bright planets of our evenings earlier in the summer were Venus and Jupiter. Those two are now setting within an hour after sunset, so they will be very low in the west by the time the sky gets dark enough to spot them. Probably too low to see in our dirty air. 

Saturn is high up in the southern sky by 9 PM between the dim stars of Libra and the brighter stars of Scorpius. Also up in the sky at a convenient time is the bulge of our galaxy in the direction of Sagittarius. A number of interesting star clusters, gas nebulae, dust nebulae, etc. are in that direction.

Almost straight overhead at 9 PM is the gorgeous globular cluster M13 in the constellation Hercules. It contains several hundred thousand stars gravitationally bound to each in a ball about 145 light years across at a distance of 25,100 light years from us. Humans had not yet formed civilization yet when the light we're seeing tonight was leaving those stars. 

The Moon a day past Full Phase rises at 9 PM tonight among the dim stars of Aquarius. By the night of the peak of the Perseid meteor shower on August 12/13, the Moon will be just a very thin Waning Crescent phase that rises just before sunrise. That leaves the sky nice and dark for meteor observing. Hurray! Get up out of the valley far from city lights for the best view of the Perseids. Best views of the Perseids are with just your eyes so you can see a big chunk of the sky at once. Binoculars and telescopes have too narrow a field of view to catch a meteor.

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. Visit the Dark Sky International website for more info.

Nick Strobel
Director of the William M Thomas Planetarium at Bakersfield College
Author of the award-winning website