October 16, 2022

Mid-October at 3:30 AM looking east-southeast

Sunday, October 16, 2022

This Thursday, October 20, is the International ShakeOut Day when different organizations, including schools and colleges, will hold earthquakes drills emphasizing the Drop, Cover, and Hold On technique that is much better than the running outside, standing in the doorway, or bogus “triangle of life” techniques. It doesn't help, though, that most schools (including BC) also schedule fire drills to happen right after the earthquake drills, so students will be evacuating outside for the fire drill, opposite to what we should do for an earthquake. 

Anyway, the William M Thomas Planetarium will show “Earthquake: Evidence of a Restless Planet” on Thursday evening. We'll begin with a tour of the evening sky and then use the dome to take a look under the Earth's surface to see how the action of plate tectonics causes the Earth to move beneath our feet. Two weeks later, November 3, we'll show “From Dream to Discovery: Inside NASA”. Tickets are still available for both shows through Vallitix.

The night of October 20/21 is also the peak of the Orionid meteor shower. The Orionids are active from September 26 to November 22 because the dust trail left behind by Comet Halley, responsible for the shower, is fairly broad. 

When comets get close to the sun, bits of rock and dust embedded in the water, carbon dioxide, carbon monoxide, methane, and ammonia ices are released into space as the ices sublimate. Whether the rock and dust are released in explosive jets or a bit more gently, the result is a dust trail left behind in the comet's orbit. If the comet's orbit crosses Earth's orbit, we run into the dust trail and we see the streaks of light coming from a particular direction as the comet bits vaporize high up in the atmosphere far from the surface.

The Orionids streak through the atmosphere at 41 miles per second. Thank goodness we have an atmosphere to shield us! On the night of the peak, we should see between ten to twenty meteors per hour. The direction the meteors will appear to come from, the radiant, is in the upper left corner of the Orion constellation boundary where the fainter stars of Orion's club held in his right hand are found. If you draw a line from the bright red star Betelgeuse at the upper left part of the main part of Orion that you can see from anywhere in Bakersfield and the even brighter orange-red Mars about a fist-and-a-half at arm's length above Betelgeuse, the radiant of the Orionids will be midway between them and to the left of that line. The radiant will rise several hours before the moon rises. This year, the moon will be just a waning crescent, just 21% lit up and the moon will rise in the east at about 3:15 to 3:30 AM on October 21, depending on how close you are to the mountains.

Two other meteor shower that ramp up a bit at the very end of October/first part of November are the Southern Taurids and Northern Taurids from Comet Encke. The Southern Taurids have several peaks but don't produce more than five meteors per hour. However, the ones that do flash across the sky are the larger very-easy-to-see fireballs. The Northern Taurids also produce fireballs and every seven years produce more remarkable ones. The last remarkable year was 2015, seven years ago, so this year should be a good year. The Northern Taurids peak in the second week of November and the moon will be in a nearly full waxing gibbous phase then.

Speaking of fireballs, one recent one fireball caught on film over Canada by hundreds of security and dashboard cameras plus the Global Fireball Observatory and an orbiting satellite has had its path traced back to the Oort Cloud. What makes this fireball so noteworthy is that it looks like the fragment of an asteroid instead of a fragment of a comet. The Oort Cloud is a spherical cloud of comets that extends out about one-third to one-half of the distance to the nearest star. It is thought to be the result of the giant planets gravitationally slingshotting trillions of comets, in the earliest days of the solar system, randomly every which way to build up a spherical cloud of comets. The Oort Cloud was thought to be exclusively made of the dirty icebergs we call comets. Another fireball in 1979 shared many of the same characteristics with an orbit that also places it coming from the Oort Cloud despite being a rocky asteroid. Because it is just two rocky asteroid fireballs observed so far coming from the Oort Cloud, it's difficult to say how much of the model of the formation of the solar system needs to be adjusted so that the outer giant planets can fling asteroids as well as comets to the outer edges of the solar system. However, it does indicate that the formation of the solar system was messier than originally thought. Still more to learn which is what makes research science so darn interesting and worthwhile!

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