Once upon a raisin

A Perseid meteor aims straight at the North Star above a neighborhood in Vero Beach, Florida this morning. Details: 30 sec 16mm f2.8 ISO 1600. Credit: Jim Schaff

Anybody see any meteors last night? This morning during the peak of the Perseid shower a huge boom went off near our home. How I wished it had been a meteorite, but of course it was only a thunderbolt.  Rain fell all night.

Composite of Perseid meteors photographed between sunset August 7 through sunrise August 11. Credit: Chris Peterson

Chris Peterson, who operates the ironically named Cloudbait Observatory, in Guffey, Colorado, has been tracking the Perseids since August 7 with an all-sky camera. His composite photo shows a total of 88 meteors through August 11. The curved trail at lower right is Jupiter. According to the most recent data from the International Meteor Organization (IMO), the shower peaked around 3:30 p.m. Central time yesterday August 12. While afternoon for U.S. observers, that was prime viewing time for sky watchers living in Eastern Europe and the Middle East. The hourly rate, which assumes excellent conditions and the radiant near the zenith, shot up to a healthy 82 Perseids at that time. For U.S. observers, the number decreased only a little to 76 per hour during the wee hours this morning. Ardent meteor watchers across the world contributed observations of 11,166 Perseids to arrive at those figures. With no moon, many faint meteors were visible, and the shower tossed fortunate sky watchers occasional brilliant fireballs with bright “smoke trails” as well. For more details, please go to the IMO’s Quick Look page.

Raisins have wrinkles and so does Titan, only Titan's wrinkles are mountain chains. The image at right shows mountainous terrain in the moon's northern hemisphere. Red indicates higher elevations, blue lower. Credit (left): Jorge Barrios. Right: NASA/JPL-Caltech

So what do raisins and Saturn’s moon Titan have in common? Wrinkles of course! Turns out Titan’s mountains, which rise about a thousand feet above the surface, were likely formed as the moon shrunk. Just as grapes dry and shrink to become raisins, Titan is shrinking as it cools, causing its surface to crumple into chains of icy mountains. The cooling starting not long after Titan formed and continues to this day.

A thick hydrocarbon haze in Titan's atmosphere makes it look hazy. Credit: NASA

Heat was first generated over 4 billion years ago from the gravitational attraction of the materials that gathered together to form Titan. That heat, as well as heat released from the decay of radioactive materials, leaks out into space, cooling the moon.  As this happens, parts of Titan’s denser subsurface ocean freezes and the crust thickens and shrivels. “Titan is the only icy body we know of in the solar system that behaves like this,” said Giuseppe Mitri, the lead author of the paper and a Cassini radar associate based at the California Institute of Technology in Pasadena. Most of the bumpy topography in the outer solar system’s icy moons was formed by expansion of their crusts.

Artists view based on pictures taken by the Huygens lander of how the surface and sky of Titan might look to a visiting astronaut. A mountain range is in the background. Credit: NASA

Scientists came to their conclusion about the shrinking moon by modeling various mixes of rocks, ice and underground water sources based on information sent by the Cassini probe until they succeeded in reproducing the appearance and locations of Titan’s hilly wrinkles. Not only is Titan the only moon in the solar system with a significant atmosphere and rivers of liquid hydrocarbons flowing across its bitterly cold surface, but it now may harbor a hidden ocean of water still warm from the moon’s formation. The closer we look at these little worlds on the fringe, the curiouser and curiouser they become.

The International Space Station (ISS) is still making excellent passes in the morning sky. If you’d like to see the brightest thing in the night sky after the moon and Venus, here are viewing times for the Duluth region. For times for your town, please click HERE. The ISS travels from west to east and looks like a brilliant, moving star. All passes below occur in the northern sky except the last.

* Friday morning Aug. 14 at 3:48 and again at 5:22 a.m.
* Saturday Aug. 15 at 4:14 a.m.
* Sunday Aug. 16 at 4:40 a.m.
* Monday Aug. 17 at 3:34 and 5:07 a.m.
* Tuesday Aug. 18 at 4 a.m. and 5:34 a.m. The second pass will be especially brilliant as the ISS cuts straight across the top of the sky moving northwest to southeast.

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About astrobob

My name is Bob King and I work at the Duluth News Tribune in Duluth, Minn. as a photographer and photo editor. I'm also an amateur astronomer and have been keen on the sky since age 11. My modest credentials include membership in the American Association of Variable Star Observers (AAVSO) where I'm a regular contributor, International Meteorite Collectors Assn. and Arrowhead Astronomical Society. I also teach community education astronomy classes at our local planetarium.

4 thoughts on “Once upon a raisin

  1. Bobby boy – We had clear skies out west. I went up to the ridge and counted 50 in one hour in 15 minute increments, 10, 18, 10, 12 from 2:30 to 3:30. Several nice meteors, but nothing spectacular. One in particular seemed to float in the air. Had two non-Persiads including the brightest one seen. It actually followed the same course and place in the sky as one seen the day before. I think the event should be called a meteor sprinkle though instead of shower. One would barely get wet in such a “shower”. I stayed up in the mountains over night sleeping in the back of my pickup so I could go marmot watching in the morning. The winds were tremendous though and kept me up the rest of the morning. The marmots seemed spooked also. Clear, sunny skies and blowing wind, unusual weather for the summer despite the name Hurricane Ridge. Rick

    • Hey, Rockinricky, nice to hear from you and thanks for the birthday card. I like the reflection of the ridge in the marmot’s eye. Great going on the Perseids – 50 in an hour is fantastic. Glad you wrote in to tell us.

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