Podcaster: Dr. Al Grauer
Title: Travelers in the Night Eps.609 & 610: Lurking & Atmospheric Gravity Waves
Organization: Travelers in The Night
Description: Today’s 2 topics:
- Greg Leonard discovered 2,200’ diameter 2020 PC5.
- Gravity wave examples are wind-generated waves on the surface of an ocean or lake, tsunamis, ocean tides, and wave clouds.
Bio: Dr. Al Grauer is currently an observing member of the Catalina Sky Survey Team at the University of Arizona. This group has discovered nearly half of the Earth approaching objects known to exist. He received a PhD in Physics in 1971 and has been an observational Astronomer for 43 years. He retired as a University Professor after 39 years of interacting with students. He has conducted research projects using telescopes in Arizona, Chile, Australia, Hawaii, Louisiana, and Georgia with funding from NSF and NASA.
He is noted as Co-discoverer of comet P/2010 TO20 Linear-Grauer, Discoverer of comet C/2009 U5 Grauer and has asteroid 18871 Grauer named for him.
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Statistically asteroid hunters have found more than 90% of the asteroids whose impact could cause global climate change. However, recently, my Catalina Sky Survey teammate Greg Leonard was observing in the constellation of Pegasus with our 60 inch telescope on Mt. Lemmon, Arizona when he spotted a fast moving point of light in the night sky. After Greg reported his observations to the Minor Planet Center his discovery was tracked by telescopes in
Arizona, Germany, Pennsylvania, and California. Scientists used these data to calculate this previously unknown asteroid’s orbit about the Sun, estimate it to have a diameter of 2,200 feet, and give it the name 2020 PC5. Currently this large space rock poses no threat to Earth since on its present path it never comes closer than 29 million miles to our home planet.
According to the Purdue University and Imperial College of London’s impact calculator an asteroid the size of 2020 PC5 enters the Earth’s atmosphere once every 190,000 years or so, breaks into pieces at an altitude of about 154,000 feet, and strikes the ground in broken pieces at 6.8 mi/second. One hundred miles from an impact like this you would experience a shock like a Richter Scale 7.2 magnitude Earthquake and be pummeled by 1/2 diameter, asteroid produced gravel. This impact would make a crater 5 miles in diameter and 2,000 feet deep in sedimentary rock. Asteroid hunters are happy to report that so far we have not discovered any such object like this on a collision course with Earth.
610: Atmospheric Gravity Waves
It takes a very carefully designed experimental apparatus to detect
ripples in space-time called cosmic gravitational waves. However, gravity waves like wind-generated waves on the surface of an ocean or lake, tsunamis, ocean tides, and wave clouds are part of our everyday experiences. Atmospheric gravity waves can be powerful. In September of 2018 two glider pilots surfed an atmospheric gravity wave created by high speed polar winds as they encounter the Andes mountains. Amazingly their unpowered aircraft reached an altitude of more than 76,000 feet on a wave which itself can travel to more than 100,000 feet above sea level .
Further, atmospheric gravity waves can travel out to the edge of space into the ionosphere where they create wave like patterns in meteor trails. In May of 2013 the superstorm cell that generated the devastating EF5 tornado in Oklahoma produced concentric gravity waves in the ionosphere hundreds of miles above the Earth’s surface. This disturbance at the edge of space was observed 1 to 2 hours after the massive tornado hit Moore.
A side benefit of the GPS satellite system that we use to find a restaurant is that GPS signals can be used to detect and track atmospheric gravity waves created by tsunamis and earthquakes. So far scientists have been able to use this technique to study the effects of tsunamis in the Pacific Ocean. By studying atmospheric gravity waves generated by tornadoes, hurricanes, earthquakes, and tsunamis scientists hope we may be able to mitigate the disasters that these events can cause.
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