Organization: Travelers in The Night
Description: Today’s 2 topics:
Dr. Grauer discovered 2014 JO25 with the 60″ scope. But on its 2017 pass by Earth it was seen to be a double-lobed peanut-shaped asteroid by an Arecibo/Goldstone radar study.
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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357 – Double Trouble
When I discovered 2014 JO25 with the NASA funded Catalina Sky Survey’s 60 inch telescope on May 5, 2014, it appeared as a single point of light as it moved past us. As 2014 JO25 approached the Earth from the direction of the Sun in 2017, no-one had any idea that it is really a double asteroid system nearly a mile in diameter.
The RADAR images obtained at NASA’s Goldstone Solar System Radar facility in California and the NSF’s giant RADAR dish in Puerto Rico in 2017, clearly show that 2014 JO25 has a double lobed peanut shape with the largest piece being about 2000 feet in diameter. It travels at 21 mi/s when it comes near Earth and fortunately will not enter the Earth’s atmosphere or even come very close again for at least 500 years.
From RADAR observations and a careful study of the changes in brightness of single appearing asteroid points of light, moving in the night sky, it is estimated that about 16% of the Earth approaching asteroids larger than 600 feet in diameter have orbiting companions. This observation prompts one to wonder how to defend against such a complex object. A further complication is that some asteroids are solid objects while others are rubble piles of space rocks held together by their tiny forces of gravity. Our best chance of a developing a defense for double trouble objects will be enabled by a careful study of every large object which comes within the range of our telescopes.
358 – Bigee
Evidence that relatively large, unknown close approaching asteroids exist came with my Catalina Sky Survey teammate Richard Kowalski’s recent discovery of 2017 HT2, a half mile diameter space rock, that on it’s current path can come to about 4 times the Moon’s distance from us. It is extremely unlikely to ever strike the Earth. Asteroid hunting surveys have discovered about 75% of the Earth approaching asteroids of 2017 HT2’s size leaving perhaps 150 more unknown ones out there.
Fortunately, the impact of an asteroid like Richard’s discovery, 2017 HT2, is rare, happening once every 200,000 years or so. When such an impact occurs it’s atmospheric entry energy is equivalent to 300 large hydrogen bombs and if it is stony it could make a crater 6 miles in diameter. Since the Earth’s surface is 3/4 covered with water an impacting object is likely to strike the ocean somewhere. As long as it happens far from shore the main effect would be to vaporize thousands of metric megatons of water and blow it into the atmosphere. The water vapor that makes its way to the stratosphere would act as a powerful green house gas and cause climate change. All of this would be fairly bad news for the residents of planet Earth and is the reason that detecting potentially impacting objects many years in advance is the highest priority for asteroid hunters. Given enough lead time humans could mount a space mission to a threatening object and deflect it from its dangerous path.
For Travelers in the Night this is Dr. Al Grauer.
End of podcast:
365 Days of Astronomy
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