Podcaster: Dr. Al Grauer


Title: Travelers in the Night Eps.   85E & 86E: A Large Strange One & Small Objects Visiting Our Neighborhood

Organization: Travelers in The Night

Link : Travelers in the Night ; @Nmcanopus

Description: Today’s 2 topics:

  • Jess Johnson discovered a 43 mile diameter Centaur near Neptune.
  • Rik Hill discovered 5 asteroids that come closer than the Moon.

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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85E: A Large Strange One

During the past 20 years more than 550 small asteroids ranging in size from 3 to 60 feet in diameter have entered the Earth’s atmosphere. They had impact energies ranging from 5 to 500,000 tons of TNT.  Newly released data show that most of them exploded high above the ground doing little or no damage at the surface.  NASA NEO Observations Program Executive Lindley Johnson stated  “We now know that Earth’s atmosphere does a great job of protecting Earth from small asteroids”.

Dr. Peter Brown of Western Ontario University and his co-authors have done a thorough analysis of data obtained when a small asteroid exploded over Chelyabinsk, Russia. This was an impressive and unusual event which injured nearly 1500 people. To an observer directly under it, the airburst would have appeared to be about 30 times brighter than the Sun.  Dr. Brown and his co-authors  comment that telescopic surveys have found only 500 of the estimated 20 million objects in the near Earth asteroid population in the 30 to 60 foot diameter range.  

Further, Dr. Brown and his co-authors have analyzed airbursts from meteors with energies of more than 1 kiloton of TNT.  They indicate that there may be 10 times the number of impacts of asteroids in the 30 to 150 foot size range than was previously suspected.  This finding suggests that the human population may be more at risk from smaller rather than larger Earth approaching asteroids.

86E: Small Objects Visiting Our Neighborhood

My, University of Arizona,  Catalina Sky Survey, teammate, Rik Hill, continues to add to the collection of small Earth approaching asteroids which he has discovered.  He is able to distinguish these faint points of light in the night sky from the millions of stars his equipment images, by their rapid motion relative to other objects in space.   Five of these recently discovered small space rocks, were followed up  by telescopes in  Illinois, France, New Mexico, Tennessee, Pennsylvania, and Arizona  All of these observations were necessary to determine each asteroid’s size and path around the Sun.

All of this set of Rik’s 5 small asteroids come closer than the Moon.  They range in size from 20 to 50 feet in diameter and would have impact energies between 100 and 1000 kilotons of TNT if they were to enter the Earth’s atmosphere. 

Our NASA funded group at the University of Arizona has discovered the majority of the nearly 800 known 30-60 foot diameter asteroids similar to the one which injured nearly 1500 people in Russia in 2013.

There are probably 20 million asteroids in this size range which come near the Earth.  A few of these may eventually impact our planet.  Those that do are likely to explode high in the atmosphere producing a supersonic boom.

We are not more likely to be hit by a small asteroid  than we have in the past. However, we are becoming more likely to be able to provide a tornado like warning for people in the affected area to stay away from doors and windows.

For Travelers in the Night this is Dr. Al Grauer.

End of podcast:

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