Organization: Travelers in The Night
Description: Today’s 2 topics:
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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6E – Suppose An Asteroid Is On A Collision Course With Earth
Over geologic times, the impacts of objects from space have produced significant changes to our planet’s biosphere. Earth threatening asteroids present a complicated challenge due to the wide range of compositions, sizes, orbital paths, and warning times that we can encounter.
A warning stay away from windows and seek cover would have eliminated most of the more than 1400 injuries which occurred when a house trailer sized asteroid entered the Earth’s atmosphere over Russia in February of 2013. Damage from an asteroid several times larger than that one could affect an area on the Earth similar to a hurricane’s destructive footprint. Such an impact could be mitigated by evacuations. Warning times for these smaller space rocks range from none, to hours to a few days.
Earth impacting asteroids between 2 or 3 football fields to several miles in diameter are fortunately rare. To limit their damage these large asteroids would have to be deflected. Lead times of decades are required to allow for an effective response.
One proposal involves changing the path of a threatening asteroid by striking it with a high velocity impacting space craft.
Another involves using a “gravity tractor” to exert a tiny force for a long time causing the asteroid to miss the Earth.
Another involves setting off a nuclear blast adjacent to the asteroid to vaporize a portion of its surface. This will produce a rocket type of thrust to change the threatening object’s trajectory.
The goal of the NASA Near Earth Object program is to provide the early detection critical to any of these mitigation techniques.
1E- Russian Fireball (Chelyabinsk)
Have you wondered what would happen if a rock from space landed near one of our large cities? We got a clue on February 15, 2013 when a large fireball appeared in the sky over Russia.
The event was caused when a small asteroid entered the Earth’s Atmosphere at a speed 41,000 miles per hour. The asteroid was approximately the size of a small house trailer.
The fireball it created released the energy of 90,000 tons of TNT, creating a super sonic boom. 1491 injuries were treated at local hospitals. They were caused primarily by flying glass from broken windows. 7,200 buildings were reported as being damaged.
More than, 10,000 Near-Earth Asteroids have been discovered. More than 1400 of them come close enough, and are large enough, to be designated as Potentially Hazardous Asteroids. None of them are likely to strike the Earth any time soon.
There are probably hundreds of thousands, of fairly small “rocks in space” which come near the Earth.
Very tiny ones, much less than the size of your little finger, become shooting stars. Larger space rocks are described as fireballs when they enter the Earth’s atmosphere. Every 500,000 years or so a very large one has caused changes in life on Earth.
Frequently objects the size of the one which caused the Russian Fireball come close to the Earth.
This particular asteroid approached the Earth at only about 15 degrees from the direction of the Sun.
It was impossible for us to find before it hit.
For Travelers in the Night this is Dr. Al Grauer.
End of podcast:
365 Days of Astronomy
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