Podcaster: Dr. Al Grauer
Title: Travelers in the Night Eps. 537 & 538: Earth Glow & Asteroid Slam
Organization: Travelers in The Night
Description: Today’s 2 topics:
- Although you can’t see the extremely faint geocorona, you can observe other components of the Earth’s nightly airglow.
- Detected far enough in advance, a Chelyabinsk sized space rock could be slowed slightly so that it would arrive more than 7 minutes late and safely pass behind our home planet.
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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537 – Earth Glow
During a total solar eclipse the Moon covers the Sun’s bright photospheric disk and we are able to see the solar corona. In 1972 Apollo 16 astronauts took an ultraviolet image of the Earth from the Moon which shows that the Earth too has a faint corona of gas surrounding it.
In a paper published in the February 15, 2019 online Journal of Geophysical Research: Space Physics scientists report that data from the NASA/ESA Solar Heliospheric Observatory (SOHO) obtained in 1996,1997, and 1998 reveals the Earth’s hydrogen corona extends 50 times our planet’s diameter to a nearly a distance of 400,000 miles. This means that the Moon flies through the outer limits of our atmosphere where there are less than three hydrogen atoms per cubic inch and that so far humans have never completely left the Earth’s atmosphere behind. Although you can’t see the extremely faint geocorona, you can observe other components of the Earth’s nightly airglow.
The most prominent features are the auroras which can dominate the night sky in areas near the north and south magnetic poles. In between the polar regions, on a clear moonless night, you can see and even walk around by the light of the stars and airglow at a natural night sky location like the Cosmic Campground International Dark Sky Sanctuary in New Mexico. Scientists are exploring how Earth’s glow relates to our weather and climate.
538 – Asteroid Slam
Moving at about 70,000 mph on its path about the Sun, the Earth travels the distance one of its diameters every 7 minutes. Thus if the arrival time of an asteroid on a collision course with our planet could delayed by 7 minutes it would safely pass behind our planet as it orbits the Sun. A lesson as to why this could help came in February of 2013 when the six story building sized Chelyabinsk meteor exploded with the force of a nuclear weapon injuring more than 1,200 people and damaged buildings in Russia.
Detected far enough in advance, a Chelyabinsk sized space rock could be slowed slightly so that it would arrive more than 7 minutes late and safely pass behind our home planet. One way to ensure its late arrival is to slam a dangerous space rock with a heavy projectile. The impact and the ensuing plume of debris which would act like a tiny rocket would work together to slow the space rock just enough to ensure its late arrival as it crosses our planet’s orbit about the Sun.
In April of 2019 Japan tested this idea by slamming a copper cannonball into a 3,000 foot wide asteroid. In the next such experiment NASA will use a SpaceX Falcon 9 rocket to launch the Double Asteroid Redirection Test or DART Mission which will slam into the 500 foot satellite Didymoon which orbits the half mile diameter Didymos. These experiments will give us the know how to deal with a dangerous space rock which has our number on it.
For Travelers in the Night this is Dr. Al Grauer.
End of podcast:
365 Days of Astronomy
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