Podcaster: Dr. Al Grauer
Title: Travelers in the Night Eps. 91E & 92E: Small Asteroids in Earth-like Orbits & Jupiter Trojan Confusion
Organization: Travelers in The Night
Link : Travelers in the Night ; @Nmcanopus
Description: Today’s 2 topics:
- Four days after it made its closest approach to Earth, I found a 10 foot diameter asteroid with the NASA funded University of Arizona 60 inch telescope on Mt. Lemmon.
- Humans know of approximately half million main belt asteroids orbiting the Sun between Mars and Jupiter. We have also found approximately 11,000 Earth approaching asteroids.
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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Transcript:
91E: Small Asteroids in Earth-like Orbits
Four days after it made its closest approach to Earth, I found a 10 foot diameter asteroid with the NASA funded University of Arizona 60 inch telescope on Mt. Lemmon. At that point it was 838,000 miles from us and was moving away at about 3 miles/second. Previously, It had been about half the distance to the Moon from planet Earth. This small asteroid orbits the Sun every 349 days on a path which crosses our orbit twice a year. Calculations by the NASA – JPL group indicate that it can come within 2 Earth diameters of us.
A week later my Catalina Sky Survey Survey team leader, Eric Christensen found a slightly larger small asteroid. It orbits the Sun in 388 days and can closer than 4 Earth diameters to us.
Either of these small asteroids would fit into the bed of a dump truck. Their speeds relative to Earth are well within our rockets ability to catch them.
These two asteroids do not pose a threat to humans. If they ever did enter the Earth’s atmosphere, they would likely burn up at high altitude producing a supersonic boom. They are interesting because they could be targets for NASA’s Asteroid Redirect Mission. The concept for this project is to redirect a small asteroid into orbit around the Moon where it would be visited by Astronauts using the Orion Spacecraft. This mission will provide us with scientific data about Earth approaching objects and develop the capability for humans to explore the planet Mars.
92E: Jupiter Trojan Confusion
Humans know of approximately half million main belt asteroids orbiting the Sun between Mars and Jupiter. We have also found approximately 11,000 Earth approaching asteroids. Members of these two groups can be recognized by briefly observing their motion since their paths about the Sun are very different. Jupiter Trojans, on the other hand, occupy a point either 60 degrees in front or behind Jupiter as it moves about the Sun. Their orbit around the Sun takes about 5 and a half years so short pieces of one of their orbits can mimic the path of an Earth approaching object. When Jupiter Trojans are opposite to the Sun, their little full moon faces are pointing towards Earth. When they are in this position in the sky we have to sort through a number of them so we can separate them from real near Earth objects.
The Jupiter Trojans oscillate about a stable point 60 degrees in front of or behind a planet as it orbits the Sun. This geometry was predicted by Joseph-Louis Lagrange in 1772. More than 100 years later Astronomers began to discover Jupiter Trojans. Today we know of almost 6,000 of the perhaps several hundred thousand of these asteroids which are larger than a kilometer in diameter. The largest one, Hektor. It is about 120 miles in diameter. Most of the Jupiter Trojans are much smaller than Hektor and may be fragments of larger ones which collided with each other.
Someday humans may visit these distant asteroids and find them to be a rich sources of raw materials.
For Travelers in the Night this is Dr. Al Grauer.
End of podcast:
365 Days of Astronomy
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