Podcaster: Dr. Al Grauer
Title: Travelers in the Night Eps. 207E & 208E: Zero and Deuce
Organization: Travelers in The Night
Description: Today’s two stroy:
- Newly discovered 2016 AM2’s path had a zero distance between it and the Earth’s orbit.
- Within the space of 31 hours the NASA/NEOWISE spacecraft reported the discovery of a pair of comets: C/2015 X8 & C/2015 YG1.
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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I had to look at my computer screen a second time to be sure. What I saw is that a newly discovered object’s path had a zero distance between it and the Earth’s orbit around the Sun. When asteroid hunters find and track a new Earth approaching asteroid we determine how close its orbit comes to that of planet Earth. We call that measurement its Earth Minimum Orbit Intersection Distance. Its units are the AU which is the Earth’s distance from the Sun. In these units the Moon is .0027AU from us. Recently my Catalina Sky Survey team Captain Eric Christensen discovered a small space rock with a minimum orbital intersection distance of 0.0000 AU. This does not mean it will hit the Earth anytime soon because it an the Earth would have to both be there for that to happen. However, this space rock has gotten asteroid hunter’s attention since we seldom see an object whose path so nearly crosses ours.
This new objects name is 2016 AM2. It is about the same size as the one which entered the Earth’s atmosphere over Russia in 2013 injuring nearly 1,500 people. In 2015 this small space rock missed both the Earth and our moon by several hundred thousand miles.
2016 AM2’s current path comes less than an Earth radius from our planet’s path about the Sun. So far we have observed this space rock for only 2 days out of its 958 day path around the Sun. We will need obtain more data on 2016 AM2 the next time it comes near to be able to determine if and/or when a collision might occur.
A picture of your teeth in visible light shows what is on the outside while one taken in X-rays reveals what is inside. In a similar way images of comets in visible light show what is on the outside while those obtained using their thermal infrared glow tell you about their innards.
The NASA/NEOWISE mission utilizes a spacecraft whose orbit passes above the North and South poles. Its infrared eyes point opposite to the Earth at a right angle to direction of the Sun. Comets discovered by NEOWISE are detected by measuring their thermal infrared glow. NEOWISE can thus find comets which are dark and do not reflect much sunlight in the visible part of the spectrum.
Within the space of 31 hours the NASA/NEOWISE spacecraft reported the discovery of a pair of comets.
One of them, C/2015 X8 has an orbital period of about 121 years. It is currently heading away from the Sun on a path that will take it to between the orbits of Uranus and Neptune before it heads back in our direction again.
The other, C/2015 YG1 has a period of 350 years or so and is on a path which does not come as close to the Sun as the planet Mars. It travels a very elliptical path which extends to well beyond the dwarf planet Pluto.
It is likely that the gravity of the giant planet Jupiter will change the orbits of these two comets. It could direct them towards the Earth, the Sun, or fling them from the solar system.
For Travelers in the Night this is Dr. Al Grauer.
End of podcast:
365 Days of Astronomy
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