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Podcaster: Dr. Al Grauer
travelers-in-the-nightTitle:
Travelers in the Night Digest: Dead Comet & Jupiter’s Comet

Organization: Travelers in The Night

Link : Travelers in the Night

Description: Today’s 2 topics:

  • A potentially hazardous dead comet makes a close approach to Earth.

  • The giant planet Jupiter has its own family of comets orbiting our Sun.

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:
211-Dead Comet

A potentially hazardous asteroid made a close approach to our Moon and then to the Earth late in 2015.  2015 TB145 as it is now called, had come near humans six times between 1920 and 2015 but had gone unnoticed as it zipped through the night skies.  On the 2015 close approach to us, the Pan-STARRS group in Hawaii found it heading towards the Sun at a speed of 23 miles/second.

On its 2015 close approach,  2015 TB145 was imaged by the RADAR at  Goldstone, the Green Bank Telescope,and the Arecibo Observatory.  These data show that this interesting object is about 2,000 feet in diameter and rotates about once every 5 hours.  Dr. Vishnu Reddy a research scientist at the Planetary Science Institute in Tucson, Arizona said “We found that the object reflects about six percent of the light it receives from the sun”.  Dr. Reddy continued “That is similar to fresh asphalt, and while here on Earth we think that is pretty dark, it is brighter than a typical comet which reflects only 3 to 5 percent of the light.   Since 2015 TB145 reflects about half the light one would expect to obtain from a typical asteroid but we don’t observe the gas cloud of an active comet we are led to the conclusion that 2015 TB145 is a dead comet.

 What event gave 2015 TB145 a skull like appearance and placed on its current path remains a mystery.

214-Jupiter’s Comet

The giant planet Jupiter has more than twice the mass of all of the other planets, asteroids, and comets in the solar system put together.  As well as its moons Jupiter’s gravity controls the orbits of thousands of asteroids that proceed and trail it in its path around the Sun.  Jupiter also has a family of short period comets which it has collected from the Kuiper belt  beyond the orbit of the planet Neptune. The most well known of these, Comet Shoemaker-Levy met its fate in a collision with Jupiter more than 20 years ago.
A typical Jupiter family of comet’s member orbits the Sun in less than 20 years. It actively produces a gas cloud or coma for perhaps a thousand orbits around the Sun over a period of time of 10,000 years or so. What is left after the volatile material evaporates is is a small dark rocky lump or rubble pile orbiting the Sun in an elliptical orbit.
Recently my Catalina Sky Survey teammates Greg Leonard  and Rose Matheny were using a Schmidt telescope on Mt. Bigelow, AZ when they discovered an Earth approaching object now named 2015 XL128.  Observations from telescopes in Arizona, Pennsylvania, Germany, Italy, and France indicate that this new object is relatively large and on a 6 year path around the Sun. These data suggests that 2015 XL128 may be a dormant Jupiter Family Comet.   Not too worry, 2015 XL128 never gets closer than about 13.7 million miles from planet Earth.
For Travelers in the Night this is Dr. Al Grauer.

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365 Days of Astronomy
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