Podcaster: Dr. Al Grauer
Title: Travelers in the Night Eps. 229E & 230E: Could Be Twins & Spray Paints
Organization: Travelers in The Night
Description: Today’s two stroy:
A pair of possibly related comets pass unusually close to Earth.
A gentle method of causing an asteroid to miss planet Earth
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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229E – Could be Twins
It is hard to have a personal feel for the microgravity of a comet since it is only a few ten thousandths of the pull of gravity we experience on Earth. When a comet comes near Jupiter or perhaps the Earth the tiny gravity which holds it together can be overwhelmed by gravity of the larger object and the comet’s structure disrupted.
Astronomers have observed comets breaking up into smaller pieces as they orbit the Sun. In a spectacular example, more than 20 years ago Comet Shoemaker-Levy 9 became a beautiful string of comets before it crashed into Jupiter.
Recently on two consecutive days, Comet P/2016 BA14 (PANSTARRS) and Comet 252P (LINEAR) both passed within a few million miles of planet Earth. These two objects have remarkably similar orbits which take them from near Earth out to close to the giant planet Jupiter. This situation suggests that the smaller of the two, P/2016 BA14, could be a fragment of Comet 252P which calved off of the parent object during a previous close encounter with Jupiter, Mars, or the Earth.
Currently, Astronomers are using data from the Hubble Space Telescope and NASA’s Infrared telescope in Hawaii to look for clues as to the nature of these potentially twin objects.
Comet 252P and P/2016 BA14 will not come this close to Earth again for millennia and are not threat to Earth. What makes them unusual is the opportunity given to humans to study these wanderers of the solar system relatively close up and personal.
230E – Spray Paints
Recently, NASA scientists using the giant RADAR telescope in Puerto Rico measured changes in the orbit of the asteroid Bennu. They found that a tiny sunlight pressure of 1/2 oz on this 68 million ton object has changed it’s orbit about a hundred miles over a 12 year period of time. These NASA astronomers thus measured the Yarkovsky force which was first suggested by a Russian engineer more than a hundred years ago. This Yarkovsky force, named for its proposer, occurs because sunlight absorbed by an object in space is reradiated in a directional way and thus acts like a tiny rocket motor. It is likely that, over the eons, this tiny effect has changed the course of families of asteroids between Mars and Jupiter causing some of them to be sent in our direction.
This leads to the question “Is it possible that the world could be saved by spray paint?” Well maybe.
One expects that an asteroid has a small positive charge because of the solar wind. It this is so then a stream of negatively charged paint particles could be projected towards the asteroid. The ultraviolet light from the Sun would melt the paint particles together which would coat the asteroid with a new color. The new color would be chosen to amplify the Yarkovsky force pushing the asteroid into safe orbit. Professor David Hyland of Texas A&M University has lead a team which has been studying this method of causing an asteroid’s orbit to change so that it will miss the Earth. His group is proposing to test these ideas on Apophis.
End of podcast:
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