Organization: Travelers in The Night
Description: Today’s 2 topics:
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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19E – A Gentle Breakup Of An Asteroid
Newton formulated that the change in motion for an object depends on the amount of force and the length of time it is applied. For this reason a baseball pitcher tries to have a long pull on the ball before releasing it.
Astronomers have a theory, called the Yorp effect, that light from the Sun produces a very tiny torque which increases the rate of spin of an object. The effect is so small that it would take billions of years to be produce a measurable outcome. How can such an idea ever be tested?
In September of 2013, the Pan-STARRS group found a strange moving object in the night sky. The plot thickened when the Keck Telescope on Mauna Kea Hawaii found that instead of being a single body it appeared to be three small objects embedded in a cloud of gas and dust several thousands of miles in diameter. The Hubble Space Telescope was used to see what is going on.
Hubble found that this object changes significantly over a period of months, that it has 6 tails, and that pieces of it continue to emerge from the center and slowly move away at a walking pace.
An asteroid collision is too violent to cause what is seen. The object is too cold for expanding gases to cause it to break up. The best explanation which fits the data is that Sun light has slowly, over billions of years, increased P/2013 P5’s rate of spin causing it to gently come apart. Some of the dust and small particles which escape from it will orbit the Sun. When the Earth runs into them we may see them as meteors in our night sky.
120E – A Peanut Shaped Asteroid with a Moon
It appears that Hektor and its moon were created by a collision between two icy asteroids early in the 4.5 billion year history of our solar system when things were more chaotic. They happened to land in a gravitational dip which has allowed them to remain relatively undisturbed for billions of years.
The asteroid Hektor orbits the Sun at a point where the gravity of the Sun and Jupiter create a stable point 60 degrees in front of the giant planet. In 1907 Hector was discovered as a moving point of light in the night sky. For the next 99 years its true nature remained unknown. In the past few years the Keck Telescope in Hawaii has discovered that the main body is a 230 mile long peanut shaped object. Most recently Keck was used to discover that Hektor has a 7.5 mile diameter moon which has a dense core surrounded by icy layers. This asteroid moon orbits the peanut shaped Hektor in a stable orbit every 3 hours.
Recently, NASA scientists using the Goldstone Radar telescope were taking advantage of a close approach of a potentially hazardous asteroid to obtain radar images. These data show 2006 DP14 is a peanut shaped object about 1300 feet long. It slowly spins with a 6 hour period. Previous data from Goldstone and the Arecibo Observatory in Puerto Rico suggests that more than 10 % of near Earth asteroids larger than 650 feet in diameter have a peanut shape. This knowledge will be important if we find one of these strange objects is on a collision course with our planet.
For Travelers in the Night this is Dr. Al Grauer.
End of podcast:
365 Days of Astronomy
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