Podcaster: Dr. Al Grauer
Title: Travelers in the Night Eps. 231E & 232E: Comet Ahoy & Earth’s Wobble
Organization: Travelers in The Night
Description: Today’s two stroy:
A story about Comet P/2016 BA14 flew past Earth at about 9 times the distance to our Moon from us. It was the third closest comet approach in recorded history.
A careful study of the Earth’s motion in space is a key to understanding past climate change and enables us to predict future patterns of flooding and drought.Wobbles tell all.
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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231E – Comet Ahoy
All comets are likely to have a small solid icy nucleus the nature of which remains a mystery because it is obscured by the glowing gases which surround it.
Recently a relatively dim object, Comet P/2016 BA14 flew past Earth at about 9 times the distance to our Moon from us. It was the third closest comet approach in recorded history. This situation allowed NASA scientists to use the Goldstone Solar System Radar located in California to obtain detailed RADAR images. These revealed the nucleus of P/2016 BA14 to be about 3000 feet in diameter. It slowly spins once very 35 to 40 hours as it travels on its 5.26 year orbital path around the Sun. Observations by the NASA Infrared Telescope Facility on Mauna Kea reveal the nucleus to be as dark as fresh asphalt which means it’s surface is about 4 times darker than that of our moon.
In the future this comet will make rather close approaches to Earth in 2048 and to Jupiter in 2188. These encounters make P/2016 BA14’s orbit unstable in the sense that it is likely to eventually hit Jupiter, Earth or Mars or perhaps even be ejected from the solar system.
Asteroid hunter’s will continue to search for potentially dangerous objects like Comet P/2016 BA14. We don’t really know how many more are out there and they are so dim that we can only detect them on their relatively close approaches to planet Earth.
232E – Earth’s Wobble
For those of us in the mid-latitudes the spin of the Earth on its axis carries us along at somewhere between 700 and 900 miles per hour. We don’t feel the motion because its a smooth ride. Superimposed on this steady motion are wobbles which effect GPS readings and can tell us about changes in ice sheets, water movements, and even climate change.
Recently scientists at NASA’s Jet Propulsion Laboratory published a paper which lays out how the movement of the water on Earth effects the Earth’s wobbles. For the past 100 years the Earth’s spin on its axis, which we call the North pole, has been moving southward towards Hudson Bay at the rate of a few inches per year. In 2000 the north pole’s motion took a sharp turn to the east and accelerated to nearly 7 inches per year in the direction of the British Isles.
After taking into account the changes in the ice sheets in Greenland and Antartica the NASA JPL researchers were left with an unexplained speedup in the Earth’s wobble. By using data from NASA’s GRACE satellite to track changes in gravity over the planet on a month to month basis these researchers were able to pinpoint the cause of the previously unexplained wobble. To their surprise their data pointed to the drought in India and the Caspian sea area as the driver for the wobble changes they observed.
Who would have suspected that a careful study of the Earth’s motion in space would turn out to be a key to understanding past climate change and enable us to predict future patterns of flooding and drought.
End of podcast:
365 Days of Astronomy
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