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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375 – Chelyabinsk Sized
There are likely to be tens of millions of small space rocks similar to the meteor which entered our atmosphere over Chelyabinsk, Russia in February of 2013. This celestial visitor exploded at an altitude of about 19 miles releasing about 30 times the energy of the atomic bomb dropped on Hiroshima. The shock wave from it’s airburst damaged more than 7,000 buildings and sent nearly 1,500 people to the hospital with injuries from flying glass and other debris. A small asteroid like the Chelyabinsk object is likely to enter the Earth’s atmosphere every 60 years or so and 3/4 of the time probably explode harmlessly over an ocean or other unpopulated area. The Chelyabinsk meteor was not spotted traveling through space in part due to the fact that it came in from close to the direction of the Sun.
Recently my Catalina Sky Survey teammate Rose Matheny was observing with our Schmidt telescope on Mt. Bigelow, Arizona when she discovered a Chelyabinsk sized space rock, 2017 MF, when it was about two and a half times the Moon’s distance from us traveling in our direction at 4 miles per second. 2017 MF was tracked by telescopes around the world as 38 hours later this small space rock made it’s closest approach, about the distance to the moon, from us. If 2017 MF had been on a collision course with planet Earth, Rose’s early detection would have allowed asteroid hunters to warn people in the impact area to avoid injury by staying away from doors and windows.
376 – Active Asteroids
When it was first spotted by astronomers at Space Watch on Kitt Peak, 2008 GO98 appeared to be one of many outer main belt asteroids moving through the night sky. 9 years later when my Catalina Sky Survey teammate Greg Leonard observed it with our 60 inch telescope on Mt. Lemmon it had a coma and a tail like a comet. Active asteroids like 2008 GO98 have asteroid orbits but sometimes show cometary activity which could be caused by a collision with another object and/or by thermal fracturing and ice sublimation caused by the slight warming they obtain from sunlight.
Sometimes, due to a collision or an interaction with Jupiter, the orbit of an active asteroid like 2008 GO98 can change to bring it near the Earth. When that happens the trail of dust it leaves could give rise to a meteor shower. In the distant past such objects could have brought the water which form our oceans as they impacted upon the young Earth.
3200 Phaethon [FAY-ə-thon] is soon to be a famous active asteroid. It has an Apollo Near Earth asteroid orbit, is made of dark material, sometimes appears comet like, and sheds dust giving rise to the December Geminid Meteor shower. Phaethon’s close approach to Earth in December of 2017 provides astronomers with a rare opportunity to study one of the mysteries of our solar system. You can come to appreciate one of Phatheon’s gifts to us by viewing some of the spectacular Geminid Meteors as they streak through the pre-Christmas night sky.
For Travelers in the Night this is Dr. Al Grauer.
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365 Days of Astronomy
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