Podcaster: Dr. Al Grauer
Title: Travelers in the Night Eps. 783 & 784: Kacper’s Centaur & Josh’s Two PHAs
Organization: Travelers in The Night
Link : Travelers in the Night ; @Nmcanopus
Description: Today’s two stories:
- Centaurs have long puzzled astronomers since they have traits in common with both asteroids and comets.
- So far asteroid hunters have discovered approximately half of the 5,000 PHAs which are likely to exist. Asteroid hunters will continue to search the sky to discover dangerous asteroids 50 years before impact so that humans can either deflect or pulverize them.
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:
Ep. 783: Kacper’s Centaur
My Catalina Sky Survey teammate, Caspar Wirzusch, was asteroid hunting in the constellation of Pisces with the 90-inch Bach telescope on Kitt Peak, Arizona, when an unknown moving object appeared in his images. After Caspar reported his observations to the Minor Planet Center, it was observed with additional telescopes in Arizona and Hawaii.
Astronomers use these data to calculate a preliminary orbit about the sun and give it the name 2023 VQ17. It is a mysterious object called a centaur and travels about the sun once every 157 years on a path that takes it from slightly inside the orbit of Saturn to further from the sun than Pluto. Centaurs, like Caspar’s discovery, have long puzzled astronomers.
If they are asteroids which have been flung from the asteroid belt by an encounter with Jupiter or Saturn, they are likely to reflect as much light as lunar dust, whereas if they are dormant comets that have come from the outer reaches of the solar system, they are likely to have a soot-like coating over an icy surface. Depending on 2023 VQ17’s reflectivity, its size estimates range from 20 to 80 miles in diameter. Astronomers really don’t know how many centaurs are in the solar system, with estimates ranging from 40,000 to 10 million.
2023 VQ17’s orbit crosses that of Saturn, suggesting that at some point in a few million years, it could be redirected by Saturn’s gravity to either head towards the inner solar system, where it could become an asteroid or a comet, or perhaps be flung away from the sun into truly deep space.
For Travelers in the Night, this is Dr. Al Grauer. Stay tuned.
Ep. 784: Josh’s Two PHAs
In the space of three nights, my Catalina Sky Survey teammate, Josh Hogan, discovered two potentially threatening asteroids. NASA designates both of them as Potentially Hazardous Asteroids, or PHAs for short, since they are larger than approximately 1.5 football fields in diameter, and can theoretically come to less than 19 times the moon’s distance from us. So far, asteroid hunters have discovered approximately half of the 5,000 PHAs which are likely to exist.
Neither of Josh’s PHA discovery, 2023 XV1 or 2023 XG10, are dangerous enough to make the NASA Sentry Table, which is the short list of asteroids which could pose a significant but remote threat to the Earth. The reason for keeping careful track of PHA-sized asteroids is that according to the Imperial College of London and Purdue University’s Impact Calculator, a PHA-sized asteroid impacts the Earth once every 25,000 years or so, creating a crater more than a mile in diameter and a half mile deep in sedimentary rock. If you were 10 miles from the impact, it would feel like a 5.9 Richter scale earthquake, and fragments as large as 6 feet in diameter would fall around you. The air blast with winds as high as 270 mph would destroy multi-story buildings, and 90% of the trees would be blown down. To avoid all that bother, asteroid hunters will continue to search the sky to discover dangerous asteroids 50 years before impact, so that humans can either deflect or pulverize them. Sleep easy.
Asteroid hunters are on the lookout, but haven’t spotted any dangerous ones with our number on it. For Travelers in the Night, this is Dr. Al Grauer. Stay tuned.
End of podcast:
365 Days of Astronomy
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