Organization: Travelers in The Night
Description: Today’s 2 topics:
- Often observers report hearing a percussive sound, like a sonic boom from an aircraft, minutes after viewing a bright meteor fireball.
- The mysterious Earth approaching object Phaethon does not fit neatly into our definition of either an asteroid or a comet.
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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427 – Meteor Whispers
Often observers report hearing a percussive sound, like a sonic boom from an aircraft, minutes after viewing a bright meteor fireball. In addition, in a fewer number of instances, there are many reliable reports of observers hearing popping, hissing, and rustling sounds at the same time they are observing a very bright meteor traveling though the night sky. Professional astronomers have long dismissed these reports saying that what these people hear simultaneously with their visual observations cannot be due to to sound traveling from the meteors path since sound travels 800,000 times slower than light and would take 1.5 to 4 minutes to traverse the distance that the light does in a tiny fraction of a second. Recent scientific studies have begun to shed light on the interesting mystery of how the small number of what we now call electrophonic meteors produce simultaneous light and sound. One theory is that the flickering bright light produced in the meteor’s path is absorbed by by hair or other material near the observer’s ears producing acoustic sound waves. An alternate hypothesis is that as the meteor streaks through our atmosphere it ionizes air molecules whose motion in the Earth’s magnetic field generates radio waves which travel to objects near to the observer causing them to vibrate and thus produce sound. Either way observers with large amounts of hair or those near metallic objects like barbed wire fences are the most likely to hear these strange unusual sounds. If you are lucky you could hear a meteor’s dying whispers and could even be the first person to record these sounds on your cell phone.
428 – Phaethon
The mysterious Earth approaching object Phaethon (FAY-eh-thon) does not fit neatly into our definition of either an asteroid or a comet. Further it appears to be like the Peanuts character Pigpen in that it leaves a trail of dust and other fine debris in it’s wake which in the case of Phaethon produces the Geminid Meteor Shower to delight us every year around Christmas time. Phaethon is amazing in that every 524 days it makes a death defying flight to a point less than one of half of the planet Mercury’s distance from the Sun, where it’s surface temperature reaches a mind boggling 1,200 Fahrenheit. During one of these events the NASA Stereo Spacecraft A discovered that Phaethon had rock dust tail.
During it’s close approach to Earth in December of 2017 the Arecibo Observatory, having just recovered from hurricane Maria, used the unique combination of it’s giant 1,000 foot diameter dish and RADAR transmitting capability to ping Phaethon to obtain images with the RADAR signals it reflected back to us. These data reveal that Phaethon is roughly spherical, about 3.6 miles in diameter, has a several football field sized crater near it’s leading edge, and a dark area near one of it’s poles. By studying the second largest Potentially Hazardous asteroid Phaethon, as well as scores of other potentially dangerous Earth approaching objects, the Arecibo Observatory is an important global asset in humans efforts to prepare for the day when asteroid hunters discover an object with our number on it.
For Travelers in the Night this is Dr. Al Grauer.
End of podcast:
365 Days of Astronomy
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