Podcaster: Dr. Al Grauer


Title: Travelers in the Night Eps. 203E & 204E: Blinky & Blinky Revealed

Organization: Travelers in The Night

Link : Travelers in the Night ; @Nmcanopus

Description: Today’s two stroy:

  • Eric Christiensen discovered 2015 YJ, that had missed the Earth by 40,000 miles.
  • Dr. Bill Ryan determined that 2015 YJ is a collision fragment perhaps one and a half times longer that it is wide and is spinning on its axis once every 9 minutes.

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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203E: Blinky

Some things immediately grab your attention. On a long winter’s night my Catalina Sky Survey team Captain Eric Christensen was taking 4 images of the same place in the night sky spaced out over 45 minutes or so.  During this short interval nearby objects show up as a rapidly moving points of light.  Most of the time each of the images of the same object have about the same brightness.  To Eric’s surprise on some of his images, his discovery was about  twice as bright as it was on others.    I nicknamed it “Blinky” and observed it the next night providing the additional data which allowed the Minor Planet Center to find its orbit and estimate its size.  These calculations provided some interesting surprises.  Turns out this object now named 2015 YJ had missed the Earth by 40,000 miles 59 hours earlier traveling at a speed of 10 miles per second. At that point it could have been spotted by a backyard telescope equipped with an electronic camera if anyone had been looking. Further, 6 hours and 29 minutes before it streaked by the Earth, 2015 YJ aka Blinky had missed the Moon by only 80,000 miles.

The fact that Blinky changes brightness rapidly suggests that it has an elongated shape and thus reflects different amounts of sunlight as it spins on its axis. 

If you had been on your way to the Moon in your space ship, seeing the tumbling 2015 YJ coming by at 10 miles/second would have gotten your adrenaline pumping. 

204E: Blinky Revealed

The Magdalena Ridge Observatory in New Mexico is home to the largest telescope in the world which is routinely used for Earth approaching asteroid research. The telescope’s primary mirror is almost 8 feet in diameter and is housed in a mount which allows it to move around the sky at an amazing 10 degrees per second. Dr. Eileen Ryan is the observatory’s director and her husband Dr. Bill Ryan uses this large telescope to study solar system objects.

On his discovery images, my Catalina Sky Survey team leader Eric Christensen was amazed to see rapid brightness changes in the Earth approaching asteroid he had just discovered. He immediately suspected it to be an irregularly shaped rapidly spinning object and contacted the Ryans for followup observations. I continued to track this object on my observing shift on the telescope and gave it the nickname “Blinky”.  Dr. Bill Ryan’s first observations of 2015 YJ aka Blinky encouraged him to continue to measure its brightness changes as it streaked through the night sky. In Dr. Bill Ryan’s experiences a typical small Earth approaching object spins at a rate of once every two hours or so. When 2015 YJ tripled in brightness every 9 minutes he knew that Blinky is unusual and is spinning too fast for its tiny gravity to hold it together unless it is a solid object. 

Blinky is likely to be a collision fragment perhaps one and a half times longer that it is wide and is spinning on its axis once every 9 minutes. What violent event which created Blinky remains a mystery. 

For Travelers in the Night this is Dr. Al Grauer.

End of podcast:

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