Podcaster: Dr. Al Grauer


Title: Travelers in the Night Eps. 251 & 252: Catching Shadows & Tough Guy

Organization: Travelers in The Night

Link : Travelers in the Night ; @Nmcanopus

Description: Today’s two stroy:

  • On Jun 29, 2015, Pluto occulted a star, UCAC4 347-165728 showing us that it had an atmosphere. Now high school students can join in the hunt for TNO occultations.
  • The Earth-approaching asteroid 3200 Phaethon and its debris trail gives us the Geminid meteor shower each December. 2016 LV47 was discovered by Eric Christensen of the Catalina Sky Survey, but it’s a 1,000′ diameter solid body instead of a rubble pile like Phaethon.

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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251E – Catching Shadows

For years humans knew Pluto, the first Trans-Neptunian object to be discovered, only as a moving point of light in the night sky. It wasn’t until 58 years after it’s discovery that astronomers were able to observe a star as Pluto passed in front of it. These data gave an accurate diameter and also proved that Pluto has an atmosphere. There are estimated to be 100,000 Trans-Neptunian bodies larger than 60 miles or so in diameter. They have stories to tell about the beginning of the solar system. Additionally, sometimes, a passing star changes one of their orbits sending it into the inner solar system and perhaps near to us.

The size and shape of a Trans-Neptunian can be found by measuring the size of the shadow it creates as it passes in front of a star. Because it is not known in advance exactly where such a shadow will be located on planet Earth, it is necessary to have a wide net to catch it.

To answer this need, a network of 56 stations each equipped with a telescope, camera, and timing device will allow the operators to measure a star’s brightness as a Trans-Neptunian object passes in front of it. These science teams have been established primarily at schools usually at the 9-12 grade level. These are spaced more or less evenly along a path through the western states that goes from Canada to Mexico.

In the process of measuring the sizes and shapes of distant members of the solar system the students and teachers working together on this project will have the exciting opportunity to be a part of an authentic scientific investigation.

252E – Tough Guy
Many of the Earth approaching asteroids that we discover are loose collections of rocks and dust held together by their tiny gravity. If such a rubble pile passes near the Sun, the strong heating it experiences, can cause it to shed a trail of debris behind it. If the Earth runs into such a debris trail we are treated to a meteor shower. An example of this is the Earth approaching asteroid Phaethon which apparently is the source of the spectacular mid-December Geminid meteor shower.

Recently my Catalina Sky Survey team captain Eric Christensen discovered a 1000 foot diameter potentially hazardous asteroid now called 2016 LV47. It orbits the Sun once every 2.29 years on a path that takes it from 64% of Mercury’s distance from the Sun out to between Mars and Jupiter. When it is closest to the Sun it zips along at 51 miles/second and receives nearly 4 times the amount of energy which heats the surface of the planet Mercury to 800 F. The fact that it survives this experience suggests that it may be a solid metallic/rocky asteroid.

An asteroid the size of 2016 LV47 strikes the Earth every 80,000 years or so making a crater more than 3 miles in diameter as it releases the energy of several thousand million tons of TNT. Not to worry 2016 LV47 never gets closer than about 13 times the Moon’s distance from us.

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

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