Podcaster: Dr. Al Grauer


Title: Travelers in the Night Eps. 45 & 46: A World Full Of Holes How Far is Forever

Organization: Travelers in The Night

Link : Travelers in the Night ; @Nmcanopus

Organization: Travelers in The Night

Link : Travelers in the Night ; @Nmcanopus

Description: Today’s 2 topics:

  • It may surprise you to know that there are more than 180 confirmed impact craters on our planet.  It is likely that many more have been erased by the actions of wind and water.
  • When you look out in space you are also looking back in time.  Objects in space are older than they appear to us.

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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33E45 – A World Full Of Holes

When you look out in space you are also looking back in time.  Objects in space are older than they appear to us; the Moon more than a second  , Mars a  minute and a half,  and the Great Galaxy in Andromeda appears as it was 3 million years ago.  This situation is due to the fact that it takes time for light to travel the great distances in the Universe. 

You can experience this effect by observing a distant thunderstorm. On Earth light travels so fast that you see the lightning flash immediately after it happens.  On the other hand sound takes about 5 seconds to travel a mile. Therefore  if you see a lightning flash and hear the thunder10 seconds later, you are hearing sound from an event that happened 10 seconds in the past.

The NASA Hubble Space Telescope was pointed at a spot in the sky about 1/30 the width of your finger held at arms length. It was selected because it contains no objects which would block the view into deep space.  Hubble took more than 2,000 images of this dot in the sky over a 10 year period of time.  When they were combined electronically the resultant image contains 5,500 galaxies.  The most distant galaxies  appear as they were 13.2 billion years ago. Dr Garth Illingworth of the University of California at Santa Cruz, the principal investigator, points out that the Hubble Deep Field is the deepest image of the sky ever obtained.

In this one image you are able to travel in time down a corridor which leads from the time when galaxies like our Milky Way were  formed to about 450 million years after the Universe came into being with the big bang. 

34E – 46 – How Far is Forever

The asteroid Psyche is named for a Greek mythological figure. It  was discovered in 1852 as a moving point of light in the night sky.  This small world is about 155 miles in diameter and orbits the Sun between Mars and Jupiter every 5 years. 

The mass of an asteroid can be determined in principle, by how its gravity effects other objects which it encounters.  An asteroid’s size can be determined by how it dims a star as it passes between the star and us. The size and mass of Psyche suggest that it is dense enough to consist largely of iron. This hypothesis is supported by radar observations. These data suggest that the asteroid Psyche may be the core of what was once a rocky proto planet which lost its outer layers during catastrophic collisions in the early solar system. 

The iron world Psyche is unique among the many millions of asteroids in our Solar System which are composed of some combination rocks and ice.

Dr. Elkins-Tanton and her colleagues propose that NASA send a robotic space craft to orbit the asteroid Psyche for 6 months. During that time it would take images, measure magnetic fields, and make an accurate mass determination. 

The Earth’s core and magnetic field effects our weather and climate. However, we can’t travel to the center of the Earth.  Instead we must rely on earthquake waves to know anything about what is at our planet’s core.  A visit to Psyche would allow us to directly study a naked planet’s core and provide clues as to the nature of what is beneath our feet. 

For Travelers in the Night this is Dr. Al Grauer

End of podcast:

365 Days of Astronomy
The 365 Days of Astronomy Podcast is produced by Planetary Science Institute. Audio post-production by Richard Drumm. Bandwidth donated by and wizzard media. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at or email us at This year we will celebrates the Year of Everyday Astronomers as we embrace Amateur Astronomer contributions and the importance of citizen science. Join us and share your story. Until tomorrow! Goodbye!

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