Podcaster: Dr. Al Grauer


Title: Travelers in the Night Eps. 117E & 118E: A Three-City-Block-Sized Asteroid & Things That Dim In The Night

Organization: Travelers in The Night

Link : Travelers in the Night ; @Nmcanopus

Description: Today’s 2 topics:

  • Carson Fuls and Jess Johnson discovered 2015 DH155 which comes close enough and is large enough be be classified as a Potentially Hazardous Asteroid.
  • Dr. Alice Quillen of the University of Rochester began to wonder if there are objects which dim in ways that will tell us about their natures. 

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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117E: A Three-City-Block-Sized Asteroid

Recently my Catalina Sky Survey teammates Carson Fuls and Jess Johnson discovered an asteroid which comes close enough and is large enough be be classified as a Potentially Hazardous Asteroid.   It was subsequently observed by telescopes in New Zealand, Australia, Italy, Arizona, Pennsylvania, and Illinois and given the name 2015 DH155.

An asteroid of 2015 DH155’s size is likely to strike the Earth every 60,000 years or so. Its orbit causes it to be traveling at 29,000 miles per hour when it crosses the Earth’s path. If an asteroid like this were to impact on our planet it would release 10 times the energy of the most powerful hydrogen bomb ever exploded.  Such an event could make a crater several miles in diameter and damage trees and buildings over several thousand square miles if it happened over a land area.  

Asteroid 2015 DH155 travels once about the Sun in a bit less than 4 years on a path that takes it from out to well past Mars to near the planet Venus. For all but about 3 months every 4 years it is invisible to Earth’ telescopes.  When humans discovered this 800 foot diameter asteroid, it was about 25 million miles from planet Earth and was traveling towards us a 9 miles/second. Fortunately, its orbit never brings it closer than about 16 times the Moon’s distance from planet Earth.

Since DH155 will come near the orbits of Mars in July,  Earth in September,  and Venus in October of 2018,  the asteroid hunting community will be keeping track of it to determine that its path is not changed to make it a threat. 

118E: Things That Dim In The Night

Objects in the Universe that brighten rapidly grab our attention. One of the most spectacular examples is Kepler’s supernova. In 1604 this star was bright enough to be seen with the naked eye in the daytime for over three weeks. Another occurred in 1843 when a comet became almost as bright as the limb of the Sun.  Over the centuries there have been many suddenly appearing objects in both the day and night sky. Possibly as the result of this history, most of the surveys which look for time variable objects in the sky are set to trigger on increases in brightness. 

Always one to think out of the box, Dr. Alice Quillen of the University of Rochester began to wonder if there are objects which dim in ways that will tell us about their natures.  She knew about eclipsing binary stars like Algol which dim on a regular basis and decided to look for other examples of things that dim instead of brighten.  She and her colleagues started by analyzing data on 40,000 calibration stars which were observed for about 4 years by the 2 Micron All Sky Survey.  They found a number new of members of known types of variables as well as some objects which are not easily characterized.  Although interesting, these results suggest that if one can apply a clever enough sorting tool to some large data bases which exist some exotic objects may pop out.  

The holy grail of this effort will be to find young stars and associated planets which have disks of material surrounding them.  The results will help us to find and understand  planetary systems in formation. 

Fortunately our atmosphere protects us from space rocks and harmful radiation.

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

End of podcast:

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