Podcaster: Dr. Al Grauer
Title: Travelers in the Night Eps. 129E & 130E: Sailing The Cosmos & Planetary Defense
Organization: Travelers in The Night
Description: Today’s 2 topics:
- The Planetary Society has initiated and funded the LightSail. It is a loaf of bread sized spacecraft which will hitch a ride aboard a rocket being launched on another mission.
- In 2015 people from all over the world met in Italy to discuss ways that humans can prepare for the unlikely, but not impossible, situation that an object is on an impact trajectory with planet Earth. They were were presented with a hypothetical asteroid threat.
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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129E: Sailing the Cosmos
The first human use of the wind to power boats most likely occurred in about 3,000 BC. This was a major improvement in travel over walking and animal drawn carts.
About 400 years ago the German astronomer, Johannes Kepler, observed that Comet tails were being moved by what he thought might be a Solar breeze. He suggested that this phenomena could be used to power ships through space. In 1873 James Clerk Maxwell demonstrated that photons from the Sun exert a small force as they bounce off of a reflective surface. Recently the Kepler Space Craft began to use this tiny light pressure to maintain its orientation after the 2nd of its 4 stabilizing gyroscopes failed.
The Planetary Society has initiated and funded the LightSail It is a loaf of bread sized spacecraft which will hitch a ride aboard a rocket being launched on another mission. Once in orbit this tiny spacecraft will deploy a 4 panel solar sail which is about 5.5 meters on a side.
Three or four hundred years from now humans may send a robotic space probe to a nearby star using a light sail as big as the state of Texas. Ideally it would deploy its giant solar sail near the Sun perhaps as close to it as the planet Mercury. This would give it maximum initial thrust. After it gets far from the Sun it could be pushed along by a powerful pinpoint laser beam. Theoretically it is possible to achieve a fraction of the speed of light through this means.
130E: Planetary Defense
Recently people from all over the world met in Italy to discuss ways that humans can prepare for the unlikely, but not impossible, situation that an object is on an impact trajectory with planet Earth. They were were presented with a hypothetical asteroid threat.
On the day of its discovery the hypothetical asteroid is a faint moving point in the night sky. A few days of observation provides it with a tentative orbit and it is given the name 2015 PDC. It is the smallest of the Potentially Hazardous Asteroids with a diameter between 100 and 500 meters. As observations of its path in the sky continue, it appears to have a tiny increasing chance of impacting Earth. If it did it would be traveling at 7 miles/second and pack the energy several times greater than the most powerful hydrogen bomb ever exploded. As with all real asteroids this hypothetical object’s size and composition are not known with any degree of precision.
A month after its discovery the hypothetical asteroid comes about 18 million miles from us . It continues to be observed for another month with every new observation making it appear to have a greater chance of colliding with mother Earth about 7 years hence. This is where the participants are left. At this point they don’t know its exact size, chemical composition, if it will collide with us or not, and if it does the spot of impact on Earth. They are then charged with the task of obtaining needed observations and to develop a strategy to deal with the potential impact.
For Travelers in the Night this is Dr. Al Grauer.
End of podcast:
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