Podcaster: Dr. Al Grauer
Title: Travelers in the Night Eps. 123E & 124E: Future Impact Possibilities & The Oceans of Ganymede
Organization: Travelers in The Night
Link : Travelers in the Night ; @Nmcanopus
Description: Today’s 2 topics:
- These three asteroids are some of the most recent objects to be listed on the NASA Sentry Risk Table.
- With a diameter of 3,267 miles Ganymede is the largest satellite in the solar system.
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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Transcript:
123E: Future Impact Possibilities
Recently, three asteroids were discovered which have very slight probabilities of impact with planet Earth between 2065 and 2117. My team, the Catalina Sky Survey found two of them and the Pan-STARRS group in Hawaii found the other one. These three asteroids are some of the most recent objects to be listed on the NASA Sentry Risk Table.
It should be emphasized that the orbit of a small solar system object is never known perfectly. Soon after discovery, an Earth approaching object’s orbit is poorly known, since at that point, we have observations which cover a very small part of its path around the Sun. This is why objects which initially seem to be a threat are soon removed from that category with additional observations.
When a new object is discovered the observations of it are sent to the Minor Planet Center where they are posted on a public website. Telescopes around the world observe it to refine its path in the sky. After several days the new object’s orbit is well enough known to allow us to keep track of it and an electronic publication is issued. Within an hour or two the NASA Sentry software system calculates the impact risk that this new object poses to planet Earth. If these preliminary calculations indicate a close passage is possible then a much more extensive set of calculations are performed to pin down possible impact dates over the next 100 years.
So far so good.
Maybe against the most incredible odds a small asteroid has our number on it.
Maybe we will find it tonight.
124E: The Oceans of Ganymede
Ganymede was discovered by Galileo Galilei using his new telescope in 1610. He observed it to be a faint point of light orbiting the planet Jupiter. This discovery along with 3 of Jupiter’s moons was the first instance of objects being observed to be orbiting another planet.
With a diameter of 3267 miles Ganymede (GAN’-ih-meed) is the largest satellite in the solar system. Surrounding its iron core are a sphere of rocky material and a thick layer of water and ice which extends to the surface of this small world. If Ganymede orbited the Sun instead of Jupiter it would be a planet in its own right.
For more than 40 years, Ganymede has been suspected to have some liquid water below its frozen icy surface. Recently the Hubble Space Telescope was used to study the auroras on Ganymede. These beautiful displays are similar to the northern and southern lights on Earth. These studies enabled scientists to use Ganymede’s magnetic field to probe beneath its icy shell. What they found is an ocean 60 miles deep covered by a layer of ice 95 miles thick. This salty ocean contains more liquid water than exists on the Earth’s surface.
Water is amazing stuff. Water ice floats on top of liquid water. This makes it possible for marine life on Earth to survive below a layer of ice which separates it from the hostile conditions in the air above.
Now that we know that Ganymede has a substantial salty ocean one has to wonder if some type of microbes might be living there.
For Travelers in the Night this is Dr. Al Grauer.
End of podcast:
365 Days of Astronomy
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