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Another Successful Night Sky Network Telecon - Dr. Massimo Stiavelli


On Tuesday November 9, 2004, the Night Sky Network (an Astronomical Society of the Pacific program) held it's latest telecon. Astronomy club members were invited to listen to a talk by Dr. Massimo Stiavelli who discussed the Hubble Ultra Deep Field pictures and what they tell us about distant galaxies. His talk was less than 30 minutes long which left a long time for questions.

Some of the younger audience members had questions that I thought would fluster Dr. Stiavelli. For example, after his talk which included items like the extent of metallicity for galaxies with a redshift greater than 6, one questioner asked "What was the earth like before the big bang?". Dr. Stiavelli calmly answered that there was no earth at that time.

Dr. Stiavelli is working on the next generation telescope which is also called the James Webb Space Telescope. He gave the following facts on this scope which are compared to the Hubble Space Telescope below:
Mirror Size 6 m 2.4 m
Mirror Type Segmented One Piece
Mirror Coating Beryllium Aluminum+Magnesium Fluoride
Spectrum Range .6-28 microns .11-3 microns
Location L2 Earth Orbit
Sunshade Tennis Court Size Uses Earth Shadow
Lifetime 10 year goal 13 years so far

Other interesting points from this telecon:

* The Ultra Deep Field shows items down to the 31st magnitude. That roughly corresponds to a firefly at the same distance as the moon.

* The Ultra Deep Field required 1 million seconds of exposure time.

* That comes out to 42 minutes per orbit for 400 orbits.

* At some point, perhaps when the universe was 700 million years old, there had to be a reionization process.

* This reionization was facilitated with low metallicity stars because they can burn hotter. In the early universe there were only 7% as many stars as we see today and that suggests that metallicity in the universe was also about 7% of what it is today.

* We know that reionization had to occur because of the ionized hydrogen found in the spectra of quasars.

PowerPoint slides for this telecon are currently available at They may be moved elsewhere in the near future. The next telecon is not yet scheduled but you can get on the mailing list for future telecon announcements. E-mail Bob Havner.

The Night Sky Network, founded by the Jet Propulsion Laboratory's PlanetQuest program, is a nationwide coalition of astronomy clubs bringing the science and inspiration of NASA's missions to the public.


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