Tunguska Blast is 100 years old today June 30, 2008
Posted by jcconwell in Asteroid, Astronomy.Tags: comet, meteor, Tunguska
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On June 30th, 1908 a giant blast near the Podkamennaya Tunguska river leveled some 500,000 acres of forest, over 2000 square kilometers. The blast was originally estimated to be between 10 to 20 Megatons of TNT, 1000 times more powerful than the Hiroshima bomb, about the size of the largest H bomb in the world’s arsenals.
Because of the remote location, the political upheaval of the first world war and the Russian revolution, the first expedition did not reach the area until 1927. A blast area of radius 15miles, with felled trees pointing away from the center of impact was found , but no crater.
The lack of a crater has lead to the theory that an airburst of either a comet or meteor at an altitude of approximately 5 miles caused the destruction. The exact nature of the body whether comet or meteor is still a matter of debate. The excess amount of nickel and iridium in trees, both common in meteors, favors a rocky or iron meteorite. Also the number of Earth crossing asteroids is far larger than the number of comets. This has lead most scientists to favor the meteor rather than the comet being the impact object. The debate however is not settled.
Looking through the telescope the wrong way. June 27, 2008
Posted by jcconwell in Observatory, telescopes.Tags: Add new tag, EIU, Observatory
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Living in East-central Illinois means that when people visit the EIU observatory you have to contend with weather. At night, about half the time, it will be cloud covered and you just get to look at the telescope. If you come in the day its even worse. We can actual still see the football stadium light that are about 3000 feet away in the day.
On these occasions one of the things that I do is to lower the telescope and let people look down the tube and see the 16″ mirror, which acts like a really BIG makeup mirror. Since I have a Schmidt-Cassegrain telescope, with a front corrector plate, one of the thing people comment on is how DIRTY the front plate looks.
Don’t I ever CLEAN it!!!…….
Nope…. well not quite as often as you might think I should… and there’s a reason.
Most telescope lenses , and camera lenses, come with an anti-reflection coating, typically a coating of MgFl. You can tell when you look at it because it gives the lens a slight purple, or sometimes yellow color. The coating is put there to increase the transmission of light, to the eye or camera, by using the wave properties of light to eliminate reflection.
The coating is very thin, quite delicate, and can be easily scratched, and is expensive. Our 16″ telescope cost about $500 to get it recoated. So cleaning it is a very big project … distilled water…lots of care and can take several hours to make sure the dust doesn’t scratch the coating when it’s removed.
Also, you don’t need to do it very often. Even on a very dusty lens the light is only cut by a few percent. The dust on the lens is so much closer than what your looking at, the dust is out of focus, so you don’t notice it with your eye. A digital CCD camera is more sensitive, especially if the dirt is not uniform. We can compensate for that by taking what is called a “flat field” briefly, this is a photo through the telescope of the dirt! This is then digitally subtracted from the from any photo! Electronically cleaning it up.
So the short answer is I don’t clean it often , cause it’s tricky and I don’t need to.
Observatory Up & Running June 27, 2008
Posted by jcconwell in Observatory, Uncategorized.Tags: EIU, Observatory
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My thanks to the EIU Electricians for last week finding and installing a new transformer to the observatory. Just in time for the open house tonight. It looks like cloud cover, but we always have people even in the middle of a thunderstorm. If you’ve never been at an observatory it’s almost as much fun looking at the telescope as through the telescope . Plus if your nice, you get to rotate the DOME!! Here is a couple pictures of the field after the wind storm. Including the tracker-trailer and porto-pottie near the dome. Both of which are now upright. Thanks to the people in physical plant.
Tours of the Observatory June 23, 2008
Posted by jcconwell in Astronomy, IYA 2009, Observatory.Tags: Add new tag, EIU, Observatory
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One of the missions of the observatory is our open houses. We are 180 south of Chicago and about 65% of our students are from that region. Many have never looked through any telescope, let alone one as big as our 16″ scope.
Some have never seen a star….
The light pollution is so bad they couldn’t. Now it’s not exactly high desert out here, or as I say “places where you grow corn are not the best places to grow telescopes”, but sometimes you have to bring the observatories to the people were they live. That’s a central roll for small observatories like the ones at Eastern. This afternoon I’ll have the board of trustees for EIU, tonight we’ll have my physics class, at the end of this week I’ll have the monthly open house for the general public. The we’ll switch out the eyepiece put in the spectrograph and see if we can get our first spectra of Epsilon Aurigae. We hope to bring in more than 2000 people to the observatory next year during the Interational Year of Astronomy.
Friday the 13 June 13, 2008
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Well.. we thought the observatory dogged the bullet during last weekend storms, but when I was there yesterday I found out a transformer blew on that segment of the campus. First estimate says a replacment won’t come for several weeks. We’ll see if we can’t improve that number. At least I’m not suffering alone, … my class is having their first test today.
Back to teaching, back to blogging, & a GREAT Video! June 10, 2008
Posted by jcconwell in Astronomy, IYA 2009, Observatory.add a comment
After two days of storms, with about 70mph wind, and power outages, I’m able to get back to blogging, and back to teaching. A few comments, Well I now know that the Pro-Dome engineers like most engineers over-design things. Rated at 70mph, surrounded by upturned trees, porta-potties that were blown 40 feet ( I sure hope no one was in there at the time), the EIU Observatory still stands! Congratulations to the students who put it together in 2004! I’ll try to add some picture of the dome and the surrounding chaos tomorrow. Until them let me introduce you to the trailer for the International Year of Astronomy. This was unveiled last week in St. Louis during the AAS meeting
Why is Phoenix different than the rovers June 5, 2008
Posted by jcconwell in Astronomy, planets.Tags: Mars, rover
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I was asked a few days ago why the Phoenix was important, since unlike the rovers it just sits there. Short answer “Can you digg it? “. It helps be able to dig!
Photo credit: NASA/JPL/University of Arizona/Texas A&M
This image shows a white layer uncovered in the first practice diggs with the scoop arm.
This mission is about water, that’s the chief reason why the polar region was chosen. Since the surface of Mars looks lacking in water, other than in this region. Looks however can be decieving, what lies below the suface may be quite different. Hence to need to do more than just scratch the surface. Or as stated on the mission web site
Objective 1: Study the History of Water in All its Phases
Objective 2: Search for Evidence of Habitable Zone and Assess the Biological Potential of the Ice-Soil Boundary
For more info go to: http://phoenix.lpl.arizona.edu/
On an amusing note. A person I met at a dinner of astro bloggers, in the AAS meeting in St . Louis, told me he had just seen the first conspirasy web site come out claiming the grooves in the soil were caused not by the scoop but by some alien animal.
I believe Yetis were mentioned.
Astronomical meetings June 3, 2008
Posted by jcconwell in Astronomy.Tags: IYA 2009
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One of the main guilty pleasures of a meeting like this is the ability for me to be a non-expert, to be a student again. My field of expertise is General Relativity… neutron stars, black hole. But I’m also in charge of the observatory at Eastern Illinois University. I’m always looking for things for my students to do….and that I can learn. One of the plenary talks was on the search for new planets around other stars by looking tor transits, where the planets pass in front of the star causing a dip in the brightness. Rare because the alignment of our eye has to be close to the plane of the planet’s orbit.
If you would form a sphere of distance observers around the sun and Jupiter only about .1% would see Jupiter pass in front of the sun. You have to search for a lot of planets (and get many false positives from eclipsing stars not eclipsing planets). This technique is new enough that in the next couple of years they will have around 100 new planets around other stars using it.
First blog! June 2, 2008
Posted by jcconwell in Astronomy, General.add a comment
I’m Blogging the American astronomical society meeting at St Louis. Thanks to Dr Pamela Gay for organizing the new media workshop on Sunday afternoon, getting many of us started.
EIU Astro 