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The Michigan Meteor and possible meteorites January 17, 2018

Posted by aquillam in Astronomy, MichiganAstro.
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Last night a rather large meteor exploded over Michigan. Stories and video are all over social media. The American Meteor Society website was down for a while, but it’s back up now, and they have a map where you can see where everyone who saw it was, and the probable ground path.
This was a bolide, a very bright meteor that explodes or breaks up, and usually makes it into the lower atmosphere. That makes it more likely that fragments may have made it to the ground.  So if you happen to live or own property near the ground path, you might want to go look for some fragments.
Some things to know:
If you suspect you might have an impact site, TAKE PICTURES BEFORE YOU TOUCH ANYTHING. Then, put something down for scale, like a quarter, or a rock hammer, and take a few more pictures. Then and only then, should you pick up and examine the rocks.
The glow of the meteor is mostly from the air around it. That will make the surface hot, but, like fried ice cream or baked Alaska, the inside will still be the icy cold of outer space. If you find a molten ball of goo, or something that looks like it was recently a molten ball of goo, it’s not a meteorite. This is slag, not a meteorite.


This is slag, not a meteorite. http://meteorites.wustl.edu/id/slagq_gil.jpg

If it’s a fragment of last night’s meteor, it won’t have weathered yet, so it should have a thin fusion crust, which should be dark.


This cross section shows the crust is fairly thin. It is also relatively smooth, but with a crackle-finish like texture. http://www.meteorite-recon.com/home/meteorite-documentaries/meteorite-fusion-crust

It came in at an angle, and probably broke into smaller pieces. Small pieces make small craters, but the snow here is rather fluffy. If small meteorites hit deeper snow, they may actually melt holes through it, and you’ll find the meteor stuck to the bottom of an ice core. In shallow snow over solid ground, you’re probably looking for fairly small dark rocks in shallow oblong craters maybe up to 10 times wider than the rock. The crater size varies dramatically though.
Very large meteorites can be valuable. Meteorites from events that were documented and witnessed (like this one) can be valuable. But don’t expect to buy a car by selling a couple small meteorites on eBay. Maybe a nice dinner at a fancy restaurant for your family. If you think you have a meteorite and are considering donating or loaning it to science, I’d suggest starting with NASA’s “Watch the Skies” site.

August meteor showers  August 4, 2015

Posted by aquillam in Astronomy, MichiganAstro, Urban Observing.
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Although there are months with more meteor showers, and more productive meteor showers, August is known as the meteor shower month. That’s probably because being outside at 2 or 3 am in August depends mostly on whether or not you’re the kind of person who’s up at 2 or 3 AM, whereas being outside at 2 or 3 AM in November depends more on whether or not you have insomnia or have lost touch with reality. Even if you are the sort of person who is normally up at 2 or 3 AM, it’s a lot easier to convince yourself to go outside when it’s 60° than when it’s 6°. So let’s take a look at the August meteor showers.

First things first: what makes it a meteor shower? On a typical, average, non-meteor shower night, under dark skies you should expect to see six or seven meteors per hour. They’ll be spread randomly around the sky though, so it’s unusual for a single observer to see them all. Meteor showers occur when the meteors seem to come from a particular area of the sky, called the radiant. It usually also means more meteors, but the radiant is the important part. You’ll  generally see more meteors in the predawn sky since that’s when the sky overhead is facing the direction or his traveling. Think of it like when you’re driving in the car: more bugs hit the windshield then the side or back of the car.

The top diagram shows the time of day on Earth. The second diagram shows the direction Earth is traveling in its orbit. If you put those two together, you get the bottom diagram, showing that the part of Earth where it is both dark AND running into the meteors.

The top diagram shows the time of day on Earth. The second diagram shows the direction Earth is traveling in its orbit. If you put those two together, you get the bottom diagram, showing that the part of Earth where it is both dark AND running into the meteors.

The Perseids are of course the best-known meteor shower, and with good reason. With maximum rates reaching close to 100 in good years, it’s a reasonably active shower. Many of the meteors are also bright, so you can expect to see 10 or so even under moderately light polluted skies. They tend to be quick though, and don’t have persistent trains (they won’t leave a streak on the sky for a long time.) The number of meteors gradually builds from about mid July until the peak around the 12th or 13th, then drops dramatically right after the peak.  The show runs about two more weeks, gradually tapering off by about the 26th or 27th.

The 2015 peak should occur on August 13. The American meteor society (AMS) predicts a rate of about 50 to 75 meteors per hour. The radiant is actually circumpolar for most of the US & Canada, so anytime after midnight is worth going out, but it’ll be best around 3 – 5 AM, when the radiant is high in the northeast, and twilight hasn’t begun. Check the chart at the end for it’s location at 4 AM.

The Perseids aren’t the only show this month.

The Alpha Capricornids are a low rate shower, just around 5 an hour. However, it’s tendency to produce fireballs makes it worth watching for patient people. It peaked around July 29, but the difference between the peak and not peak is nearly insignificant. If you’re already out hunting early Perseids, you might as well find a spot where you can also see the southwest!

The Delta Aquariids  also peaked around July 29, but you’ll continue to see several of these every night until late August. These are faint, though, so avoid the waning moon nights, and find someplace dark. The radiant is pretty far south too, so the farther south you are, the better.

There are also a few other recognized meteor showers, but they have very low numbers. If you happen to have a clear night when you’ll be at a dark site, you should check out the weekly meteor outlook at the AMS. Also, if you happen to spot a fireball, you can help identify and track it by reporting it!

meteorShower (pdf)      meteorShower

The 2011 Geminid Meteor Shower – NASA Science December 13, 2011

Posted by aquillam in Astronomy, MichiganAstro, Science.
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The 2011 Geminid Meteor Shower – NASA Science.

The Geminids are usually one of the nicer meteor showers, but the cold of December makes them rather less popular than the famous Perseids.This year, a bright waning moon adds interference.

If you’re wiling to brave the cold and the Moon, and you have an iOS device, you can help NASA and other planetary scientists. Download the Meteor Counter app from the app store, and become a citizen scientist for the night.

More information on the app (including screen shots and instructions) are available at http://meteorcounter.com/