25 January 2007
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First snow last night . .
There across the morning bay Sudden mountain-white. Shiki |
It wasn't actually the first snow of the season, but was the first snow that has accumulated at all and lasted until morning while I have been here to see it.
We are supposed to see one to three inches of accumulation before the snow stops then the mercury is supposed to fall out of the bottom of the thermometer and the impellers spin off the anemometer this afternoon and tonight. It doesn’t look like we are going to get all that snow and what there is seems to be disappearing pretty fast. They are talking about the coldest temperatures of the season again with wind chill temperatures down to -15°F.
I have been doing some reading in The Big Splat, Or How Our Moon Came to Be and they talked about the density of the planets being controlled by their distance from the Sun at their time of formation so I prepared this chart to compare all of the current known planets and the Moon based on numbers from Wikipedia. I used the semi-major axis of the planet's orbit for the distance since we don't know exactly where they were when they formed and it was the one number that was available for all planets. There is no estimate of Eris’ density so a used a value consistent with the density of the other dwarf planets.
Look at how far Eris is from everything else.
I have been reading this book to learn about crater formation on the Moon. Here is what Dana Mackenzie has to say about high speed impacts:
. . . the only collisions we ever see in everyday life are low-speed impacts. Throwing a rock on the ground; dropping it from a tall building; even firing a bullet into the ground, as Gilbert did in some experiments - these are all low-speed collisions. The bullet may gouge a big hole, but the bullet remains basically intact; it doesn't explode. It transfers momentum to the soil, but not a lot of energy.A High-speed impact, on the other hand, is much more like an explosion than a collision. The 63,000-ton stone that plowed into the Arizona plain fifty thousand years ago was moving at more than forty thousand miles per hour -- fifty times faster than a speeding bullet. At that speed it contained ten times more energy per pound than a stick of dynamite. When the energy was released, the stone exploded. That is why no large body of iron was ever found underneath Meteor Crater, and only a few beach-ball-size fragments were found outside of it. The vast majority of the impactor had simply been vaporized.
Until 1945 it was impossible for humans to conceive of such an explosion. But now we can. Think of Hiroshima -- only bigger. Like a nuclear bomb, the explosion would first produce a blinding spherical shock wave, then a mushroom cloud. The shock wave is what does most of the damage. It travels down into the ground as well as up into the air, subjecting the rock to immense pressure. It isn't really accurate to think of the meteorite "digging" a crater, instead, it compresses, fractures, pulverizes, and even melts the rock, and launches it in all directions. On the Moon (though not on Earth) it is easy to spot secondary craters that were created by material ejected from larger impact craters.
The planet takes a long time to rebound from the violence of the impact. Over time the crater gets shallower, because the weight that has been pressing down on the rock at the bottom of the crater has been removed. Physicists call this an "isostatic adjustment"; it has nothing to do with erosion, and this it can happen just as well on the Moon as on Earth. This explains why so many of the Moon's craters are very flat-bottomed.
Baldwin also explained why lunar craters are round, a fact that had puzzled Gilbert. Gilbert thought that a meteorite could create a circular crater only if it came in along a nearly vertical trajectory. An oblique or glancing impact would, he assumed, create a more elongated crater. Yet stretched-out craters are very rare on the Moon. The resolution of this paradox, Baldwin showed, is again that we are accustomed to impacts where the colliding bodies remain intact. A meteorite impact is first and foremost an explosion, and the shock wave produced by an explosion is symmetric. So the crater will be circular as well.
NASA has announced its target date for the next Space Shuttle launch. They are shooting for just before sunrise on the first day of the launch window which runs from 15-29Mar07. This will get the Shuttle up here during civil twilight. For each day they delay the launch it will get earlier and the skies will be darker here making it easier for us to see.
| 0536 EDT | Astronomical Twilight Begins |
| 0609 EDT | Nautical Twilight Begins |
| 0640 EDT | Civil Twilight Begins |
| 0643 EDT | STS-117 Launch |
| 0651 EST | STS-117 Cloasest Approach to NYC |
| 0708 EST | Sunrise |
For every day the launch is delayed the launch time will advance about 23 minutes. It should be about Mag -2.
CalSky is indicating that there will be early morning visible ISS passes during the launch window so we should also have a chance to see the ISS and STS-117 flying in tandem.
And in another long range planning, NASA has announced that it will be crashing a rocket into the Moon near one of the poles as part of the Lunar CRater Observation and Sensing Satellite (LCROSS) mission. The rocket is supposed to be launched sometime in 2008 but no date is given and they don't indicate how long it will be after launch before the impact. But amateur astronomers are supposed to be able to see dust from the impact when it does occur. It will be timed so that it will be observable from the Pacific, the continental US and Europe.
| Observing Location | Metropolitan Ave and McGraw Ave, Bronx, NY | ||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Observational Period | 2130-2145 EST | ||||||||||||||
| Atmospheric Conditions |
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| Instruments | Naked-eye Observing - Charlie | ||||||||||||||
| Observing Party | Charlie Ridgway |
There was supposed to have been a two-hour period of very poor transparency (or clouds so thick CSC couldn't predict transparency (but I guess I missed it because there was no ring around the Moon and I could are Orion just above the fluorescent-lit subway station. I saw one star to the N tonight.
I saw a few more stars tonight than I did last night.
- Below Saturn were Regulus, Algeiba, and Zosma.
- I know I saw Procyon and thought I saw something to its right which I thought would have been Gomesia but that star would have been above Procyon. There is nothing else in the neighborhood and the only thing I can figure is that at that time I was looking at Sirius and Mirzim.
- In Orion I added Saiph to Rigel, Betelgeuse, Belatrix Alnitak, Albulam and Mintaka.
- I saw one star to the north that appeared a little orange. Dubhe is the brightest star in that part of the sky and is indicated to be a red star in Planetarium so I suspect that is what I was seeing.
After having set record high temperatures multiple times this winter, now they are saying that we will have abnormally cold weather tomorrow and may set a low temperature record.
posted by Charlie at 14:03
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