On the Motion of the Moon in the Margaret Wise Brown Classic "Goodnight Moon"

Please observe the following composite image, taken from several different exposures of the moon.

It is clear from the non-linear motion of the moon across the sky that the orbit of the moon is not a simple ellipse. This is probably because the planet inhabited by the race of sentient bunny-like aliens (henceforth: Planet Bun) is probably in a non-stable multi-body system. It likely involves multiple other moons, planets, and potentially stars, although we can clearly see from the view out this window that the stars must all be opposite Planet Bun from the observer. The intense gravitational forces from the other unseen bodies of the system must steer the moon in a strange path, and not in an elliptical orbit around Planet Bun.

Also, based on the fact that the pattern of the  background stars changes so rapidly between each exposure, we can conclude that Planet Bun itself must be orbiting or rotating at a very high velocity. In fact, the "moon" may not be a satellite of Planet Bun at all. It could very well be a double planet or, judging by the lack of surface features, a white dwarf star that Planet Bun itself is orbiting. In fact, judging by just how quickly Planet Bun's view of the background stars changes, it may be quite likely that the "moon" is in fact a neutron star, which Planet Bun orbits in hours or minutes. The orbital distance is likely quite close in order for a small star to have such a high angular diameter.

Note also how the apparent motion of the "moon"-like neutron star speeds up between the fixed-interval exposures. This is likely because Planet Bun is in a highly-elliptical orbit and it is approaching perigee, causing the vast orbital speed increase.

Happy first day of Spring!

At 11:44 am UT this morning, (4:44 if you're in California, 6:44 if you're in Chicago or Texas, 7:44 if you're in Virginia, Florida, or Ohio), the Earth crossed that mystical point in space such that the Sun crossed the celestial equator as seen from Earth. This denoted that the Sun is now "in" the Northern Hemisphere and marks the first day of Spring.

What is particularly interesting is that, had the Sun crossed the celestial equator just sixteen minutes later, you could have "drawn" a perfectly straight line through the center of the earth, the intersection of the Prime Meridian and equator, the center of the Sun, and the intersection of zero hours right ascension and 0° declination on the celestial sphere.

While the Prime Meridian and equator of the Earth coincide with the celestial Prime Meridian and Equator once every 23 hours and 56 minutes (or about 366 times a year), the 

celestial prime meridian is defined as the First Point of Ares or the vernal point, i.e., that point that the Sun occupies in the sky during the vernal equinox.

What this means is that at noon UT today, the Sun was directly above 0°N, 0°E, and was also at 0 hours right ascension and 0° declination. (The Sun, afterall, is a disk not a point, so while the exact center of the Sun was not directly overhead, part of the Sun was.)

In Celestial terms, this is what it looks like:

Notice how the Sun covers the intersection of the celestial Prime Meridian and equator.

Other interesting points:

While today is the equinox, it is not the day that day time and night time are equal. That was the equilux and occured several days ago (Tuesday, here in So Cal). The reason day and night are not the same length today is because the Sun's disk spans several arcminutes of the sky, and the Earth's atmosphere bends the sunlight around the curve of the Earth slightly. These two factors combine to make the day slightly longer than night.

Secondly, since the Sun is a disc, it actually takes it about 33 hours to completely cross the celestial equator. That means starting yesterday and going until sometime tomorrow, the Sun will be covering the vernal point.

Gravitationally Stable Three-Body System.



I've had this system running stably in Dave's Gravity Simulator for about two-and-a-half hours, with no end in sight. I have never seen a three-body system run so smoothly for so long, without any gravitational perturbations messing it up. The closest I did get was a three body system in which there were two planets orbiting in intersecting, counter-directional orbits for quite a long time, before one was perturbed enough to break orbit. What was interesting about that one was the two planets orbits were in 1:3 phase-resonance with each other, such that even though they were orbiting in opposite directions, and their orbits crossed, they never came very near to each other. This one, however, looks to be even more stable. I'm going to let it run overnight and check back in the morning.

--UPDATE 6/18 7:30am--

This is what I saw when I came in this morning.



It's actually not the same system. The number of starting planets is different (648 vs. 777). Also, this one has to have been running all night to rack up a score of 140,000. I was hoping that when I came in this morning, even if the system from yesterday evening wasn't running, the high score would at least indicate how much longer it had run. Unfortunately, this new system overwrote its high score. Crumb.

--Update 6/18 12:54pm--

The system just broke 200,000 points, and still isn't showing any signs of stopping. Further bulletins as events warrant.

--Update 6/18 4:33pm--

The system's at 240,000 points and still going. That means it's gaining about 100,000 points per nine hours, indicating it was running for about 13 hours or so before I got in this morning. I'll leave it overnight and see what happens.

--Update 6/19 8:03am--

The system died sometime last night shortly after I left. I got in and found a new system running, at 120,000 points. The final score for yesterday's was 268,911.

--Update 6/20 2:56pm--

The system that started night before last is still running, with over 400,000 points. I'm going to let it run over the weekend and see what happens.

The Quiz: Planets Edition.

For the purposes of this quiz, I will be using the IAU definition of planet. Sorry, but Pluto is not considered, primarily because in questions of "least", "most", "greatest", and "smallest", it's more interesting if the objects in question share very similar characteristics. So the EIGHT planets that are valid answers for this quiz are (alphabetically) Earth, Jupiter, Mars, Mercury, Neptune, Saturn, Uranus, and Venus.

As with other quizzes, the numbers pre- and post-slash refer to the number of points you gain/lose for correct/incorrect answers. Answers are written after the questions. Highlight to read.

All answers are taken from Wikipedia. You got a problem wit dat, take it up wit dem. Also NO CHEATING!

Section I: "Duh... Venus shore is a bright star. Duh...."
What planet is furthest from the sun? (1/-10)
Neptune (30 AU; ≈4.5 billion km)
What is the largest planet? (1/-10)
Jupiter (radius: 71,000 km; surface area: 64 billion km²; volume: 1.4e15 km³; mass: 1.9e27 kg)
What is the smallest planet? (1/-10)
Mercury (2439 km radius)
What planet has the highest orbital velocity? (2/-10)
Mercury (47.87 km/s. Duh, this follows naturally from it being closest to the Sun)
Which planet is closest to Earth-sized? (2/-8)
Venus (0.95 Earth radii)
Which planet achieves the closest proximity to Earth? (3/-8)
Venus (≈40 million km)
How many planets are superior to Earth? (3/-7)
Five (superior refers to having an orbit larger than Earth's)
How many planets transit the Sun, as seen from Earth? (3/-6)
Two (Mercury and Venus). This follows naturally from them being the only inferior planets.
Which planet has the lowest non-zero number of moons? (3/-6)
Earth (1; duh)

Section II: "I know a thing or two about heavenly bodies."
Which planet has the most moons? (5/-3)
Jupiter (currently; give yourself 3 points if you said Saturn)
How many is that? (10/0)
63 (again, currently known)
How many planets have "significant" atmospheres (>1 millibar surface pressure)? (5/-3)
Seven (all except Mercury)
Which planet has the longest day? (5/-5)
Venus (243 days)
Shortest day? (8/0)
Jupiter (0.41 days)
Which planet has the highest axial tilt? (5/-5)
Uranus (97°)
Lowest axial tilt? (6/0)
Mercury (0°)
The tallest active volcano in the solar system is on which planet? (5/-2)
Mars (Olympus Mons; 88,580 feet)
Which planet has the lowest density? (5/-2)
Saturn (70% that of water)
Which planet has the highest density? (6/-1)
Earth (550% that of water)
Second highest? (7/0)
Mercury (543% that of water)

Section III: "Ok, but not that much."
Which planet has the highest mean surface temperature? (5/0)
Venus (730 K)
How many planets have rings? (7/-2)
Four
Name them (x² where x is the number you got right):
Jupiter, Saturn, Uranus, Neptune
Which planet has the highest degree of flattening (relative difference between polar radius and equatorial radius)? (7/0)
Saturn (0.0976)
Which planet has the most eccentric orbit (most elliptical)? (8/-2) See? This is why we can't invite Pluto to parties!
Mercury (0.206)
Least eccentric (most circular)? (9/0)
Venus (0.00677)
Which planet has the lowest equatorial surface gravity? (8/0)
Mars (Ha! Bet you didn't know that!) 3.69 m/s² (compared with Mercury, 3.7 m/s²)
Which planet's equatorial surface gravity is closest to that of Earth? (10/0)
Saturn (8.96 m/s², or .914g)
Which planet has the strongest magnetosphere? (9/0)
Jupiter
Which two planets have highly unusual magnetospheres, in that their magnetic poles are tilted at extreme angles from their axes of rotation, and the magnetic center is highly offset from the planetary center? (10/0)
Uranus and Neptune

Bonus Questions: "Buh?"
What planet has the highest planetary discriminant (clearest orbit)? (15/0)
Earth (1.7e6)
What planet has the lowest planetary discriminant ("dirtiest" orbit)? (15/0)
Neptune (2.4e4) (Compare this to Pluto's value, 0.077)
When the IAU defined a planet as having "cleared its orbit", they didn't assign any value definition to what that meant, leaving it open to interpretation. However, we can try and quantify this by using the "planetary discriminant" which is, basically, the mass of the body in question, divided by the mass of all other objects which share that body's orbital zone, but are not dominated gravitationally by that body (such as moons) nor in orbital resonance with the body (such as trojans). Using this method, it is plainly visible that the clearest Dwarf Planet's orbit (Pluto's) is six orders of magnitude less "cleared" than the "dirtiest" planet's. So even by the vague terminology of "cleared its orbit", it's very easy to say that the eight planets conform to that terminology and Pluto does not.

Scoring:
(-∞, -100): Boy, you suck at both Astronomy and Math.
[-100, -50): Unga. Grok see if rocks edible. Grok like looking at shiny dots in sky. Unga.
[-50, 0): You're probably in favor of burning those who say the Earth revolves around the Sun at the stake.
[0, 50): Tycho Brahe
[50, 100): Galileo Galilei (heretic)
[100, 150): Edwin Hubble
[150, 175]: Johannes Kepler
(175, ∞): Nicolaus Copernicus
(205, ∞): You're either really good at astronomy, or you suck at math, probably both.

Eclipse Pictures

Fortunately, the weather here was perfectly clear. Unfortunately, it was 10 degrees, so I just ran out every 45 minutes or so, snapped a bunch of pictures, and ran back in. I don't remember the last time I got such a good view of a lunar eclipse. I took these from the street outside my fiancee's apartment. Sorry for the generally low quality - I was missing part of my tripod so these are all hand-held.

The very start of the eclipse:
















Halfway to totality, the curve of the Earth's shadow is easy to see, along with with the coloration of the light deflected through the atmosphere:















During totality. No tripod = ISO 800 = grainy. The Moon was very dark at this point.















Totality with Saturn to the lower left and Regulus above:




















Post-totality.

















The pictures don't really capture how beautiful it was to watch. Sorry you missed it Joe, there's always 2010. I'm sure you can find plenty of good pictures of it on the net.

Oh no! The moon is being swallowed by a dragon! 'Tis the end of the— oh, never mind.

http://www.reuters.com/article/scienceNews/idUSL2028499420080221

Did anyone get any pictures of the eclipse last night? It was completely overcast here. Stoopid one-day-of-rain-a-year has to fall on eclipse night.

All I can say is NASA better hurry up and get their Lunar base up and running, because I want to see picture of an eclipse as seen from the moon.

Astronomy Picture of the Day/Week/Month.

From Space.com

<<The Moon passes less than a degree from very bright Mars. In fact, observers in northern Canada, Alaska, the Arctic and parts of Europe may see an occultation (basically, an eclipse) of Mars by the Moon. For a map and more information on the occultation, see the International Occultation Timing Association page: http://www.lunar-occultations.com/iota/planets/1224mars.htm>>



I took that picture a couple hours after the closest approach. It should be noted that It would have missed the event altogether if The Observant Murloc hadn't noticed it as we were driving home from mass.

In a little more cosmic terms, it would look something like this.



(Screenshot courtesy Celestia. What? You don't have Celestia? Go get it now!)

It's interesting to note that any picture with an exposure long enough to capture Mars automatically means the Moon is whited out. If you want a picture of the Moon, here's one.



Note that was taken without the aid of a tripod at a 1/1600" shutter speed.

Too cool not to link to.

An Atlas of The Universe

But, of course, I have to balance it out with something completely inane and idiotic.

Cabotia