Astronomy Picture of the Day -- Fly Me to the Moons

NASA ^ | February 25, 2013 | (see photo credit)

[SunkenCiv]

Explanation: Sometimes the Moon is a busy direction. Last week, for example, our very Moon passed in front of the planet Jupiter. While capturing this unusual spectacle from New South Wales, Australia, a quick-thinking astrophotographer realized that a nearby plane might itself pass in front of the Moon, and so quickly reset his camera to take a continuous series of short duration shots. As hoped, for a brief instant, that airplane, the Moon, and Jupiter were all visible in a single exposure, which is shown above. But the project was not complete -- a longer exposure was then taken to bring up three of the Jupiter's own moons: Io, Calisto, and Europa (from left to right). Unfortunately, this triple spectacle soon disappeared. Less than a second later, the plane flew away from the Moon. A few seconds after that, the Moon moved to cover all of Jupiter. A few minutes after that, Jupiter reappeared on the other side of the Moon, and even a few minutes after that the Moon moved completely away from Jupiter. Although hard to catch, planes cross in front of the Moon quite frequently, but the Moon won't eclipse Jupiter again for another three years.

[SunkenCiv]

[Credit & Copyright: Greg Gibbs]

[SunkenCiv]

Reader Challenge: Hard: What type of airplane is this? Really hard: What was the flight number?

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[no-to-illegals]

Thanks SunkenCiv. and I'll never miss anything following.

[houeto]

Fantastic! Thank you SunkenCiv.

[TheOldLady]

That’s wonderful! It’s worth the trip to go to the APOD and click on the picture to get the enlarged version. It’s easy to see the moons of Jupiter and the details on our moon.

Thanks again (and again!) Mr. Civilizations.

[Lonesome in Massachussets]

The definition of the second is directly linked to motion of the moon. Canadian-American astronomer Simon Newcomb found records in the Paris Observatory of 18th century observations of the moon occulting ( the right word, not eclipsing) bright stars and was able to work out an accurate theory of lunar motion. Later astronomers built on his work. In 1958, the British National Physics Laboratory built the first atomic clocks. Working with their colleagues at the U.S. Naval Observatory in Washington DC, and using the then novel technique of satellite time transfer, they compared the ticks of the atomic clock to the motion of the moon as it occulted bright stars, and used lunar ephemerides to calibrate the Caesium (it was British, after all) Atom to the motion of the moon, and by extension, to Ephemeris Time (ET), being able to compare time kept by the Caesium Atom to the length of tropical year 1900, by the known relationship of lunar motion to twists and turns of the apparent sun.