The widest swings happen when the Moon is at the 3 o'clock and 9 o'clock positions.
#Download nasa picture of the day full
In the full animation, watch both the orbit and the "gyroscope" Moon in the lower left. The tilt of the Earth is important for understanding why the north pole of the Moon seems to swing back and forth.
The north pole of the Earth is tilted 23.5 degrees toward the 12 o'clock position at the top of the image. This direction serves as the zero point for both ecliptic longitude and right ascension. You can check this by freezing the animation at around the 1:03 mark, or by freezing the full animation with the time stamp near March 20. The Sun is in this direction at the March equinox. The First Point of Aries is at the 3 o'clock position in the image. First and Third Quarter Moon occur when the Moon is along the day-night line on the Earth. The Moon is full when its orbit places it in the middle of the night side of the Earth. (There is also a south-up version of this page.)įrom this birdseye view, it's somewhat easier to see that the phases of the Moon are an effect of the changing angles of the Sun, Moon and Earth. The descriptions of the print resolution stills also assume a northern hemisphere orientation. The third quarter Moon is often surprisingly conspicuous in the daylit western sky long after sunrise.Ĭelestial north is up in these images, corresponding to the view from the northern hemisphere. The full Moon rises at sunset and is high in the sky at midnight. By first quarter, the Moon is high in the sky at sunset and sets around midnight. The cycle begins with the waxing (growing) crescent Moon visible in the west just after sunset. The most noticed monthly variation in the Moon's appearance is the cycle of phases, caused by the changing angle of the Sun as the Moon orbits the Earth. The two extremes, called perigee (near) and apogee (far), differ by as much as 14%. The Moon also approaches and recedes from us, appearing to grow and shrink. The roll angle is given by the position angle of the axis, which is the angle of the Moon's north pole relative to celestial north. It appears to roll back and forth around the sub-Earth point. The Moon is subject to other motions as well. The sub-Earth point is also the apparent center of the Moon's disk and the location on the Moon where the Earth is directly overhead. The sub-Earth point gives the amount of libration in longitude and latitude. The word comes from the Latin for "balance scale" (as does the name of the zodiac constellation Libra) and refers to the way such a scale tips up and down on alternating sides.
When a month is compressed into 24 seconds, as it is in this animation, our changing view of the Moon makes it look like it's wobbling. Because of the tilt and shape of its orbit, we see the Moon from slightly different angles over the course of a month. The Moon always keeps the same face to us, but not exactly the same face. The pummeled, craggy landscape thrown into high relief at the terminator would be impossible to recreate in the computer without global terrain maps like those from LRO. This is especially evident in the long shadows cast near the terminator, or day-night line. Its laser altimeter ( LOLA) and camera ( LROC) are recording the rugged, airless lunar terrain in exceptional detail, making it possible to visualize the Moon with unprecedented fidelity. Lunar Reconnaissance Orbiter ( LRO) has been in orbit around the Moon since the summer of 2009. Until the end of 2022, the initial Dial-A-Moon image will be the frame from this animation for the current hour. The animation archived on this page shows the geocentric phase, libration, position angle of the axis, and apparent diameter of the Moon throughout the year 2022, at hourly intervals. The data in the table for the entire year can be downloaded as a JSON file or as a text file.
#Download nasa picture of the day download
Hover over the image to reveal the animation frame number, which can be used to locate and download the corresponding frame from any of the animations on this page, including unlabeled high-resolution Moon images. Click on the image to download a high-resolution version with feature labels and additional graphics.