The rings of Uranus turn the edge towards us

Once every 42 years the angle between Uranus and the Earth aligns so that we see the rim of the rings

Photo: NASA and the European Space Agency

Once every 42 years the angle between Uranus and the Earth aligns so that we see the rim of the rings. Because the rings were only discovered in 1977, this is the first time astronomers can see the planet without the interfering glow and dust of the rings. The event does not occur on a specific date but in a more complex process.

Due to Earth's much faster orbit than distant Uranus, there are actually three times when Uranus and Earth align perfectly - May 3 and August 16, 2007, and February 20, 2008. Unfortunately, during the next alignment - in February the Sun will line up directly between us and Uranus so we could not see Uranus.

The first to photograph Uranus during the special occasion this time were astronomers from the University of California at Berkeley. They imaged Uranus on May 28 with a near-infrared camera that also contains equipment for corrective optics, using the KEC 2 telescope on Mauna Kea in Hawaii. Their images revealed the ring almost on edge appearing as a bright line out to the right of Uranus.

The next shot was from the Hubble telescope, on August 14. Hubble took his pictures at almost the exact moment the rings aligned with Earth, showing features similar to those in Keck's photo, and he also revealed some of the outer rings that were only recently discovered. The outermost ring, observed by Hubble, is very difficult to detect in infrared light.

Astronomers hope these images will reveal more details about the moons that help organize the Cordelia and Ophelia rings in place. But there may be other moons around that help keep all nine rings in shape. The precise geometry may allow telescopes to reveal the moons that are normally lost in the glow of the rings.

Dec. 7 will be the equinox on Uranus, when the rings will be precisely aligned with the sun, and then there will be a short period when we will see the dark side of the rings, before they will light up again for another 42 years, says Heidi Hamel of the Space Science Institute in Boulder, Colorado.
For information on the Universe Today website