Slendor, crescent moon will illumninate two brightest planets

Space.com / Starry Night Software

Look to the southwest after sunset on Dec. 1 for a close conjunction between three bright solar system objects: the moon, Venus and Jupiter. If you have binoculars, you might even be able to fit all three of them in the field of view. Between now and then, you can see Jupiter and Venus getting closer together each evening.

Every once in a while, something will appear in the night sky that will attract the attention of even those who normally don’t bother looking up. It’s likely to be that way on Monday evening, Dec. 1.

A slender crescent moon, just 15 percent illuminated, will appear in very close proximityto the two brightest planets in our sky, Venus and Jupiter.

People who are unaware or have no advance notice will almost certainly wonder, as they cast a casual glance toward the moon on that night, what those two "large silvery stars" happen to be? Sometimes, such an occasion brings with it a sudden spike of phone calls to local planetariums, weather offices and even police precincts. Not a few of these calls excitedly inquire about "the UFOs" that are hovering in the vicinity of our natural satellite.

Keeping it all in perspective
Keep in mind that this head-turning display of three celestial objects crowded together will be merely an illusion of perspective: the moon will be only about 251,400 miles from Earth, while Venus is nearly 371 times farther away, at 93.2 million miles. Meanwhile, Jupiter is almost 2,150 times farther away than our natural satellite at 540.3 million miles.

Those using binoculars or a small telescope will certainly enjoy the almost three-dimensional aspect of the moon, but Venus will be rather disappointing appearing only as a brilliant blob of light, for right now, it’s a small, featureless gibbous disk.

That will change in the coming weeks, however, as Venus approaches Earth and the angle it makes between us and the Sun allows it to evolve into a "half-moon" phase in mid-January, and a lovely crescent phase of its own during the latter part of February and March.

Jupiter, on the other hand, is a far more pleasing sight with its relatively large disk, cloud bands and its retinue of bright Galilean satellites.

All four will be in view on Monday evening, with Callisto sitting alone on one side of Jupiter, Ganymede, Io and Europa will be on the other side. Io and Europa will in fact, appear very close to each other, separated by only about one-sixth the apparent width of Jupiter.

When Venus emerges, it will look like a brightening jewel on the slender lunar crescent. For virtually all of Europe, the Sun will have set by then, the exception being southern Portugal (including Lisbon).

Such favorable circumstances are quite rare for any given location. For example, the last time London was treated to such a favorably placed Venus occultation such was back on Oct. 7, 1961.

And after 2008, there will not be another similarly favorable Venus occultation for the United Kingdom until Jan. 10, 2032.

[via MSNBC] by Joe Rao

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