Look up at the sky Monday night to see a bright cosmic frown. The planets Jupiter and Venus will briefly align to form (nearly upside down) two eyes and a frowning mouth in the southwest.

In what's called a planetary conjunction, the two planets —the brightest in the night sky — will appear extremely close, separated by only the width of a finger held at arm's length. They won't be this close together and well-placed for evening viewing again until May 2013.

In fact, some astronomers think a similar alignment of the planets on June 17 in the year 2 BC is behind biblical accounts of the Star of

Bethlehem present during Christ's birth. The bright planets would have appeared so close together they could have been taken as a single shining star.

Though the three celestial objects will appear to be close together Monday night, they lie at drastically different distances from Earth. While the moon is only 252,000 miles away, Venus is 370 times farther away, at 94

million miles. And distant Jupiter lies nearly six times farther away than

Venus, at around 540 million miles.

The tables are turned when we think about the heavenly objects' relative size. While the moon appears as the largest of the three, it is really a tiny speck in space compared to the vast bulk of Venus, which is again dwarfed by Jupiter, the largest planet in the solar system. Jupiter's diameter is 40 times that of the moon.

Though Jupiter is much larger than Venus, it appears dimmer to us, because the latter planet is so much closer to Earth. Plus, Jupiter is much farther away from the sun than Venus, so the light bouncing off it is much less intense than the light bouncing off

Venus, which hasn't had to travel so far.

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Image: Sky and Telescope