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Friday, September 14, 2007

Venus has been rising ever higher and has been getting a little brighter

Spot the Morning Beacon

When September opened, this resplendent Morning Star was rising just after dawn's first glow at around 5 a.m. local daylight time. But with each passing morning, Venus has been rising ever higher and has been getting a little brighter.

It will attain its greatest brilliance on Sept. 23, appearing at an eye-popping magnitude of -4.6. This is 19 times as bright as the brightest star in the sky, Sirius (in Canis Major, the Big Dog), and 10 times as bright as the next-brightest planet, Jupiter. (On this astronomers' scale, smaller numbers represent brighter objects, with negative numbers reserved for the brightest of all.)

See it during the day

Try looking for Venus through the brilliance of the daytime sky. It can be done if you know exactly where to look. Those who live in rural areas far from any extraneous light have reported that Venus can cast a faint, yet distinct shadow.

Probably the best method is to simply keep it in view until after the sun comes up. At its current extreme brightness, it can often be perceived as a tiny white speck against the blue backdrop of daylight.

And by month's end, it's rising at around 3:30 a.m. and will precede the sun by some three and a half hours.

Venus was at inferior conjunction on Aug. 18, in line between the Earth and the sun. Now it is swinging away from that line, speeding ahead of the Earth in its faster orbit. So in a telescope during September, it displays a large, brilliant, beautiful crescent that waxes in phase all month while shrinking in size.
When September opened, Venus was only 8-percent illuminated, but by month's end, that figure will have increased to 33 percent. But because it will have receded 16 million miles from Earth, the planet will appear more than one-third smaller than it did at the start of the month.
Magical telescopes

Thoughts of viewing the crescent of Venus reminds me of an amusing story related by George Lovi (1939-1993), a well-known astronomy lecturer and author who was also a good friend of mine.
One night, while running a public night at the Brooklyn College Observatory in New York, the telescope was pointed right at Venus which was then displaying its delicate crescent shape. Yet one student gazing through the telescope eyepiece stubbornly insisted he was not looking at Venus, but at the moon instead. When George commented that the moon wasn't even in the sky, the student replied, "So what? Doesn't a telescope show you things you can't see without it?"
During the coming weeks, Venus will also be floating ever closer to the bright star, Regulus and the planet Saturn, its evening partners from July. By the end of this month, Venus and Regulus will be separated by about 7 degrees and Venus and Saturn by 10 degrees (your clenched fist held at arm's length measures roughly ten degrees in width).

Come early in October, this trio - and a lovely crescent moon - will make for some eye-catching configurations in our predawn sky.

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