A plane? A UFO? No, it's probably Venus.
Posted October 9, 2007
We’ve been on an amazing clear sky streak for our past few monthly skywatching sessions. Let’s hope the streak stays alive for this weekend’s Saturday, October 13, 7:00-9:00 p.m. session. As usual, we’ll be at Jordan Lake’s Ebenezer Church Recreation Area. Please visit the Morehead skywatching webpage for directions.
Everyone has seen it – a curiously bright object in the sky. Maybe it looks like a plane making its approach for landing at RDU, but it doesn’t have blinking lights. You stare at it for a few moments, but it does not seem to move. What could this thing be?
You are probably seeing a bright star or planet, and the #1 candidate is usually Venus. Reported “UFO sightings” go through the roof whenever Venus is at a good, visible position in the sky. In fact, our former president Jimmy Carter, while he was governer of Georgia, once reported a UFO sighting that was actually Venus!
For the next few months, you can see Venus low in the eastern sky just before Sunrise.
Venus is the third brightest object in the sky, behind only the Sun and the Moon. It is very bright for a few reasons:
a) Venus is relatively close to Earth. It is the 2nd planet from the Sun, and Earth is the 3rd. Depending on where the two planets are in their orbits, the distance between them can be as little as 24 million miles, or as much as 160 million miles. For comparison, Mars, the 4th planet from the Sun, never gets closer than about 35 million miles away from Earth, and is often over 200 million miles away.
b) Venus has a thick, cloudy atmosphere that is highly reflective. It reflects over half of the visible light that it receives from the Sun.
c) Venus is large compared to the two other inner planets, Mercury and Mars.
Venus’s location in our sky depends on its location relative to the Sun. Sometimes Earth, Venus, and the Sun all get nearly lined up – when this happens, we won’t see Venus for months because it is lost in the glare of the Sun.
Other times, we can see Venus for months at a time to the east or west of the Sun. When Venus is to the east of the Sun, we see it after Sunset, low the in western sky. When it is to the west of the Sun, we see it before Sunrise, low in the Eastern sky. The latter is the position that Venus will be in for the next few months, until it is lost in the Sun’s glare beginning in mid-February of 2008.
From our latitude here in North Carolina (or anywhere in the continental US), you will never see Venus late at night (anytime between about 10 p.m. and 3 a.m.). During this period each night, your location on Earth is facing away from the Sun and Venus. To see Venus, we always have to look in general direction of the Sun – that’s why we only see it in the couple of hours before Sunrise, or after Sunset.
One more cool thing about Venus: it goes through phases, just like our Moon. As it orbits the Sun, we see different portions of its lit side. Sometimes we see only a small crescent of Venus’s lit side, but thanks to its close proximity and cloudy, reflective atmosphere, it remains extremely bright in our sky.