I receive many calls about “unidentified flying objects” or UFOs at my office. I’ve spent countless hours observing the night sky, and I’ve never seen anything I couldn’t identify. Just because something in the sky is unidentified doesn’t mean it’s unidentifiable.
During my years as director of the Kirkpatrick Planetarium, I have noticed a pattern. Whenever some bright object appears in the evening sky that wasn’t there a month ago, people suddenly think it’s odd. Apparently, it makes no difference that the same object was in the same location a year ago. People seem to have a short memory when it comes to astronomical objects.
The two most common causes for UFO calls I receive are visible in the evening sky this time of year, and I have already received numerous calls about them. The objects are the planet Venus and the star Sirius.
Normally, the brightest objects in the sky are, in this order: sun, our moon, Venus, Jupiter and Sirius. On rare occasions, a meteor can outshine Venus, and on even rarer occasions, a supernova can, also.
Venus orbits the sun inside Earth’s orbit. This means we may see it at some times on the far side of the sun where it will be 150 million miles away, at other times nearly between us and the sun, as close as 32 million miles. Venus is in the west after sunset and remains visible until 9:30 p.m., well after sunset. Like our moon, planets don’t make any light of their own, they only reflect sunlight. Venus is covered with bright clouds, so it reflects sunlight very efficiently. Venus reflects 65 percent of the sunlight striking it. Compare that to our moon, which reflects only 12 percent of the sunlight hitting it.
Not only is Venus the brightest star-like object in the night sky, it behaves differently than the stars. Remember the nursery rhyme “Twinkle, Twinkle Little Star?” That wasn’t called “Twinkle, Twinkle Little Planet” because planets don’t twinkle like stars. So, not only is Venus extremely bright, it shines with a steady glow, more akin to an airplane’s landing light. Since Venus moves at the same, slow rate as the stars, it can’t be mistaken for an airplane. Therefore, it must be a UFO.
OK, if you don’t know what it is, then by definition it becomes a UFO, at least to you. But that doesn’t make it an alien spacecraft. Go out tonight and look at Venus, often referred to as the “Evening Star.” It might be a surprising sight but perfectly natural.
Sirius causes UFO buzz for a different reason than Venus; it DOES twinkle, very dramatically. To understand why Sirius looks so different than other stars, you have to understand why stars twinkle.
Stars are much larger than planets. Our sun is 100 times wider than Earth. But the stars we see at night are so distant, they appear as a point of light with no size, even with the largest telescopes. In effect, the point of light we see from a nighttime star is just one ray of light hitting our eyes. As starlight travels through our atmosphere, it gets distorted. This is analogous to the shimmering effect you see over a road on hot summer days. Different patches of atmosphere with slightly different temperatures will bend starlight like a prism. This effect causes starlight to take a zigzag course to our eyes. From one moment to the next, we may see all the starlight hitting our eyes or just a fraction or even none. Hence the twinkle.
While planets are much smaller, they are much closer. Through even a small telescope, Venus and the other planets reveal a disk. There are many rays of light from a planet hitting your eye. Although the atmosphere will affect each ray, all the other rays average out the effect, so planets shine with a steady glow. However, Sirius is so bright, a factor of our physiology comes into play. Our eyes contain two types of light receptor cells, rods and cones. Cones detect color, but rods only work at low light levels, and they are colorblind. Rods perceive only shades of gray. Most stars are too dim to register in our cones. Sirius is so bright, the cones detect it as well. Remember that different patches of atmosphere bend starlight like a prism. Prisms also break white light into the rainbow spectrum of color. With Sirius, each separate color is bright enough to register on your cones. So, not only does it twinkle, it flashes in brilliant colors. Anything in the sky rapidly changing colors just doesn’t look like a star; it must be a UFO.
Not in this case.
“UFO” Sirius sits in the southeast, one-third of the way up after sunset. The colored twinkling is dramatic and obvious. Check it out tonight. Try using binoculars. The effect is more obvious.
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Venus will reach its greatest brilliancy Feb. 23 as it is poised to dive between Earth and the sun. It will remain the “Evening Star” through the end of March.
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Astronomers need special locations for their expensive telescopes. Twinkling starlight ruins the ability to perceive fine detail. The solution: put your telescope as high as you can, above as much air and especially water vapor as possible. These considerations make Mauna Kea in Hawaii one of the finest observing sites on the planet. The current main feature program in the Kirkpatrick Planetarium Star Theater is “Explorers of Mauna Kea.” The show examines why Mauna Kea is great place to situate your telescope and many of the exciting discoveries made at this superb site. Call 602-3761 for information and show times.
The Oklahoma City Astronomy Club will meet at 7:30 p.m. Friday. Guests are welcome.
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Planet Visibility Report: Brilliant Venus dominates the western evening sky throughout February. Dim Mercury floats at the top of the sun’s light at sunset for the first two weeks of the month and then rapidly plunges between Earth and the sun. Jupiter and Saturn are nearly overhead at sunset. Mars rises around 2 a.m. Full moon will occur Feb. 8; new moon Feb. 23.
Recently recovered FarShores file refiled Dec 31.06
UFO Sightings Generally Not UFOs Says Astronomer
Have you ever seen something you can’t explain in the night sky? Something that doesn’t look like anything you’ve ever seen? [Original headline:Sightings generally not UFOs]
The Oklahoman / OK | By Wayne Wyrick - February 6 2001
