Published: 2007-04-28 09:40:19
Updated: 2007-04-28 09:40:19
Posted April 28, 2007
By Tom Russell / Marilyn Rhodes / Lynn
Some related recent questions:
Last night, 4/25/07 at around 8:45 pm, we saw very bright light in the night sky over the Durham, RDU Airport area. It was not moving, or blinking, but did not look like a planet or star. Was there anything passing over our area that you know of? Possibly a sattelite or the spacestation? Marilyn Rhodes
What is the bright "star" in the southern sky just after sunset until 11pm or so? Is it a planet or star? Lynn
MIKE MOSS SAYS: Tom, Marilyn and Lynn, I would speculate that the brightest and steadiest of the lights you are seeing is the planet Venus, which is currently visible sinking through the low western sky in the evenings. It can appear so bright as to make you wonder if it isn't some kind of artificial object, but it fits with the descriptions you've given. Unlike a satellite or the space station, however, it appears to remain in one place when watched for a while, whereas sateliites usually progress across the entire sky over the course of a few minutes.
As for the varying colors Tom reported, my guess would be a couple of very bright stars that are also low in the western sky in the evenings at this time. They include Sirius, Rigel and Betelgeuse, three of the nine brightest stars in the sky. Sirius, the brightest, has often been reported as oscillating among several colors when it is down fairly close to the horizon, the apparent effect of its very bright starlight passing through turbulent irregularities in temperature and humidity (and thus density) which causes an erratic dispersive refraction and scintillation of the star. This can cause its apparent brightness to fluctuate, and can also result in some colors of the spectrum being magnified so that in addition to "twinkling," the star may appear to cycle through a variety of colors.
A good resource for identifying objects you've seen in the night sky, or in planning for future observations, is the interactive sky chart available online at the Sky & Telescope web site. You can designate your location and time zone, and then can us a plus and minus button to step ahead or back (by minute, hour, day, month or year) through a map of the sky that shows major stars, constellations, planets, and the position of the moon and sun. Here is an address for the chart
Note that for some reason this feature has not worked for me in Firefox browsers, but does seem to work well using Internet Explorer.