Published Saturday, Feb. 20, 1999 They're planets, not stars. And, Lightner advises, don't stop watching now, because they're getting ready to put on some spectacular displays that won't be matched for years.
Lightner, professor of physics at Westminster College, New Wilmington, and co-director of the college's planetarium, said that he's hoping for a clear night on Feb. 23 to better see a "rare, close conjunction of Venus and Jupiter." The two planets will be so close together -- less than 0.5 degrees -- that it will "look like they're on top of each other," he said.
That conjunction of planets won't happen again until 2015, Lightner said, and the number of planets currently visible won't be bested till March, 2002.
Right now, Venus, Jupiter, and Saturn are all visible to the unaided eye. Venus, is just above the west-southwest horizon, lining up with the orbit of the sun. Just above Venus and to the left is Jupiter. About 28 degrees above and to the left of Jupiter is Saturn.
Next week Mercury joins the planetary congregation, coming out from the glare of the sun. Mercury is below Venus, and difficult to see because it's so close to the horizon and sets before the sky is dark enough to see it clearly.
By Feb. 23, though, Lightner said, that small planet should be visible without binoculars, setting about 45 minutes after sunset.
On March 8, the four planets are at a "minimum span," Lightner said, 27 degrees from Mercury to Saturn. "That's a pretty narrow range to find four planets," he explained. By this time, Venus will have passed Jupiter, so the planets will be in this order: Mercury, Jupiter, Venus, and Saturn.
By mid-March, Lightner said, Jupiter and Mercury start to disappear into the evening twilight. On March 19, Venus and Saturn are at their closest, a little over 2 degrees apart. By mid-April, Saturn will also disappear into the twilight. Venus will stay with us a while, however, continuing to be "a beacon of light in the west the rest of the spring," Lightner said.
And if that spring night light is not quite enough for you, just turn to the east. By April, Lightner said, Mars will be rising in the east and will become brighter every evening.
First, understand that location and timing are critical. "You've got to be somewhere that has a good sight line of the west-southwest horizon," Lightner said. While it doesn't have to be on a hill or a rise of land, that certainly won't hurt, since Venus and Jupiter are fairly close to the horizon and Mercury is even closer. What your location needs most of all, though, is a view unimpeded by trees and buildings.
When you find that good location, get there at a good time, around 30 minutes after the sun sets. According to Lightner's chart of the sun and evening planet setting times, on Feb. 23 the sun sets at 6 p.m., Mercury at 7:17, Venus at 8:18, Jupiter at 8:19, and Saturn at 10:33. Keep in mind, Lightner warns, that total twilight time is about 1½ hours, making Mercury very difficult to see because the sky won't be totally dark before that planet sets.
Venus and Jupiter, on the other hand, will be very difficult to miss. Venus is the brightest object in the evening sky, next to the moon, and, joined with Jupiter's light will be exceptionally bright. The trick on Feb. 23, Lightner said, will be to spot two distinct planets because it may look like one large one.
By Mar. 8, the setting times for sun and planets are favorable for seeing all four planets. The sun will set at 6:15, followed by Mercury at 7:41, Jupiter at 7:43, Venus at 8:49, and Saturn at 9:49. This is the date the four are within 27 degrees of each other, which may prompt you to ask, "how am I supposed to measure a degree to find these objects?"
Lightner has a rule of thumb for that measurement -- or, more accurately, a rule of hand.
When you're observing stars or planets and have no instruments to measure distance, hold your arm straight out in front of you toward the objects. If you spread your fingers, the span from your thumb to your little finger is about 15 degrees, Lightner said. If you put your fingers together, the span across your hand (including your thumb) is about 10 degrees. If you hold up your forefinger, the span across the finger is about 1 degree.
So, presuming you've easily found Venus and Jupiter on Feb. 23 and are looking for Saturn, which is about 28 degrees above and to the left of Jupiter, you might try spreading your fingers once, and then again, to get an approximate location. On Mar. 8, that rough measurement will be a little more than the 27-degree distance between Mercury, closest to the horizon, and Saturn, farthest from the horizon.
Just in case you're worried that your hand is either too big or too small to get this measurement right, Lightner said he and others at the college have already discussed that issue. They've concluded that it doesn't make much difference. People with larger hands generally have longer arms, and people with smaller hands generally have shorter arms, making the rough distance measurement work out right no matter what.
If you're still not sure how to observe stars or planets on your own, Lightner and Westminster College host a weekly sky observing gathering every Monday (weather permitting) at 8:30 p.m. Open to the public, this group meets at room 104 in the Hoyt Science Building and then goes to the rooftop observatory. Although that time makes it too late to see any planet but Saturn right now, you will learn where to look for them. You may also see the southern sky, home of Orion. If you can tear yourself away from the planets, look south, because that area right now, Lightner said, "is the richest in bright stars of any region of the sky."
