The annual Leonid meteor shower is due to be at its peak tomorrow. But astronomers aren't forecasting any space spectaculars like the Perseid meteor "storm" that flopped in August.
"When we build too much hope for something spectacular and it doesn't happen, it's a bad reflection on science," said Dr. George W. Wetherill, an astronomer at the Carnegie Institution of Washington.
"Then when you really have something you want to tell about, they [the public] don't pay any attention."
The Leonid shower is expected to be near its peak just after dark tomorrow, with perhaps 12 to 16 meteors an hour.
"That's only three to four times more than you would see on a normal night in a dark location," said Jim O'Leary, of the Davis Planetarium in Baltimore. "But this meteor shower is unpredictable. It can be much higher than that."
The Leonid shower is associated with the comet Tempel-Tuttle, which visits the inner solar system about every 33 years, leaving a trail of dust and stony debris. The Earth passes through the debris stream each November on its orbit around the sun, producing the Leonid showers.
Shortly after many of Tempel-Tuttle's returns, the Leonid displays have been extraordinary. The last such spectacular was in 1966, when as many as 150,000 meteors an hour were recorded on the West Coast -- about 140 per minute. Similar events were recorded in 1866, 1833, 1799 and as far back as A.D. 472, when they were seen in Constantinople.
If the pattern holds, the next chance for a show like that will come in 1999.
If there is any excitement surrounding this year's Leonids, it is being fueled by Peter Brown, an amateur Canadian astronomer who publishes a newsletter for the International Meteor Organization.
Mr. Brown has noted that the Leonid showers began increasing in 1961 -- five years before the really big display in 1966 -- suggesting that they may soon begin to increase in advance of Tempel-Tuttle's return in 1999.
But Dr. Wetherill advises caution.
"I hate to disappoint people," he said. "Then they feel nobody knows what they're talking about, which is pretty much true with regard to most meteor streams. They are very poorly understood."
After the spectacular displays in 1833 and 1866, the news media of the day produced a tremendous amount of advance publicity for the expected 1899 Leonids.
"And nothing happened, or nothing to speak of," Dr. Wetherill said. "I think that had a lot to do with the demise of meteor astronomy. Before that time it was considered a respectable field of work. After that it fell into quite a bit of disrepute. And it's been a very small field since then."
Amateurs like Mr. Brown have been providing science with most of the new data collected since then.
Mr. Brown was among those who predicted that last August's Perseid meteor shower would be particularly intense -- hundreds of meteors a minute. The prediction was based partly on the observation that the Perseids' associated comet, Swift-Tuttle, passed closer to Earth last November on its 130-year orbit than it had in more than 2,000 years.
Others disagreed. But taking no chances, scientists at the Space Telescope Science Institute in Baltimore swiveled the $1.5 billion Hubble Space Telescope in orbit to protect its mirror and solar panels. NASA postponed a shuttle flight until after the shower.
Then the Perseids fizzled.
Clouds blocked the view for most Marylanders. Sky-watchers elsewhere with a clear view saw a nice Perseid display, but not the spectacle they were led to expect.
If you want to try your luck with this year's Leonid shower, Mr. O'Leary advised that you find a place as far as possible from urban lights and allow 20 minutes for your eyes to adjust to the dark.
"Dress up warm, and bring some hot chocolate and a lounge chair or a sleeping bag," he said. Watching for meteors from a standing position can be quite literally a pain in the neck.
The Leonid shower will appear to originate in the constellation Leo, hence its name. But that star field does not rise in the east at this time of year until after midnight.
There's no need to wait. The shower will actually peak at 4 p.m., and meteors should begin to appear overhead as soon as the sky is dark. Moonlight should not be a problem. "The moon will be a thin crescent in the western sky after sunset," Mr. O'Leary said. "It will be setting an hour or two after the sun and will be out of the way."