Weather permitting, millions of people in the northeastern USA could witness a rare and eerie sight next week: a space rock blotting out one of the brightest stars in the sky.
The Rhode Island-sized space rock will extinguish the light from the star Regulus just after 2 a.m. ET Thursday for as long as 14 seconds. This blockage-by-space rock will be the most visible such event in North America, an unprecedented marvel that those with no astronomical knowledge can observe.
What's more, anyone with even modest gear "can contribute real science," says Alan MacRobert, a senior editor at Sky & Telescope magazine. "You can give one additional data point for determining the character of this asteroid that will be known for all time and history." An observer armed with a digital SLR camera can collect high-quality data, but even someone with just a stopwatch, video camera or no equipment at all can provide useful information.
Space rocks, formally known as asteroids, block the stars every night. Only people with telescopes can see most of these "occultations." The asteroid is usually too small, too dim, too fast or too far away to make for easy observation, and relatively few stars are bright enough to be seen with the naked eye, says Steve Preston, president of the International Occultation Timing Association, a volunteer science organization, via e-mail. He says that since the 1980s, only eight occultations of stars visible to the naked eye have been observed in the USA. The asteroid blockage of the next-brightest star was in 1975, and that star was far dimmer than the star that will vanish next week.
The star of the show Thursday is Regulus in the constellation Leo, which will be in the western part of the sky in the wee hours. Regulus is what's known as a first-magnitude star, so it's very bright to those in rural areas and visible in big cities except in places such as Times Square that are drenched in artificial light.
Thanks to Regulus' brightness, the asteroid's passage will be visible in New York City, Long Island and portions of New York state, New Jersey, Connecticut and eastern Canada. The exact time will vary by location, but those in the New York metropolitan area should see the star disappear around 2:06 a.m. ET, according to the website set up by the occultation association.
Of all the occultations "easily visible to lots of people, this is going to be by far the best one, head and shoulders above any other," says Brad Timerson, another official of the occultation association. "Of course, it's 2 o'clock on a Thursday morning."
The spoiler that will temporarily hide Regulus' light is a 45-mile-wide rock named Erigone. Erigone, which is as dark as fresh asphalt, orbits the sun between Mars and Jupiter and does not come close to Earth, says José Luis Galache, an astronomer at the Minor Planet Center, which tracks comets, asteroids and other small objects. Observers should see the star wink out, then reappear. Anyone who times the event can send observations to the occultation association (http://occultations.org/regulus2014), which will use the collected data to calculate the asteroid's shape and precise size and to learn more about Regulus itself.
Skywatchers from as far away as Germany plan to descend on New York for the asteroid's passage, and astronomers plan to deploy to bars in Brooklyn and Manhattan to encourage late-night patrons to step outside. The occultation association has developed a free smartphone app to help people time the passage of the asteroid. The group will post recommendations about the locations most likely to have clear skies.
The long-term forecast for early Thursday is for clouds, but unless the forecast is "hopeless," Preston says, he'll fly from his home in Seattle to New York in hopes of seeing the spectacle.
"This is a very rare event," he says. It "may well be the only chance in my lifetime to observe an occultation of a first-magnitude star."