The heavens are aligning to give Marylanders a rare look at a naked-eye comet as Lulin swings by en route to what could be a million-year exile in the far reaches of the solar system.
Comet Lulin is the first comet visible from Maryland with the naked eye since Comet Holmes appeared in October and November 2007. You can see it already, but the view will be even better when it passes within 38 million miles of Earth on Monday evening, its closest approach since rounding the sun in January.
It might be making its very first visit to the inner solar system, scientists say. At the very least, it is on a path that brings it back into the sun's heat and turbulent solar winds only once in tens of thousands or even millions of years.
Amateur stargazers and scientific observatories around the world are already watching through telescopes and binoculars as the eerie green object brightens with each passing night.
"It's a fairly easy binocular sight now," said Frank Reddy, an astronomy science writer at the NASA Goddard Space Flight Center who spotted it early Monday morning from a parking lot near his home in Greenbelt. He described it as a "hazy ball. ... It was fairly easy to pick out."
It might be more difficult to spot amid urban lighting. But the Maryland Science Center and other local public observatories are preparing to help visitors find the comet during scheduled observation sessions starting this evening, weather permitting. Baltimore's "Streetcorner Astronomer," Herman Heyn, said he would be looking with his telescope Sunday evening, from the 3100 block of St. Paul St. in Charles Village.
Under clear, dark skies, Lulin should be visible for most of the night Monday. The best time to look will be in the late evening, after 11 p.m.
Comet Lulin was first photographed two years ago by Chi Sheng Lin, an astronomer at the Lulin Observatory in Taiwan. But it wasn't discovered in those images until July 2007, when Quanzhi Ye, a 19-year-old meteorology student at mainland China's Sun Yat-sen University, found it on the Lulin photos.
The Chinese and Taiwanese are calling it the "comet of collaboration."
Astronomers around the world quickly zeroed in on the new object. They calculated its orbit and concluded it originated in the Oort Cloud, an icy region far beyond the orbits of the outermost planets.
Comets are often described as dirty snowballs. They're composed mostly of water ice, frozen gases and dust. Scientists believe they carry some of the solar system's original construction debris. By analyzing and comparing comets' composition, researchers gain insights into the physical makeup and environmental conditions of the solar system as the planets formed 4.5 billion years ago.
Lulin is very active, scientists say, perhaps because it is near the sun for the first time and reacting to the heat and bombardment by solar particles.
"There is really a lot of gas evaporating off the comet's nucleus," said Dennis Bodewits, a post-doctoral fellow at Goddard. A comet specialist, he has been observing Lulin in X-ray and ultraviolet wavelengths with NASA's orbiting Swift Observatory.
Most of that gas is water that has evaporated from the comet's icy nucleus. Bodewits estimated the comet is losing water at 800 gallons a second, enough to fill an Olympic pool in 15 minutes.
A handful of spacecraft have flown close to other comets to photograph them and scoop up matter from their tails and "comas," the halo of gas and dust surrounding the tiny nucleus. In 2005, a spacecraft called Deep Impact, on a mission led by a University of Maryland scientist, hurled a projectile onto the nucleus of Comet Tempel 1, then examined the resulting crater and the material blasted into space by the impact.
But mostly scientists study comets from a vast distance, by analyzing the sunlight they reflect or the X-rays they give off as their water molecules are struck by the solar wind. The task becomes more difficult as sunlight hits the gas and dust coming off the comet, and those molecules break down into other substances.
"Our question is, 'How does what we're seeing relate to what the comet is made of?' " Bodewits said. As Lulin draws nearer, he said, "Pretty much all the observatories are on it. It's the only bright comet at this moment."
For the rest of us, it's simply a rare opportunity to see a comet. The last naked-eye comet visible from Maryland was Comet Holmes, in October and November 2007. In 1997, Comet Hale Bopp passed by. Comet Hyakutake, with its classic sweeping tail, made a naked-eye appearance for Marylanders in 1996.
To find Lulin on Monday: Look about halfway up in the southeastern sky, just below the hook-shaped constellation Leo. You should see two bright stars. One is Regulus, the brightest star in Leo. The second is the planet Saturn, a faintly yellow object below and slightly to the left of Regulus.
Scan the sky just below and to the right of Saturn, and look for a fuzzy blob of light. That's Comet Lulin.
Unlike the 1990s comets, Lulin is a relatively small object, with its icy nucleus estimated to be only a few miles across. But its coma has expanded under the sun's influence to the size of Jupiter. It is the sunlight reflected off that coma that makes it visible from Earth.
Lulin's greenish glow is caused by the fluorescence of carbon atoms in the coma as they are struck by sunlight, Bodewits said. But the color might not be apparent to the naked eye or through binoculars.
It might also be hard to spot the odd double tail visible in Lulin photos. A smear of dust appears on both sides of the comet, and a blue-green tail of ionized gas is streaming off the comet, driven away from the sun by the solar wind.
The comet will be visible for several weeks. It will move noticeably westward relative to the stars each night, but it will also fade quickly through March as it speeds away from Earth toward deep space.
For a telescopic view of Lulin, weather permitting:
* The Maryland Science Center: Open this evening until 8 p.m. Extended evening observatory hours next Friday, Feb. 27, to at least 9 p.m.
* Streetcorner Astronomer Herman Heyn: after 7 p.m. Sunday in the 3100 block of St. Paul St., Charles Village.
* Anne Arundel County Community College Observatory: Open Feb. 28. Call 410 777-1820
* Maryland Space Grant Observatory at Johns Hopkins University: Open 8 to 11 p.m. Fridays. Call 410-516- 6525
* University of Maryland, College Park: Open 8 p.m. tonight and March 5. Check Web site: www.astro.umd.edu/openhouse