Look up in the sky this month and you might see... a comet. (What were you expecting, Superman?) Linear and Neat are two long-period comets--with orbits of more than 200 years around the sun--making their debut in recorded history. To spot them, your best shot is to flee the city lights for "a place dark enough to see the Milky Way" at night, says Donald E. Brownlee, astronomy professor at the University of Washington in Seattle. Neat will be at its brightest this week, in the southwest horizon near Sirius. Linear can be seen in late May and early June at dusk in the west-southwest. Search skyandtelescope.com for more information and cometography.com for recent photographs. A third comet, Bradfield (pictured), is also out there. But it's fading, so you'll need a good telescope to catch it.