Discovered in 1986 by Australian astronomer Malcolm Hartley, the mountain-size ball of ice and dust orbits the sun every 6.5 years. But comet Hartley 2 has remained shrouded in mystery, in part because gravitational interactions with Jupiter kept pushing the comet's path farther from Earth. That means Hartley 2 has been too faint to be seen using anything other than professional telescopes—until now.

This week the comet should already be visible to the naked eye as a faint fuzzy patch in the late-night sky high above the northeast horizon.

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