Friday afternoon, a wee spacecraft orbiting Saturn will turn its camera Earthward and start snapping away.
Launched in 1997, the Cassini probe usually focuses on Saturnian events. It will peek between the planets dazzling rings for snapshots of home. Its the first time Earthlings have been notified in advance that NASA will be taking a picture of them.
Both Carolinas will have rolled into view for the picture. But theres a trick to it. Saturn is nearly 900 million miles away, about 10 times the distance between Earth and the sun.
That means it will take light about 80 minutes to jump the gap, says Daniel Caton, professor of physics and astronomy at Appalachian State University in Boone. Cassini will actually be looking back in time at the Earth as it appeared more than an hour earlier.
NASA knows that because theyre rocket scientists. Theres no need to show up early. Its not actually snapping the shutter for another 80 minutes, 24 seconds. That means Cassini will be capturing the photons that left Earth at 5:27 p.m., says Jia-Rui Cook, spokeswoman for the Jet Propulsion Laboratory in Pasadena, Calif.
So if you want to be in the group portrait, face southeast and smile at a spot about two-fist lengths above the horizon. Gather the family if you want.
And, Caton says, tell them to wave.
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