The Sky Today on Saturday, July 18: Comet Tempel’s knife-edge tail
Catch an edge-on comet as Tempel 2 plunges below the plane of our planet’s orbit, heading toward perihelion.
Imager Chris Schur captured this photo of Comet Tempel 2 on July 10, showing the comet’s bright green nucleus and thin, edge-on tail as Earth passes through the comet’s orbital plane. Credit: Chris Schur
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July 17: The Moon skims south of Venus
Comet 10P/Tempel (also called Tempel 2) is closing in on the Sun for an early August perihelion. It’s now undergoing some spectacular visual changes as Earth passes through the plane of the comet’s orbit. As we pass through the plane, the comet’s tail appears to thin and spread out, turning into a line that extends to either side of the nucleus, rather than the more traditional one-sided tail we’d expect.
Tempel 2 is in an extremely favorable location, rising late in the evening and visible overnight. After the Moon sets, turn southeast and look about 20° above the horizon for 3rd-magnitude Deneb Algedi, the brightest star in Capricornus. Tempel 2 is just 4.2° southwest of this star this evening, close to Iota (ι) Cap (about 1.5° northwest of this star). Check out our chart above to help you pinpoint its location. Recent observations have placed the comet around 9th magnitude — an easy catch for binoculars or any scope, especially in a dark sky.
Sunrise: 5:47 A.M.
Sunset: 8:26 P.M.
Moonrise: 10:41 A.M.
Moonset: 10:58 P.M.
Moon Phase: Waxing crescent (27%)
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40° N 90° W. The Moon’s illumination is given at 10 P.M. local time from the same location.
Alison Klesman is senior editor of Astronomy magazine. She holds a Ph.D. in astronomy and has studied a variety of topics, from minor planets to supermassive black holes.
