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Celestial Trifecta on Monday, Dec. 7

Monday, December 7, has three celestial highlights for observers in the South Bend, IN, region--a comet, an occultation, and satellite passes.


Before sunrise in the eastern twilight, find a triangle formed by the crescent moon, Venus, and Comet Catalina, with the faint comet requiring a telescope or binoculars. See Comet Catalina in the Morning Sky.


The moon occults

Venus re-emerges from behind the moon.


After the sun sets around 5:15 p.m., satellites offer a double-header. First, around 6:16 p.m., an Iridium satellite zooming over Michiana "flares" as it reflects sunlight.

Image of Iridium ground track courtesy of Chris Peat.

[Actually, for South Bend residents, a brighter flare occurs exactly 24 hours earlier in the same spot, 30 degrees above the horizon at 188 degrees of azimuth (compass bearing). The Dec. 7 flare is centered over Elkhart and Goshen (see map), but the Sunday, Dec. 6, flare occurs after the satellite passes directly over South Bend.]

For more satellite predictions, see Heavens-Above.

Image of Iridium path courtesy of Chris Peat.

But, wait, there's more. At 7:00 p.m., the International Space Station (ISS) rises above the western horizon, passes the bright star Vega in the Summer Triangle asterism, passes South Bend's birthday star Eltanin, and heads toward Polaris before dimming in the shadow of the earth around 7:05 p.m.. The path of ISS below is adapted from the more accurate starfield of Heavens Above, shown further below.

ISS pass Dec. 7, 2015

Star chart for ISS pass for Dec. 7, 2015. Image courtesy of Chris Peat.

The ground track shows the path of ISS and its appearance from 7:00 to 7:05 p.m. EST on Dec. 7, 2015.

ISS ground track for Dec. 7, 2015. Image courtesy of Chris Peat.

Most of the mentioned celestial highlights require a low, unobstructed horizon, so plan in advance the site from which you will observe.

If you've read this far, I'll tell you that a higher ISS pass will occur Saturday, Dec. 5. The space station rises out of the southwest after 7:07 p.m., and heads to 70 degrees of altitude before it fades into the earth's shadow at 7:11 p.m. Note that when ISS disappears, its visible streak ends near Indiana's Bicentennial Star named Scheat.

As if that isn't enough, December 8, just after 6:06 p.m., the ISS makes its best pass yet, zooming from southwest to high overhead (74 degrees) to northeast. It'll be obvious when it's high until it disappears low in the northeast at 6:12 p.m..


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