We hear that Comet ISON has had an outburst. It has suddenly brightened and might be visible to the eye alone, in dark country skies. Plus the planet Mercury is now presenting its best morning apparition of the year for the Northern Hemisphere, and Mercury is in the same part of the sky as the comet. Friday morning – November 15, 2013 – will be a good time to look east before dawn!
You probably won’t need binoculars to catch Mercury around 90 to 70 minutes before sunrise on Friday. But you will want to bring along your binoculars (or a small telescope) to scan for Comet ISON. People are describing it as “a smudge.” But possibly a visible smudge, if your sky is dark enough! And that’s exciting. It might mean ISON will continue to get brighter and give us a good display in early December, after it rounds the sun. Or … it might not.
Both Mercury and Comet ISON are brightening day by day. Will Comet ISON be visible to the unaided eye when the twosome comes together on November 21 and 22? Maybe.
Before the comet appears near Mercury on our sky’s dome, however, Comet ISON will first pair up with the star Spica on November 17 and 18. Go back to our post for November 12 to learn more about that.
Or if you’re up for a really big challenge, you can try to catch Comet Encke, as Mercury shares the same binocular field with this comet for several days, centered on November 18. For us mere mortals, though, we may rest content just seeing Mercury near the horizon at the crack of dawn.
Mercury is considered the most elusive planet because it’s the innermost planet in our solar system. It always stays near the sun in our sky, either up briefly in the west after sunset or – as now – up briefly in the east before dawn. Mercurty will reach its greatest western elongation – maximum angular distance from the sun – on November 18. What’s more, Mercury will in the same part of the sky as Comet ISON – which is not visible to the eye, but which is visible with binoculars – for several days, centered on November 22. After that, Mercury will have a stunning conjunction with the planet Saturn in the predawn and dawn sky on November 25 and 26.
At present, Mercury rises about 100 minutes before sunrise at mid-northern latitudes in the Northern Hemisphere. Farther north, Mercury rises sooner before the sun; farther south, Mercury rises closer to sunrise. At temperate latitudes in the Southern Hemisphere, for instance, Mercury only rises about 45 minutes before the sun.
Mercury, the innermost planet of the solar system, is often lost in the sun’s glare, because this world circles the sun deep inside of Earth’s orbit. But Mercury is now swinging to the outer (western) edge of its orbit as seen from Earth, so we can now glimpse Mercury near the sunrise point on the horizon as darkness gives way to dawn.
Bottom line: Comet ISON has had an outburst and is suddenly brighter, possibly bright enough to see with the eye alone, in a dark sky. It’s in the east before dawn, not far from the planet Mercury, which is now at the height of its best morning apparition of 2013. If you’re in the Northern Hemisphere, look for Mercury and Comet ISON on Friday, November 15, 2013 – or anytime around mid-November. Mercury’s greatest angular distance from the sun on our sky’s dome – called its greatest elongation by astronomers – will come on November 18, 2013. Comet ISON’s perihelion – or closest approach to the sun – will be November 28. Afterwards, the comet may – or may not – become a striking object in Earth’s skies.