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Sky Watch by J. Alex Knoll

Comet ISON is heading for the sun

If you haven’t looked for Comet ISON yet, now is the time. In just the past few days, the comet has grown more than 15 times brighter and is now visible to the unaided eye low in the east-southeast before dawn.

The interloper visits Spica and Mercury

Mercury is putting on its best pre-dawn show of 2013, more than doubling in brightness this week, from +1 magnitude to –0.5 (each order of magnitude is exponential, so an increase from +1 to 0 is a doubling). Monday marks the innermost planet’s greatest elongation — its farthest point away from the sun as seen from earth and its highest point above the horizon. Mercury rises a little before 6am and climbs nearly 15 degrees above the southeast horizon before the sun rises more than an hour later.

Planets and clusters and meteors

As the sun sets around 5pm, Venus blazes in the south-southwest. Our sister planet is at its farthest point east of the sun. But the geometry between Venus, the sun and earth doesn’t add up to a better view, as the evening star climbs only a dozen degrees above the horizon and sets within 90 minutes of the sun. Still, Venus is near impossible to miss, and Thursday evening it is joined by the waxing crescent moon a little higher in the sky.

Even a partial eclipse can be blinding

The last day of October marks the mid-point between autumnal equinox and winter solstice, one of four cross-quarter days in the passage of the earth around the sun. The day has been recognized for millennia, celebrated as Samhein, The Day of the Dead and All Hallow’s Eve, or Halloween.

The brightest Evening Star

Sunset finds Venus ablaze low in the southwest before setting by 8pm. There is no brighter planet or star, and so close to the horizon Venus can pulse and shimmer as its light is distorted by our atmosphere. Traveling close to the sun, Venus appears for at most a few hours either after sunset or before dawn. This led early civilizations to believe that the evening star and the morning star were two distinct objects. The ancient Greeks called the morning Venus Phosphoros and the evening apparition Hesperos.

Despite a penumbral eclipse, the moon will dampen the Orionid meteors

As the sun sets Friday, the full Hunter’s Moon rises, shining all night long and reaching its highest around midnight. Like last month’s Harvest Moon, the Hunter’s Moon travels its shallowest arc along the ecliptic, rising far to the north of due east and setting far to the south. Rising so much farther to the north than other months, the Hunter’s Moon reappears just 30 minutes later from night to night, as opposed to 50 minutes normally. The effect of this is several consecutive nights bathed in moonlight from near sunset to sunrise.

Join the fun in International Observe the Moon Night

Saturday, October 12, is International Observe the Moon Night, a global celebration of earth’s only natural satellite. InOMN is overseen by “scientists, educators, and moon enthusiasts [who] believe in the inspirational power of the moon — a celestial body that has influenced human lives since the dawn of time.”

The new moon is right in front of us, but its absent light reveals plenty

Friday marks new moon. You might think that the new moon is lost behind the sun. But the moon is roughly 250,000 miles from earth, while the sun is more than 90 million miles away. So the moon can never be behind the sun. Rather, new moon is right in front of us, directly between earth and the sun, invisible in the blinding glare.     This makes for dark night skies much of the week, allowing you to spot more dim and distant celestial objects.

While the Harvest Moon lingers, the sun begins a fast getaway

If you’ve been outside after dark the past few days, you’ve likely noticed the full-appearing moon. While Thursday the 19th marks the true full phase, September’s Harvest Moon fills the sky for several days at a time. The full moon closest to Autumnal Equinox, the Harvest Moon gets its name from the role it played historically in providing light for farmers to bring in the last of the season’s crops.

Stellar incubator is home to thousands of stars

Saturn and Venus have been fixtures of the early evening sky, and come Friday, the two are within half a dozen degrees of one another. By Tuesday they are barely three degrees apart low in the west-southwest immediately after sunset. Venus is so bright you may spot her while the sky is still lit. Saturn pops into view to the upper left of Venus. Both planets sink beneath the horizon within an hour of the sun, but over the coming weeks, Venus holds steady, while Saturn disappears from view.