The Great Green Comet of 2018


Contributing Writer
Walt Pickut
Martz-Kohl Board of Directors

Beginning in early December, sky watchers around the world began to report that Comet 46P/Wirtanen was brightening noticeably as it zoomed toward the sun on its 54-year periodic visit to the inner solar system and Earth’s neighborhood. This year, it came within 7.4 million miles of Earth, a near-miss in astronomical terms. In theory, it was growing bright enough to be seen with the eye. Unfortunately, the dim light from the comet’s fluorescing atmosphere, its coma, about 100,000 miles across, is spread over an area wider than a full moon. Therefore its half-mile wide nucleus will be hard to see without binoculars or a telescope.
The comet is glowing in a peculiar shade of green. A comet’s atmosphere, though extremely thin, fluoresces in sunlight. It is usually composed of water, methane, carbon dioxide, cyanide, ammonia and other gasses. The proportions and nature of the gasses determine the color. Wirtanen’s green is quite unusual.
Wirtanen’s closest approach to Earth was on Sunday, December, 16. But it will remain in the sky for a considerable time to come.

Where to Look

To learn exactly where in the sky to look for Comet Wirtanen on any particular night with binoculars or a modest backyard telescope, check the Comet Wirtanen page at or

Observatory Reopening for Doors Open 2019

Though ongoing construction closed the Martz-Kohl Observatory this fall, it reopened briefly last month to host a number of groups and guests. However, between now and January 19, it will be closed to visitors again for installation of a new parking lot which will make the observatory inaccessible and potentially hazardous to all but necessary construction equipment.
Doors Open Jamestown 2019, Saturday, January 20, 10 a.m. to 5 p.m., will see the Martz-Kohl Observatory open again to welcome guests for tours and educational sessions to view the new facilities, telescopes, and astrophotography presentations.

A Solstice Meteor Shower

December 21, the shortest day and longest night of the year, will herald arrival of the Winter Solstice. The South Pole of the earth will be tilted 23.5 degrees toward the Sun. This is the first day of winter in the Northern Hemisphere. December 22 welcomes the Full Moon, known by early Native Americans as the Full Cold Moon and by the Europeans as Full Long Nights Moon and the Moon Before Yule.
December 21 and 22 will also bring the Ursids Meteor Shower with about 5 to 10 meteors per hour, composed of dust grains left behind by comet Tuttle, first discovered in 1790.
Unfortunately, the full moon’s glare will hide all but the brightest meteors, mostly emanating from a focus in the constellation, Ursa Major – the Big Bear – or the “Big Dipper.”

For a deeper look at the night sky, planets, stars and the entire universe, visit the Martz/Kohl Observatory online at, check the schedule of events and visit in person. Thank you to Hall and Laury Opticians for sponsoring these Martz/Kohl column.