Don’t miss brightening Comet 41P riding high in Ursa Major during March

By Ade Ashford

Comet 41P/Tuttle–Giacobini–Kresák was about magnitude +8 on the evening of 15 March when captured in this nine-minute integration with a colour Starlight Xpress Ultrastar camera at the f/2 HyperStar focus of the author’s Celestron C11 Schmidt-Cassegrain telescope. The comet’s motion is evident during the exposure. AN image by Ade Ashford.
Now that the waning gibbous Moon is confined to the early morning sky, observers can make the most of the dark evenings to catch a brightening comet that is very well placed for Northern Hemisphere stargazers. Discovered in 1858, 41P/Tuttle–Giacobini–Kresák is a periodic comet that orbits the Sun every 5.4 years and will pass through perihelion (its closest point to the Sun) on 12 April 2017.
During the second half of March 2017, periodic comet 41P/Tuttle–Giacobini–Kresák traverses nearly 30 degrees of sky through the constellation of Ursa Major into Draco, making it ideally placed for Northern Hemisphere observers. Comet 41P should be a comfortable binocular object as seen from rural areas in the latter part of the month. As UK darkness falls on Wednesday 22 March, the comet lies 0.6 degrees from galaxy Messier 108 and less than a degree from the Owl Nebula, Messier 97 — a perfect astrophotographic opportunity! Click the graphic for a high-resolution PDF finder chart suitable for printing. AN graphic by Ade Ashford.
Comet 41P is well worth a look with binoculars and telescopes using your lowest magnification eyepiece, as increased outgassing from its mile-wide icy nucleus can give rise to surges in brightness. In late May 1973, the comet flared ten magnitudes to peak at a comfortable naked-eye magnitude +4 — an incredible 10,000 times brighter over the course of a week! Of course, that doesn’t mean Comet 41P will do the same this time around, but one never knows.

Click here for a high-resolution PDF version of the finder chart above. Comet 41P passes just 0.14197 astronomical units (13.2 million miles; 21.2 million kilometres) from Earth at 00:53 UT on 1 April. This is equivalent to 55 times the distance of the Moon. More on that — and the comet’s close encounters with some prominent stars in the constellation of Draco — nearer the time.

This UK topocentric ephemeris of 41P/Tuttle–Giacobini–Kresák shows the J2017.3 apparent coordinates of the comet at 22h UT (10pm GMT) from 18 March to 2 April 2017. Since right ascension (RA) and declination (Dec) are given for the current epoch, they may be entered directly into digital setting circles. Delta is the comet’s distance in astronomical units (AU), predicted total magnitude (Mag), apparent motion in degrees/day and constellation of residence.

Inside the magazine

For a comprehensive guide to observing all that is happening in the coming month’s sky, tailored to Western Europe and North America, obtain a copy of the March 2017 edition of Astronomy Now.

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