Before the light from a waxing Moon becomes too obtrusive (full Moon occurs on 19 February), take full advantage of any clear nights to catch a glimpse of swift Comet C/2018 Y1 Iwamoto as it traverses the constellations of Leo, Cancer and Gemini over the next ten nights. Click here to download a high-resolution PDF finder chart suitable for printing.
Discovered by Japanese astronomer Masayuki Iwamoto in images captured on 18 December 2018, C/2018 Y1 orbits the Sun every 148.7 years in a highly eccentric path inclined to the ecliptic by an angle of 160 degrees. Comet Iwamoto came within 1.3 astronomical units (AU) of the Sun at perihelion on 6 February, but will plumb the depths of the solar system out beyond 245 AU at aphelion.
Comet C/2018 Y1 passes closest to Earth on 12 February at 20:10 UT when it lies 0.30384 AU, or 45.45 million kilometres away (some 118 times the distance of the Moon) and can be found traversing Leo at a rate of 7.2 degrees/day. At opposition on 13 February, the comet transits around 12:30am GMT at an altitude exceeding 50 degrees for an observer in the heart of the British Isles.
Predictions indicate that Comet Iwamoto might attain an integrated magnitude of +6 around closest approach, but don’t miss any viewing opportunities owing to the waxing Moon’s glare. Latest reports indicate a coma approximately one-third of a degree across with a short tail.
A close encounter with NGC 2903
On the UK night of 13 February, C/2018 Y1 passes very close to magnitude +9 barred spiral galaxy NGC 2903 in Leo about 21:30 UT (9:30pm GMT). In fact, depending on the comet’s coma size, it may appear superimposed on the galaxy! Discovered by Sir William Herschel who catalogued it in 1784, NGC 2903 is visible in large binoculars or small telescopes and lies about 30 million light-years from Earth. This galaxy displays exquisite spiral arms in photographs, so astrophotographers are advised to prepare for a great shot – weather permitting.