Asteroid 9 Metis will brighten favourably over the course of the month

Asteroid 9 Metis reaches opposition on 20 July, having tracked from southern Capricornus at the month’s start into Sagittarius. This area of sky can be challenging to navigate due to the fact that it never gets very high from the UK. The start of the track is also less easy to navigate to, thanks to a lack of notable stars in the southeast corner of Capricornus. The situation does improve throughout July though, thanks in part to darkening skies, but also by virtue of a small kite-shaped pattern – the Little Kite – formed by 58 Omega, 59, 60 and 62 Sagittarii. These stars range in brightness from mag. +4.5 to mag. +4.7 and thanks to the area being devoid of much else, do tend to stand out.

The asteroid begins the month at mag. +10.1, brightening towards opposition on the 20th, when it shines at mag. +9.7. By July’s end it only dims by one tenth of a magnitude to end the month at mag. +9.8. This places 9 Metis within small telescope range. One caveat will be the Moon, which is full on 13 July, making it difficult to navigate this area of sky around mid-month.

On the morning of the 14th, the Moon will sit immediately west of the kite-shaped asterism mentioned earlier. On opposition night, the Moon will appear 56%-lit, 80˚ to the east, and should be less intrusive, a situation that continues to improve towards July’s end.

Metis is a main-belt asteroid, located in a vast band of similar objects orbiting between Mars and Jupiter. It is a large siliceous or S-type asteroid, a term used to describe a stony or mineralogical composition. The best-fit size of Metis is a tri-axial ellipsoid 222km x 195km x 140km. It was discovered by Irish astronomer Andrew Graham with a 3-inch, wide-field scope made for hunting comets.