Observe asteroid 8 Flora as it reaches opposition in the constellation of Cetus

The asteroid 8 Flora is at opposition on 1 November, when it will appear at mag. +8.0 in the constellation of Cetus, the Whale. At the start of the month it’s conveniently located just to the west of the mag. +3.5 star, Kaffalijidhma (Gamma (g) Ceti). At 00:00 UT on 1 November the asteroid is just 20 arcminutes west of this star. Kaffalijidhma marks the southern point of Cetus’s misshapen pentagonal head. Over the remainder of the month, Flora tracks west, arcing slightly to the west-northwest towards the end of November. It never strays too far from the head asterism though.

Flora is a large and bright object, with a mean diameter of 128km based on tri-axial ellipsoidal dimensions of 136km x 136km x 113km. It has a relatively high albedo of 24.3%, a measure of how much incoming light it reflects. At favourable oppositions it can brighten to mag. +7.9 (at its dimmest it is mag. +11.6) and this month’s opposition will see it get close to its peak of achievable brightness.

Flora has several claims to fame: it’s the lead member of the Flora family of S-type (siliceous) asteroids, thought to be the source of the object which impacted Earth and wiped out the dinosaurs.

It is also the closest of the large asteroids to the Sun and has the second closest mean orbital distance of the main belt asteroids, at 2.20 AU; its orbit takes it between 1.86 AU and 2.55 AU of the Sun.

Flora has caused confusion in the past, when an observation in March 1917 of the 15th magnitude variable star TU Leonis was usurped by 8 Flora. Having been mistaken for the star, it looked as if TU had brightened considerably. As a consequence, Flora was classified incorrectly as a U Geminorum cataclysmic variable. This classification remained until the error was realised in 1995.