Asteroid Florence is on its way

[lukebl]

I had a session capturing images of close-approach asteroid 3122 Florence last night, to see if I could determine any magnitude variations to show its rotation.

I captured 320 30-second exposures over a period of about 3 hours, and then ran the images through Muniwin software to produce a light curve. Sure enough, my images clearly show a periodic variation of about 0.15 of a magnitude. A small range, but plenty enough for my cam to pick it up. Florence has a published rotation of 2.3 hours, which corresponds with the minima I captured at about 19:20 and 21:40. As you see, there's also a significant minimum in between the two. I guess double minima like this demonstrates significant changes in albedo or shape, although the Aricebo radar images show that it's roughly spherical. Florence is an interesting object. It's a potentially hazardous asteroid with two moons. After its close approach last month, it's now high in the northern sky in Ursa Minor at a distance of 47 million km. It's officially at mag 13.8, but my astrometric measurements make it somewhat brighter at about 13.1.

Here's the light curve:

And here's a quick stack of a few of the images. No darks of flats:

An here's a lovely animation of the fascinating Aricebo radar images, which shows its two little moons nicely: