Tuesday, August 29, 2017
Seeing NEO 3122 Florence from Australia
NEO 3122 Florence makes an historic approach to Earth in early September. This will be the closest this asteroid, named after reforming nurse Florence Nightingale has come since 1890.
While not a particularly close approach (September 1, 12:06 UT, 0.047 AU, around 18 Earth-Moon distances), this will be the closest a large NEO has come to Earth since this class of objects were first described.
With a diameter of about 4.3 km, Florence ranks fourth in diameter of those NEO's classified as potentially hazardous. It is also the brightest of the Large NEO's, brighter than 3200 Phaeton (the asteroid responsible for the Geminid meteor shower).
The asteroid will range from magnitude 9 up to around magnitude 8.7 then fading down to 10.
This means that the asteroid is potentially viewable in good binoculars (10x50's and up) under dark sky conditions. However, the waxing Moon will make binocular detection harder closer to closest approach. It will remain easily visible in small telescopes even with the increasing moonlight.
Although the asteroid is effectively on a line between the bright stars Fomalhaut and Altair, Finding the asteroid can be a bit tricky without good maps.
On the 29th, the asteroid is 22" from Zeta (ζ) Capricorii, and so should be easy to spot. You will need to watch the stars around Zeta for around 15 minutes to detect the movement of Florence.
On the 30 the brightening Florence is within 22' of 29 Capricorii (which forms a triangle with iota and theta Capricornii), again, watching for 10-15 minutes will detect the asteroid drifting.
On the 31st the asteroid is between mu and beta Aquarii, but is not close to a useful guide star.
On the first the asteroid is within binocular distance of alpha Equuleus, and between that and 1 Aquarii, but again is not near any obvious guide star. Still if you watch for 10-15 minutes you will see the asteroid drift against the background stars.
Many instruments will be watching this approach, including the Goldstone radar to try and capture its shape and possible satellites.
While not spectacular, this will be an historic pass to witness, the next closest approach of Florence is in 2057.