Asteroid (4) Vesta occults a bright star

2020 February 3

Tim Haymes

On 2020 Feb 11 at 22:02 UT, observers in Newfoundland, Scotland, Northern Ireland, the north of England, the Isle of Man, Denmark, southern Norway and Sweden may be treated to a once-in-a-century event when the 522km-diameter main belt asteroid Vesta occults the 5th magnitude HIP 14439. Vesta itself is magnitude +8 and the star is expected to ‘disappear’ for up to 28s when the asteroid blocks the light path. A close appulse will occur for observers outside the occultation path.

For the best chance of seeing an occultation, observers need to be north of the blue line in the map shown. Maximum duration is expected in the central regions of the path, between Inverness and Glasgow.

The prediction by E. Goffin appears on p.53 of the BAA Handbook 2020.

When I searched for occultations by Vesta of naked-eye stars during the period from 1920–2020, I found five observable events across the globe (see Table 1). So for the UK, the 2020 February event is quite a rare occurrence. Looking into the future, there will be no UK events until 2070 AD.

Tips

To locate the star, I suggest the use of good mounted binoculars or a small telescope. It is unlikely to be seen by eye alone unless it is very dark and clear. The starfield is towards the south-west at altitude 27° and azimuth 250°; there are a number of brighter stars nearby to guide the observer (in the constellations of Aries, Cetus and Boötes).

When the star is found, the 8th magnitude asteroid should be seen close by and some magnification will show the event well. A good plan would be to set up 30 minutes beforehand and watch the asteroid creep up on the star until, if you are in a good location on the path, an occultation should be seen.

It will be possible to record the occultation by video or CCD and to time it, but I would also watch and enjoy. This is a good opportunity to see an occultation visually – if the weather cooperates.

Timing the event

A silhouette of Vesta can be revealed by timing the start and duration of the occultation. Observers’ timings from different parts (and depths) of the shadow path can be combined. The Section would be pleased to receive your impressions or timing data.