Minor planet 4 Vesta reaches opposition on 2 May, a time when it will be shining at mag. +5.7 among the stars of northern Libra.
This offers up an interesting opportunity to try to spot Vesta with the naked eye if you have access to a dark-sky site.
Vesta was the fourth minor planet discovered and is the brightest, able to reach a peak mag. of +5.1 during an extremely favourable opposition.
The average threshold of naked-eye visibility from a dark sky site is mag. +6.0, but it doesn’t take much in the way of light pollution or haze to raise this threshold.
Consequently, seeing Vesta with the naked eye may be a step too far for many this year, the easiest observing option being binoculars.
Here, things get a lot easier as Vesta will be visible through any binocular size. It also goes without saying that a small or larger telescope will easily be able to bring you a view of Vesta.
How to find Vesta
To locate Vesta using binoculars, wait for the sky to darken and then try to work out the form of Virgo.
This is easier said than done, as the constellation is quite sprawling in nature.
Find the three stars Iota (ι) and Mu (μ) Virginis together with 16 Librae, magnitudes +4.1, +3.8 and +4.5, respectively.
During May, Vesta follows an arcing path from 16 Librae to 1° north of the mid-point between Iota and Mu Virginis.
From 16 Librae to Mu Virginis is around 3.8°, which fits easily inside an average binocular field of view.
If you have very dark skies, then once you’ve located Vesta with binoculars, try for it with the naked eye but make sure your eyes are properly dark-adapted; 20 minutes in complete darkness should get your eyes to peak sensitivity.
If you manage to spot or photograph Vesta in May 2025, we'd love to hear from you! Email us at contactus@skyatnightmagazine.com
