Asteroid 15 Eunomia will be well placed, lying in the constellation Scorpius, well above the horizon for much of the night.

Regardless of your location on the Earth, 15 Eunomia will reach its highest point in the sky around midnight local time.

From Cambridge however, it will not be readily observable since it will lie so far south that it will never rise more than 16° above the horizon.

The geometry of the alignment

This optimal positioning occurs when it makes its closest approach to the point in the sky directly opposite to the Sun – an event termed opposition. Since the Sun reaches its greatest distance below the horizon at midnight, the point opposite to it is highest in the sky at the same time.

At around the same time that 15 Eunomia passes opposition, it also makes its closest approach to the Earth – termed its perigee – making it appear at its brightest in the night sky. This happens because when 15 Eunomia lies opposite to the Sun in the night sky, the solar system is lined up so that 15 Eunomia, the Earth and the Sun lie in a straight line with the Earth in the middle, on the same side of the Sun as 15 Eunomia.

On this occasion, 15 Eunomia will pass within 1.851 AU of us, reaching a peak brightness of magnitude 9.3. Nonetheless, even at its brightest, 15 Eunomia is a faint object beyond the reach of the naked eye; binoculars or a telescope of moderate aperture are needed.

Finding 15 Eunomia

The chart below indicates the path of 15 Eunomia across the sky around the time of opposition.

It was produced using StarCharter and is available for download, either on dark background, in PNG, PDF or SVG formats, or on a light background, in PNG, PDF or SVG formats.