Asteroid 14 Irene: see the main-belt body at opposition

Track Asteroid 14 Irene's movements in the night sky over January 2021 and take advantage of this main belt asteroid at opposition.

Asteroid 14 Irene in January 2021. Credit: Pete Lawrence

Asteroid 14 Irene reaches opposition in January as it tracks across the northern part of the constellation of Cancer, passing just to the south of mag. +4.0 Iota (ι) Cancri.

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At 00:00 UT on 1 January, Irene is located 1.5˚ northwest of mag. +5.4 Nu (ν) Cancri. From here it tracks northwest, passing 1.5˚ south of Rho1 (ρ1) Cancri and Rho2 (ρ2) Cancri between 7-12 January.

These stars are of mag. +6.0 and +5.2 respectively. (As an aside, Rho1, or 55 Cancri, is a fascinating star located 41 lightyears from Earth and known to have at least five exoplanets in orbit around it.)

Irene passes just over a degree south of Iota Cancri on 16/17 January, ending the month 3.5˚ west and a fraction north of this star.

Its brightness increases slowly over the month, from mag. +9.9 on the 1st up to +9.3 on the 23rd, dipping slightly to +9.4 by the month’s close.

Opposition occurs on 24 January when Irene lies 2.316 AU from the Sun and 1.340 AU from Earth.

What is Asteroid 14 Irene?

A 3D model of Asteroid 14 Irene. Credit: Astronomical Institute of the Charles University: Josef Ďurech, Vojtěch Sidorin
A 3D model of Asteroid 14 Irene. Credit: Astronomical Institute of the Charles University: Josef Ďurech, Vojtěch Sidorin

Irene is a large body orbiting within the main asteroid belt of our Solar System. It has tri-ellipsoidal dimensions of 167km x 153km x 139km and is a dark siliceous, or S-type asteroid, with an albedo – a measure of a body’s reflectivity – of 0.16.

Irene takes 4.16 years to orbit the Sun and rotates on its axis once every 15.1 hours. Its orbital distance from the Sun varies from 3.02 AU at aphelion to 2.15 AU at perihelion.

From Earth, its apparent magnitude can vary from a favourable +8.9 to +12.3.

This month’s +9.3 opposition magnitude presents an excellent opportunity to spot it. Binoculars will show it, but a small scope will give a better view.

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Pete Lawrence is an experienced astronomer and a co-host of The Sky at Night. This guide originally appeared in the January 2021 issue of BBC Sky at Night Magazine.