What telescope do I need to see Irene?

At magnitude 8.6, Irene is within reach of a 3-inch (80 mm) telescope from a moderate-Bortle site.

Irene — Asteroid in Ophiuchus

14 Irene

Magnitude 8.6^m Asteroid Ophiuchus Visible

Rendered preview of Irene from the Nightbase orrery, lit from the current Sun direction with the terminator visible.

Star Map 3D Solar System + List + Plan

Properties

Magnitude 8.6

Description

Type: Asteroid

Distance: 2.588 AU

Orbital Period: 1520.6 days

Diameter: 152 km

Greek goddess of peace; S-type; reaches mag 8.6 at perihelic oppositions, near the binocular limit.

Position & Identifiers

RA 17h 32m 29.5s

Dec -22° 44' 04.4"

Constellation Ophiuchus

Catalog Irene

Wikipedia

Physical Properties

Diameter 152 km

Mass 5.6e18 kg

Albedo 0.16 (16% reflected)

Rotation 15.0 hours

Angular Size 0.1″ (current)

Orbital Properties

Semi-major Axis 2.5879 AU (387.1 million km)

Eccentricity 0.1627

Inclination 9.13°

Orbital Period 4.16 years

Distance 1.433 AU (11.9 light-min)

Elongation 179.0° Near opposition

Brightness Forecast (next 12 months)

Apparent magnitude as Earth–asteroid distance changes through the year. The peak marks the brightest moment in the window — usually around opposition, when the asteroid is closest and fully illuminated.

Computed from JPL orbital elements via m = H + 5·log₁₀(r·Δ). Phase-function correction is omitted, so curves trace distance variation only — accurate within a few tenths for main-belt asteroids; coarse for fast-moving NEOs near Earth.