What telescope do I need to see Itokawa?

At magnitude 19.0, Itokawa is a challenging target that needs at least an 8-inch (200 mm) telescope and dark skies.

Itokawa — Near-Earth Object in Taurus

25143 Itokawa, 1998 SF36

Magnitude 19.0^m NearEarthObject Taurus Visible

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Properties

Magnitude 19.0

Description

Type: Near-Earth Object

Distance: 1.324 AU

Orbital Period: 556.5 days

Diameter: 1 km

Features: 'Head' and 'body' lobes; smooth Muses Sea regolith pond; boulder-strewn highlands

Two-lobed contact-binary 'sea otter' shape (~535×294×209 m). Target of JAXA's Hayabusa mission, the first sample-return from an asteroid (samples returned 2010). Confirmed S(IV)-type composition matching ordinary chondrite meteorites — settled a long-standing question about asteroid–meteorite linkage. Low density (1.9 g/cm³) reveals it as a rubble-pile, not monolithic.

Position & Identifiers

RA 04h 00m 27.1s

Dec +20° 13' 30.6"

Constellation Taurus

Catalog Itokawa

Physical Properties

Diameter 1 km

Mass 3.51e10 kg

Albedo 0.23 (23% reflected)

Rotation 12.1 hours

Surface 'Head' and 'body' lobes; smooth Muses Sea regolith pond; boulder-strewn highlands

Angular Size 0.0″ (current)

Orbital Properties

Semi-major Axis 1.3241 AU (198.1 million km)

Eccentricity 0.2802

Inclination 1.62°

Orbital Period 556.5 days

Distance 2.589 AU (21.5 light-min)

Elongation 22.4° Near Sun

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.

Observing Tips

Visibility Large telescope only at close approach

Where to Look Near-Earth asteroid (Apollo group)

Notes Two-lobed contact-binary 'sea otter' shape (~535×294×209 m). Target of JAXA's Hayabusa mission, the first sample-return from an asteroid (samples returned 2010). Confirmed S(IV)-type composition matching ordinary chondrite meteorites — settled a long-standing question about asteroid–meteorite linkage. Low density (1.9 g/cm³) reveals it as a rubble-pile, not monolithic.