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Solar system
Neptune's moon, Triton

4.5 billion years, about the same age as Neptune


Solar system, in orbit around Neptune

Avg. distance from Neptune

354,759 km (219,965 mi)


2,700 km (1,700 mi)


2.14 x 1022 kg

Orbital period around Neptune

5.877 days. Triton orbits in the opposite direction to Neptune's rotation (called a retrograde rotation). In addition, the same side of Triton always faces Neptune.

Distinguishing features

Due to its retrograde rotation, Triton is believed to be a captured moon that was originally a Kuiper Belt object. Triton is a little larger than the dwarf planets Pluto and Eris, but resembles Pluto in its composition. Knowledge of surface details comes from the Voyager 2 encounter in 1989. Images show a relatively flat surface with rocky outcroppings and canyons, active geyser-like eruptions, but few impact craters.

Neptune's moon, Triton

Enlarge Image


"Fast Facts: Neptune's moon, Triton" is a table that lists the moon's age, location, average distance from Neptune, diameter, orbital period around Neptune, mass, and distinguishing features. A picture of Triton is included.

Printer-friendly web page
Adaptable, at teacher's discretion
How to use in the classroom

Use this resource as:

A source of information. Read the table to find out about this object.

A large-number recognition and ordering activity. Have students review several Fast Fact moon tables, including this one. Have students read the tables to find each object's mass. Then ask them to arrange the objects according to their mass, from smallest to largest. Students also can arrange the objects according to their diameter.

A math activity. Use Newton's law of gravitation, the distance between Io and Jupiter, and the masses of the two objects to determine the gravitational force between them. (Recommended for grades 10-12)

An inquiry tool. Have students write down questions they would like answered about the image and the information in the Fast Facts table.

An engagement tool. Involve students in a discussion.

Related materials

Amazing Space resources by topic: Solar system

HubbleSite: Press releases on Moons