Rubin Planetarium Video - Trans-Neptunian Objects

A trans-Neptunian object (TNO) is any minor planet in the Solar System that orbits the Sun at a greater average distance than Neptune, i.e., it has semi-major axis greater than 30 astronomical units (AU). TNOs are made primarily of rock, as well as water and methane ice. Organic compounds, such as tholins, can give TNOs a reddish color. Like asteroids, TNOs can exist in a binary system where they move around a common center of mass that orbits the Sun.

Because they are so far from the Sun, TNOs are extremely faint and therefore hard to detect. The first TNO to be discovered was Pluto in 1930. The second one wasnʼt discovered until 1992. Since then, about 2,500 TNOs have been discovered. During its ten years of operation, it is estimated that LSST will discover about 40,000 TNOs. LSST will be much more successful at detecting TNOs than previous surveys because the telescope has a giant 8.4-meter mirror, which enables it to easily see faint objects. LSST is also surveying a large area of the sky.

Because TNOs are very far away from the Sun, they can take can take hundreds to thousands of years to complete one orbit. It is therefore necessary to have multiple observations of a TNO, spanning many years, to accurately determine its orbital path. By tracking the motions of TNOs, LSST will calculate the sizes and shapes of their orbits. LSST will also measure the brightness of each TNO so that its size can be calculated (larger asteroids reflect more sunlight and therefore appear brighter). And, by measuring its brightness in six filters, LSST will be able to determine the color and composition of an object. The orbital parameters, sizes, and compositions of all the TNOs will give astronomers information about the formation and history of the Solar System.


This animation presents Trans-Neptunian Objects (TNOs) in context with their location in the outer solar system. The TNOs are given reddish colorations consistent with resolved (Charon) and unresolved observations of this population of small bodies. In this video the TNOs are shown as a gravitationally-bound pair separated roughly by 100x their diameters, consistent with findings for many known sources in this region. Overall surface features are inspired by detailed observations of Charon by New Horizons.


We begin adjacent to Neptune before pulling out to greater distances. The Sun and the Milky Way are visible in the distance.


As we begin to fly to a TNO binary system, Neptuneʼs orbit line fades in to provide scale and orientation.


The first TNO in the binary system moves into view.


The second TNO appears.


We transition into a rotational motion around the TNO binary system.


The first TNO returns to close proximity with its partner, seen in the distance.

Additional References


Caltech-IPAC/LSST Project/NSF/AURA

Special Recognition

Data to Dome initiative

About the Video

Release date:April 11, 2023, 3:09 p.m.
Duration:02 m 26 s
Frame rate:30 fps

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