The location of the solar system's outer boundary is a point of contention among astronomers. There are three possible candidates, which "all have merit." But which one is best?

An illustration of the solar system (not to scale), including the sun, inner rocky planets, asteroid belt, the outer gassy planets, and—beyond Neptune—the Kuiper belt and the Oort cloud.

NASA has revealed that they have sent a man-made machine further than they ever have before, and they said they made an odd ...

The answer depends on how you define coldest. Uranus boasts the lowest recorded planetary temperature in our solar system: about minus 370 degrees , according to University College London.

Many smaller outer solar system objects appear to have orbits that are aligned in certain mysterious ways; the simplest explanation is that their motions are influenced by another, as-yet-unseen ...

It's because the solar system is flat. ... Since we define acceleration as the rate of change of velocity, this ball must have an acceleration. Even if it's moving at a constant speed, ...

The curious minds at What If explore how the discovery of Kepler 22-b in our solar system would alter everything we know about space and life.

Temperatures there reach an astonishing 30,000-50,000 kelvin. There are a few ways you could define the edge of the Solar System – for instance, where the planets end, or at the Oort cloud, the ...

Now, however, Pluto and that part of the solar system has moved away from the backdrop of the Milky Way into a sparser region of the night sky. With its Hyper Suprime-Cam (HSC), Subaru has ...