A fresh study of the Kuiper Belt’s structure has revived that far-out question, pointing to a possible Earth-sized ...

Astronomers have identified a small but significant possibility that a Neptune-sized planet is quietly orbiting within the ...

Over the past seven decades, thousands of sophisticated spacecraft have been launched on ambitious missions to look down on ...

It will be a while before you can see it for yourself, however. Halley’s comet was last visible from Earth in 1986, meaning ...

Two bright green comets are streaming through the skies and are visible to skygazers in the Northern Hemisphere. Both hail ...

Voyager 1, launched in 1977, has traveled farther than any spacecraft in human history. After more than four decades of silent endurance through space, it now sails beyond the orbit of the outer ...

A new study suggests yet another theory for a possible extra planet in our solar system, likely of a size between Mercury and ...

(CNN) — The search for an unknown planet in our solar system has inspired astronomers for more than a century. Now, a recent study suggests a potential new candidate, which the paper’s authors have ...

Portal’s heat exchanger thruster, known as Flare, fires up during a test in a vacuum chamber. (Portal Space Systems Photo) Bothell, Wash.-based Portal Space Systems says it has successfully tested its ...

3I/ATLAS likely weighs more than 33 billion tons. The interstellar object hurtling toward the inner solar system, where Earth is located, is much larger than previously thought, astronomers say. A ...

The methane gas may constitute a rarefied atmosphere, or it may come from erupting plumes on Makemake’s surface.

Anyone hungry for the icy crunch of a Pluto -like body? No? Well, one nearby white dwarf is going all in on a Pluto-esque ...