The interstellar comet 3I/ATLAS is barreling toward its closest point to the sun as perihelion looms on Oct. 29. How different will it look when it reappears on the other side?

Comet 3I/ATLAS will be closest to the Sun on October 29 and will be observable through telescopes. Here is how you can track it.

Surrounding our solar system is a natural and enigmatic cosmic shield called the heliosphere — and a new mission has launched to help astronomers better understand it. Created by the solar wind, a ...