Astronomy Picture of the Day

Explanation: Discovered on July 1with the NASA-funded ATLAS(Asteroid Terrestrial-impact Last Alert,System) survey telescope in Rio Hurtado, Chile,3I/ATLAS is so designated as the third known interstellar objectto pass through our Solar SystemIt follows1I/ʻOumuamua in 2017 and the comet2I/Borisov in 2019. Also known asC/2025 N1,3I/ATLAS is clearly a comet, its diffuse cometary coma,a cloud of gas and dust surrounding an icy nucleus, iseasily seen in these images from the largeGemini North telescope on Maunakea, Hawai‘i.The left panel tracks the comet as it moves across the sky againstfixed background stars in successive exposures.Three different filters were used, shown in red, green, and blue.In the right panel the multiple exposures are registered andcombined to form a single image of the comet.The comet's interstellar origin is alsoclear from its orbit,determined to be an eccentric, highly hyperbolic orbit that doesnot loop back around the Sun and will return3I/ATLASto interstellar space.Not a threat toplanet Earth,the inbound interstellar interloper is nowwithin the Jupiter's orbital distance of the Sun, while itsclosest approach to the Sun will bring it just within the orbitaldistance of Mars.