Astronomy Picture of the Day

Explanation: Discovered on July 1with the NASA-funded ATLAS(Asteroid Terrestrial-impact Last AlertSystem) survey telescope in Rio Hurtado, Chile,3I/ATLAS is so designated as the third known interstellar objectto pass through our Solar System.It follows1I/ʻOumuamua in 2017 and the comet2I/Borisov in 2019. Also known asC/2025 N1, 3I/ATLAS is a comet.A teardrop-shaped cloud of dust, ejected from its icy nucleuswarmed by increasing sunlight, is seen in thissharp image from the HubbleSpace Telescope captured on July 21.Background stars are streaked in the exposure as Hubble trackedthe fastest cometever recorded on its journey toward the inner solar system.An analysisof the Hubble image indicates thesolid nucleus, hiddenfrom direct view, is likely less that 5.6 kilometers in diameter.This comet's interstellar origin isclear 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 inside the orbitaldistance of Mars.