Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2025 July 7
A drawing of our Solar System shows the orbits of 
Jupiter and interior planets. A white line shows the 
trajectory of passing comet 3I/ATLAS.
Please see the explanation for more detailed information.

Interstellar Comet 3I/ATLAS
Image Credit: NASA, JPL-Caltech

Explanation: It came from outer space. An object from outside our Solar System is now passing through at high speed. Classified as a comet because of its gaseous coma, 3I/ATLAS is only the third identified macroscopic object as being so alien. The comet's trajectory is shown in white on the featured map, where the orbits of Jupiter, Mars, and Earth are shown in gold, red, and blue. Currently Comet 3I/ATLAS is about the distance of Jupiter from the Sun -- but closing, with its closest approach to our Sun expected to be within the orbit of Mars in late October. Expected to pass near both Mars and Jupiter, 3I/ATLAS is not expected to pass close to the Earth. The origin of Comet 3I/ATLAS remains unknown. Although initial activity indicates a relatively normal comet, future observations about 3I/ATLAS' composition and nature will surely continue.

Piece it All Together: Astronomy Puzzle of the Day
Tomorrow's picture: stellar sisters


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