3I/ATLAS

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'''3I/ATLAS''', also known as '''C/2025 N1 (ATLAS)''' (previously '''A11pl3Z'''), is an inbound [[interstellar comet]] discovered by the [[Asteroid Terrestrial-impact Last Alert System]] station at [[Río Hurtado]], Chile, on 1 July 2025 when it was {{convert|4.5|AU|e6km e6mi|lk=in|abbr=unit}} from the [[Sun]] and moving at a relative speed of {{cvt|61|km/s|mi/s}}. It follows an unbound, [[hyperbolic trajectory]] around the Sun with an [[orbital eccentricity]] of {{val|6.30|0.15}}.<ref name="jpldata"/> It is the third interstellar object confirmed passing through the [[Solar System]], after [[1I/ʻOumuamua]] and [[2I/Borisov]].<ref name="UT-20250702"/>

'''3I/ATLAS''', also known as '''C/2025 N1 (ATLAS)''' and previously as '''A11pl3Z''', is an inbound [[interstellar comet]] discovered by the [[Asteroid Terrestrial-impact Last Alert System]] station at [[Río Hurtado]], Chile, on 1 July 2025 when it was {{convert|4.5|AU|e6km e6mi|lk=in|abbr=unit}} from the [[Sun]] and moving at a relative speed of {{cvt|61|km/s|mi/s}}. It follows an unbound, [[hyperbolic trajectory]] around the Sun with an [[orbital eccentricity]] of {{val|6.30|0.15}}.<ref name="jpldata"/> It is the third interstellar object confirmed passing through the [[Solar System]], after [[1I/ʻOumuamua]] and [[2I/Borisov]].<ref name="UT-20250702"/>

The size of 3I/ATLAS's [[comet nucleus|nucleus]] is uncertain because it is an active comet surrounded by a [[Coma (comet)|shell of reflective dust]].<ref name="Seligman2025"/> Estimates suggest the nucleus of 3I/ATLAS should be smaller than {{cvt|24|km|mi}} in diameter, which is the size it would have if all of the observed light came from the nucleus and none from the coma.<ref name="Seligman2025"/> 3I/ATLAS will come to [[perihelion]] on 29 October 2025, at a distance of {{convert|1.38 ± 0.02|AU|e6km e6mi|abbr=unit}} from the Sun.<ref name="jpldata"/> When far away from the Sun, the comet's [[hyperbolic excess velocity]] (<math>v_\infty</math>) will be {{cvt|58|km/s|mi/s}} with respect to the Sun.<ref name="Deen-vinf"/><ref name=vinf-perihelion/>{{efn|name=vinf-formula}}

The size of 3I/ATLAS's [[comet nucleus|nucleus]] is uncertain because it is an active comet surrounded by a [[Coma (comet)|shell of reflective dust]].<ref name="Seligman2025"/> Estimates suggest the nucleus of 3I/ATLAS should be smaller than {{cvt|24|km|mi}} in diameter, which is the size it would have if all of the observed light came from the nucleus and none from the coma.<ref name="Seligman2025"/> 3I/ATLAS will come to [[perihelion]] on 29 October 2025, at a distance of {{convert|1.38 ± 0.02|AU|e6km e6mi|abbr=unit}} from the Sun.<ref name="jpldata"/> When far away from the Sun, the comet's [[hyperbolic excess velocity]] (<math>v_\infty</math>) will be {{cvt|58|km/s|mi/s}} with respect to the Sun.<ref name="Deen-vinf"/><ref name=vinf-perihelion/>{{efn|name=vinf-formula}}