Discovery and Preliminary Characterization of a Third Interstellar Object: 3I/ATLAS
We report initial observations aimed at the characterization of a third interstellar object. This object, 3I/ATLAS or C/2025 N1 (ATLAS), was discovered on 2025 July 1 UT and has an orbital eccentricity of e ∼ 6.1, perihelion of q ∼ 1.36 au, inclination of ∼175°, and hyperbolic velocity of V _∞ ∼ ...
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2025-01-01
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| author | Darryl Z. Seligman Marco Micheli Davide Farnocchia Larry Denneau John W. Noonan Henry H. Hsieh Toni Santana-Ros John Tonry Katie Auchettl Luca Conversi Maxime Devogèle Laura Faggioli Adina D. Feinstein Marco Fenucci Marin Ferrais Tessa Frincke Michael Gillon Olivier R. Hainaut Kyle Hart Andrew Hoffman Carrie E. Holt Willem B. Hoogendam Mark E. Huber Emmanuel Jehin Theodore Kareta Jacqueline V. Keane Michael S. P. Kelley Tim Lister Kathleen Mandt Jean Manfroid Dušan Marčeta Karen J. Meech Mohamed Amine Miftah Marvin Morgan Francisco Ocaña Eloy Peña-Asensio Benjamin J. Shappee Robert J. Siverd Aster G. Taylor Michael A. Tucker Richard Wainscoat Robert Weryk James J. Wray Atsuhiro Yaginuma Bin Yang Quanzhi Ye Qicheng Zhang |
| author_facet | Darryl Z. Seligman Marco Micheli Davide Farnocchia Larry Denneau John W. Noonan Henry H. Hsieh Toni Santana-Ros John Tonry Katie Auchettl Luca Conversi Maxime Devogèle Laura Faggioli Adina D. Feinstein Marco Fenucci Marin Ferrais Tessa Frincke Michael Gillon Olivier R. Hainaut Kyle Hart Andrew Hoffman Carrie E. Holt Willem B. Hoogendam Mark E. Huber Emmanuel Jehin Theodore Kareta Jacqueline V. Keane Michael S. P. Kelley Tim Lister Kathleen Mandt Jean Manfroid Dušan Marčeta Karen J. Meech Mohamed Amine Miftah Marvin Morgan Francisco Ocaña Eloy Peña-Asensio Benjamin J. Shappee Robert J. Siverd Aster G. Taylor Michael A. Tucker Richard Wainscoat Robert Weryk James J. Wray Atsuhiro Yaginuma Bin Yang Quanzhi Ye Qicheng Zhang |
| author_sort | Darryl Z. Seligman |
| collection | DOAJ |
| description | We report initial observations aimed at the characterization of a third interstellar object. This object, 3I/ATLAS or C/2025 N1 (ATLAS), was discovered on 2025 July 1 UT and has an orbital eccentricity of e ∼ 6.1, perihelion of q ∼ 1.36 au, inclination of ∼175°, and hyperbolic velocity of V _∞ ∼ 58 km s ^−1 . We report deep stacked images obtained using the Canada–France–Hawaii Telescope and the Very Large Telescope that resolve a compact coma. Using images obtained from several smaller ground-based telescopes, we find minimal light-curve variation for the object over a ∼4 day time span. The visible/near-infrared spectral slope of the object is 17.1% ± 0.2%/100 nm, comparable to other interstellar objects and primitive solar system small bodies (comets and D-type asteroids). Moreover, 3I/ATLAS will be observable through early 2025 September, then unobservable by Earth-based observatories near perihelion due to low solar elongation. It will be observable again from the ground in late 2025 November. Although this limitation unfortunately prohibits detailed Earth-based observations at perihelion when the activity of 3I/ATLAS is likely to peak, spacecraft at Mars could be used to make valuable observations at this time. |
| format | Article |
| id | doaj-art-199ea04ce5af4ff2b813547fe99c9930 |
| institution | DOAJ |
| issn | 2041-8205 |
| language | English |
| publishDate | 2025-01-01 |
| publisher | IOP Publishing |
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| series | The Astrophysical Journal Letters |
| spelling | doaj-art-199ea04ce5af4ff2b813547fe99c99302025-08-20T03:02:52ZengIOP PublishingThe Astrophysical Journal Letters2041-82052025-01-019892L3610.3847/2041-8213/adf49aDiscovery and Preliminary Characterization of a Third Interstellar Object: 3I/ATLASDarryl Z. Seligman0https://orcid.org/0000-0002-0726-6480Marco Micheli1https://orcid.org/0000-0001-7895-8209Davide Farnocchia2https://orcid.org/0000-0003-0774-884XLarry Denneau3https://orcid.org/0000-0002-7034-148XJohn W. Noonan4https://orcid.org/0000-0003-2152-6987Henry H. Hsieh5https://orcid.org/0000-0001-7225-9271Toni Santana-Ros6https://orcid.org/0000-0002-0143-9440John Tonry7https://orcid.org/0000-0003-2858-9657Katie Auchettl8https://orcid.org/0000-0002-4449-9152Luca Conversi9https://orcid.org/0000-0002-6710-8476Maxime Devogèle10https://orcid.org/0000-0002-6509-6360Laura Faggioli11https://orcid.org/0000-0002-5447-432XAdina D. Feinstein12https://orcid.org/0000-0002-9464-8101Marco Fenucci13https://orcid.org/0000-0002-7058-0413Marin Ferrais14https://orcid.org/0000-0002-0535-652XTessa Frincke15https://orcid.org/0009-0000-4697-5450Michael Gillon16https://orcid.org/0000-0003-1462-7739Olivier R. Hainaut17https://orcid.org/0000-0001-6952-9349Kyle Hart18https://orcid.org/0009-0003-2390-2840Andrew Hoffman19https://orcid.org/0000-0002-8732-6980Carrie E. Holt20https://orcid.org/0000-0002-4043-6445Willem B. Hoogendam21https://orcid.org/0000-0003-3953-9532Mark E. Huber22https://orcid.org/0000-0003-1059-9603Emmanuel Jehin23https://orcid.org/0000-0001-8923-488XTheodore Kareta24https://orcid.org/0000-0003-1008-7499Jacqueline V. Keane25https://orcid.org/0000-0002-2021-1863Michael S. P. Kelley26https://orcid.org/0000-0002-6702-7676Tim Lister27https://orcid.org/0000-0002-3818-7769Kathleen Mandt28https://orcid.org/0000-0001-8397-3315Jean Manfroid29https://orcid.org/0000-0002-6930-2205Dušan Marčeta30https://orcid.org/0000-0003-4706-4602Karen J. Meech31https://orcid.org/0000-0002-2058-5670Mohamed Amine Miftah32https://orcid.org/0009-0003-1220-6532Marvin Morgan33https://orcid.org/0000-0003-4022-6234Francisco Ocaña34https://orcid.org/0000-0002-9836-3285Eloy Peña-Asensio35https://orcid.org/0000-0002-7257-2150Benjamin J. Shappee36https://orcid.org/0000-0003-4631-1149Robert J. Siverd37https://orcid.org/0000-0001-5016-3359Aster G. Taylor38https://orcid.org/0000-0002-0140-4475Michael A. Tucker39https://orcid.org/0000-0002-2471-8442Richard Wainscoat40https://orcid.org/0000-0002-1341-0952Robert Weryk41https://orcid.org/0000-0002-0439-9341James J. Wray42https://orcid.org/0000-0001-5559-2179Atsuhiro Yaginuma43https://orcid.org/0009-0001-9538-1971Bin Yang44https://orcid.org/0000-0002-5033-9593Quanzhi Ye45https://orcid.org/0000-0002-4838-7676Qicheng Zhang46https://orcid.org/0000-0002-6702-191XDepartment of Physics and Astronomy, Michigan State University , East Lansing, MI 48824, USA ; dzs@msu.eduESA NEO Coordination Centre , Largo Galileo Galilei 1, I-00044 Frascati (RM), ItalyJet Propulsion Laboratory, California Institute of Technology , 4800 Oak Grove Dr., Pasadena, CA 91109, USAInstitute for Astronomy, University of Hawaii , 2680 Woodlawn Drive, Honolulu, HI 96822, USADepartment of Physics, Auburn University , Edmund C. Leach Science Center, Auburn, AL 36849, USAPlanetary Science Institute , 1700 East Fort Lowell Rd., Suite 106, Tucson, AZ 85719, USADepartamento de Física, Ingeniería de Sistemas y Teoría de la Señal, Universidad de Alicante , Carr. San Vicente del Raspeig, s/n, 03690 San Vicente del Raspeig, Alicante, Spain; Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (UB) , c. Martí Franquès, 1, 08028 Barcelona, Catalonia, SpainInstitute for Astronomy, University of Hawaii , 2680 Woodlawn Drive, Honolulu, HI 96822, USASchool of Physics, University of Melbourne , Parkville, VIC 3010, Australia; Department of Astronomy and Astrophysics, University of California , Santa Cruz, CA 93105, USAESA NEO Coordination Centre , Largo Galileo Galilei 1, I-00044 Frascati (RM), ItalyESA NEO Coordination Centre , Largo Galileo Galilei 1, I-00044 Frascati (RM), ItalyESA NEO Coordination Centre , Largo Galileo Galilei 1, I-00044 Frascati (RM), ItalyDepartment of Physics and Astronomy, Michigan State University , East Lansing, MI 48824, USA ; dzs@msu.eduESA NEO Coordination Centre , Largo Galileo Galilei 1, I-00044 Frascati (RM), ItalyFlorida Space Institute, University of Central Florida , 12354 Research Parkway, Orlando, FL 32828, USADepartment of Physics and Astronomy, Michigan State University , East Lansing, MI 48824, USA ; dzs@msu.eduAstrobiology Research Unit, Université de Liège , 4000 Liège, BelgiumEuropean Southern Observatory , Karl-Schwarzschild-St. 2, 85748 Garching-bei-München, GermanyInstitute for Astronomy, University of Hawaii , 2680 Woodlawn Drive, Honolulu, HI 96822, USAInstitute for Astronomy, University of Hawaii , 2680 Woodlawn Drive, Honolulu, HI 96822, USALas Cumbres Observatory , 6740 Cortona Drive, Suite 102, Goleta, CA 93117, USAInstitute for Astronomy, University of Hawaii , 2680 Woodlawn Drive, Honolulu, HI 96822, USAInstitute for Astronomy, University of Hawaii , 2680 Woodlawn Drive, Honolulu, HI 96822, USASpace sciences, Technologies & Astrophysics Research (STAR) Institute Université de Liége 4000 Liege , BelgiumDept. of Astrophysics and Planetary Science, Villanova University , Villanova, PA, USA; Lowell Observatory , 1400 W Mars Hill Rd, Flagstaff, AZ 86001, USAU.S. National Science Foundation , 2415 Eisenhower Avenue, Alexandria, VA 22314, USADepartment of Astronomy, University of Maryland , College Park, MD 20742-0001, USALas Cumbres Observatory , 6740 Cortona Drive, Suite 102, Goleta, CA 93117, USANASA Goddard Space Flight Center , Greenbelt, MD 20771, USASpace sciences, Technologies & Astrophysics Research (STAR) Institute Université de Liége 4000 Liege , BelgiumDepartment of Astronomy, Faculty of Mathematics, University of Belgrade , SerbiaInstitute for Astronomy, University of Hawaii , 2680 Woodlawn Drive, Honolulu, HI 96822, USASpace sciences, Technologies & Astrophysics Research (STAR) Institute Université de Liége 4000 Liege , Belgium; Cadi Ayyad University (UCA) , Oukaimeden Observatory (OUCA), Faculté des Sciences Semlalia (FSSM), High Energy Physics, Astrophysics and Geoscience Laboratory (LPHEAG), Marrakech, MoroccoDepartment of Physics, University of California , Santa Barbara, Santa Barbara, CA 93106, USAESA NEO Coordination Centre , Largo Galileo Galilei 1, I-00044 Frascati (RM), ItalyDepartment of Aerospace Science and Technology , Politecnico di Milano, Via La Masa 34, 20156 Milano, ItalyInstitute for Astronomy, University of Hawaii , 2680 Woodlawn Drive, Honolulu, HI 96822, USAInstitute for Astronomy, University of Hawaii , 2680 Woodlawn Drive, Honolulu, HI 96822, USADept. of Astronomy, University of Michigan , Ann Arbor, MI 48109, USACenter for Cosmology & Astroparticle Physics, The Ohio State University , Columbus, OH, USA; Department of Astronomy, The Ohio State University , Columbus, OH, USAInstitute for Astronomy, University of Hawaii , 2680 Woodlawn Drive, Honolulu, HI 96822, USADepartment of Physics and Astronomy, The University of Western Ontario , 1151 Richmond Street, London, ON N6A 3K7, CanadaSchool of Earth and Atmospheric Sciences, Georgia Institute of Technology , 311 Ferst Drive, Atlanta, GA 30332, USADept. of Physics and Astronomy, Michigan State University , East Lansing, MI 48824, USAInstituto de Estudios Astrofísicos , Facultad de Ingeniería y Ciencias, Universidad Diego Portales, Santiago, ChileDepartment of Astronomy, University of Maryland , College Park, MD 20742-0001, USA; Center for Space Physics, Boston University , 725 Commonwealth Ave, Boston, MA 02215, USALowell Observatory , 1400 W Mars Hill Rd, Flagstaff, AZ 86001, USAWe report initial observations aimed at the characterization of a third interstellar object. This object, 3I/ATLAS or C/2025 N1 (ATLAS), was discovered on 2025 July 1 UT and has an orbital eccentricity of e ∼ 6.1, perihelion of q ∼ 1.36 au, inclination of ∼175°, and hyperbolic velocity of V _∞ ∼ 58 km s ^−1 . We report deep stacked images obtained using the Canada–France–Hawaii Telescope and the Very Large Telescope that resolve a compact coma. Using images obtained from several smaller ground-based telescopes, we find minimal light-curve variation for the object over a ∼4 day time span. The visible/near-infrared spectral slope of the object is 17.1% ± 0.2%/100 nm, comparable to other interstellar objects and primitive solar system small bodies (comets and D-type asteroids). Moreover, 3I/ATLAS will be observable through early 2025 September, then unobservable by Earth-based observatories near perihelion due to low solar elongation. It will be observable again from the ground in late 2025 November. Although this limitation unfortunately prohibits detailed Earth-based observations at perihelion when the activity of 3I/ATLAS is likely to peak, spacecraft at Mars could be used to make valuable observations at this time.https://doi.org/10.3847/2041-8213/adf49aInterstellar objectsAsteroidsCometsMeteors |
| spellingShingle | Darryl Z. Seligman Marco Micheli Davide Farnocchia Larry Denneau John W. Noonan Henry H. Hsieh Toni Santana-Ros John Tonry Katie Auchettl Luca Conversi Maxime Devogèle Laura Faggioli Adina D. Feinstein Marco Fenucci Marin Ferrais Tessa Frincke Michael Gillon Olivier R. Hainaut Kyle Hart Andrew Hoffman Carrie E. Holt Willem B. Hoogendam Mark E. Huber Emmanuel Jehin Theodore Kareta Jacqueline V. Keane Michael S. P. Kelley Tim Lister Kathleen Mandt Jean Manfroid Dušan Marčeta Karen J. Meech Mohamed Amine Miftah Marvin Morgan Francisco Ocaña Eloy Peña-Asensio Benjamin J. Shappee Robert J. Siverd Aster G. Taylor Michael A. Tucker Richard Wainscoat Robert Weryk James J. Wray Atsuhiro Yaginuma Bin Yang Quanzhi Ye Qicheng Zhang Discovery and Preliminary Characterization of a Third Interstellar Object: 3I/ATLAS The Astrophysical Journal Letters Interstellar objects Asteroids Comets Meteors |
| title | Discovery and Preliminary Characterization of a Third Interstellar Object: 3I/ATLAS |
| title_full | Discovery and Preliminary Characterization of a Third Interstellar Object: 3I/ATLAS |
| title_fullStr | Discovery and Preliminary Characterization of a Third Interstellar Object: 3I/ATLAS |
| title_full_unstemmed | Discovery and Preliminary Characterization of a Third Interstellar Object: 3I/ATLAS |
| title_short | Discovery and Preliminary Characterization of a Third Interstellar Object: 3I/ATLAS |
| title_sort | discovery and preliminary characterization of a third interstellar object 3i atlas |
| topic | Interstellar objects Asteroids Comets Meteors |
| url | https://doi.org/10.3847/2041-8213/adf49a |
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