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NSF-DOE Vera C. Rubin Observatory Observations of Interstellar Comet 3I/ATLAS (C/2025 N1)

Publication ,  Journal Article
Chandler, CO; Bernardinelli, PH; Jurić, M; Singh, D; Hsieh, HH; Sullivan, I; Jones, RL; Kurlander, JA; Vavilov, D; Eggl, S; Holman, M; Inno, L ...
Published in: The Astrophysical Journal Letters
April 20, 2026

We report on the observation and measurement of astrometry, photometry, morphology, and activity of the interstellar object 3I/ATLAS, also designated C/2025 N1 (ATLAS) with the NSF-DOE Vera C. Rubin Observatory. Comet 3I/ATLAS, the third known interstellar object, was discovered on UT 2025 July 1. Rubin Observatory had coincidentally collected images of the object’s region of the sky during routine commissioning. Facilitated by Rubin’s high resolution and large aperture, we successfully recovered object detections from Rubin observations spanning UT 2025 June 21 (10 days before discovery, when 3I/ATLAS was 4.5 au from the Sun) through the date of discovery, and we acquired additional images through UT 2025 July 20 as part of commissioning. We measure on-sky locations of 3I/ATLAS in Rubin bands, with a typical precision of ∼70 mas, and briefly describe the reason this is coarser than our measured static source astrometric precision of ∼3 mas in Rubin images. We measure magnitudes of 3I/ATLAS photometry at ∼0.01 mag precision, detecting no short-term photometric variability above 0.01 mag. We derive an estimated near-nucleus dust-to-nucleus scattering cross-sectional ratio of  ≳ 13 on UT 2025 July 2 based on Rubin photometry and an upper limit nucleus size computed from Hubble Space Telescope observations. We find Rubin colors of  −   =  (0.657 ± 0.013) mag,  −   =  (0.235 ± 0.018) mag,  −   = (0.147 ±  0.042) mag, and  −   =  (0.047 ± 0.052) mag. These data represent the earliest observations of this object by a large (≳8 m class) telescope and illustrate the type of measurements (and discoveries) Rubin’s Legacy Survey of Space and Time will provide after it begins in early 2026.

Duke Scholars

Published In

The Astrophysical Journal Letters

DOI

EISSN

2041-8213

ISSN

2041-8205

Publication Date

April 20, 2026

Volume

1001

Issue

2

Start / End Page

L35 / L35

Publisher

American Astronomical Society

Related Subject Headings

  • Astronomy & Astrophysics
  • 5109 Space sciences
  • 5101 Astronomical sciences
 

Citation

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Chandler, C. O., Bernardinelli, P. H., Jurić, M., Singh, D., Hsieh, H. H., Sullivan, I., … Zhou, C. (2026). NSF-DOE Vera C. Rubin Observatory Observations of Interstellar Comet 3I/ATLAS (C/2025 N1). The Astrophysical Journal Letters, 1001(2), L35–L35. https://doi.org/10.3847/2041-8213/ae4b3a
Chandler, Colin Orion, Pedro H. Bernardinelli, Mario Jurić, Devanshi Singh, Henry H. Hsieh, Ian Sullivan, R Lynne Jones, et al. “NSF-DOE Vera C. Rubin Observatory Observations of Interstellar Comet 3I/ATLAS (C/2025 N1).” The Astrophysical Journal Letters 1001, no. 2 (April 20, 2026): L35–L35. https://doi.org/10.3847/2041-8213/ae4b3a.
Chandler CO, Bernardinelli PH, Jurić M, Singh D, Hsieh HH, Sullivan I, et al. NSF-DOE Vera C. Rubin Observatory Observations of Interstellar Comet 3I/ATLAS (C/2025 N1). The Astrophysical Journal Letters. 2026 Apr 20;1001(2):L35–L35.
Chandler, Colin Orion, et al. “NSF-DOE Vera C. Rubin Observatory Observations of Interstellar Comet 3I/ATLAS (C/2025 N1).” The Astrophysical Journal Letters, vol. 1001, no. 2, American Astronomical Society, Apr. 2026, pp. L35–L35. Crossref, doi:10.3847/2041-8213/ae4b3a.
Chandler CO, Bernardinelli PH, Jurić M, Singh D, Hsieh HH, Sullivan I, Jones RL, Kurlander JA, Vavilov D, Eggl S, Holman M, Spoto F, Schwamb ME, MacArthur LA, Makadia R, Micheli M, Heinze A, Christensen EJ, Beebe W, Roodman A, Lim K-T, Jenness T, Bosch J, Smart BM, Bellm E, MacBride S, Rawls ML, Greenstreet S, Slater C, Ivezić Ž, Blum RD, Connolly A, Daues G, Gower M, Kalmbach JB, Bannister MT, Dones L, Dorsey RC, Farnocchia D, Fraser WC, Forbes JC, Fuentes C, Holt CE, Inno L, Jones GH, Knight MM, Lintott CJ, Lister T, Lupton R, Magbanua MJM, Malhotra R, Mueller BEA, Murtagh J, Pandey N, Reach WT, Samarasinha NH, Seligman DZ, Snodgrass C, Solontoi M, Szabó GM, Vereš P, White E, Womack M, Young LA, Allbery R, Anand S, Armellin R, Aubourg É, Avdellidou C, Azfar F, Bauer J, Bechtol K, Becker V, Belyakov M, Benecchi SD, Bertini I, Bodewits D, Boeshaar P, Bolin BT, Bose M, Boucaud A, Boufleur RC, Boutigny D, Bradshaw A, Braga-Ribas F, Bregeon J, Buchanan LE, Calabrese D, Camargo JIB, Caplar N, Carlin JL, Carry B, Carvajal JP, Ceballo R, Chiang H-F, Choi Y, Combet C, da Costa L, Cowan P, Crenshaw JF, Croft S, Ćuk M, Daly PN, D’Ammando F, Daruich F, Daubard G, Davenport JRA, Daylan T, Delgado J, Devillepoix HAR, Doherty PE, Donaldson A, Drass H, Deppe SJH, Dubois-Felsmann GP, Ferguson PS, Economou F, Eduardo MR, Sotuela Elorriaga I, Englert A, Karavakis E, Fanning K, Frissell MK, Fedorets G, Fernandes MB, Ferté A, Fisher-Levine M, Freytag ML, Fulle M, Gandhi P, Gates J, Gerdes DW, Gibbs AR, Gillan AF, Giordano Orsini M, Glanzman T, Goodenow I, Gomes-Júnior AR, Gorsuch MR, Granvik M, Guan W, Guy LP, Hammergren M, Hanushevsky A, Hernandez F, Herrold Ǎ, Hestroffer D, Hoblitt J, Megias Homar G, Hopkins MJ, Ieva S, Ingraham P, Irving DH, Jannuzi BT, Jee MJ, Jimenez D, Juramy C, Kahn SM, Kang Y, Kannawadi A, Kavelaars JJ, Kelley MSP, Kelkar K, Kelvin LS, Kotov I, Koumjian A, Kovács G, Krughoff KS, Kryszczyńska A, Kubánek P, Lage C, Lange TJ, Léget P-F, Le Guillou L, Levine B, Levine WG, Li ZC, Liang S, Licandro J, Lin 林 HW省, Lisse C, Lust NB, Lyttle RR, Mahabal AA, Mahlke M, Mainetti G, Mandelbaum R, Margheim SJ, Margoti G, Marshall P, Plazas Malagón AA, Marčeta D, Melita MD, Menanteau F, Meyers J, Mills D, Moniez M, Morales Marín CAL, Morato N, More S, Morrison CB, Mortensen K, Moulane Y, Mrakovčić K, Mueller F, Muñoz-Gutiérrez MA, Neal H, Newcomer FM, Nourbakhsh E, O’Connor P, Oldag D, Oldroyd WJ, O’Mullane W, Opitom C, Oszkiewicz D, Page GL, Patterson J, Patterson MT, Payne MJ, Pedersen EM, Peloton J, Pereira CL, Peterson JR, Pietrowicz SR, Podlewska-Gaca E, Polen R, Polin D, Pollek HMM, Qiu Y, Quint B, Rabus M, Ragozzine D, Rajagopal J, Ranabhat A, Reil K, Ribeiro T, Rice M, Ridgway ST, Ritz SM, Rivkin AS, Robinson JE, Rożek A, Rykoff E, Salazar Manzano LE, Salnikov A, Sánchez BO, Sanmartim D, Sarid G, Schambeau CA, Schindler RH, Schmidt SJ, Schumacher G, Schutt T, Scolnic D, Seaman R, Sebag J, Sedaghat N, Seron J, Shaw RA, Shugart A, Sick J, Singhal J, Siraj A, Sitarz MC, Snyder A, Sobhani S, Soldahl C, Spencer D, Stalder B, Stetzler S, Strauss A, Stubbs CW, Suberlak KL, Swinbank JD, Szigeti L, Taranu DS, Tauraso M, Thayer JG, Thomas S, Thornton A, Tonietti L, Toribio San Cipriano L, Trilling DE, Trujillo CA, Tsai T-W, Tucker DL, Turri M, Tyson T, Urbach EK, van Reeven W, Villarreal AS, Voutsinas S, Walter CW, Wang YD, Ward C, Warner M, West M, Whittaker E, Wong I, Wood-Vasey WM, Yang B, Ye 叶 Q泉, Yoachim P, Zanmar Sanchez R, Zhang J, Zhou C. NSF-DOE Vera C. Rubin Observatory Observations of Interstellar Comet 3I/ATLAS (C/2025 N1). The Astrophysical Journal Letters. American Astronomical Society; 2026 Apr 20;1001(2):L35–L35.
Journal cover image

Published In

The Astrophysical Journal Letters

DOI

EISSN

2041-8213

ISSN

2041-8205

Publication Date

April 20, 2026

Volume

1001

Issue

2

Start / End Page

L35 / L35

Publisher

American Astronomical Society

Related Subject Headings

  • Astronomy & Astrophysics
  • 5109 Space sciences
  • 5101 Astronomical sciences