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

2025/07/17 by Colin Orion Chandler, Pedro H. Bernardinelli, Chandler, Colin Orion +554 · 15 voices · 9 citations
Physics and Astronomy · #Astrophysics and Star Formation Studies #Astronomy and Astrophysical Research #Gamma-ray bursts and supernovae

paper · pdf · doi:10.3847/2041-8213/ae4b3a

Abstract

Abstract 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 ugrizy 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 grizy 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 η ≳ 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 g − r = (0.657 ± 0.013) mag, r − i = (0.235 ± 0.018) mag, i − z = (0.147 ± 0.042) mag, and z − y = (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.

Citations

• Nucleus and Postperihelion Activity of Interstellar Object 3I/ATLAS Observed by Hubble Space Telescope
• Hubble Space Telescope Observations of the Interstellar Interloper 3I/ATLAS
• Snapshot of a new interstellar comet: 3I/ATLAS has a red and featureless spectrum
• Interstellar comet 3I/ATLAS: discovery and physical description
• From a Different Star: 3I/ATLAS in the Context of the Ōtautahi–Oxford Interstellar Object Population Model
• Discovery and Preliminary Characterization of a Third Interstellar Object: 3I/ATLAS
• The Active Asteroids Citizen Science Program: Overview and First Results
• Predicting Interstellar Object Chemodynamics with Gaia
• The Astropy Project: Building an Open-science Project and Status of the v2.0 Core Package^*
• ASTROMETRY.NET: BLIND ASTROMETRIC CALIBRATION OF ARBITRARY ASTRONOMICAL IMAGES
• A theory of dust comets. 1. Model and equations

Cited by

• Intercepting 3I/ATLAS at Closest Approach to Jupiter with the Juno spacecraft
• A Search for Radio Technosignatures from Interstellar Object 3I/ATLAS with the Allen Telescope Array
• Future Dark Energy Constraints from Atomic Clocks
• Skykatana: a scalable framework to construct sky masks for the Vera Rubin Observatory and large astronomical surveys
• The Distribution of Earth-Impacting Interstellar Objects
• Cross-correlating Astrometric and Timing Residuals to Constrain Stochastic Gravitational-Wave Backgrounds
• Cosmological Implications of Thermodynamic Split Conjecture
• Thermodynamic Split Conjecture and an Observational Test for Cosmological Entropy
• Temporal Evolution of the Third Interstellar Comet 3I/ATLAS: Spin, Color, Spectra and Dust Activity

Discussions

• It's paper day! The first science paper with data from @vrubinobs.bsky.social's survey camera, the mighty LSSTCam, is a VERY quick turnaround of Rubin's observations thus far of interstellar comet 3I/ [bsky, 156 points, 5 comments]
• New paper on arXiv, analyzing Rubin Observatory data of interstellar object 3I/ATLAS. This is the first science paper with data from LSSTCam!!!!! arxiv.org/abs/2507.13409 [bsky, 61 points, 1 comments]
• So now I can talk about arxiv.org/abs/2507.13409 - First science results with the @vrubinobs.bsky.social LSSTCam! [bsky, 32 points, 3 comments]
• Today on the #arXiv: Chandler et al. 2025, "NSF-DOE Vera C. Rubin Observatory Observations of Interstellar Comet #3I/ATLAS (C/2025 N1)" - arxiv.org/abs/2507.13409 Confirming cometary activity signific [bsky, 30 points, 0 comments]
• What a way to kick off Rubin Observatory research - with a paper on 3I/Atlas! arxiv.org/pdf/2507.13409 [bsky, 27 points, 1 comments]
• Very cool update on 3I/ATLAS: the Vera Rubin Observatory (which hasn’t even got its survey going yet) has found images of the interstellar object going back to June 21, clearly showing a coma (that’s [bsky, 19 points, 1 comments]
• Not convinced that this image from the Vera Rubin Observatory made optimal use of the Simonyi Survey Telescope’s 9.6 square degree field of view, but I look forward to the LSST finding dozens more int [bsky, 15 points, 2 comments]
• 11/11 patch of sky, with north up and east to the left. Image credit: NSF/Rubin Observatory/Chandler et al. Science paper: “NSF-DOE Vera C. Rubin Observatory Observations of Interstellar Comet 3I/ATLA [bsky, 13 points, 2 comments]
• During the Science Verification and Validation phase of the @vrubinobs.bsky.social we were lucky to capture images of the 3I/ATLAS interstellar comet. After the announcement of the discovery we looked [bsky, 12 points, 1 comments]
• Vera C. Rubin Observatory Observations of Interstellar Comet 3I/Atlas [hn, 4 points, 0 comments]
• NSF-DOE Vera C. Rubin Observatory Observations of Interstellar Comet 3I/ATLAS (C/2025 N1): arxiv.org/abs/2507.13409 - the first 5 were made before it was discovered. [bsky, 3 points, 0 comments]
• The @vrubinobs.bsky.social observatory pretty much puts the nail in the coffin of any alternatives - it's not an ETI, it's not mechanical, it's a comet. arxiv.org/abs/2507.13409 ☄️🔭🦛 [bsky, 3 points, 1 comments]
• NSF-DOE Vera C. Rubin Observatory Observations of Interstellar Comet 3I/Atlas [hn, 2 points, 1 comments]
• Today on the # arXiv : Chandler et al. 2025, "NSF-DOE Vera C. Rubin Observatory Observations of Interstellar Comet # 3I /ATLAS (C/2025 N1)" - https:// arxiv.org/abs/2507.13409 Confirming cometary acti [mastodon, 0 points, 0 comments]
• Vera C. Rubin Observatory Observations of Interstellar Comet 3IATLAS arxiv.org/abs/2507.13409 [bsky, 0 points, 0 comments]

Related

• Palomar and Apache Point Spectrophotometry of Interstellar Comet 3I/ATLAS
• Near-Discovery Observations of Interstellar Comet 3I/ATLAS with the NASA Infrared Telescope Facility
• ATLAS Photometry of Interstellar Object 3I/ATLAS
• Snapshot of a new interstellar comet: 3I/ATLAS has a red and featureless spectrum
• Interstellar comet 3I/ATLAS: discovery and physical description