Snapshot of a new interstellar comet: 3I/ATLAS has a red and featureless spectrum

Fuente: arXiv
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Auteurs principaux: Opitom, Cyrielle, Snodgrass, Colin, Jehin, Emmanuel, Bannister, Michele T., Bufanda, Erica, Deam, Sophie E., Dorsey, Rosemary, Ferrais, Marin, Hmiddouch, Said, Knight, Matthew M., Kokotanekova, Rosita, Leicester, Brayden, Marsset, Michaël, Murphy, Brian, Okoth, Vincent, Ridden-Harper, Ryan, Donckt, Mathieu Vander, Ferellec, Léa, Hutsemekers, Damien, Lippi, Manuela, Manfroid, Jean, Benkhaldoun, Zouhair
Format: Preprint
Publié: 2025
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author Opitom, Cyrielle
Snodgrass, Colin
Jehin, Emmanuel
Bannister, Michele T.
Bufanda, Erica
Deam, Sophie E.
Dorsey, Rosemary
Ferrais, Marin
Hmiddouch, Said
Knight, Matthew M.
Kokotanekova, Rosita
Leicester, Brayden
Marsset, Michaël
Murphy, Brian
Okoth, Vincent
Ridden-Harper, Ryan
Donckt, Mathieu Vander
Ferellec, Léa
Hutsemekers, Damien
Lippi, Manuela
Manfroid, Jean
Benkhaldoun, Zouhair
author_facet Opitom, Cyrielle
Snodgrass, Colin
Jehin, Emmanuel
Bannister, Michele T.
Bufanda, Erica
Deam, Sophie E.
Dorsey, Rosemary
Ferrais, Marin
Hmiddouch, Said
Knight, Matthew M.
Kokotanekova, Rosita
Leicester, Brayden
Marsset, Michaël
Murphy, Brian
Okoth, Vincent
Ridden-Harper, Ryan
Donckt, Mathieu Vander
Ferellec, Léa
Hutsemekers, Damien
Lippi, Manuela
Manfroid, Jean
Benkhaldoun, Zouhair
contents The interstellar comet 3I/ATLAS is only the third interstellar object to be discovered. Pre-perihelion measurements provide a unique opportunity to study its activity and composition, which may alter as it is heated in the coming months. We provide an initial baseline from optical spectroscopic observations obtained only two days after discovery, using the MUSE instrument on the VLT on 2025 July 3, while 3I was at 4.47 au from the Sun and 3.46 au from the Earth. These observations confirm the cometary nature of 3I, and reveal a red coma with a spectral slope of $(18\pm4)\%/1000$~Å, redder than most Solar System comets but similar to the surface colour of some Solar System Trans-Neptunian Objects or Centaurs. We searched for but did not detect gas emission from C$_2$, NH$_2$, CN, and [OI], which is consistent with volatile non-detections for Solar System comets at this heliocentric distance. At present, the coma appears entirely dusty. Future observations of 3I as it comes closer to the Sun will provide an invaluable opportunity to witness the evolution of its activity, study its composition, test predictions of interstellar object population models, and compare 3I to Solar System comets.
format Preprint
id arxiv_https___arxiv_org_abs_2507_05226
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Snapshot of a new interstellar comet: 3I/ATLAS has a red and featureless spectrum
Opitom, Cyrielle
Snodgrass, Colin
Jehin, Emmanuel
Bannister, Michele T.
Bufanda, Erica
Deam, Sophie E.
Dorsey, Rosemary
Ferrais, Marin
Hmiddouch, Said
Knight, Matthew M.
Kokotanekova, Rosita
Leicester, Brayden
Marsset, Michaël
Murphy, Brian
Okoth, Vincent
Ridden-Harper, Ryan
Donckt, Mathieu Vander
Ferellec, Léa
Hutsemekers, Damien
Lippi, Manuela
Manfroid, Jean
Benkhaldoun, Zouhair
Earth and Planetary Astrophysics
Astrophysics of Galaxies
The interstellar comet 3I/ATLAS is only the third interstellar object to be discovered. Pre-perihelion measurements provide a unique opportunity to study its activity and composition, which may alter as it is heated in the coming months. We provide an initial baseline from optical spectroscopic observations obtained only two days after discovery, using the MUSE instrument on the VLT on 2025 July 3, while 3I was at 4.47 au from the Sun and 3.46 au from the Earth. These observations confirm the cometary nature of 3I, and reveal a red coma with a spectral slope of $(18\pm4)\%/1000$~Å, redder than most Solar System comets but similar to the surface colour of some Solar System Trans-Neptunian Objects or Centaurs. We searched for but did not detect gas emission from C$_2$, NH$_2$, CN, and [OI], which is consistent with volatile non-detections for Solar System comets at this heliocentric distance. At present, the coma appears entirely dusty. Future observations of 3I as it comes closer to the Sun will provide an invaluable opportunity to witness the evolution of its activity, study its composition, test predictions of interstellar object population models, and compare 3I to Solar System comets.
title Snapshot of a new interstellar comet: 3I/ATLAS has a red and featureless spectrum
topic Earth and Planetary Astrophysics
Astrophysics of Galaxies
url https://arxiv.org/abs/2507.05226