The Origin of the Cluster of Local Interstellar Clouds

The interstellar medium within ≈15 pc of the Sun consists of a complex of 15 diffuse, partially ionized clouds. Located within the Local Bubble, these clouds, known as the Cluster of Local Interstellar Clouds (CLIC), constitute the interstellar environment impinging upon our heliosphere. While each...

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Main Authors: Catherine Zucker, Seth Redfield, Sara Starecheski, Ralf Konietzka, Jeffrey L. Linsky
Format: Article
Language:English
Published: IOP Publishing 2025-01-01
Series:The Astrophysical Journal
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Online Access:https://doi.org/10.3847/1538-4357/adc920
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author Catherine Zucker
Seth Redfield
Sara Starecheski
Ralf Konietzka
Jeffrey L. Linsky
author_facet Catherine Zucker
Seth Redfield
Sara Starecheski
Ralf Konietzka
Jeffrey L. Linsky
author_sort Catherine Zucker
collection DOAJ
description The interstellar medium within ≈15 pc of the Sun consists of a complex of 15 diffuse, partially ionized clouds. Located within the Local Bubble, these clouds, known as the Cluster of Local Interstellar Clouds (CLIC), constitute the interstellar environment impinging upon our heliosphere. While each individual cloud can be modeled with a distinct velocity vector, the complex demonstrates a coherent bulk motion suggestive of a common origin. Here, we examine two theories for the origin of the CLIC: that it formed due to an ionization front associated with nearby Strömgren spheres and/or due to a nearby supernova explosion that occurred within the pre-evacuated cavity of the Local Bubble. Tracing back the trajectory of the clouds, we disfavor a purely Strömgren sphere origin, given the CLIC’s position interior to the surface of the most significant nearby Strömgren sphere and its motion transverse to the sphere’s trajectory. Turning to a supernova origin, we model the formation of the CLIC assuming individual clouds have been swept up over time due to the expansion of a supernova remnant in its pressure-driven snowplow phase. We find that the 3D spatial-dynamical properties of the CLIC can be explained by the most recent supernova that exploded in the nearby Upper Centaurus Lupus cluster ≈1.2 Myr ago and propagated into an ambient density of n  ≈ 0.04 cm ^−3 . Our model predicts that the formation of the individual CLIC clouds occurred progressively over the past 1 Myr and offers a natural explanation for the observed distribution, column density, temperature, and magnetic field structure of the complex.
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spelling doaj-art-c8e674228db64f748533c01b5f6c58c02025-08-20T02:03:20ZengIOP PublishingThe Astrophysical Journal1538-43572025-01-0198615810.3847/1538-4357/adc920The Origin of the Cluster of Local Interstellar CloudsCatherine Zucker0https://orcid.org/0000-0002-2250-730XSeth Redfield1https://orcid.org/0000-0003-3786-3486Sara Starecheski2https://orcid.org/0009-0002-7155-6180Ralf Konietzka3https://orcid.org/0000-0001-8235-2939Jeffrey L. Linsky4https://orcid.org/0000-0003-4446-3181Center for Astrophysics ∣ Harvard & Smithsonian , 60 Garden St., Cambridge, MA 02138, USA ; catherine.zucker@cfa.harvard.edu; Space Telescope Science Institute , 3700 San Martin Drive, Baltimore, MD 21218, USAAstronomy Department and Van Vleck Observatory, Wesleyan University , Middletown, CT 06459, USAAstronomy Department and Van Vleck Observatory, Wesleyan University , Middletown, CT 06459, USA; Department of Physics, Sarah Lawrence College , Bronxville, NY 10708, USACenter for Astrophysics ∣ Harvard & Smithsonian , 60 Garden St., Cambridge, MA 02138, USA ; catherine.zucker@cfa.harvard.eduJILA, University of Colorado and NIST , Boulder, CO 80309-0440, USAThe interstellar medium within ≈15 pc of the Sun consists of a complex of 15 diffuse, partially ionized clouds. Located within the Local Bubble, these clouds, known as the Cluster of Local Interstellar Clouds (CLIC), constitute the interstellar environment impinging upon our heliosphere. While each individual cloud can be modeled with a distinct velocity vector, the complex demonstrates a coherent bulk motion suggestive of a common origin. Here, we examine two theories for the origin of the CLIC: that it formed due to an ionization front associated with nearby Strömgren spheres and/or due to a nearby supernova explosion that occurred within the pre-evacuated cavity of the Local Bubble. Tracing back the trajectory of the clouds, we disfavor a purely Strömgren sphere origin, given the CLIC’s position interior to the surface of the most significant nearby Strömgren sphere and its motion transverse to the sphere’s trajectory. Turning to a supernova origin, we model the formation of the CLIC assuming individual clouds have been swept up over time due to the expansion of a supernova remnant in its pressure-driven snowplow phase. We find that the 3D spatial-dynamical properties of the CLIC can be explained by the most recent supernova that exploded in the nearby Upper Centaurus Lupus cluster ≈1.2 Myr ago and propagated into an ambient density of n  ≈ 0.04 cm ^−3 . Our model predicts that the formation of the individual CLIC clouds occurred progressively over the past 1 Myr and offers a natural explanation for the observed distribution, column density, temperature, and magnetic field structure of the complex.https://doi.org/10.3847/1538-4357/adc920Diffuse interstellar cloudsInterstellar dynamicsSupernova remnants
spellingShingle Catherine Zucker
Seth Redfield
Sara Starecheski
Ralf Konietzka
Jeffrey L. Linsky
The Origin of the Cluster of Local Interstellar Clouds
The Astrophysical Journal
Diffuse interstellar clouds
Interstellar dynamics
Supernova remnants
title The Origin of the Cluster of Local Interstellar Clouds
title_full The Origin of the Cluster of Local Interstellar Clouds
title_fullStr The Origin of the Cluster of Local Interstellar Clouds
title_full_unstemmed The Origin of the Cluster of Local Interstellar Clouds
title_short The Origin of the Cluster of Local Interstellar Clouds
title_sort origin of the cluster of local interstellar clouds
topic Diffuse interstellar clouds
Interstellar dynamics
Supernova remnants
url https://doi.org/10.3847/1538-4357/adc920
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