Local_Interstellar_Cloud

# Local Interstellar Cloud  **Microsim — three.js (Wikitube framework):** *Out to the nearest star (Solar System explorer)* <div class="wt-sim" data-src="https://wikitube-3d-microsims.netlify.app/solar/Solar_System.html?view=neighborhood&embed=1" data-title="Out to the nearest star (Solar System explorer)"></div> *The Solar System explorer locked on this article's state (`?view=neighborhood`); every object and population of the [[PORTAL_Solar_System|Solar System portal]] has its own state in the same scene.*  *Try: follow the ruler outward from the heliopause tick at 121 AU, past Sedna's aphelion, the Oort cloud at about 2,000 AU and the Hill sphere at about 200,000 AU, to Proxima Centauri at 4.25 light-years; set show to clouds and boundaries to leave only the Oort cloud points and the boundary shells; scroll out to the end of the ruler and keep in mind that the whole span is a small fraction of the cloud's width of about 30 light-years.* The **Local Interstellar Cloud** (LIC), informally the **Local Fluff**, is a warm, thin, partly ionized cloud of interstellar gas about 30 light-years across through which the [[Sun]] is currently moving.[^enc-astrobio][^frisch2011] It is one of a cluster of small warm clouds that sit inside the [[Local_Bubble|Local Bubble]], a much larger cavity of hotter and thinner gas, and it belongs to the very local [[Interstellar_medium|interstellar medium]] that begins where the [[Heliosphere|heliosphere]] ends.[^linsky2020egu][^jpl-neighborhood] Observations cannot yet say whether the Sun lies inside the cloud or in a transition zone between it and the neighbouring G cloud.[^linsky2019][^frisch2011] The cloud's gas is about as hot as the surface of the Sun, near 7,000 K, yet so thin that it holds only about 0.3 atoms per cubic centimetre.[^nasa2003][^jpl-neighborhood] It is also magnetized, strongly enough for its field to help shape the heliosphere.[^opher2009] The explorer at the top of this page cannot show the cloud. Its neighbourhood view is a ruler that ends at Proxima Centauri, 4.25 light-years out, and nothing beyond the Sun's own gravitational domain is drawn; the Local Interstellar Cloud is several times wider than that whole ruler. ## Structure The picture of the nearby gas comes mostly from absorption lines. Light from nearby stars passes through the clouds on its way to Earth, and each cloud imprints narrow absorption lines of ionized magnesium, iron and other atoms at its own Doppler velocity. Sorting these [[Spectral_line|spectral lines]] toward many stars into groups that share a common velocity vector, Redfield and Linsky identified about 15 distinct warm clouds within 15 parsecs of the Sun.[^redfield2008] The Local Interstellar Cloud is the one surrounding, or nearly surrounding, the Solar System; Linsky and colleagues reconstructed its three-dimensional shape from absorption along 62 lines of sight and found that four partly ionized clouds, the LIC, the G cloud, the Blue cloud and the Aql cloud, are in contact with the outer heliosphere.[^linsky2019] The cloud is denser than the gas around it. Its density of about 0.3 per cubic centimetre is below the average of about 0.5 for the interstellar medium of the [[Milky_Way|Milky Way]], but some six times that of the hot, thin gas of the Local Bubble, about 0.05 per cubic centimetre.[^jpl-neighborhood][^boulanger2000] For a sense of scale, the [[Atmosphere_of_Earth|atmosphere]] at 100 km altitude holds about 1.2 × 10¹³ molecules per cubic centimetre, some 40 trillion times more (derived).[^ussa1976] A temperature near 7,000 K therefore carries very little heat: the product of density and temperature, a measure of thermal pressure, is only about 2,000 K per cubic centimetre (derived).[^nasa2003] The Sun and the cloud move relative to each other. Frisch and colleagues estimate that the Sun entered the Local Interstellar Cloud within the past 10,000 years, and a later analysis puts its complete exit no more than 1,900 years in the future.[^frisch2011][^linsky2020] The motion of the local clouds points back to the Scorpius–Centaurus association, a group of young, massive stars whose winds and supernovae are thought to have driven the gas outward.[^frisch2011] The cloud may also leave a trace on [[Earth]]. In 2019 Koll and colleagues reported [[Iron|iron]]-60, a radioactive [[Isotope|isotope]] made in supernovae, in recent Antarctic snow, and suggested that the influx comes from the cloud through which the Sun is now passing.[^koll2019] With a [[Half-life|half-life]] of about 2.6 million years, any iron-60 in fresh snow must have been produced in the last few million years.[^rugel2009] ## Interaction with solar magnetic field The Sun's wind and magnetic field hold the cloud's charged particles off. The [[Solar_wind|solar wind]] inflates the heliosphere inside the surrounding gas, and the wind and the Sun's field together shield [[Earth]] from most of what the cloud contains.[^nasa2003] The boundary itself, the [[Heliopause|heliopause]], was crossed by [[Voyager_1|Voyager 1]] in August 2012 and by Voyager 2 in November 2018, and both probes now sample the interstellar plasma just outside it.[^jpl-voyager][^linsky2020egu] The cloud's magnetic field shapes the heliosphere in turn. In 2009 Opher and colleagues compared models of the heliosphere with the distances at which the two Voyagers met the termination shock and found that the interstellar field just outside must be stronger than assumed, about 370–550 picotesla (3.7–5.5 microgauss) rather than the earlier 180–250 picotesla, and strongly tilted.[^opher2009] A field of that strength adds to the cloud's pressure and may be what has kept it intact inside the hot Local Bubble.[^opher2009] NASA's Interstellar Boundary Explorer (IBEX), launched in 2008, maps the interaction from Earth orbit by collecting energetic neutral atoms that form where solar wind protons exchange charge with neutral interstellar atoms. Its first all-sky maps in 2009 showed an unexpected narrow ribbon of enhanced emission, which appears to be ordered by the interstellar magnetic field draped over the heliosphere.[^mccomas2009] Together with the Voyager data, these maps constrain the direction of the interstellar field around the Sun. ## See also - [[Local_Bubble]] - [[Interstellar_medium]] - [[Heliosphere]] - [[Orion_Arm]] - [[Alpha_Centauri]] - [[Voyager_1]] - Gould Belt · Perseus Arm · List of nearest stars and brown dwarfs ## References [^enc-astrobio]: Gargaud, M.; et al. (eds.) (2011). "Local Interstellar Cloud". *Encyclopedia of Astrobiology*. Springer, pp. 1526–1527. https://doi.org/10.1007/978-3-642-11274-4_1460 [^frisch2011]: Frisch, P. C.; Redfield, S.; Slavin, J. D. (2011). "The interstellar medium surrounding the Sun". *Annual Review of Astronomy and Astrophysics* 49: 237–279. https://doi.org/10.1146/annurev-astro-081710-102613 [^linsky2020egu]: Linsky, J. (2020). "What lies immediately outside of the heliosphere in the very local interstellar medium (VLISM): morphology of the Local Interstellar Cloud, its hydrogen hole, Strömgren shells, and ⁶⁰Fe accretion". *EGU General Assembly 2020*, abstract EGU2020-1410. https://doi.org/10.5194/egusphere-egu2020-1410 [^jpl-neighborhood]: NASA/JPL Interstellar Probe (2000). "Our local galactic neighborhood". http://interstellar.jpl.nasa.gov/interstellar/probe/introduction/neighborhood.html [^linsky2019]: Linsky, J. L.; Redfield, S.; Tilipman, D. (2019). "The interface between the outer heliosphere and the inner local ISM: morphology of the Local Interstellar Cloud, its hydrogen hole, Strömgren shells, and ⁶⁰Fe accretion". *The Astrophysical Journal* 886: 41. https://doi.org/10.3847/1538-4357/ab498a [^nasa2003]: NASA Science (6 January 2003). "Near-Earth supernovas". https://science.nasa.gov/science-news/science-at-nasa/2003/06jan_bubble [^opher2009]: Opher, M.; Alouani Bibi, F.; Toth, G.; Richardson, J. D.; Izmodenov, V. V.; Gombosi, T. I. (2009). "A strong, highly-tilted interstellar magnetic field near the Solar System". *Nature* 462: 1036–1038. https://doi.org/10.1038/nature08567 [^redfield2008]: Redfield, S.; Linsky, J. L. (2008). "The structure of the local interstellar medium. IV. Dynamics, morphology, physical properties, and implications of cloud-cloud interactions". *The Astrophysical Journal* 673: 283–314. https://doi.org/10.1086/524002 [^boulanger2000]: Boulanger, F.; Cox, P.; Jones, A. P. (2000). "Course 7: Dust in the interstellar medium". In Casoli, F.; Lequeux, J.; David, F. (eds.), *Infrared Space Astronomy, Today and Tomorrow*. Les Houches Summer School 70, p. 251. Bibcode 2000isat.conf..251B. [^ussa1976]: NOAA, NASA and U.S. Air Force (1976). *U.S. Standard Atmosphere, 1976*. NOAA-S/T 76-1562, pp. 210–215. [^linsky2020]: Linsky, J. L.; Redfield, S.; Wood, B. E. (2020). "New results concerning the environment of the heliosphere, nearby interstellar clouds, and physical processes in the inter-cloud medium". *Journal of Physics: Conference Series* 1620: 012010. https://doi.org/10.1088/1742-6596/1620/1/012010 [^koll2019]: Koll, D.; Korschinek, G.; Faestermann, T.; Gómez-Guzmán, J. M.; Kipfstuhl, S.; Merchel, S.; et al. (2019). "Interstellar ⁶⁰Fe in Antarctica". *Physical Review Letters* 123: 072701. https://doi.org/10.1103/PhysRevLett.123.072701 [^rugel2009]: Rugel, G.; Faestermann, T.; Knie, K.; et al. (2009). "New measurement of the ⁶⁰Fe half-life". *Physical Review Letters* 103: 072502. https://doi.org/10.1103/PhysRevLett.103.072502 [^jpl-voyager]: Jet Propulsion Laboratory. "Voyager – Interstellar mission". https://voyager.jpl.nasa.gov/mission/interstellar-mission/ [^mccomas2009]: McComas, D. J.; Allegrini, F.; Bochsler, P.; et al. (2009). "Global observations of the interstellar interaction from the Interstellar Boundary Explorer (IBEX)". *Science* 326: 959–962. https://doi.org/10.1126/science.1180906 ## Further reading - NASA Science. "A breeze from the stars" (Science@NASA feature on the interstellar wind). - NASA Science. "Voyager makes an interstellar discovery" (Science@NASA feature on the Local Fluff's magnetic field). ## External links - NASA, Interstellar Boundary Explorer (IBEX) mission: https://science.nasa.gov/mission/ibex/ - NASA/JPL Voyager interstellar mission: https://voyager.jpl.nasa.gov/mission/interstellar-mission/ - Redfield, S.; Linsky, J. L., Colorado Local ISM kinematic model (2008): https://doi.org/10.1086/524002 ## Wikipedia : Wikitube **Strict pair:** [Wikipedia](https://en.wikipedia.org/wiki/Local_Interstellar_Cloud) : [Wikitube](https://en.wikitube.io/wiki/Local_Interstellar_Cloud) · pinned revision [1336856340](https://en.wikipedia.org/w/index.php?oldid=1336856340) · 2026-09-18 ## Previous hub tags Hubs: `Life_Physics`. Portals: [[PORTAL_Solar_System]]. --- *Solar System portal child articles, wave 1 · 2026-09-18 · drafted · row SOL-028 · explorer state `?view=neighborhood`.*