The Local Interstellar Cloud ( LIC ), also known as the Local Fluff , is an interstellar cloud roughly 30 light-years (9.2 pc ) across, through which the Solar System is moving. This feature overlaps with a region around the Sun referred to as the solar neighborhood . It is unknown whether the Sun is embedded in the Local Interstellar Cloud, or is in the region where the Local Interstellar Cloud is interacting with the neighboring G-Cloud . Like the G-Cloud and others, the LIC is part of the Very Local Interstellar Medium which begins where the heliosphere and interplanetary medium end, the furthest that probes have traveled.
33-699: The Solar System is located within a structure called the Local Bubble , a low-density region of the galactic interstellar medium . Within this region is the Local Interstellar Cloud (LIC), an area of slightly higher hydrogen density. It is estimated that the Solar System entered the LIC within the past 10,000 years. It is uncertain whether the Sun is still inside of the LIC or has already entered
66-407: A star system tend to be small fractions of a light-year, and are usually expressed in astronomical units . However, smaller units of length can similarly be formed usefully by multiplying units of time by the speed of light. For example, the light-second , useful in astronomy, telecommunications and relativistic physics, is exactly 299 792 458 metres or 1 / 31 557 600 of
99-486: A unit of time . The light-year is most often used when expressing distances to stars and other distances on a galactic scale, especially in non-specialist contexts and popular science publications. The unit most commonly used in professional astronomy is the parsec (symbol: pc, about 3.26 light-years). As defined by the International Astronomical Union (IAU), the light-year
132-412: A light-year. Units such as the light-minute, light-hour and light-day are sometimes used in popular science publications. The light-month, roughly one-twelfth of a light-year, is also used occasionally for approximate measures. The Hayden Planetarium specifies the light month more precisely as 30 days of light travel time. Light travels approximately one foot in a nanosecond ; the term "light-foot"
165-559: A small space observatory called Cosmic Hot Interstellar Plasma Spectrometer (CHIPS or CHIPSat) examined the hot gas within the Local Bubble. The Local Bubble was also the region of interest for the Extreme Ultraviolet Explorer mission (1992–2001), which examined hot EUV sources within the bubble. Sources beyond the edge of the bubble were identified but attenuated by the denser interstellar medium. In 2019,
198-420: A transition zone between the LIC and the G cloud. A recent analysis estimates the Sun will completely exit the LIC in no more than 1,900 years. The cloud has a temperature of about 7,000 K (7,000 °C; 12,000 °F), about the same temperature as the surface of the Sun. However, its specific heat capacity is very low because it is not very dense, with 0.3 atoms per cubic centimetre (5/cu in). This
231-418: Is Iron-60 from deep sea sediments , Antarctic snow, and lunar soil . Other isotopes are Manganese-53 and Plutonium-244 from deep sea materials. Supernova-originated Aluminium-26 , which was expected from cosmic ray studies, was not confirmed. Iron-60 and Manganese-53 have a peak 1.7–3.2 Million years ago and Iron-60 has a second peak 6.5–8.7 Million years ago. The older peak likely originated when
264-560: Is "ly", International standards like ISO 80000:2006 (now superseded) have used "l.y." and localized abbreviations are frequent, such as "al" in French, Spanish, and Italian (from année-lumière , año luz and anno luce , respectively), "Lj" in German (from Lichtjahr ), etc. Before 1984, the tropical year (not the Julian year) and a measured (not defined) speed of light were included in
297-402: Is a unit of length used to express astronomical distances and is equal to exactly 9 460 730 472 580 .8 km , which is approximately 5.88 trillion mi. As defined by the International Astronomical Union (IAU), a light-year is the distance that light travels in vacuum in one Julian year (365.25 days). Despite its inclusion of the word "year", the term should not be misinterpreted as
330-804: Is a relative cavity in the interstellar medium (ISM) of the Orion Arm in the Milky Way . It contains the closest of celestial neighbours and among others, the Local Interstellar Cloud (which contains the Solar System ), the neighbouring G-Cloud , the Ursa Major moving group ( the closest stellar moving group ) and the Hyades (the nearest open cluster ). It is estimated to be at least 1000 light years in size, and
363-533: Is an odd name. In 1868 an English journal labelled the light-year as a unit used by the Germans. Eddington called the light-year an inconvenient and irrelevant unit, which had sometimes crept from popular use into technical investigations. Although modern astronomers often prefer to use the parsec , light-years are also popularly used to gauge the expanses of interstellar and intergalactic space. Distances expressed in light-years include those between stars in
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#1732765707355396-516: Is defined by its neutral- hydrogen density of about 0.05 atoms /cm , or approximately one tenth of the average for the ISM in the Milky Way (0.5 atoms/cm ), and one sixth that of the Local Interstellar Cloud (0.3 atoms/cm ). The exceptionally sparse gas of the Local Bubble is the result of supernovae that exploded within the past ten to twenty million years. Geminga , a pulsar in
429-544: Is flowing outwards from the Scorpius–Centaurus association , a stellar association that is a star-forming region, roughly perpendicular to the Sun's own direction, if assumed to be two dimensional. In 2019, researchers found interstellar iron-60 (Fe) in Antarctica , which they relate to the Local Interstellar Cloud. In 2009, Voyager 2 data suggested that the magnetic strength of the local interstellar medium
462-463: Is less dense than the average for the interstellar medium in the Milky Way (0.5/cm or 8/cu in), though six times denser than the gas in the hot, low-density Local Bubble (0.05/cm or 0.8/cu in) which surrounds the local cloud. In comparison, Earth's atmosphere at the edge of space (i.e. 100 km above sea level) has around 1.2 × 10 molecules per cubic centimeter, dropping to around 50 million (5.0 × 10) at 450 km (280 mi). The cloud
495-570: Is the product of the Julian year (365.25 days, as opposed to the 365.2425-day Gregorian year or the 365.24219-day Tropical year that both approximate) and the speed of light ( 299 792 458 m/s ). Both of these values are included in the IAU (1976) System of Astronomical Constants , used since 1984. From this, the following conversions can be derived: The abbreviation used by the IAU for light-year
528-549: Is the product of the J1900.0 mean tropical year and the defined speed of light. Abbreviations used for light-years and multiples of light-years are: The light-year unit appeared a few years after the first successful measurement of the distance to a star other than the Sun, by Friedrich Bessel in 1838. The star was 61 Cygni , and he used a 160-millimetre (6.2 in) heliometre designed by Joseph von Fraunhofer . The largest unit for expressing distances across space at that time
561-513: The Local Interstellar Cloud (LIC), a minor region of denser material within the Bubble. The LIC formed where the Local Bubble and the Loop I Bubble met. The gas within the LIC has a density of approximately 0.3 atoms per cubic centimeter. The Local Bubble is not spherical, but seems to be narrower in the galactic plane , becoming somewhat egg-shaped or elliptical, and may widen above and below
594-824: The Sun's magnetic field . This interaction with the heliosphere is under study by the Interstellar Boundary Explorer (IBEX), a NASA satellite mapping the boundary between the Solar System and interstellar space. Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → Local Hole → Observable universe → Universe Each arrow ( → ) may be read as "within" or "part of". Local Bubble The Local Bubble , or Local Cavity ,
627-476: The constellation Gemini , was once thought to be the remnant of a single supernova that created the Local Bubble, but now multiple supernovae in subgroup B1 of the Pleiades moving group are thought to have been responsible, becoming a remnant supershell . Other research suggests that the subgroups Lower Centaurus–Crux (LCC) and Upper Centaurus–Lupus (UCL), of the Scorpius–Centaurus association created both
660-496: The IAU (1964) System of Astronomical Constants, used from 1968 to 1983. The product of Simon Newcomb 's J1900.0 mean tropical year of 31 556 925 .9747 ephemeris seconds and a speed of light of 299 792 .5 km/s produced a light-year of 9.460 530 × 10 m (rounded to the seven significant digits in the speed of light) found in several modern sources was probably derived from an old source such as C. W. Allen 's 1973 Astrophysical Quantities reference work, which
693-789: The diagram above right. Several tunnels connect the cavities of the Local Bubble with the Loop ;I Bubble, called the "Lupus Tunnel". Other bubbles which are adjacent to the Local Bubble are the Loop II Bubble and the Loop III Bubble . In 2019, researchers found interstellar iron in Antarctica which they relate to the Local Interstellar Cloud , which might be related to the formation of the Local Bubble. Launched in February ;2003 and active until April 2008,
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#1732765707355726-798: The expanding surface of the bubble had collected gas and debris and was responsible for the formation of all young, nearby stars. These new stars are typically in molecular clouds like the Taurus molecular cloud and the open star cluster Pleiades . On earth several radioactive isotopes were connected to supernovae occurring relative nearby to the solar system. The most common source is found in deep sea ferromanganese crusts . Such nodules are constantly growing and deposits iron, manganese and other elements. Samples are divided into layers which are dated for example with Beryllium-10 . Some of these layers have higher concentrations of radioactive isotopes. The isotope most commonly associated with supernovae on earth
759-411: The first 3D map of the Local Bubble has been reported using the observations of diffuse interstellar bands. In 2020, the shape of the dusty envelope surrounding the Local Bubble was retrieved and modeled from 3D maps of the dust density obtained from stellar extinction data. In January 2022, a paper in the journal Nature found that observations and modelling had determined that the action of
792-452: The galactic plane, becoming shaped like an hourglass. It abuts other bubbles of less dense interstellar medium (ISM), including, in particular, the Loop I Bubble. The Loop I Bubble was cleared, heated and maintained by supernovae and stellar winds in the Scorpius–Centaurus association , some 500 light years from the Sun . The Loop I Bubble contains the star Antares (also known as α Sco, or Alpha Scorpii), as shown on
825-464: The local bubble and the Loop I Bubble. With LCC being responsible for the Local Bubble and UCL being responsible for the Loop I Bubble. It was found that 14 to 20 supernovae originated from LCC and UCL, which could have formed these bubbles. The Solar System has been traveling through the region currently occupied by the Local Bubble for the last five to ten million years. Its current location lies in
858-438: The mental picture of the approximate transit time for light, but he refrained from using the light-year as a unit. He may have resisted expressing distances in light-years because it would reduce the accuracy of his parallax data due to multiplying with the uncertain parameter of the speed of light. The speed of light was not yet precisely known in 1838; the estimate of its value changed in 1849 ( Fizeau ) and 1862 ( Foucault ). It
891-689: The older peak is that it was produced by one supernova in the Tucana-Horologium association 7-9 Million years ago. Solar System → Local Interstellar Cloud → Local Bubble → Gould Belt → Orion Arm → Milky Way → Milky Way subgroup → Local Group → Local Sheet → Virgo Supercluster → Laniakea Supercluster → Local Hole → Observable universe → Universe Each arrow ( → ) may be read as "within" or "part of". Light years A light-year , alternatively spelled light year ( ly or lyr ),
924-493: The same general area, such as those belonging to the same spiral arm or globular cluster . Galaxies themselves span from a few thousand to a few hundred thousand light-years in diameter, and are separated from neighbouring galaxies and galaxy clusters by millions of light-years. Distances to objects such as quasars and the Sloan Great Wall run up into the billions of light-years. Distances between objects within
957-489: The solar system moved through the Orion-Eridanus superbubble and the younger peak was generated when the solar system entered the local bubble 4.5 Million years ago. One of the supernovae creating the younger peak might have created the pulsar PSR B1706-16 and turned Zeta Ophiuchi into a runaway star . Both originated from UCL and were released by a supernova 1.78 ± 0.21 Million years ago. Another explanation for
990-404: Was much stronger than expected (370 to 550 pico teslas (pT), against previous estimates of 180 to 250 pT). The fact that the Local Interstellar Cloud is strongly magnetized could explain its continued existence despite the pressures exerted upon it by the winds that blew out the Local Bubble. The Local Interstellar Cloud's potential effects on Earth are greatly diminished by the solar wind and
1023-432: Was not yet considered to be a fundamental constant of nature, and the propagation of light through the aether or space was still enigmatic. The light-year unit appeared in 1851 in a German popular astronomical article by Otto Ule . Ule explained the oddity of a distance unit name ending in "year" by comparing it to a walking hour ( Wegstunde ). A contemporary German popular astronomical book also noticed that light-year
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1056-492: Was the astronomical unit , equal to the radius of the Earth's orbit at 150 million kilometres (93 million miles). In those terms, trigonometric calculations based on 61 Cygni's parallax of 0.314 arcseconds, showed the distance to the star to be 660 000 astronomical units (9.9 × 10 km; 6.1 × 10 mi). Bessel added that light takes 10.3 years to traverse this distance. He recognized that his readers would enjoy
1089-438: Was updated in 2000, including the IAU (1976) value cited above (truncated to 10 significant digits). Other high-precision values are not derived from a coherent IAU system. A value of 9.460 536 207 × 10 m found in some modern sources is the product of a mean Gregorian year (365.2425 days or 31 556 952 s ) and the defined speed of light ( 299 792 458 m/s ). Another value, 9.460 528 405 × 10 m ,
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