local interstellar cloud
redfield s. , linsky j. the structure of the local interstellar medium. iv. dynamics, morphology, physical properties, and implications of cloud–cloud interactions .
redfield, s. , and linsky, j. l. : 2001 ,
microstructure of the local interstellar cloud and the identification of the hyades cloud
, astrophysical journal, 551, 413
centauri a and b evidently lie beyond the local interstellar cloud, although the line of sight from earth is dominated by another interstellar cloud known as the g cloud. an interstellar mission to this system would tell us whether the sun is actually embedded in the local interstellar cloud or just outside it in the region where the lic is interacting with the g cloud. conceivably a centauri mission would thus get to sample two different interstellar clouds, along with the low density material between them. as crawford writes, we would receive a windfall of data :
the local interstellar cloud is an almost empty bubble of gas and dust that our solar system is travelling through with a distinct direction and speed .
previous measurements of interstellar helium atoms by the ulysses spacecraft indicated the solar system may be emerging from the local cloud. but the latest ibex data, which detected incoming atoms moving at a slower speed, show the heliosphere is still embedded within the local cloud .
determine the chemical abundances and depletions of warm clouds in the local interstellar medium .
above: an artist' s concept of the local interstellar cloud, also known as the
local fluff .
credit: linda huff (american scientist) and priscilla frisch (university of chicago) [ more ]
redfield, seth and linsky, jeffrey l. : 2008 ,
the structure of the local interstellar medium. iv. dynamics, morphology, physical properties, and implications of cloud - cloud interactions
, astrophysical journal, 673, 283
redfield, s. , and linsky, j. l. ,: 2000 ,
the three dimensional structure of the warm local interstellar medium. ii. the colorado model of the local interstellar cloud (lic), astrophysical journal, 534, 825
, also called the local fluff, during the next 10, 000 years. much remains unknown about the local
the lism is that region of space in the local galactic arm where the sun is located (thomas, 1978), the local interstellar cloud is the cloud within it in which the sun resides, and the heliosphere is the region in space filled with solar wind material (both supersonic and subsonic flow) .
, the local cloud has an extent of about 5 pc (15 light - years) in the direction of g191 - b2b. if this dimension is typical, the total mass of the cloud is about 0. 4
determine the physical properties (temperature, density, and ionization state) of warm clouds in the local interstellar medium .
the observed temperature and density of the local cloud do not provide enough pressure to resist the' crushing action' of the hot gas around it ,
says opher .
the sun is located near the edge of a great void in interstellar matter known as the
local bubble
that is filled with hot low - density plasma. several thousand years ago the sun entered our local interstellar cloud (lic), one of several nearby clouds composed of warm, low density (~ 0. 3 atoms / cm
map of the local galactic neighborhood showing the sun located near the edge of our local interstellar cloud (lic). the star alpha - centauri is located just over 4 light - years away in the neighboring g - cloud complex. outside these clouds, the density may be lower than 0. 001 atoms / cc. our sun and the lic have a relative velocity of 26 km / sec .
during the past few million years, wispy filaments of interstellar gas have drifted into the local bubble. our solar system is immersed in one of those filaments - - the
local fluff ,
a relatively cool (7000 k) cloud containing 0. 1 atoms per cubic centimeter. by galactic standards, the local fluff is not very substantial. it has little effect on earth because the solar wind and the sun' s magnetic field are able to hold the wispy cloud at bay .
2 science summary: the interaction of the solar wind and the local interstellar medium .
national research council. 2004 .
the voyagers are not actually inside the local fluff ,
says opher .
but they are getting close and can sense what the cloud is like as they approach it .
right: an artist' s concept of the local fluff. [ more ]
astronomers originally thought that this suffocating cloud would smother its smaller relative, but measurements from the voyager probes as they exit the solar system have shown that the fluff has its own magnetic field that repels the larger cloud .
the survival of the local cloud in the environment of the hot local bubble is problematical. if it predated the occurrence of a nearby supernova whose blast wave might have created the local bubble, it should not have survived the blast. even in the current environment, such a cloud must have a short lifetime because of evaporation by the hot bubble gas, and it is therefore tempting to conclude that the cloud is fairly young. perhaps it is the remnant of a planetary nebula shed by a nearby star that has recently become a white dwarf (cox & reynolds 1987) .
1. evaluating the morphology of the local interstellar medium: using new data to distinguish between multiple discrete clouds and a continuous medium redfield, s. , & linsky, j. l. 2015, apj, 812, 125 we use a new sample of hst observations to test between a lism morphology of a single lism cloud that is kinematically deformed or a multiple cloud model. we find the multiple cloud model is preferred, even though it utilizes more parameters .
we’d better, in other words, get up to speed about the interstellar medium before we launch any true interstellar craft, and that means a series of early missions of a precursor nature that can tell us what to expect. crawford notes that the sun is currently located close to the boundary of a small low - density interstellar cloud known as the local interstellar cloud (lic), one of several such clouds within several parsecs of our solar system — indeed, one study identifies seven such clouds within 5 parsecs of sol. these are found within the local bubble, about which this :
v. v. izmodenov, j. geiss, r. lallement, g. gloeckler, v. b. baranov, y. g. malama, filtration of interstellar hydrogen in the two - shock heliospheric interface: inferences on the local interstellar cloud electron density. j. geophys. res .
g. p. zank, interaction of the solar wind with the local interstellar medium: a theoretical perspective. space sci. rev .
6. the three - dimensional structure of the warm local interstellar medium. ii. the colorado model of the local interstellar cloud redfield, s. , & linsky, j. l. 2000, apj, 534, 825 my first paper on the lism that i led, and the beginning of a long series of papers with my ph. d. advisor, jeff linsky. we developed a model of the morphology of the local interstellar cloud, the cloud that directly surrounds the solar system, and the material in which the voyager spacecraft are speeding into. an online lic model column density calculator is available to predict the amount of material associated with the lic along any given sight line. this work was featured in physics today and sky & telescope .
weingartner, j. c. & draine, b. t. dust grain - size distributions and extinction in the milky way, large magellanic cloud, and small magellanic cloud. astrophys. j. 548, 296 (2001) .
nasa astronomer' s best guess is depicted in the map (below) of the surrounding 1500 light years constructed from multiple observations and deductions. the local interstellar cloud (lic), shown in violet, which is flowing away from the scorpius - centaurus association of young stars) .
i' ve been trying to wrap my head around capabilities of current radio - astronomical spectrometry technology to isolate not too distant tenuous sources, say, chemical composition and density of the the interstellar medium right in the neighborhood of our solar system. in essence, what is our local interstellar cloud made out of and how much of it is there :
cen line of sight: d / h ratio, physical properties of local interstellar gas, and measurement of heated hydrogen near the heliopause. astrophys. j .
h. l. pauls, g. p. zank, interaction of a nonuniform solar wind with the local interstellar medium. j. geophys. res .
opher m. , stone e. c. , liewer p. c. the effects of a local interstellar c field on voyager 1 and 2 observations .
we can learn a lot about these matters, including the properties of the local interstellar cloud, by spectroscopic studies of interstellar absorption lines toward nearby stars. investigations into our solar system’s interactions with the heliosphere are also useful, but we’ll need to augment these with direct measurements of the interstellar materials just beyond the heliopause, and that means developing the capability to get space probes to distances up to 1000 au or more .
4. the structure of the local interstellar medium iv: dynamics, morphology, physical properties, and implications of cloud - cloud interactions redfield, s. , & linsky, j. l. 2008, apj, 673, 283 a new kinematic model of the suite of 15 clouds within about 15 pc of the sun. an online lism kinematic calculator is available to predict the velocity of absorption along any given sight line .
study the interaction of stellar winds with the local ism that forms hydrogen walls and astrospheres around stars .
astronomers call the cloud we' re running into now the local interstellar cloud or
local fluff
for short. it' s about 30 light years wide and contains a wispy mixture of hydrogen and helium atoms at a temperature of 6000 c. the existential mystery of the fluff has to do with its surroundings. about 10 million years ago, a cluster of supernovas exploded nearby, creating a giant bubble of million - degree gas. the fluff is completely surrounded by this high - pressure supernova exhaust and should be crushed or dispersed by it .
wood, b. e. , redfield, s. , linsky, j. l. , and sahu, m. s. : 2002 ,
elemental abundances and ionization states within the local interstellar cloud derived from hst and fuse observations of the capella line of sight
, astrophysical journal, 581, 1168
3. the interstellar medium surrounding the sun frisch, p. c. , redfield, s. , & slavin, j. d. 2011, araa, 49, 237 a review of our current understanding of the local interstellar medium .
v. florinski, g. p. zank, w. i. axford, the solar system in a dense interstellar cloud: implications for cosmic ray fluxes at earth and 10be records. geophys. res. lett .
h. l. pauls, g. p. zank, l. l. williams, interaction of the solar wind with the local interstellar medium. j. geophys. res .
our sun is moving through the local interstellar gas cloud approximately into the direction of scorpio with a speed of about 25 km / sec. as a result of this motion, an interstellar wind with that speed is blowing through our planetary system. this is similar to the wind felt while driving a convertible car with the top down. we measure this interstellar wind as helium, and the density of helium changes with our year, an effect that can be seen in this brief animation .
redfield, s. , and linsky, j. l. : 2004 ,
the structure of the local interstellar medium. iii. temperature and turbulence
, astrophysical journal, 613, 1004
the matter between stars, the interstellar medium, varies considerably from region to region in our galaxy. the sun is inside a very large structure called the local bubble, a region of hot tenuous gas formed by supernova explosions tens of millions of years ago [ 1–3 ]. adjacent to the local bubble is a similar but larger bubble, also formed from supernova explosions. inside the local bubble are smaller, denser clouds which may have broken off from the bubble interaction region. the sun is now in one of these denser, cooler clouds. the h density of the local cloud is about 0. 2 cm −3, the temperature is about 6000 k, and the cloud moves about 23 km / s with respect to the sun [ 4, 5 ]. the magnetic field strength cannot be directly measured, but based on models is 3–5 nt [ 6, 7 ] .
close to the sun (within ~ 5 au), the local distribution of interstellar neutral helium has been measured using an impact - ionization method by the ulysses interstellar neutral gas experiment (gas) (witte et al. , 1992). these measurements provide the velocity and direction of the flow of interstellar he as well as its temperature and density .
december 23, 2009: the solar system is passing through an interstellar cloud that physics says should not exist. in the dec. 24th issue of nature, a team of scientists reveal how nasa' s voyager spacecraft have solved the mystery .
linsky, jeffrey l. , rickett, barney j. , and redfield, seth: 2008 ,
the origin of radio scintillation in the local interstellar medium
, astrophysical journal, 675, 413
h. l. pauls, g. p. zank, interaction of a nonuniform solar wind with the local interstellar medium. 2. a two - fluid model. j. geophys. res .
we entered the 30 - light - year - wide cloud of hydrogen and helium, which astronomers refer to as ‘local fluff’, at some point after anatomically modern humans evolved about 200, 000 years ago, and we’ll be leaving it in about 10, 000 to 20, 00 years .
toward all stars observed, and this minimum is all that is seen for stars in the local bubble. thus, it appears that the sun must be surrounded by a small, at least partially neutral cloud with approximately this column density. an atomic - hydrogen density of about 0. 1 cm
whereas solar wind and interstellar plasmas respond to electromagnetic fields (being decelerated at the heliospheric boundary shocks, for example), interstellar neutrals flow relatively unimpeded. plasma
below: a computer - simulated chips spectrum of extreme - uv radiation from hot gas in the local bubble. [ more ]
our solar system has been voyaging through the very low density local interstellar cloud, a region about 30 light - years across that' s as sparse as a handful of air stretched over a column that is hundreds of light years long, or about one atom per three cubic centimeters of space. earth and our sun has been traveling through the cloud for somewhere between 40, 000 and 150, 000 years and will probably not emerge for another 20, 000 years. a mere blip in our 250 million - year orbit through the milky way .
if the sun does lie within the lic, then a mission to α cen would sample the outer layers of the lic, an interval of low density lb material, the edge of the g cloud, and the deep interior of the g cloud. this would sample one of the most diverse ranges of interstellar conditions of any mission to another star located with 5 pc of the sun, as most other potential targets lie within the lic… even if the sun lies just outside the lic (as argued by redfield and linsky [ 8 ]), the trajectory to α cen would still permit detailed observations of the boundary of the g cloud (and its possible interaction with the lic), and determine how its properties change with increasing depth into the cloud from the boundary .
isn' t alpha centauri in there as well? given it' s very short distance from sol, i' d expect both systems to belong to the same cloud .
redfield, s. , wood, b. e. , and linsky, j. l. : 2004 ,
physical structure of the local interstellar medium
, advances in space research, 34, 41
the first thing to notice is that the local interstellar cloud, in which the sun is evolving right now, is a fairly diffuse region, with a typical density of about one to a few particles per cubic centimeters. clouds with such low density are actually mostly atomic; as you can see on this plot (snow & mccall 2006, adapted from neufeld et al. 2005) :
linsky, j. l. and redfield, s. : 2015 ,
what is the morphology of the local interstellar medium and its importance for the gaia era ?
, memorie della societa astronomica italiana, 86, 606
p. c. frisch, characteristics of nearby interstellar matter. space sci. rev .
i don’t want to worry you, but the solar system is currently sat in the middle of a vast cloud of incredibly hot gas, about the same temperature as the surface of the sun .
redfield, s. and linsky, j. l. : 2015 ,
evaluating the morphology of the local interstellar medium: using new data to distinguish between multiple discrete clouds and a contimuous medium
, astrophysical journal, 822, 125
g. p. zank, h. l. pauls, l. l. williams, d. t. hall, interaction of the solar wind with the local interstellar medium: a multifluid approach. j. geophys. res .
beyond that, and having taken these findings in account in its design, a true interstellar probe would be a priceless tool for measuring everything from dust density and composition to the interstellar magnetic field strength enroute. crawford points out that a spacecraft moving at 0. 1c could do daily measurements 17 au apart (roughly half the radius of the solar system) which would offer unprecedented knowledge of the structure of the local interstellar medium .
good news is, there is not only molecular lines to give informations about the physical properties (temperature, density, ionization, velocity structure and morphology) of the local interstellar cloud. in particular, ultraviolet is a perfectly suited wavelength range to sudy this region in absorption, and there are some quite extensive studies of the subject (see for example paper i, paper ii, paper iii and paper iv of redfield et al .) .
the lic resides in a low - density hole in the interstellar medium (ism) called the local bubble, shown in black. nearby, high - density molecular clouds including the aquila rift surround star forming regions, each shown in orange .
the
local bubble
exists in a network of cavities in the interstellar medium, probably carved by massive star explosions millions of years ago. the interstellar medium (or ism) is the matter that exists in the space between the star systems in a galaxy. this matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. it fills interstellar space and blends smoothly into the surrounding intergalactic space .
i recall reading about smoke particle shield, although i do not recall the source. once cruising speed is reached, a probe moves out significantly ahead of the main spacecraft and generates a very large cloud of smoke particles that leads the spacecraft for the entire journey. the idea is that the smoke cloud will intercept and atomize the majority of the dust particles before the main spacecraft reaches that area of space .
the newly - created ion, with its positive electric charge, can no longer cross magnetic field lines. ions are forced to gyrate around a field line, like a gymnast swings around the horizontal bar in the giant swing. (to see an animated explanation of this, please watch part two of our movie regading the topic .) these interstellar ions are called
pickup ions
. they are an excellent tool for determining the density of the local insterstellar cloud, and to help us find out of which elements the interstellar medium consists .
for more information regarding this website and the interstellar probe project, please contact dr. paulett liewer
model the structure and kinematics of warm clouds in the interstellar medium out to about 100 pc .
observations from the interstellar boundary explorer are not consistent with a bow shock ahead of the heliosphere .
frisch p. c. the s1 shell and interstellar magnetic field and gas near the heliosphere .
we know because we can still see the cloud today. it' s 450 light years from earth and receding in the direction of the constellations scorpius and centaurus (hence the cloud' s name ,
sco - cen
). astronomer jesús maíz - apellániz of johns hopkins university recently backtracked sco - cen' s motion and measured its closest approach: 130 light years away about 5 million years ago .
d. p. cox, l. helenius, flux - tube dynamics and a model for the origin of the local fluff. astrophys. j .
perhaps the most important lesson learned from the voyager and ulysses missions, complemented by theory and modeling efforts, is that the physics of the outer heliosphere is influenced profoundly by the lism since we are embedded in the local interstellar cloud (lic). this is because neutral hydrogen atoms flow into the heliosphere and are the dominant component, by mass, from 10 au outward (i. e. , beyond saturn). as described below, the ionization of interstellar neutrals in the supersonic solar wind can even affect the size and structure of the global heliosphere .
supernovas near earth are rare today, but during the pliocene era of australopithecus supernovas happened more often. their source was an interstellar cloud called
sco - cen
that was slowly gliding by the solar system. within it, dense knots coalesced to form short - lived massive stars, which exploded like popcorn .
figure 2. 8 projection of a three - dimensional magnetohydrodynamic - only simulation (i. e. , excluding interstellar h atoms) in the presence of an interplanetary and an interstellar magnetic field. the interstellar magnetic field is oriented 20° from the interstellar flow direction and the interstellar magnetic field strength is assumed to be 1. 6 μg. density isolines are plotted in the meridional plane, together with three - dimensional steamlines starting in this plane. source: pogorelov et al. (2004) .
this may be applicable: urltoken table1. dat contains a list of hipparchos stars in the ism (local bubble) used to calibrate distances to nai observations .
frisch has noted that homo sapiens arose only after the local interstellar medium was cleared out. fewer clouds to run into would promote a stabler climate for our planet, she argues. so perhaps what australopithecus saw was a good omen, after all... .
linsky, j. l. , redfield, s. , wood, b. e. , and piskunov, n. : 2000 ,
the three dimensional structure of the warm local interstellar medium. i. methodology
, astrophysical journal, 528, 756
t. linde, t. i. gombosi, p. l. roe, k. g. powell, d. l. dezeeuw, the heliosphere in the magnetized local interstellar medium: results of a 3d mhd simulation. j. geophys. res .
using data from voyager, we have discovered a strong magnetic field just outside the solar system ,
explains lead author merav opher, a nasa heliophysics guest investigator from george mason university .
this magnetic field holds the interstellar cloud together and solves the long - standing puzzle of how it can exist at all .
the effectiveness of the lyman - alpha absorption technique for investigating the outer heliosheath resides in its ability to probe local density and temperature enhancements. the lyman - alpha absorption
the sensitivity of hut in the 400 - 900 å portion of the extreme - uv band allows us to make a direct measurement of the neutral - hydrogen and neutral helium column densities in the local ism. the nearby hot white dwarf g191 - b2b, located within the bubble but beyond the local cloud, provides a suitable background source for this measurement. it is a da white dwarf, meaning that it has a pure hydrogen atmosphere whose properties are readily calculated, and is hot enough (60, 000 k) to provide a strong signal at 500 å. furthermore, the absence of atmospheric helium in such a star avoids potential confusion with interstellar helium .
these [ clouds ] are immersed in the very empty (n h ~ 0. 005 cm - 3) and probably hot (t ~ 10 6 k) local bubble (lb) in the interstellar medium, which extends for about 60 - 100 parsecs from the sun in the galactic plane before denser interstellar clouds are encountered (at high galactic latitudes the lb appears to be open, forming a chimney - like structure in the interstellar medium which extends into the galactic halo… )
there are, however, denser clouds out there. the sco - cen complex, for instance, is sending a stream of interstellar
cloudlets
in our direction .
some of those cloudlets might be hundreds of times denser than the local fluff ,
says priscilla frisch, an astrophysicist at the university of chicago who studies the local interstellar medium .
if we ran into one, it would compress the sun' s magnetic field and allow more cosmic rays to penetrate the inner solar system, with unknown effects on climate and life .
linsky, j. l. , redfield, s. , and schwarz, m. : 2017 ,
visualizing the three - dimensional structure of the local interstellar medium and possible physical causes of this structure
, open access journal of physics: conference series, to appear
primitive solar system materials, such as certain types of meteorites, interplanetary dust particles and cometary matter, contain small quantities of refractory dust grains that are older than our solar system. these ‘presolar grains’ condensed in the winds of evolved stars and in the ejecta of stellar explosions, and they were part of the interstellar gas and dust cloud from which our solar system formed 4. 57 billion years ago 1. interstellar dust is not only stardust but forms in the interstellar medium as well, predominantly as silicates, and, to a lesser extent, as carbonaceous dust and iron particles 2. presolar grains represent a sample of stardust, and their abundances in primitive solar system materials can be used to constrain the fraction of stardust among interstellar dust. here we show that the size distribution of presolar silicates follows that observationally derived for interstellar dust, at least in the diameter range 100–500 nm, that current estimates of presolar grain abundances (mass fractions) are at least a factor of 2 too low, and that several per cent of the interstellar dust in the interstellar cloud pre - dating our solar system was stardust, making it a minor but still important ingredient of the starting material from which our solar system formed .
linsky, j. l. : 2002 ,
constructing physically realistic models of the interstellar gas: start with understanding the physics of the local ism
, in hubble science legacy workshop, ed. k. sembach, et al, asp conf. series, 291, 188
polarized radiation in the nebula cloud leads to the formation of proteins, nucleobases and then dna. the combination of hydrogen, carbon, oxygen, nitrogen, cyanide and several other elements, could create adenine, which is a dna base, whereas oxygen and phosphorus could ladder dna base pairs. glycine has also been identified in the interstellar clouds .
we present an empirical dynamical model of the local interstellar medium based on 270 radial - velocity measurements for 157 sight lines toward nearby stars. physical - parameter measurements (i. e. , temperature, turbulent velocity, depletions) are available for 90 components, or one - third of the sample, enabling initial characterizations of the physical properties of lism clouds. the model includes 15 warm clouds located within 15 pc of the sun, each with a different velocity vector. we derive projected morphologies of all clouds and estimate the volume filling factor of warm partially ionized material in the lism to be between ~ 5. 5% and 19% . relative velocities of potentially interacting clouds are often supersonic, consistent with heating, turbulent, and metal - depletion properties. cloud - cloud collisions may be responsible for the filamentary morphologies found in ~ 1 / 3 of lism clouds, the distribution of clouds along the boundaries of the two nearest clouds (lic and g), the detailed shape and heating of the mic cloud, the location of nearby radio scintillation screens, and the location of a lism cold cloud. contrary to previous claims, the sun appears to be located in the transition zone between the lic and g clouds .
redfield, s. , and linsky, j. l. : 2002 ,
the structure of the local interstellar medium. i. high - resolution observations of fe ii, mg ii, and caii toward stars within 100 parsecs
, astrophysical journal supplement series, 139, 439
jenkins, e. b. , et al (including linsky, j. l .), 2000 ,
the ionization of the local interstellar medium as revealed by fuse observations of n, o, and ar toward white dwarf stars
, astrophysical journal letters, 538, l81
linsky, j. l. and redfield, s. : 2009 ,
structure, dynamics, and physical properties of the warm lism within the local bubble
, in the local bubble and beyond ii, ed. k. d. kuntz, r. k. smith, and s. l. snowden, aip conference proceedings 1156, 174
alouani - bibi1 f. , opher m. , alexashov d. , izmodenov v. , toth g. kinetic versus multi - fluid approach for interstellar neutrals in the heliosphere: exploration of the interstellar magnetic field effects .
i posted this question in the space exploration forum, but i think it might be more appropriate here in the astronomy forum. this is the thread: urltoken basically, i' d like to know which local stars are, and aren' t, embedded in the
local fluff
along with the sun. i can' t find any lists .
linsky, j. l. : 2009 ,
results of the issi workshop' from the outer heliosphere to the local bubble: comparison of new observations with theory
, in the local bubble and beyond ii, ed. k. d. kuntz, r. k. smith, and s. l. snowden, aip conference proceedings 1156, 184
linsky, j. l. and redfield, s. : 2007 ,
structure of the local ism
, in sins - small ionized and neutral structures in the diffuse interstellar medium, ed. m. haverkorn and w. m. goss, asp conf. series, 365, 219
what was something of a mystery until recently, however, is why the cloud exists at all. about ten million years ago, a cluster of supernovae exploded close to earth, creating a bubble of much - hotter gas that enveloped the fluff .
redfield, s. , and linsky, j. l. : 2004 ,
the structure of the local interstellar medium. ii. observations of d i, c ii, n i, o i, al ii, and si ii toward stars within 100 parsecs
, astrophysical journal, 602, 776
r. ratkiewicz, a. barnes, g. a. molvik, j. r. spreiter, s. s. stahara, m. vinokur, s. venkateswaran, effect of varying strength and orientation of local interstellar magnetic field on configuration of exterior heliosphere: 3d mhd simulations. astron. astrophys .
the only two stars that are definitely shown as being embedded in the local fluff are sol and altair; bit it looks a lot more extensive than that. stars that might be in the fluff, judging by the map praedst posted, include barnard' s star, 61 cygni, wolf 1055, and maybe 70 ophiuchi. but since we don' t know the thickness of this cloud from the published image, we can' t be sure .
n. v. pogorelov, g. p. zank, t. ogino, three - dimensional features of the outer heliosphere due to coupling between the interstellar and interplanetary magnetic fields i. magnetohydrodynamic model: interstellar perspective. astrophys. j .
this report is the summary of a workshop held in may 2003 by the space studies board' s committee on solar and space physics to synthesize understanding of the physics of the outer heliosphere and the critical role played by the local interstellar medium (lism) and to identify directions for the further exploration of this challenging environment .
however, suppose we assume for the moment that there is an impending threat from such a cloudlet incursion. would the solar and climatic effects be like that of a superwave? well we can do some calculations to find out. given that the local fluff has a density of ~ 0. 1 hydrogen atoms / cm 3. the hypothesized cloudlet, which could have a density hundreds of times greater, would then have a density of say around 20 to 50 hydrogen atoms per cubic centimeter. this would equal a cloud density of around 3 to 8 x 10 - 23 grams / cm 3. an interstellar cloud incursion of this sort would have a significant climatic effect and a significant solar effect. but the most dangerous phase would likely last for several years, rather than for centuries or millennia as is often the case for the effects from a superwave .
linsky, j. l. and redfield, s. : 2014 ,
the local ism in three dimensions: kinematics, morphology and physical properties
, astrophysics and space science, 354, 29
we often think about interstellar probes only in the context of what they find at the end of their journeys — astrobiologically interesting planets seem to be the whole story. but not so fast. as ian crawford (university of london) notes in a recent paper, there are quite a few fascinating — and indeed critical — things we need to learn about interstellar space itself, in this case what is known as the local interstellar medium (lism). crawford, who has been analyzing these matters for the project icarus team, notes how much we’ve learned about the lism since the daedalus days .
in the gas flowing through the solar system and a neutral - hydrogen density about five times as large with a temperature of about 8, 000 k. the low observed ratio of h to he compared with the nominal cosmic abundance ratio of 10 has usually been interpreted to indicate that the hydrogen is significantly ionized, whereas the helium is largely neutral. however, known sources of ionizing radiation in the solar neighborhood are insufficient to maintain such a high degree of hydrogen ionization in the local cloud .
w. i. axford, the interaction of the solar wind with the interstellar medium. solar wind, nasa spec. publ .
the size of the heliosphere is determined by a balance of forces: solar wind inflates the bubble from the inside while the local fluff compresses it from the outside. voyager' s crossings into the heliosheath revealed the approximate size of the heliosphere and, thus, how much pressure the local fluff exerts. a portion of that pressure is magnetic and corresponds to the ~ 5 microgauss opher' s team has reported in nature .
malamut, c. , redfield, s. , linsky, j. l. , wood, b. e. , and ayres, t. r. : 2014 ,
the structure of the local interstellar medium. vi. new mgii, feii, and mnii observations toward stars within 100 pc
, astrophysical journal, 787, 75
the relative proximity of α cen, together with its interesting interstellar sightline and the presence of stars of three different spectral types, makes it an attractive target for humanity’s first interstellar mission. however, as the bulk of the scientific benefits of interstellar spaceflight pertain to planetary science and astrobiology, a final prioritization must await future developments in the detection of planetary systems around the nearest stars. fortunately, expected advances in astronomical instrumentation over the next century should ensure that a comprehensive list of prioritized targets is available well before rapid interstellar travel is technically feasible .
n. v. pogorelov, t. matsuda, nonevolutionary mhd shocks in the solar wind and interstellar medium interaction. astron. astrophys .
pickup ion data directly to the lism h. secondly, there is some disagreement about the temperature of neutral hydrogen in the interplanetary medium. however, the interstellar helium temperature now appears to be well constrained and, by implication, the temperature of the interstellar h as well .
on the other hand, the website of priscilla frisch (urltoken) suggests that this apod image is based on some slightly earlier and less complete data from the same instrument (hubble ghrs). the methodology is outlined in frisch (1994), science, v265, p1423 ,
morphology and ionization of the interstellar cloud surrounding the solar system
: urltoken using the results from the 1995 paper i mentioned above would be better .
even if we didn’t have that, the damage wouldn’t be too great. the cloud is hot, but it’s also not very dense — with just 0. 3 atoms per cubic centimetre. at the edge of the atmosphere, for comparison, the earth has about 12 billion atoms per cubic centimetre .
linsky, j. l. , redfield, s. , and wood, b. : 2000 ,
components of the local interstellar medium
, invited talk at iau symposium 203, recent insights in to the physics of the sun and heliosphere, manchester england, aug 7 - 11, 2000, astronomical society of the pacific conference series, 200, 595
figure 2. 2 schematic of the heliosphere. the global heliosphere is created by the supersonic solar wind diverting the interstellar plasma flow around the sun. interstellar ions and neutral atoms flow at 26 km / s relative to the sun. the solar wind, flowing outward at 400 to 800 km / s, makes a transition to subsonic flow at the termination shock. beyond this, the solar wind is turned toward the heliotail, carrying with it the spiraling interplanetary magnetic field. the heliopause separates solar material and magnetic fields from interstellar material and magnetic fields. interstellar neutral atoms and higher - energy galactic cosmic rays can penetrate the heliosphere, but interstellar ions are diverted around it. beyond the heliopause there may also be a bow shock formed in the interstellar medium. source: jet propulsion laboratory (1999a), courtesy of steven t. suess .
linsky, j. l. , redfield, s. , and wood, b. e. : 2000 ,
the warm local ism: structure, properties, and theory
, invited talk at the fourth tetons summer conference: galactic structure, stars and the interstellar medium, jackson hole wy, may 28 - june 1, 2000, asp 231, 337
the cosmic hot interstellar plasma spectrometer - - (uc berkeley) chips mission home page. see also the chips public education and outreach website .
p. a. isenberg, interaction of the solar wind with interstellar neutral hydrogen: three - fluid model. j. geophys. res .
in february 2012, nasa' s interstellar boundary explorer (ibex), the centerpiece of a $ 169 million mission mapping the frontier of the sun' s influence, detected atoms from interstellar space streaming by earth, that are different from the chemical make - up of the solar system .
besides the erosion / explosion fears, flying through even a tenuous dust cloud at 0. 1c could create enough friction to slow down the craft like an atmospheric reentry. it would then require addition propulsion (and time) to regain 0. 1c. the craft could also be thrown off course - perhaps badly off course - requiring a significant course correction and the use of more propellant, also adding time to the mission. (this assumes the craft was designed strictly for the vacuum of space and wasn’t particularly aerodynamic. for example, enormous solar sails as currently envisioned would fare poorly with a dust cloud encounter at significant speed .) multiply that by the number of dust clouds a craft might encounter and an interstellar mission could take much, much longer than anyone anticipated .
for example, p. caselli et al. from the harvard - smithsonian center for astrophysics presented a paper (pdf) on j = 1 → 0 transition of n 2 h + at 93 ghz toward the quiescent low - mass cloud core l1512 in taurus, back in 1995. that is 18 years ago !
note: the cosmic hot interstellar plasma spectrometer (chips) is a university - class explorer (unex) mission at uc berkeley funded by nasa .
during the sun' s journey through the galaxy it encounters a range of environments, and interstellar densities ranging from 10 - 5 to 10 5 atoms / cm 3 are observed in our galactic neighborhood. hydrodynamic simulations show that if the solar system were to enter a typical diffuse cloud with a density of 10 atoms / cm 3, the size of the heliosphere would shrink by nearly a factor of ten, with significant effects on the interplanetary environment at 1 au. by targeting interstellar probe to fly upstream of the sun' s motion, it will explore the future environment of the solar system over the coming decades .
astronomers call it
the local bubble .
it' s peanut - shaped, about 300 light years long, and filled with almost nothing. gas inside the bubble is very thin (0. 001 atoms per cubic centimeter) and very hot (a million degrees) - - that' s 1000 times less dense and 100 to 100, 000 times hotter than ordinary interstellar material .
that local fluff image was apod feb 10, 2002. maybe one of the contact pages reachable from there may lead to an involved scientist who would just love to share his / her expertise and / or graphical and / or other data .
magnetic fields play an important (sometimes dominant) role in the evolution of gas clouds in the galaxy, but the strength and orientation of the field in the interstellar medium near the heliosphere has been poorly constrained. previous estimates of the field strength range from 1. 8 - 2. 5mug and the field was thought to be parallel to the galactic plane or inclined by 38 - 60° (ref. 2) or 60 - 90° (ref. 3) to this plane. these estimates relied either on indirect observational inferences or modelling in which the interstellar neutral hydrogen was not taken into account. here we report measurements of the deflection of the solar wind plasma flows in the heliosheath to determine the magnetic field strength and orientation in the interstellar medium. we find that the field strength in the local interstellar medium is 3. 7 - 5. 5mug. the field is tilted ~ 20 - 30° from the interstellar medium flow direction (resulting from the peculiar motion of the sun in the galaxy) and is at an angle of about 30° from the galactic plane. we conclude that the interstellar medium field is turbulent or has a distortion in the solar vicinity .
like interstellar neutrals, galactic cosmic rays allow us to probe the interstellar medium, with the distinction being that their origin is not necessarily local. however, unlike interstellar neutrals, galactic cosmic rays, being charged, respond to the (electro) magnetic structure of the heliosphere - lism interaction region. observations (mcdonald et al. , 2000) and models are beginning to use galactic cosmic rays flowing into the heliosphere to infer the structure of the boundary regions. such studies can be accomplished only by spacecraft placed far out in the heliosphere since diffusion effectively washes out any signature or imprint of the heliospheric boundaries on the cosmic ray flux observed within 40 to 50 au (florinski et al. , 2003) .
as i mentioned above, crawford’s paper delves deeply into the rationale for an interstellar mission, going beyond the interstellar medium question to address planetary and stellar studies and astrobiology. it’s a fascinating rationale for undertaking these studies and continuing to advocate precursor missions. and note this final caveat re alpha centauri as a destination :
the space between the stars is filled with gas and dust. spectacular displays of this interstellar medium (ism) can be found in star - forming regions where new stars are being created from the ism, as well as in planetary nebulae and supernova remnants where old stars are returing much of their mass back into space. i explore the region just around the sun, within approximately 100 pc, which is home to the local interstellar medium (lism). here we find a suite of warm, modest density, partially ionized clouds (see figure below) .
right: the brightest star in the sco - cen star - forming cloud is the red giant antares, which illuminates the yellow nebula in the upper - left corner of this image. antares might be the next star to explode in sco - cen, but at 500 light years it is a safe distance from earth. [ more ]
draine, b. t. & salpeter, e. e. destruction mechanisms for interstellar dust. astrophys. j. 231, 438–455 (1979) .
n. v. pogorelov, a. y. semenov, solar wind interaction with the magnetized interstellar medium. shock - capturing modeling. astron. astrophys .
linsky, j. l. , mobius, e. , izmodenov, v. v. , and von steiger, r. (eds .): 2009 ,
from the outer heliosphere to the local bubble
, space sciences reviews, 143
“i recall reading about smoke particle shield, although i do not recall the source. once cruising speed is reached, a probe moves out significantly ahead of the main spacecraft and generates a very large cloud of smoke particles that leads the spacecraft for the entire journey. the idea is that the smoke cloud will intercept and atomize the majority of the dust particles before the main spacecraft reaches that area of space. ” hmmm. surely that would take quite a bit of dust, since the smoke would be disappated eventually and need replacing? i suppose you could hold a plasma shield, and idea i’ve been considering – the heat to keep it ionized might come from the energy of vaporization ?
issues like this further highlight the difficulty in making interstellar voyages. it will certainly be possible, but there will be many challenges to be met by innovative ideas .
p. a. isenberg, w. c. feldman, electron - impact ionization of interstellar hydrogen and helium at interplanetary shocks. geophys. res. lett .
m. witte, kinetic parameters of interstellar neutral helium. review of results obtained during one solar cycle with the ulysses / gas - instrument. astron. astrophys .
and neutral atoms are coupled weakly but directly through various kinetic processes, these being charge exchange, photoionization, recombination, and electron - impact ionization, besides direct collisions between the neutral atoms and charged particles. the weak coupling of neutral interstellar hydrogen and plasma affects both interstellar hydrogen and plasma distributions in important ways. in the partially
as mankind begins to travel further outside the solar system, we’ll need to start thinking about how to shield ourselves from the local fluff and other gas clouds we may travel through. but for the time being, we should probably just focus on planets closer to home .
i had a look round yesterday, but i couldn' t find any decent maps of the local fluff. you might try fitting the picture you posted to this map of our neighbourhood. it' s approx the same scale as the fluff, 20 - 30ly .
heck, p. et al. interstellar residence times of presolar sic dust grains from the murchison carbonaceous meteorite. astrophys. j. 698, 1155 (2009) .
linsky, jeffrey l. : 2009 ,
solving the mysteries of the diffuse interstellar medium with high - resolution spectroscopy
, astrophysics and space science, 320, 85
the interaction of the solar wind with the local interstellar medium is characterized by the self - consistent coupling of solar wind plasma, both upstream and downstream of the heliospheric termination shock, the interstellar plasma, and the neutral atom component of interstellar and solar wind origin. the complex coupling results in the creation of new plasma components (pickup ions), turbulence, and anomalous cosmic rays, and new populations of neutral atoms and their coupling can lead to energetic neutral atoms that can be detected at 1 au. in this review, we discuss the interaction and coupling of global sized structures (the heliospheric boundary regions) and kinetic physics (the distributions that are responsible for the creation of energetic neutral atoms) based on models that have been developed by the university of alabama in huntsville group.
the local interstellar cloud ( lic ) , also known as the local fluff , is the interstellar cloud roughly 30 light-years ( 9.2 pc ) across through which the solar system is currently moving . it is currently unknown if the sun is embedded in the local interstellar cloud , or in the region where the local interstellar cloud is interacting with the neighboring g-cloud . 
the local interstellar cloud (lic), also known as the local fluff, is the interstellar cloud roughly 30 light-years (9.2 pc) across through which the solar system is currently moving. it is currently unknown if the sun is embedded in the local interstellar cloud, or in the region where the local interstellar cloud is interacting with the neighboring g-cloud.
the local interstellar cloud (lic), also known as the local fluff, is the interstellar cloud roughly 30 light-years (9.2 pc) across through which the solar system is currently moving. it is currently unknown if the sun is embedded in the local interstellar cloud, or in the region where the local interstellar cloud is interacting with the neighboring g-cloud.