In astronomy and planetary science , a magnetosphere is a region of space surrounding an astronomical object in which charged particles are affected by that object's magnetic field . It is created by a celestial body with an active interior dynamo .
84-503: The heliosphere is the magnetosphere , astrosphere , and outermost atmospheric layer of the Sun . It takes the shape of a vast, tailed bubble-like region of space . In plasma physics terms, it is the cavity formed by the Sun in the surrounding interstellar medium . The "bubble" of the heliosphere is continuously "inflated" by plasma originating from the Sun, known as the solar wind . Outside
168-528: A 4-lobed tail on the Solar System's heliosphere. The heliopause is the final known boundary between the heliosphere and the interstellar space that is filled with material, especially plasma, not from the Earth's own star, the Sun, but from other stars. Even so, just outside the heliosphere (i.e. the "solar bubble") there is a transitional region, as detected by Voyager 1 . Just as some interstellar pressure
252-441: A deflated croissant. The solar wind consists of particles ( ionized atoms from the solar corona ) and fields like the magnetic field that are produced from the Sun and stream out into space. Because the Sun rotates once approximately every 25 days, the heliospheric magnetic field transported by the solar wind gets wrapped into a spiral. The solar wind affects many other systems in the Solar System; for example, variations in
336-403: A distance of several hundred kilometers above Earth's surface. Earth's magnetopause has been compared to a sieve because it allows solar wind particles to enter. Kelvin–Helmholtz instabilities occur when large swirls of plasma travel along the edge of the magnetosphere at a different velocity from the magnetosphere, causing the plasma to slip past. This results in magnetic reconnection , and as
420-474: A distinct maximum and minimum of solar wind activity, is thought to be significant. On a broader scale, the motion of the heliosphere through the fluid medium of the ISM results in an overall comet-like shape. The solar wind plasma which is moving roughly "upstream" (in the same direction as the Sun's motion through the galaxy) is compressed into a nearly-spherical form, whereas the plasma moving "downstream" (opposite
504-403: A potential difference between the day side and the night side. Many astronomical objects generate and maintain magnetospheres. In the Solar System this includes the Sun, Mercury , Earth , Jupiter , Saturn , Uranus , Neptune , and Ganymede . The magnetosphere of Jupiter is the largest planetary magnetosphere in the Solar System, extending up to 7,000,000 kilometers (4,300,000 mi) on
588-519: A radio emission in the 14-30 MHz band was detected from the Tau Boötis system, likely associated with cyclotron radiation from the poles of Tau Boötis b a signature of a planetary magnetic field. In 2021 a magnetic field generated by HAT-P-11b became the first to be confirmed. The first unconfirmed detection of a magnetic field generated by a terrestrial exoplanet was found in 2023 on YZ Ceti b . Merav Opher Merav Opher
672-424: A region of hot hydrogen, a structure called the "hydrogen wall" may be between the bow shock and the heliopause. The wall is composed of interstellar material interacting with the edge of the heliosphere. One paper released in 2013 studied the concept of a bow wave and hydrogen wall. Another hypothesis suggests that the heliopause could be smaller on the side of the Solar System facing the Sun's orbital motion through
756-421: A relatively constant pressure associated with it; the pressure from the solar wind decreases with the square of the distance from the Sun. As one moves far enough away from the Sun, the pressure of the solar wind drops to where it can no longer maintain supersonic flow against the pressure of the interstellar medium, at which point the solar wind slows to below its speed of sound, causing a shock wave . Further from
840-492: A simple magnetic dipole . Farther out, field lines can be significantly distorted by the flow of electrically conducting plasma , as emitted from the Sun (i.e., the solar wind ) or a nearby star. Planets having active magnetospheres, like the Earth, are capable of mitigating or blocking the effects of solar radiation or cosmic radiation ; in Earth's case, this protects living organisms from harm. Interactions of particles and atmospheres with magnetospheres are studied under
924-409: Is a broad transitional region between the termination shock and the heliosphere's outmost edge, the " heliopause ". The overall shape of the heliosphere resembles that of a comet , being roughly spherical on one side to around 100 astronomical units (AU), and on the other side being tail shaped, known as the "heliotail", trailing for several thousands of AUs. Two Voyager program spacecraft explored
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#17327724801431008-647: Is a professor of astronomy at Boston University known for her work on the heliosphere , the cocoon formed by the wind emanated from the Sun as it travels in the Galaxy. In 2021 she was named a William Bentinck-Smith Fellow at the Harvard Radcliffe Institute . Opher was born in Israel and lived there until 1978 when she moved to Brazil with her parents. In 1992 and 1998, Opher received her B.S. in physics and her Ph.D. in physics and astronomy from
1092-456: Is balanced with the pressure from the solar wind. It is the convergence of the shocked solar wind from the magnetosheath with the magnetic field of the object and plasma from the magnetosphere. Because both sides of this convergence contain magnetized plasma, the interactions between them are complex. The structure of the magnetopause depends upon the Mach number and beta of the plasma, as well as
1176-572: Is higher than the local wave speed , forming a disk of shallow, rapidly diverging flow (analogous to the tenuous, supersonic solar wind). Around the periphery of the disk, a shock front or wall of water forms; outside the shock front, the water moves slower than the local wave speed (analogous to the subsonic interstellar medium). Evidence presented at a meeting of the American Geophysical Union in May 2005 by Ed Stone suggests that
1260-605: Is not opposed by the object's magnetic field. In this case, the solar wind interacts with the atmosphere or ionosphere of the planet (or surface of the planet, if the planet has no atmosphere). Venus has an induced magnetic field, which means that because Venus appears to have no internal dynamo effect , the only magnetic field present is that formed by the solar wind's wrapping around the physical obstacle of Venus (see also Venus' induced magnetosphere ). When R C F ≈ R P {\displaystyle R_{\rm {CF}}\approx R_{\rm {P}}} ,
1344-408: Is that of a four-leaf clover. The particles in the tail do not shine, therefore it cannot be seen with conventional optical instruments. IBEX made the first observations of the heliotail by measuring the energy of " energetic neutral atoms ", neutral particles created by collisions in the Solar System's boundary zone. The tail has been shown to contain fast and slow particles; the slow particles are on
1428-518: The Solar System and will eventually pass through the heliopause. Contact to Pioneer 10 and 11 has been lost. Rather than a comet-like shape, the heliosphere appears to be bubble-shaped according to data from Cassini ' s Ion and Neutral Camera (MIMI / INCA). Rather than being dominated by the collisions between the solar wind and the interstellar medium, the INCA ( ENA ) maps suggest that
1512-466: The Solar System with the interstellar medium , solar wind , and shocks in the lower corona, T-Tauri and Solar-Like Stars. In 2001, Opher began work on the heliosphere while she was a postdoctoral student at the Jet Propulsion lab. Her researcher focuses on how the solar wind shapes the heliosphere, the protective atmospheric shield between Earth and the rest of the galaxy, where she has shown
1596-414: The Sun 's solar wind is stopped by the interstellar medium ; where the solar wind's strength is no longer great enough to push back the stellar winds of the surrounding stars. This is the boundary where the interstellar medium and solar wind pressures balance. The crossing of the heliopause should be signaled by a sharp drop in the temperature of solar wind-charged particles, a change in the direction of
1680-462: The University of São Paulo . Following her Ph.D., Opher was a postdoctoral investigator at the University of California, Los Angeles from 1999 until 2001. She was a Caltech Scholar at NASA's Jet Propulsion Laboratory and at University of Michigan from 2001-2004. She was on the faculty of George Mason University from 2005 until 2010, at which point she moved to Boston University , where she
1764-531: The Voyager 1 spacecraft passed the termination shock in December 2004, when it was about 94 AU from the Sun, by virtue of the change in magnetic readings taken from the craft. In contrast, Voyager 2 began detecting returning particles when it was only 76 AU from the Sun, in May 2006. This implies that the heliosphere may be irregularly shaped, bulging outwards in the Sun's northern hemisphere and pushed inward in
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#17327724801431848-644: The heliospheric magnetic field and the solar wind from the Sun. Three major sections from the beginning of the heliosphere to its edge are the termination shock, the heliosheath, and the heliopause. Five spacecraft have returned much of the data about its furthest reaches, including Pioneer 10 (1972–1997; data to 67 AU), Pioneer 11 (1973–1995; 44 AU), Voyager 1 and Voyager 2 (launched 1977, ongoing), and New Horizons (launched 2006). A type of particle called an energetic neutral atom (ENA) has also been observed to have been produced from its edges. Except for regions near obstacles such as planets or comets ,
1932-438: The interstellar medium , its velocity slows to a stop. The point where the solar wind becomes slower than the speed of sound is called the termination shock ; the solar wind continues to slow as it passes through the heliosheath leading to a boundary called the heliopause , where the interstellar medium and solar wind pressures balance. The termination shock was traversed by Voyager 1 in 2004, and Voyager 2 in 2007. It
2016-707: The Apollo program the Solar wind was measured on the Moon via the Solar Wind Composition Experiment . Some examples of Earth surface based Solar observatories include the McMath–Pierce solar telescope or the newer GREGOR Solar Telescope , and the refurbished Big Bear Solar Observatory . The heliosphere is the area under the influence of the Sun; the two major components to determining its edge are
2100-547: The Cahill and Amazeen observation in 1963 of a sudden decrease in magnetic field strength near the noon-time meridian, later was named the magnetopause . By 1983, the International Cometary Explorer observed the magnetotail, or the distant magnetic field. Magnetospheres are dependent on several variables: the type of astronomical object, the nature of sources of plasma and momentum, the period of
2184-400: The Sun's motion) flows out for a much greater distance before giving way to the ISM, defining the long, trailing shape of the heliotail. The limited data available and the unexplored nature of these structures have resulted in many theories as to their form. In 2020, Merav Opher led the team of researchers who determined that the shape of the heliosphere is a crescent that can be described as
2268-426: The Sun's own magnetic field are carried outward by the solar wind, producing geomagnetic storms in the Earth's magnetosphere . The heliospheric current sheet is a ripple in the heliosphere created by the rotating magnetic field of the Sun. It marks the boundary between heliospheric magnetic field regions of opposite polarity. Extending throughout the heliosphere, the heliospheric current sheet could be considered
2352-427: The Sun, and a large increase in galactic cosmic rays. The flow of the interstellar medium (ISM) into the heliosphere has been measured by at least 11 different spacecraft as of 2013. By 2013, it was suspected that the direction of the flow had changed over time. The flow, coming from Earth's perspective from the constellation Scorpius, has probably changed direction by several degrees since the 1970s. Predicted to be
2436-411: The Sun, the termination shock is followed by heliopause, where the two pressures become equal and solar wind particles are stopped by the interstellar medium. Other termination shocks can be seen in terrestrial systems; perhaps the easiest may be seen by simply running a water tap into a sink creating a hydraulic jump . Upon hitting the floor of the sink, the flowing water spreads out at a speed that
2520-422: The Sun. In 2004, Voyager 1 crossed the Sun 's termination shock, followed by Voyager 2 in 2007. The shock arises because solar wind particles are emitted from the Sun at about 400 km/s, while the speed of sound (in the interstellar medium) is about 100 km/s. The exact speed depends on the density, which fluctuates considerably. The interstellar medium, although very low in density, nonetheless has
2604-435: The bow shock, the stellar wind plasma gains a substantial anisotropy , leading to various plasma instabilities upstream and downstream of the bow shock. The magnetosheath is the region of the magnetosphere between the bow shock and the magnetopause. It is formed mainly from shocked solar wind, though it contains a small amount of plasma from the magnetosphere. It is an area exhibiting high particle energy flux , where
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2688-407: The bubbles in 2007 and 2008, respectively. The probably sausage-shaped bubbles are formed by magnetic reconnection between oppositely oriented sectors of the solar magnetic field as the solar wind slows down. They probably represent self-contained structures that have detached from the interplanetary magnetic field . At a distance of about 113 AU, Voyager 1 detected a 'stagnation region' within
2772-402: The constellation Cetus has been shown to have both a debris tail of ejecta from the star and a distinct shock in the direction of its movement through space (at over 130 kilometers per second). The precise distance to and shape of the heliopause are still uncertain. Interplanetary/interstellar spacecraft such as Pioneer 10 , Pioneer 11 and New Horizons are traveling outward through
2856-448: The dayside and almost to the orbit of Saturn on the nightside. Jupiter's magnetosphere is stronger than Earth's by an order of magnitude , and its magnetic moment is approximately 18,000 times larger. Venus , Mars , and Pluto , on the other hand, have no magnetic field. This may have had significant effects on their geological history. It is theorized that Venus and Mars may have lost their primordial water to photodissociation and
2940-413: The direction and magnitude of the magnetic field varies erratically. This is caused by the collection of solar wind gas that has effectively undergone thermalization . It acts as a cushion that transmits the pressure from the flow of the solar wind and the barrier of the magnetic field from the object. The magnetopause is the area of the magnetosphere wherein the pressure from the planetary magnetic field
3024-449: The direction opposite to the Sun's path through space. At its windward side, its thickness is estimated to be between 10 and 100 AU. Voyager project scientists have determined that the heliosheath is not "smooth" – it is rather a "foamy zone" filled with magnetic bubbles, each about 1 AU wide. These magnetic bubbles are created by the impact of the solar wind and the interstellar medium. Voyager 1 and Voyager 2 began detecting evidence of
3108-508: The existence of the Van Allen radiation belt (located in the inner region of Earth's magnetosphere), with the follow-up Explorer 3 later that year definitively proving its existence. Also during 1958, Eugene Parker proposed the idea of the solar wind , with the term 'magnetosphere' being proposed by Thomas Gold in 1959 to explain how the solar wind interacted with the Earth's magnetic field. The later mission of Explorer 12 in 1961 led by
3192-653: The galaxy. It may also vary depending on the current velocity of the solar wind and the local density of the interstellar medium. It is known to lie far outside the orbit of Neptune . The mission of the Voyager ;1 and 2 spacecraft is to find and study the termination shock, heliosheath, and heliopause. Meanwhile, the IBEX mission is attempting to image the heliopause from Earth orbit within two years of its 2008 launch. Initial results (October 2009) from IBEX suggest that previous assumptions are insufficiently cognizant of
3276-469: The galaxy." In October 2010, significant changes were detected in the ribbon after 6 months, based on the second set of IBEX observations. IBEX data did not support the existence of a bow shock, but there might be a 'bow wave' according to one study. Examples of missions that have or continue to collect data related to the heliosphere include: During a total eclipse the high-temperature corona can be more readily observed from Earth solar observatories. During
3360-490: The gases in the interstellar medium . This takes place in several stages: The termination shock is the point in the heliosphere where the solar wind slows down to subsonic speed (relative to the Sun) because of interactions with the local interstellar medium . This causes compression , heating, and a change in the magnetic field . In the Solar System , the termination shock is believed to be 75 to 90 astronomical units from
3444-423: The heliopause as of 25 August 2012. This was at a distance of 121 AU (1.81 × 10 km) from the Sun. Contrary to predictions, data from Voyager 1 indicates the magnetic field of the galaxy is aligned with the solar magnetic field. On November 5, 2018, the Voyager 2 mission detected a sudden decrease in the flux of low-energy ions. At the same time, the level of cosmic rays increased. This demonstrated that
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3528-424: The heliopause. In the summer of 2013, NASA announced that Voyager 1 had reached interstellar space as of 25 August 2012. In December 2012, NASA announced that in late August 2012, Voyager 1, at about 122 au (1.83 × 10 km; 1.13 × 10 mi) from the Sun, entered a new region they called the "magnetic highway", an area still under the influence of the Sun but with some dramatic differences. Pioneer 10
3612-427: The heliosheath, starting around 113 au (1.69 × 10 km; 1.05 × 10 mi), detected by Voyager 1 in 2010. There, the solar wind velocity drops to zero, the magnetic field intensity doubles, and high-energy electrons from the galaxy increase 100-fold. Starting in May 2012 at 120 au (1.8 × 10 km; 1.1 × 10 mi), Voyager 1 detected a sudden increase in cosmic rays, an apparent sign of approach to
3696-410: The heliosheath. In this region, the solar wind slowed to zero, the magnetic field intensity doubled and high-energy electrons from the galaxy increased 100-fold. At about 122 AU, the spacecraft entered a new region that Voyager project scientists called the "magnetic highway", an area still under the influence of the Sun but with some dramatic differences. The heliopause is the theoretical boundary where
3780-414: The heliosphere in different overall directions away from the Sun. Data obtained from Pioneer and Voyager spacecraft helped corroborate the detection of a hydrogen wall. Voyagers 1 and 2 were launched in 1977 and operated continuously to at least the late 2010s and encountered various aspects of the heliosphere past Pluto. In 2012 Voyager 1 is thought to have passed through heliopause, and Voyager 2 did
3864-431: The heliosphere is dominated by material emanating from the Sun, although cosmic rays , fast-moving neutral atoms , and cosmic dust can penetrate the heliosphere from the outside. Originating at the extremely hot surface of the corona , solar wind particles reach escape velocity , streaming outwards at 300 to 800 km/s (671 thousand to 1.79 million mph or 1 to 2.9 million km/h). As it begins to interact with
3948-464: The heliosphere than anyone previously believed" "No one knows what is creating the ENA (energetic neutral atoms) ribbon, ..." "The IBEX results are truly remarkable! What we are seeing in these maps does not match with any of the previous theoretical models of this region. It will be exciting for scientists to review these ( ENA ) maps and revise the way we understand our heliosphere and how it interacts with
4032-437: The heliosphere, and thus the Solar System's tail. It can be compared to the tail of a comet (however, a comet's tail does not stretch behind it as it moves; it is always pointing away from the Sun). The tail is a region where the Sun's solar wind slows down and ultimately escapes the heliosphere, slowly evaporating because of charge exchange. The shape of the heliotail (newly found by NASA's Interstellar Boundary Explorer – IBEX),
4116-460: The heliosphere, this solar plasma gives way to the interstellar plasma permeating the Milky Way . As part of the interplanetary magnetic field , the heliosphere shields the Solar System from significant amounts of cosmic ionizing radiation ; uncharged gamma rays are, however, not affected. Its name was likely coined by Alexander J. Dessler , who is credited with the first use of the word in
4200-494: The heliosphere. Opher has written in The Hill about the dangers of space tourism for people where she describes the radiation coming through space and the need to better understand how the heliosphere filters this radiation before people can travel safely to other planets. As of 2021, Opher's research has been cited more than 4400 times and she has an h-index of 37. In 2008, Opher received an NSF Young Investigator Award,
4284-459: The interaction is controlled more by particle pressure and magnetic field energy density. Initial data from Interstellar Boundary Explorer (IBEX), launched in October 2008, revealed a previously unpredicted "very narrow ribbon that is two to three times brighter than anything else in the sky." Initial interpretations suggest that "the interstellar environment has far more influence on structuring
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#17327724801434368-472: The interstellar medium due to it shrinking the heliosphere to the Inner Solar System , which possibly had impacted Earth's past climate and human evolution. Despite its name, the heliosphere's shape is not a perfect sphere. Its shape is determined by three factors: the interstellar medium (ISM), the solar wind, and the overall motion of the Sun and heliosphere as it passes through the ISM. Because
4452-457: The largest structure in the Solar System and is said to resemble a "ballerina's skirt". The outer structure of the heliosphere is determined by the interactions between the solar wind and the winds of interstellar space. The solar wind streams away from the Sun in all directions at speeds of several hundred km/s in the Earth's vicinity. At some distance from the Sun, well beyond the orbit of Neptune , this supersonic wind slows down as it encounters
4536-404: The magnetic field is significantly distorted by the solar wind and its solar magnetic field. On the dayside of Earth, the magnetic field is significantly compressed by the solar wind to a distance of approximately 65,000 kilometers (40,000 mi). Earth's bow shock is about 17 kilometers (11 mi) thick and located about 90,000 kilometers (56,000 mi) from Earth. The magnetopause exists at
4620-419: The magnetic field lines break and reconnect, solar wind particles are able to enter the magnetosphere. On Earth's nightside, the magnetic field extends in the magnetotail, which lengthwise exceeds 6,300,000 kilometers (3,900,000 mi). Earth's magnetotail is the primary source of the polar aurora . Also, NASA scientists have suggested that Earth's magnetotail might cause "dust storms" on the Moon by creating
4704-563: The magnetic field, and an increase in the number of galactic cosmic rays . In May 2012, Voyager 1 detected a rapid increase in such cosmic rays (a 9% increase in a month, following a more gradual increase of 25% from January 2009 to January 2012), suggesting it was approaching the heliopause. Between late August and early September 2012, Voyager 1 witnessed a sharp drop in protons from the Sun, from 25 particles per second in late August, to about 2 particles per second by early October. In September 2013, NASA announced that Voyager 1 had crossed
4788-401: The magnetic field. The magnetopause changes size and shape as the pressure from the solar wind fluctuates. Opposite the compressed magnetic field is the magnetotail, where the magnetosphere extends far beyond the astronomical object. It contains two lobes, referred to as the northern and southern tail lobes. Magnetic field lines in the northern tail lobe point towards the object while those in
4872-482: The object's spin, the nature of the axis about which the object spins, the axis of the magnetic dipole, and the magnitude and direction of the flow of solar wind . The planetary distance where the magnetosphere can withstand the solar wind pressure is called the Chapman–Ferraro distance. This is usefully modeled by the formula wherein R P {\displaystyle R_{\rm {P}}} represents
4956-406: The outer reaches of the heliosphere, passing through the termination shock and the heliosheath. Voyager 1 encountered the heliopause on 25 August 2012, when the spacecraft measured a forty-fold sudden increase in plasma density . Voyager 2 traversed the heliopause on 5 November 2018. Because the heliopause marks the boundary between matter originating from the Sun and matter originating from
5040-441: The planet itself and its magnetic field both contribute. It is possible that Mars is of this type. The bow shock forms the outermost layer of the magnetosphere; the boundary between the magnetosphere and the ambient medium. For stars, this is usually the boundary between the stellar wind and interstellar medium ; for planets, the speed of the solar wind there decreases as it approaches the magnetopause. Due to interactions with
5124-409: The primary opposition to the flow of solar wind is the magnetic field of the object. Mercury , Earth, Jupiter , Ganymede , Saturn , Uranus , and Neptune , for example, exhibit intrinsic magnetospheres. A magnetosphere is classified as "induced" when R C F ≪ R P {\displaystyle R_{\rm {CF}}\ll R_{\rm {P}}} , or when the solar wind
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#17327724801435208-507: The radius of the planet, B s u r f {\displaystyle B_{\rm {surf}}} represents the magnetic field on the surface of the planet at the equator, and V S W {\displaystyle V_{\rm {SW}}} represents the velocity of the solar wind: A magnetosphere is classified as "intrinsic" when R C F ≫ R P {\displaystyle R_{\rm {CF}}\gg R_{\rm {P}}} , or when
5292-401: The rest of the galaxy, spacecraft that depart the heliosphere (such as the two Voyagers) are in interstellar space . The heliosphere is thought to change significantly over the course of millions of years due to extrasolar effects such as closer super novas or the traversing interstellar medium of different densities. Evidence suggests that up to three million years ago Earth was exposed to
5376-702: The same in 2018 The twin Voyagers are the only man-made objects to have entered interstellar space. However, while they have left the heliosphere, they have not yet left the boundary of the Solar System which is considered to be the outer edge of the Oort Cloud . Upon passing the heliopause, Voyager 2 's Plasma Science Experiment (PLS) observed a sharp decline in the speed of solar wind particles on 5 November and there has been no sign of it since. The three other instruments on board measuring cosmic rays, low-energy charged particles, and magnetic fields also recorded
5460-436: The scientific literature in 1967. The scientific study of the heliosphere is heliophysics , which includes space weather and space climate . Flowing unimpeded through the Solar System for billions of kilometers, the solar wind extends far beyond even the region of Pluto until it encounters the " termination shock ", where its motion slows abruptly due to the outside pressure of the interstellar medium. The " heliosheath "
5544-546: The shape of the heliosphere is similar to a croissant and not a comet with a tail as previously thought. Opher's 2020 paper expanding on the crescent shape of the heliosphere was published in Nature Astronomy , featured on the cover of the July 2020 issue, and covered by the media. In 2021, Opher's research revealed that the stability of the heliosphere originates from the neutral hydrogen particles that interact with
5628-444: The side and the fast particles are encompassed in the center. The shape of the tail can be linked to the Sun sending out fast solar winds near its poles and slow solar winds near its equator more recently. The clover-shaped tail moves further away from the Sun, which makes the charged particles begin to morph into a new orientation. Cassini and IBEX data challenged the "heliotail" theory in 2009. In July 2013, IBEX results revealed
5712-411: The solar wind and the ISM are both fluid, the heliosphere's shape and size are also fluid. Changes in the solar wind, however, more strongly alter the fluctuating position of the boundaries on short timescales (hours to a few years). The solar wind's pressure varies far more rapidly than the outside pressure of the ISM at any given location. In particular, the effect of the 11-year solar cycle , which sees
5796-402: The solar wind. Pioneer 10 returned scientific data until March 1997, including data on the solar wind out to about 67 AU. It was also contacted in 2003 when it was a distance of 7.6 billion miles from Earth (82 AU), but no instrument data about the solar wind was returned then. Voyager 1 surpassed the radial distance from the Sun of Pioneer 10 at 69.4 AU on 17 February 1998, because it
5880-510: The solar wind. A strong magnetosphere greatly slows this process. Magnetospheres generated by exoplanets are thought to be common, though the first discoveries did not come until the 2010s. In 2014, a magnetic field around HD 209458 b was inferred from the way hydrogen was evaporating from the planet. In 2019, the strength of the surface magnetic fields of 4 hot Jupiters were estimated and ranged between 20 and 120 gauss compared to Jupiter's surface magnetic field of 4.3 gauss. In 2020,
5964-431: The south. The heliosheath is the region of the heliosphere beyond the termination shock. Here the wind is slowed, compressed, and made turbulent by its interaction with the interstellar medium. At its closest point, the inner edge of the heliosheath lies approximately 80 to 100 AU from the Sun. A proposed model hypothesizes that the heliosheath is shaped like the coma of a comet, and trails several times that distance in
6048-420: The southern tail lobe point away. The tail lobes are almost empty, with few charged particles opposing the flow of the solar wind. The two lobes are separated by a plasma sheet, an area where the magnetic field is weaker, and the density of charged particles is higher. Over Earth's equator , the magnetic field lines become almost horizontal, then return to reconnect at high latitudes. However, at high altitudes,
6132-403: The spacecraft crossed the heliopause at a distance of 119 AU (1.78 × 10 km) from the Sun. Unlike Voyager 1 , the Voyager 2 spacecraft did not detect interstellar flux tubes while crossing the heliosheath. NASA also collected data from the heliopause remotely during the suborbital SHIELDS mission in 2021. The heliotail is the several thousand astronomical units long tail of
6216-449: The specialized scientific subjects of plasma physics , space physics , and aeronomy . Study of Earth's magnetosphere began in 1600, when William Gilbert discovered that the magnetic field on the surface of Earth resembled that of a terrella , a small, magnetized sphere. In the 1940s, Walter M. Elsasser proposed the model of dynamo theory , which attributes Earth's magnetic field to the motion of Earth's iron outer core . Through
6300-399: The transition. The observations complement data from NASA's IBEX mission. NASA is also preparing an additional mission, Interstellar Mapping and Acceleration Probe ( IMAP ) which is due to launch in 2025 to capitalize on Voyager 's observations. Magnetosphere In the space environment close to a planetary body with a dipole magnetic field such as Earth, the field lines resemble
6384-492: The true complexities of the heliopause. In August 2018, long-term studies about the hydrogen wall by the New Horizons spacecraft confirmed results first detected in 1992 by the two Voyager spacecraft . Although the hydrogen is detected by extra ultraviolet light (which may come from another source), the detection by New Horizons corroborates the earlier detections by Voyager at a much higher level of sensitivity. It
6468-497: The use of magnetometers , scientists were able to study the variations in Earth's magnetic field as functions of both time and latitude and longitude. Beginning in the late 1940s, rockets were used to study cosmic rays . In 1958, Explorer 1 , the first of the Explorer series of space missions, was launched to study the intensity of cosmic rays above the atmosphere and measure the fluctuations in this activity. This mission observed
6552-676: Was detected as early as 2004, some of the Sun's material seeps into the interstellar medium. The heliosphere is thought to reside in the Local Interstellar Cloud inside the Local Bubble , which is a region in the Orion Arm of the Milky Way Galaxy . Outside the heliosphere, there is a forty-fold increase in plasma density. There is also a radical reduction in the detection of certain types of particles from
6636-494: Was determined it probably does not exist. This conclusion resulted from new measurements: The velocity of the LISM (local interstellar medium) relative to the Sun's was previously measured to be 26.3 km/s by Ulysses , whereas IBEX measured it at 23.2 km/s. This phenomenon has been observed outside the Solar System, around stars other than the Sun, by NASA's now retired orbital GALEX telescope. The red giant star Mira in
6720-613: Was launched in March 1972, and within 10 hours passed by the Moon; over the next 35 years or so the mission would be the first out, laying out many firsts of discoveries about the nature of heliosphere as well as Jupiter's impact on it. Pioneer 10 was the first spacecraft to detect sodium and aluminum ions in the solar wind, as well as helium in the inner Solar System. In November 1972, Pioneer 10 encountered Jupiter's enormous (compared to Earth) magnetosphere and would pass in and out of it and its heliosphere 17 times charting its interaction with
6804-427: Was long hypothesized that the Sun produces a "shock wave" in its travels within the interstellar medium. It would occur if the interstellar medium is moving supersonically "toward" the Sun, since its solar wind moves "away" from the Sun supersonically. When the interstellar wind hits the heliosphere it slows and creates a region of turbulence. A bow shock was thought to possibly occur at about 230 AU, but in 2012 it
6888-669: Was promoted to professor in 2020. Opher is the director of the SHIELD DRIVE Science Center at Boston University, a project funded by NASA that will study the shape of the heliosphere. She has served on the Space Studies Board at the National Academy of Sciences which evaluated the progress of space and solar physics. Her research interests include computational and theoretical plasma physics in space and astrophysics , interaction of
6972-400: Was thought that beyond the heliopause there was a bow shock , but data from Interstellar Boundary Explorer suggested the velocity of the Sun through the interstellar medium is too low for it to form. It may be a more gentle "bow wave". Voyager data led to a new theory that the heliosheath has "magnetic bubbles" and a stagnation zone. Also, there were reports of a "stagnation region" within
7056-475: Was traveling faster, gaining about 1.02 AU per year. On July 18, 2023, Voyager 2 overtook Pioneer 10 as the second most distant human-made object from the Sun. Pioneer 11 , launched a year after Pioneer 10 , took similar data as Pioneer out to 44.7 AU in 1995 when that mission was concluded. Pioneer 11 had a similar instrument suite as 10 but also had a flux-gate magnetometer. Pioneer and Voyager spacecraft were on different trajectories and thus recorded data on
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