The End of the Sun Rays

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In turn, gravity pulls the ISM material together to form more stars. What is the bow shock or bow wave? A bow shock or wave will form in front of the heliosphere, as the Sun moves through the interstellar medium. A bow wave is similar to what happens at the prow of a boat, while a bow shock is similar to the shockwave that forms in front of a supersonic jet. If the Sun is moving faster than the speed of sound in the interstellar medium, a bow shock will form. Otherwise, if the Sun is not traveling that fast a bow wave will form. What is the heliopause? The heliopause is the boundary between the Sun's solar wind and the interstellar medium.

The solar wind blows a "bubble" known as the heliosphere into the interstellar medium. The outer border of this "bubble" is where the solar wind's strength is no longer great enough to push back the interstellar medium. This is known as the heliopause, and is often considered to be the outer border of the solar system. The zone between the termination shock and the heliopause is known as the heliosheath. What is the termination shock? The termination shock is the boundary marking one of the outer limits of the Sun's influence, and is one boundary of the solar system.

It is where the bubble of solar wind particles slows down so that the particles are traveling slower than the speed of sound. The solar wind particles slow down when they begin to press into the interstellar medium. The solar wind is made of plasma, and when it slows in this way, it goes through many changes. The solar wind plasma gets smooshed together, or compressed like people crowded together in a tiny room. When it is compressed, it also becomes much hotter, in the same way as a bicycle pump heats up in your hand when you vigorously inflate a tire. Also, the solar wind carries outward some of the Sun's magnetic field, which now gets stronger at the termination shock and twists around.

We have only two direct measurements of the distance to the Termination Shock. These measurements were made by Voyager 1 and Voyager 2. The solar wind flow also represents a strong outward pressure. Close to the Sun, the solar wind has a high pressure and can easily push the interstellar medium away from the Sun. Further away from the Sun, the pressure from the Interstellar Medium is strong enough to slow down and eventually stop the flow solar wind from traveling into space.

The place where the speed of the solar wind becomes slower than the speed of sound is called the termination shock. A similar shock is formed when you run water from a faucet into a sink. When the stream of water hits the sink basin, the flowing water spreads out at a relatively fast speed, forming a disk of shallow water that quickly moves outward, like the solar wind inside the termination shock.

Around the edge of the disk, a shock front or wall of water forms; outside the shock front, the water moves relatively slower, like outside the termination shock. Remember, the water shock is only 2-dimensional or flat. The Boundary of our solar system is 3-dimensional like a sphere. How does the solar system boundary affect me? This graph depicts the fraction of high energy cosmic rays greater than MeV that pass through the boundary of the solar system.

There is a small drop off in the number that make it through to the heliopause. The solar system boundary may be defined as the region where the solar wind slows down and interacts with the Interstellar Medium. If the solar system did not have a boundary, or if the boundary changed size so that it was inside the orbit of the Earth, then there would be at least 4 times the amount of cosmic rays in the solar system.

Luckily the Earth's magnetosphere protects us from some of the cosmic rays that come from outside our solar system. However, if there were a dramatic increase in the number of cosmic rays entering the solar system, it could change the amount of high energy cosmic rays that would be able to reach Earth's surface. Damage to the Earth's ozone layer could occur and cosmic rays may cause damage and mutation to DNA.

What are cosmic rays? These particles could be single protons, nuclei of different atoms or electrons. Cosmic rays are neither light nor beams of particles, so maybe they should be renamed energetic cosmic particles. Cosmic rays are often made when a star explodes. This is called a supernova. Some cosmic rays can be produced by the Sun and some can even come from as far away as other galaxies. These particles are very energetic, but also very small.

They rarely directly hit anything as they travel through space, but if they do it can cause nuclear reactions with atoms. These reactions are similar to the activities in particle accelerators. The Sun's heliosphere protects the planets and other objects in the solar system from some of these dangerous particles.

The Earth's magnetosphere and atmosphere protect life on Earth from cosmic rays that make it through the heliosphere. Studying the heliosphere will help us to prepare adequate shielding during future space travel How do cosmic rays affect DNA? Cosmic rays can seriously damage DNA. If DNA damage cannot be repaired by the cell, the cell could die. If the damage is copied into more cells, then a mutation could occur. Exposure to large amounts of cosmic rays could increase the risks for cancer, cataracts and neurological disorders.

The Sun Is Stranger Than Astrophysicists Imagined

Long term exposure to cosmic rays, or short intense bursts, could affect the evolution of life on Earth. What are energetic neutral atoms? ENAs are formed from particles that are ionized, meaning they have lost electrons. The Sun orbits the center of the Milky Way, and it is presently moving in the direction of the constellation of Cygnus. A simple model of the motion of a star in the galaxy gives the galactic coordinates X , Y , and Z as:. We take X 0 and Y 0 to be zero and Z 0 is estimated to be 17 parsecs. In the X, Y coordinates, the Sun describes an ellipse around the point, whose length in the Y direction is.

The oscillation in the Z direction takes the Sun. The Sun's orbit around the Milky Way is perturbed due to the non-uniform mass distribution in Milky Way, such as that in and between the galactic spiral arms. It has been argued that the Sun's passage through the higher density spiral arms often coincides with mass extinctions on Earth, perhaps due to increased impact events.

It is thought that the energy necessary to heat the corona is provided by turbulent motion in the convection zone below the photosphere, and two main mechanisms have been proposed to explain coronal heating. Currently, it is unclear whether waves are an efficient heating mechanism. Current research focus has therefore shifted towards flare heating mechanisms. Theoretical models of the Sun's development suggest that 3. Such a weak star would not have been able to sustain liquid water on Earth's surface, and thus life should not have been able to develop.

However, the geological record demonstrates that Earth has remained at a fairly constant temperature throughout its history, and that the young Earth was somewhat warmer than it is today. One theory among scientists is that the atmosphere of the young Earth contained much larger quantities of greenhouse gases such as carbon dioxide , methane than are present today, which trapped enough heat to compensate for the smaller amount of solar energy reaching it.

However, examination of Archaean sediments appears inconsistent with the hypothesis of high greenhouse concentrations. Instead, the moderate temperature range may be explained by a lower surface albedo brought about by less continental area and the "lack of biologically induced cloud condensation nuclei". This would have led to increased absorption of solar energy, thereby compensating for the lower solar output. The Sun has been an object of veneration in many cultures throughout human history.

Humanity's most fundamental understanding of the Sun is as the luminous disk in the sky , whose presence above the horizon creates day and whose absence causes night. In many prehistoric and ancient cultures, the Sun was thought to be a solar deity or other supernatural entity. Worship of the Sun was central to civilizations such as the ancient Egyptians , the Inca of South America and the Aztecs of what is now Mexico. In religions such as Hinduism , the Sun is still considered a god. The Egyptians portrayed the god Ra as being carried across the sky in a solar barque, accompanied by lesser gods, and to the Greeks, he was Helios , carried by a chariot drawn by fiery horses.

From the reign of Elagabalus in the late Roman Empire the Sun's birthday was a holiday celebrated as Sol Invictus literally "Unconquered Sun" soon after the winter solstice, which may have been an antecedent to Christmas. Regarding the fixed stars , the Sun appears from Earth to revolve once a year along the ecliptic through the zodiac , and so Greek astronomers categorized it as one of the seven planets Greek planetes , "wanderer" ; the naming of the days of the weeks after the seven planets dates to the Roman era.

In the early first millennium BC, Babylonian astronomers observed that the Sun's motion along the ecliptic is not uniform, though they did not know why; it is today known that this is due to the movement of Earth in an elliptic orbit around the Sun, with Earth moving faster when it is nearer to the Sun at perihelion and moving slower when it is farther away at aphelion. One of the first people to offer a scientific or philosophical explanation for the Sun was the Greek philosopher Anaxagoras.

He reasoned that it was not the chariot of Helios , but instead a giant flaming ball of metal even larger than the land of the Peloponnesus and that the Moon reflected the light of the Sun. In the 1st century AD, Ptolemy estimated the distance as 1, times the radius of Earth , approximately 7.

The theory that the Sun is the center around which the planets orbit was first proposed by the ancient Greek Aristarchus of Samos in the 3rd century BC, and later adopted by Seleucus of Seleucia see Heliocentrism. This view was developed in a more detailed mathematical model of a heliocentric system in the 16th century by Nicolaus Copernicus.

Observations of sunspots were recorded during the Han Dynasty BC—AD by Chinese astronomers , who maintained records of these observations for centuries. Averroes also provided a description of sunspots in the 12th century. Galileo posited that sunspots were on the surface of the Sun rather than small objects passing between Earth and the Sun. Arabic astronomical contributions include Albatenius ' discovery that the direction of the Sun's apogee the place in the Sun's orbit against the fixed stars where it seems to be moving slowest is changing.

Ibn Yunus observed more than 10, entries for the Sun's position for many years using a large astrolabe. From an observation of a transit of Venus in , the Persian astronomer and polymath Avicenna concluded that Venus is closer to Earth than the Sun. In , Isaac Newton observed the Sun's light using a prism , and showed that it is made up of light of many colors. In the early years of the modern scientific era, the source of the Sun's energy was a significant puzzle.

Characteristics of the sun

Lord Kelvin suggested that the Sun is a gradually cooling liquid body that is radiating an internal store of heat. Not until was a documented solution offered. Ernest Rutherford suggested that the Sun's output could be maintained by an internal source of heat, and suggested radioactive decay as the source. The theoretical concept of fusion was developed in the s by the astrophysicists Subrahmanyan Chandrasekhar and Hans Bethe. Hans Bethe calculated the details of the two main energy-producing nuclear reactions that power the Sun.

The first satellites designed for long term observation of the Sun from interplanetary space were NASA 's Pioneers 6, 7, 8 and 9, which were launched between and These probes orbited the Sun at a distance similar to that of Earth, and made the first detailed measurements of the solar wind and the solar magnetic field.

Pioneer 9 operated for a particularly long time, transmitting data until May In the s, two Helios spacecraft and the Skylab Apollo Telescope Mount provided scientists with significant new data on solar wind and the solar corona.

Sun - Wikipedia

The Helios 1 and 2 probes were U. This spacecraft was designed to observe gamma rays , X-rays and UV radiation from solar flares during a time of high solar activity and solar luminosity. Just a few months after launch, however, an electronics failure caused the probe to go into standby mode, and it spent the next three years in this inactive state. In Space Shuttle Challenger mission STSC retrieved the satellite and repaired its electronics before re-releasing it into orbit. The Solar Maximum Mission subsequently acquired thousands of images of the solar corona before re-entering Earth's atmosphere in June Launched in , Japan's Yohkoh Sunbeam satellite observed solar flares at X-ray wavelengths.

Mission data allowed scientists to identify several different types of flares, and demonstrated that the corona away from regions of peak activity was much more dynamic and active than had previously been supposed. Yohkoh observed an entire solar cycle but went into standby mode when an annular eclipse in caused it to lose its lock on the Sun. It was destroyed by atmospheric re-entry in All these satellites have observed the Sun from the plane of the ecliptic, and so have only observed its equatorial regions in detail. The Ulysses probe was launched in to study the Sun's polar regions.

It first travelled to Jupiter , to "slingshot" into an orbit that would take it far above the plane of the ecliptic. Elemental abundances in the photosphere are well known from spectroscopic studies, but the composition of the interior of the Sun is more poorly understood. A solar wind sample return mission, Genesis , was designed to allow astronomers to directly measure the composition of solar material. Two identical spacecraft were launched into orbits that cause them to respectively pull further ahead of and fall gradually behind Earth.

This enables stereoscopic imaging of the Sun and solar phenomena, such as coronal mass ejections. Its main instrument will be a coronagraph for studying the dynamics of the Solar corona. The brightness of the Sun can cause pain from looking at it with the naked eye ; however, doing so for brief periods is not hazardous for normal non-dilated eyes. Viewing the Sun through light-concentrating optics such as binoculars may result in permanent damage to the retina without an appropriate filter that blocks UV and substantially dims the sunlight.

When using an attenuating filter to view the Sun, the viewer is cautioned to use a filter specifically designed for that use. Some improvised filters that pass UV or IR rays, can actually harm the eye at high brightness levels. The sunlight that is destined for the eyepiece is reflected from an unsilvered surface of a piece of glass. Only a very small fraction of the incident light is reflected. The rest passes through the glass and leaves the instrument. If the glass breaks because of the heat, no light at all is reflected, making the device fail-safe.

Simple filters made of darkened glass allow the full intensity of sunlight to pass through if they break, endangering the observer's eyesight. Unfiltered binoculars can deliver hundreds of times as much energy as using the naked eye, possibly causing immediate damage. It is claimed that even brief glances at the midday Sun through an unfiltered telescope can cause permanent damage. Partial solar eclipses are hazardous to view because the eye's pupil is not adapted to the unusually high visual contrast: the pupil dilates according to the total amount of light in the field of view, not by the brightest object in the field.

During partial eclipses most sunlight is blocked by the Moon passing in front of the Sun, but the uncovered parts of the photosphere have the same surface brightness as during a normal day. This can damage or kill those cells, resulting in small permanent blind spots for the viewer. During sunrise and sunset , sunlight is attenuated because of Rayleigh scattering and Mie scattering from a particularly long passage through Earth's atmosphere, [] and the Sun is sometimes faint enough to be viewed comfortably with the naked eye or safely with optics provided there is no risk of bright sunlight suddenly appearing through a break between clouds.

Hazy conditions, atmospheric dust, and high humidity contribute to this atmospheric attenuation. An optical phenomenon , known as a green flash , can sometimes be seen shortly after sunset or before sunrise. The flash is caused by light from the Sun just below the horizon being bent usually through a temperature inversion towards the observer.

Light of shorter wavelengths violet, blue, green is bent more than that of longer wavelengths yellow, orange, red but the violet and blue light is scattered more, leaving light that is perceived as green. Ultraviolet light from the Sun has antiseptic properties and can be used to sanitize tools and water. It also causes sunburn , and has other biological effects such as the production of vitamin D and sun tanning.

Ultraviolet light is strongly attenuated by Earth's ozone layer , so that the amount of UV varies greatly with latitude and has been partially responsible for many biological adaptations, including variations in human skin color in different regions of the Earth. The Sun has eight known planets. The Solar System also has at least five dwarf planets , an asteroid belt , numerous comets , and a large number of icy bodies which lie beyond the orbit of Neptune.

Solar deities play a major role in many world religions and mythologies. From at least the 4th Dynasty of Ancient Egypt , the Sun was worshipped as the god Ra , portrayed as a falcon-headed divinity surmounted by the solar disk, and surrounded by a serpent. In the New Empire period, the Sun became identified with the dung beetle , whose spherical ball of dung was identified with the Sun.

Naked Science - Death of the Sun

In the form of the sun disc Aten , the Sun had a brief resurgence during the Amarna Period when it again became the preeminent, if not only, divinity for the Pharaoh Akhenaton. In the Bible , Malachi mentions the "Sun of Righteousness" sometimes translated as the "Sun of Justice" , [] which some Christians have interpreted as a reference to the Messiah Christ. It was adopted as the Sabbath day by Christians who did not have a Jewish background.

The symbol of light was a pagan device adopted by Christians, and perhaps the most important one that did not come from Jewish traditions. In paganism, the Sun was a source of life, giving warmth and illumination to mankind. It was the center of a popular cult among Romans, who would stand at dawn to catch the first rays of sunshine as they prayed. The celebration of the winter solstice which influenced Christmas was part of the Roman cult of the unconquered Sun Sol Invictus.

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Christian churches were built with an orientation so that the congregation faced toward the sunrise in the East. Tonatiuh , the Aztec god of the sun, was usually depicted holding arrows and a shield [] and was closely associated with the practice of human sacrifice. From Wikipedia, the free encyclopedia. This article is about the star. For other uses, see Sun disambiguation. For other uses, see The Sun disambiguation.

Star at the centre of the Solar System. Sun with sunspots and limb darkening as seen in visible light with solar filter. False-color photo of the Sun as seen in ultraviolet light wavelength of Main article: Sunlight. See also: Molecules in stars. Main article: Standard solar model. Main article: Solar core. Main article: Radiative zone. Main article: Tachocline. Main article: Convection zone. Main article: Photosphere. See also: Corona and Coronal loop.

See also: Solar irradiance. See also: Stellar magnetic field , Sunspots , List of solar cycles , and Solar phenomena. Butterfly diagram showing paired sunspot pattern. Graph is of sunspot area. Main articles: Formation and evolution of the Solar System and Stellar evolution. Main article: Corona. Main article: Faint young Sun paradox. See also: The Sun in culture. See also: Solar observatory. Play media. Main article: Solar System.

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