Stars different color
Our Sun is a pale yellow star. In general, the color of stars is an amazingly diverse palette of colors. One of the constellations is called “Jewelry Box”. Sapphire and blue stars are scattered across the black velvet of the night sky. Between them, in the middle of the constellation, is a bright orange star.
Differences in star color
Differences in the color of stars are explained by the fact that stars have different temperatures. This is why this happens. Light is wave radiation. The distance between the crests of one wave is called its length. The waves of light are very short. How much? Try dividing an inch by 250000 equal parts(1 inch is equal to 2.54 centimeters). Several such parts will make up the wavelength of light.
Despite such an insignificant wavelength of light, the slightest difference between the sizes of light waves dramatically changes the color of the picture we observe. This comes from the fact that light waves different lengths are perceived by us as different colors. For example, the wavelength of red is one and a half times longer than the wavelength of blue. White color is a ray consisting of photons of light waves of different lengths, that is, rays of different colors.
From everyday experience we know that the color of bodies depends on their temperature. Place an iron poker on the fire. As it heats up, it first turns red. Then she will blush even more. If the poker could be heated even more without melting it, it would turn from red to orange, then yellow, then white, and finally blue-white.
what color are the stars? and why?
- Stars come in all colors of the rainbow. Because they have different temperatures and composition.
http://www.pockocmoc.ru/color.php- Stars come in a variety of colors. Arcturus has a yellow-orange tint, Rigel is white-blue, Antares is bright red. The dominant color in a star's spectrum depends on its surface temperature. The gas shell of a star behaves almost like an ideal emitter (absolutely black body) and is completely subject to the classical laws of radiation by M. Planck (1858-1947), J. Stefan (1835-1893) and W. Wien (1864-1928), connecting the temperature of the body and the nature of its radiation. Planck's law describes the distribution of energy in the spectrum of a body. He points out that with increasing temperature, the total radiation flux increases, and the maximum in the spectrum shifts towards shorter waves. The wavelength (in centimeters) at which the maximum radiation occurs is determined by Wien's law: lmax = 0.29/T. It is this law that explains the red color of Antares (T = 3500 K) and the bluish color of Rigel (T = 18000 K).
HARVARD SPECTRAL CLASSIFICATION
Spectral class Effective temperature, KColor
O———————————————2600035000 ——————Blue
B ———————————————1200025000 ———-White-blue
A ————————————————800011000 ———————White
F ————————————————-62007900 ———-Yellow-white
G ————————————————50006100 ——————-Yellow
K ————————————————-35004900 ————-Orange
M ————————————————26003400 ——————Red - Our sun is a pale yellow star. In general, stars have a wide variety of colors and shades. The differences in the colors of stars are due to the fact that they have different temperatures. And that's why this happens. Light, as is known, is wave radiation, the wavelength of which is very short. If we change the length of this light even slightly, the color of the picture we see will change dramatically. For example, the wavelength of red light is one and a half times longer than the wavelength of blue light.
Cluster of colorful stars
Scientists have formulated physical laws that relate color and temperature. The hotter the body, the greater the radiation energy from its surface and the shorter the length of the emitted waves. Therefore, if a body emits blue wavelengths, then it is hotter than a body emitting red.
Atoms of hot gases in stars emit photons. The hotter the gas, the higher the energy of the photons and the shorter their wavelength. Therefore, the hottest new stars emit in the blue-white range. As stars use up their nuclear fuel, they cool down. Therefore, old, cooling stars emit in the red range of the spectrum. Middle-aged stars, such as the Sun, emit in the yellow range.
Our Sun is relatively close to us, and therefore we clearly see its color. Other stars are so far away from us that even with the help of powerful telescopes we cannot say with certainty what color they are. To clarify this issue, scientists use a spectrograph, an instrument for identifying the spectral composition of starlight. - It depends on the temperature. The hottest colors are white and blue, the coldest are red, but even then they have a temperature higher than any molten metal.
- Is the sun white?
- The perception of color is purely subjective, it depends on the reaction of the observer's retina.
- in the sky? I know that there are blue, and yellow, and white. here is our Sun - a yellow dwarf)))
- Stars come in different colors. Blue ones have a higher temperature than red ones and greater radiation energy from its surface. They also come in white, yellow and orange, and almost all are made of hydrogen.
- Stars come in a variety of colors, almost all the colors of the rainbow (for example: our Sun is yellow, Rigel is white-blue, Antares is red, etc.)
The differences in the colors of stars are due to the fact that they have different temperatures. And that's why this happens. Light, as is known, is wave radiation, the wavelength of which is very short. If we change the length of this light even slightly, the color of the picture we see will change dramatically. For example, the wavelength of red light is one and a half times longer than the wavelength of blue light.
As you know, when the temperature increases, a heated metal first begins to glow red, then yellow and, finally, white. The stars shine in a similar way. Reds are the coldest, and whites (or even blues!) are the hottest. A newly flared star will have a color corresponding to the energy released in its core, and the intensity of this release, in turn, depends on the mass of the star. Consequently, all normal stars are cooler the more red they are, so to speak. “Heavy” stars are hot and white, while “light”, non-massive stars are red and relatively cool. We have already named the temperatures of the hottest and coldest stars (see above). We now know that the highest temperatures correspond to blue stars, the lowest to red ones. Let us clarify that in this paragraph we were talking about the temperatures of the visible surfaces of stars, because in the center of stars (in their cores) the temperature is much higher, but it is also highest in massive blue stars.
The spectrum of a star and its temperature are closely related to the color index, i.e., to the ratio of the brightness of the star in the yellow and blue ranges of the spectrum. Planck's law, which describes the distribution of energy in the spectrum, gives an expression for the color index: C.I. = 7200/T 0.64. Cool stars have a higher color index than hot stars, that is, cool stars are relatively brighter in yellow rays than in blue ones. Hot (blue) stars appear brighter on ordinary photographic plates, while cool stars appear brighter to the eye and special photographic emulsions that are sensitive to yellow rays.
Scientists have formulated physical laws that relate color and temperature. The hotter the body, the greater the radiation energy from its surface and the shorter the length of the emitted waves. Therefore, if a body emits blue wavelengths, then it is hotter than a body emitting red.
Atoms of hot gases in stars emit photons. The hotter the gas, the higher the energy of the photons and the shorter their wavelength. Therefore, the hottest new stars emit in the blue-white range. As stars use up their nuclear fuel, they cool down. Therefore, old, cooling stars emit in the red range of the spectrum. Middle-aged stars, such as the Sun, emit in the yellow range.
Our Sun is relatively close to us, and therefore we clearly see its color. Other stars are so far away from us that even with the help of powerful telescopes we cannot say with certainty what color they are. To clarify this issue, scientists use a spectrograph, an instrument for identifying the spectral composition of starlight.
HARVARD SPECTRAL CLASSIFICATION gives a dependence on the temperature of the star's color, for example: 35004900 - orange, 800011000 white, 2600035000 blue, etc. http://www.pockocmoc.ru/color.phpAnd another important fact: the dependence of the color of a star’s glow on its mass.
More massive normal stars have higher surface and core temperatures. They burn their nuclear fuel faster - hydrogen, which basically makes up almost all stars. Which of two normal stars is more massive can be judged by its color: blue ones are heavier than white ones, white ones are heavier than yellow ones, yellow ones are heavier than orange ones, orange ones are heavier than red ones.
Everyone knows the three physical states of matter - solid, liquid and gaseous.. What happens to a substance when successively heated to high temperatures in a closed volume? - Consecutive transition from one state of aggregation to another: solid- liquid - gas(due to an increase in the speed of movement of molecules with increasing temperature). With further heating of the gas at temperatures above 1,200 ºС, the disintegration of gas molecules into atoms begins, and at temperatures above 10,000 ºС - partial or complete disintegration of gas atoms into their components elementary particles- electrons and atomic nuclei. Plasma is the fourth state of matter in which the molecules or atoms of a substance are partially or completely destroyed under the influence of high temperatures or for other reasons. 99.9% of the matter in the Universe is in the plasma state.
Stars are a class of cosmic bodies with a mass of 10 26 -10 29 kg.
A star is a hot plasma spherical cosmic body, which is, as a rule, in hydrodynamic and thermodynamic equilibrium.
If the equilibrium is disturbed, the star begins to pulsate (its size, luminosity and temperature change). The star becomes a variable star.
Variable star is a star whose brightness (visible brightness in the sky) changes over time. The reasons for variability may be physical processes in the bowels of a star. Such stars are called physical variables(for example, δ Cephei. Variable stars similar to it began to be called Cepheids).
Meet and eclipsing variables stars whose variability is caused by mutual eclipses of their components(for example, β Persei - Algol. Its variability was first discovered in 1669 by the Italian economist and astronomer Geminiano Montanari).
Eclipsing variable stars are always double, those. consist of two closely spaced stars. Variable stars on star maps are indicated by a circle:
Stars are not always balls. If a star rotates very quickly, then its shape is not spherical. The star contracts from the poles and becomes like a tangerine or pumpkin (for example, Vega, Regulus). If the star is double, then the mutual attraction of these stars to each other also affects their shape. They become ovoid or melon-shaped (for example, components of the double star β Lyrae or Spica):
Stars are the main inhabitants of our Galaxy (our Galaxy is written with a capital letter). There are about 200 billion stars in it. With the help of even the largest telescopes, only half a percent of the total number of stars in the Galaxy can be seen. More than 95% of all matter observed in nature is concentrated in stars. The remaining 5% consists of interstellar gas, dust and all non-self-luminous bodies.
Apart from the Sun, all the stars are so far from us that even in the largest telescopes they are observed in the form of luminous points of different colors and brilliance. The closest system to the Sun is the α Centauri system, consisting of three stars. One of them, a red dwarf called Proxima, is the closest star. Before her 4.2 light years. To Sirius - 8.6 sv. years, to Altair - 17 St. years. To Vega - 26 St. years. To the North Star - 830 sv. years. To Deneb - 1,500 sv. years. For the first time in 1837, V.Ya. was able to determine the distance to another star (it was Vega). Struve.
The first star for which it was possible to obtain an image of the disk (and even some spots on it) is Betelgeuse (α Orionis). But this is because Betelgeuse is 500-800 times larger in diameter than the Sun (the star is pulsating). An image of Altair's disk (α Aquila) was also obtained, but this is because Altair is one of the closest stars.
The color of stars depends on the temperature of their outer layers. Temperature range - from 2,000 to 60,000 °C. The coolest stars are red, and the hottest are blue. By the color of a star you can judge how hot its outer layers are.
Examples of red stars: Antares (α Scorpii) and Betelgeuse (α Orionis).
Examples of orange stars: Aldebaran (α Tauri),
Arcturus (α Bootes)
and Pollux (β Gemini).
Examples of yellow stars: the Sun, Capella (α Auriga) and Toliman (α Centauri).
Examples of yellowish-white stars: Procyon (α Canis Minor) and Canopus (α Carinae).
Examples of white stars: Sirius (α Canis Major), Vega (α Lyra), Altair (α Eagle) and Deneb (α Cygnus).
Examples of bluish stars: Regulus (α Leo) and Spica (α Virgo).
Due to the fact that very little light comes from the stars, the human eye is able to distinguish color shades only from the brightest of them. With binoculars and even more so with a telescope (they capture more light than the eye), the color of the stars becomes more noticeable.
Temperature increases with depth. Even the coldest stars have temperatures reaching millions of degrees at their centers. The Sun has about 15,000,000 °C at its center (the Kelvin scale is also used - a scale of absolute temperatures, but when we are talking about very high temperatures, the difference of 273 º between the Kelvin and Celsius scales can be neglected).
What heats up the stellar interior so much? It turns out that there are happening thermonuclear processes, as a result of which a huge amount of energy is released. Translated from Greek, “thermos” means warm. The main chemical element that stars are made of is hydrogen. It is this that is the fuel for thermonuclear processes. In these processes, the nuclei of hydrogen atoms are converted into the nuclei of helium atoms, which is accompanied by the release of energy. The number of hydrogen nuclei in the star decreases, and the number of helium nuclei increases. Over time, others are synthesized in the star. chemical elements. All the chemical elements that make up molecules various substances, were once born in the depths of the stars.“The stars are the past of man, and man is the future of the star,” as they sometimes say figuratively.
The process of a star emitting energy in the form electromagnetic waves and the particles are called radiation. Stars emit energy not only in the form of light and heat, but also other types of radiation - gamma rays, X-rays, ultraviolet, radio radiation. In addition, stars emit streams of neutral and charged particles. These streams form the stellar wind. Stellar wind is the process of outflow of matter from stars into outer space. As a result, the mass of stars is constantly and gradually decreasing. It is the stellar wind from the Sun (solar wind) that leads to the appearance of auroras on Earth and other planets. It is the solar wind that deflects the tails of comets in the direction opposite to the Sun.
Stars, of course, do not appear from the void (the space between stars is not an absolute vacuum). The materials are gas and dust. They are distributed unevenly in space, forming shapeless clouds of very low density and enormous extent - from one or two to tens of light years. Such clouds are called diffuse gas-dust nebulae. The temperature in them is very low - about -250 °C. But not every gas-dust nebula produces stars. Some nebulae may for a long time exist without stars. What conditions are necessary for the process of star birth to begin? The first is the mass of the cloud. If there is not enough matter, then, of course, the star will not appear. Second, compactness. If the cloud is too extended and loose, the processes of its compression cannot begin. Well, and thirdly, a seed is needed - i.e. a clot of dust and gas, which will later become the embryo of a star - a protostar. Protostar- this is a star at the final stage of its formation. If these conditions are met, then gravitational compression and heating of the cloud begins. This process ends star formation- the appearance of new stars. This process takes millions of years. Astronomers have found nebulae in which the process of star formation is in full swing - some stars have already lit up, some are in the form of embryos - protostars, and the nebula is still preserved. An example is the Great Orion Nebula.
The main physical characteristics of a star are luminosity, mass and radius(or diameter), which are determined from observations. Knowing them as well chemical composition star (which is determined by its spectrum), one can calculate the model of the star, i.e. physical conditions in its depths, to explore the processes that occur in it.Let us dwell in more detail on the main characteristics of stars.
Weight. The mass can be directly estimated only by the gravitational effect of the star on surrounding bodies. The mass of the Sun, for example, was determined from the known periods of revolution of the planets around it. Planets are not directly observed in other stars. Reliable measurement mass is possible only in double stars (in this case, Kepler’s law generalized by Newton III is used, nand then the error is 20-60%). About half of all the stars in our Galaxy are double. Stellar masses range from ≈0.08 to ≈100 solar masses.There are no stars with a mass less than 0.08 solar masses; they simply do not become stars, but remain dark bodies.Stars with a mass greater than 100 solar masses are extremely rare. Most of stars have masses less than 5 solar masses. The fate of a star depends on its mass, i.e. the scenario according to which the star develops and evolves. Small, cold red dwarfs use hydrogen very sparingly and therefore their lives last hundreds of billions of years. The lifespan of the Sun, a yellow dwarf, is about 10 billion years (the Sun has already lived about half of its life). Massive supergiants consume hydrogen quickly and fade away within a few million years after their birth. The more massive the star, the shorter its life path.
The age of the Universe is estimated at 13.7 billion years. Therefore, stars older than 13.7 billion years old do not yet exist.
- Stars with mass 0,08 solar masses are brown dwarfs; their fate is constant compression and cooling with the cessation of all thermonuclear reactions and transformation into dark planet-like bodies.
- Stars with mass 0,08-0,5
The masses of the Sun (these are always red dwarfs) after using up hydrogen begin to slowly compress, while heating up and becoming a white dwarf.
- Stars with mass 0,5-8
masses of the Sun at the end of their lives turn first into red giants and then into white dwarfs. The outer layers of the star are scattered in outer space in the form planetary nebula. A planetary nebula is often spherical or ring-shaped.
- Stars with mass 8-10 solar masses can explode at the end of their lives, or they can age quietly, first turning into red supergiants and then into red dwarfs.
- Stars with a mass greater than 10
mass of the Sun at the end life path first become red supergiants, then explode as supernovae (a supernova is not a new star, but an old star) and then turn into neutron stars or become black holes.
Black holes- these are not holes in outer space, but objects (remnants of massive stars) with very high mass and density. Black holes have neither supernatural nor magical powers, and are not “monsters of the Universe.” They just have so much strength gravitational field that no radiation (neither visible - light, nor invisible) can leave them. That's why black holes are invisible. However, they can be detected by their effect on surrounding stars and nebulae. Black holes are a completely common phenomenon in the Universe and there is no need to be afraid of them. There may be a supermassive black hole at the center of our Galaxy.
Radius (or diameter). The sizes of stars vary widely - from several kilometers (neutron stars) to 2,000 times the diameter of the Sun (supergiants). As a rule, the smaller the star, the higher its average density. In neutron stars, the density reaches 10 13 g/cm 3! A thimble of such a substance would weigh 10 million tons on Earth. But supergiants have a density less than the density of air at the surface of the Earth.
The diameters of some stars compared to the Sun:
Sirius and Altair are 1.7 times larger,
Vega is 2.5 times larger,
Regulus is 3.5 times greater,
Arcturus is 26 times larger
Polar is 30 times larger,
The crossbar is 70 times larger,
Deneb is 200 times larger,
Antares is 800 times larger,
YV Canis Majoris is 2,000 times larger (the largest star known).
Luminosity is total energy, emitted by an object (in this case stars) per unit time. The luminosity of stars is usually compared with the luminosity of the Sun (the luminosity of stars is expressed through the luminosity of the Sun). Sirius, for example, emits 22 times more energy than the Sun (the luminosity of Sirius is equal to 22 Suns). The luminosity of Vega is 50 Suns, and the luminosity of Deneb is 54,000 Suns (Deneb is one of the most powerful stars).
The apparent brightness (more correctly, brightness) of a star in the earth’s sky depends on:
- distance to the star. If a star approaches us, its apparent brightness will gradually increase. And vice versa, as a star moves away from us, its apparent brightness will gradually decrease. If you take two identical stars, the one closer to us will appear brighter.
- on the temperature of the outer layers. The hotter a star is, the more light energy it sends into space, and the brighter it will appear. If a star cools down, then its apparent brightness in the sky will decrease. Two stars of the same size and at the same distances from us will appear the same in apparent brightness, provided that they emit the same amount of light energy, i.e. have the same temperature of the outer layers. If one of the stars is cooler than the other, then it will appear less bright.
- on size (diameter). If you take two stars with the same temperature of the outer layers (the same color) and place them at the same distance from us, the larger star will emit more light energy, and therefore will appear brighter in the sky.
- from the absorption of light by clouds of cosmic dust and gas located in the path of the line of sight. The thicker the layer of cosmic dust, the more light from the star it absorbs, and the dimmer the star appears. If we take two identical stars and place a gas-dust nebula in front of one of them, then this star will appear less bright.
- from the height of the star above the horizon. There is always a dense haze near the horizon, which absorbs some of the light from the stars. Near the horizon (shortly after sunrise or just before sunset), stars always appear dimmer than when they are overhead.
It is very important not to confuse the concepts of “appear” and “be”.
A star can be very bright in itself, but seem dim due to various reasons: due to the large distance to it, due to its small size, due to the absorption of its light by cosmic dust or dust in the Earth's atmosphere. Therefore, when talking about the brightness of a star in the earth’s sky, they use the phrase "apparent brightness" or "brilliance".
As already mentioned, double stars exist. But there are also triple (for example, α Centauri), and quadruple (for example, ε Lyra), and five, and six (for example, Castor), etc. Individual stars in star system called components. Stars with more than two components are called multiples stars. All components of a multiple star are connected by mutual gravitational forces (they form a system of stars) and move along complex trajectories.
If there are many components, then this is no longer a multiple star, but star cluster. Distinguish ball And scattered star clusters. Globular clusters contain many old stars and are older than open clusters, which contain many young stars. Globular clusters are quite stable, because... the stars in them are at small distances from each other and the forces of mutual attraction between them are much greater than between the stars of open clusters. Open clusters disperse further over time.
Open clusters are correctly located on the strip Milky Way or nearby. On the contrary, globular clusters are located on starry sky away from the Milky Way.
Some star clusters can be seen in the sky even with the naked eye. For example, the open clusters Hyades and Pleiades (M 45) in Taurus, the open cluster Manger (M 44) in Cancer, the globular cluster M 13 in Hercules. Quite a lot of them are visible through binoculars.