Stars belong to the hottest objects of the Universe. It was the high temperature of our Sun that made this possible on Earth. But the reason for such strong heating of stars remained unknown to people for a long time.
Unraveling the secret high temperature the star lies inside it. This refers not only to the composition of the star - literally, the entire glow of the star comes from within. - this is the hot heart of the star, in which the thermonuclear fusion reaction occurs, the most powerful of nuclear reactions. This process is a source of energy for the entire star - heat from the center rises outward, and then into outer space.
Therefore, the temperature of a star varies greatly depending on where it is measured. For example, the temperature in the center of our core reaches 15 million degrees Celsius - and already on the surface, in the photosphere, the heat drops to 5 thousand degrees.
Why is the star's temperature so different?
The primary union of hydrogen atoms is the first step of the nuclear fusion process
Indeed, the differences in heating of the star's core and its surface are surprising. If all the energy of the Sun's core were distributed evenly throughout the star, the surface temperature of our star would be several million degrees Celsius! No less striking are the differences in temperature between stars of different spectral classes.
The thing is that the temperature of a star is determined by two main factors: the level of the core and the area of the emitting surface. Let's take a closer look at them.
Emission of energy from the nucleus
Although the core heats up to 15 million degrees, not all of this energy is transferred to neighboring layers. Only the heat produced by the thermonuclear reaction is emitted. The energy, despite its power, remains within the core. Accordingly, the temperature of the upper layers of a star is determined only by the strength of thermonuclear reactions in the core.
The differences here can be qualitative and quantitative. If the core is large enough, more hydrogen “burns” in it. This is how young and mature stars the size of the Sun, as well as blue giants and supergiants, receive energy. Massive stars like red giants burn not only hydrogen, but also helium, or even carbon and oxygen, in their nuclear furnace.
Fusion processes with the nuclei of heavy elements provide much more energy. In a thermonuclear fusion reaction, energy is obtained from the excess mass of the joining atoms. During the time that occurs inside the Sun, 6 hydrogen nuclei with an atomic mass of 1 combine into one helium nucleus with a mass of 4 - roughly speaking, 2 extra hydrogen nuclei are converted into energy. And when carbon “burns,” nuclei with a mass of already 12 collide - accordingly, the energy output is much greater.
Radiating surface area
However, stars not only generate energy, but also waste it. Consequently, the more energy a star gives off, the lower its temperature. And the amount of energy released primarily determines the area of the emitted surface.
The truth of this rule can be verified even in everyday life - laundry dries faster if it is hung wider on a line. And the surface of the star expands its core. The denser it is, the higher its temperature - and when a certain level is reached, hydrogen outside the stellar core is ignited from the incandescence.
On a clear night, if you look closely, you can see a myriad of colorful stars in the sky. Have you ever wondered what determines the shade of their flickering, and what colors of heavenly bodies are there?
The color of a star is determined by its surface temperature. A scattering of lights, as if gems, has infinitely varied shades, like an artist’s magical palette. The hotter the object, the higher the energy of radiation from its surface, which means the shorter the length of the emitted waves.
Even a slight difference in wavelength changes the color perceived by the human eye. The longest wavelengths have a red tint, with increasing temperature it changes to orange, yellow, turns into white, and then becomes white-blue.
The gas shell of the luminaries serves as an ideal emitter. Based on the color of a star, you can calculate its age and surface temperature. Of course, the shade is determined not “by eye”, but with the help of a special instrument - a spectrograph.
The study of the spectrum of stars is the foundation of astrophysics of our time. What colors the heavenly bodies are is most often the only information available to us about them.
Blue stars
Stars blue color- the most big and hot. The temperature of their outer layers averages 10,000 Kelvin, and can reach 40,000 for individual stellar giants.
New stars that are just beginning their “life journey” emit in this range. For example, Rigel, one of the two main luminaries of the Orion constellation, bluish-white.
Yellow stars
The center of our planetary system is Sun- has a surface temperature exceeding 6000 Kelvin. From space it and similar luminaries look dazzling white, although from Earth they appear rather yellow. Gold stars are middle aged.
Of the other luminaries known to us, the white star is Sirius, although its color is quite difficult to determine by eye. This happens because it occupies a low position above the horizon, and on its way to us its radiation is greatly distorted due to multiple refraction. In mid-latitudes, Sirius, flickering frequently, is capable of demonstrating the entire color spectrum in just half a second!
Red stars
Stars with low temperatures have a dark reddish tint., for example, red dwarfs, whose mass is less than 7.5% of the mass of the Sun. Their temperature is below 3500 Kelvin, and although their glow is a rich shimmer of many colors and shades, we see it as red.
Giant stars that have run out of hydrogen fuel also appear red or even brown. In general, the emission of old and cooling stars lies in this range of the spectrum.
The second of the main stars of the constellation Orion has a distinct red tint, Betelgeuse, and a little to the right and above it is located on the sky map Aldebaran, having an orange color.
The oldest red star in existence - HE 1523-0901 from the constellation Libra - a giant second-generation luminary, found on the outskirts of our galaxy at a distance of 7500 light years from the Sun. Its possible age is about 13.2 billion years, which is not much less than the estimated age of the Universe.
Stars of different colors
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 colors 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 into 250,000 equal parts (1 inch equals 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 of 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.
Related materials:
Flame color
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.
The sun is a yellow star. The temperature on its surface is 5,500 degrees Celsius. The temperature on the surface of the hottest blue star exceeds 33,000 degrees.
Physical laws of color and temperature
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. Blue color has a shorter wavelength than red. Therefore, if a body emits blue wavelengths, then it is hotter than a body emitting red light. Atoms of hot gases in stars emit particles called photons. The hotter the gas, the higher the energy of the photons and the shorter their wavelength.
what colors are cold and hot stars and got the best answer
Answer from DOKER-L[guru]
COLOR AND TEMPERATURE OF STARS
Temperature and color of stars
Source: All about the stars:
Answer from 2 answers[guru]
Hello! Here is a selection of topics with answers to your question: what color are cold and hot stars?
Answer from Roman Maryashin[newbie]
Answer from Alex Vlasov[newbie]
white and blue
Answer from Vladimir buhvestov[expert]
The stars are always cold in the sky
Answer from Artem Kereev[newbie]
cold-blue, hot-red
Answer from mm mm[newbie]
The hottest stars are always blue and white, less hot - yellowish, cold - reddish. But even the coldest stars have a temperature of 2-3 thousand Kelvin - hotter than any molten metal.
Answer from Morfix_Game-Channel[newbie]
DOKER-L Enlightened (37832) 5 years ago
COLOR AND TEMPERATURE OF STARS
One of the easily measured characteristics of stars is color. Just as hot metal changes its color depending on the degree of heating, so the color of a star always indicates its temperature. In astronomy, an absolute temperature scale is used, the step of which is one kelvin (1 K) - the same as in the familiar Celsius scale (1 ° C), and the beginning of the scale is shifted by -273 (0 K = - 273 ° C).
Temperature and color of stars
The hottest stars are always blue and white, less hot ones are yellowish, and cooler ones are reddish. But even the coldest stars have a temperature of 2-3 thousand Kelvin - hotter than any molten metal.
The human eye can only roughly determine the color of a star. For more accurate estimates, photographic and photoelectric radiation detectors are used, sensitive to different parts of the visible (or invisible) spectrum. After all, the color of a star depends on which part of the spectrum contains the greatest radiation energy. Comparing stellar magnitudes in different spectral intervals (for example, in blue and yellow) makes it possible to quantitatively characterize the color of a star and estimate its temperature.
Answer from Liliya Bashlaeva[newbie]
red
Answer from Lyubov Botalova[newbie]
why bother with just red?
Answer from Danila Pro-Sto[newbie]
COLOR AND TEMPERATURE OF STARS
One of the easily measured characteristics of stars is color. Just as hot metal changes its color depending on the degree of heating, so the color of a star always indicates its temperature. In astronomy, an absolute temperature scale is used, the step of which is one kelvin (1 K) - the same as in the familiar Celsius scale (1 ° C), and the beginning of the scale is shifted by -273 (0 K = - 273 ° C).
Temperature and color of stars
The hottest stars are always blue and white, less hot ones are yellowish, and cooler ones are reddish. But even the coldest stars have a temperature of 2-3 thousand Kelvin - hotter than any molten metal.
The human eye can only roughly determine the color of a star. For more accurate estimates, photographic and photoelectric radiation detectors are used, sensitive to different parts of the visible (or invisible) spectrum. After all, the color of a star depends on which part of the spectrum contains the greatest radiation energy. Comparing stellar magnitudes in different spectral intervals (for example, in blue and yellow) makes it possible to quantitatively characterize the color of a star and estimate its temperature.
In quantities. By general agreement, these scales are chosen so that a white star, such as Sirius, has the same magnitude on both scales. The difference between the photographic and photovisual magnitudes is called the color index of a given star. For blue stars like Rigel, this number will be negative, since such stars on a regular plate show more blackening than on a yellow-sensitive plate.
For red stars like Betelgeuse, the color index reaches +2-3 magnitudes. This color measurement is also a measurement of the surface temperature of the star, with blue stars being significantly hotter than red ones.
Since color indices can be obtained quite easily even for very faint stars, they are of great importance in studying the distribution of stars in space.
The most important tools for studying stars include instruments. Even the most superficial glance at the spectra of stars reveals that they are not all the same. The Balmer lines of hydrogen are strong in some spectra, weak in some, and completely absent in others.
It soon became clear that the spectra of stars could be divided into a small number of classes, gradually transforming into each other. Currently used spectral classification was developed at the Harvard Observatory under the leadership of E. Pickering.
At first, spectral classes were designated in Latin letters in alphabetical order, but in the process of clarifying the classification, the following designations were established for successive classes: O, B, A, F, G, K, M. In addition, a few unusual stars are combined into classes R, N and S , and certain individuals who do not fit into this classification at all are designated by the symbol PEC (peculiar - special).
It is interesting to note that the arrangement of stars by class is also the arrangement by color.
- Class B stars, which include Rigel and many other stars in Orion, are blue;
- classes O and A - white (Sirius, Deneb);
- classes F and G - yellow (Procyon, Capella);
- classes K and M, - orange and red (Arcturus, Aldebaran, Antares, Betelgeuse).
Arranging the spectra in the same order, we see how the maximum radiation intensity shifts from the violet to the red end of the spectrum. This indicates a decrease in temperature as one moves from class O to class M. A star's place in the sequence is determined more by its surface temperature than by its chemical composition. It is generally accepted that the chemical composition is the same for the vast majority of stars, but different surface temperatures and pressures cause large differences in stellar spectra.
Blue class O stars are the hottest. Their surface temperature reaches 100,000°C. Their spectra can be easily recognized by the presence of some characteristic bright lines or by the spread of the background far into the ultraviolet region.
They are immediately followed blue class B stars, also very hot (surface temperature 25,000°C). Their spectra contain lines of helium and hydrogen. The former weaken, and the latter strengthen during the transition to class A.
IN classes F and G(a typical G-class star is our Sun), the lines of calcium and other metals, such as iron and magnesium, gradually become stronger.
IN class K The calcium lines are very strong, and molecular bands also appear.
Class M includes red stars with surface temperatures less than 3000°C; bands of titanium oxide are visible in their spectra.
Classes R, N and S belong to the parallel branch of cool stars, in the spectra of which other molecular components are present.
For a connoisseur, however, there is a very big difference between “cold” and “hot” class B stars. In a precise classification system, each class is further divided into several subclasses. The hottest class B stars are subclass VO, stars with an average temperature for a given class - k subclass B5, the coldest stars - to subclass B9. The stars follow directly behind them. subclass AO.
Studying the spectra of stars turns out to be very useful, since it makes it possible to roughly classify stars according to their absolute magnitudes. For example, the star VZ is a giant with an absolute magnitude approximately equal to - 2.5. It is possible, however, that the star will turn out to be ten times brighter (absolute magnitude - 5.0) or ten times fainter (absolute magnitude 0.0), since it is impossible to give a more accurate estimate based on spectral type alone.
When establishing a classification of stellar spectra, it is very important to try to separate giants from dwarfs within each spectral class, or, where this division does not exist, to isolate from the normal sequence of giants stars that have too much or too little luminosity.
