How do you measure the distance between planets? How the distance between the stars is measured

1. Measure the closer stars:

We can take the diameter of the Earth's orbit around the Sun as a baseline for a known distance. The time it takes for the Earth to orbit the Sun is one year, and half a circle in half a year. In the two days that were half a year apart, the Earth was exactly at opposite ends of the diameter of the Earth's orbit.

When the same star is observed in two days half a year apart, its direction is different, which is its parallax angle. The distance of the star can be calculated from the parallax angle and the diameter of the Earth's orbit (300 million kilometers). With this method, only the distance of stars within two to three hundred light-years can be measured.

2. Measure stars farther away:

Because the parallax angle of the stars farther away is too small to be accurate, other methods can only be found. One of the well-known methods is to use the circumference of Cepheid variables.

relationship to calculate the distance of distant celestial bodies, Cepheids thus obtained a "measuring scale."

The good name of the city. 3. Now, we can use radar to go from the Earth to the Moon.

and the emitted radio waves on Venus, and by calculating the time it takes for the radio waves to return to the ground, this distance can be measured very accurately.

The period of motion of the planets t and the semi-major axis a can be observed and determined. The only unknown quantity in the formula at the time was the gravitational constant g, and it was not until 1797 that Cavendish measured g using torsion, quickly determining the mass of the planets in the solar system with satellite systems and the mass of the Sun. Well, for stars outside the solar system, how to measure their mass brightness has puzzled astronomers for many years, until the discovery of spectral lines and blackbody spectra.

Let's start with the blackbody radiation when the two flowers bloom. It doesn't take a day or two for people to wonder how objects glow. For a long time, it was found that as the temperature rises, the iron in the iron furnace turns red first and then white.

Obviously, temperature is extremely important for luminescence, and based on this idea, Kirchhoff postulated an ideal condition – a black body: it can absorb all external light without any reflection or transmission. While a blackbody sounds ideal, many things in real life can be approximated as a blackbody, the largest of which are the trillions of stars overhead.

Kirchhoff, through simple thermodynamic calculations, pointed out that the ratio of radiant energy to absorbed energy of an object in thermal equilibrium has nothing to do with the physical properties of the object itself, but only with wavelength and temperature. According to Kirchhoff's law of radiation, at a certain temperature, a black body must be the object with the greatest radiation capacity, which can be called a complete radiator.

Kirchhoff's theorem is the first step in the long march, and the next task is to determine the radiation capacity of a black body at a certain temperature. Blackbody radiation is one of Sir Rayleigh's two famous dark clouds, and the details are no longer too deep. In short, Planck solved the problem theoretically in 1900 with experimental data.

Photon statistics can be used to quickly derive the law of blackbody radiation. With this, we can get the temperature of the surface of the sun by measuring the solar spectrum, and the temperature of the sun will certainly only depend on the amount of fuel in the sun, and ultimately on the mass. On the other hand, the brightness of the star is eventually reflected in the distance.

While these relationships are unclear at this time, there is finally something to be done.

It is mainly measured by sending radio waves. Because radio waves are reflected back when they come into contact with an obstacle, the distance of the planet can be determined based on the speed at which the radio waves travel.

Scientists use radar telemetry to make measurements, and they will also use some scientific and technological means to assist measurements, so that they can accurately measure the distance between the traveling stars.

Within the solar system, distances can be measured with radar or lasers. In addition, when Venus is on the other side of the Sun, the distance is measured with radar, and when Venus and the Earth are on the same side, the distance is measured by radar again. The average of the two times is the distance from the sun to the earth.

When measuring distances from other celestial bodies, the distance is calculated using the Sun-Earth distance and trigonometric functions.

Outside the solar system, the movement of distant stars on the background of the sky can be measured at a position where the Earth is on either side of the Sun, that is, half a year apart, and then the Earth's orbital radius can be used. But this method can only measure stars that are relatively close together. For distant objects, other methods can be used, such as when the star is far away from us, the Doppler effect will cause spectral redshift, and the distance can also be obtained by measuring the redshift.

For another example, there is a class of stars called Cepheids, which is characterized by the longer the light period, the smaller the absolute magnitude value, that is, by measuring its light period, its absolute magnitude can be obtained, and there is a distance-related function between visual magnitude and absolute magnitude, that is, its distance can be obtained by measuring the light period of Cepheid variables. This method is commonly used to measure the distances of extragalactic galaxies. Therefore, Cepheid variables have a nickname called "Measuring Ruler".

Introduction: There are many galaxies in the universe, for example, the earth is in the solar system, and the solar system is in the Milky Way, but in fact, there are many galaxies in the universe. So the distance between galaxies is also very important, so how do scientists measure the distance between galaxies?

In fact, in daily life, people can also measure the distance from one object to another, and the simpler way is when people are observing an object. When objects get smaller and smaller, they are getting farther and farther away from people. Or the same glowing object, as the distance from people gets farther and farther away, the brightness gets darker and darker, which is also a way of measurement.

The relationship between the distances of galaxies can be judged by observing the light of galaxies when they hit the Earth, and the light-year is also a unit of distance, so the distance between galaxies can be measured in this process. Of course, there is actually a Hubble telescope in outer space, and the Hubble telescope can observe very distant galaxies without any impurities and obstacles, and at this time, the distance between galaxies can be measured through the redshift phenomenon of light waves, which is also a good way. Others measure by the position of a fixed star, which allows them to measure the distance of the galaxy farther away.

In fact, the study of galaxies is of great significance to the earth and human beings. After all, there are many kinds of Milky Way, and there will always be a system similar to the Earth in the Milky Way, maybe there will be a habitable environment, after all, it is a matter of probability. In addition, the distance between galaxies can also be used to evaluate the size of the universe, so that the changes in the universe can be judged, so it is very meaningful to study these things.

There are times when people study the cosmic environment, and it also helps to improve their mood. You can also learn about it in your daily life, so as to better understand the environment of the earth in which people live.

Through arithmetic calculations, these scientists are very careful about the distance of galaxies and the things that matter about galaxies.

It is mainly judged according to the brightness of the period, the distance is relatively long, and it is calculated by Cepheid variables.

Scientists are able to make calculations based on the brightness of galaxies and are able to calculate them from Cepheid variables.

A closer star, the parallax method, and the eye to distinguish the distance, if you observe the whole earth as an eye, you can see far away.

Farther away, Cepheid variable star is the same as distinguishing the distance of a light bulb, it is darker farther and brighter closer, and the distance can be estimated.

No matter how far it goes, it is the redshift of the metering, and the wavelength of a beam of light can be judged by the absorption spectrum, and then the wavelength of the beam of light when it reaches the earth can be measured.