How scientists calculate the distance of galaxies from Earth

Cepheids are a class of stars that change their brightness periodically. American astronomers have discovered the change in the diameter of a Cepheid variable star by looking at the side, so that they can directly calculate its distance from the Earth. This will help to more accurately measure the distance of galaxies from Earth, thus "calibrating" the expansion rate.

Stars such as Cepheids have been observed to expand and contract as if they were taking a deep breath, producing light changes. Cepheids' luminous periods are related to their true brightness, so the brightness observed from Earth is correlated with their distance from Earth. If the exact distance between a Cepheid variable and the Earth is known, the apparent magnitude and absolute luminosity data of the other Cepheids can be used to calculate the distance of these variables, and thus determine the distance between the galaxy in which they are located and the Earth.

And galaxy distances are the basis for calculating the expansion rate of the universe. However, the closest Cepheid variable to Earth, Polaris, is also hundreds of light-years away from Earth, and it is difficult to measure its distance directly using the traditional parallax method. Scientists can only estimate the distance of the constellation containing Cepheid variables indirectly, and then infer the distance of other galaxies.

Scientists at the Palomar Observatory at the California Institute of Technology in the United States reported in the British journal Nature that they used the technique of "optical interferometry" to make two small telescopes play the fruit of one large telescope and directly observe the expansion and contraction of the Cepheid variable "Zeta Gemini". Zeta Gemini is one of the brightest Cepheid variable stars ever discovered, about 100 meters from Earth. Light-year.

Using its size change and brightness data, you can directly calculate the exact distance from the Earth. On this basis, scientists can more precisely calculate the distance from Earth from other galaxies containing Cepheid variables.

It is calculated according to the Pythagorean theorem.

First of all, you need to find two points and observe a galaxy or celestial object at the same time.

To make an observation, a sophisticated goniometer is used to measure the angle at which the object is observed at these two points.

Then, calculate the distance between these two points.

When we get the distance between the two angles and the two points, we can calculate the distance between the two points and the celestial body according to the Pythagorean theorem--- that is, knowing the length of one side and the two equal angles of the isosceles triangle, we can easily find the length of the two equal sides.

Of course, the prerequisite is that the angle and the length between two points can be accurately measured. In the past, when goniometers were not so sophisticated, some people used another exaggerated method, measuring the distance of celestial bodies in a year, that is, observing and sideways angles when the Earth's revolution was at the corresponding point.

Theoretically, the same astronomical telescope can calculate the distance of the celestial body after observing the celestial body every hour and calculating the displacement and observation angle caused by the earth's revolution and rotation.

When we talk about the distance between stars, it always feels particularly far, but how do we know how far away the star is? Calculate galaxies.

There are many ways to distance each other, and I will share three of them with you below.

1. ParallaxHave you ever noticed that when you look out the window of a moving vehicle, things near you will fly away, while things in the distance seem to move slowly? This is called the parallax effect. In the same way, the earth rotates on the ground.

, the position of stars close to Earth will always move from one place to another, while distant stars appear to be moving away from Earth. Using this filial piety principle, astronomers can more accurately calculate the distances between stars orbiting the Earth. Let's say there is a line called AB, which we call a baseline, and the longer the baseline, the farther the distance that can be measured.

Therefore, you can take a picture of the target planet and wait until a period of time to compare the difference between the galaxies in the two photos, and the angles connected by these different lines are parallax.

2. The standard candlelight method is based on magnitude.

m) Brightness (b) Luminosity (i) The concept can be seen:

Magnitude: Describes the brightness of the celestial body, absolute magnitude: the magnitude m at a distance of 10pc from the object;

Brightness: A unit of time on Earth.

the amount of radiation received by the celestial body in the area;

Luminosity: the total amount of radiation per unit time of a celestial body;

Relationship between them: m1-m2=

3. Spectral redshift method According to Hubble's law, the galaxy regression velocity v obtained by the redshift of the galaxy is proportional to the distance d of the galaxy.

It is concluded that v=h0 is the Hubble constant, and the regression velocity is related to the redshift z.

In short, the universe is vast and infinite, and it is wonderful and magnificent. iScientists.

I have been studying and measuring the distance between galaxies, to broaden our infinite knowledge, astronomy is really not something that ordinary brains can learn, these methods are also summarized, I hope it will be helpful to you, please criticize and correct.

You're very vast and very beautiful, so the distances of galaxies between the universes are measured in light years. Light-year search is a single key of length. It is used to calculate the distance of the stars.

The distance between each galaxy is measured by radar, and it is also estimated by some reflective elements.

It is very difficult to calculate by the Pythagorean theorem, and there may be some gaps in the calculated figures.

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.

It is calculated by a computer by receiving the electromagnetic waves emitted by these galaxies and the degree of attenuation.

It can be directly estimated and measured by a technology such as radar or a scatterer laser, and he can use triangulation, or a ruler to create a Cepheid, or a redshift.

It's all deduced and calculated by scientists through some of the data we currently have.

How is the distance between galaxies measured? What are the means? Let's take a look!

Looking out the window of a moving vehicle, have you ever noticed that something near you is flying away and something in the distance seems to be moving slowly? This is called the jet lag effect. Similarly, when the earth rotates.

, the position of stars approaching the Earth always moves from one place to another, and distant stars seem to be far away from the Earth. Using this principle, astronomers can more accurately calculate the distance between stars orbiting the Earth. For example, there is a line called ab, which we call the baseline.

The longer the baseline, the farther the measurable distance. Therefore, you can take a picture of the target planet, and after a while, you can take another one and compare the differences between the galaxies in the two photos. The corner where this different line joins together is jet lag.

When looking up at the sky, some stars look much brighter than him. Ancient Greece.

This was noticed by the astronomer Hippoclas, who, in 150 BC, worked to classify the stars by their brightness. This classification of stars according to the brightness of the earth's crust is called temporal magnitude. Today, in order to accommodate the vast amount of astronomical data we have, we have adjusted the scale of Hippoclas, creating a more complex scale.

At this scale, the lower the brightness of the star, the greater its gaze and so on. Some of the apparent magnitudes of stars observed by the Hubble telescope.

It can rise up to 30, and the Sun sees magnitude as.

Galaxies are far away from us, and the distance between galaxies is measured in light-years. off the Milky Way.

The two closest galaxies are the Large Magellanic Cloud and the Small Magellanic Cloud, which are about 170,000 light-years and 200,000 light-years from Earth, respectively. On a cosmic scale, they are at the entrance to the "home" of the Milky Way, the partner galaxies of the Milky Way. The Large Magellanic Cloud and the Small Magellanic Cloud were the first two extragalactic galaxies to be identified.

Trigonometric parallax: It is not easy to measure the distance between celestial bodies. Astronomers classify the objects to be measured into several grades based on the distance.

For objects closer to us, they are no more than 100 light-years away (1 light-year = ?). 1012 km). Astronomers measure their distances using trigonometric parallax.

The trigonometric parallax method is to place the measured object at the apex of a supertriangle. At the ends of the diameter of the Earth's orbit around the Sun are the other two vertices of the triangle. By measuring the angle of view from the Earth to that celestial body, and then measuring the known diameter of the Earth's orbit around the Sun, we can calculate the distance from that object to us based on a triangular formula.

For a distant object, we cannot measure its distance from the Earth using trigonometric parallax because their parallax is no longer accurate on Earth.

It can be measured by laser. The best way to do this is to use lasers, radars, field measurements, and light years, so that you can calculate the distances between galaxies.

Cursor. The distance between galaxies can be obtained through the calculation of two cursors, which is the most accurate and will better know the distance of galaxies.

Trigonometric parallax method.

Measuring the distance between celestial bodies is not an easy task. Astronomers classify the objects to be measured into several grades according to their distance. Astronomers measure the distance of celestial objects that are closer to us, no more than 100 light-years (1 light-year kilometer) away from us.

The trigonometric parallax method is to put the measured celestial body at the apex of a large triangle, and the two ends of the diameter of the Earth's orbit around the sun are the other two vertices of the triangle. A slightly farther celestial body cannot be measured by trigonometric parallax to measure its distance from the Earth, because it is no longer possible to accurately measure their parallax on Earth.

Moving star cluster method.

At this time, we need to measure the distance using the method of kinematics, which is also called the method of moving clusters in astronomy, and determines the distance according to their speed. However, kinematics must also be used to assume that all stars in a moving cluster are moving in the Milky Way at equal and parallel speeds. Celestial bodies beyond the Milky Way cannot be determined by kinematic methods to determine their distance from the Earth.

Cepheid parallax method (standard candle method).

There is a formula in physics about the relationship between luminosity, brightness, and distance. s∝l0/r2

The luminosity l0 and luminance s of the celestial object are measured, and then the distance r. of the celestial body is known using this formulaLuminosity and brightness have different meanings, brightness refers to how bright the luminous body we see is, which is something we can directly measure on Earth. Photometry refers to the ability of a luminous object to emit light, and the key is to try to know it to get the distance.

Astronomer LeWitt discovered "Cepheids" with a definite relationship between their luminous period and luminosity. The breadth can be determined by measuring its photoperiod, and then the distance can be found. If there is a Cepheid variable star in a galaxy outside the Milky Way, then we can know the distance between this galaxy and us.

For more distant galaxies that can't even be observed with or without Cepheids, of course, they have to find another way.

Trigonometric parallax and Cepheid parallax are the two most commonly used ranging methods, with the former measuring a few hundred light-years and the latter a few million light-years. In the middle zone, statistical and indirect methods are used. The largest measuring scale is the Hubble's Law method, which is on the order of 10 billion light-years.

Hubble's Law Method.

In 1929, Edwin Hubble studied the relationship between radial velocity and distance in extragalactic galaxies. At that time, only 46 extragalactic galaxies had radial velocities that could be used, and only 24 of them had calculated distances, and Hubble derived a roughly linear proportional relationship between radial velocity and distance. Modern accurate observations have confirmed this linear proportionality.

v = h0×d

where v is the receding velocity, d is the distance of the galaxy, h0 = 100h0km s-1mpc (the value of h0 is 0