1 light year in meters. What is a light year equal to? What is a light year equal to?

The distances between stars are so great that measuring them in kilometers or miles is an exercise with endless zeros. The usual measurement system is used to designate distances in one system. For example, they say that the minimum distance from Earth to Mars is 55.76 million kilometers. With stars, everything is more complicated, and here the concepts of light year and parsec are usually used.

Astronomical unit- a unit of measurement adopted in astronomy for objects of the Solar System and the objects of the Universe closest to it. An astronomical unit is equal to 149,598,100 km (+- ~750 km), which is approximately equal to the average distance of the Earth from the Sun. Modern observations have recorded a gradual increase in value by 15 cm annually, which is explained by the possible loss of mass by the Sun, the consequences of the solar wind.

Light year- the distance that light travels in one year, in meters it is 9,460,730,472,580,800. In fact, the light of the stars that we see on a cloudless night traveled to our planet for many centuries, and some of them no longer exist at all.

Parsec, also known as “arcsecond parallax,” is the distance from which the average radius of the Earth’s orbit (perpendicular to the line of sight) is visible at an angle of one arcsecond. Quite simply, a parsec = 3.26 light years.

It is interesting that in popular science and fantasy literature it is customary to use the concept of a light year, and parsecs are usually used only in professional works and research.

(Galaxy UDFj-39546284 is the farthest galaxy from Earth (13.3 billion light years from Earth), in the image taken by the Hubble telescope it looks like a red dot)

The closest star to us is Alpha Centauri, which is located 4.37 light years from Earth. But the most distant galaxy (as of December 2012) is as much as 13.3 billion light years from Earth! It turns out that when the sun of this very galaxy (known under the symbol UDFj-39546284) goes out, humanity will not know about it soon.

An extra-system unit of length used in astronomy; 1 S.g. is equal to the distance traveled by light in 1 year. 1 S. g. = 0.3068 parsec = 9.4605 1015 m. Physical encyclopedic dictionary. M.: Soviet Encyclopedia. Editor-in-Chief A. M. Prokhorov... ... Physical encyclopedia

LIGHT YEAR, a unit of astronomical distance equal to the distance that light travels in outer space or in a VACUUM in one tropical year. One light year is equal to 9.46071012 km... Scientific and technical encyclopedic dictionary

LIGHT YEAR, a unit of length used in astronomy: the path traveled by light in 1 year, i.e. 9.466?1012 km. The distance to the nearest star (Proxima Centauri) is approximately 4.3 light years. The most distant stars in the Galaxy are located on... ... Modern encyclopedia

Unit of interstellar distances; the path that light travels in a year, i.e. 9.46? 1012 km... Big Encyclopedic Dictionary

Light year- LIGHT YEAR, a unit of length used in astronomy: the path traveled by light in 1 year, i.e. 9.466´1012 km. The distance to the nearest star (Proxima Centauri) is approximately 4.3 light years. The most distant stars in the Galaxy are located on... ... Illustrated Encyclopedic Dictionary

An extra-system unit of length used in astronomy. 1 light year is the distance that light travels in 1 year. 1 light year is equal to 9.4605E+12 km = 0.307 pc... Astronomical Dictionary

Unit of interstellar distances; the path that light travels in a year, that is, 9.46·1012 km. * * * LIGHT YEAR LIGHT YEAR, a unit of interstellar distances; the path that light travels in a year, i.e. 9.46×1012 km... encyclopedic Dictionary

Light year- a unit of distance equal to the path traveled by light in one year. A light year is equal to 0.3 parsecs... Concepts of modern natural science. Glossary of basic terms

light year- šviesmetis statusas T sritis Standartizacija ir metrologija apibrėžtis Astronominis ilgio matavimo vienetas, lygus nuotoliui, kurį vakuume nusklinda šviesa per 1 atogrąžinius metus. Žymimas šm: 1 šm = 9.46073 · 10¹² km. atitikmenys: engl. light... ... Penkiakalbis aiškinamasis metrologijos terminų žodynas

light year- šviesmetis statusas T sritis fizika atitikmenys: engl. light year vok. Lichtjahr, n rus. light year, m pranc. année lumière, f … Fizikos terminų žodynas

Books

There is no turning back. Set of 3 books, Alexey Lukyanov, Ivan Sergeevich Naumov. Set of 3 books. 1. "Tsunami. Book one. Earthshakers" 1999. Egor and Yusya Kruglov are left without adult care. Nothing good awaits them ahead. Disability has turned...
Fascinating astronomy, Elena Kachur. About the book In the new and long-awaited book, Chevostik and Uncle Kuzya go to the observatory! Here they will have a fascinating acquaintance with the celestial bodies that decorate our night sky. Together with…

Surely, having heard in some science fiction action movie an expression a la “twenty to Tatooine light years", many asked legitimate questions. I'll mention some of them:

Isn't a year a time?

Then what is it light year?

How many kilometers is it?

How long will it take to overcome light year spaceship with Earth?

I decided to devote today’s article to explaining the meaning of this unit of measurement, comparing it with our usual kilometers and demonstrating the scale that it operates Universe.

Virtual racer.

Let's imagine a person, in violation of all the rules, rushing along a highway at a speed of 250 km/h. In two hours it will cover 500 km, and in four – as much as 1000. Unless, of course, it crashes in the process...

It would seem that this is speed! But in order to circumnavigate the entire globe (≈ 40,000 km), our racer will need 40 times more time. And this is already 4 x 40 = 160 hours. Or almost a whole week of continuous driving!

In the end, however, we will not say that he covered 40,000,000 meters. Because laziness has always forced us to invent and use shorter alternative units of measurement.

Limit.

From a school physics course, everyone should know that the fastest rider in Universe- light. In one second, its beam covers a distance of approximately 300,000 km, and thus it will circle the globe in 0.134 seconds. That's 4,298,507 times faster than our virtual racer!

From Earth before Moon the light reaches on average 1.25 s, up to Sun its beam will reach in a little more than 8 minutes.

Colossal, isn't it? But the existence of speeds greater than the speed of light has not yet been proven. Therefore, the scientific world decided that it would be logical to measure cosmic scales in units that a radio wave (which light, in particular, is) travels over certain time intervals.

Distances.

Thus, light year- nothing more than the distance that a ray of light travels in one year. On interstellar scales, using distance units smaller than this does not make much sense. And yet they are there. Here are their approximate values:

1 light second ≈ 300,000 km;

1 light minute ≈ 18,000,000 km;

1 light hour ≈ 1,080,000,000 km;

1 light day ≈ 26,000,000,000 km;

1 light week ≈ 181,000,000,000 km;

1 light month ≈ 790,000,000,000 km.

Now, so that you understand where the numbers come from, let’s calculate what one is equal to light year.

There are 365 days in a year, 24 hours in a day, 60 minutes in an hour, and 60 seconds in a minute. Thus, a year consists of 365 x 24 x 60 x 60 = 31,536,000 seconds. In one second, light travels 300,000 km. Therefore, in a year its beam will cover a distance of 31,536,000 x 300,000 = 9,460,800,000,000 km.

This number reads like this: NINE TRILLION, FOUR HUNDRED AND SIXTY BILLION AND EIGHT HUNDRED MILLION kilometers.

Of course, the exact meaning light years slightly different from what we calculated. But when describing distances to stars in popular science articles, the highest accuracy is, in principle, not needed, and a hundred or two million kilometers will not play a special role here.

Now let's continue our thought experiments...

Scale.

Let's assume that modern spaceship leaves solar system with the third escape velocity (≈ 16.7 km/s). First light year he will overcome it in 18,000 years!

4,36 light years to the closest star system to us ( Alpha Centauri, see the image at the beginning) it will overcome in about 78 thousand years!

Our Milky Way galaxy, having a diameter of approximately 100,000 light years, it will cross in 1 billion 780 million years.

And to the big one closest to us galaxies, spaceship will arrive only after 36 billion years...

These are the pies. But in theory, even Universe arose only 16 billion years ago...

And finally...

One can begin to marvel at the cosmic scale even without going beyond solar system, because it itself is very large. This was demonstrated very well and clearly, for example, by the creators of the project If the Moon wereonly 1 pixel (If the Moon Were Just One Pixel): http://joshworth.com/dev/pixelspace/pixelspace_solarsystem.html.

With this, I think I’ll end today’s article. I am glad to welcome all your questions, comments and wishes in the comments below.

Galactic distance scales

Light year ( St. G., ly) is an extra-system unit of length equal to the distance traveled by light in one year.

More precisely, as defined by the International Astronomical Union (IAU), a light year is equal to the distance that light travels in a vacuum, unaffected by gravitational fields, in one Julian year (equal by definition to 365.25 standard days of 86,400 SI seconds, or 31,557 600 seconds). It is this definition that is recommended for use in popular science literature. In professional literature, parsecs and multiples of units (kilo- and megaparsecs) are usually used instead of light years to express large distances.

Previously (before 1984), a light year was the distance traveled by light in one tropical year, assigned to the epoch 1900.0. The new definition differs from the old one by approximately 0.002%. Since this unit of distance is not used for high-precision measurements, there is no practical difference between the old and new definitions.

Numeric values

A light year is equal to:

9,460,730,472,580,800 meters (approximately 9.46 petameters)
63,241.077 astronomical units (AU)
0.306601 parsecs

Related units

The following units are used quite rarely, usually only in popular publications:

1 light second = 299,792.458 km (exact)
1 light minute ≈ 18 million km
1 light hour ≈ 1079 million km
1 light day ≈ 26 billion km
1 light week ≈ 181 billion km
1 light month ≈ 790 billion km

Distance in light years

The light year is convenient for qualitatively representing distance scales in astronomy.

Scale	Value (St. years)	Description
Seconds	4 10 −8	The average distance to is approximately 380,000 km. This means that a beam of light emitted from the surface will take about 1.3 seconds to reach the surface of the Moon.
minutes	1.6·10−5	One astronomical unit is equal to approximately 150 million kilometers. Thus, light reaches the Earth in approximately 500 seconds (8 minutes 20 seconds).
Watch	0,0006	The average distance from the Sun is approximately 5 light hours.
Watch	0,0016	The devices of the Pioneer and series flying beyond, in about 30 years since the launch, have moved to a distance of about one hundred astronomical units from the Sun, and their response time to requests from the Earth is approximately 14 hours.
Year	1,6	The inner edge of the hypothetical is located at 50,000 a. e. from the Sun, and the outer one - 100,000 a. e. It will take about a year and a half for light to travel the distance from the Sun to the outer edge of the cloud.
	2,0	The maximum radius of the region of gravitational influence of the Sun (“Hill Spheres”) is approximately 125,000 AU. e.
	4,2	The closest one to us (not counting the Sun), Proxima Centauri, is located at a distance of 4.2 light years. of the year.
Millennium	26 000	The center of our Galaxy is approximately 26,000 light-years from the Sun.
Millennium	100 000	The diameter of our disk is 100,000 light years.
Millions of years	2.5 10 6	The closest M31 to us, the famous one, is 2.5 million light years away from us.
	3.14 10 6	(M33) is located 3.14 million light years away and is the most distant stationary object visible to the naked eye.
	5.8 10 7	The closest one, the Virgo cluster, is 58 million light years away from us.
	Tens of millions of light years	The characteristic size of galaxy clusters by diameter.
	1.5 10 8 - 2.5 10 8	The “Great Attractor” gravitational anomaly is located at a distance of 150-250 million light years from us.
Billions of years	1.2 10 9	The Great Wall of Sloan is one of the largest formations in the world, its dimensions are about 350 Mpc. It will take about a billion years for light to travel from end to end.
	1.4 10 10	The size of the causally connected region of the Universe. It is calculated from the age of the Universe and the maximum speed of information transmission - the speed of light.
	4.57 10 10	The accompanying distance from the Earth to the edge of the observable Universe in any direction; accompanying radius of the observable Universe (within the framework of the standard cosmological model Lambda-CDM).

Do you know why astronomers don't use light years to calculate distances to distant objects in space?

A light year is a non-systemic unit of measurement of distances in outer space. It is widely used in popular books and textbooks on astronomy. However, in professional astrophysics this figure is used extremely rarely and is often used to determine distances to nearby objects in space. The reason for this is simple: if you determine the distance in light years to distant objects in the Universe, the number will turn out to be so huge that it will be impractical and inconvenient to use it for physical and mathematical calculations. Therefore, instead of the light year in professional astronomy, a unit of measurement is used, which is much more convenient to operate when performing complex mathematical calculations.

Definition of the term

We can find the definition of the term “light year” in any astronomy textbook. A light year is the distance a ray of light travels in one Earth year. Such a definition may satisfy an amateur, but a cosmologist will find it incomplete. He will note that a light year is not just the distance that light travels in a year, but the distance that a ray of light travels in a vacuum in 365.25 Earth days, unaffected by magnetic fields.

A light year is equal to 9.46 trillion kilometers. This is exactly the distance a ray of light travels in a year. But how did astronomers achieve such precise determination of the ray path? We'll talk about this below.

How was the speed of light determined?

In ancient times, it was believed that light travels throughout the Universe instantly. However, starting in the seventeenth century, scientists began to doubt this. Galileo was the first to doubt the above proposed statement. It was he who tried to determine the time it takes for a ray of light to travel a distance of 8 km. But due to the fact that such a distance was negligibly small for such a quantity as the speed of light, the experiment ended in failure.

The first major shift in this matter was the observation of the famous Danish astronomer Olaf Roemer. In 1676, he noticed a difference in the time of eclipses depending on the approach and distance of the Earth to them in outer space. Roemer successfully connected this observation with the fact that the further the Earth moves away from, the longer it takes the light reflected from them to travel the distance to our planet.

Roemer grasped the essence of this fact accurately, but he failed to calculate the reliable value of the speed of light. His calculations were incorrect because in the seventeenth century he could not have accurate data on the distance from the Earth to the other planets of the solar system. These data were determined a little later.

Further advances in research and the definition of the light year

In 1728, the English astronomer James Bradley, who discovered the effect of aberration in stars, was the first to calculate the approximate speed of light. He determined its value to be 301 thousand km/s. But this value was inaccurate. More advanced methods for calculating the speed of light were produced without regard to cosmic bodies - on Earth.

Observations of the speed of light in a vacuum using a rotating wheel and a mirror were made by A. Fizeau and L. Foucault, respectively. With their help, physicists managed to get closer to the real value of this quantity.

Exact speed of light

Scientists were able to determine the exact speed of light only in the last century. Based on Maxwell's theory of electromagnetism, using modern laser technology and calculations corrected for the refractive index of the ray flux in air, scientists were able to calculate the exact speed of light as 299,792.458 km/s. Astronomers still use this quantity. Further determining the daylight hours, month and year was already a matter of technology. Through simple calculations, scientists arrived at a figure of 9.46 trillion kilometers—that’s exactly how long it would take a beam of light to travel the length of the Earth’s orbit.