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, according to the International Astronomical Union (IAU) definition, a light year equal to the distance, which 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.
	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 is 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. year.
Millennium	26 000	The center of our Galaxy is located approximately 26,000 light years from the Sun.
	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 entities In , 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. Calculated from the age of the Universe and maximum speed transmission of information - 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).



Light year- an unsystematic unit of distance measurement in astronomy.
Numerically, one light year equal to the distance light travels in one year.
More precisely, a light year is the distance that light travels in a vacuum, without the influence of gravitational fields, in one Julian year (365.25 days or 31,557,600 standard seconds).
In Russian literature, the light year is designated “St. g.", in foreign: "ly"

What is one equal to? light year:
Light year in kilometers: 9,460,730,472,580.8 km.
9 460 730 472 580 800 meters
63,241.077 astronomical units (AU)
1 light year is equal to 0.306601 parsecs.

In addition to the light year, there are also fractions of the light year: light month, light week, light hour, light minute and light second. They are rare, but it will be interesting to see how different distances are expressed in these units:

The light year is a fairly convenient unit of distance measurement in astronomy. The highest speed at which information can spread in our world is the speed of light. Therefore, distances expressed in light years simultaneously show how quickly one space object can affect another.

For example, you've probably heard that the star Betelgeuse in the constellation Orion is expected to explode in the foreseeable future (in fact, within a few centuries).
Betelgeuse is located at a distance of 495 to 640 light years from us.
If it explodes right now, then the inhabitants of the Earth will see this explosion only in 500-600 years.
And if you see an explosion today, then remember that in fact the explosion occurred around the time of Ivan the Terrible...
This example clearly shows how convenient the light year is - it simultaneously shows both distance and time.

Light year - how many Earth years is it?

How many Earth years are there in a light year? Enough strange question, but sometimes it occurs... A light year is a measure of distance, as written above, and an earthly year is a measure of time. Therefore, the answer to the question, how many Earth years are in one light year, will be - none :-)

 or tell your friends:

Cosmic distances are difficult to measure in ordinary meters and kilometers, so astronomers use other physical units. One of them is called a light year.


Many fantasy fans are very familiar with this concept, as it often appears in films and books. But not everyone knows what a light year is, and some even think that it is similar to the usual annual calculation of time.

What is a light year?

In reality, a light year is not a unit of time, as one might assume, but a unit of length used in astronomy. It refers to the distance traveled by light in one year.

It is usually used in astronomy textbooks or popular science fiction to determine lengths within solar system. For more accurate mathematical calculations or measuring distances in the Universe, another unit is taken as a basis - .

The appearance of the light year in astronomy was associated with the development of stellar sciences and the need to use parameters comparable to the scale of space. The concept was introduced several years after the first successful measurement of the distance from the Sun to the star 61 Cygni in 1838.


Initially, a light year was the distance traveled by light in one tropical year, that is, in a period of time equal to the full cycle of seasons. However, since 1984, the Julian year (365.25 days) began to be used as a basis, as a result of which the measurements became more accurate.

How is the speed of light determined?

To calculate a light year, researchers had to first determine the speed of light. Astronomers once believed that the propagation of rays in space was instantaneous, but in the 17th century this conclusion began to be questioned.

The first attempts to make calculations were made by Galileo Gallilei, who decided to calculate the time it takes light to travel 8 km. His research was unsuccessful. James Bradley managed to calculate the approximate value in 1728, who determined the speed at 301 thousand km/s.

What is the speed of light?

Despite the fact that Bradley made fairly accurate calculations, they were able to determine the exact speed only in the 20th century, using modern laser technologies. Advanced equipment made it possible to make calculations corrected for the refractive index of rays, resulting in this value being 299,792.458 kilometers per second.


Astronomers operate with these figures to this day. Subsequently, simple calculations helped to accurately determine the time that the rays needed to fly around the orbit. globe without the influence of gravitational fields on them.

Although the speed of light is not comparable to earthly distances, its use in calculations is explained by the fact that people are accustomed to thinking in “earthly” categories.

What is a light year equal to?

If we take into account that a light second is equal to 299,792,458 meters, it is easy to calculate that light travels 17,987,547,480 meters in a minute. As a rule, astrophysicists use this data to measure distances inside planetary systems.

To study celestial bodies on the scale of the Universe, it is much more convenient to take as a basis a light year, which is equal to 9.460 trillion kilometers or 0.306 parsecs. Observing cosmic bodies is the only case when a person can see the past with his own eyes.

It takes many years for light emitted by a distant star to reach Earth. For this reason, when observing space objects, you see them differently from what they are in at the moment, and what they were like at the moment of light emission.

Examples of distances in light years

Thanks to the ability to calculate the speed of movement of rays, astronomers were able to calculate the distance in light years to many celestial bodies. Thus, the distance from our planet to the Moon is 1.3 light seconds, to Proxima Centauri - 4.2 light years, to the Andromeda nebula - 2.5 million light years.


The distance between the Sun and the center of our galaxy takes rays approximately 26 thousand light years, and between the Sun and the planet Pluto - 5 light hours.

Textbook for 7th grade

§ 4.6. Can distance be measured in years?

Distances between stars are measured in light years. One light year is equal to the distance that light travels in empty space in a year. This is a huge distance: after all, light travels in emptiness in 1 second, almost 300,000 km.

The closest star to us (not counting the Sun) is about 4 light years away from us. But it cannot be seen with the naked eye: it is quite dim. The bright star Alpha Centauri is located relatively close to it, but it is visible mainly to residents of the Southern Hemisphere.

But almost all inhabitants of the Earth can clearly see the brightest star in the night sky - Sirius. The light from Sirius has been coming to us for almost 9 years. Sirius is much larger and brighter than our Sun: if it were at the same distance from us as the Sun, it would seem to us 20 times brighter than it. However, we would not be able to enjoy this insanely bright spectacle - all life on Earth would instantly burn out. But thanks to the fact that Sirius is far enough from us, we can admire this brightest star as much as they want, and astronomers can study it without running the risk of being “burnt out of curiosity.” This study allowed them to determine the size of Sirius and even the temperature of its surface - despite the enormous distance to it!

With the help of modern powerful telescopes, astronomers study galaxies that are millions and even billions of light years away from us. Scientists see them as they were millions or billions of years ago: that's when they emitted the light that has reached us today. Therefore, by studying distant galaxies, scientists learn the distant past of our Universe, which arose about 13 billion years ago.

A light year is the distance that light travels in one year. The International Astronomical Union has given its explanation of the light year - this is the distance that light travels in a vacuum, without the participation of gravity, in a Julian year. The Julian year is equal to 365 days. It is this decoding that is used in scientific literature.

If we take professional literature, then the distance is calculated in parsecs or kilo- and megaparsecs.

There are specific numbers that determine the distance of light hours, minutes, days, etc.

• A light year is equal to 9,460,800,000,000 km,
• month- 788,333 million km.,
• week- 197,083 million km.,
• day- 26,277 million km,
• hour- 1,094 million km.,
• minute- about 18 million km.,
• second- about 300 thousand km.

This is interesting! From the Earth to the Moon, light travels on average in 1.25 seconds, while its beam reaches the Sun in just over 8 minutes.

The star Betelgeuse in the constellation Orion should explode in the foreseeable future (in fact, within a few centuries).

Betelgeuse is located at a distance of 495 to 640 light years from us.
If it explodes right now, then the inhabitants of the Earth will see this explosion only in 500-600 years.

And if you see an explosion today, then remember that in fact the explosion occurred around the time of Ivan the Terrible...

Earth year

An earthly year is the distance traveled by the earth in one year. If we take into account all the calculations, then one light year is equal to 63242 Earth years. This figure applies specifically to planet Earth; for others, for example Mars or Jupiter, they will be completely different. A light year calculates the distance from one object celestial body to another. The numbers for light years and earth years are so different, although they mean distance.

Scale

Video

Sources

Quick answer: not at all.

We are often asked very interesting questions, the answers to which are very non-standard.

You see one of these questions in the title. And really, how many earthly years are there in one bright year? You may be disappointed, but there is no real answer.

The fact is that a bright year is not a measure of time, but a distance measure. To be more precise, a light year is the distance of distance in a vacuum without gravity fields, one effect of the Julian year (equivalent to 365.25 standard days per 86,400 SI seconds or 31,557,600 seconds) by the International Astronomical Federation.

To do this, we take the 300 thousand kilometers per second mark (that's exactly the speed of light) and multiply it with 31.56 million seconds (many seconds per year) and we get a huge number - 9460800000,000 km (or 9.46 million kilometers). This fantastic number means a distance equal to a light year.

• 1 light month ~ 788,333,000,000 km

• 1 easy week ~ 197,083,000 km

• 1 daylight ~ 26,277 million km

• 1 light hour ~ 1,094 million km

• 1 light minute ~ about 18 million km

• 1 light second ~ 300 thousand km

To find out how many kilometers in a light year you need to use a simple web calculator.

In the left box, enter the number of light years of interest you want to convert. In the field on the right you will see the calculation result. Simply click the appropriate link to convert light years or miles to other units.

What is “bright summer”

The light year of the one-way system (St., ly) is equal to the distance traveled by light in a vacuum in one July year (365.25 days).

This term is mainly used in science and fiction, and in the professional environment the term “parsecs” with the prefix “kilo” and “mega” was adopted.

and not before 1984, according to bright year, to understand the distance with light traveled in a tropical year, the value has now changed by 0.002%, and the practical value of this difference is because it is very precise measurements are not produced in light years. The speed of light is about 300 thousand.

km per second and a luminous year of about 10 trillion kilometers (9460.8800 million km). Regarding distances, for example, Sirius is 8 light years from its closest proximity to the star Proxima Centauri - 4.22 light years, and the diameter of the Roman road - our galaxy, which is 100,000 light years.

What is a "kilometer"

The kilometer kilometer (km, km) is a plural unit of reference distances, widely used throughout the world.

One kilometer 1000 meters, 0.621 miles, 0.9374 miles, 1094 yards, 3281 meters, 1.057 x 10 - 13 light years, 6.67 x 10 - 9 astronomical units.

Easy years

For hundreds of years, people have been inventing their own planet to invent more and more remote sensing systems. Therefore, it was decided to take into account a universal unit of one meter in length and a long measuring path of kilometers.

But in the next twentieth century it created new problem for humanity. People began to carefully study the universe - and it turned out that the size of the universe is so large that miles are simply not suitable here.

In ordinary units you can express the distance from the Earth to the Moon or from the Earth to Mars. But if you're trying to figure out how far the nearest star is from our planet, the number "grows" with an imperceptible number of characters per decimal point.

What is 1 light year?

It was obvious that a new space exploration unit was needed - and it was a bright year.

In a second, light travels 300,000 kilometers. Easy years — this is the distance whose light will travel exactly a year, and when translated into a more familiar system of numbers, this distance is 9,460,730,472,580.8 kilometers. It is clear that using a concise “simple flight” is much more convenient than using every huge number in calculations.

Of all the stars closest to us, Proxima Centauri was only “4.2 light years away.” Of course, based on kilometer data there is an unimaginable amount. However, everything is relative - considering that the nearest Andromeda galaxy is separated from the Roman road by as much as 2.5 million light years, the star and the truth begin to seem very close neighbors.

By the way, using light years helps scientists understand in which corners of space it is reasonable to find intelligent life and where sending radio signals is completely useless.

After all, the speed of a radio signal is similar to the speed of light, so a greeting sent towards a distant galaxy would take millions of years to reach its destination. It makes sense to expect a response from neighboring “neighbors” - objects whose hypothetical response signals will reach ground-based devices even during a person’s lifetime.

1 light year - how many Earth years?

There is a common misconception that a light year is a unit of time.

Actually this is not true. This term has nothing to do with Earth years, it does not refer to them and only represents the distance that light travels in one Earth year.