On February 22, 2017, NASA reported that 7 exoplanets were found around the single star TRAPPIST-1. Three of them are in the range of distances from the star in which the planet can have liquid water, and water is a key condition for life. It is also reported that this star system is located 40 light years from Earth.
This message caused a lot of noise in the media; some even thought that humanity was one step away from building new settlements near nova, but that's not true. But 40 light years is a lot, it’s a LOT, it’s too many kilometers, that is, it’s a monstrously colossal distance!
The third is known from the physics course escape velocity- this is the speed that a body must have at the surface of the Earth in order to go beyond the limits solar system. The value of this speed is 16.65 km/sec. Conventional orbital spaceships start at a speed of 7.9 km/sec and revolve around the Earth. In principle, a speed of 16-20 km/sec is quite accessible to modern earthly technologies, but no more!
Humanity has not yet learned to accelerate spaceships faster than 20 km/sec.
Let's calculate how many years it will take a starship flying at a speed of 20 km/sec to travel 40 light years and reach the star TRAPPIST-1.
One light year is the distance that a beam of light travels in a vacuum, and the speed of light is approximately 300 thousand km/sec.
A human-made spaceship flies at a speed of 20 km/sec, that is, 15,000 times slower than the speed of light. Such a ship will cover 40 light years in a time equal to 40*15000=600000 years!
Earth ship (at modern level technology) will reach the star TRAPPIST-1 in about 600 thousand years! Homo sapiens has existed on Earth (according to scientists) for only 35-40 thousand years, but here it is as much as 600 thousand years!
In the near future, technology will not allow humans to reach the star TRAPPIST-1. Even promising engines (ion, photon, cosmic sails, etc.), which do not exist in earthly reality, are estimated to be able to accelerate the ship to a speed of 10,000 km/sec, which means that the flight time to the TRAPPIST-1 system will be reduced to 120 years . This is already a more or less acceptable time for flight using suspended animation or for several generations of immigrants, but today all these engines are fantastic.
Even the nearest stars are still too far from people, too far, not to mention the stars of our Galaxy or other galaxies.
The diameter of our Milky Way galaxy is approximately 100 thousand light years, that is, the journey from end to end for a modern Earth ship will be 1.5 billion years! Science suggests that our Earth is 4.5 billion years old, and multicellular life approximately 2 billion years. The distance to the closest galaxy to us - the Andromeda Nebula - 2.5 million light years from Earth - what monstrous distances!
As you can see, of all the living people, no one will ever set foot on the earth of a planet near another star.
It is this definition that is recommended for use in popular science literature. IN professional literature to express long distances instead of light years Parsecs and multiples of units (kilo- and megaparsecs) are commonly used.
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 distance unit is not used for high-precision measurements, practical difference there is no difference between old and new definitions.
Numeric values
A light year is equal to:
- 9,460,730,472,580,800 meters (approximately 9.5 petameters)
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 the Moon is approximately 380,000 km. This means that a beam of light emitted from the surface of the Earth 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 travels from the Sun to Earth in approximately 500 seconds (8 minutes 20 seconds). |
| Watch | 0,0006 | The average distance from the Sun to Pluto is approximately 5 light hours. |
| 0,0016 | The Pioneer and Voyager series devices flying beyond the solar system, in about 30 years since launch, have moved to a distance of about one hundred astronomical units from the Sun, and their response time to requests from Earth is approximately 14 hours. | |
| Year | 1,6 | The inner edge of the hypothetical Oort cloud is located at 50,000 AU. 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 | Maximum area radius gravitational influence Sun (“Hill Spheres”) - approximately 125,000 AU. e. | |
| 4,22 | The closest star to us (not counting the Sun), Proxima Centauri, is located at a distance of 4.22 light years. of the year . | |
| Millennium | 26 000 | The center of our Galaxy is approximately 26,000 light-years from the Sun. |
| 100 000 | The diameter of the disk of our Galaxy is 100,000 light years. | |
| Millions of years | 2.5 10 6 | Closest to us spiral galaxy M31, the famous Andromeda galaxy, is 2.5 million light years away from us. |
| 3.14 10 6 | The Triangulum Galaxy (M33) is located 3.14 million light-years away and is the most distant stationary object visible to the naked eye. | |
| 5.9 10 7 | The closest cluster of galaxies, the Virgo cluster, is 59 million light-years away. | |
| 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 Universe, 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). |
Galactic distance scales
- An astronomical unit with good accuracy is equal to 500 light seconds, that is, light reaches the Earth from the Sun in about 500 seconds.
see also
Links
- International Organization for Standardization. 9.2 Measurement units
Notes
Wikimedia Foundation. 2010.
See what “Light Year” is in other dictionaries:
An extra-system unit of length used in astronomy; 1 S. g. equal to the distance traversed by light in 1 year. 1 S. g. = 0.3068 parsec = 9.4605 1015 m. Physical encyclopedic Dictionary. M.: Soviet encyclopedia. Chief Editor A. M. Prokhorov... ... Physical encyclopedia
LIGHT YEAR, unit of measurement astronomical distance, equal to the distance that light travels in outer space or in VACUUM for 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. Distance to nearest star(Proxima Centauri) 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 modern natural science. Glossary of basic terms
For their calculations, astronomers use special units of measurement that are not always clear ordinary people. This is understandable, because if cosmic distances were measured in kilometers, then the number of zeros would dazzle the eyes. Therefore, to measure cosmic distances it is customary to use much large quantities: astronomical unit, light year and parsec.
Quite often used to indicate distances within our native Solar System. If we can also express it in kilometers (384,000 km), then Pluto is the closest close way is approximately 4,250 million km, and this will be difficult to understand. For such distances it is time to use an astronomical unit (AU), equal to the average distance from earth's surface to the Sun. In other words, 1 a.u. corresponds to the length of the semimajor axis of our Earth’s orbit (150 million km). Now, if we write that the shortest distance to Pluto is 28 AU, and the shortest long haul may be 50 AU, this is much easier to imagine.
The next largest is a light year. Although the word “year” is present there, one should not think that we're talking about about the time. One light year is 63,240 AU. This is the path that a ray of light travels over the course of 1 year. Astronomers have calculated that from the most distant corners of the Universe, a ray of light takes more than 10 billion years to reach us. To imagine this gigantic distance, let’s write it in kilometers: 95000000000000000000000. Ninety-five billion trillion usual kilometers.
Scientists began to guess that light does not travel instantly, but at a certain speed, starting in 1676. It was at this time that a Danish astronomer named Ole Roemer noticed that the eclipses of one of Jupiter's satellites were beginning to lag, and this happened precisely when the Earth was heading in its orbit towards opposite side The sun opposite to where Jupiter was. Some time passed, the Earth began to move back, and eclipses again began to approach their previous schedule.
Thus, about 17 minutes of time difference were noted. From this observation it was concluded that it took light 17 minutes to travel a distance the length of the Earth’s orbit. Since the diameter of the orbit was proven to be approximately 186 million miles (now this constant is 939,120,000 km), it turned out that the light beam moves at a speed of about 186 thousand miles per second.
Already in our time, thanks to Professor Albert Michelson, who set out to determine as accurately as possible what a light year is, using a different method the final result was obtained: 186,284 miles in 1 second (approximately 300 km/s). Now, if we count the number of seconds in a year and multiply by this number, we find that a light year is 5,880,000,000,000 miles long, which corresponds to 9,460,730,472,580.8 km.
For practical purposes, astronomers often use a unit of distance called the parsec. It is equal to the displacement of the star against the background of other celestial bodies by 1"" when the observer is displaced by 1 radius
Whatever lifestyle we lead, whatever we do, one way or another, we use some units of measurement every day. We ask for a glass of water, warm up our own breakfast until certain temperature, visually assess how far we need to walk to the nearest post office, we arrange a meeting in certain time and so on. All these actions require
Not just calculations, but also a certain measurement of various numerical categories: distance, quantity, weight, time and others. In our Everyday life we use numbers regularly. And we have long been accustomed to these numbers, as if to some kind of instruments. But what happens when we get out of our everyday comfort zone and encounter something unusual for us? numerical values? In this article we'll talk about the fantastic figures of the Universe.
Universal spaces
The situation with cosmic distances is even more surprising. We are fully aware of the kilometers to the neighboring city and even from Moscow to New York. But it’s difficult to visualize distances when it comes to scale star clusters. It is now that we will need the so-called light year. After all, the distances even between neighboring stars are extremely large, and measuring them in kilometers or miles is simply irrational. And here the matter is not only in the difficulty of perceiving the huge resulting numbers, but in the number of their zeros. It becomes a problem to write the number. For example, the distance from Earth to Mars during the period of closest approach is 55.7 million kilometers. A value with six zeros. But Mars is one of our closest cosmic neighbors! The distance to the nearest star other than the Sun will be millions of times greater. And then, whether we measured it in kilometers or miles, astronomers would have to spend hours of their time just recording these gigantic quantities. A light year solved this problem. The solution was quite ingenious.
What is a light year equal to?
Instead of inventing a new unit of measurement, which is the sum of units of a smaller order (as happens with millimeters, centimeters, meters, kilometers), it was decided to tie distance to time. Actually, the fact that time is also physical field influencing events more
Moreover, interconnected and convertible with space, it was discovered by Albert Einstein and proven through his theory of relativity. Constant speed became the speed of light. And the passage of a certain distance by a light beam per unit of time gave new physical spatial quantities: light second, light minute, light day, light month, light year. For example, per second a beam of light (in space conditions - vacuum) travels a distance of approximately 300 thousand kilometers. It is easy to calculate that one light year is equal to approximately 9.46 * 10 15. So, the distance from the Earth to the nearest cosmic body, The Moon is a little more than one light second, and the Sun is about eight light minutes. The outermost bodies of the solar system modern ideas orbit at a distance of one light year. The next star closest to us, or rather, a system of double star, Alpha and Proxima Centauri, so far away that even the light from them reaches our telescopes only four years after their launch. And these are still the celestial bodies closest to us. Light from the other end milky way spends more than a hundred thousand years to get to us.
One way or another, in our daily lives we measure distances: to the nearest supermarket, to a relative’s house in another city, to, and so on. However, when it comes to the vastness of outer space, it turns out that using familiar values like kilometers is extremely irrational. And the point here is not only in the difficulty of perceiving the resulting gigantic values, but in the number of numbers in them. Even writing so many zeros will become a problem. For example, the shortest distance from Mars to Earth is 55.7 million kilometers. Six zeros! But the red planet is one of our closest neighbors in the sky. How to use the cumbersome numbers that result when calculating the distance even to the nearest stars? And right now we need such a value as a light year. How much is it equal? Let's figure it out now.
The concept of a light year is also closely related to relativistic physics, in which the close connection and mutual dependence of space and time was established at the beginning of the 20th century, when the postulates collapsed Newtonian mechanics. Before this distance value, larger scale units in the system
were formed quite simply: each subsequent one was a collection of units of a smaller order (centimeters, meters, kilometers, and so on). In the case of a light year, distance was tied to time. Modern science It is known that the speed of light propagation in a vacuum is constant. Moreover, she is maximum speed in nature, acceptable in modern relativistic physics. It was these ideas that formed the basis of the new meaning. A light year is equal to the distance a ray of light travels in one Earth calendar year. In kilometers it is approximately 9.46 * 10 15 kilometers. Interestingly, a photon travels the distance to the nearest Moon in 1.3 seconds. It's about eight minutes to the sun. But the next closest stars, Alpha, are already about four light years away.
Just a fantastic distance. There is an even larger measure of space in astrophysics. A light year is equal to about one-third of a parsec, an even larger unit of measurement of interstellar distances.
Speed of light propagation under different conditions
By the way, there is also such a feature that photons can at different speeds spread in different environments. We already know how fast they fly in a vacuum. And when they say that a light year is equal to the distance covered by light in a year, they mean exactly the empty space. However, it is interesting to note that under other conditions the speed of light may be lower. For example, in air environment photons scatter at a slightly lower speed than in a vacuum. Which one depends on the specific state of the atmosphere. Thus, in a gas-filled environment, the light year would be somewhat smaller. However, it would not differ significantly from the accepted one.