The concept of light-year is often misleading. The very existence of the word year has led many to associate the expression with a temporal unit. However, it is the unit of measurement for longitude used in the field of astronomy, so instead of saying "take a light year", people say "be a light year away".
In this article we are going to tell you what a light year is, how it is measured, examples and much more.
What is a light-year
This concept works as a unit of measurement in astronomy that quantifies the distance that a photon or a particle of light can travel within the vacuum of one year. In numerical terms, One light year is equal to 9,46 x 1012 km or 9.460.730.472.580,8 km. This unit was specifically designed to measure vast sidereal distances extending over billions of kilometers. These distances require a specific measure to express them in an easily understandable way.
The International Astronomical Union provides the precise definition of a light year, abbreviated as ly or ly in English. To measure it, the Julian calendar (instead of the Gregorian) and the speed of light (calculated at 299.792.458 meters per second) must be taken into account. Therefore, the duration of a year in which light travels a distance in space is equal to 365,25 days, instead of 365,2425 days as in the Gregorian calendar.
Like other distance measurement units, this measurement can be expanded to higher multiples by adding a prefix to the numeric value. For example, a distance of 1.000 light-years can be expressed as a kilo-light-year, or kly, while a distance of 1.000.000 light-years can be expressed as a mega-light-year, or gly.
The origin of the concept
In the mid-61th century, Friedrich Bessel, a German astronomer and mathematician, established the concept of the light year as a unit of measurement. Bessel's groundbreaking achievement was the precise calculation of the distance from Earth to a star other than the Sun, specifically the star XNUMX Cygni located in the constellation Cygnus. This distance amounted to astonishing amount of 98.734.594.662 kilometers or 61.350.985.287,1 miles, Those were pretty hard numbers to handle. To circumvent this problem, Bessel chose to express this distance in terms of the amount of time it takes for light to travel this distance, which is approximately 10,3 years.
During the time period in which Bessel was working, the speed of light had not yet been precisely determined, which led him to avoid using the term "light year" in his calculations. Otto Ule, a German popular science writer, introduced the concept of a "light year" in 1851 and proposed that it be used in a similar way to a "march hour."
This unit of measurement was initially viewed as an astronomical unit by the German academy, although some, such as Britain's astrophysicist Arthur Eddington, they were against its adoption, considering it cumbersome, impractical, and better suited to popular science.
Examples of distances measured in light years
When measured in light years, certain spatial distances become particularly significant. Let's see some of the most representative examples where scientists use this unit of measurement:
- The Milky Way, our own galaxy, has a diameter of about 150.000 light-years. For comparison, Andromeda, its neighboring galaxy, has a diameter of about 240.000 light-years. The two galaxies are separated by a distance of 2.500.000 light years.
- At the outer edge of Our solar system is located in the Oort Cloud., and the distance between this cloud and the Sun is about 1 light year.
- next Centauri, the closest star to the Sun, it is 4,22 light years away.
- The dwarf galaxy Canis Major, which is the closest to the Milky Way, is separated from it by a distance of 25.000 light years.
- The local group of galaxies, including the Milky Way, It has an estimated diameter of 10.000.000 light years.
- The Virgo Supercluster, which encompasses the Local Group of galaxies, has an estimated diameter of 200 light-years.
- The Pisces-Cetus supercluster complex, which includes the Virgo Supercluster, has an estimated diameter of 1.000.000.000 light-years.
- La Great Wall of Hercules-Corona Borealis, the largest observable astronomical structure in the universe, has an approximate diameter of more than 10.000.000.000 light-years.
Other astronomical units of measurement
Apart from this well-known astronomical unit of measurement, there are other units of measurement that are used to represent the great distances between celestial bodies and space formations. Several of these units are derived from the light year, including the light month, light day, light hour, light minute, and light second. These units operate on the same principle and are frequently used in popular science, telecommunications, and relativistic physics.
Astronomy specialists tend to favor the use of astronomical units that exceed one light-year in length. Examples of such units include:
- Named for the English parallax of one arc second, The parsec (pc) is a unit of measurement equivalent to 3,2616 light years.
- By calculating the average distance between Earth and the Sun, scientists established the astronomical unit (AU) as the equivalent of 8 light minutes.
Astronomy students tend to prefer the astronomical unit as their preferred unit of measurement due to its relatively fixed value, which can be expressed in simpler terms. On the other hand, the value of the light year is subject to contextual considerations, such as whether the measurement is taken in a vacuum or whether the Julian or Gregorian calendar is being used.
The light year is a less precise and more complex unit of measurement than others. However, it has the advantage of being a very descriptive representation of the great distances between celestial objects. This is because light, which is the fastest entity in the universe, is used as a reference point to measure these distances.
I hope that with this information you can learn more about what the light year is and how it is measured.
