200 Light Years In Miles

Schematic portraying a light-year: A large yellow shell outside smaller shell with arrows point from center to each. — The big yellow shell depicts a light-year; the smaller yellow shell depicts a light-month. Read more near this paradigm at Wikimedia Commons.

Objects in our universe are extremely far away. They're then far away that kilometers or miles aren't a useful mensurate of their distance. So nosotros speak of infinite objects in terms of light-years, the distance low-cal travels in a year. Lite is the fastest-moving stuff in our universe. It travels at 186,000 miles per second (300,000 km/sec). And thus a low-cal-year is 5.88 trillion miles (9.46 trillion kilometers).

But stars and nebulae – not to mention afar galaxies – are vastly farther than 1 low-cal-year abroad. And, if we try to express a star's distance in miles or kilometers, we before long end up with impossibly huge numbers. Nonetheless miles and kilometers are what most of us use to comprehend the distance from i place on Earth to some other. In the belatedly 20th century astronomer Robert Burnham, Jr. – author of Burnham'southward Celestial Handbook – devised an ingenious manner to portray the distance of light-years in terms of miles and kilometers.

Go on reading, for a mode to comprehend the vastness of the universe, using units of altitude we know and apply every day.

Burnham started by relating the light-year to the astronomical unit – the Earth-sun altitude.

One astronomical unit of measurement, or AU, equals near 93 million miles (150 million km).

Another way of looking at information technology: the astronomical unit is a scrap more than 8 light-minutes in altitude.

Diagram of sun, Earth, moon, labeled, with line between labeled 150,000,000 kilometers. — A light axle takes 8 minutes to travel the 93 million miles (150 one thousand thousand km) from the lord's day to the Earth. Prototype via Brews Ohare/ Wikimedia Eatables.

A light-yr, pictured every bit a mile

Robert Burnham noticed that, quite past coincidence, the number of astronomical units in one light-year and the number of inches in i mile are virtually the same.

For general reference, there are 63,000 astronomical units in one calorie-free-year, and 63,360 inches (160,000 cm) in one mile (1.6 km).

This wonderful coincidence enables u.s. to bring the light-year down to Earth. If we calibration the astronomical unit of measurement – the World-sun distance – at i inch, then the light-yr on this scale represents one mile (one.half-dozen km).

The closest star to Earth, other than the lord's day, is Blastoff Centauri at some 4.iv light-years away. Scaling the Earth-sun distance at one inch places this star at 4.4 miles (7 km) distant.

See?

Star field with a red star at center. — The blood-red star in the heart of this pic is Proxima Centauri, our sun's nearest neighbor amongst the stars. A beam of light from this star takes almost 4 years to travel to Earth. Prototype via Max Planck Institute for Extraterrestrial Physics.

Familiar space objects, conceptualized

Scaling the astronomical unit at 1 inch (2.5 cm), here are distances to various bright stars, star clusters and galaxies:

Alpha Centauri: 4.4 miles (6.4 km)

Sirius: 8.six miles (14 km)

Vega: 25 miles (forty km)

Pleiades open star cluster: 444 miles (715 km)

Antares: 555 miles (893 km)

Hercules globular star cluster (aka M13): 22,200 miles (35,700 km)

Heart of our Milky Way galaxy: 26,100 miles (42,000 km)

Swell Andromeda milky way (M31): two,540,000 miles (4,100,000 km)

Sombrero galaxy (M104): 28,000,000 miles (45,000,000 km)

Whirlpool galaxy (M51): 31,000,000 miles (50,000,000 km)

And and so on, dorsum to approximately 13 billion+ light-years to the farthest galaxies: 13,000,000,000 miles (21,000,000,000 km)

Okay, the numbers are still pretty big! But hopefully they tin can help you see that our universe is very vast.

Schematic of the stellar neighborhood of the sun, with sun in center and labeled stars, scale and arrow towards galactic center. — There are 33 stars within 12.5 light years of our sunday. Click into Atlas of the Universe to notice an interactive folio that'll let you keep zooming farther and further out. Image via Atlasoftheuniverse.com.

The fastest-moving stuff in the universe

Every bit mentioned to a higher place, light travels at an incredible 186,000 miles per 2nd (300,000 km/sec). That'southward very fast. If you lot could travel at the speed of light, you would exist able to circle the Globe's equator about seven.five times in just one 2d!

In other words, a lite-second is the altitude lite travels in 1 2d, or 7.5 times the distance effectually Globe'due south equator. A light-twelvemonth is the distance light travels in 1 year.

How far is that? Multiply the number of seconds in one year past the number of miles or kilometers that calorie-free travels in one second, and there you have it: one lite-yr. It's near five.ix trillion miles (9.five trillion km).

Diagram of earth with arrows to moon, sun, star, cluster and galaxy, depicting distances. — This scale starts shut to home merely takes us all the way out to the Andromeda Galaxy, the well-nigh distant object about people can encounter with the unaided centre. Paradigm via Bob Male monarch/ Skyandtelescope.com.

Bottom line: Here's a way to empathize the scale of light-years in miles and kilometers.

Read another article answering the same question: What is a light-year?

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Bruce McClure

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About the Writer:

Bruce McClure served as lead writer for EarthSky's popular Tonight pages from 2004 to 2021, when he opted for a much-deserved retirement. He's a sundial aficionado, whose beloved for the heavens has taken him to Lake Titicaca in Bolivia and sailing in the Northward Atlantic, where he earned his celestial navigation certificate through the School of Ocean Sailing and Navigation. He too wrote and hosted public astronomy programs and planetarium programs in and around his home in upstate New York.