Scientists Say: Proxima Centauri | Science News for Students

# Scientists Say: Proxima Centauri

This is our nearest stellar neighbor
Oct 31, 2016 — 7:00 am EST

This is Proxima Centauri, the star closest to our sun. Its red glow marks it as a red dwarf.

ESA/Hubble & NASA

#### Proxima Centauri (noun, “PROX-ih-mah sen-TOR-aye”)

This is a star located about 4.2 light-years away from our sun. Its name is composed of Latin words. They mean “nearest star of Centaurus.” (Proxima Centauri is part of the Centaurus constellation.) It’s the nearest-known star to the sun. But it's a different type of star. Proxima Centauri is a red dwarf — a small, red glowing star that is about 2,800 degrees Celsius (5,000 degrees Fahrenheit) cooler than our sun.

#### In a sentence

Scientists recently found that a planet may be orbiting Proxima Centauri — making it the closest planet outside our solar system.

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## Power Words

constellation     Patterns formed by prominent stars that lie close to each other in the night sky. Modern astronomers divide the sky into 88 constellations, 12 of which (known as the zodiac) lie along the sun’s path through the sky over the course of a year. Cancri, the original Greek name for the constellation Cancer, is one of those 12 zodiac constellations.

extraterrestrial     Anything of or from regions beyond Earth.

light-year     The distance light travels in one year, about 9.48 trillion kilometers (almost 6 trillion miles). To get some idea of this length, imagine a rope long enough to wrap around the Earth. It would be a little over 40,000 kilometers (24,900 miles) long. Lay it out straight. Now lay another 236 million more that are the same length, end-to-end, right after the first. The total distance they now span would equal one light-year.

mass     A number that shows how much an object resists speeding up and slowing down — basically a measure of how much matter that object is made from.

planet     A celestial object that orbits a star, is big enough for gravity to have squashed it into a roundish ball and it must have cleared other objects out of the way in its orbital neighborhood. To accomplish the third feat, it must be big enough to pull neighboring objects into the planet itself or to sling-shot them around the planet and off into outer space. Astronomers of the International Astronomical Union (IAU) created this three-part scientific definition of a planet in August 2006 to determine Pluto’s status. Based on that definition, IAU ruled that Pluto did not qualify. The solar system now includes eight planets: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune.

red dwarf     A type of smallish star that is relatively cool (and hence emits reddish light). Dwarfs are the most common size stars in the Milky Way.

solar system     The eight major planets and their moons in orbit around the sun, together with smaller bodies in the form of dwarf planets, asteroids, meteoroids and comets.

star     The basic building block from which galaxies are made. Stars develop when gravity compacts clouds of gas. When they become dense enough to sustain nuclear-fusion reactions, stars will emit light and sometimes other forms of electromagnetic radiation. The sun is our closest star.

stellar     An adjective that means of or relating to stars.

sun     The star at the center of Earth’s solar system. It’s an average size star about 26,000 light-years from the center of the Milky Way galaxy. Or a sunlike star.