Scientists Say: Yellow dwarf | Science News for Students

Scientists Say: Yellow dwarf

This is a medium-sized star — like our sun
Oct 8, 2018 — 6:30 am EST

This is an image of our sun, which is a yellow dwarf star. The tiny black dot at the upper left corner is the planet Venus passing in front of it.


Yellow dwarf (noun, “YEH-low DWAR-f”)

This is the term used to describe a medium-sized star. These stars are also known as “G dwarf stars” and “G-type main-sequence stars.” One notable characteristic of these stars is their size. Yellow dwarf stars are between 0.84 and 1.15 times the mass of our sun. Our sun (which is one solar mass) is a yellow dwarf star.

The phrase “yellow dwarf” isn’t quite right, because not all yellow dwarf stars are yellow. Some are white. Our sun is one of these; it is actually white. People perceive it as yellow because we view it through our atmosphere, which distorts its color.  

In a sentence

The Parker Solar Probe is heading for our own yellow dwarf, and will swoop into the sun’s corona in November 2018.

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Power Words

(more about Power Words)

atmosphere     The envelope of gases surrounding Earth or another planet.

corona     The envelope of the sun (and other stars). The sun’s corona is normally visible only during a total solar eclipse, when it is seen as an irregularly shaped, pearly glow surrounding the darkened disk of the moon.

distort     (n. distortion) To change the shape or image of something in a way that makes it hard to recognize, or to change the perception or characterization of something (as to mislead).

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.

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.

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. Also a term for any sunlike star.

yellow dwarf     A medium-sized star. Our sun is an example of a yellow dwarf.