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Forms of Light: Omega Centauri

Decoding starlight Full Story Below

Star field showing variation between stars. Star field showing variation between stars.
Same stars with differences in which are bright and dim. Same stars with differences in which are bright and dim.
More differences in brightness with fewer stars. More differences in brightness with fewer stars.
Same stars, but very few, are bright compared to others. Same stars, but very few, are bright compared to others.
Colored images shows blue, white and red stars. Colored images shows blue, white and red stars.
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Although all stars emit light in a variety of wavelengths, those that stand out in one view tell us more about their makeup.

Orange dwarf stars are small and cool, lead long lives over billions of years, and stand out in visible light.

Yellow dwarf stars are hotter than red giants and orange dwarf stars, and are detected in near-ultraviolet light.

Stars at the end of their lives, which have exposed, hot cores, are brightest in this view.

Since all of these stars are about the same distance from Earth, researchers can compare their brightnesses and temperatures.

Near-Infrared
Visible
Near-Ultraviolet
Mid-Ultraviolet
Multi-Wavelength

Forms of Light: Omega Centauri

Mapping the lifecycle of stars with light.

Human eyes have evolved to detect the rainbow of colors that make up visible light. Some objects, like stars and light bulbs, emit their own light. Other matter, like plants and animals, can be detected because they reflect visible light from other sources.

Visible light is only one form of light. There are other types of electromagnetic radiation that human eyes cannot see. Objects that do not give off their own visible light (and are therefore invisible to our eyes in the dark) can glow in other wavelengths, like infrared or ultraviolet. The entire range of light, from radio waves to gamma rays, is known as the electromagnetic spectrum.

Omega Centauri is among the biggest and most massive globular star clusters that orbit our Milky Way galaxy, and has been observed across the electromagnetic spectrum. The average distance between any two stars in the cluster’s crowded core is only about a third of a light-year, roughly 13 times closer than our sun’s nearest stellar neighbor, Proxima Centauri. Since its stars are all approximately the same distance from Earth, researchers have used Omega Centauri to plot the brightness of individual stars. The color indicates the temperature of the star. Hotter stars appear bluer and cooler stars appear redder. Astronomers compare the brightnesses and colors of individual stars to create what’s known as the Hertzsprung-Russell diagram.

Quick Facts: Omega Centauri

Also known as: NGC 5139 and Caldwell 80

Distance from Earth: 16,000 light-years

Size: Entire cluster is about 150 light-years across, approximately 6 light-years shown above

Type of object: Globular star cluster

Location in the sky: Centaurus Constellation

Did you know: When ancient astronomer Ptolemy identified this object 2,000 years ago, he thought it was a single star, but it’s now known to contain nearly 10 million stars.

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Find out more with these additional resources from NASA’s Universe of Learning

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Watch “Electromagnetic Spectrum: The Musical”
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Credits: Omega Centauri

All images from the Hubble Space Telescope: NASA, ESA, and the Hubble SM4 ERO Team

Content development by Claire Blome, Dr. Kelly Lepo, Yesenia Perez

Design by Zena Levy

Web development by Isaar Sadr, Lara Wilkinson

Subject-matter expertise provided by Dr. Jay Anderson