To a casual observer, all stars may appear white. But they are not. Stars come in different colors: Red, Blue, Orange, Yellow, and White.

They are differently colored because they have different surface temperatures. And objects at different temperatures emit different colors.

star colors
Star Colors in Fahrenheit (not Kelvins)

Hotter stars emit a shorter wavelength of light and appear blue or blue-white. While the cooler stars emit a longer wavelength of light and appear red.

We decided to test this for stars in our favorite constellation: the Orion. Orion is a very prominent winter constellation. It is in the shape of a “hunter” represented by bright stars Rigel and Betelgeuse that are diagonal to each other.

Rigel and Betelgeuse are among the top ten brightest stars in the sky. If you look closely (even better with small binoculars) you will notice that Rigel is blue while Betelgeuse is reddish-orange in color.

Orion Constellation (ground-based image)
Orion Constellation

Rigel is a blue-white supergiant star up to 100,000 times as bright as our sun. But it is far away: 860 light years from us. Because it is very hot (11,000 K) and because of its enormous brilliance, it appears very bright in the night sky in spite of the distance.

Betelgeuse is a red supergiant. And it is really a giant star. If we were put to replace our Sun at the center of the solar system with Betelgeuse it would engulf Earth and extend beyond Mars’ orbit. Betelgeuse is around 640 light years away and its temperature is only 3500K.

In comparison, the surface temperature of our sun is 5700 K or around 9800 Fahrenheit.

Arushi loves programming, space, science, and making. She created a Star Colors Globe to share information about the fascinating universe of stars, their colors, and temperatures as a part of our family space and science outreach activities.

rainbow-blue-1.jpg
Star Colors Globe giving the color of Rigel

Arushi used 2 lunch boxes, a RGB led strip, an arduino and some push buttons to create a star globe. She got the hexadecimal color codes of different bright stars from the Vendian website: http://www.vendian.org/mncharity/dir3/starcolor/ She used the hexadecimal codes in her arduino programme to generate the appropriate star colors.

When the user presses the button, say Rigel then the corresponding color of the star: Blue is lighted up. Similarly one can view colors of several other stars, including our Sun on how it appears from Earth (yellow) and how it would appear above the atmosphere (white).

The Star Colors Globe also displays a rainbow of different colors of the star that we see in our universe.

The Making of Star Colors Globe

making2
Making and wiring up the components
making3
Programming the Arduino with the hexadecimal color code of stars
making1
Coded and ready to close the lunch boxes!
star chart
Star Globe with corresponding Start Chart

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