U.S. #5599
2021 55¢ Sun Science – Coronal Loops
Issue Date: June 18, 2021
First Day City: Greenbelt, MD
Type of Stamp: Commemorative
Printed by: Banknote Corporation of America
Printing Method: Flexographic, Foil Stamping
Format: Pane of 20
Self-Adhesive
Quantity Printed: 18,000,000
Some people call the Sun a yellow dwarf star. However, this is more of a nickname than an actual scientific designation. (The Sun is officially classified as a G-type main-sequence star.). It is easy to understand how this got started, since G-type main-sequence stars tend to range in color from white to pale yellow.
However, sometimes our Sun appears in other colors. This is because of the way visible light is scattered by Earth's atmosphere. This phenomenon makes the Sun, and sky, appear orange, red, and other vibrant colors at sunrise and sunset. In reality, our Sun is actually white – the brightest intensity of light the human eye can distinguish. But, the Sun looks completely different when viewed in the ultraviolet or other higher-level spectrums. That is why NASA uses a number of special filters when studying certain parts of the Sun.
Our Sun is not the only G-type main-sequence star in our corner of space. Several nearby stars fall into the same category. These include Alpha Centauri A, Tau Ceti, and 51 Pegasi. Tau Ceti may be the most similar of these three to our Sun. It, too, has planets thought to be capable of supporting life (a similar distance from their star as Earth is from the Sun). It makes you wonder what other "suns" might be out there...