White dwarf stars, it turns out, come in a variety of hues. Says one astronomer: "Some of them genuinely surprised me."

High school science class taught us that stars come in very specific colors. You have cooler stars that are red, orange and yellow. Then you have hotter, larger stars that are white and blue. It turns out that much like the wind in the movie Pocahontas, stars also come in all sorts of colors, including green and pink.

The discovery was outlined in a study published this month in RAS Techniques and Instruments. According to the lead author, Mark Hollands of Warwick University’s astronomy and astrophysics group, the humble white dwarf star is the centerpiece of this chromatic curiosity. 

“Most stars, including most white dwarfs, behave like ‘perfect radiators,’ so their color is set almost entirely by temperature. But nobody had really looked into what else might be possible for white dwarfs,” Hollands said in a statement. “It turns out these incredibly dense stars can produce colors nobody expected, and some of them genuinely surprised me.”

Hollands says that the key is density and atmosphere. White dwarfs are among the densest objects in the known universe, and that also includes the atmosphere around the white dwarf. Thanks to the intense gravity, a white dwarf’s atmosphere — which is composed primarily of hydrogen and helium — can have some interesting interactions with trace amounts of other elements that are present. 

“For white dwarfs with a cool, helium-dominated atmosphere, as the star gets cooler, the helium becomes more and more transparent, which means you can see further into the star where the gas gets denser,” Hollands told CNET in an email.

Source link