Astronomers identify a star that would look green

Astronomers at the University of Warwick in England have identified a stellar remnant that would look yellow-green to human eyes, according to their calculations. The team says it is the first credible example of a green star.

Called WD J1330+6435, the object lies about 280 light-years from Earth. It is a white dwarf, the dense core left behind when a star like the Sun reaches the end of its life. Its colour cannot be appreciated directly at that distance. Instead, the researchers analysed its spectrum, the pattern of wavelengths in its light, using a model of human colour vision.

Most stars owe their colour largely to temperature. Here, chemistry changes the picture. Rocky debris from the dwarf’s planetary system has added elements including sodium to its atmosphere. Under the atmosphere’s extremely dense conditions, sodium absorbs a broad band of yellow, orange and some red light, leaving the light with a green tint.

The study, published in RAS Techniques and Instruments, also found that white dwarfs can appear pink, purple, yellow and cyan. In a separate sample of 151 white dwarfs within about 65 light-years of Earth, five had unusual colours. That suggests roughly one in 30 white dwarfs may depart from the familiar range of stellar colours.