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A star is what it eats. Consuming a planet or two early in its life may explain why some young stars are iron-rich – and those habits can change its colour.

Last year, a team of scientists led by of the University of São Paulo, Brazil, a young, particularly iron-rich star may have gotten its metals from eating a planet early in its development.

Now, and of the University of Pisa, Italy, have shown how that star’s planet-eating habits can change its colour.

The pair used computer simulations to compare what happens when planets of various sizes – from Earth-like to 50 times more massive – get enveloped by the outer layer of a young star. This showed that swallowing one or more planets containing iron is enough to change the chemical make-up of the star, giving it a reddish tint.

“The main effect of the planet ingestion is to increase the metal content in the outer region of the star,” the researchers told Â鶹´«Ã½. The metals absorb light in shorter, bluer wavelengths, making its red hues more prominent.

Hungry stars

It’s similar to how flamingos become pinker with every pigment-rich shrimp they slurp – but on a solar scale.

Since this happens early on in a star’s evolution, it’s hard to say if more mature stars had planet-eating habits in their youth. But it’s possible that our sun ate one or more planets long ago, say Tognelli and Prada Moroni.

Spina says the study did a good job of simulating what happens to small stars that eat planets. “The model is excellent,” he says. “It takes into account all the effects produced by such a dramatic event.”

There’s still much more to learn, though. “We do not know if stars often ingest planets,” Spina says. And since a star gulps a planet down quickly, it’s probably a tricky event to watch in real time. “The change in colour due to a planet engulfment episode has not been observed yet, and probably is still difficult to spot,” he says.

Journal reference: arXiv, arxiv.org/abs/1605.07920

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