A Star's Leftovers May Be Building a Second-Generation Planet

NASA describes a chemical clue suggesting that the white dwarf star HS 0209+0832 may host a second-generation planet — a world built from material the star cast off rather than from whatever it formed alongside.

The mechanism is what makes the label useful. A white dwarf is the leftover core of a star that burned through all of its nuclear fuel and lost its outer envelope; a planet that forms from that cast-off gas and dust has a chemical content that is very different from a planet that formed as its host star was forming. That remains a proposed explanation rather than a confirmed world, but it is a tidy one: the end of a star's life as the start of another body's.