The cosmos is full of puzzling objects such as starless worlds that come in pairs. Did these worlds form like planets? Or are they more like tiny failed stars? Astronomers are not sure.
When Galileo Galilei, a mathematician at the University of Padua, trained a spyglass of his own creation on the sky, he was overwhelmed with what he saw — more than 500 new stars in the constellation Orion, in addition to the familiar three in the hunter’s belt and six in the sword.
In October, astronomers used the James Webb Space Telescope to zoom in on one of the middle stars in the sword and identified another 500 or so previously unseen spots. The worlds are so small and dim that they blur the line between star and planet. It’s an ambiguity that plagued Galileo, who referred to the moons of Jupiter as both “stars” and “planets” in the same page of his 1610 astronomical treatise, and it continues to trouble astronomers today.
“When we look at the solar system it’s all nice and neat. You get the sun, and you get planets,” said Samuel Pearson, an astronomer with the European Space Agency (ESA). There’s nothing in the middle. But “when you actually go and have a look,” Pearson said, “you realize there’s a full spectrum of [objects with] basically every mass in between.”