Astronomers recently discovered an unseen, interstellar object moving through the Milky Way. Specifically, researchers at the National Astronomical Observatory of Japan (NAOJ) uncovered evidence of a rare type of black hole, according to a study shared on the preprint server ArXiv.

If their findings are accurate, this black hole, roughly the size of Jupiter, would be only the third of its kind ever detected in our galaxy, according to New Scientist.

Although the team didn’t directly observe the black hole—it is, after all, invisible—they did spot a cloud of gas orbiting something using Chile’s Atacama Large Millimeter/submillimeter Array, as reported by Space.com.

“When I first examined the ALMA data, I was thrilled because the motion of the gas clearly indicated orbital movements, strongly hinting at an unseen massive object,” said Shunya Takekawa, an astrophysicist at the NAOJ, in an interview with New Scientist.

From the gas cloud’s orbital path, the team inferred that the newly found black hole is about 3,000 times heavier than our Sun but compact enough to only occupy the space of Jupiter. Given that roughly 1,000 Jupiters could fit into the Sun, this means the black hole is 3 million times denser than the Sun.

Scientists are more familiar with smaller black holes created from collapsing stars and with the supermassive black holes at the center of galaxies like the Milky Way.

This discovery raises the possibility that there are many more medium-sized black holes roaming the Milky Way. Now that astronomers know to look for gas clouds spiraling around these objects, other research teams may soon identify more of these rare and mysterious black holes.