Invisible Rings Around a Young Star: The Secret of Brightness
In the dusty disk around the young star CI Tau, astronomers found hidden rings using a clever trick—like guessing the location of unseen stones by their shadows on the water. These dense rings could be the birthplaces of planets. Could planetary embryos be hiding from our telescopes in such rings?
Young stars are often surrounded by rotating disks of gas and dust. Over time, planets form within these disks. But spotting the finest details in these disks is hard even for powerful telescopes. Recently, astronomers devised a new way to see what's hidden from direct view. They studied the star CI Tau, which is similar in size to our Sun. Using the ALMA radio telescope, they noticed that the disk's brightness varies in a telltale way: at its edges, where the disk appears thinner to us, two bright spots glow. It looks like peering at a thin pancake with chocolate chips: along the edges, where the batter is more transparent, the chocolate chips seem brighter. That's what's happening here: the disk contains narrow, dense rings of dust, and the gaps between them are almost empty. When we view the disk at an angle, these rings at the edges are most visible.
The method the scientists used is similar to spectroscopy—studying light at different wavelengths. They compared the disk's brightness in three radio "colors" and realized: the central part of the disk is almost transparent, while the rings are dense, like tiny beads. The distance to the rings is about 22 astronomical units, roughly the distance from the Sun to Uranus in our own system. The dust in these rings consists of sand-like substances, with a trace of carbon, while the gas is mostly hydrogen and helium. Such rings are ideal places for the birth of future exoplanets (planets around other stars). This discovery matters not just for one star: now astronomers can search for similar rings in other disks across our Galaxy using telescopes like Hubble or the new James Webb.
🎯 The star CI Tau is just 2 million years old—a mere infant by stellar standards. The newly found rings are narrower than the ALMA telescope’s beam, which is why no one spotted them before.