Light from distant stars has reached the coronagraph on NASA's Nancy Grace Roman Space Telescope for the first time. The instrument, built to block the glare of a star so that faint planets and dust disks around it become visible, saw its first light on September 22. NASA reported the milestone on October 2.
A coronagraph only works if the telescope barely moves. Planets are far fainter than their stars and sit very close to them in the sky. The smallest wobble lets starlight leak in and hide them.
A dime from 150 miles
During tests in September, Roman held its aim to better than 1/100,000 of a degree. It kept that precision for 30 minutes with its main camera, the Wide Field Instrument, and for eight hours with the coronagraph. NASA compares it to keeping a laser on a dime 150 miles away, and expects to improve it to 230 miles.
The coronagraph's first targets were faint stars in the Large Magellanic Cloud, a small galaxy near the Milky Way. With its detectors cooled, it produced sharp images.
"This observation confirms that the instrument can produce a focused image," says Vanessa Bailey, the coronagraph's instrument scientist at NASA's Jet Propulsion Laboratory. The telescope has shown it can hold still. That is the first condition for everything else.
