first_imgOver 500 planets are known to exist orbiting other stars, and there are many more we know about that are waiting to be verified. However, it’s rare to actually have direct images of the planets since stars are billions of times brighter than planets. And, since planets happen to always be close to the star they’re orbiting, it makes it hard to see them through telescope photos since the star’s light tends to overwhelm the light of the planets.Astronomers have recently revealed three exoplanets that they captured back in 1998 using the Hubble Space Telescope while taking photos of the Sun-like HR 8799 star. The images resulted in just a bright light from the star, and no exoplanets to be seen. Then, in 2008, the Gemini telescope took images of HR 8799 and found four planets orbiting the star. The technology between 1998 and 2008 had changed enough that the astronomers were able to remove the star’s light using the Gemini telescope images, whereas that technology wasn’t around in ’98.Thirteen years later, astronomers have gone back to the HST photos using new methods to clean up the images. Their work revealed three out of the four exoplanets. It’s almost like cleaning an old painting and finding something the artist had painted but had been hidden from the world for hundreds of years.So how does the technique work? According to Phil Plait of Bad Astronomy, the technique relies on a database of images of 466 stars observed in the same way as the star in question. “By adding them together digitally,” Plait said, “a very accurate model of the target star can be made, and used to literally subtract the star’s light.”One of the great things about this discovery is that the ’98 image provides a “much longer baseline over which we can see the planets,” Plait said. Since planets are constantly moving, comparing the location of the planets from the ’98 images to the location of the planets in the ’08 images allows astronomers to measure the motion of the planets as they orbit the star. They were able to determine that planet d takes about 100 years to circle the star, planet c takes 200 years, and planet b takes 400 years. The fourth planet, planet e, is too close to the star to be seen with the new method.As Plait aptly points out, we can only wonder how many other planets are there out there that we’ve already captured in photos but didn’t have the technology at the time to clean up and reveal?via Bad Astronomylast_img read more