Young and hot: This is an artist’s illustration of the giant planet HR 8799b. First discovered in 2007, it was recently found hidden in archival data from the Hubble Space Telescope. It is slightly larger than Jupiter and may be at least seven times more massive.
Credit: NASA, ESA, and G. Bacon (STScI)
Hubble images of previously discovered exoplanets can also provide more detail about the physical characteristics of the planets, because NICMOS uses near-infrared wavelengths that are mostly blocked by Earth's atmosphere, Marois said.
Measurements at these wavelengths reveal the amount of water vapour in the planet's atmosphere, which can in turn tell about the planet's temperature, cloud cover or atmospheric pressure.
"Look again at old data"
The Hubble telescope has been gathering data for more than ten years and has a huge archive. The development of the adapted LOCI algorithm highlights the importance of maintaining this kind of archive, Lafreniere said.
"I hope this realisation will motivate people to look again at old data," he said.
Chris Tinney, an astrophysicist at the University of New South Wales in Sydney, Australia, said that if the LOCI algorithm ever does find an undiscovered exoplanet, it would be an astounding breakthrough.
"The fact it was used to recover an already-known planet in old data makes it interesting, but not exactly exciting," Tinney said.
