Imaging advance reveals planetary discs in Hubble archive
Sen—Astronomers using the Hubble Space Telescope have applied a new image-processing technique to obtain near-infrared scattered light photos of five discs observed around young stars, which are telltale evidence for newly formed planets.
Thanks to the wealth of information stored in the Hubble data archive, astronomers can make new discoveries by revisiting earlier data with new methods for producing the images. This is what Rémi Soummer, of the Space Telescope Science Institute (STScI) and his team recently did while on a hunt for hidden Hubble treasures.
The stars in question initially were targeted with Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) based on unusual heat signatures obtained from NASA's Spitzer Space Telescope and the Infrared Astronomical Satellite that flew in 1983.
The previous data provided interesting clues that dusty discs could exist around these stars. Small dust particles in the discs might scatter light and therefore make the discs visible. But when Hubble first viewed the stars between 1999 and 2006, no discs were detected in the NICMOS pictures.
With improvements in image processing, including algorithms used for face-recognition software, Soummer and his team reanalyzed the archived images. This time, they could unequivocally see the debris discs and even determine their shapes.
Debris discs HD 141943, HD 191089, HD 202917, HD 30447, HD 35841. Image credit: NASA, ESA, and Z. Levay (STScI)
"Now, with such new technologies in image processing, we can go back to the archive and conduct research more precisely than previously possible with NICMOS data," said Dean Hines of STScI. See the full range of images here on the HubbleSite.
"These findings increase the number of debris discs seen in scattered light from 18 to 23. By significantly adding to the known population and by showing the variety of shapes in these new discs, Hubble can help astronomers learn more about how planetary systems form and evolve," said Soummer.
The dust in the discs is thought to be produced by collisions between small planetary bodies such as asteroids. The debris discs are composed of dust particles formed from these grinding collisions. The tiniest particles are constantly blown outward by radiation pressure from the star. This means they must be replenished continuously though more collisions. This game of bumper cars was common in the Solar System 4.5 billion years ago. Earth's moon and the satellite system around Pluto are reckoned to be byproducts of ancient collisions.
The previous image of HD 181327, left, and one produced with the new technique, right, which filters out the residual starlight and clearly reveals the entire debris disk. Image credit: NASA, ESA, R. Soummer and M. Perrin (STScI), L. Pueyo (STScI/Johns Hopkins University), C. Chen and D. Golimowski (STScI), J.B. Hagan (STScI/Purdue University), T. Mittal (University of California, Berkeley/Johns Hopkins University), E . Choquet, M. Moerchen, and M. N’Diaye (STScI), A. Rajan (Arizona State University), S. Wolff (STScI/Purdue University), J. Debes and D. Hines (STScI), and G. Schneider (Steward Observatory/University of Arizona)
"One star that is particularly interesting is HD 141943," said Christine Chen, debris disk expert and team member. "It is an exact twin of our Sun during the epoch of terrestrial planet formation in our own Solar System."
Hubble found the star exhibits an asymmetrical, edge-on disk. This asymmetry could be evidence the disk is being gravitationally sculpted by the tug of one or more unseen planets.
"Being able to see these discs now also has let us plan further observations to study them in even more detail using other Hubble instruments and large telescopes on the ground," added Marshall Perrin of STScI.
"We also are working to implement the same techniques as a standard processing method for NASA's upcoming James Webb Space Telescope," said STScI teammate Laurent Pueyo. "These discs will also be prime targets for the Webb telescope."