Image Credit: NASA, ESA, and R. Soummer and A. Feild (STScI). Science Credit: NASA, ESA, R. Soummer (STScI), 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). Release images
Such is the case with four disks of planetary debris uncovered in
images of young stars that astronomers retrieved from the Barbara A.
Mikulski Archive for Space Telescopes (MAST). A fifth disk image, which
was an unpublished borderline detection by Hubble from 2007, was also
recovered. These disks are telltale evidence for newly formed planets.
This is an astronomical forensics story of revisiting earlier data
with new image processing techniques — and of some tenacious
astronomers. Rémi Soummer, of the Space Telescope Science Institute
(STScI) in Baltimore, Md., led the team on an Indiana Jones hunt for
hidden Hubble treasures.
The stars were initially targeted with Hubble's Near Infrared Camera
and Multi-Object Spectrometer (NICMOS) based on unusual heat signatures
obtained from NASA space-based telescopes, including IRAS (Infrared
Astronomical Satellite) and the Spitzer Space Telescope. The previous
data provided interesting clues that dusty disks might exist around
these stars. Such disks might be seen in scattered light from small dust
particles. But when Hubble first viewed the stars between 1999 and
2006, no visible-light disks were detected in the NICMOS pictures.
Recently, 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 disks, and they could even determine their shapes.
"These findings increase the number of debris disks 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 disks, Hubble can
help astronomers learn more about how planetary systems form and
evolve," said Soummer.
The dust in the disks is hypothesized to be produced by collisions
between small planetary bodies such as asteroids. The debris disks 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 considered to be collisional byproducts.
"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 that 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.
The NICMOS instrument, which began taking data in 1997, was so
cutting-edge that ground-based technology is only now beginning to
match its power. Because Hubble has been in operation for 24 years, it
provides a long baseline of high-quality archival observations. "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.
Once Soummer's team began to apply the new algorithm to the old data,
the disks immediately started appearing. "I remember we tried it, and
we thought, 'It's not possible. We've done something wrong!' The disks
popped out immediately," explained Soummer. "It worked so well, and the
results came up so quickly, that at first we didn't believe them."
"Being able to see these disks 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 are also working to implement the same techniques as a standard
processing method for the upcoming James Webb Space Telescope," said
STScI teammate Laurent Pueyo. "These disks will also be prime targets
for the Webb Telescope."
Soummer's team has just begun its work. They will next search for structures in the disks that suggest the presence of planets.
The Space Telescope Science Institute in Baltimore, Md., conducts
Hubble Space Telescope (HST) science operations. HST is a project of
international cooperation between NASA and the European Space Agency.
NASA's Goddard Space Flight Center in Greenbelt, Md., manages the
telescope. STScI is operated by the Association of Universities for
Research in Astronomy, Inc., in Washington, D.C.
The Mikulski Archive for Space Telescopes, located at STScI, is a
NASA-funded project to support and provide to the astronomical community
a variety of astronomical data archives, with the primary focus on
scientifically related data sets in the optical, ultraviolet, and
near-infrared parts of the spectrum.
CONTACT:
Ann Jenkins / Ray VillardSpace Telescope Science Institute, Baltimore, Md.
410-338-4488 / 410-338-4514
jenkins@stsci.edu / villard@stsci.edu
Rémi Soummer
Space Telescope Science Institute, Baltimore, Md.
410-338-4737
soummer@stsci.edu
Source: Hubble Site
