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Astronomers have used the Kepler Space Telescope to observe changes in the brightness of stars in the Pleiades star cluster. Normally, the high brightness of these stars would be too much for Kepler's camera, but a new technique can ignore saturated pixels and glean information about changes in brightness:
While the central pixels in an image of a star become too saturated to take accurate scientific measurements of its brightness, the unaffected pixels around that superbright spot still contain accurate information. This is useful for measuring changes in the brightness of these so-called variable stars, the study's authors report.
"The solution to observing bright stars with Kepler turned out to be rather simple," Tim White, an astrophysicist at Aarhus University in Denmark and lead author of the study, said in the statement. "We're chiefly concerned about relative, rather than absolute changes in brightness. We can just measure these changes from nearby unsaturated pixels, and ignore the saturated areas altogether."
After measuring the light around a star, White and his colleagues found they still needed to adjust their data for any changes in the spacecraft's motion and possible imperfections in the camera's detector. Even the slightest error could prevent the researchers from detecting a star's variability, the authors suggest, adding those errors could be corrected using simple algorithms.
To account for any discrepancies in their measurements, the authors developed "a new technique to weight the contribution of each pixel to find the right balance where instrumental effects are canceled out, revealing the true stellar variability," the Royal Astronomical Society's press release said. White and his colleagues named this new technique "halo photometry."
No exoplanets were detected, but the technique could help Kepler, TESS, and the JWST to spot exoplanets around bright stars, including Alpha Centauri.
Also at the Royal Astronomical Society and the Stellar Astrophysics Centre.
Beyond the Kepler/K2 bright limit: variability in the seven brightest members of the Pleiades (DOI: 10.1093/mnras/stx1050) (DX) (arXiv)
(Score: 4, Interesting) by takyon on Monday September 04 2017, @03:43AM
A related concept is the starshade [wikipedia.org], meant to block out the brightness of a star in order to directly image exoplanets. This halo photometry technique embraces the brightness instead, allowing existing imagery to be studied with more use out of telescopes that aren't well suited to looking at bright objects. It's making the best of what is available today, although I think we would love to see a billion dollar starshade go up.
And then there's the gravitational lens telescope at 550 AU:
The Ultimate Space Telescope Would Use the Sun as a Gravitational Lens [airspacemag.com]
[SIG] 10/28/2017: Soylent Upgrade v14 [soylentnews.org]