HST/NICMOS detection of HR 8799 b in 1998

TL;DR

This paper reports the first detection of exoplanet HR 8799 b in archival HST/NICMOS data from 1998, demonstrating an improved imaging technique that enhances sensitivity and provides valuable astrometric and atmospheric insights.

Contribution

The study introduces a novel image processing method that significantly improves exoplanet detection sensitivity in archival space telescope data, enabling earlier detection and better characterization.

Findings

Detection of HR 8799 b in 1998 data consistent with a 70 AU orbit

Improved sensitivity by a factor of ~10 over traditional methods

Atmospheric modeling suggests water absorption features

Abstract

Three planets have been directly imaged around the young star HR 8799. The planets are 5-13 Mjup and orbit the star at projected separations of 24-68 AU. While the initial detection occurred in 2007, two of the planets were recovered in a re-analysis of data obtained in 2004. Here we present a detection of the furthest planet of that system, HR 8799 b, in archival HST/NICMOS data from 1998. The detection was made using the locally-optimized combination of images algorithm to construct, from a large set of HST/NICMOS images of different stars taken from the archive, an optimized reference point-spread function image used to subtract the light of the primary star from the images of HR 8799. This new approach improves the sensitivity to planets at small separations by a factor of ~10 compared to traditional roll deconvolution. The new detection provides an astrometry point 10 years before the most recent observations, and is consistent with a Keplerian circular orbit with a~70 AU and low orbital inclination. The new photometry point, in the F160W filter, is in good agreement with an atmosphere model with intermediate clouds and vertical stratification, and thus suggests the presence of significant water absorption in the planet's atmosphere. The success of the new approach used here highlights a path for the search and characterization of exoplanets with future space telescopes, such as the James Webb Space Telescope or a Terrestrial Planet Finder.