We are very lucky, as we live on a planet, which orbits at the life-favoring distance from the Sun. It is also very likely, that the currently available technologies could let us also live on the Moon and – perhaps in a not so distant future – on Mars. Hypothetically, the extraterrestrial life forms could exist under significantly harsher environmental conditions, like on Venus or Saturn’s Titan. But if a planet simply gets burned by its host star, nothing can be saved, no matter how tough those aliens could be.

The exoplanet Kepler-91b experiences exactly this scenario: the hot-Jupiter type celestial body is currently in a stage before it gets completely engulfed by its mother-star. Kepler-91b was ‘demoted’ this year from a planet candidate to a self-luminous object due to the large albedo not typical to regular planets (study by Esteves et al.). However, a recent study, which was conducted by an international team of astronomers from Spain, Belgium, Germany, Chile and Italy, provides a careful analysis of observational data confirmed this transiting object to be a planet, although not a lucky one. The complete scientific paper describing the results of this study can be accessed at arXiv.org.

The team analyzed photometric data from the Kepler telescope to verify the transit parameters of Kepler-91b. Additionally, the light-curve modulations and accurate stellar parameters were measured and analyzed using CAFE spectrograph data. AstraLux North instrument, which is mounted on the 2.2 meter telescope at the Calar Alto Observatory (CAHA, Spain) and provides high-resolution images, was also used to reject false-positive stellar configuration that could potentially mimic the planetary transit.

The scientists used computer simulation to determine that Kepler-91b mass is approximately 14% smaller compared to Jupiter’s mass, whereas its radius is roughly 1.38 times larger. The analysis of the stellar parameters showed that the outer atmospheric layers of the K3 giant host star are expanding and will reach the planet’s orbital pericenter in less than 55 million years. The astrophysical measurements also indicate a strongly inflated low-density atmosphere present on Kepler-91b: the authors note, that this is a very likely result of the strong surface irradiation induced by the closely residing star.

Approximately 36% of the planet’s day-sky is currently covered by the star, considering the large stellar radius and a very close orbit. A single sufficiently strong stellar flare probably would not be enough to incinerate Kepler-91b entirely, but it could reduce its remaining lifespan by one or two million years…

By Alius Noreika, Source: www.technology.org