Hubble observations used to answer important exoplanet questions

A substantial aspect of this research is that the team were able to make use of a large sample of exoplanets and an extremely large amount of data to determine trends, which can be used to predict behavior in other exoplanets

Archival observations of 25 very hot Jupiters by the NASA/ESA Hubble Space Telescope have been analyzed by an international team of astronomers, enabling them to solution five open questions vital that you our understanding of exoplanet atmospheres.

Amongst other findings, the team found that the presence of metal oxides and hydrides in the hottest exoplanet atmospheres was clearly linked to the atmospheres’ being thermally inverted.

Area of  exoplanet   science has lengthy since shifted its focus from just detection on to characterization, although characterization continues to be extremely challenging.

Thus far, the majority of research into characterization has been instructed towards modeling, or studies focusing on one or a few exoplanets. This new work, directed by researchers based in University College London (UCL), used the largest amount of archival data ever examined in one exoplanet atmosphere survey to analyze the atmospheres of twenty five exoplanets.

The majority of the data came from findings taken with the NASA/ESA Hubble Space Telescope. The prospect author, Quentin Changeat, points out: “ Hubble enabled the in-depth characterization of 25 exoplanets, and the amount of details we learnt about their particular chemistry and formation— thanks to a decade of intense watching campaigns— is incredible. ”

The technology team sought to find answers to five open questions about exoplanet atmospheres— an ambitious goal that they succeeded in reaching. Their questions probed what H– plus certain metals can tell us about the chemistry and flow of exoplanet atmospheres, and about planet formation.

They chose to investigate a wide range of hot Jupiters, using the intention of identifying developments within their sample population that might provide insight into exoplanet atmospheres more generally.

The study’s co-leader, Billy Edwards of UCL and the Commissariat à l’é nergie atomique et aux é nergies alternatives (CEA) said: “ Our document marks a turning point for your field: we are now moving from the characterization of individual exoplanet atmospheres to the characterization of atmospheric populations. ”

In order to check out their sample of 25 exoplanets, the team reanalysed an enormous amount of archival data, consisting of 600 hours associated with Hubble observations, which they complemented with more than 400 hours associated with observations from the Spitzer Space Telescope.

Their data contained eclipses for all 25 exoplanets, plus transits for 17 of them.

A good eclipse occurs when an exoplanet passes behind its star as seen from Earth, and a transit occurs every time a planet passes in front of the star. Eclipse and transportation data can both supply crucial information about an exoplanet’s atmosphere.

The particular large-scale survey yielded outcomes, with the team able to recognize some clear trends plus correlations between the exoplanets’ atmospheric constitutions and observed conduct.

A selection of their key findings related to the presence or absence of thermal inversions [6] in the atmospheres of their exoplanet sample.

They found that virtually all the exoplanets with a thermally inverted atmosphere were incredibly hot, with temperatures over 2000 Kelvin.

Importantly, this is sufficiently hot that the metallic varieties TiO (titanium oxide), VO (vanadium oxide) and FeH (iron hydride) are stable in an  atmosphere . Of the exoplanets displaying thermal inversions, almost all of all of them were found to have H–, TiO, VO or FeH in their atmospheres.

It is always challenging to attract inferences from such outcomes, because correlation does not always equal causation. However , the team were able to propose the compelling argument for precisely why the presence of H–, TiO, VO or FeH might lead to the thermal inversion— namely that most these metallic species are extremely efficient absorbers of outstanding light.

It might be that exoplanet atmospheres hot enough to maintain these species tend to be thermally inverted because they then soak up so much stellar light that will their upper atmospheres warm up even more.

Conversely, the team also available that colder hot Jupiters (with temperatures less than 2k Kelvin, and thus without H–, TiO, VO or FeH in their atmospheres) almost never had thermally inverted atmospheres.

A significant aspect of this research was that the team were able to use a large test of exoplanets and an extremely large amount of data to determine tendencies, which can be used to predict actions in other exoplanets.

This is extremely useful, because it provides insight into how planets may form, and also because it allows other astronomers to more effectively plan long term observations.

Conversely, if a paper studies a single exoplanet in excellent detail, whilst that is valuable it is much harder to extrapolate trends from. An improved understanding of exoplanet populations could also bring us closer to resolving open mysteries about our personal Solar System.

As Changeat says: “ Many issues such as the origins of the water in the world, the formation of the Moon, and the different evolutionary chronicles of Earth and Mars, are still unsolved despite our ability to obtain in-situ dimensions. Large exoplanet population studies, such as the one we existing here, aim at knowing those general processes. ”

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