WASP-76b is an

exoplanet An exoplanet or extrasolar planet is a planet outside the Solar System. The first confirmed detection of an exoplanet was in 1992 around a pulsar, and the first detection around a main-sequence star was in 1995. A different planet, first det ...

classified as a

Hot Jupiter Hot Jupiters (sometimes called hot Saturns) are a class of gas giant exoplanets that are inferred to be physically similar to Jupiter (i.e. Jupiter analogue, Jupiter analogues) but that have very short orbital periods (). The close proximity to t ...

. It is located in the

constellation A constellation is an area on the celestial sphere in which a group of visible stars forms Asterism (astronomy), a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object. The first constellati ...

Pisces and orbits its host star, WASP-76, at a distance of approximately . Its orbital period is approximately 1.8 days, and its mass is about 0.92 times that of

Jupiter Jupiter is the fifth planet from the Sun and the List of Solar System objects by size, largest in the Solar System. It is a gas giant with a Jupiter mass, mass more than 2.5 times that of all the other planets in the Solar System combined a ...

. The discovery of WASP-76b took place on October 21, 2013; as of 2022, it is the only known planet in the WASP-76 system. The equilibrium temperature of WASP-76b is estimated to be around , However, the measured daytime temperature is higher, reaching approximately .

Atmospheric composition

Data collected from the Hubble and

Spitzer Space Telescope The Spitzer Space Telescope, formerly the Space Infrared Telescope Facility (SIRTF), was an infrared space telescope launched in 2003, that was deactivated when operations ended on 30 January 2020. Spitzer was the third space telescope dedicate ...

s have provided evidence of

titanium oxide Titanium oxide may refer to: * Titanium dioxide (titanium(IV) oxide), TiO2 * Titanium(II) oxide (titanium monoxide), TiO, a non-stoichiometric oxide * Titanium(III) oxide (dititanium trioxide), Ti2O3 * Ti3O * Ti2O * δ-TiOx (x= 0.68–0.75) * Ti ...

and small amounts of

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

within the planet's atmosphere. Further analysis using higher-resolution spectra has revealed the presence of ionized elements such as

lithium Lithium (from , , ) is a chemical element; it has chemical symbol, symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard temperature and pressure, standard conditions, it is the least dense metal and the ...

sodium Sodium is a chemical element; it has Symbol (chemistry), symbol Na (from Neo-Latin ) and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 element, group 1 of the peri ...

magnesium Magnesium is a chemical element; it has Symbol (chemistry), symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 ...

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

manganese Manganese is a chemical element; it has Symbol (chemistry), symbol Mn and atomic number 25. It is a hard, brittle, silvery metal, often found in minerals in combination with iron. Manganese was first isolated in the 1770s. It is a transition m ...

potassium Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...

, and

iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...

. The existence of

was confirmed by the Gemini North Observatory in 2021; in 2022,

barium Barium is a chemical element; it has symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Th ...

was also detected. The atmosphere of WASP-76b is characterized as cloudy, predominantly grey, and exhibits significant thermal

incandescence Thermal radiation is electromagnetic radiation emitted by the thermal motion of particles in matter. All matter with a temperature greater than absolute zero emits thermal radiation. The emission of energy arises from a combination of electron ...

. In April 2024, it was suggested that a glory effect in the atmosphere of WASP-76b might be responsible for the observed increase in brightness of its eastern terminator zone. If this interpretation could be confirmed, it would become the first extrasolar glory-like phenomenon to be discovered.

Iron rain

In March 2020, an initial

spectroscopic analysis Spectroscopy is the field of study that measures and interprets electromagnetic spectra. In narrower contexts, spectroscopy is the precise study of color as generalized from visible light to all bands of the electromagnetic spectrum. Spectrosc ...

revealed the presence of neutral

in the atmosphere of WASP-76b. The conditions required for the vaporization and condensation of neutral iron were determined to be a temperature of and a lower temperature of for condensation. Under these specific temperature conditions, neutral iron could potentially precipitate like liquid rain. In May 2020, the

Hubble Space Telescope The Hubble Space Telescope (HST or Hubble) is a space telescope that was launched into low Earth orbit in 1990 and remains in operation. It was not the Orbiting Solar Observatory, first space telescope, but it is one of the largest and most ...

discovered that the previous spectrum of WASP-76b had been distorted by the light from a companion star. Subsequently, an updated atmospheric model was developed using the most recent spectrum data. The revised model indicates the presence of a cloudy

hydrogen Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...

helium Helium (from ) is a chemical element; it has chemical symbol, symbol He and atomic number 2. It is a colorless, odorless, non-toxic, inert gas, inert, monatomic gas and the first in the noble gas group in the periodic table. Its boiling point is ...

envelope and suggests the absence of previously reported neutral iron, including "iron rain." Additionally, only upper limits on the presence of

titanium Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...

and vanadium oxides were detected. By 2021, the controversy surrounding the presence of iron condensation had been resolved by demonstrating that the observed signal may also be due to temperature variations between different parts of the planet. However, existing data is insufficient to definitively distinguish between these two scenarios. Based on planetary atmospheric circulation models for WASP-76b, it is suggested that dense cloud layers composed of

aluminum oxide Aluminium oxide (or aluminium(III) oxide) is a chemical compound of aluminium and oxygen with the chemical formula . It is the most commonly occurring of several aluminium oxides, and specifically identified as aluminium oxide. It is commonly ...

, neutral iron, or magnesium orthosilicate may form. However, significant condensation of iron on the night side of the planet is not indicated by the available data.

Possible exomoon

It has been speculated that a possible hot evaporating exomoon orbiting around WASP-76b could be consistent with an extrasolar toroidal atmosphere.

References

{{Pisces (constellation) Exoplanets discovered by WASP Hot Jupiters Giant planets Exoplanets discovered in 2013

Atmospheric composition

Iron rain

Possible exomoon

See also

References