_(2024-117).jpg) Temperature map of WASP-43b | |
| Discovery[1] | |
|---|---|
| Discovered by | Coel Hellieret al. |
| Discovery site | La Silla Observatory /South African Astronomical Observatory |
| Discovery date | Published April 15, 2011 |
| transit method (secondary occultation detected later) | |
| Designations | |
| Astrolábos[2] | |
| Orbital characteristics | |
| 0.01526 (± 0.00018)[3]AU | |
| Eccentricity | < 0.0298[3] |
| 0.81347753 (± 0.00000071)[3]d | |
| Inclination | 82.33 (± 0.20)[3] |
| Star | WASP-43 |
| Physical characteristics | |
| 1.04+0.07 −0.09[4]RJ | |
| Mass | 2.03 (± 0.1)[4]MJ |
| Albedo | <0.06[5] |
| Temperature | 1479±13 K (1,206 °C; 2,203 °F, dayside) 755±46 K (482 °C; 899 °F, nightside)[6] |
WASP-43b, formally namedAstrolábos,[2] is atransitingplanet in orbit around the young, active, and low-massstarWASP-43 in the constellationSextans. The planet is ahot Jupiter with a mass twice that ofJupiter, but with a roughly equal radius. WASP-43b was flagged as a candidate by theSuperWASP program, before they conducted follow-ups using instruments atLa Silla Observatory in Chile, which confirmed its existence and provided orbital and physical characteristics. The planet's discovery was published on April 14, 2011.[1]
WASP-43b has anorbital period of approximately 0.8 days (19.2 hours), which at the time of discovery was the third-shortest known, surpassed only byWASP-19b andWASP-47e.[1] At the time of its discovery, the size of WASP-43b's orbit was the smallest known for a hot Jupiter,[1] probably due to its host star's low mass.
In August 2022, this planet and its host star were included among 20 systems to be named by the thirdNameExoWorlds project.[7] The approved names, proposed by a team fromRomania, were announced in June 2023. WASP-43b is namedAstrolábos and its host star is namedGnomon, after thegnomon and the Greek word for theastrolabe.[2]
WASP-43 was first flagged as host to a potentialtransiting event (when a body crosses in front of and dims its host star) by data collected bySuperWASP, a British organization working to discover transiting planets across the entirety of the sky. In particular, WASP-43 was observed first by the leg of WASP-South at theSouth African Astronomical Observatory between January and May 2009.[1]
Later observation by both SuperWASPs in theNorthern andSouthern Hemispheres led to the collection of 13,768 data points between January and May 2010 and to the use of theCORALIE spectrograph atLa Silla Observatory in Chile. Fourteen measurements using theradial velocity method confirmed WASP-43b as a planet, revealing its mass in the process. The use of La Silla'sTRAPPIST telescope helped the science team working on the planet to create alight curve of the planet's transit in December 2010.[1]
The initial discovery was published in the journalAstronomy and Astrophysics in 2011.[1] This was followed by reporting of a second transit in 2014,[8] and a full observation of the phases of the planet later that year.[9]
WASP-43 is aK-type star in theSextans constellation that is about 80parsecs (261light years) away.[1] The star has amass 0.58 times that of the Sun, but is more diffuse, with aradius 0.93 times that of the Sun. The star'seffective temperature is 4,400K, making the star cooler than the Sun, and is metal-poor with regards to the Sun because it has ametallicity of [Fe/H] = −0.05 (89% the amount of iron in the Sun).[4] The star is young, and is estimated to be 598 million years old (as compared to the Sun's 4.6 billion years).[4] Analysis of emission lines indicate that WASP-43 is an active star.[1]
WASP-43 has one detected planet in its orbit, WASP-43b. The star has anapparent magnitude of 12.4, and thus is too faint to be seen with the unaided eye from Earth.[4]
_(WASP43b-1).jpg)
WASP-43b is a densehot Jupiter with a mass 2.05 times themass of Jupiter, but aradius 1.036 times that of Jupiter's. The planet orbits its host star at amean distance of 0.01526AU every 0.813478 days (19.5235 hours);[4] thisorbital period, at the time of WASP-43b's discovery, was the second-shortest orbit yet detected, surpassed only byWASP-19b. In comparison,Mercury has an orbital period of 87.97 days and lies at a mean distance of 0.387 AU from the Sun.[10] In addition, WASP-43b had the closest orbit to its host star (among hot Jupiters) at the time of its discovery, comparable only to thesuper-Earth planetGJ 1214 b and to the planetary candidate orbiting KOI-961 (confirmed a year later asKepler-42). While hot Jupiters are known to have small orbital periods, planets withexceptionally small periods below three or four days are extremely rare; however, in the case of WASP-43b, the planet's proximity can be explained because its host star has a very low mass. The rarity of systems like that of WASP-43 and its planet suggest that hot Jupiters do not usually occur around low-mass stars, or that such planets cannot maintain stable orbits around such stars.[1]
WASP-43b, along with the planets WASP-19b andWASP-18b, conflicted with currently accepted models of tidal movements derived from observations of the orbits ofbinary star systems. Revisions to the model with regard to planets were proposed to help the models conform to the orbital parameters of these planets.[1] No orbital decay driven by tidal dissipation was detected in 2016, placing a lower limit of 10 million years on the remaining planetary lifetime.[11] Updated orbital period measurements have failed to detect orbital decay as of 2021.[12][13]
In 2019, the spectrum of WASP-43b was taken, with the best fit being water-containing clouds without significant amounts of alkali metals.[14]In 2020, further analysis of the spectra revealed the presence of bivalent aluminum oxide (AlO) and water in the atmosphere,[15] while carbon monoxide, carbon dioxide and methane were not detected. Climate modelling suggests the carbon monoxide concentration may be variable, while the atmospheric spectrum of WASP-43b is dominated by clouds made of refractory mineral particles, with a small contribution from hydrocarbon haze.[16] Carbon to oxygen ratio in the planet (0.75±0.15) is elevated compared to the Solar ratio of 0.55.[17] The planet is very dark overall, with no clouds on the dayside[6] and an albedo below 0.06.[5] In 2024, theJames Webb Space Telescope observed that the skies are clear on the day side and is cloudy on its night side, with winds of 5,000 miles per hour.[18]
There is a large difference in temperature between dayside (1479±13K) and nightside (755±46K).[6]
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