TOI-178 is a

planetary system A planetary system is a set of gravity, gravitationally bound non-stellar Astronomical object, bodies in or out of orbit around a star or star system. Generally speaking, systems with one or more planets constitute a planetary system, although ...

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 ...

Sculptor Sculpture is the branch of the visual arts that operates in three dimensions. Sculpture is the three-dimensional art work which is physically presented in the dimensions of height, width and depth. It is one of the plastic arts. Durable sc ...

Requête spécifique à TOI-178
sur

VizieR A vizier (; ; ) is a high-ranking political advisor or Minister (government), minister in the Near East. The Abbasids, Abbasid caliphs gave the title ''wazir'' to a minister formerly called ''katib'' (secretary), who was at first merely a help ...

. around which six planets have been observed, at at least five of which orbit in a chain of Laplace resonances, which constitute one of the longest chains yet discovered in a system of planets. The system also has unusual variations in the densities among the planets. The system is 205

light-year A light-year, alternatively spelled light year (ly or lyr), is a unit of length used to express astronomical distances and is equal to exactly , which is approximately 9.46 trillion km or 5.88 trillion mi. As defined by the International Astr ...

s away, which is relatively close, implying that such systems may be relatively common. The brightness of the star, TOI-178, facilitates followup observations, which make it an ideal system in which to expand our understanding of planet formation and evolution. The planetary system was confirmed by data provided by five different planet search projects. After

TESS Tess or TESS may refer to: Film and theatre * Tess (1979 film), ''Tess'' (1979 film), a 1979 film adaptation of ''Tess of the d'Urbervilles'' * Tess (2016 film), ''Tess'' (2016 film), a South African production Music * Tess (band), a Spanish pop ...

provided first hints at a system with an interesting resonant chain, additional observations to refine the measurement and confirm the finding were provided by

CHEOPS Khufu or Cheops (died 2566 BC) was an ancient Egyptian monarch who was the second pharaoh of the Fourth Dynasty, in the first half of the Old Kingdom period (26th century BC). Khufu succeeded his father Sneferu as king. He is generally accep ...

ESPRESSO Espresso (, ) is a concentrated form of coffee produced by forcing hot water under high pressure through finely ground coffee beans. Originating in Italy, espresso has become one of the most popular coffee-brewing methods worldwide. It is cha ...

NGTS The Next-Generation Transit Survey (NGTS) is a ground-based robotic search for exoplanets. The facility is located at Paranal Observatory in the Atacama Desert in northern Chile, about 2 km from European Southern Observatory, ESO's Very Lar ...

and

SPECULOOS Speculoos (; ; ) is a biscuit, originally manufactured in Belgium, made from wheat flour, candy syrup (from beet sugar), fat, and sometimes cinnamon. Speculoos were developed in the 20th century around the area of Verviers, as an alternative fo ...

. Over the coming years, observations of

transit-timing variation Transit-timing variation is a method for detecting exoplanets by observing variations in the timing of a transit. This provides an extremely sensitive method capable of detecting additional planets in the system with masses potentially as small a ...

s in the transits of the various planets, which are expected to range from minutes to tens of minutes, should help pin down the planetary masses and uncover the eccentricities of the various orbits.

Planetary system and orbital resonance

Of the six planets, named TOI-178b through TOI-178g as per IAU convention, the outer five are locked in a chain of Laplace resonances. The periods of the planets, in days, revolving around the star are b = 1.91, c = 3.24, d = 6.56, e = 9.96, f = 15.23, and g = 20.71. While this is not a perfect integer ratio, there exists a frame of reference that rotates by roughly 1.37° day⁻¹, in which successive conjunctions of the planets form a repeating pattern. For an observer rotating within this frame of reference, the planets c through g form a chain of resonance that can be expressed as 2:4:6:9:12 in ratios of periods, or as 18:9:6:4:3 in ratios of orbits, which means that for every eighteen revolutions of the planet c, the planet d completes nine, the planet e six, the planet f four, and the planet g three. In addition, the planet b orbits close to where it would also be a part of the same resonant chain. In a slightly bigger orbit of period of ~1.95 days, it would form a 3:5 resonance with the planet c in the same corotating frame of reference as the other five. It is possible that the entire system originally formed in one long resonant chain, but later the innermost planet was pulled out of it, perhaps by

tidal interactions The tidal force or tide-generating force is the difference in gravitational attraction between different points in a gravitational field, causing bodies to be pulled unevenly and as a result are being stretched towards the attraction. It is the d ...

References

{{DEFAULTSORT:TOI-178 Sculptor (constellation) K-type main-sequence stars 178, TOI J00291228-3027133 Planetary systems with six confirmed planets Planetary transit variables

Planetary system and orbital resonance

See also

References