Tucana–Horologium association

The Tucana–Horologium association (Tuc–Hor), or Tucana Horologium moving group, is a stellar association with an age of 45 ± 4 Myr and it is one of the largest stellar associations within . The association has a similar size to the Beta Pictoris moving group (BPMG) and contains, like BPMG, more than 12 stars with spectral type B, A and F. The association is named after two southern constellations, the constellation Tucana and the constellation Horologium.

The group was at first not recognized as an individual group, but stars within the group were first assigned to the Great Austral Young Association (GAYA). Only later did it become clear that this complex is divided into three groups: the Tucana-Horologium association, the Carina association and the Columba association.

Members The members of this young group are potential targets for directly imaged circumstellar disks and exoplanets. The stars are located close to Earth and the planets are young, so they give off more infrared light, which is suited for directly imaging techniques. AB Pictoris was considered a member of Tuc-Hor, but it is more likely a member of the Carina association.

The brightest-identified member of the association is the massive star Alpha Pavonis, which is leaving the main sequence. The association also contains stars of the Beta Tucanae group. Another notable member is DS Tucanae, which is a binary star, with the primary having one exoplanet transiting in front of the star.

Debris disks have been detected around some members. Examples are HD 1466, HD 10472, DK Ceti, CPD-74 192, HD 21997, HD 32195, HD 37484, HD 38206, V1358 Orionis and HD 85672. The star HD 202917 has a debris disk that was directly imaged with the Hubble Space Telescope. The brown dwarf 2MASS J02265658-5327032 is likely a member of the Tuc–Hor association and has a circumstellar disk, which is unusual for its age. Some researchers call these relatively old disks Peter Pan disks.

Examples of directly imaged planets in the association are 2MASS 0219-3925 b and 2MASS 0103(AB) b.

The list below shows some members of the group. The list is focused on B-type, A-type and F-type stars and other stars/brown dwarfs are included if they are notable. The list is sorted after the brightness. + List of membersNamedistance (light-years)spectral typebrightness (V-mag)α Pavonis179B2IV1.91φ Eridani154B8V3.56ε Hydri152B9IV4.12HD 2884135B9V4.36HD 24072172B9.5Van4.71HD 2885166A2V4.77η Tucanae154A1Va+n4.99HD 3003150A0V5.07HD 24071172A1Va5.25HD 20121139F4V+F9V6.01HD 154431181A5V6.07HD 19545177A3V6.18HD 12894151F4V6.45HD 207964152F0IV6.56HD 200798227A5/6IV/V6.70HD 30051220F2IV7.12HD 24636186F3IV/V7.13HD 207575153F6V7.22HD 1466140F8V7.45HD 53842189F5V7.46HD 20385159F6V7.49HD 13246149F7V7.50HD 17250186F7V7.88HD 32195205F7V8.12DS Tucanae149G6V8.49DK Ceti135G4V8.66HD 202917153G7V8.67BS Indi172G9V8.87CC Phoenicis130K1V9.38BO Microscopii218K3Ve9.45V857 Arae194G8V9.50AT Columbae254K1Ve9.58CT Tucanae144M0Ve11.47GJ 3054134M1.5V11.97AF Horologii142M2Ve12.132MASS 0103154M5.0+L15.402MASS 0219-3925131M6γ+L4γ11.32 (J-band)2MASS J02265658-5327032152L0δ15.40 (J-band)

Tucana–Horologium association

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