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T-Associations are groups or clusters of very young stars that are very near to our Sun. Along with the O-Associations, these are the nearest groups of celestial objects. T-Associations are loose groups of T Tauri and RW Aurigae stars at distances from about 100 to 1000 parsecs from the Sun. There are about forty of these associations known, most with few then thirty members, although there may be as many as four hundred. T Associations have received much attention in recent years from astronomers due to the fact that T Tauri stars are closely associated with strong clouds of interstellar dust and are often observed near or within these dark nebulae. Armenian astronomer V. A. Ambartsumian sees in these compact associations of variable stars a special class of stars, possible in the condensing stage—young or very young stars. These T Tauri stars help to bridge the gap between protostars (newborn stars) and the younger stars. (T Tauri stars = age less than 107 The spherical shape of the T-Associations or clusters is an indication that these young stars will disband in a relatively short period of time. They are unstable.

The T Tauri stars exhibit erratic variations that may be, in part, extrinsic. They have luminosity comparable to our Sun, although their spectra are peculiar, with bright lines of hydrogen and the metals and continua of unusual energy distribution. These stars are strong emitters of infrared radiation.

Table of T-Associations

1. Zodiac Latitude Name
   T 00°Ar49’39 46°20’49|Phe T1-SY Phe (?)
   T 16°Ar55’06 60°49’02|Cep T3-DI Cep (?)
   T 18°Ar28’31 +46°11’53|And T1-BM And (?)
   T 25°Ar27’56 +72°56’37|Cep T1-NGC 7023
   T 27°Ar51’29 +56°23’36|Cas T2-NGC 7635
   T 08°Ta48’53 +52°45’13|Cas T1-VX Cas
   T 13°Ta26’01 +68°28’03|Cep T2-BO Cep (?)
   T 22°Ta39’28 +38°03’48|Per T1-EO Per
   T 29°Ta42’27 +11°46’47|Per T2-IC 348
   T 06°Ge14’51 6°47’57|Tau T1-RY Tau
   T 07°Ge47’56 – 3°06’36|Tau T2-T Tau
   T 09°Ge10’25 4°00’53|Tau T3-UZ Tau
   T 10°Ge08’19 +14°10’25|Per T3-NGC 1579
   T 15°Ge22’37 8°27’42|Aur T1-RW Aur
   T 21°Ge32’35 -11°39’14|Ori T1-CO Ori
   T 21°Ge35’23 -27°46’17|Ori T2-T Ori
   T 22°Ge56’16 -23°49’56|Ori T3-sigma Ori
   T 24°Ge35’34 -13°40’39|Ori T4-FU Ori
   T 26°Ge26’59 2°39’09|Tau T4-RR Tau
   T 09°Cn01’43 -13°14’53|Mon T1-NGC 2264, S Mon
   T 11°Cn09’09 – 9°42’52|Gem T1-FY Gem
   T 13°Cn05’34 -25°42’19|Mon T2-WX Mon (?)
   T 28°Cn11’07 -34°42’39|Pup T1-UY Pup (?)
   T 19°Li02’12 -58°14’13|Car T1-eta Car (?)
   T 25°Li12’46 -39°44’18|Cen T1-V 654 Cen
   T 07°Sa01’02 – 1°27’22|Sco T1? Sco
   T 29°Sa11’45 0°19’13|Sgr T1-NGC 6514
   T 29°Sa29’47 – 0°00’14|Sgr T2-NGC 6530
   T 00°Cp53’54 + 0°28’09|Sgr T3-S 188, IC 1274b
   T 03°Cp19’54 +11°03’44|Ser T1 NGC 6611
   T 06°Cp55’11 +56°52’12|Lyr T1 LT Lyr
   T 07°Cp37’01 +31°48’55|Oph T1 - V 426 Oph