Tranquil Star descended from Daffodils Dam through Lady Vivian (GB), who were from the Bruce Lowe family 20.

Tranquil Star was sold at Mackinnon and Cox's 1939 yearling sales and was purchased by the partners Messrs R. Cobden and T. G. Jones for 600 guineas.

[1] She was owned by T. G. Jones in partnership with Arthur Cobden and trained by Ron Cameron during her racing career.

[1] Tranquil Star won the Moonee Valley Quality Handicap, then defeated True Flight in the Caulfield Stakes, before winning the Caulfield Cup (carrying 8 stone 12 lbs and from a big field which included three horses who had won a Melbourne Cup, Colonus, Skipton, and Dark Felt), the W.S.

Cox Plate Tranquil Star became the first seven-year-old mare, and the only one of two to win this prestigious race at that age.

Her defeat in the Essendon Stakes was attributed by her trainer, Ron Cameron to the heat, as she had been beaten before under similar conditions.

She also scored 20 seconds and 12 thirds for a total of £26,690 in prize-money which made her Australasia's greatest stake-winning mare.

[1][7] Tranquil Star's last public appearance was before a large crowd on 24 March 1946 at Olympic Park, Victoria.

[8] Retired to stud Tranquil Star was a good brood mare that produced nine foals, of which seven were raced and three were winners.

Her progeny were: Calaway Gal was foaled by Calais Royale, a non-stud book mare whose 4th dam was Tranquil Star, but she proved she was a Thoroughbred by winning a Golden Slipper.

The registered Group 3 Melbourne Racing Club Tranquil Star Stakes, run over 1,400 metres, are named in her honour.