Sdor S Doradus 2 stars

- These are eruptive, high-luminosity Bpec-Fpec stars showing irregular, sometimes cyclic, light changes with amplitudes in the range jm-7"' in V. They belong to the brightest blue stars of their parent galaxies. As a rule, these stars are connected with diffuse nebulae and surrounded by expanding envelopes. GCVS

The S Dor stars, occasionally called Hubble-Sandage stars and luminous blue variables, are a relatively new entry to the General Catalog of Variable Stars. They were officially recognized on 31 March 2000, when described within IBVS 4870, The 75,h Name List of Variable Stars although their eruptions have been known, and observed, for centuries. Probably the best known S Doradus star is i] (Eta) Carinae, visible from the southern hemisphere.

Between the years 1600 and 1800, astronomers occasionally noticed ri Carinae as either a second- or fourth-magnitude star. It apparently varied in brightness, fluctuating between these two limits, until the late 1830s, when it became one of the brightest stars in the sky, remaining so for nearly 20 years. John Herschel called it "fitfully variable" and described its "sudden flashes and relapses" as it varied in brightness between magnitude +1 and -1. i] Carinae eventually faded to eighth magnitude as the eruption ended and a circumstellar dust cloud formed. Today, i] Carina teeters on the edge of catastrophic collapse and is watched carefully by astronomers from around the world.

Observation Key

Faint stars -V1 Mixed amplitudes ^ Fast outbursts <3> Visual, CCD/PEP

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