Mira

Mira (ο Cet / ο Ceti / Omicron Ceti) is a binary star in the constellation Cetus consisting of the red giant, Mira A or just Mira, and a white dwarf, Mira B or VZ Ceti. Mira A is also an oscillating variable star and was the first non-supernova variable star discovered, with the possible exception of Algol. Apart from the odd Eta Carinae, Mira is the brightest periodic variable in the sky that is not visible during part of its cycle.

Discovery

Mira was discovered (or at least noted as special for the first time) after a series of observations by the astronomer David Fabricius beginning on August 3, 1596. Observing the planet Mercury, he needed a reference star for comparing positions and picked a previously unremarked third-magnitude star nearby. By August 21, however, it had increased in brightness by one magnitude, then by October had faded from view. Fabricius assumed it was a nova — interesting enough — but then saw it again on February 16, 1609.

Related Topics:
David Fabricius - August 3 - 1596 - Mercury - August 21 - Magnitude - February 16 - 1609

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

Eventually, Johann Holwarda determined a period of the star's reappearances, eleven months; Johannes Hevelius was observing it at the same time and named it "Mira" (meaning "Wonderful") in 1662's Historiola Mirae Stellae, for it acted like no other known star in the sky. Ismail Bouillaud then nailed the period down to 333 days, less than one day off of the modern value of 332 days (and perfectly forgivable, as Mira is known to vary slightly in period, and may even be slowly changing over time).

Related Topics:
Johann Holwarda - Johannes Hevelius - 1662 - Ismail Bouillaud

~ ~ ~ ~ ~ ~ ~ ~ ~ ~

There is considerable speculation as to whether or not Mira had been observed prior to Fabricius. Certainly Algol's history (known for certain as a variable only in 1667, but with legends and such stretching back to antiquity showing that it had been observed with suspicion for millennia) suggested that Mira might have been known too. Karl Manitius, a translator of Hipparchus' Commentary on Aratus, has suggested that certain lines from that second century BC text may be about Mira. The other usual pre-telescopic Western suspects -- the catalogs of Ptolemy, al-Sufi, Ulugh Beg, and Tycho Brahe -- turn up no mentions, even as a regular star. There are three observations from Chinese and Korean archives, in 1596, 1070, and the same year when Hipparchus would have made his observation (134 BC) that are suggestive, but the Chinese practice of pinning down observations no more precisely than within a given Chinese constellation makes it difficult to be sure.

Related Topics:
Algol - 1667 - Hipparchus - Second century BC - Ptolemy - Al-Sufi - Ulugh Beg - Tycho Brahe - 1596 - 1070 - 134 BC - Chinese constellation

~ ~ ~ ~ ~ ~ ~ ~ ~ ~