The vast majority of the electromagnetic radiation from the central stars is absorbed by surrounding dust, then emitted as Far infrared observations show a large mass of dust at 100–150 K, suggesting a total mass for the Homunculus of 20 All the high energy emission associated with Eta Carinae varies during the orbital cycle. The period between the Great Eruption and the smaller 1890 eruption was apparently 5.52 years, while before the Great Eruption it may have been lower still, possibly between 4.8 and 5.4 years.Perhaps the most valuable use of an accurate orbit for a binary star system is to directly calculate the masses of the stars. This requires the dimensions and inclination of the orbit to be accurately known. It does not currently lie on the S Doradus instability strip, although it is unclear what the temperature or spectral type of the underlying star actually is, and during its Great Eruption it was much cooler than a typical LBV outburst with a mid G spectral type.
Individual lines show widely varying Direct spectral observations did not begin until after the Great Eruption, but In the second half of the 20th century, much higher resolution visual spectra became available. This would result in a type Ib or type Ic supernova due to the lack of hydrogen and possibly helium. Observations with the As a 4th-magnitude star, Eta Carinae is comfortably visible to the naked eye in all but the most The earliest analyses of the star's spectrum are descriptions of visual observations from 1869, of prominent emission lines "C, D, b, F, and the principal green nitrogen line". The inclination has been modelled at 130–145 degrees, but the orbit is still not known accurately enough to provide the masses of the two components.A Great Eruption event similar to Eta Carinae A's has only been observed in one other star in the Milky Way—Eta Carinae A is not a typical LBV.
An O supergiant of 933,000 The size of Eta Carinae A is not even well defined. Its stellar wind is entirely opaque and appears as a pseudo-photosphere; this optically dense surface hides the true physical surface of the star. This supernova type is thought to be the originator of certain classes of gamma ray bursts, but models predict they occur only normally in less massive stars.Several unusual supernovae and impostors have been compared to Eta Carinae as examples of its possible fate. It becomes a Wolf–Rayet star on the Eta Carinae is a close binary and this complicates the evolution of both stars. Single massive stars spin down quickly due to braking from their strong winds, but there are hints that both Eta Carinae A and B are fast rotators, up to 90% of critical velocity. The rotation rate of the Eta Carinae stars cannot be measured directly because their surfaces cannot be seen. When hydrogen at the core is depleted after 2–2.5 million years, Models of the evolution and death of single very massive stars predict an increase in temperature during helium core burning, with the outer layers of the star being lost. Analysis to modern spectral standards suggests an early F The emission line spectrum associated with dense stellar winds has persisted ever since the late 19th century. The 1890 eruption may have been fairly typical of LBV eruptions, with an early F spectral type, and it has been estimated that the star may currently have an opaque stellar wind forming a pseudo-photosphere with a temperature of 9,000 K–10,000 K.Eta Carinae B is a massive luminous hot star, about which little else is known. Although the secondary star has never been directly observed, there is widespread agreement on models where it has a temperature between 37,000 K and 41,000 K.In all other directions on the other side of the wind-wind collision zone, there is the wind from Eta Carinae A, cooler and around 100 times denser than Eta Carinae B's wind. The line profiles are complex and variable, indicating a number of absorption and emission features at various The 5.5 year orbital cycle produces strong spectral changes at periastron that are known as spectroscopic events. Therefore, its future evolution is highly uncertain, but almost certainly involves further mass loss and an eventual supernova.Eta Carinae A would have begun life as an extremely hot star on the main sequence, already a highly luminous object over a million As core hydrogen burning progresses, a very massive star would slowly expand and become more luminous, becoming a blue hypergiant and eventually an LBV while still fusing hydrogen in the core.