A unique feature of the Homunculus is the ability to measure the spectrum of the central object at different latitudes by the reflected spectrum from different portions of the lobes. These clearly show a polar wind where the stellar wind is faster and stronger at high latitudes thought to be due to rapid rotation causing gravity brightening towards the poles. In contrast the spectrum shows a higher excitation temperature closer to the equatorial plane. By implication the outer envelope of η Carinae A is not strongly convective as that would prevent the gravity darkening. The current axis of rotation of the star does not appear to exactly match the alignment of the Homunculus. This may be due to interaction with η Carinae B which also modifies the observed stellar winds.
A unique feat.ure of the Homunculus is the ability to measure the spectrum of the central object at different latitudes by the reflected spectrum from different portions of the lobes. These clearly show a polar wind where the stellar wind is faster and stronger at high latitudes thought to be due to rapid rotation causing gravity brightening towards the poles In contrast the spectrum shows a higher excitation temperature closer to the equatorial plane. By implication the outer envelope of η Carinae A is not strongly convective as that would prevent the gravity darkening. The current axis of rotation of the star does not appear to exactly match the alignment of the Homunculus. This may be due to interaction with η Carinae B which also modifies the observed stellar winds.