Herbig stars Ae / Be are young stars belonging to spectral types A and B, which have not yet entered the main sequence. They are enveloped in clouds of gas and dust and may be surrounded by a circumstellar disk. They have a mass between 2 and 8 solar masses and are still in the phase of star formation (gravitational contraction), approaching the main sequence, but without the fusion of hydrogen in its nucleus. Its name is due to the astronomer George Herbig, who in 1960 distinguished this type of stars from the rest. characteristics
The criteria for distinguishing Herbig Ae / Be stars are:
Occasionally, Herbig Ae / Be stars show significant changes in their brightness. It is thought that it is due to the existence of lumps (protoplanetas or planetesimals) in the circumstellar disk.
Objects similar to stars Herbig Ae / Be but with a smaller mass (less than 2 solar masses) are the aforementioned T Tauri stars, which correspond to spectral stars F, G, K and M that have not yet entered in the main sequence. No similar objects with mass greater than 8 solar masses have been observed, since they evolve very quickly: when they are visible, the fusion of hydrogen in the nucleus already occurs and they are, therefore, stars of the main sequence.
51 Ophiuchi, AB Aurigae, UX Orionis, V700 Monocerotis and V856 Scorpii are some of the best known stars of this class.
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