What are the luminosity classes?
What are the luminosity classes?
Classification. Luminosity classes are labeled with Roman numerals from I to V: I are supergiant stars, II are bright giants, III are ordinary giants, IV are subgiants, and V are ordinary main sequence stars.
What are the classes of stars?
Harvard spectral classification
| Class | Effective temperature | Fraction of all main-sequence stars |
|---|---|---|
| B | 10,000–30,000 K | 0.13% |
| A | 7,500–10,000 K | 0.6% |
| F | 6,000–7,500 K | 3% |
| G | 5,200–6,000 K | 7.6% |
What is the Harvard spectral classification?
The Harvard Spectral Classification is based on the absorption lines (i.e. bark lines) in the stellar spectrum, that are sensitive to the stellar temperature, rather than to gravity or luminosity.
How did Angelo Secchi come up with the five Secchi classes?
Through analysis of this data, he discovered that the stars come in a limited number of distinct types and subtypes, which could be distinguished by their different spectral patterns. From this concept, he developed the first system of stellar classification: the five Secchi classes.
When did Angelo Secchi create the spectral classification?
During the 1860s and 1870s, pioneering stellar spectroscopist Father Angelo Secchi created the Secchi Spectral Classification in order to classify observed spectra. The classifications group stars into classes as follows: Class I: white and blue stars with broad heavy hydrogen lines, such as Vega and Altair.
How is the transparency of a Secchi disc determined?
Secchi disc readings do not carry the identity of the actual measure of transparency. The unbearable intense light of the sun fell on the water or one person saw the disk at a certain depth, but another person with good eyesight saw it at a greater depth. Secchi disc may vary in viewing ability.
When is the best time to measure the Secchi disc?
Secchi disc measurements should be taken from the shady side of the boat or dock from 9 a.m. to 3 p.m. Good results are available between 10 a.m. and 2 p.m. Secchi disc depth should be measured in the same manner every time by a person.