Spectral Standard Stars
| Stellar Class |
Mass (M☉) |
Radius (R☉) |
Mv | Teff (K) |
|---|---|---|---|---|
| A0V | 2.40 | 1.87 | 0.7 | 9,727 |
| A2V | 2.19 | 1.78 | 1.3 | 8,820 |
| A5V | 1.86 | 1.69 | 2.0 | 7,880 |
| A6V | 1.80 | 1.66 | 2.1 | 7,672 |
| A7V | 1.74 | 1.63 | 2.3 | 7,483 |
| A8V | 1.66 | 1.60 | 2.4 | 7,305 |
| A9V | 1.62 | 1.55 | 2.5 | 7,112 |
The revised Yerkes Atlas system listed a dense grid of A-type dwarf spectral standard stars, but not all of these have survived to this day as standards. The "anchor points" and "dagger standards" of the MK spectral classification system among the A-type main sequence dwarf stars, i.e. those standard stars that have remain unchanged over years and can be considered to define the system, are Vega (A0 V), gamma Ursae Majoris (A0 V), and Fomalhaut (A3 V). The seminal review of MK classification by Morgan & Keenan (1973) did not provide any dagger standards between types A3 V and F2 V. HD 23886 was suggested as an A5 V standard in 1978. Richard Gray & Robert Garrison provided the most recent contributions to the A dwarf spectral sequence in a pair of papers in 1987 and 1989. They list an assortment of fast- and slow-rotating A-type dwarf spectral standards, including HD 45320 (A1 V), HD 88955 (A2 V), 2 Hya (A7 V), 21 LMi (A7 V), and 44 Ceti (A9 V). Besides the MK standards provided in Morgan's papers and the Gray & Garrison papers, one also occasionally sees delta Leonis (A4 V) listed as a standard. There are no published A6 V and A8 V standard stars.
Read more about this topic: A-type Main Sequence Star
Famous quotes containing the words spectral, standard and/or stars:
“How does one kill fear, I wonder? How do you shoot a spectre through the heart, slash off its spectral head, take it by its spectral throat?”
—Joseph Conrad (1857–1924)
“I find it interesting that the meanest life, the poorest existence, is attributed to God’s will, but as human beings become more affluent, as their living standard and style begin to ascend the material scale, God descends the scale of responsibility at a commensurate speed.”
—Maya Angelou (b. 1928)
“The day in his hotness,
The strife with the palm;
The night in her silence,
The stars in their calm . . .”
—Matthew Arnold (1822–1888)