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A Class A star is the third rarest and brightest type of main sequence star. They are typically colored white. They make up roughly 0.7% of main sequence stars.

A typical Class A star has a mass of 2 (1.6 to 2.9) solar masses, a radius of 1.7 (1.5 to 2.4) solar radii, a luminosity of 20 (6.5 to 54) solar luminosities, a surface temperature of 8500 K (7200 K to 9500 K), and a lifespan of way less than 1 billion years. A-type stars' core temperatures are no higher than 30,000,000°K (50,000,000°F).

They are hot, bright, and short-lived, which means that significant complex life is unlikely to develop around them. However, some simple life may have time to form in the habitable zone approximately 5 AU away from the parent star.

In about 300,000,000 - 700,000,000 years, the star's core hydrogen will exhaust. It will start burning helium, and start ballooning into a yellow giant, then into a red bright giant. The very unstable red bright giant, which has already lost almost 25% of its mass, will explode into a planetary nebula, leaving behind its former core, a white dwarf.

Properties

Properties of typical A-type main-sequence stars
Spectral type Mass Luminosity Temperature (Fahrenheit)
A0V 2.40 28.24 17,054
A1V 2.29 21.37 16,190
A2V 2.19 17.27 15,416
A3V 2.08 14.40 14,840
A4V 2.00 12.65 14,480
A5V 1.90 11.92 14,390
A6V 1.82 10.63 14,102
A7V 1.74 9.37 13,778
A8V 1.70 8.32 13,490
A9V 1.63 6.96 13,094

See Also

Stellar Classes
Φ · Ψ · Ω · Q · DE · GR · σ ς · Θ · N · D · BS · Y · T · L · M · C · S · QS · K · G · F · A · B · LBV · β · O · W · N · X · n0 · Exotic (Π · Σ · Γ · Δ · μ) · δ · I · TŻO · BL · ·
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