2. Which star is hotter, Aldebaran or SiriusB? Aldebaran SiriusB There is not en

Question

2.Which star is hotter, Aldebaran or SiriusB?

Aldebaran

SiriusB

There is not enough information to tell

Aldebaran

SiriusB

There is not enough information to tell

Copyright© The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Spectral Class F G 10° 105X 104-Acrux.)rWxxxxx x ue gignts,x Betelgeuse RigelxYellow Yellow x × xgiants Antares Deneb Antares× Red giants .giants anopUS AcherndMainex,xxPolans 10 Polaris Mainkx x xxxxx xx . Aldebarän × 102 Arcturus Vega Sirius A AltairCapella 10 Procyon A a Centauri A Sun ,0 Centauri B 0.1 61 Cygni A 61 Cygni B Gliese 876 0.01

Explanation / Answer

Luminosity of the star altair L = 10Lo

Lo – Luminosity of sun = 3.846 x 1026 W

L = L­o (M/Mo)3/2

10 = (M/Mo)3/2

100 = (M/Mo)3

M = 4.64 Mo

= 4.64 x 1.989 × 1030 kg

= 9.23 x 1030kg

= 1010 / (M/Mo)5/2

T = 1010 / 4.645/2

T = 0.0217 x 1010 years

T = 2.17E8 years

Or 0.217 billion years

Siruis B is hotter since it’s surface temperature is little more than 20,000 K while the surface temperature of aldebaran is only around 4000 K

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