• Q11. Sirius has an apparent magnitude of
about -1.5 and an absolute
magnitude of 1.4. Would you have to wait more than or less than 30 years for a radio signal to arrive from
Sirius?
a. Less than 30 years. b. More than 30 years.
•
•30
years matches light travel time for about 10 parsecs or 30 light years. If it were at 10 pc, then M would equal
m. If farther away than 30 light years would need to have an
absolute magnitude greater than the apparent magnitude, which it does.
•
• Question
12 (1 point) Hadar, at a distance of about 145 parsecs, has an absolute magnitude of -5.2. Which of the
following is most likely
Hadar's apparent magnitude?
a.-8.8
•b.-3.9
•c.0.6
•d.85.9
•m – M = -5 +5 log d = -5 + 5log 145
= -5 + 5(2.16)
•m = -5.2 +5.8 = 0.6
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