The Crab Nebula is the result of a supernova explosion of a star that occurred at a distance of about 1.84 kpc from Earth.If people first saw the explosion in a.d.1054,when did the explosion actually occur?
A) about a.d.1048
B) 786 b.c.
C) a.d. 1054, of course
D) about 4946 b.c.

Question

Quizplus · Accepted Answer

To calculate, we can use the formula: distance (in kiloparsecs) = (age of supernova in years) / (constant value)

The constant value is usually taken as 3.1 for the Crab Nebula.

So, distance = 1.84 kpc = (age of supernova) / 3.1

Age of supernova = 1.84 x 3.1 kpc = 5.71 kpc

To convert kpc to years, we multiply by 3.086 x 10^13 years/kpc (the value of 1 kiloparsec in years).

Age of supernova = 5.71 kpc x 3.086 x 10^13 years/kpc = 1.76 x 10^14 years

Subtracting the year of observation (1054 AD) from the age gives the answer:

Age of explosion = 1.76 x 10^14 years - 1054 years = 1.76 x 10^14 years BCE or about 4946 BCE.

Therefore, the answer is D (about 4946 BC).

The Crab Nebula Is the Result of a Supernova Explosion