320 gånger tyngre än solen och dubbelt så tung som någon annan hittills känd himlakropp säger vetenskapsmän som på sitt speciella sätt vägde R135a1 i onsdags.
En massa om massan:
The Question
(Submitted June 09, 1997)
I wish to know how we go about calculating the mass of our Sun and other stars. Are there other ways to measure bodies in space rather than by gravitational means? Do we estimate the mass of our Sun by measuring it against the combined mass of all the planets in our solar system? I'm interested in the equations and procedures.
The Answer
You've asked about one of the fundamental issues in astronomy, namely determining the mass of objects such as the Sun and other stars.
The short answer is that there is no other way to *directly* measure the mass of the Sun or any other star than by observing the gravitational effects of one object on another.
You can estimate the mass of the Sun one of two ways.
Both use Newton's Laws of motion.
The first way uses Newton's revision of Kepler's third law, which states that the period squared or any body orbiting the Sun is proportional to its average distance from the Sun cubed. Newton generalized this for all gravitating systems. In the case of the Sun, the equation we can use is:
Mass_of_Sun=((4*pi2)/G) (a3/P2), where pi=3.14159, G is a fundamental constant, a is the radius of the Earth's orbit about the Sun, and P is the orbital period of the Earth about the Sun.
Another method uses Newton's second law and gravitation. In this case, one starts with F=m*a (where F is the force on an object, m is the mass of the object and a is the acceleration of the object due to the force). Since the gravitational force can be expressed as
F = G(MSun)(Mearth)/(R2) where MSun and Mearth are the masses of the Sun and Earth, and R is the distance between the two, and the acceleration for a circular orbit is equal to the velocity2/R, Newton's second law can be rewritten in this case to give
Mass_of_Sun=velocity2*R/G
In both cases, putting in the values for Earth's orbital velocity, distance from Sun and the value for G gives a value of about 2 x 1030 kg for the mass of the Sun. (That's 2 with 30 zeroes after it.)
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Regards,
Padi Boyd
for the Ask an Astrophysicist
Här (ESO:s hemsida) finns den bästa och mest informativa informationen på svenska om R136a1:
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