What is solar mass?

US, WASHINGTON (ORDO NEWS) — The solar mass is the mass of the sun. Or, more precisely, it is 1.989 x 10 30 kilograms – about 333,000 Earth masses.

Astronomers use solar mass as their primary unit of mass. Since most of the things in space are large and heavy – such as stars, galaxies and black holes – it makes sense to talk about such cosmic objects from the point of view of solar masses, in contrast to much smaller units, such as a kilogram.

Speaking of objects in terms of solar masses also provides a more intuitive concept of the mass of an object with respect to the sun. A supermassive black hole in the center of the Milky Way galaxy, for example, 7.956 x 10 30kg Such a huge amount is much more difficult to imagine than if you said that a black hole is as massive as 4 million suns.

Thanks to Sir Isaac Newton, calculating the mass of the sun is not a very difficult task. The mass of the sun also determines the strength of its gravity. And its gravity determines the orbital distance and speed of the planet Earth.

For example, if the Sun were more massive with a stronger gravitational pull, and if the Earth were at the same distance from the Sun, our planet would have to rotate faster or it would simply fall on the Sun. If the Sun were less massive with a weaker gravitational pull, the Earth would have to rotate more slowly or it would be ejected from the Solar system.

Newton calculated the mass of the sun, since we know the speed of the earth and the distance to the sun. Astronomers use basic geometry to calculate these two constants. The Earth revolves around the Sun at a speed of about 107,000 km / h, according to Cornell University, and the distance from the Earth to the Sun (called an astronomical unit) is 149,597,870 kilometers according to the International Union of Astronomers.

In the late 1600s, Newton calculated the relative masses of the Sun and other planets. His calculations were mostly correct, although his values ​​for the relative weight of the Earth were inaccurate. He found that the Sun is 169,282 times more massive than the Earth, while the exact value is 331,950. He miscalculated because his figures for the distance from the Earth to the Sun were based on inaccurate measurements of solar parallax, which is an obvious shift of the Sun in the sky, observed in different points of the Earth’s orbit.

Today, instead of parallax, astronomers can accurately measure distances between objects in the solar system using radar. By measuring the time it takes for a satellite’s radar signal to be reflected from another planet, astronomers can determine the distance to this planet. But since the sun does not have a solid surface, radar signals cannot be adjusted. So, in order to measure Earth-Sun distance, astronomers must first measure distances to another object, such as Venus. Then, by triangulation, they can calculate the distance to the Sun.

Connect this value and the measured speed of the Earth’s orbit to Newton’s equations, and using simple algebra you can calculate the mass of the Sun. Assuming that the circular Orbit (the Earth’s Orbit is close to a circle), M = (d / G) V 2where d is the distance to the Sun, v is the orbital velocity of the Earth, and G is the gravitational constant.


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