# What is solar mass

(ORDO NEWS) — 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 the solar mass as their basic unit of mass. Since most things in space are big and heavy – like stars, galaxies and black holes – it makes sense to talk about such space objects in terms of solar masses, as opposed to much smaller units like the kilogram.

Speaking of objects in terms of solar masses also provides a more intuitive notion of an object’s mass relative to the Sun. Supermassive black hole at the center of the Milky Way galaxy, e.g. 7.956 x 10 30kg.

Such a huge number is much harder 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 too difficult a 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 the same distance from the Sun, our planet would have to spin faster or it would simply fall into 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 because 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 about 107,000 km/h, according to Cornell University, and the distance from the Earth to the Sun (called the astronomical unit) is 149,597,870 kilometers, according to the International Union of Astronomers.

In the late 1600s, Newton was calculating the relative masses of the sun and other planets. His calculations were mostly correct, although his values for the Earth’s relative weight were inaccurate. He found that the Sun is 169,282 times more massive than the Earth, when 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 apparent shift of the Sun in the sky observed in different points in the Earth’s orbit.

Today, instead of using parallax, astronomers can accurately measure the distances between objects in the solar system using radar. By measuring the time it takes for a satellite’s radar signal to bounce off another planet, astronomers can determine the distance to that planet.

But since the Sun does not have a solid surface, radar signals cannot be sent. So, in order to measure the Earth-Sun distance, astronomers must first measure the distances to another object, such as Venus. Then, by triangulation, they can calculate the distance to the Sun.

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

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