Understanding the Solar System’s Journey around the Milky Way

KOMPAS.com – Humans are accustomed to calculating time by measuring the movement of the Earth relative to the sun.

The Earth’s journey around the sun is important for our lives, but don’t forget the epic journey that took the sun and the entire solar system around the center of the Milky Way.

The solar system surrounds the Milky Way

The solar system’s journey around the galaxy, in fact, resembles the Earth’s orbit around the sun.

However, according to Keith Hawkins, assistant professor of astronomy at the University of Texas, Austin, instead of orbiting a star, the sun actually circles a supermassive black hole located at the center of the Milky Way.

The black hole exerts enormous gravity on objects near the center of the galaxy, but it is the gravity exerted collectively by matter in the Milky Way itself that keeps the sun in its orbit.

Also read: What does the new galaxy JWST-ER1 discovered by the James Webb Telescope look like?

Orbiting the Milky Way galaxy once takes about 220 million to 230 million Earth years from the sun.

In other words, if time were calculated by this galactic “clock,” the Earth would be about 16 years old (in galactic or cosmic years), the sun would be formed about 20 years ago, and the universe would be about 60 years old.

Hawkins explained that the sun is moving at a speed of about 230 km per second so that it continues to rotate around the center of the galaxy in a circle, instead of being pulled towards the black hole.

Galactic year

Compared to the Earth year, the galactic year represents time on a large scale, but it is not a consistent measurement across the galaxy.

Thus, what Earthlings call a galactic year is specific to Earth’s position in the Milky Way galaxy.

Also read: How Long Does It Take to Travel from Earth to the Nearest Galaxy?

Hawkins added, we can say that one galactic year is 220 to 230 million years. However, other stars in the Milky Way have different galactic years.

The Milky Way is about 100,000 light years across and Earth is about 28,000 light years from its center. If you imagine the galaxy as a city, then Earth is on the outskirts of the city.

For stars orbiting close to a black hole or central “city,” a galactic year is relatively short.

In the “suburbs,” where our solar system is located, Hawkins said, galactic years are a little longer.

Similar rules control the variability of the length of a year between planets. For example, Mercury makes a complete orbit around the sun in about 88 Earth days. Uranus orbits the sun every 84 years, by Earth standards.

Also read: Where is the Andromeda Galaxy located?

Regarding how astronomers know the span of a galactic year, Hawkins said that actually quite basic knowledge became clear in the early days of modern astronomy.

According to Hawkins, these calculations are mostly about watching stars move around the galaxy.

Astronomers can watch stars move around the galaxy and infer from them the speed and direction of other stars.

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2023-10-09 05:00:00
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