Evaluating the number of times the Sun has orbited the Milky Way

Sun’s Path Around the Milky Way. An illustration showing the path of the Sun, Earth and Moon around the Milky Way. The inclinations of the Ecliptic Plane and Celestial Equator are shown with respect to the Galactic North Pole and Galactic Plane. The inclination of the moon’s orbit is shown relative to the Ecliptic Plane. The Solar System traces out a sinusoidal path in its orbit around the galactic center. Using Galactic North as the initial frame of reference, the Earth and Sun rotate counterclockwise, and the Earth revolves in a counterclockwise direction around the Sun. However, the Sun and its satellites revolve CLOCKWISE around the Milky Way. Date 13 July 2017 Source Own work Author Jim slater307

Our solar system has been circling the heart of the Milky Way’s black hole for 4.6 billion years. However, determining the exact number of revolutions our sun has completed around the galaxy during this time is a challenging task.

It can be perplexing to grasp the notion that Earth is in constant motion through space. Yet, even more bewildering is the realization that we are simultaneously undertaking two journeys — orbiting the sun and traversing the Milky Way.

Similar to how the moon revolves around Earth and our planet orbits the sun, our sun also revolves around the Milky Way. To be precise, it orbits the supermassive black hole situated at the center of our galaxy. In actuality, the entire Milky Way is continually rotating around the heart of our galaxy’s black hole.

So, how many times has our solar system completed orbits around the colossal black hole at the center of the Milky Way? The answer isn’t as straightforward as one might assume.

In contrast to the predictable orbits of planets around the sun, the trajectory of our sun through the Milky Way is significantly longer and less stable, making it challenging to determine the number of revolutions around the galaxy’s center.

Utilizing basic mathematical calculations can offer insights into the duration it takes for the solar system to traverse our galaxy, thereby providing an estimate of the number of rotations our cosmic neighborhood has made. However, providing a precise answer remains elusive.

According to Space.com, the sun and the rest of the solar system are currently hurtling through our galaxy at approximately 448,000 mph (720,000 km/h). While this speed seems remarkable, certain stars within the Milky Way, known as hypervelocity stars, travel through the galaxy at speeds reaching up to 5.1 million mph (8.2 million km/h).

At its current velocity, it takes around 230 million years for our sun to complete a single orbit around the Milky Way. This duration exceeds the existence of dinosaurs on Earth and surpasses the lifespan of Homo sapiens by more than 750 times.

The sun, estimated to be around 4.6 billion years old, was joined by Earth approximately 100 million years later. In theory, if the sun’s orbital path had remained consistent throughout its existence, it would have completed approximately 20 orbits around our galaxy, with Earth accompanying it for roughly 98% of those revolutions.

However, the sun’s orbit has likely undergone significant alterations over time. Rather than maintaining a constant trajectory, our sun has likely undergone substantial movements since its formation.

Victor Debattista, an astrophysicist at the University of Central Lancashire, suggests that the sun’s original position differed from its current location. It is probable that our sun originated much closer to the center of the Milky Way.

Currently positioned approximately 26,100 light-years from the galaxy’s center, our sun’s chemical composition indicates that it was born roughly 16,300 light-years away from the galactic core. This outward migration, known as “radial migration,” involves stars being propelled along the spiral arms of galaxies like the Milky Way by the momentum generated by the rotating limbs — comparable to how a surfer navigates a wave.

During its formation, the sun’s orbital period was considerably shorter. Initially, it likely took approximately 125 million years for our star to complete a full orbit. As the sun migrated outward, its orbital period lengthened, a process that likely spanned billions of years.

Consequently, the sun has likely traversed the Milky Way more times than previously estimated, although the exact magnitude of these movements remains uncertain.

Radial migration is not unique to our sun; numerous other stars in the solar neighborhood are believed to have originated elsewhere and subsequently migrated outward. Moreover, the proportion of stars migrating outward increases with distance from the Milky Way’s center.

Presently, the sun is considered to be in a relatively stable orbit around our galaxy. However, there remains a possibility that it has not completed its outward migration entirely.

According to Debattista, it is plausible that the sun will continue its outward migration. Nonetheless, predicting the extent of this movement remains challenging.

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