Beijing time on September 3, according tomedia reports, we have long been used to using the earth’s position relative to the sun, to distinguish the year-round. However, while the Earth’s journey around the sun is important to humans on Earth, it is insignificant compared to the epic week-long journey of the sun – and our entire solar system – around the center of the Milky Way.
Keith Hawkins, an assistant professor of astronomy at the University of Texas at Austin, said it takes about 220 million to 230 million Earth years for the sun to orbit the Milky Way — a week for the Earth to orbit the sun.
In other words, if we measure time by the Milky Way ‘clock’, our Earth exists only about 16 years (in Galactic or Cosmic years), and the Sun is only 20 years old, and even the entire universe exists for about 60 years.
The solar system’s process of orbiting the Milky Way is very similar to earth’s orbit around the sun. However, Hawkins explains that the solar system does not orbit a star, but a supermassive black hole at the center of the Milky Way. And this supermassive black hole has a huge gravitational force on all matter in the Milky Way.
“The sun’s speed is very fast — about 230 kilometers per second, or half a million miles per hour, and the sun keeps orbiting the center of the Milky Way” so it won’t be pulled toward the black hole, Hawkins said.
Our place in the Milky Way.
The Year of the Milky Way represents a larger unit of time than the Year of the Earth. But in the Milky Way, this unit of time is not uniform. We Earthlings call the Milky Way relative to Earth’s position in the Milky Way.
“We can say that a Milky Way year is about 220 million or 230 million Earth years. But on other planets in the Milky Way, their milky years are different,” Hawkins said.
The Milky Way is about 100,000 light-years in diameter, and our Earth is 28,000 light-years away from the center of the Milky Way. “If you think of the Milky Way as a city, then our planet is probably in a suburban location, ” Hawkins explains. If it’s a star with a orbit close to a “downtown” black hole, a Milky Way year is relatively short. But in the “suburbs”, where our solar system is located, “the Milky Way is a little bit older,” he said.
Similar rules apply to different planetary years. Mercury, for example, is the innerst planet in the solar system. Mercury orbits the sun for only 88 Earth days a week. Ueon, the seventh planet in the solar system, orbits the sun for a week for 84 Earth years. Pluto, a distant dwarf planet, has a orbital cycle of 248 Earth years.
Although the physical mechanisms of planetary orbits are similar to those that shape the solar system’s orbit around the Milky Way, one question is worth noting: How do astronomers calculate the length of the Milky Way? In fact, Hawkins says, this is a fairly basic science that was made clear in the early stages of modern astronomy.
“The main thing is to observe the movement of stars around the Milky Way, ” he said. ” “