What's special about our Milky Way?

The Milky Way contains the Solar System and the planet Earth within it. The Milky Way is very special to us, but considering the whole universe, it is just a normal spiral galaxy like billions of other spiral galaxies.

On beautiful evenings, look up at the starry sky and you will see a strip of light across the sky. In the past, people in different cultures described this strip of light with many interesting images, such as rivers, milk lines, walkways, halls, .

Since the Earth was formed, that strip of light has shone brightly in the sky and so it was one of the first things that people admired. In fact, that is the region - the galaxy that holds us, when viewed from our position, is its outer spiral arm.

The Milky Way strip across the sky of Mangaia island paradise in the South Pacific.This image was chosen as the best work at the Astronomical Photography Competition organized by the British National Maritime Museum in 2011. (Photo: Tunc Tezel).

Understanding the structure of the Milky Way is a difficult challenge and has been done for a long time. Our Solar System is located on an area near the outer edge of the Milky Way disc, so we never looked through the heart of the Milky Way to observe the other side of the galaxy disk.

The Milky Way is a spiral galaxy, spanning about 100,000 light-years. If you can see it from above, you'll see the center bulge out and there are four large spiral arms around. Spiral galaxies are very popular, making up two-thirds of all galaxies in the universe.

Unlike ordinary spiral galaxies, bar-shaped spiral galaxies (or spiral-shaped spiral galaxies) have a barrier-like region that runs across its center, and it has two main spiral arms. . So did the Milky Way and had two smaller spiral arms. One of the two small arms is the Orion Spiral Arm, which contains the Solar System, which sits between two large arms, Perseus and Sagittarius.

The panoramic image of, a nearby galaxy and looks like our Milky Way with spiral arms.(Photo: ESO).

The Milky Way does not stand still, but it always revolves around its core. Helical arms are always moving in space, the Sun and planets also move with them. Our solar system travels at 828,000 km / hr, but even with this tremendous speed, it takes us 230 million years to complete a spin around the Milky Way core.

The spiral arms make dust and stars and planets move slowly together, when matter reaches dense areas of material in spiral arms, it will compress together to create areas with a high density of material, and promote the process of forming new stars.

Our Milky Way galaxy is surrounded by a giant halo of glowing hot gas that lasts hundreds of light years. Although it is just a halo of gas, it is estimated that it has the same weight as all the stars in the Milky Way. Like the Milky Way, this gas halo moves very quickly.

The spiral arms always revolve around the Milky Way core, each of which has a huge amount of dust and gas, the newly formed star here and there. These spiral arms form a disk of galactic matter, which is about 1,000 light-years across.

The wide-angle image shows the central area of ​​the Milky Way, the bulge area, when viewed from Earth.The area marked with the red box in the picture is the view through infrared light wavelength by VISTA glass.Photo: ESO / Nick Risinger (skysurvey.org).

In the center of the Milky Way is the bulge. Ngan Ha's core is crammed with gas, dust and stars. The number of stars in the Milky Way accounts for a very small percentage, because most of them are concentrated in this bulge. Dust, gas and why this place is so thick that you can't see the core of the Milky Way, let alone see through the other side.

Located in the center of the Milky Way is one, which is billions of times more massive than the Sun. This supermassive black hole may have started to shrink gradually, but its excess gas and dust still allow it to grow even bigger.

Black holes are gluttonous monsters, they swallow everything around it. Although black holes cannot be observed directly, scientists still see its gravitational influence when it distorts and changes the paths of surrounding objects. Most galaxies have large black holes in the center.

A computer simulation graphic shows the merger between the Milky Way and the Andromeda galaxy for several billion years when viewed from the sky of Earth.(Photo: NASA, ESA, Z. Levay and R. van der Marel (STScI), and A. Mellinger).

Quick information about the Milky Way:

• The Milky Way contains more than 200 billion stars, and enough excess dust to create billions more stars.
• The Solar System lies 30,000 light-years away from the center of the Milky Way, and lies 20 light-years away, above the plane of the Milky Way. The Earth and the planets do not move parallel to the Milky Way plane, but tilt at an angle of about 63 degrees.
• More than half of the stars found in the Milky Way are older than the Sun at 4.5 billion years old. Our Milky Way galaxies have gone through the "population boom" process when new stars were created continuously 10 billion years ago.
• The most common type of star in the Milky Way is a red dwarf, which is less hot and one-tenth of the mass of the Sun. Previously, we still thought that such stars would not own planets that could survive life, but now they become the most valuable candidates for alien hunting.
• In the late 1920s, astronomers all thought that all the stars in the universe were in the Milky Way. Until Edwin Hubble discovered a special star called the Cepheid variable star , it allowed him to accurately measure the distance from Earth to it, and astronomers at the time realized that out there there are separate galaxies.
• NASA recently chose to carry out the mission of the Galaxy Terahertz Spectroscopy / Galactic Observatory (GUSTO), bringing a telescope up high by a balloon to map the Milky Way and the Galaxy Large nearby. This mission will be started in 2021 from McMurdo, Antarctica and hovering in the air for 100 to 170 days depending on the weather.

This is the Milky Way in the southern hemisphere sky, many bright stars and celestial bodies are more interesting than watching the Milky Way in the northern hemisphere.The Covered Nebula is a dark space in the middle of the light band.Alpha Centauri stars (the closest star to the Solar System, 4.3 light-years away) and Beta Centauri star just to the left of the Charcoal Nebula, while the famous Crux (Southern Cross) is to the right of the Charcoal Nebula.The image was taken on April 6, 1986 in La Serena, Chile.(Photo: Joe Rao).