Questions about the milky way galaxy

Galaxy (Milky? Way) is the galaxy where the solar system is located. It is a disk-shaped star system consisting of more than 1 100 billion stars, thousands of clusters and nebulae, with a diameter of over 80,000 light years and a center thickness of over 6,000 light years. The solar system belongs to one of this huge galaxy, and the earth we live in belongs to a planet in the solar system. It used to be considered as a spiral galaxy, just like Andromeda, in the same galaxy cluster, but the latest research points out that the Milky Way is actually a bar galaxy. Spiral? Galaxy). Because it flows in the sky like a shining river, it was called Galaxy, Tianhe and Tianhan in ancient times. In the northern hemisphere, the Milky Way is most obvious in summer (in Scorpio and Sagittarius, it extends to the summer triangle and even Cassiopeia), and the Milky Way is very dim in winter (in Orion and Canis Canis). It is estimated that it consists of more than 1000 billion stars.

structure

Observing the spiral arm structure of the Milky Way in 2005, according to Haber's classification, it was found that the Milky Way is a huge rod-shaped spiral galaxy SBc (with loose spiral arms), with a total mass of about 600 billion to 3 trillion times that of the sun. [3][4],? There are about10 billion stars. [5]

Since 1980s, astronomers have always suspected that the Milky Way is a rod-shaped spiral galaxy, rather than an ordinary spiral galaxy. In 2005, the Spitzer Space Telescope confirmed this suspicion, and also confirmed that the rod-like structure of the galactic core was larger than expected. [6]

The disk diameter of the Milky Way is estimated to be 100000 light years, and the distance from the sun to the center of the Milky Way is about 26000 light years. The center of the disc protrudes outward.

The center of the Milky Way has a huge mass and a dense structure, so it is strongly suspected that there are supermassive black holes in it, because many galaxies are considered to have supermassive black holes in their cores.

Like many typical galaxies, the speed of celestial bodies orbiting the center of the Milky Way is not determined by the distance from the center and the distribution of the mass of the Milky Way. The typical speed of a star is between 210 and 240 kilometers per second after leaving the core bulge or at the periphery. [7] So the period of this star's orbit around the Milky Way is only related to the length of the orbit, which is different from the solar system. In the solar system, different distances have different orbital speeds.

The rod-like structure of the Milky Way is about 27,000 light years long and spans between the sun and the center of the Milky Way at an angle of 4410. It is mainly composed of red stars, which people think are ancient stars.

Each spiral arm of the observed and inferred spiral arm structure of galaxies is given a corresponding number (just like the spiral arms of all spiral galaxies), which can be roughly divided into 12 segments. It is believed that four main spiral arms originated from the core of the Milky Way. Their names are as follows: (refer to the right)

2? And then what? 8? -? 3kpc？ And then what? Perseus arm?

3? And then what? 7? -? Rectangular arm? And then what? Swan arm? With recently discovered extensions? -? 6)?

4? And then what? 10? -? Southern cross? And then what? Shield arm?

5? And then what? 9? -? Bottom arm? And then what? Sagittarius arm?

There are at least two small branches or branches, including:

1 1? -? Orion arm? (including the sun and the solar system? -? 12)?

Outside the main spiral arm is the outer ring or unicorn ring, which is the astronomer Brian Yanni? (Brian? Yanny) and then what? Handy Zhou newberg (Heidi? Joe. Newberg) proposed that it is a ring composed of stars around the outside of the Milky Way, including stars and gases born in the interaction with other galaxies billions of years ago.

The disk of the Milky Way galaxy is surrounded by a spherical silver halo with an estimated diameter of between 250,000 and 400,000 light years. [8].？ Because the gas and dust on the disk will absorb electromagnetic waves of some wavelengths, the composition and structure of the silver halo are still unclear. The disk (especially the spiral arm) is an active area for the birth of stars, but there is no such activity in the silver halo, and open clusters mainly appear on the disk.

Most of the mass of the Milky Way is dark matter, and the dark silver halo formed is estimated to be 600 billion to 3 trillion solar masses, which are gathered around the Milky Way. [4]

The new discovery has increased our understanding of the structure and dimensions of the Milky Way galaxy, which is more than what was obtained from the disk of Andromeda galaxy (M3 1) earlier. [9] Recently, newly discovered evidence confirmed that the outer ring was extended by the swan arm, which obviously supported the possibility of the silver plate extending outward. [ 10]? The discovery of Sagittarius dwarf ellipsoid galaxy and its debris in orbit around the silver pole show that it was torn apart in the interaction with the galaxy. Similarly, the Canis Canis dwarf galaxy also makes debris surround the Milky Way on the disk because of its interaction with the Milky Way.

June 9, 2006 65438+? Mario? Juric and some people at Princeton University announced that Si Long's digital sky survey found a huge cloud structure (spanning about 5,000 full moon areas) in the northern hemisphere sky, but it doesn't seem to be applicable to all current galaxy models. He concentrated some stars on the vertical line perpendicular to the disk where the spiral arm is located, which may be explained by the merger of Pettigrew and the Milky Way. This structure is located in the direction of Virgo, about 30 thousand light years away from us, and is temporarily called Virgo Star Jet.

May 9, 2006? Daniel? Zuk? And then what? Vasily? Belokurov announced that Si Long's digital survey had discovered two dwarf galaxies in Canis and Capricorn.

Neighbors of the milky way galaxy

NGC？ 733 1 is usually considered as the "twin brother of the Milky Way", which may be the case when we look back at our Milky Way from the outside. The Milky Way, Andromeda and Triangle Galaxy are the main galaxies in this cluster, which has about 50 galaxies, and this cluster is a part of virgo supercluster.

The Milky Way is surrounded by dwarf galaxies in some local galaxy groups, the largest of which is large magellanic cloud with a diameter of 265,438+0,000 light years, and the smallest is? The Carina dwarf galaxy, the Tianlong dwarf galaxy and the Lion dwarf galaxy are all only 500 light-years in diameter. Other galaxies around the Milky Way are the Small Magellanic Cloud, and the closest is the Canis dwarf galaxy, followed by the Sagittarius dwarf galaxy, the Ursa minor dwarf galaxy, the Yufu dwarf galaxy, the sextant dwarf galaxy, the celestial dwarf galaxy and the Lion I dwarf galaxy.

On June 5438+ 10, 2006, researchers reported that the disk of the Milky Way was found to be tilted for unknown reasons in the past, but now it is found to be ripples caused by the disturbance of large and small Magellanic clouds around the Milky Way. It is caused by vibrations of certain frequencies when they pass through the edge of galaxies. The mass of these two galaxies is about 2% of that of the Milky Way, which is considered insufficient to influence the Milky Way. But considering dark matter, the motion of these two galaxies is enough to affect larger galaxies. After adding dark matter, the impact on the Milky Way increased by 20 times. This calculation result is based on the computer model of Martin Weinberg of the University of Massachusetts at amherst. In his model, dark matter is distributed from the disk of the Milky Way to all known layers. Therefore, the model predicts that the influence of gravity will be amplified when the Magellanic Cloud passes through the Milky Way.

Observed and inferred galactic spiral arm structure