What is Extragalactic Astronomy?

The branch of astronomy that takes galaxies and intergalactic space as research objects. The research object is galaxies other than our galaxy (researching all celestial bodies that do not belong to galaxy astronomy), also known as extragalactic astronomy. Its mission is to explore the structure, movement, origin, and evolution of galaxies, the spatial structure, interactions, and evolutionary relationships of galaxy pairs, galaxy groups, and galaxy clusters, the phenomenon of galaxy clustering, and the distribution of matter on a larger scale. Galaxy astronomy is the basis of modern cosmology.

Galaxy astronomy

Published in 1888

With medium-aperture optical telescopes, you can observe the galaxy disks, spiral arms, galaxy nuclei, galaxy halos, and galaxy crowns of some members of the local galaxy group (such as the Large Magellanic Cloud and the Fairy Galaxies), and observe the celestial bodies of their members , Ionized hydrogen region, planetary nebula, supergiant, red giant, nova, Cepheid variable) for photometric measurement and spectral analysis. However, with the exception of a few close-range galaxies, most galaxies appear to be faint small-area light sources due to their long distances, which are even as small as point sources. To obtain their optical observation data, large-aperture telescopes and high-efficiency radiation receiving devices must be used, and deep-space exploration of 10 billion light-years must be equipped with high-power wide-angle equipment. To master the radio astronomical maps of astronomical objects outside the river, you must have a large radio antenna and radio resolution technology that is commensurate with optical imaging. The non-thermal radiation and high-energy processes of the extragalactic galaxy world are attracting large-scale radio equipment and space detection devices around the world. Contemporary powerful telescopes in various wave bands have taken extragalactic celestial bodies as important observation objects in order to achieve greater progress and breakthroughs in this regard. The main research methods of galaxy astronomy are astrophysics method and radio astronomy method. In addition, galaxy dynamics and statistical astronomy are also important research tools.

Galaxy astronomy size

Elliptical galaxies vary widely in size, with diameters ranging from more than 3300 light years to 490,000 light years; spiral galaxies typically have diameters between 16,000 light years and 160,000 light years; irregular galaxies are generally between 6500 light years and Between 29,000 light years. Of course, since the brightness of galaxies always fades from the center to the edges, and there are no obvious boundaries on the outer edges, the results measured by different methods are often different.

Galaxy astronomy

Galaxy astronomy quality

The mass of galaxies is generally between 1 million and 100 billion times the mass of the sun. The masses of elliptical galaxies are very different, with a difference in mass of up to 100 million times. In contrast, spiral galaxies are centered and irregular galaxies are generally smaller.

Galaxy astronomy movement

The stars in the galaxy are moving, the galaxy itself also rotates, and the galaxy as a whole is also moving in space. The galaxy's redshift phenomenon The galaxy's redshift phenomenon is the displacement of a spectral line toward the red end in the galaxy's spectral observation. Why is there such a displacement? What does this displacement phenomenon mean? According to the Doppler effect in physics, the red shift indicates that the observed celestial body is moving away from us in the direction of the line of sight in space. In 1929, Hubble discovered that the galaxy's redshift is proportional to the distance of the galaxy from us. The longer the distance, the greater the amount of redshift. This relationship is called Hubble's Law. This is the measured basis of the Big Bang cosmology.

Galaxy Astronomy Distribution

The overall distribution of galaxies in cosmic space is the same in all directions and is nearly uniform. However, on a small scale, the galaxy's distribution is uneven. Like the distribution of stars, there is a tendency to cluster. The Large Magellanic Cloud and the Small Magellanic Cloud form a dual galaxy. They form a triple galaxy with the Milky Way. Together with the Andromeda galaxy, the galaxy group is formed.

Galaxy astronomy evolution

As a huge celestial system, galaxies also have an evolutionary process from formation to development and decay. From the morphological sequence of galaxies, there are elliptical galaxies, spiral galaxies and irregular galaxies. Does this morphological difference represent a difference in their evolutionary stages? Who is young? Who is middle-aged? Who is old? These issues are still inconclusive and are still being explored. Elliptical galaxy: The shape is a perfect circle or ellipse, with a bright center and darkening edges. According to the shape, it is divided into eight subtypes E0 to E7. E0 oval galaxy One type of core is not spherical, but rod-shaped. Spiral arms emerge from both ends of the rod, and are called rod spiral galaxies. The Sc-type spiral galaxy Andromeda Nebula is an Sb-type spiral galaxy. The Sb-type spiral galaxy is an SBb-type spiral galaxy. Regular shape. In addition to the above Hubble classification, the irregular galaxies of the large Magellanic Cloud and the Magellanic Cloud also have special galaxies. The special galaxies mainly show obvious galaxy nucleus activity.