What are galaxies in outer space?That is, what do those nouns in astronomy mean?

Honorable astronomers, and convenient for people to study them.

Categories: Science & Engineering.

Analysis: Human beings on the earth generally refer to objects outside the earth's atmosphere as celestial bodies. For example, the moon, seven planets other than the earth among the eight planets, the Kuansen sun, asteroids, comets, etc., are all celestial bodies that are closer to our earth.

Of course, there are man-made celestial bodies in the sky that are closest to us, artificial Qingqiaoxiang moons.

Galaxies are, of course, celestial bodies, and the largest celestial bodies that humans can currently observe. Many of the total galaxies that have been observed, such as those observed, are clusters of galaxies made up of thousands of galaxies like ours.

Countless how to make it clear, the solar system is only the smallest star system, there are many such systems outside the solar system, and then there are nebula systems, and there are star cluster systems composed of more than ten stars nearby, countless star systems star systems and countless nebula star clusters composed of large galaxy systems, just like we are in the small star system in the big galaxy Milky Way, there are more than 100 million large galaxies like the Milky Way in the universe, so we can't say that there are hundreds of millions of small galaxies.

In the universe, there are many galaxies beyond the solar system. There are many planets in the galaxy. It's a bare rock planet.

In fact, at first glance, you might mistake Mercury for the Moon. The closest planet to the Sun can reach temperatures of more than 400 degrees Celsius during the day when it is baked by the Sun. However, Mercury does not have a heat-trapping atmosphere, so the temperature drops to around minus 200 degrees Celsius at night.

As the smallest planet in the solar system, Mercury orbits the Sun in just 88 days, while Mercury has a day of nearly 59 days. Only two spacecraft have visited Mercury. The first was the Mariner 10, which passed in the mid-70s of the 20th century, and the second was the Courier, which arrived in 2011.

In April 2015, before scientists sent Mercury to the planet, Courier orbited Mercury more than 4,000 times. Of all the man-made and naturally occurring celestial bodies, Messenger is probably the only one orbiting Mercury.

<> it is too close to the Sun and the gravitational pull is too strong for the moon to form around Mercury and cannot be captured from elsewhere. The Sun's gravitational pull pulls Mercury three times every two revolutions. These Mercury missions provide details that are difficult to see from Earth, as Mercury is very tiny, even smaller than some of Jupiter's and Saturn's moons.

The most prominent feature on Mercury is the Caroli Basin, which was discovered by Mariner 10 during its flyby. It is an ancient crater and one of the largest in the solar system, with a diameter of more than 1,500 kilometers. Some say that this effect is like ringing a bell, sending shockwaves throughout Mercury.

The uneven terrain is where the shock wave moves outward 180 degrees from the point of impact. Like Venus, Mercury sometimes moves in front of the Sun, but the frequency of transits is much higher than that of Venus, with 13 to 14 transits in a century. On June 3, 2014, the Curiosity rover observed Mercury ghostly passing through the Sun from Mars, a transit that was not visible from Earth.

It is also the first time that a transit of Mercury or Venus has been observed from another planet. But 10,000 galaxies** cover only 12.7 million of the total area of the sky, so astronomers estimate that at least 7 trillion galaxies within the 46.5 billion light-year radius of the observable universe are isotropic, a number several times greater if the unobserved universe is taken into account. Carl Sagan once said, "There are more stars in the sky than there is sand on the earth", and now this sentence seems a bit conservative, because there are only 400 billion stars in the Milky Way, or even 1 trillion times the number of stars in the universe, so that even if the probability of habitable planets on the earth is more than 1 million, the number of earths in the universe is quite considerable with such a large base.

Among them, there are currently eight planets in the solar system, namely Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune. There are three main types of galaxies, elliptical galaxies, spiral galaxies, and irregular galaxies.

In the Milky Way, which is made up of stars, gas, and dust, the solar system is just a drop in the ocean. Until 100 years ago, people thought that our galaxy was the entire universe. No one thought that there was matter beyond the Milky Way.

We now know that there are 100 billion separate galaxies in the observable part of the universe alone. These galaxies vary widely in scale, from dwarf galaxies with a diameter of a few hundred light-years and millions of stars to giant galaxies spanning hundreds of thousands of light-years and containing trillions of stars. In addition to stars, galaxies also contain gas clouds, dust, and dark matter.

They are all gravitationally bound together. There are 5 types of galaxies: spiral galaxies, barred spiral galaxies, elliptical galaxies, lenticular galaxies, and irregular galaxies.

Astronomers mark objects based on their numbers in several celestial databases. For example, NGC 1530 represents galaxy number 1530 in the New General Catalog of Nebula Clusters (NGC) in the catalog database.

Quasars are extremely bright galaxies. At least some galaxies were quasars in their early years. Their energy comes from the matter that falls into the central massive black hole.

The image, taken by the Spitzer Space Telescope, shows a nearby spiral galaxy called M81. The detector records infrared radiation, not visible light. As a result, dust in the galaxy's core and spiral arms is evident in the image.

In a barred spiral galaxy like NGC1530, the spiral arms extend from the ends of the bar-like structure, rather than originating from the core as in spiral galaxies. This is evident in the image.

This state galaxy, nicknamed "Tadpole", is located hundreds of millions of light-years away. Like other galaxies, this large, rotating wheel of matter is held by gravity. In galaxy clusters, gravity can also tear galaxies apart.

The bands of stellar light that extend out of this galaxy are thought to be caused by the gravitational pull of a smaller passing galaxies.

No, the part of the universe that we observe is usually called a total galaxy. A total galaxy is a celestial hierarchy that is one level higher than a galaxy and may be smaller than, equal to, or larger than the part of the universe that can be observed.

The typical size of total galaxies is about 10 billion light-years and the age is on the order of 15 billion years. Through galaxy counting and microwave background radiation measurements, it is proved that the distribution of matter and motion in total galaxies is statistically homogeneous and isotropic, without any special position and orientation.

Dark matter and dark energy indicate their existence by their gravitational attraction on ordinary matter and the accelerated expansion of the universe, respectively. If dark energy were not present, then the gravitational pull between matter would slow down the expansion of the universe, but astronomical observations show that our universe is doing an accelerated expansion. The universe is made up of all celestial bodies.

Total galaxies are the general term for all the galaxies in our observable universe.

I don't know where the title came about, but I always felt that it wasn't a scientific concept. I don't know when this concept appeared, but I guess it was something that I made out because of laziness when we didn't understand the large-scale structure of galaxy groups, galaxy clusters, and the large-scale structure of the universe.

Maybe someone thinks: the Earth is in the solar system, the sun is in the Milky Way, and there are galaxies beyond the Milky Way, but is there a larger structure of the universe? What is the universe like?

At that time, the observation technology and observation level were insufficient, so I thought that all galaxies, including the Milky Way, should be integrated into a larger system structure, which should be called the total galaxy. Hence the word.

However, with the progress of theory, science and technology, and the improvement of the understanding of dark matter, dark energy, and the large-scale structure of the universe, the concept of total galaxies can no longer summarize the entire universe. It is now believed that the universe is the sum of all matter, energy, time, and space, and that the total galaxy alone can only explain the visible matter in the universe at most, and cannot summarize the constituent elements of the universe such as dark matter, dark energy, and time.

According to this, the total galaxy is not the universe.

Is it true that the total galaxy is the universe?

The total galaxy refers to the entire range of the universe that can be observed and detected by people with the existing means and methods of observation, and the universe is far from being observed, and we don't even know how big the universe is.

The universe encompasses everything, not just celestial bodies and celestial systems, or just a spatial sphere.

Therefore, the total galaxy cannot be equated with the universe.