Give some astronomical figures!

[Noun explanation] Commonly used astronomical terms

Absolute magnitude: The brightness of a star if it is placed at a distance of 32.6 light years from the Earth 10 parsec.

Absorption line: a dark spectral line formed after a certain band of light in the spectrum is absorbed by cold gas.

Accretion disk: a disk of matter that is attracted by a star or a black hole and eventually falls into a central star or a black hole.

Active galaxy: A galaxy with extremely high energy and a supermassive black hole at its center.

Height: the distance of a celestial body from the horizon measured in angle.

Arc minute: 1 degree 1/60 is called 1 arc minute. 1 arc is divided into 60 arc seconds.

Constellation: A group of distinct stars, such as the Big Dipper, forming part of a constellation.

Asteroid: a small stone object orbiting the sun, mainly between the orbits of Mars and Jupiter.

Astronomical unit: the unit for measuring distance, with the symbol AU, which stipulates that the distance between the sun and the earth is one astronomical unit, that is, 93 million miles (65.438+0.5 billion kilometers).

Azimuth: The celestial distance measured eastward along the horizon from the North Pole.

Big Bang Theory: This theory holds that the expansion of the universe began at a small point 654.38+0.5 billion years ago.

Binary star: Two stars orbiting each other.

Black hole: It is a very dense celestial body, and light cannot escape its gravitational effect.

CCD: charging lotus root device. Silicon wafers convert light into electricity and then form images.

Celestial equator: the projection of the earth's equator on the celestial sphere.

Celestial pole: the projection of the earth's south pole and north pole on the celestial sphere.

Celestial sphere: it is an imaginary hollow sphere to defend the earth, and stars seem to be embedded in this sphere.

Cepheid variable star: this is a variable star, represented by Cepheus triangle star, whose brightness fluctuates. The brighter the Cepheid variable, the slower its pulse.

Chandraseka: This is the mass limit that the stellar core cannot maintain the white dwarf. When the mass of a star exceeds 1.4 times that of the sun, it will become a neutron star or a black hole.

Chromosphere: A layer in the atmosphere of a star, surrounded by the photosphere.

Cirumpolar star: a star that never sets around the celestial pole in the view of an observer at a certain latitude.

Closed universe: refers to the universe in which mass generates enough gravity to resist its expansion and eventually collapse.

Collimation: Calibrating the lens or mirror of a telescope.

Synapsis: Two celestial bodies are in a straight line with the observer's line of sight.

Constellation: People have identified 88 images composed of stars in the sky. Each image is called a constellation, and now it also refers to the sky area delineated by these constellations.

Corona: the outermost layer of a star's atmosphere.

Dark matter: invisible and non-radioactive matter, accounting for 90% of the universe. They are invisible, but their existence can be inferred from their gravitational effects on galaxies and clusters of galaxies.

Declination: The distance from the celestial body to the equator, in degrees.

Binary star: two stars orbiting each other, or two stars that are actually unrelated but in the same line of sight. The latter is an optical binary star.

Dwarf: a main sequence star like the sun. If it is a white dwarf, it is the remnant of a star like the sun. Brown dwarfs don't have enough matter to melt.

Eclipse: The shadow of one celestial body passing by another. An eclipse occurs when the moon blocks the sun and forms a shadow on the earth. An eclipse occurs when the moon passes through the shadow of the earth.

Zodiac: the projection of the planetary orbital plane on the celestial sphere. It is also the annual orbit of the sun in the sky.

Electromagnetic spectrum: all spectral lines of electromagnetic radiation, from long-wavelength radio waves to short-wavelength gamma rays.

Elongation: the distance from the planet to the sun, measured in degrees, can be measured from the east or the west.

Emission line: a bright spectral line formed by waves of a specific wavelength emitted by hot gas.

Emission net: A luminous cloud composed of interstellar gas.

Event horizon: The matter around the black hole has an irreversible boundary, and no events can be observed outside the boundary.

Flat universe: The universe has enough matter to slow its expansion without collapsing.

Galactic disk: A flat disk of stars, dust and gas in spiral galaxies.

Galactic halo: A huge spherical region surrounding a galaxy, consisting of old stars and globular clusters.

Galaxy: A huge group of stars combined by gravity, which can be divided into irregular galaxies, elliptical galaxies, rod-spiral galaxies and regular spiral galaxies.

Globular cluster: an ancient globular cluster consisting of clusters of stars in the orbit of galaxies, which can contain up to 6,543,800 stars.

Gravitational lens: Radiation emitted from a distant radiation source is bent under the action of a gravitational field of a certain mass, such as a galaxy.

Inflation era theory: this is a theory about the initial state of the big bang theory, which holds that there is a driving force in the initial vacuum to push the universe to expand at superluminal speed.

Interferometry: combining light or radio waves from the same celestial body with multiple telescopes to increase decomposition.

Kelvin: A temperature scale based on absolute zero, namely-273,438+05 degrees Celsius, at which molecules stop moving. (0℃ =273. 15K)

Kuiper Belt: A circular disk composed of icy objects outside Pluto's orbit, located in the Oort cloud, is a gathering place for short-period comets.

Light-year: The distance that light travels in a year is equal to 6 trillion miles (947 million kilometers).

Local galaxy group: A group of galaxies linked by gravity consisting of about 30 local galaxy groups, in which our Milky Way is located.

Magnitude: the brightness of a celestial body. Every time the magnitude decreases, the brightness increases by 2.5 1 times of the previous magnitude.

Main sequence: The main part of a star's life cycle, during which it uses hydrogen as its main fuel.

Meridian: an imaginary line connecting due south and due north through the zenith.

Messier catalog: A catalog of 1 10 bright celestial bodies, including clusters, nebulae and galaxies.

Nebula: an interstellar cloud of dust and gas.

Netutron star: a massive star with a diameter of about 20 miles (32 kilometers) in the late evolution. It is very dense, and protons and electrons in it combine to form neutrons.

NGC: A new catalog of nebula clusters, including 840 clusters, nebulae and galaxies.

Nova: A star gets gas from its companion star and suddenly burns and glows.

Occlusion: A celestial body, such as a star, is hidden by another celestial body, such as the moon.

Oort Cloud: A huge spherical cloud surrounded by icy materials outside the solar system, which is the repository of long-period comets.

Open cluster: A loose cluster of young stars.

Open Universe: If the mass of a universe is not large and gravity is not enough to slow down its expansion, this is the so-called open universe.

The point on a planet's orbit that passes through the sun and is opposite to the earth.

Parallax (parsec): The displacement of celestial bodies on distant background observed from different angles.

Parsec: It means distance. At this distance, the distance from the sun to the earth is exactly 1 sec.

Photosphere: The visible surface of a star.

Planetary Nebula: A gas shell that explodes before a red giant becomes a white dwarf.

Precession: The earth's rotation swings with a period of 25,800 years, which causes the coordinates of the celestial pole and the celestial sphere to move, which is called precession.

Prominence: Magnetic solar material that erupts from the surface of the sun.

Self-motion: Observing the apparent motion of stars on the celestial background from the earth.

Pulsar: A rotating neutron star. When the beam determined by its strong magnetic field sweeps across the earth, it will cause radio waves with pulse characteristics.

Quasar: A celestial body resembling a star. Active galaxies are in a very high energy stage at the initial stage of formation, which is characterized by very strong radiation.

Radio galaxy: An active elliptical galaxy whose radiation is mainly radio waves.

Red shift: the spectral line moves to the red end of the spectrum. This is because the celestial bodies move away from the earth, which lengthens the wavelength of electromagnetic waves.

Retrograde: the normal motion of the planet is from west to east, and the opposite apparent motion is called retrograde, which is determined by the relative motion of the planet and the earth.

Right ascension: A line on the celestial sphere corresponding to the meridian of the earth, passing through the poles of the celestial sphere and perpendicular to the equator of the celestial sphere. It is expressed in hours, minutes and seconds, and it increases from west to east from 0: 00 to 24 hours.

Seyfert galaxy: A galaxy with intense nuclear activity, with a black hole in its core, which may be the late evolution of quasars.

Stellar time: a time system based on the true rotation of the earth, that is, from the time when the star rises to the time when the star rises again (23: 56: 4).

Singularity: Infinitely dense point in the center of a black hole.

Solar wind: A stream of subatomic particles with dots emitted by the sun.

Space-time: the unified four-dimensional universe (three-dimensional space and one-dimensional time) is bent by the influence of mass.

Spectral type: according to the temperature and color of stars, stars are divided into O, B, A, F, G, K and M types: hot blue stars, and M types: cold red stars.

Sunspot: It is a relatively cold dark area on the surface of the sun, and the magnetic field can penetrate the surface of the sun.

Supercluster: A huge galaxy cluster composed of thousands of galaxies connected by gravity.

Superstar: A huge explosion of the star itself.

Variable star: a star whose brightness changes, possibly due to its own or external influence.

Zodiac: a strip on the celestial sphere extending 9 degrees north and south along the ecliptic. There are zodiac signs on the ecliptic, and the sun, moon and planets except Pluto all run on the ecliptic.