NGC2 17 1NGC celestial bodies
Discoverer: John Friedrich Wilhelm Herschel.
Date of discovery:1835 65438+February 65438+June.
Era J2000.0
Right ascension 5: 44: 13.8 seconds
Declination-70 40' 9
Open classification of star types in Trinary star system: NGC celestial bodies
NGC 1777NGC celestial bodies-discoverer: John Friedrich Wilhelm Herschel.
Discovery date:1836165438+1October1.
Other numbers: ESO33-SC 1
Era J2000.0
Right ascension 4 minutes 55 seconds 47.8 seconds
Declination -74 17' 8
Stellar galaxy
Magnitude 12.8
Blue is equal to 13.4 Magellanic Cloud, the two companion galaxies of the Milky Way. It is above the ground in the area south of 20 degrees north latitude. They are two cloud-like objects clearly visible to the naked eye near the Milky Way in the southern sky. The big one is in swordfish and mountain constellation, about 6, which is equivalent to 12 lunar apparent diameters; The small one in the rhododendron has an opening angle of about 2, which is equivalent to the apparent diameter of four moons; The two clouds are about 20 apart on the celestial sphere. The most famous celestial bodies in the southern hemisphere, except the rosy keyhole nebula and the shining Southern Cross, all belong to small magellanic cloud. These two celestial bodies are invisible in the latitude of Taiwan Province Province. They are the satellite galaxies of their own galaxy. Like M32 and NGC205 next to Cassiopeia, they are small galaxies next to big galaxies. /kloc-Arabs in the 0/0th century and Portuguese in the 0/5th century discovered barley clouds and wheat clouds long ago, but it was not until 152 1 that the Portuguese navigator Magellan accurately described them during his voyage around the world and later named them after Magellan. Short for barley cloud (LMC) and wheat cloud (SMC). LMC is 65,438+0.6 million light years away from the Earth, and SMC is 65,438+0.9 million light years away from the Earth. German amateur astronomers mistook LMC and SMC for two "clouds" in the sky when they came to Australia to watch the stars. Why can't the wind blow away? For a while, it was a joke. NGC 104 next to SMC is another good viewing target, and the Tarantula Nebula next to LMC should not be missed.
The name of the large Magellanic galaxy: LGMagellanic CCL.
Common name: large magellanic cloud.
Celestial body type: galaxy
Magnitude: 0.4
Size: 550.0'x 170.0'
Small Magellanic galaxy
Name of celestial body: NGC292
Common name: small magellanic cloud.
Celestial body type: galaxy
Magnitude: 2.2
Size: 319.1'x205.1'
radial velocity
Radial velocity of heliocentric measured by radio:175.0km/s.
Radio measurement error: 20.5km/s.
Optical measurement of the radial velocity of the sun center: 177.3 km/s.
Optical measurement error: 40.9 km/s.
Mean radial velocity of the sun center:175.5km/s.
Average measurement error:18.3km/s.
Consider the radial velocity of the local galaxy group: -6.5km/sec.
Considering the radial speed of GSR: 34.6 km/s.
The radial velocity of Virgo galaxy group is revised to -87.8 km/s.
Considering the radial velocity of 3K background radiation:113.7km/s.
Astrophysics distance module: 19.5 1 1.
Absolute B magnitude:-17.495438+0.65438+When the Arabs and Portuguese sailed south of the equator in the 20th century, they both noticed these two foggy celestial bodies in the southern sky, which were called "Cape of Good Hope Clouds". The Portuguese navigator Magellan described them accurately for the first time when he sailed around the world in 152 1 and later named them after his own surname. The Big Cloud is called the Large Magellanic Cloud, or Barley Cloud (LMC) for short. Xiaoyun is called Small Magellanic Cloud, which is short for Wheat Cumulus Cloud (SMC). Collectively known as the Magellanic Cloud.
19 12, American astronomer Loewit discovered the period-luminosity relationship between Maiyun's Cepheid Variables hertzsprung and shapley, and then measured the distance of Maiyun, becoming the earliest confirmed extragalactic galaxy. The distance of barley cloud is 654.38+0.6 million light years, and that of wheat cloud is 654.38+0.9 million light years. They are 50,000 light years apart in space. Wheat clouds belong to the nearest galaxy, which enables us to analyze their member celestial bodies carefully, so they are important astronomical observation objects and an important source of astrophysical data of galaxies. The Magellanic Cloud, like our Milky Way, also contains gas and stars. Barley Cloud is a dwarf or irregular galaxy with a mass of 1/20 that of the Milky Way. Maiyun belongs to an irregular galaxy or an irregular rod-spinning dwarf galaxy, and its mass is only1100 of that of the Milky Way. The Magellanic Cloud is rich in gas. The mass of neutral hydrogen accounts for 9% and 32% of their total mass respectively, which is much larger than that of the Milky Way. This shows that their evolution is not as high as that of the Milky Way. Their interstellar dust content is less than that in the Milky Way, and the young constellation I has many celestial bodies and a large number of high-luminosity O-B stars. In addition, new stars, supernova remnants, X-ray binaries and other celestial bodies have been observed. For example, a supernova (SN 1987A) in large magellanic cloud was discovered on February 23rd, 1987. Its maximum brightness is 250 million times that of the sun, and it is considered as the brightest supernova in 383 years. The Magellanic Cloud orbits the Milky Way once every/kloc-0.5 billion years. Every time we approach the Milky Way, its stars and gases will change under the gravitational force of the Milky Way. Small magellanic cloud has now been torn apart, and its star will become a part of the Milky Way. Large magellanic cloud will end up with the same fate.