Constellation expansion of triangle

Right ascension 0 1:33.9 (hours: minutes)

Declination +30:39 (degrees: minutes)

Distance 3000 (thousand light years)

Apparent brightness 5.7 (magnitude)

Apparent size 73x45 (angular minutes)

It may have been discovered by Hodierna before 1654. 1764 was independently rediscovered by CharlesMessier.

Triangle galaxy is another important member of the local galaxy group. Compared with our Milky Way galaxy, this galaxy is much smaller than its big neighbor, Andromeda galaxy M3 1, but closer to the average size of spiral galaxies in the universe. A small member galaxy LGS3 in this galaxy group may be the satellite galaxies of M33, which itself may be a distant but gravitationally related companion galaxy of Andromeda M3 1.

According to the data of R.BrentTully, it is approaching us (solar system) at the speed of 182 km/s, or according to the data of NED, the speed is179+/-3 km/s. After correcting our motion around the center of the Milky Way, it is still approaching our galaxy at the speed of 24 kilometers per second.

M33 may have been first discovered by Hodierna before 1654 (the open cluster NGC752 may also be discovered). 1764 On August 25th, this celestial body was independently rediscovered by CharlesMessier, who incorporated it into the catalog. Although William Herschel always avoided numbering the messier objects in other sky surveys, he still numbered this celestial body HV. 1 1 day in September. Because of Herschel's catalog, the brightest and largest HII region (diffuse emission nebula containing ionized hydrogen) in M33 also got its own NGC number: NGC604 (William Herschel's number is HIII.150); It is located in the northeast of this galaxy; That is, the obvious bright spot near the top of our photo. This is one of the largest known HII regions: its diameter is close to 1500 light years, and its spectral line is similar to that of Orion Nebula M42. Huiyang (university of Illinois) and JeffJ J. Hearst (Arizona State University) took photos of NGC604 with Hubble Space Telescope, and distinguished more than 200 young high-temperature massive stars (about 15 to 60 times the mass of the sun) recently formed there.

M33 is one of the first "spiral nebulae" confirmed by WilliamParsons, the third Sir of Deiros. Look at his sketch. It was also identified as one of the first "nebulae" of the galaxy because of the discovery of Cepheid variable stars. EdwinHubble published the basic research results in 1926 (Hubble 1926). Several other bright spots in the spiral arm have also been assigned corresponding NGC catalog numbers: NGCs588, 592, 595, NGC603(RNGC thinks that the latter does not exist, although they mentioned that it is also included in the Zwicky catalog), ICs 13 1, 132, 65438. 136, 137, 139-40, 142 and 143(NGC2000.0 put IC 134 and139-. Some of them are also marked on our map. KennethGlynJones pointed out that they can be observed with a 12.5-inch telescope. William. Waller used HST to study the giant emission nebula NGC595 (see Astronomy1June 1995, 16- 18); With the help of Hubble, he analyzed the high-temperature massive stars that excited the gas in the nebula. Our photo was taken by DavidMalin on LaPalma Mountain through the IsaacNewton Telescope (INT) with a photographic platform. The photo shows many celestial bodies in the spiral arms of this beautiful Sc spiral galaxy (such as NGC604, the obvious red spot near the left edge in the upper part of our photo). Interested readers can see more information about this photo. Using different methods, DavidMalin processed different pictures from this M33 photo taken by INT to highlight different features. The result of Hipparcos satellite led to the revision of the cosmic distance scale, which also affected the distance of M33: the current observation value is about 3 million light years. Most data give a distance of 2.3 million to 2.4 million light years, but the value given by SkyCatalogue2000.0 is slightly more than 2.9 million light years (900kpc), which is just closer to the data after the Cepheid Variable Distance is corrected according to the result of Hipparcos 1997. 199 1 The study of Cepheid Variable (Freedman et al., 199 1) in M33 shows that M33 is a little farther away from us than the Andromeda galaxy M3 1. According to our distance value, the distance between M3 1 and M33 is about 750,000 light years. According to previous data, its angular diameter of 73 minutes in the main axis direction (about 2.5 times the diameter of the moon) corresponds to a real scale of about 50,000 light years, which is half the diameter of the Milky Way. But the darkest outer edge seems to extend further, so the actual diameter may exceed 60 thousand light years. The mass of the triangle galaxy is estimated to be between 100 and 40 billion solar masses.

M33 is a Sc-type galaxy, even a "late" type galaxy in this category, so Tully classified it as Scd (in the catalogue of neighboring galaxies). The obvious spiral arms are dotted with the red HII region (including NGC604) and the blue nebula composed of young stars. Budd also discovered a second group of stars, and globular clusters were also discovered. Although no supernovae have been found in the triangle galaxy, radio astronomers have found some supernova remnants and located them with high precision. At present, at least 1 12 variables have been found, including 4 new stars and about 25 Cepheid variables. There is also a strong X-ray source in this galaxy.

For observers, this galaxy can be seen with the naked eye under extremely good conditions; For most people, this is the farthest celestial body visible to the naked eye (few observant stargazers report that they have successfully seen M8 1 under excellent conditions, but this is only an extremely exceptional case). It is obvious in high-quality binoculars, but its surface brightness is extremely low, because its considerable total brightness is very evenly distributed in an area nearly four times the area of the moon. So it is difficult, even impossible, to observe it with a high-powered telescope-the lowest magnification is the best for this celestial body! The author used a 6-inch telescope and got the best observation effect of M33 at 25 times. M33 is also the most valuable target for astrophotographers. Its spiral arms and bright star clouds can be captured with quite cheap equipment.

More ambitious observers with large telescopes (more than 40cm in diameter) can try to find M33 globular cluster. RichJakiel observed five globular clusters in M33 with a 50 cm telescope. Scientists found a prehistoric map on the wall of the famous Lascaux Cave Group in central France. It is reported that this picture is 16500 years ago (ice age). It depicts the orientation map of the three most dazzling stars in the night sky at that time, which are now called the "summer triangle" in astronomy. The so-called "summer triangle" refers to Vega, Altair and Tianjin IV in Lyra. People concerned believe that the discovery of this constellation has pushed forward human understanding of this field for thousands of years. A professor from the University of Munich, Germany, who participated in the research, said that it can be seen from the scenes depicted in this map that prehistoric humans mastered astronomy much more deeply than we now think. 1940, scientists discovered Lascaux caves in France, and found that there were a large number of animal patterns drawn by prehistoric humans inside the caves. These patterns not only show the living standard of early human beings, but also mainly reflect human cognition of science and technology at that time.