CygnusbyNorthern constellationone of.At 20:00 on September 25 every year,CygnusRise to the middle of the sky.Summer and autumn are the best time to observe Cygnus.Interestingly, the constellation Cygnus rises and falls like a swan flying: it rises from the northeast to the sky on its side. When it reaches the zenith, it heads west, and when it moves to the northwest, it turns head down and tail up and disappears into the horizon.
Cygnus is completely immersed in the white Milky WayAquilaandLyraThree constellations stand in a tripodPrimary star(alpha star), i.eNiulang Star、VegaandTianjin IVFormed a largetriangle(The big triangle in summer).IntracerataApparent magnitudeThere are 191 stars brighter than the sixth order, and 22 stars brighter than the fourth order.Therefore, in the summer night sky, although the Milky Way is like gauze and stars are crowded, Cygnus is not difficult to find, and it can still show its glory in the Milky Way.
The main stars of the constellation Cygnus are arranged like a big cross, so they used to be called the "North Cross".It is easy to imagine the cross as a swan. The long vertical line under the cross is the swan's long neck and the horizontal line is the swan's wings.[1]
Research History
stayancient GreekAt that time, the main star of Cygnus had been described as a swan《The one thousand one night》In the navigation story of Central Sinbad, it was once described as a "roc bird".[1]
There are several bright stars in the constellation Cygnus.
Tianjin IV
Cygnus in the night sky
Tianjin IV(Alpha Cygni, also called Deneb) is the brightest star in the constellation Cygnus.It is aSpectral typeIt is white of A2IaeSupergiant，the magnitudeVarying between 1.21 and 1.29, it is one of the largest and brightest A-type stars known.It is located at the tail of the swan, about 3200 light years away from the earth.Around this star, there areGas cloudAn enclosure formed.In the next 8300 years, Tianjin IV will be far away from the celestial sphereNorth PoleIt is only 6.6 degrees, which is the bright star closest to the North Pole. Then it will become“Polaris”。
Tianjin II(Delta Cygni, also known as Fawaris) is another bright binary system in the constellation Cygnus, 171 light-years away from Earth, with a cycle of 800 years.The main star is a 2.9 class blue white giant star, and the companion star is a 6.6 class star.Medium amateur telescopes can distinguish the two stars.
Tianjin IX(Epsilon Cygni, also called Aljanah) is an orange giant star with a magnitude of about 2.5 and a distance of 72 light-years from the Earth.
Other noteworthy stars
There are several other darker binary systems in the constellation Cygnus.μ Cygnus is a binary star system, with the third star that is optically visible (not related to the binary star system). The cycle of mutual rotation is 790 years, 73 light-years away from the Earth.The magnitude of the main star and companion star is 4.8 and 6.2 respectively, and the magnitude of the third star is 6.9.The third star is inBinocularsThe main star and the companion star can be separated by a medium-sized amateur telescope.
Tianjin San (30 Cygni) andCygnus 31(31 Cygni) forms a contrasting binary system, similar to the brightAlbireo 。The two are separable in binoculars.The main star, 31 Cygnus, is an orange star with a magnitude of 3.8 and 1400 light-years away from Earth.Companion Tianjin SanchengTurquoise, the spectral type is A5IIIn, the magnitude is 4.83, and it is about 610 light-years away from the Earth.Cygnus 31 itself is a binary system, and its companion star is a blue star with a star grade of 7.0.Cygnus ψ is a binary system that can be distinguished in a small amateur telescope. It is composed of two white stars.The main star magnitude is 5.0, and the companion star magnitude is 7.5.Tianjin Zeng-29 is a binary system that can be distinguished from large binoculars or small amateur telescopes.It is 11.4 light years away from the earth and rotates for 750 years.These two ingredients are orangedwarf star（Main preface）For stars, the main star is 5.2, and the companion star is 6.1.Tianjin Zeng-29 is the first knownparallaxOf stars,Friedrich William BesselIts parallax was determined in 1838.
be locatedThe chariot road increases by five(also known as Cygnus η)X-ray sourceCygnus X-1The X-ray source is a black hole near the binary system, which is devouring these two stars.This is the first X-ray source considered to be a black hole.Cygnus also contains some other noteworthy X-ray sources:Cygnus X-3Is aMicroquasar(microquasar), which is surrounded byCompact starThe rotation period of Wolf Rayet star is only 4.8 hours.The system is one of the brightest X-ray sources observed.The system will have periodic bursts, and during one burst, people find that it is launchingMuon。Although people once thought that the dense star in the center wasneutron starOr black hole, this object may also be the remains of an abnormal star, which may be the first to be foundQuark star。If this star is a normal neutron star, it will not emit muons.The system also emits high energyGamma rayThis will help astronomers understand the formation process of these rays.
Cygnus also contains several variable stars.SS Cygni（SS Cygnus）Is aDwarf nova(or calledGeminiU-shaped variable star, yesCataclysmic variable starIt will erupt every 7-8 days.The system'sTotal magnitudeFrom the darkest level 12 to the lightest level 8.The two stars in the system are very close,Orbital periodLess than 0.28 days.Cygnus χ(Chi Cygni) is aRed GiantIs also the second brightestMira variable star。Its magnitude varies between 3.3 and 14.2, its spectral type ranges from S6,2e to S10,4e (MSe), and its variation period is 408 days.Its diameter is 300 times the diameter of the sun, 350 light years away from the earth.Tianjin Zengjiu(P Cygni) is a luminous blue variable star, whose magnitude suddenly increased to 3 in 1600 AD.Since 1715, although it is more than 5000 light years away from the Earth, the star's magnitude has also reached 5.The spectrum of this star is very unusual, because it contains very strongSpectral line。W Cygni is a semi regular red giant star, 618 light-years away from the Earth, with the maximum magnitude of 5.10 and the minimum magnitude of 6.83, and the variation period of 131 days.It is a red giant with spectral type M4e-M6e (Tc:) III changing. NML Cygni is a red supergiant, 5300 light-years away from EarthSemiregular variable star。It is the currentGalaxyOne of the largest stars in theSolar radius。Its magnitude is about 16.6 and its period is about 940 days.
V1331 Cygnus
Cygnus is also Kepler's satellite searchingExtrasolar planetsTherefore, there are about 100 stars in Cygnus with known planets, which is the largest of all constellations.One of the most noteworthy systems isKepler-11The system consists of six planets, all located in a plane of about one degree.The spectral type is G6V, indicating that this star is slightly cooler than the sun.Except for the last planet, the distance between all planets and Kepler-11 is less thanMercuryThe distance from the sun.All the planets are bigger than the earth.Star Xi Zhongsi（16 Cygni）Is aSamsung system, about 70 light years from the earthHelioid starAnd aRed dwarfIt consists of a planet orbiting one of the sun like stars.Gliese 777 is a multi star system containing yellow stars and red dwarfs, as well as a planet.This planet is somewhat similar to Jupiter, but its mass is slightly largerEccentric trackMore slanted than Jupiter.Kepler-22 system is also worth noting that itsouter planetIt is the first planet similar to the Earth discovered so far.
People find a lot in Cygnusdeep space , includingOpen cluster、supernova remnant And various strange nebulae.The constellation background in Cygnus is so rich that some open star clusters are submerged in light and cannot be observed.
M39(NGC 7092) is an open star cluster 950 light-years away from us, visible to the naked eye in the dark sky.It has about 30 bright stars, which are loosely distributed in a triangular area.The brightest star in M39 is 7.Another open star cluster in Cygnus isSummer open clusters(NGC 6910), with 16 starsAstronomical telescopeVisible in, diameter 5Arcminute, average magnitude 7.4.
Other open star clusters in Cygnus include Dolidze 9, Dolidze 11, Collinder 421 and Berkeley 90.Dolidze 9 is 2800 light years away from the earth, and about 20 million years old. It is a young and weak open star cluster, of which 22 stars can be seen in small and medium-sized amateur telescopes.Dolidze 11 is a 400 million year old open star cluster, 3700 light-years away from us. With amateur telescopes, we can see more than 10 stars, of which the brightest is 7.5.Collider 421 is a particularly ancient open star cluster, with an age of about 1 billion years and a magnitude of 10.1.It is 3100 light years away from the Earth and has a diameter of 8 arc seconds.The stars in the north of the cluster are golden, while those in the south are slightly orange.Berkeley 90 is a small open star cluster with a diameter of 5 minutes of arc.
NGC 6826It's an 8.5 classPlanetary nebula, about 300 light years from the earth.Its central star is a 10th class star, which is particularly prominent in the telescope, and even sometimes appears in the telescopeeyepieceFlashes in.WhenObserverFocus on thisSidereal time, the nebula nearby seems to become dim.
North American nebula NGC7000
North American nebula（NGC 7000）It is one of the most famous nebulae in the constellation Cygnus. It is visible to the naked eye in the dark sky.However, its characteristic shape is onlytime exposureIs visible in the photo of.Because the North American nebula is very large, itsSurface brightnessVery low, it is difficult for people to see it directly through the telescope.The North American nebula is illuminated by a sixth magnitude star in its center. This nebula is 1500 light-years away from the Earth and covers about 2 degrees of the sky.
Veil Nebula East
To the south of Tianjin Jiu isVeil Nebula (NGC 6960696269796992 and 6995)Supernova remnant, covering about 3 degrees of the sky
, the total length exceeds 50 light years.Its unique ring shape gives it another nickname: Cygnus Loop.The brightest part of the Veil Nebula (NGC6992) is faintly visible in binoculars, but itsRing mountingThe shape can only be exposed for a long timeAstronomical photographOnly in the middle can you see it.
Gamma-Swan Nebula(Gamma Cygni nebula, also known asIC 1318）Is both aDiffuse nebula, is also aDark nebula, across the sky of more than 4 degrees.Two of themEmission nebula: Sharpness 2-112 and Sharpness 2-115.When viewed through amateur telescopes, Sharpless 2-112 seems to be in the form of tears.The eastern nebula can be seen more clearly using the secondary ionization oxygen filter (O III).
Cygnus X is the largest near the sunStar formationRegion, where some of the largest and brightest stars are born today (such asCygnus OB2-12）And many youngGlobular cluster。
In Greek mythology, the godsZeusAttracted by the beauty of Princess Leda, but afraid of being enviousHeraAnger, and it is difficult to entice the pure girl if she appears in her own image.So he came up with a trick and transformed it into aswan。
One day, Leda was playing on an island when he saw a swan flying down from the white clouds. It was so beautiful and lovely, and it was not afraid of people. Let Leda touch and hug it. Its feathers were white, its body was soft, and Leda loved it. Filled with intoxication and excitement, Leda unconsciously held the swan to sleep.When she woke up, the swan reluctantly left her, spread its strong wings and flew to the sky.Leda felt uncomfortable after returning to the palace, and soon found that she was pregnant.wait untilOctober pregnancyGive birth to a pair upon expirationtwin boys。It becameGeminiThe Greek heroes Castor and Polutex.
Later, Leda obeyed his father's order and marriedSpartaKing Tyndareus married two more daughters, one named Lvnistra, and marriedTroy WarThe supreme commander of the Central GreeksAgamemnon；One is calledHelen, married Agamemnon's brotherMenelaus。ZeusI am very happy to return to Tianting to commemorate thisRomanceHe left his swan in the sky and becameCygnus。
Myth 2
Cygnus
In Greek mythology,Helios's youngest son（Phaethon ）He drove his father's "solar car" but could not drive it, so he caused a big disaster.The Emperor of Heaven (Zeus) killed him with thunder and lightning.A good friend of Phaethon (Saignes) was so sad when he learned about it that he turned into a swan and searched for Phaethon's body everywhere in the sky of the Milky Way.
Myth 3
Zeus in pursuit of VengeanceNemesisTurn yourself into a swan and call Love GodAphroditeHe became an eagle to chase himself and win Nemesis's sympathy. After a turn, he finally won the hearts of beauty. To commemorate this event, Zeus raised the swan and the eagle to the sky together and became Cygnus and Aquila.
Myth IV
Cygnus
Zeus turned into a swan to seduce Sparta's empress Leda, who later laid an eggGeminiCastor, Polluces/Pollux and Helen (it is said that Castor and Pollux were on the same egg, Helen and Clutennestra on the other egg, a total of two eggs). Later, the eggshells were placed in the Temple of Sparta, suspended on the roof with ribbons, to avoid confusion,Castor and Cluteniestra are usually regarded as the bones and flesh of the Spartan emperor Tyndareus, while Helen and Poludukus are the bones and flesh of Zeus.
Myth Five
Zeus passed Rhamnus in the north of Athens, and fell in love at first sight when he saw Nemesis, the goddess of revenge. In order to avoid Zeus, Nemesis turned into a different animal and fled, first from the river, then from the land, and finally into a swan. After many pursuits, he still failed to escape from Zeus, and finally was caught by the swan in the incarnation of Zeus and committed violence.
meteor shower
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Cygnus
Cygnus also has a very famousmeteor shower, YesFireball, usually in late August, the peak period is on August 20,Radiant pointNear k-star, the end of the meteor can often see bright bursts, which is very eye-catching in the summer sky.
P-type star
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A kind of star whose spectrum has a special emission line, whose spectrum type is mostly B-type, and whose gas shell expands outward.Cygnus PStars are typical examples of such stars.The visual magnitude of P in Cygnus is 4.9.It was discovered in 1600, when the visual magnitude increased by 3 degrees, and was once regarded as a new star.After that, there was a series of irregular changes in the luminosity, which began to stabilize after about 1715.It is aSpectral classificationIs a supergiant of B1 Ia.Its parameters are quite controversial.A study in 1979 suggested that its distance was 1.8 ± 0.7Kilosecond gap，Absolute thermal magnitude- 8.9 ± 1.4, surfaceEffective temperature17000 ± 3000K, 60 ± 30 times the solar radius, 40 ± 20 times the massSolar mass。This star is constantly throwing out matter,Mass loss rateAbout 3 × 10-5 solar mass per year.The ejected material forms an outward expanding gas shell around it. The density of the gas shell is relatively thin, which can generateComposite spectrumConditions.Cygnus P starThe spectral structure of is very special. There is aAbsorption lineOccasionally, there are two absorption lines at some spectral components.AbsorptiveViolet shiftIt indicates that the gas shell is expanding outward continuously, and the appearance of two absorption lines indicates that there are two gas shells with different velocities at the same time.The expansion velocity of the gas shell calculated according to the absorption lines of various elements is in the range of 30-250 kilometers per second, and the infrared andRadio radiation。
Scientists found that the highest energy photons came from the very active star forming region in the constellation Cygnus, and also found 12 stable gamma raysRadio source，Photon energyIt extends to near one electron volt, which is located atLHAASOfieldThe brightest group of galactic gamma ray sources within, the measured gamma photon signal is 7 times higher than the backgroundstandard deviation Above, source locationmeasurement accuracy Better than 0.3 °.[2]
