synonymWheat Zhelunyun(Magellanic Cloud) generally refers to the Little Magellanic Galaxy
Magellanic galaxy（Small Magellanic Cloud，abbreviation:SMC；Also known as Little Magellanic Cloud, short for:Wheat cloud[2]）, onRhododendronAndHydraBetween is closeGalaxyOne ofDwarf galaxy、Irregular galaxy。The diameter of Magellan galaxy is about 7000Light year[3], including hundreds of millionsfixed star，Total massAbout 7 billion times that of the sun[4]。Its distanceGalaxyAbout 200000 light years, which is the nearestExtragalactic galaxyone of.
It is speculated that the Little Magellanic Galaxy was originallyBarred spiral galaxy, becauseGalaxyOfGravitational disturbanceIt has become an irregular galaxy, but there is still a stick like structure in the core.
At a distance of about 200000 light-years, the Little Magellanic Galaxy is one of the closest neighbors to the Milky Way.It seems vague in the night skyfacula, the size is about 3 °, due to the averageDeclinationIt is - 73 °, so it can only be located south of 15 ° north latitudeLow latitudeSee the area.Because of its low surface luminosity, it can be seen clearly in the environment far away from light pollution.
Panoramic view from the Very Large Telescope observation point.The galaxy is on the left side of the image
In the southern hemisphere,Magellan CloudFor a long time, it has includedSouth Pacific Islanders andAustralian aboriginesIt is part of the legend of local residents.PersiaastronomerAbdul Rahman SufiOn《Book of Stars》These two objects are recorded in.European sailors probably first noticed these two celestial bodies in the Middle Ages, when they were used for navigation.PortugalandNetherlandsTwenty five percent of sailors called them "Cape Clouds," a term that has been retained for centuries.In 1519-1522Ferdinand Magellan During the round the world voyage of the fleet,Antonio PigafetaDescribe them as "dim star clusters"[6]。Published in 1603Johann Bayer Of《Geodetic chart》He named the smaller "cloud"“Wheat cloud”（Nubecula Minor）。[7]
In 1891,Harvard University ObservatoryPeruArequipa RegionOpened aObservation station。From 1893 to 1906, under the guidance of Solon Irving Bailey, the 24 inch telescope in this area was used to observe the Large Magellanic Galaxy and the Small Magellanic Galaxy[9]。Henrietta Swan, an astronomer at Harvard University Observatory·Leavitt Leverage fromArequipaThe change of relative luminosity of stars in Little Magellanic Galaxy has been studied by using the light plate.
In 1908, her published research results showed that she found a“Cluster variable”OfVariable starLater, the prototype star of this variable starCepheid IName, called“Cepheid variable”, itsPhotoperiodSiderealApparent brightnessIt has a lot to do with it.Leavitt believes that all stars in the wheat cloud are approximately the same distance from the Earth, which means that the light variation period isAbsolute magnitudeThere is a similar relationship between[10]。Peripheral light relationSo that people can estimate the distance from other Cepheid variables according to the distance from the Little Magellanic Galaxy[11]。She hopes to find several Cepheid variable stars close enough to the earth, so that they can measure theirparallaxAnd finally determine the distance from the earth.This allows Cepheid variables to act asStandard candleAnd promoted many great astronomical discoveries.[12]
In 1913, Einar Herzpoon estimated the distance of the Little Magellanic Galaxy for the first time by using this peripheral light relationship.First, he measured 13 nearby Cepheid variables, measured the absolute magnitude of a target star with a light change period of one day, and compared it with the light change period of Cepheid variables measured by Leavitt, he estimated thatsunlightAnd the Little Magellanic GalaxySecond gap(About 33000 light years)[13]。Later, with the continuous improvement of observation technology and method, the distance parameters were further refined. Later, the data proved to be a serious underestimate of the real distance, but it did prove the potential utility of this measurement method.[14]
In April 2023, Webb telescope will be usedThe composition of planet formation has been detected around hundreds of young stars in the Magellanic Cloud.[27]
In 2017, usingDark Energy Survey With MagLiteS data, we found a large density related to the Little Magellanic GalaxyStar regionThe research suggests that this may be the result of the interaction between the Magellanic Galaxy and the Large Magellanic Galaxy.[17]
X-ray source
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Magellanic galaxy contains a lot of activeX-ray linked star。Recent star forming events have resulted in a large number ofHigh qualityStars and high qualityX-rayThe emergence of conjoined stars (HMXBs).beardlessStellar clusterAnd most of the known X-ray conjointers are concentrated in the Little Magellanic Galaxy.Most X-ray conjoined stars belong toBe star, this type of systemGalaxy70%, and 98% in the Little Magellanic Galaxy.The equatorial disk of Be star provides a material "repository", which can beneutron staradoptPeristellar pointMost known systems have largeEccentricity）Or in the process of mass ejection, it is accumulated on the neutron star.This situation will lead to a large X-ray burst, which is typicalX-ray photometryIs Lx=10thirty-six-10thirty-sevenerg/s。
During the Nike Tomahawk flight on September 20, 1966Magellan CloudX-ray higher than the background star is observed in[18]。October 24, 1967, fromAustraliaMilduraYes, smallMagellanic Clouds Balloon observation, setting the upper limit of X-ray detection[19]。12:54, September 24, 1970（UTC）FromJohnston AtollEmittingPGM-17 Raytheon missileYou have one onX-ray astronomyThe instrument is used to observe the Little Magellanic Galaxy at an altitude of more than 300 kilometers.The X-ray luminosity emitted from the small Magellan galaxy is 1.5-12keV5 × 10 within the rangethirty-eightergs/s，2.5 × 10 in the range of 5-50 keVthirty-nineergs/s，This is obviously an X-rayExtended Source。[20]
FourthUhuru satelliteThe probe data listsRhododendronAn early X inRadio source：4U 0115-73（3U 0115-73，2A 0116-737，SMCX-1）[21]。Uhuru satellite observed the Little Magellanic Galaxy on January 1, 12, 13, 16 and 17, 1971, and detected a ray source located at 01149-7342, which was then named SMC X-1[22]。Some X-ray data were also received on January 14, 15, 18 and 19, 1971[23]。The third Ariel 5 data (3A) also contains this early X-ray source in the constellation Rhododendron, which is numbered 3A 0116-736 (2A 0116-737, SMC X-1).[24]SMC X-1 is aHMXRB，At J2000Right ascension: 01h 15m 14s, declination: 73 ° 42 ′ 22 ″.
The other two radiation sources detected and listed in 3A include SMC of 3A 0042-738X-2SMC of 3A 0049-726X-3。[24]
Related research
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Astrophysicist DS. Mathewson, V.L.Ford and NVisvanathan proposed thatGalaxyIn fact, it may be divided into two partsA smaller part of the galaxy is behind the main part of the galaxy and is about 30000 light-years apart.They believe that the reason for this is that the Little Magellanic Galaxy andLarge Magellanic GalaxyOfInteractionAs a result, they are separated, and the two parts are still being separated.They call this smaller part the "mini Magellanic Cloud".[25-26]
