Vulpecula is a faint constellation in the northern sky. Its name is Latin for "little fox", although it is known as the fox, it was identified in the seventeenth century, is located in the middle of the Summer Triangle. There are no stars brighter than 4th magnitude in this constellation; the brightest star in Vulpecula is Alpha Vulpeculae, a magnitude 4.44m red giant at a distance of 297 light-years. The star is an optical binary; the star carries the traditional name Anser, which refers to the goose the little fox holds in its jaws.23 Vulpeculae is the second brightest star in the constellation. In 1967, the first pulsar, PSR B1919+21, was discovered in Vulpecula by Jocelyn Bell, supervised by Antony Hewish, in Cambridge. While they were searching for scintillation of radio signals of quasars, they observed pulses which repeated with a period of 1.3373 seconds. Terrestrial origin of the signal was ruled out because the time it took the object to reappear was a sidereal day instead of a solar day.
This anomaly was identified as the signal of a rotating neutron star. Fifteen years after the first pulsar was discovered, the first millisecond pulsar, PSR B1937+21, was discovered in Vulpecula, only a few degrees in the sky away from PSR B1919+21. Vulpecula is home to HD 189733 b, one of the closest extrasolar planets being studied by the Spitzer Space Telescope. On 12 July 2007 the Financial Times reported that the chemical signature of water vapour was detected in the atmosphere of this planet. Although HD 189733b with atmospheric temperatures rising above 1,000 °C is far from being habitable, this finding increases the likelihood that water, an essential component of life, would be found on a more Earth-like planet in the future; the Dumbbell Nebula, is a large, bright planetary nebula, discovered by the French astronomer Charles Messier in 1764 as the first object of its kind. It can be seen with good binoculars in a dark sky location, appearing as a dimly glowing disk 6 arcminutes in diameter.
A telescope reveals its double-lobed shape, similar to that of an hourglass. Brocchi's Cluster is an asterism thought to be an open cluster, it is called "the Coathanger" because of its distinctive star pattern when viewed with binoculars or a low power telescope. NGC 7052 is an elliptical galaxy in Vulpecula at a distance of 214 million light-years from Earth, it has a central dusty disk with a diameter of 3700 light-years. Astronomers surmise that the disk is the remnant of a smaller galaxy that merged with NGC 7052. Jets can be seen emanating from the galaxy, it has strong radio emissions; this means that it is classified as a radio galaxy. The eastern part of Vulpecula is occupied by the Hercules–Corona Borealis Great Wall, it is a galaxy filament, with the length of 3,000 megaparsecs, making it the largest structure in the universe. In the late 17th century, the astronomer Johannes Hevelius created Vulpecula, it was known as Vulpecula cum ansere or Vulpecula et Anser, was illustrated with a goose in the jaws of a fox.
Hevelius did not regard the fox and the goose to be two separate constellations, but the stars were divided into a separate Anser and Vulpecula. Today, they have been merged again under the name of the fox, but the goose is remembered by the name of the star α Vulpeculae: Anser. 3C 433 Ridpath, Ian. Stars and Planets Guide. London: William Collins. ISBN 978-0-008-23927-5; also available from Princeton University Press, Princeton: ISBN 978-0-691-17788-5. The Deep Photographic Guide to the Constellations: Vulpecula Vulpecula page at SEDS M-27 page at SEDS Star Tales - Vulpecula
A globular cluster is a spherical collection of stars that orbit a galactic core, as a satellite. Globular clusters are tightly bound by gravity, which gives them their spherical shapes, high stellar densities toward their centers; the name of this category of star cluster is derived from globulus -- a small sphere. A globular cluster is sometimes known, more as a globular. Globular clusters are found in the halo of a galaxy and contain more stars, are much older, than the less dense, open clusters which are found in the disk of a galaxy. Globular clusters are common. Larger galaxies can have more: The Andromeda Galaxy, for instance, may have as many as 500; some giant elliptical galaxies, such as M87, have as many as 13,000 globular clusters. Every galaxy of sufficient mass in the Local Group has an associated group of globular clusters, every large galaxy surveyed, has been found to possess a system of globular clusters; the Sagittarius Dwarf galaxy, the disputed Canis Major Dwarf galaxy appear to be in the process of donating their associated globular clusters to the Milky Way.
This demonstrates. Although it appears that globular clusters contain some of the first stars to be produced in the galaxy, their origins and their role in galactic evolution are still unclear, it does appear clear that globular clusters are different from dwarf elliptical galaxies and were formed as part of the star formation of the parent galaxy, rather than as a separate galaxy. The first known globular cluster, now called M22, was discovered in 1665 by Abraham Ihle, a German amateur astronomer. However, given the small aperture of early telescopes, individual stars within a globular cluster were not resolved until Charles Messier observed M4 in 1764; the first eight globular clusters discovered are shown in the table. Subsequently, Abbé Lacaille would list NGC 104, NGC 4833, M55, M69, NGC 6397 in his 1751–52 catalogue; the M before a number refers to Charles Messier's catalogue, while NGC is from the New General Catalogue by John Dreyer. When William Herschel began his comprehensive survey of the sky using large telescopes in 1782 there were 34 known globular clusters.
Herschel discovered another 36 himself and was the first to resolve all of them into stars. He coined the term "globular cluster" in his Catalogue of a Second Thousand New Nebulae and Clusters of Stars published in 1789; the number of globular clusters discovered continued to increase, reaching 83 in 1915, 93 in 1930 and 97 by 1947. A total of 152 globular clusters have now been discovered in the Milky Way galaxy, out of an estimated total of 180 ± 20; these additional, undiscovered globular clusters are believed to be hidden behind the gas and dust of the Milky Way. Beginning in 1914, Harlow Shapley began a series of studies of globular clusters, published in about 40 scientific papers, he examined the RR Lyrae variables in the clusters and used their period–luminosity relationship for distance estimates. It was found that RR Lyrae variables are fainter than Cepheid variables, which caused Shapley to overestimate the distances of the clusters. Of the globular clusters within the Milky Way, the majority are found in a halo around the galactic core, the large majority are located in the celestial sky centered on the core.
In 1918, this asymmetrical distribution was used by Shapley to make a determination of the overall dimensions of the galaxy. By assuming a spherical distribution of globular clusters around the galaxy's center, he used the positions of the clusters to estimate the position of the Sun relative to the galactic center. While his distance estimate was in significant error, it did demonstrate that the dimensions of the galaxy were much greater than had been thought, his error was due to interstellar dust in the Milky Way, which absorbs and diminishes the amount of light from distant objects, such as globular clusters, that reaches the Earth, thus making them appear to be more distant than they are. Shapley's measurements indicated that the Sun is far from the center of the galaxy contrary to what had been inferred from the nearly distribution of ordinary stars. In reality, most ordinary stars lie within the galaxy's disk and those stars that lie in the direction of the galactic centre and beyond are thus obscured by gas and dust, whereas globular clusters lie outside the disk and can be seen at much further distances.
Shapley was subsequently assisted in his studies of clusters by Henrietta Swope and Helen Battles Sawyer. In 1927–29, Shapley and Sawyer categorized clusters according to the degree of concentration each system has toward its core; the most concentrated clusters were identified as Class I, with successively diminishing concentrations ranging to Class XII. This became known as the Shapley–Sawyer Concentration Class In 2015, a new type of globular cluster was proposed on the basis of observational data, the dark globular clusters; the formation of globular clusters remains a poorly understood phenomenon and it remains uncertain whether the stars in a globular cluster form in a single generation or are spawned across multiple generations over a period of several hundred million years. In many globular clusters, most of the stars are at approxima
Astrosat is India's first dedicated multi-wavelength space telescope. It was launched on a PSLV-XL on 28 September 2015. With the success of this satellite ISRO has proposed to launch AstroSat-2 as a successor for Astrosat when nears its five-year life span. After the success of the satellite-borne Indian X-ray Astronomy Experiment, launched in 1996, the Indian Space Research Organization approved further development for a full-fledged astronomy satellite, Astrosat, in 2004. A number of astronomy research institutions in India, abroad have jointly built instruments for the satellite. Important areas requiring coverage include studies of astrophysical objects ranging from nearby solar system objects to distant stars and objects at cosmological distances. Astrosat is a multi-wavelength astronomy mission on an IRS-class satellite into a near-Earth, equatorial orbit; the five instruments on board cover the visible, near UV, far UV, soft X-ray and hard X-ray regions of the electromagnetic spectrum.
Astrosat was launched on 28 September 2015 from the Satish Dhawan Space Centre on board a PSLV-XL vehicle at 10:00AM. Astrosat is a proposal-driven general purpose observatory, with main scientific focus on: Simultaneous multi-wavelength monitoring of intensity variations in a broad range of cosmic sources Monitoring the X-ray sky for new transients Sky surveys in the hard X-ray and UV bands Broadband spectroscopic studies of X-ray binaries, AGN, SNRs, clusters of galaxies, stellar coronae Studies of periodic and non-periodic variability of X-ray sourcesAstrosat performs multi-wavelength observations covering spectral bands from radio, optical, IR, UV, X-ray wavelengths. Both individual studies of specific sources of interest and surveys are undertaken. While radio, IR observations would be coordinated through ground-based telescopes, the high energy regions, i.e. UV, X-ray and visible wavelength, would be covered by the dedicated satellite-borne instrumentation of Astrosat; the mission would study near simultaneous multi-wavelength data from different variable sources.
In a binary system, for example, regions near the compact object emit predominantly in the X-ray, with the accretion disc emitting most of its light in the UV/optical waveband, whereas the mass of the donating star is brightest in the optical band. The observatory will carry out: Low- to moderate-resolution spectroscopy over a wide energy band with the primary emphasis on studies of X-ray-emitting objects Timing studies of periodic and aperiodic phenomena in X-ray binaries Studies of pulsations in X-ray pulsars Quasi-periodic oscillations, flickering and other variations in X-ray binaries Short- and long-term intensity variations in active galactic nuclei Time-lag studies in low/hard X-rays and UV/optical radiation Detection and study of X-ray transients. In particular, the mission will train its instruments at active galactic nuclei, which are believed to contain super-massive black holes; the scientific payload contains six instruments. The Ultra Violet Imaging Telescope performs imaging in three channels: 130–180 nm, 180–300 nm, 320–530 nm.
The three detectors are vacuum image intensifiers manufactured by Photek, UK. The FUV detector consists of a CsI photocathode with a MgF2 input optic, the NUV detector consists of CsTe photocathode with a fused-silica input optic and the visible detector consists of an alkali-antimonide photocathode with a fused-silica input optic; the field of view is a circle of ~28′ diameter and the angular resolution is 1.8" for the ultraviolet channels and 2.5″ for the visible channel. In each of the three channels a spectral band can be selected through a set of filters mounted on a wheel; the primary mirror diameter of the telescope is 40 cm. The Soft X-ray imaging Telescope employs focusing optics and a deep depletion CCD camera at the focal plane to perform X-ray imaging in the 0.3–8.0 keV band. The optics will consist of 41 concentric shells of gold-coated conical foil mirrors in an approximate Wolter-I configuration; the focal plane CCD camera will be similar to that flown on SWIFT XRT. The CCD will be operated at a temperature of about −80 °C by thermoelectric cooling.
The LAXPC Instrument covers X-ray timing and low-resolution spectral studies over a broad energy band, Astrosat will use a cluster of 3 co-aligned identical Large Area X-ray Proportional Counters, each with a multi-wire-multi-layer configuration and a Field of View of 1° × 1°. These detectors are designed to achieve wide energy band of 3–80 keV, high detection efficiency over the entire energy band, narrow field of view to minimize source confusion, moderate energy resolution, small internal background and long lifetime in space; the effective area of the telescope is 6000 cm2. The Cadmium Zinc Telluride Imager is a hard X-ray imager, it will consist of a Pixellated Cadmium-Zinc-Telluride detector array of 500 cm2 effective area and the energy range from 10 to 150 kev. The detectors have a detection efficiency close to 100% up to 100 keV, have a superior energy resolution compared to scintillation and proportional counters, their small pixel size facilitates medium resolution imaging in hard x-rays.
The CZTI will be fitted with a two dimension
A Ritchey–Chrétien telescope is a specialized variant of the Cassegrain telescope that has a hyperbolic primary mirror and a hyperbolic secondary mirror designed to eliminate off-axis optical errors. The RCT has a wider field of view free of optical errors compared to a more traditional reflecting telescope configuration. Since the mid 20th century, a majority of large professional research telescopes have been Ritchey–Chrétien configurations; the Ritchey–Chrétien telescope was invented in the early 1910s by American astronomer George Willis Ritchey and French astronomer Henri Chrétien. Ritchey constructed the first successful RCT, which had a diameter aperture of 60 cm in 1927; the second RCT was a 102 cm instrument constructed by Ritchey for the United States Naval Observatory. The basic Ritchey–Chrétien two-surface design is free of third-order coma and spherical aberration, although it does suffer from fifth-order coma, severe large-angle astigmatism, comparatively severe field curvature.
The remaining aberrations of the basic design may be improved with the addition of smaller optical elements near the focal plane. When focused midway between the sagittal and tangential focusing planes, stars are imaged as circles, making the RCT well suited for wide field and photographic observations; as with the other Cassegrain-configuration reflectors, the RCT has a short optical tube assembly and compact design for a given focal length. The RCT offers good off-axis optical performance, but the Ritchey–Chrétien configuration is most found on high-performance professional telescopes. A telescope with only one curved mirror, such as a Newtonian telescope, will always have aberrations. If the mirror is spherical, it will suffer from spherical aberration. If the mirror is made parabolic, to correct the spherical aberration it must suffer from coma and astigmatism. With two non-spherical mirrors, such as the Ritchey–Chrétien telescope, coma can be eliminated as well; this allows a larger useful field of view.
However, such designs still suffer from astigmatism. This too can be cancelled by including a third curved optical element; when this element is a mirror, the result is a three-mirror anastigmat. Alternatively, a Ritchey-Chrétien may use one or several low-power lenses in front of the focal plane as a field-corrector to correct astigmatism and flatten the focal surface, as for example the SDSS telescope and the VISTA telescope. In practice, each of these designs may include any number of flat fold mirrors, used to bend the optical path into more convenient configurations. In a Ritchey-Chrétien design, as in most Cassegrain systems, the secondary mirror blocks a central portion of the aperture; this ring-shaped entrance aperture reduces a portion of the modulation transfer function over a range of low spatial frequencies, compared to a full-aperture design such as a refractor. This MTF notch has the effect of lowering image contrast. In addition the support for the secondary may introduce diffraction spikes in images.
The radii of curvature of the primary and secondary mirrors in a two-mirror Cassegrain configuration are R 1 = − 2 D F F − B and R 2 = − 2 D B F − B − D where F is the effective focal length of the system, B is the back focal length, D is the distance between the two mirrors. If, instead of B and D, the known quantities are the focal length of the primary mirror, f 1, the distance to the focus behind the primary mirror, b D = f 1 / and B = D + b. For a Ritchey–Chrétien system, the conic constants K 1 and K 2 of the two mirrors are chosen so as to eliminate third-order spherical aberration and coma.
Cygnus is a northern constellation lying on the plane of the Milky Way, deriving its name from the Latinized Greek word for swan. Cygnus is one of the most recognizable constellations of the northern summer and autumn, it features a prominent asterism known as the Northern Cross. Cygnus was among the 48 constellations listed by the 2nd century astronomer Ptolemy, it remains one of the 88 modern constellations. Cygnus contains Deneb -which is one of the brightest stars in the night sky and is the most distant first-magnitude star- as its "tail star" and one corner of the Summer Triangle, it has some notable X-ray sources and the giant stellar association of Cygnus OB2. Cygnus is known as the Northern Cross. One of the stars of this association, NML Cygni, is one of the largest stars known; the constellation is home to Cygnus X-1, a distant X-ray binary containing a supergiant and unseen massive companion, the first object held to be a black hole. Many star systems in Cygnus have known planets as a result of the Kepler Mission observing one patch of the sky, an area around Cygnus.
In addition, most of the eastern part of Cygnus is dominated by the Hercules–Corona Borealis Great Wall, a giant galaxy filament, the largest known structure in the observable universe, covering most of the northern sky. In Greek mythology, Cygnus has been identified with several different legendary swans. Zeus disguised himself as a swan to seduce Leda, Spartan king Tyndareus's wife, who gave birth to the Gemini, Helen of Troy, Clytemnestra; the Greeks associated this constellation with the tragic story of Phaethon, the son of Helios the sun god, who demanded to ride his father's sun chariot for a day. Phaethon, was unable to control the reins, forcing Zeus to destroy the chariot with a thunderbolt, causing it to plummet to the earth into the river Eridanus. According to the myth, Phaethon's brother, grieved bitterly and spent many days diving into the river to collect Phaethon's bones to give him a proper burial; the gods were so touched by Cygnus's devotion to his brother that they turned him into a swan and placed him among the stars.
In Ovid's Metamorphoses, there are three people named Cygnus, all of whom are transformed into swans. Alongside Cygnus, noted above, he mentions a boy from Tempe who commits suicide when Phyllius refuses to give him a tamed bull that he demands, but is transformed into a swan and flies away, he mentions a son of Neptune, an invulnerable warrior in the Trojan War, defeated by Achilles, but Neptune saves him by transforming him into a swan. Together with other avian constellations near the summer solstice, Vultur cadens and Aquila, Cygnus may be a significant part of the origin of the myth of the Stymphalian Birds, one of The Twelve Labours of Hercules. In Hinduism, the period of time or the Muhurta which lasts from 4:24 AM to 5:12 AM is called the "Brahma Muhurta" translating to "The moment of the Universe" and the Star system in correlation is the Cygnus constellation; this is a auspicious time to do any task or start the day. In Polynesia, Cygnus was recognized as a separate constellation. In Tonga it was called Tuula-lupe, in the Tuamotus it was called Fanui-tai.
Deneb was often given a name. The name Deneb comes from the Arabic name dhaneb, meaning "tail", from the phrase Dhanab ad-Dajājah, which means “the tail of the hen”. In New Zealand it was called Mara-tea, in the Society Islands it was called Pirae-tea or Taurua-i-te-haapa-raa-manu, in the Tuamotus it was called Fanui-raro. Beta Cygni was named in New Zealand. Gamma Cygni was called Fanui-runga in the Tuamotus. A large constellation, Cygnus is bordered by Cepheus to the north and east, Draco to the north and west, Lyra to the west, Vulpecula to the south, Pegasus to the southeast and Lacerta to the east; the three-letter abbreviation for the constellation, as adopted by the IAU in 1922, is'Cyg'. The official constellation boundaries, as set by Eugène Delporte in 1930, are defined as a polygon of 28 segments. In the equatorial coordinate system, the right ascension coordinates of these borders lie between 19h 07.3m and 22h 02.3m, while the declination coordinates are between 27.73° and 61.36°. Covering 804 square degrees and around 1.9% of the night sky, Cygnus ranks 16th of the 88 constellations in size.
Cygnus culminates at midnight on 29 June, is most visible in the evening from the early summer to mid-autumn in the Northern Hemisphere. Cygnus is depicted with Delta and Epsilon Cygni as its wings. Deneb, the brightest in the constellation is at its tail, Albireo as the tip of its beak. There are several asterisms in Cygnus. In the 17th-century German celestial cartographer Johann Bayer's star atlas the Uranometria, Alpha and Gamma Cygni form the pole of a cross, while Delta and Epsilon form the cross beam; the nova P Cygni was considered to be the body of Christ. Bayer catalogued many stars in the constellation, giving them the Bayer designations from Alpha to Omega and using lowercase Roman letters to g. John Flamsteed were dropped by Francis Baily. There are several bright stars in Cygnus. Alpha Cygni, called Deneb, is the brightest star in Cygnus, it is a white supergiant star of spectral type A2Iae that varies between magnitudes 1.21 and 1.29, one of the largest and most luminous A-class stars known.
It is located about 3200
AGILE is an X-ray and Gamma ray astronomical satellite of the Italian Space Agency. AGILE's mission is to observe gamma-ray sources in the universe. Key scientific objectives of the AGILE Mission include the study of: Active Galactic Nuclei Gamma-Ray Bursts X-ray and gamma galactic sources Non-identified gamma sources Diffuse galactic gamma emissions Diffuse extra-galactic gamma emissions Fundamental physics AGILE's instrumentation includes a Gamma Ray Imaging Detector sensitive in the 30 MeV - 50 GeV energy range, a SuperAGILE hard X-ray monitor sensitive in the 18–60 keV energy range, a Mini-Calorimeter non-imaging gamma-ray scintillation detector sensitive in the 350 keV - 100 MeV energy range, an Anti-coincidence System, based on a plastic scintillator, to assist with suppressing unwanted background events; the SuperAGILE SA is an instrument based on a set of four silicon strip detectors, each equipped with one-dimensional coded mask. The SA is designed to detect X-Ray signals from burst-like signals.
It provides long-term monitoring of spectral features. MCAL can effectively detect high-energy radiation bursts in its energy band. AGILE was launched on 23 April 2007, from the Indian base of Sriharikota and was inserted in an equatorial orbit with low particle background. On 23 April 2007, ASI made contact with AGILE; some transient events detected by AGILE are associated with positions not consistent with a known source and have cosmological origins. Others are due to solar flares. "AGILE – Gamma Ray Light Detector – Astrorivelatore Gamma ad Immagini LEggero". Carlo Gavazzi Space. Archived from the original on 2007-07-07. "AGILE Launch Campaign". Iasf-bo. Archived from the original on 21 April 2007. "AGILE - Status and recent detections". INAF-IAPS
Small Magellanic Cloud
The Small Magellanic Cloud, or Nubecula Minor, is a dwarf galaxy near the Milky Way. Classified as a dwarf irregular galaxy, the SMC has a diameter of about 7,000 light-years, contains several hundred million stars, has a total mass of 7 billion solar masses; the SMC contains a central bar structure and is speculated to once be a barred spiral galaxy, disrupted by the Milky Way to become somewhat irregular. At a distance of about 200,000 light-years, the SMC is among the nearest intergalactic neighbors of the Milky Way and is one of the most distant objects visible to the naked eye; the SMC is visible from the entire Southern Hemisphere, but can be glimpsed low above the southern horizon from latitudes south of about 15° north. The galaxy is located across both the constellations of Tucana and part of Hydrus, appearing as a faint hazy patch resembling a detached piece of the Milky Way; the SMC has an average diameter of about 4.2° and thus covers an area of about 14 square degrees. Since its surface brightness is low, this deep-sky object is best seen on clear moonless nights and away from city lights.
The SMC forms a pair with the Large Magellanic Cloud, which lies 20° to the east, like the LMC, is a member of the Local Group and probably is a satellite of the Milky Way. In the southern hemisphere, the Magellanic clouds have long been included in the lore of native inhabitants, including south sea islanders and indigenous Australians. Persian astronomer Al Sufi labelled the larger of the two clouds as the White Ox. European sailors may have first noticed the clouds during the Middle Ages when they were used for navigation. Portuguese and Dutch sailors called them the Cape Clouds, a name, retained for several centuries. During the circumnavigation of the Earth by Ferdinand Magellan in 1519–22, they were described by Antonio Pigafetta as dim clusters of stars. In Johann Bayer's celestial atlas Uranometria, published in 1603, he named the smaller cloud, Nubecula Minor. In Latin, Nubecula means a little cloud. Between 1834 and 1838, John Frederick William Herschel made observations of the southern skies with his 14-inch reflector from the Royal Observatory.
While observing the Nubecula Minor, he described it as a cloudy mass of light with an oval shape and a bright center. Within the area of this cloud he catalogued a concentration of clusters. In 1891, Harvard College Observatory opened an observing station at Arequipa in Peru. Between 1893 and 1906, under the direction of Solon Bailey, the 24-inch telescope at this site was used to survey photographically both the Large and Small Magellanic Clouds. Henrietta Swan Leavitt, an astronomer at the Harvard College Observatory, used the plates from Arequipa to study the variations in relative luminosity of stars in the SMC. In 1908, the results of her study were published, which showed that a type of variable star called a "cluster variable" called a Cepheid variable after the prototype star Delta Cephei, showed a definite relationship between the variability period and the star's luminosity; this important period-luminosity relation allowed the distance to any other cepheid variable to be estimated in terms of the distance to the SMC.
Hence, once the distance to the SMC was known with greater accuracy, Cepheid variables could be used as a standard candle for measuring the distances to other galaxies. Using this period-luminosity relation, in 1913 the distance to the SMC was first estimated by Ejnar Hertzsprung. First he measured thirteen nearby cepheid variables to find the absolute magnitude of a variable with a period of one day. By comparing this to the periodicity of the variables as measured by Leavitt, he was able to estimate a distance of 10,000 parsecs between the Sun and the SMC; this proved to be a gross underestimate of the true distance, but it did demonstrate the potential usefulness of this technique. Announced in 2006, measurements with the Hubble Space Telescope suggest the Large and Small Magellanic Clouds may be moving too fast to be orbiting the Milky Way. There is a bridge of gas connecting the Small Magellanic Cloud with the Large Magellanic Cloud, evidence of tidal interaction between the galaxies; the Magellanic Clouds have a common envelope of neutral hydrogen indicating they have been gravitationally bound for a long time.
This bridge of gas is a star-forming site. In 2017, using Dark Energy Survey plus MagLiteS data, a stellar over-density associated with the Small Magellanic Cloud was discovered, the result of interactions between SMC and LMC; the Small Magellanic Cloud contains a active population of X-ray binaries. Recent star formation has led to a large population of massive stars and high-mass X-ray binaries which are the relics of the short-lived upper end of the initial mass function; the young stellar population and the majority of the known X-ray binaries are concentrated in the SMC's Bar. HMXB pulsars are rotating neutron stars in binary systems with Be-type or supergiant stellar companions. Most HMXBs are of the Be type which account for 70% in the Milky Way and 98% in the SMC; the Be-star equatorial disk provides a reservoir of matter that can be accreted onto the neutron star during periastron passage or during large-scale disk ejection episodes. This scenario leads to strings of X-ray outbursts with typical X-ray luminosities Lx = 1036–1037 erg/s, spaced at the orbital period, plus infrequent giant outbursts of greater duration and luminosity.
Monitoring surveys of the SMC performed with NASA's Rossi X-ray Timing Explorer see X-ray pulsars in outburst at more