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| Sagittarius B | |
|---|---|
| Name | Sagittarius B |
| Type | Molecular cloud complex |
| Constellation | Sagittarius |
| Epoch | J2000 |
| Distance | ~8 kpc |
| Mass | ~10^6 M☉ |
| Coordinates | RA 17h47m, Dec −28°23′ (approx.) |
Sagittarius B Sagittarius B is a massive molecular cloud complex near the center of the Milky Way that hosts intense star formation, complex chemistry, and numerous compact sources. The region lies close to the Galactic Center and is associated with prominent radio, infrared, submillimeter, and X-ray emission tied to high-mass star formation and an active interstellar medium. Observations across facilities and surveys have revealed a rich interplay among dense cores, hot cores, masers, and nonthermal structures.
Sagittarius B occupies a sector of the Central Molecular Zone adjacent to the supermassive black hole Sagittarius A*, in the direction of the constellation Sagittarius. It is often subdivided into major subcomplexes that include massive star-forming sites, dense molecular gas, and energetic feedback traced by instruments such as the Very Large Array, the Atacama Large Millimeter/submillimeter Array, the Hubble Space Telescope, the Chandra X-ray Observatory, and the Spitzer Space Telescope. Studies of the region involve teams and programs from institutions like the Max Planck Institute for Radio Astronomy, the National Radio Astronomy Observatory, the European Southern Observatory, and the Harvard-Smithsonian Center for Astrophysics.
The complex contains extensive dense gas reservoirs with masses estimated by surveys using the James Clerk Maxwell Telescope, the IRAM 30m telescope, and the Green Bank Telescope. Substructures include compact hot cores, extended envelopes, and filamentary gas shaped by tidal forces from the central potential of the Milky Way and by feedback from young massive clusters studied by groups at the Royal Observatory Edinburgh and the Institute of Astronomy, Cambridge. Prominent subregions identified in maps from the Submillimeter Array and the Herschel Space Observatory are associated with strong dust continuum and molecular line emission. Embedded clusters and cores are cataloged using data from the Two Micron All Sky Survey, the Wide-field Infrared Survey Explorer, and the VISTA Variables in the Via Lactea survey.
Star formation in the complex produces high-mass protostars, ultracompact H II regions, and clusters traced by radio recombination lines observed with the Very Large Array and maser emission from species detected by the Australia Telescope Compact Array and the Effelsberg 100-m Radio Telescope. The chemistry is extraordinarily rich, with detections of complex organic molecules reported by teams using the IRAM Plateau de Bure Interferometer, the ALMA Partnership, and the Nobeyama Radio Observatory. Molecular inventories include species mapped by surveys with the Mopra Telescope, the Green Bank Ammonia Survey, and projects led from the Max Planck Institute for Extraterrestrial Physics. Shock tracers, ionized gas tracers, and hot-core molecules reveal energetic processing linked to outflows cataloged by researchers at the Jet Propulsion Laboratory and the National Astronomical Observatory of Japan.
Early radio continuum studies with the Cambridge Radio Telescope and the Parkes Observatory first highlighted bright emission; subsequent millimeter and submillimeter line surveys by the Cologne Database for Molecular Spectroscopy collaborators and teams using the Smithsonian Astrophysical Observatory facilities expanded the molecular census. Infrared detections were advanced by the Infrared Astronomical Satellite and later by the Spitzer Space Telescope, while high-resolution X-ray imaging from the Chandra X-ray Observatory and the XMM-Newton observatory exposed energetic sources and diffuse emission. Long-term monitoring by arrays such as the Very Long Baseline Array and campaigns involving the European VLBI Network have mapped maser motions, and spectroscopic work by staff at the Institute for Radio Astronomy in the Millimeter Range refined velocity structures.
The complex is situated near the dynamical center of the Milky Way at a distance consistent with measurements to central objects like Sagittarius A* and masers tied to the Galactic Center. Parallax and kinematic estimates from the Bar and Spiral Structure Legacy Survey and the BeSSeL Survey place it at a distance of roughly 8 kiloparsecs, comparable to determinations from studies of the Galactic Center GeV excess region and investigations by researchers at the Max Planck Institute for Astronomy.
Sagittarius B contributes to the mass budget, star formation activity, and chemical enrichment of the Central Molecular Zone studied by collaborations involving the Leiden Observatory, the University of Bonn, and the University of Colorado Boulder. Its interaction with large-scale features such as the Central Molecular Zone ring, the Nuclear Stellar Cluster, and nonthermal filaments influences feedback processes examined in works tied to the Galactic Center Survey and theoretical modeling by groups at the Princeton Plasma Physics Laboratory and the Institute for Advanced Study.
Prominent compact and extended sources cataloged in the region include ultracompact H II regions, hot molecular cores, maser spots, and X-ray objects identified in surveys by the Very Large Array, the Atacama Pathfinder Experiment, the Chandra X-ray Observatory, and the Suzaku satellite. Individual objects have been targets for studies by teams affiliated with the Harvard-Smithsonian Center for Astrophysics, the Max Planck Institute for Radio Astronomy, and the European Southern Observatory to probe massive star formation, astrochemistry, and feedback on parsec scales.