Ross 154 is a star in the southern zodiac constellation of Sagittarius. It has an apparent visual magnitude of 10.44, making it much too faint to be seen with the naked eye. At a minimum, viewing Ross 154 requires a telescope with an aperture of 6.5 cm (3 in) under ideal conditions. The distance to this star can be estimated from parallax measurements, which places it at 9.71 light-years away from Earth. It is the nearest star in the southern constellation Sagittarius, and one of the nearest stars to the Sun.
The Galactic Center is the rotational center, the barycenter, of the Milky Way galaxy. Its central massive object is a supermassive black hole of about 4 million solar masses, which is called Sagittarius A*, a compact radio source which is almost exactly at the galactic rotational center. The Galactic Center is approximately 8 kiloparsecs (26,000 ly) away from Earth in the direction of the constellations Sagittarius, Ophiuchus, and Scorpius, where the Milky Way appears brightest, visually close to the Butterfly Cluster (M6) or the star Shaula, south to the Pipe Nebula.
An intermediate-mass black hole (IMBH) is a class of black hole with mass in the range 102–105 solar masses: significantly more than stellar black holes but less than the 105–109 solar mass supermassive black holes. Several IMBH candidate objects have been discovered in the Milky Way galaxy and others nearby, based on indirect gas cloud velocity and accretion disk spectra observations of various evidentiary strength.
Sagittarius A*, abbreviated Sgr A*, is the supermassive black hole at the Galactic Center of the Milky Way. It is located near the border of the constellations Sagittarius and Scorpius, about 5.6° south of the ecliptic, visually close to the Butterfly Cluster (M6) and Lambda Scorpii.
R Monocerotis, abbreviated R Mon, is a very young binary star system in the equatorial constellation of Monoceros. The apparent magnitude of R Mon varies between 10 and 12 and the spectral type is B8IIIe.
The Milky Way has several smaller galaxies gravitationally bound to it, as part of the Milky Way subgroup, which is part of the local galaxy cluster, the Local Group.
KW Sagittarii is a red supergiant, located approximately 1,900 parsecs away from the Sun in the direction of the constellation Sagittarius. It is one of the largest-known stars. If placed at the center of the Solar System, the star's surface would engulf Mars.
NGC 5986 is a globular cluster of stars in the southern constellation of Lupus, located at a distance of approximately 34 kilolight-years from the Sun. It was discovered by Scottish astronomer James Dunlop on May 10, 1826. John L. E. Dreyer described it as, "a remarkable object, a globular cluster, very bright, large, round, very gradually brighter middle, stars of 13th to 15th magnitude". Its prograde–retrograde orbit through the Milky Way galaxy is considered irregular and highly eccentric. It has a mean heliocentric radial velocity of +100 km/s. The galacto-centric distance is 17 kly (5.2 kpc), which puts it in the galaxy's inner halo.
NGC 6723 is a globular cluster in the constellation Sagittarius. Its magnitude is given as between 6 and 6.8, and its diameter is between 7 and 11 arcminutes. It is a class VII cluster with stars of magnitude 14 and dimmer. It is near the border of Sagittarius and Corona Australis.
S2, also known as S0–2, is a star in the star cluster close to the supermassive black hole Sagittarius A* (Sgr A*), orbiting it with a period of 16.0518 years, a semi-major axis of about 970 au, and a pericenter distance of 17 light hours – an orbit with a period only about 30% longer than that of Jupiter around the Sun, but coming no closer than about four times the distance of Neptune from the Sun. The mass when the star first formed is estimated by the European Southern Observatory (ESO) to have been approximately 14 M☉. Based on its spectral type, it probably has a mass of 10 to 15 solar masses.
VX Sagittarii is an asymptotic giant branch star located more than 1.5 kiloparsec away from the Sun in the constellation of Sagittarius. It is a pulsating variable star with an unusually large magnitude range. It is one of the largest stars discovered, with a radius varying between 1,350 and 1,940 solar radii (940,000,000 and 1.35×109 km; 6.3 and 9.0 au). It is the most luminous known AGB star, at bolometric magnitude –8.6, which is brighter than the theoretical limit at –8.0.
Y Sagittarii is a variable star in the constellation of Sagittarius. It is a Cepheid variable with an apparent magnitude that ranges around +5.77. The measure of its parallax by Hubble Space Telescope puts Y Sagittarii to 1,293 light-years away from the Solar System.
S55 is a star that is located very close to the centre of the Milky Way, near the radio source Sagittarius A*, orbiting it with an orbital period of 12.8 years. Until 2019, when the star S62 became the new record holder, it was the star with the shortest known period orbiting the black hole at the centre of the Milky Way. This beat the record of 16 years previously set by S2. The star was identified by a University of California, Los Angeles team headed by Andrea M. Ghez. At its periapsis, its speed reaches 1.7% of the speed of light. At that point it is 246 astronomical units from the centre, while the black hole radius is only a small fraction of that size. It passed that point in 2009 and will be there again in 2022.
The Central Molecular Zone or CMZ is a region of the Milky Way Galaxy rich in an estimated 60 million solar masses (M☉) of gas within a complex of giant molecular clouds. It spans the centre of the Milky Way, and as such is in the Sagittarius constellation, between galactic longitude 1.7° and -0.7°, and latitudes -0.2° and +0.2°.
V4743 Sagittarii was a bright nova in the southern constellation of Sagittarius. This event was discovered by K. Haseda and colleagues in September 2002. It peaked at magnitude 5.0 on September 20, 2002, then declined rapidly thereafter. It reached a peak temperature of 740,000 K around April 2003 and remained at that level for at least five months, suggesting the white dwarf component has a mass of 1.1–1.2 M☉. The distance to this system is uncertain. Infrared observations indicate a distance of approximately 21 kly (6.3 kpc). A derivation using maximum magnitude rate of decay showed a distance of 12.7 ± 1.0 kly (3.9 ± 0.3 kpc).
GW Orionis is a T Tauri type pre-main sequence hierarchical triple star system. It is associated with the Lambda Orionis star-forming region and has an extended circumtrinary protoplanetary disk.
S62 is a star in the cluster surrounding Sagittarius A*, the supermassive black hole in the center of the Milky Way. S62 orbits Sgr A* in 9.9 years, the shortest known orbital period of any star around Sgr A*. The previous record holder, S55 has a 12.8-year period.
GCIRS 16SW, also known as S97, is a contact binary star located in the Galactic Center. It is composed of two hot massive stars of equal size that orbit each other with a period of 19.5 days. The stars are so close that their atmospheres overlap, and the two stars form an eclipsing binary varying in brightness by 0.35 magnitudes at infrared wavelengths.
S4716 is an S star located at the center of the Milky Way galaxy orbiting the supermassive blackhole Sgr A* at the speed of 8,000 kilometres per second in closest approach of 100 AU. As of July 2022, the orbital period of S4716 was the shortest known of any star in the Milky Way galaxy. It orbits the Sgr A* in 4.0 years, on an elliptical orbit with an eccentricity of 0.75. Its closest approach to Sgr A* is 15 billion kilometers, while its farthest approach is 100 billion kilometers. The star can be detected by NIRC2 (Keck), OSIRIS (Keck), SINFONI (VLT), NACO (VLT) and GRAVITY (VLT).
U Sagittarii is a variable star in the southern constellation of Sagittarius, abbreviated U Sgr. It is a classical Cepheid variable that ranges in brightness from an apparent visual magnitude of 6.28 down to 7.15, with a pulsation period of 6.745226 days. At its brightest, this star is dimly visible to the naked eye. The distance to this star is approximately 2,080 light years based on parallax measurements, and it is drifting further away with a radial velocity of 2 km/s.
