HE 1327-2326, discovered in 2005 by Anna Frebel and collaborators, was the star with the lowest known iron abundance until SMSS J031300.36−670839.3 was discovered. The star is a member of Population II stars, with a solar-standardised iron to hydrogen index [Fe/H], or metallicity, of −5.4±0.2. The scale being logarithmic, this number indicates that its iron content is about 1/250000 that of the Earth's sun. However, it has a carbon abundance of roughly one-tenth solar, and it is not known how these two abundances can have been produced/exist simultaneously. Discovered by the Hamburg/ESO survey for metal-poor stars, it was probably formed during an age of the universe when the metal content was much lower. It has been speculated that this star is part of the second generation, born out of the gas clouds which were imbued with elements such as carbon by the primordial Population III stars.
HD 202206 is a binary star system in the southern constellation of Capricornus. With an apparent visual magnitude of +8.1, it is too faint to be visible to the naked eye. It is located at a distance of 150 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +14.7 km/s.
BPS CS22892-0052 is an old population II star located at a distance of 4.7 kiloparsecs in the Milky Way's galactic halo. It belongs to a class of ultra-metal-poor stars, specifically the very rare subclass of neutron-capture (r-process) enhanced stars. It was discovered by Tim C. Beers and collaborators with the Curtis Schmidt telescope at the Cerro Tololo Inter-American Observatory in Chile. Extended high-resolution spectroscopic observations since around 1995 allowed observers to determine the abundances of 53 chemical elements in this star, as of December 2005 only second in number to the Sun.
HD 224693, also named Axólotl, is a star in the equatorial constellation of Cetus, and is positioned near the western constellation border with Aquarius. It can be viewed with a small telescope but is too faint to be seen with the naked eye, having an apparent visual magnitude of 8.23. Based on parallax measurements, the object is located at a distance of approximately 306 light years from the Sun. It is drifting further away with a radial velocity of 1.5 km/s.
Przybylski's Star, or HD 101065, is a rapidly oscillating Ap star at roughly 356 light-years from the Sun in the southern constellation of Centaurus. It has a unique spectrum showing over-abundances of most rare-earth elements, including some short-lived radioactive isotopes, but under-abundances of more common elements such as iron.
HE 1523-0901 is the designation given to a red giant star in the Milky Way galaxy approximately 9,900 light-years from Earth. It is thought to be a second generation, Population II, or metal-poor, star ([Fe/H] = −2.95). The star was found in the sample of bright metal-poor halo stars from the Hamburg/ESO Survey by Anna Frebel and collaborators. The group's research was published in the May 10, 2007 issue of The Astrophysical Journal.
HD 136118 is a star in the Serpens Caput section of the Serpens constellation. The star is too dim to be readily visible to the naked eye, having an apparent visual magnitude of 6.93. It is located at a distance of 165 light years from the Sun based on parallax, and is drifting closer with a radial velocity of −3 km/s.
HD 153950 is a star in the southern constellation of Scorpius, positioned about 1.2° to the west of Eta Scorpii. It has the proper name Rapeto, which was selected in the NameExoWorlds campaign by Madagascar, during the 100th anniversary of the IAU. Rapeto is a giant creature from Malagasy tales. This star is visible in a small telescope, having an apparent visual magnitude of 7.39. It is located at a distance of 158 light years from the Sun based on parallax. The star is drifting further away with a radial velocity of 33.2 km/s.
BD+20 2457 is a 10th-magnitude K-type bright giant star located approximately 4,800 light-years away in the constellation of Leo. The name refers to the Bonner Durchmusterung star catalog. This star is very metal-poor, containing only 10% as enriched with elements heavier than hydrogen and helium as the Sun. On June 10, 2009, two planets were announced to be orbiting the star, with minimum masses 21.4 and 12.5 times the mass of Jupiter and orbital periods of 380 and 622 days for the inner and outer planets, respectively. A dynamical analysis reveals that the proposed system is unstable on astronomically short timescales and so the suggested planetary configuration is unlikely to be correct: further data is needed to determine a physically plausible explanation for the radial velocity variations. This conclusion of a dynamical unstable system depends on the planets masses. A later study found lower masses, which could increase the long-term stability. A study from 2021 using Gaia identified BD+20 2457 as a halo star on a retrograde orbit around the Milky Way with a highly eccentric orbit. The researchers constrain the minimum age and the stars upper mass to ≥8 billion years and ≤1 M☉. This decreases the mass of the planets to 13 MJ and 7 MJ. The chemical abundances also suggest that the star formed from the Milky Ways protodisk. As an alternative it could have formed from debris of the Gaia-Enceladus galaxy as it merged with the Milky Way. If BD+20 2457 formed from the Gaia-Enceladus debris, then the star and its planets could have an extragalactic origin.
HD 8535 is a star located 181 light-years away from the Sun in the southern constellation of Phoenix. It has a yellow hue and can be viewed using binoculars or a small telescope, having a low apparent visual magnitude of 7.70. The star is drifting further away from the Sun with a radial velocity of +2.5 km/s.
HD 79498 is a double star in the northern constellation of Cancer. The primary component of this pair has an orbiting exoplanet companion. This star is too faint to be viewed with the naked eye, having an apparent visual magnitude of 8.05. The system is located at a distance of 159 light years based on parallax measurements, and is drifting further away with a heliocentric radial velocity of 20 km/s. It has a relatively high proper motion, traversing the celestial sphere at an angular rate of 0.2″·yr−1.
SDSS J001820.5–093939.2 or SDSS J0018−0939 for short is a star system approximately 1000 light-years away near the constellation Cetus.
Timothy C. Beers is an American astrophysicist. Beers teaches at the University of Notre Dame in the Department of Physics (2014–present), where he holds the Notre Dame Chair in Astrophysics. He is a co-founder of the Physics Frontier Center Joint Institute for Nuclear Astrophysics – Center for the Evolution of the Elements. Prior to coming to Notre Dame, Beers was Director of Kitt Peak National Observatory (2011-2014), and for 25 years was a professor in the Department of Physics and Astronomy at Michigan State University (1986-2011), retiring from that position as University Distinguished Professor.
2MASS J18082002−5104378 is an ultra metal-poor (UMP) binary star system, in the constellation Ara, about 1,950 ly (600 pc) from Earth, and is a single-lined spectroscopic binary (SB1). It is one of the oldest stars known, about 13.53 billion years old, possibly one of the first stars, a star made almost entirely of materials released from the Big Bang. A tiny unseen companion, a low-mass UMP star, is particularly unusual.
Antlia II is a low-surface-brightness dwarf satellite galaxy of the Milky Way at a galactic latitude of 11.2°. It spans 1.26° in the sky just southeast of Epsilon Antliae. The galaxy is similar in size to the Large Magellanic Cloud, despite being 1/10,000 as bright. Antlia II has the lowest surface brightness of any galaxy discovered and is ~ 100 times more diffuse than any known ultra diffuse galaxy. The large size of the galaxy suggests that it is currently being tidally disrupted, and is in the process of becoming a stellar stream. The southeast side of Antlia II is farther away than the northwest side, likely due to the tidal disruption. It was discovered using data from the European Space Agency's Gaia spacecraft in November 2018.
HD 128429 is a binary star system located at a distance of 88 light years from the Sun in the southern zodiac constellation of Libra. It has a yellow-white hue and is just barely visible to the naked eye with an apparent visual magnitude of 6.20. The system is drifting closer to the Sun with a radial velocity of −66 km/s and has a high proper motion, traversing the celestial sphere at the rate of 0.945″ per year. It is a well-known high velocity star system with a net heliocentric velocity of 158.8 km/s. The system is orbiting the through the galaxy with a high eccentricity of 0.62, which carries it from as close as 4.1 out to 17.5 kpc away from the Galactic Center.
Price-Whelan 1 is a young stellar association or disrupting star cluster with low metallicity and extragalactic origin, more specifically the leading arm of the Magellanic gas stream originating in the Magellanic Clouds. Price-Whelan 1 was discovered by Adrian Price-Whelan using Gaia data and additional cluster members were identified using DECam data. The star cluster contains less than a thousand stars. The existence of Price-Whelan 1 suggests that the stream of gas extending from the Magellanic Clouds to our Milky Way is about half as far from the Milky Way as previously thought.
HD 7449 is a binary star system about 126 light-years way. The primary star, HD 7449 A, is a main-sequence star belonging to the spectral class F9.5. It is younger than the Sun. The primary star is slightly depleted of heavy elements, having 80% of solar abundance.
HD 72945 and HD 72946 form a co-moving star system in the northern constellation of Cancer. HD 72945 is a binary star that is dimly visible to the naked eye as a point of light with an apparent visual magnitude of 5.91. At an angular separation of 10.10″ is the fainter companion star HD 72946 at magnitude 7.25. It is being orbited by a brown dwarf. The system as a whole is located at a distance of approximately 84 light years from the Sun based on parallax measurements.
HE 1219-0312 is an extremely metal-poor star in the constellation Virgo, The star is located at around 41,400 light years away from earth.
