Algol, designated Beta Persei, known colloquially as the Demon Star, is a bright multiple star in the constellation of Perseus and one of the first non-nova variable stars to be discovered.
Canis Major is a constellation in the southern celestial hemisphere. In the second century, it was included in Ptolemy's 48 constellations, and is counted among the 88 modern constellations. Its name is Latin for "greater dog" in contrast to Canis Minor, the "lesser dog"; both figures are commonly represented as following the constellation of Orion the hunter through the sky. The Milky Way passes through Canis Major and several open clusters lie within its borders, most notably M41.
Lyra is a small constellation. It is one of the 48 listed by the 2nd century astronomer Ptolemy, and is one of the modern 88 constellations recognized by the International Astronomical Union. Lyra was often represented on star maps as a vulture or an eagle carrying a lyre, and hence is sometimes referred to as Vultur Cadens or Aquila Cadens, respectively. Beginning at the north, Lyra is bordered by Draco, Hercules, Vulpecula, and Cygnus. Lyra is nearly overhead in temperate northern latitudes shortly after midnight at the start of summer. From the equator to about the 40th parallel south it is visible low in the northern sky during the same months.
A binary star is a system of two stars that are gravitationally bound to and in orbit around each other. Binary stars in the night sky that are seen as a single object to the naked eye are often resolved using a telescope as separate stars, in which case they are called visual binaries. Many visual binaries have long orbital periods of several centuries or millennia and therefore have orbits which are uncertain or poorly known. They may also be detected by indirect techniques, such as spectroscopy or astrometry. If a binary star happens to orbit in a plane along our line of sight, its components will eclipse and transit each other; these pairs are called eclipsing binaries, or, together with other binaries that change brightness as they orbit, photometric binaries.
A variable star is a star whose brightness as seen from Earth fluctuates.
In astronomy, a semiregular variable star, a type of variable star, is a giant or supergiant of intermediate and late (cooler) spectral type showing considerable periodicity in its light changes, accompanied or sometimes interrupted by various irregularities. Periods lie in the range from 20 to more than 2000 days, while the shapes of the light curves may be rather different and variable with each cycle. The amplitudes may be from several hundredths to several magnitudes.
In astronomy, a contact binary is a binary star system whose component stars are so close that they touch each other or have merged to share their gaseous envelopes. A binary system whose stars share an envelope may also be called an overcontact binary. The term "contact binary" was introduced by astronomer Gerard Kuiper in 1941. Almost all known contact binary systems are eclipsing binaries; eclipsing contact binaries are known as W Ursae Majoris variables, after their type star, W Ursae Majoris.
Perseus is a constellation in the northern sky, being named after the Greek mythological hero Perseus. It is one of the 48 ancient constellations listed by the 2nd-century astronomer Ptolemy, and among the 88 modern constellations defined by the International Astronomical Union (IAU). It is located near several other constellations named after ancient Greek legends surrounding Perseus, including Andromeda to the west and Cassiopeia to the north. Perseus is also bordered by Aries and Taurus to the south, Auriga to the east, Camelopardalis to the north, and Triangulum to the west. Some star atlases during the early 19th century also depicted Perseus holding the disembodied head of Medusa, whose asterism was named together as Perseus et Caput Medusae; however, this never came into popular usage.
Musca is a small constellation in the deep southern sky. It was one of 12 constellations created by Petrus Plancius from the observations of Pieter Dirkszoon Keyser and Frederick de Houtman, and it first appeared on a celestial globe 35 cm (14 in) in diameter published in 1597 in Amsterdam by Plancius and Jodocus Hondius. The first depiction of this constellation in a celestial atlas was in Johann Bayer's Uranometria of 1603. It was also known as Apis for 200 years. Musca remains below the horizon for most Northern Hemisphere observers.
Beta Lyrae officially named Sheliak, the traditional name of the system, is a multiple star system in the constellation of Lyra. Based on parallax measurements obtained during the Hipparcos mission, it is approximately 960 light-years distant from the Sun.
Epsilon Aurigae is a multiple star system in the northern constellation of Auriga, the charioteer. It is an unusual eclipsing binary system comprising an F0 supergiant and a companion which is generally accepted to be a huge dark disk orbiting an unknown object, possibly a binary system of two small B-type stars. The distance to the system is still a subject of debate, but data from the Gaia spacecraft puts its distance at around 1,350±300 light years from Earth.
Upsilon Sagittarii is a spectroscopic binary star system in the constellation Sagittarius. Upsilon Sagittarii is the prototypical hydrogen-deficient binary (HdB), and one of only four such systems known. The unusual spectrum of hydrogen-deficient binaries has made stellar classification of Upsilon Sagittarii difficult.
Lambda Tauri is a triple star system in the constellation Taurus. In the Calendarium of Al Achsasi Al Mouakket, this star was designated Sadr al Tauri, which was translated into Latin as Pectus Tauri, meaning "the bull chest". In 1848, the light from this system was found to vary periodically and it was determined to be an eclipsing binary system—the third such discovered. The components of this system have a combined apparent visual magnitude of +3.37 at its brightest, making it one of the brighter members of the constellation. Based upon parallax measurements from the Hipparcos mission, the distance to this system is approximately 480 light-years.
The following outline is provided as an overview of and topical guide to astronomy:
Algol variables or Algol-type binaries are a class of eclipsing binary stars that are similar to the prototype member of this class, β Persei. An Algol binary is a system where both stars are near-spherical such that the timing of the start and end of the eclipses is well-defined. The primary is generally a main sequence star well within its Roche lobe. The secondary may also be a main sequence star, referred to as a detached binary or it may an evolved star filling its Roche lobe, referred to as a semidetached binary.
Epsilon Persei, Latinized from ε Persei, is a multiple star system in the northern constellation of Perseus. It has a combined apparent visual magnitude of +2.88, which is bright enough to be viewed with the naked eye. Based upon parallax measurements, this system is located at a distance of roughly 640 light-years (196 parsecs) from Earth.
Delta Pictoris, Latinized from δ Pictoris, is a binary star system in the southern constellation Pictor. It is visible to the naked with a combined apparent visual magnitude of 4.72. The system is located at a distance of approximately 1,300 light years from the Sun based on parallax measurements, and is drifting further away with a radial velocity of ~31 km/s. It is a runaway star system that is generating a bow shock as it moves through the interstellar medium.
QZ Carinae is a multiple star system in the constellation Carina. It is the brightest member of the loose open cluster Collinder 228 and one of the brightest stars in the Carina Nebula. The apparent magnitude is variable from +6.16 to +6.49 with a period of 6 days.
A Double Periodic Variable (DPV) is a type of binary star. As the name implies, the systems vary in brightness not only due to eclipses of one star by the other, but also on a cycle of roughly 33 times longer than the orbit. The star gaining mass from the other has a thick disk of material surrounding it, and the systems apparently lose mass cyclically into the interstellar medium over time. The cause for the secondary longer variability still is not established, but it has been proposed to be linked to a magnetic dynamo in the donor star. A famous example is β Lyrae. The stars are rare, with 21 systems found in the Galaxy and more than 170 in the Magellanic Clouds.
Psi2 Orionis a binary star system in the equatorial constellation of Orion. It has an apparent visual magnitude of 4.6, indicating that it is visible to the naked eye. Based upon an annual parallax shift of 2.87 mass, it is roughly 1,100 light years distant from the Sun.
