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.
Mass transfer is the net movement of mass from one location, usually meaning stream, phase, fraction or component, to another. Mass transfer occurs in many processes, such as absorption, evaporation, drying, precipitation, membrane filtration, and distillation. Mass transfer is used by different scientific disciplines for different processes and mechanisms. The phrase is commonly used in engineering for physical processes that involve diffusive and convective transport of chemical species within physical systems.
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.
Cataclysmic variable stars (CV) are stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state. They were initially called novae, from the Latin 'new', since ones with an outburst brightness visible to the naked eye and an invisible quiescent brightness appeared as new stars in the sky.
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.
The Roche lobe is the region around a star in a binary system within which orbiting material is gravitationally bound to that star. It is an approximately teardrop-shaped region bounded by a critical gravitational equipotential, with the apex of the teardrop pointing towards the other star (the apex is at the L1 Lagrangian point of the system).
X-ray binaries are a class of binary stars that are luminous in X-rays. The X-rays are produced by matter falling from one component, called the donor, to the other component, called the accretor, which is very compact: a neutron star or black hole. The infalling matter releases gravitational potential energy, up to several tenths of its rest mass, as X-rays. The lifetime and the mass-transfer rate in an X-ray binary depends on the evolutionary status of the donor star, the mass ratio between the stellar components, and their orbital separation.
X-ray bursters are one class of X-ray binary stars exhibiting periodic and rapid increases in luminosity that peak in the X-ray regime of the electromagnetic spectrum. These astrophysical systems are composed of an accreting compact object, and a main sequence companion 'donor' star. A compact object in an X-ray binary system consists of either a neutron star or a black hole; however, with the emission of an X-ray burst, the companion star can immediately be classified as a neutron star, since black holes do not have a surface and all of the accreting material disappears past the event horizon. The donor star's mass falls to the surface of the neutron star where the hydrogen fuses to helium which accumulates until it fuses in a burst, producing X-rays.
Tau Canis Majoris is a multiple star system in the constellation Canis Major. It is approximately 5,000 light years distant from Earth and is the brightest member of the open cluster NGC 2362.
UW Canis Majoris is a star in the constellation Canis Major. It is classified as a Beta Lyrae eclipsing contact binary and given the variable star designation UW Canis Majoris. Its brightness varies from magnitude +4.84 to +5.33 with a period of 4.39 days. Bode had initially labelled it as Tau2 Canis Majoris, but this designation had been dropped by Gould and subsequent authors.
Algol variables or Algol-type binaries are a class of eclipsing binary stars that are related to the prototype member of this class, β Persei from an evolutionary point of view. An Algol binary is a semidetached binary system where the primary component is an early type, main sequence star that does not fill its Roche lobe, while the cooler, fainter, larger, less massive secondary component lies above the main sequence in a Hertzsprung–Russell diagram and fills the Roche lobe. Early in its history, the secondary star would have been more massive, evolving first to overfill its Roche lobe. After rapid mass exchange, the lobe-filling star became less massive than its companion.
A Polar is a highly magnetic type of cataclysmic variable binary star system, originally known as an AM Herculis star after the prototype member AM Herculis. Like other cataclysmic variables (CVs), polars contain two stars: an accreting white dwarf (WD), and a low-mass donor star which is transferring mass to the WD as a result of the WD's gravitational pull, overflowing its Roche lobe. Polars are distinguished from other CVs by the presence of a very strong magnetic field in the WD. Typical magnetic field strengths of polar systems are 10 million to 80 million gauss. The WD in the polar AN Ursae Majoris has the strongest known magnetic field among cataclysmic variables, with a field strength of 230 million gauss.
A U Geminorum-type variable star, or dwarf nova is one of several types of cataclysmic variable star, consisting of a close binary star system in which one of the components is a white dwarf that accretes matter from its companion. Dwarf novae are dimmer and repeat more frequently than "classical" novae.
A symbiotic binary is a type of binary star system, often simply called a symbiotic star. They usually contain a white dwarf with a companion red giant. The cool giant star loses material via Roche lobe overflow or through its stellar wind, which flows onto the hot compact star, usually via an accretion disk.
Z Canis Majoris (Z CMa) is a B-type star in the constellation of Canis Major. It has an average apparent visual magnitude of approximately 9.85, though has brightened by 1-2 magnitudes in irregular outbursts in 1987, 2000, 2004 and 2008.
An AM Canum Venaticorum star, is a rare type of cataclysmic variable star named after their type star, AM Canum Venaticorum. In these hot blue binary variables, a white dwarf accretes hydrogen-poor matter from a compact companion star.
A luminous supersoft X-ray source is an astronomical source that emits only low energy X-rays. Soft X-rays have energies in the 0.09 to 2.5 keV range, whereas hard X-rays are in the 1–20 keV range. SSSs emit few or no photons with energies above 1 keV, and most have effective temperature below 100 eV. This means that the radiation they emit is highly ionizing and is readily absorbed by the interstellar medium. Most SSSs within our own galaxy are hidden by interstellar absorption in the galactic disk. They are readily evident in external galaxies, with ~10 found in the Magellanic Clouds and at least 15 seen in M31.
R Canis Majoris is an eclipsing interacting binary star system in the constellation Canis Major. It varies from magnitude 5.7 to 6.34. The system is unusual in the low ratio between the main two components and shortness of the orbital period.
AN Ursae Majoris is a binary star system in the northern circumpolar constellation of Ursa Major. It is a variable star, with AN Ursae Majoris being the variable star designation, and ranges in brightness from 14.90 down to 20.2. Even at its peak brightness though, the system is much to faint to be visible to the naked eye. Based on parallax measurements, the system is located roughly 1,050 light years away from the Sun.
