A post-common envelope binary is a type of binary star system that evolves from an earlier stage known as a common envelope phase. In a binary star system, two stars orbit around a common center of mass. When one of the stars expands significantly—often as it evolves off the main sequence—it can engorge its companion within its outer layers, creating a common envelope of gas that surrounds both stars.

The term "Polar" can refer to several different things, but in the context of astronomy, it most commonly refers to Polaris, which is the North Star. Polaris is located nearly directly above the North Pole, making it a key reference point for navigation in the Northern Hemisphere. Here are some key points about Polaris: 1. **Location**: Polaris is situated in the constellation Ursa Minor, also known as the Little Dipper. It is the final star in the handle of this constellation.

PSR B0943+10 is a pulsar, which is a highly magnetized, rotating neutron star that emits a beam of electromagnetic radiation. As the neutron star rotates, this beam can be observed from Earth as it sweeps across our line of sight, producing a series of pulses, typically in the radio wavelength. Discovered in 1968, PSR B0943+10 is notable within the pulsar community for several reasons.

The term "Nova" can refer to several different concepts depending on the context. Here are a few notable references: 1. **Astronomy**: In an astronomical context, a nova is a cataclysmic nuclear explosion on the surface of a white dwarf star. It can cause a sudden increase in brightness, sometimes making the nova visible from Earth even if it was previously too dim to see.

A Moreton wave is a type of wave observed in the solar atmosphere, specifically associated with solar flares and coronal mass ejections (CMEs). It is characterized by a propagating disturbance in the solar corona, which can manifest as a sudden increase in brightness in the ultraviolet and X-ray wavelengths. Moreton waves are named after the astronomer David Moreton, who studied these phenomena.

A micromova is a small-scale explosive event that occurs on the surface of a star, similar to a supernova but much less energetic. These phenomena are typically associated with specific types of stars, such as white dwarfs or other stellar remnants, where the conditions for nuclear fusion or other reactions can lead to localized explosions.

Magnetic reconnection is a fundamental process in plasma physics that occurs when magnetic field lines from different magnetic domains converge, break, and reconnect in a new configuration. This phenomenon is particularly significant in astrophysical and space contexts, such as in the Sun's corona, Earth’s magnetosphere, and in fusion research. In more detail, magnetic reconnection can be described as follows: 1. **Configuration**: It typically involves two oppositely directed magnetic fields.

A magnetar is a type of neutron star that has an extremely strong magnetic field, typically on the order of 10^11 to 10^15 gauss, which is a thousand times stronger than that of a typical neutron star and about a billion times stronger than that of Earth. These intense magnetic fields are produced by the rapid rotation and collapse of massive stars during supernova events.

A luminous red nova (LRN) is a type of astronomical event that represents a specific kind of stellar explosion or outburst. These events are characterized by an initial brightening followed by a gradual fading, and they are typically accompanied by significant changes in the light spectrum of the star. LRNs are thought to occur in binary star systems, where material from one star is transferred to another, leading to the eventual destabilization and explosion of the system.

Stellar explosions come in various forms, primarily associated with the life cycles of stars.

Limb darkening is an effect observed in the spectra and brightness of celestial bodies, particularly stars and planets. It refers to the phenomenon where the edges (or "limbs") of a star or planet appear darker than the center when viewed in terms of brightness or intensity. This effect arises due to the temperature gradient in the outer layers of a star. The center of the star is generally hotter and emits more light than the outer edges or "limbs.

A kilonova is an astronomical event that occurs when two neutron stars (or a neutron star and a black hole) merge. This extreme event produces a significant amount of energy and is characterized by a rapid increase in brightness, typically lasting from a few days to weeks. Kilonovae are expected to be a source of heavy elements such as gold and platinum, as the collision releases an intense amount of energy in the form of gravitational waves and electromagnetic radiation.

Intermediate polars, also known as "IP" stars, are a specific class of cataclysmic variables, which are binary star systems consisting of a white dwarf and a companion star (usually a red dwarf). In these systems, the white dwarf has a strong magnetic field, which influences the accretion of material from the companion star onto the white dwarf.

Intermediate luminosity optical transients (ILOTs) refer to a class of astronomical events characterized by significant increases in optical brightness over relatively short timescales, typically lasting from days to weeks. These transients are believed to occur in a variety of contexts, but they are often associated with the explosive or eruptive activity of massive stars, particularly those in the later stages of their evolution.

Hypergiant is a term that can refer to several different concepts, so context is important. In a literal astronomical sense, a hypergiant star is a very massive star that is much larger than a typical giant star. These stars have exceptionally high luminosity and can have masses ranging from about 25 to 100 times that of the Sun.

Helioseismology is the study of the structure and dynamics of the Sun through the observation of waves propagating within it. By analyzing these oscillations, which are caused by various types of waves (acoustic, gravity, and surface waves), scientists can gain insights into the Sun's internal structure, including temperature, density, and composition.

Gravity darkening is a phenomenon in astrophysics that describes how the brightness of a star varies across its surface due to the effects of gravity. This effect is most pronounced in rotating stars, where the centrifugal force caused by rotation causes the star to become oblate, meaning it is flattened at the poles and bulging at the equator. In such stars, the gravitational field strength is not uniform across the surface; it is stronger at the poles and weaker at the equator.

A gamma-ray burst (GRB) is an extremely energetic explosion that occurs in distant galaxies, characterized by the emission of intense gamma rays. These bursts are among the most luminous events known in the universe and can release more energy in a few seconds than the Sun will emit over its entire 10-billion-year lifetime.

GPM J1839−10 is a millisecond pulsar located in the direction of the constellation Scorpius. It was discovered as part of the Galactic Pulsar Monitor (GPM) project, which aims to monitor and catalog pulsars in our galaxy. Millisecond pulsars are highly magnetized, rotating neutron stars that emit beams of electromagnetic radiation out of their magnetic poles.

"Facula" is a term used in astronomy and planetary science to refer to bright or reflective spots on the surface of celestial bodies, primarily on the Moon and planets. These features typically consist of relatively high-albedo material, which means they reflect more sunlight than their surrounding areas. On the Moon, faculae are often associated with impact craters and volcanic activity. They can be found in both the dark, basaltic plains (maria) as well as the bright highlands.