Syzygy (astronomy)_Syzygy In astronomy, a syzygy (ˈsɪzədʒi ; ) is a roughly straight-line configuration of three or more celestial bodies in a gravitational system. When Earth is one of the bodies involved, the other objects appear to be close together (or overlapping) in the sky. The word is often used in reference to the Sun, Earth, and either the Moon or a planet, where the latter is in conjunction or opposition. Solar and lunar eclipses occur at times of syzygy, as do transits and occultations.
NightNight (also described as nighttime, unconventionally spelled as "nite") is the period of ambient darkness from sunset to sunrise during each 24-hour day, when the Sun is below the horizon. The exact time when night begins and ends depends on the location and varies throughout the year, based on factors such as season and latitude. The word can be used in a different sense as the time between bedtime and morning. In common communication, it is a farewell (sometimes lengthened to "good night"), mainly when someone is going to sleep or leaving.
New moonIn astronomy, the new moon is the first lunar phase, when the Moon and Sun have the same ecliptic longitude. At this phase, the lunar disk is not visible to the naked eye, except when it is silhouetted against the Sun during a solar eclipse. The original meaning of the term 'new moon', which is still sometimes used in calendrical, non-astronomical contexts, is the first visible crescent of the Moon after conjunction with the Sun. This thin waxing crescent is briefly and faintly visible as the Moon gets lower in the western sky after sunset.
Axial parallelismAxial parallelism (also called gyroscopic stiffness, inertia or rigidity, or "rigidity in space") is the characteristic of a rotating body in which the direction of the axis of rotation remains fixed as the object moves through space. In astronomy, this characteristic is found in astronomical bodies in orbit. It is the same effect that causes a gyroscope's axis of rotation to remain constant as Earth rotates, allowing the devices to measure Earth's rotation. The Earth's orbit, with its axis tilted at 23.
PhotosphereThe photosphere is a star's outer shell from which light is radiated. The term itself is derived from Ancient Greek roots, φῶς, φωτός/phos, photos meaning "light" and σφαῖρα/sphaira meaning "sphere", in reference to it being a spherical surface that is perceived to emit light. It extends into a star's surface until the plasma becomes opaque, equivalent to an optical depth of approximately , or equivalently, a depth from which 50% of light will escape without being scattered.
Astronomical filterAn astronomical filter is a telescope accessory consisting of an optical filter used by amateur astronomers to simply improve the details and contrast of celestial objects, either for viewing or for photography. Research astronomers, on the other hand, use various band-pass filters for photometry on telescopes, in order to obtain measurements which reveal objects' astrophysical properties, such as stellar classification and placement of a celestial body on its Wien curve.
Full moonThe full moon is the lunar phase when the Moon appears fully illuminated from Earth's perspective. This occurs when Earth is located between the Sun and the Moon (when the ecliptic longitudes of the Sun and Moon differ by 180°). This means that the lunar hemisphere facing Earth—the near side—is completely sunlit and appears as an approximately circular disk. The full moon occurs roughly once a month. The time interval between a full moon and the next repetition of the same phase, a synodic month, averages about 29.
Lunar standstillA lunar standstill or lunistice is when the moon reaches its furthest north or furthest south point during the course of a month (specifically a draconic month of about 27.2 days). The declination (a celestial coordinate measured as the angle from the celestial equator, analogous to latitude) at lunar standstill varies in a cycle 18.6 years long between 18.134° (north or south) and 28.725° (north or south), due to lunar precession. These extremes are called the minor and major lunar standstills.
Extraterrestrial skyIn astronomy, an extraterrestrial sky is a view of outer space from the surface of an astronomical body other than Earth. The only extraterrestrial sky that has been directly observed and photographed by astronauts is that of the Moon. The skies of Venus, Mars and Titan have been observed by space probes designed to land on the surface and transmit images back to Earth. Characteristics of extraterrestrial sky appear to vary substantially due to a number of factors.
