Galactic astronomy
Encyclopedia
Galactic astronomy is the study of our own Milky Way
galaxy and all its contents. This is in contrast to extragalactic astronomy
, which is the study of everything outside our galaxy, including all other galaxies.
Galactic astronomy should not be confused with galaxy formation and evolution
, which is the general study of galaxies
, their formation, structure, components, dynamics, interactions, and the range of forms they take.
Our own Milky Way
galaxy, where our solar system
belongs, is in many ways the best studied galaxy, although important parts of it are obscured from view in visible wavelength
s by regions of cosmic dust
. The development of radio astronomy
, infrared astronomy
and submillimeter astronomy in the 20th Century allowed the gas and dust of the Milky Way to be mapped for the first time.
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
galaxy and all its contents. This is in contrast to extragalactic astronomy
Extragalactic astronomy
Extragalactic astronomy is the branch of astronomy concerned with objects outside our own Milky Way Galaxy. In other words, it is the study of all astronomical objects which are not covered by galactic astronomy, the next level of galactic astronomy....
, which is the study of everything outside our galaxy, including all other galaxies.
Galactic astronomy should not be confused with galaxy formation and evolution
Galaxy formation and evolution
The study of galaxy formation and evolution is concerned with the processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time, and the processes that have generated the variety of structures observed in nearby...
, which is the general study of galaxies
Galaxy
A galaxy is a massive, gravitationally bound system that consists of stars and stellar remnants, an interstellar medium of gas and dust, and an important but poorly understood component tentatively dubbed dark matter. The word galaxy is derived from the Greek galaxias , literally "milky", a...
, their formation, structure, components, dynamics, interactions, and the range of forms they take.
Our own Milky Way
Milky Way
The Milky Way is the galaxy that contains the Solar System. This name derives from its appearance as a dim un-resolved "milky" glowing band arching across the night sky...
galaxy, where our solar system
Solar System
The Solar System consists of the Sun and the astronomical objects gravitationally bound in orbit around it, all of which formed from the collapse of a giant molecular cloud approximately 4.6 billion years ago. The vast majority of the system's mass is in the Sun...
belongs, is in many ways the best studied galaxy, although important parts of it are obscured from view in visible wavelength
Wavelength
In physics, the wavelength of a sinusoidal wave is the spatial period of the wave—the distance over which the wave's shape repeats.It is usually determined by considering the distance between consecutive corresponding points of the same phase, such as crests, troughs, or zero crossings, and is a...
s by regions of cosmic dust
Cosmic dust
Cosmic dust is a type of dust composed of particles in space which are a few molecules to 0.1 µm in size. Cosmic dust can be further distinguished by its astronomical location; for example: intergalactic dust, interstellar dust, interplanetary dust and circumplanetary dust .In our own Solar...
. The development of radio astronomy
Radio astronomy
Radio astronomy is a subfield of astronomy that studies celestial objects at radio frequencies. The initial detection of radio waves from an astronomical object was made in the 1930s, when Karl Jansky observed radiation coming from the Milky Way. Subsequent observations have identified a number of...
, infrared astronomy
Infrared astronomy
Infrared astronomy is the branch of astronomy and astrophysics that studies astronomical objects visible in infrared radiation. The wavelength of infrared light ranges from 0.75 to 300 micrometers...
and submillimeter astronomy in the 20th Century allowed the gas and dust of the Milky Way to be mapped for the first time.
Subcategories
A standard set of subcategories is used by astronomical journals to split up the subject of Galactic Astronomy:- abundances - the study of the location of elements heavier than helium
- bulge - the study of the bulge around the center of the Milky Way
- center - the study of the central region of the Milky Way
- disk - the study of the Milky Way disk (the plane upon which most galactic objects are aligned)
- evolution - the evolution of the Milky Way
- formation - the formation of the Milky Way
- fundamental parameters - the fundamental parameters of the Milky Way (mass, size etc.)
- globular clusters - globular clusters within the Milky Way
- halo - the large halo around the Milky Way
- kinematics and dynamics - the motions of stars and clusters
- nucleus - the region around the black holeBlack holeA black hole is a region of spacetime from which nothing, not even light, can escape. The theory of general relativity predicts that a sufficiently compact mass will deform spacetime to form a black hole. Around a black hole there is a mathematically defined surface called an event horizon that...
at the center of the Milky Way (Sagittarius A*) - open clusters and associations - open clusters and associations of stars
- solar neighbourhood - nearby stars
- stellar content - numbers and types of stars in the Milky Way
- structure - the structure (spiral arms etc.)
Interstellar medium
- Interplanetary space - Interplanetary mediumInterplanetary mediumThe interplanetary medium is the material which fills the solar system and through which all the larger solar system bodies such as planets, asteroids and comets move.-Composition and physical characteristics:...
- interplanetary dust - Interstellar spaceInterstellar SpaceInterstellar Space was one of the final studio albums recorded by the saxophonist John Coltrane before his death in 1967, originally-released posthumously by Impulse! Records on LP in 1974.-Composition:...
- Interstellar mediumInterstellar mediumIn astronomy, the interstellar medium is the matter that exists in the space between the star systems in a galaxy. This matter includes gas in ionic, atomic, and molecular form, dust, and cosmic rays. It fills interstellar space and blends smoothly into the surrounding intergalactic space...
- interstellar dust - Intergalactic space - Intergalactic medium - Intergalactic dustIntergalactic dustIntergalactic dust is cosmic dust in between galaxies in intergalactic space. Evidence for intergalactic dust has been suggested as early as 1949, and study of it grew throughout the late 20th century. There are large variations in the distribution of intergalactic dust...