An astronomer is a
scientist
A scientist is a person who Scientific method, researches to advance knowledge in an Branches of science, area of the natural sciences.
In classical antiquity, there was no real ancient analog of a modern scientist. Instead, philosophers engag ...
in the field of
astronomy
Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...
who focuses on a specific question or field outside the scope of
Earth
Earth is the third planet from the Sun and the only astronomical object known to Planetary habitability, harbor life. This is enabled by Earth being an ocean world, the only one in the Solar System sustaining liquid surface water. Almost all ...
. Astronomers observe
astronomical object
An astronomical object, celestial object, stellar object or heavenly body is a naturally occurring physical entity, association, or structure that exists within the observable universe. In astronomy, the terms ''object'' and ''body'' are of ...
s, such as
star
A star is a luminous spheroid of plasma (physics), plasma held together by Self-gravitation, self-gravity. The List of nearest stars and brown dwarfs, nearest star to Earth is the Sun. Many other stars are visible to the naked eye at night sk ...
s,
planet
A planet is a large, Hydrostatic equilibrium, rounded Astronomical object, astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. The Solar System has eight planets b ...
s,
moons,
comet
A comet is an icy, small Solar System body that warms and begins to release gases when passing close to the Sun, a process called outgassing. This produces an extended, gravitationally unbound atmosphere or Coma (cometary), coma surrounding ...
s and
galaxies
A galaxy is a system of stars, stellar remnants, interstellar gas, dust, and dark matter bound together by gravity. The word is derived from the Greek ' (), literally 'milky', a reference to the Milky Way galaxy that contains the Solar Sys ...
β in either
observational (by analyzing the data) or
theoretical astronomy. Examples of topics or fields astronomers study include
planetary science
Planetary science (or more rarely, planetology) is the scientific study of planets (including Earth), celestial bodies (such as moons, asteroids, comets) and planetary systems (in particular those of the Solar System) and the processes of ...
,
solar astronomy, the
origin or
evolution of stars, or the
formation of galaxies. A related but distinct subject is
physical cosmology
Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of fu ...
, which studies the
Universe
The universe is all of space and time and their contents. It comprises all of existence, any fundamental interaction, physical process and physical constant, and therefore all forms of matter and energy, and the structures they form, from s ...
as a whole.
Types
Astronomers typically fall under either of two main types:
observational and
theoretical. Observational astronomers make direct
observation
Observation in the natural sciences is an act or instance of noticing or perceiving and the acquisition of information from a primary source. In living beings, observation employs the senses. In science, observation can also involve the percep ...
s of
celestial objects and analyze the data. In contrast, theoretical astronomers create and investigate
model
A model is an informative representation of an object, person, or system. The term originally denoted the plans of a building in late 16th-century English, and derived via French and Italian ultimately from Latin , .
Models can be divided in ...
s of things that cannot be observed. Because it takes millions to billions of years for a system of stars or a galaxy to complete a life cycle, astronomers must observe snapshots of different systems at unique points in their evolution to determine how they form, evolve, and die. They use this data to create models or
simulation
A simulation is an imitative representation of a process or system that could exist in the real world. In this broad sense, simulation can often be used interchangeably with model. Sometimes a clear distinction between the two terms is made, in ...
s to theorize how different celestial objects work.
Further subcategories under these two main
branches of astronomy include
planetary astronomy,
astrobiology
Astrobiology (also xenology or exobiology) is a scientific field within the List of life sciences, life and environmental sciences that studies the abiogenesis, origins, Protocell, early evolution, distribution, and future of life in the univ ...
,
stellar astronomy
Astronomy is a natural science that studies astronomical object, celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall chronology of the U ...
,
astrometry
Astrometry is a branch of astronomy that involves precise measurements of the positions and movements of stars and other Astronomical object, celestial bodies. It provides the kinematics and physical origin of the Solar System and this galaxy, th ...
,
galactic astronomy
Galactic astronomy is the study of the 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 con ...
,
extragalactic astronomy
Extragalactic astronomy is the branch of astronomy concerned with objects outside the Milky Way galaxy. In other words, it is the study of all astronomical objects which are not covered by galactic astronomy.
The closest objects in extragalactic ...
, or
physical cosmology
Physical cosmology is a branch of cosmology concerned with the study of cosmological models. A cosmological model, or simply cosmology, provides a description of the largest-scale structures and dynamics of the universe and allows study of fu ...
. Astronomers can also specialize in certain specialties of observational astronomy, such as
infrared astronomy
Infrared astronomy is a sub-discipline of astronomy which specializes in the astronomical observation, observation and analysis of astronomical objects using infrared (IR) radiation. The wavelength of infrared light ranges from 0.75 to 300 microm ...
,
neutrino astronomy
Neutrino astronomy is a branch of astronomy that gathers information about astronomical objects by observing and studying neutrinos emitted by them with the help of neutrino detectors in special Earth observatories. It is an emerging field in as ...
,
x-ray astronomy
X-ray astronomy is an observational branch of astronomy which deals with the study of X-ray observation and detection from astronomical objects. X-radiation is absorbed by the Earth's atmosphere, so instruments to detect X-rays must be taken to ...
, and
gravitational-wave astronomy
Gravitational-wave astronomy is a subfield of astronomy concerned with the detection and study of gravitational waves emitted by astrophysical sources.
Gravitational waves are minute distortions or ripples in spacetime caused by the acceleration ...
.
Academic
History
Historically, astronomy was more concerned with the
classification
Classification is the activity of assigning objects to some pre-existing classes or categories. This is distinct from the task of establishing the classes themselves (for example through cluster analysis). Examples include diagnostic tests, identif ...
and description of
phenomena
A phenomenon ( phenomena), sometimes spelled phaenomenon, is an observable Event (philosophy), event. The term came into its modern Philosophy, philosophical usage through Immanuel Kant, who contrasted it with the noumenon, which ''cannot'' be ...
in the sky, while
astrophysics
Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. As one of the founders of the discipline, James Keeler, said, astrophysics "seeks to ascertain the ...
attempted to explain these phenomena and the differences between them using
physical laws
Scientific laws or laws of science are statements, based on reproducibility, repeated experiments or observations, that describe or prediction, predict a range of natural phenomena. The term ''law'' has diverse usage in many cases (approximate, a ...
. Today, that distinction has mostly disappeared and the terms "astronomer" and "astrophysicist" are interchangeable. Professional astronomers are highly educated individuals who typically have a
PhD
A Doctor of Philosophy (PhD, DPhil; or ) is a terminal degree that usually denotes the highest level of academic achievement in a given discipline and is awarded following a course of graduate study and original research. The name of the deg ...
in
physics
Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...
or astronomy and are employed by research institutions or universities. They spend the majority of their time working on research, although they quite often have other duties such as teaching, building instruments, or aiding in the operation of an observatory.
The
American Astronomical Society
The American Astronomical Society (AAS, sometimes spoken as "double-A-S") is an American society of professional astronomers and other interested individuals, headquartered in Washington, DC. The primary objective of the AAS is to promote the adv ...
, which is the major organization of professional astronomers in
North America
North America is a continent in the Northern Hemisphere, Northern and Western Hemisphere, Western hemispheres. North America is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South Ameri ...
, has approximately 8,200 members (as of 2024). This number includes scientists from other fields such as physics,
geology
Geology (). is a branch of natural science concerned with the Earth and other astronomical objects, the rocks of which they are composed, and the processes by which they change over time. Modern geology significantly overlaps all other Earth ...
, and
engineering
Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...
, whose research interests are closely related to astronomy. The
International Astronomical Union
The International Astronomical Union (IAU; , UAI) is an international non-governmental organization (INGO) with the objective of advancing astronomy in all aspects, including promoting astronomical research, outreach, education, and developmen ...
comprises about 12,700 members from 92 countries who are involved in astronomical research at the PhD level and beyond (as of 2024).
Contrary to the classical image of an old astronomer peering through a
telescope
A telescope is a device used to observe distant objects by their emission, Absorption (electromagnetic radiation), absorption, or Reflection (physics), reflection of electromagnetic radiation. Originally, it was an optical instrument using len ...
through the dark hours of the night, it is far more common to use a
charge-coupled device
A charge-coupled device (CCD) is an integrated circuit containing an array of linked, or coupled, capacitors. Under the control of an external circuit, each capacitor can transfer its electric charge to a neighboring capacitor. CCD sensors are a ...
(CCD) camera to record a long, deep exposure, allowing a more sensitive image to be created because the
light
Light, visible light, or visible radiation is electromagnetic radiation that can be visual perception, perceived by the human eye. Visible light spans the visible spectrum and is usually defined as having wavelengths in the range of 400β ...
is added over time. Before CCDs,
photographic plates
Photographic plates preceded photographic film, film as the primary medium for capturing images in photography. These plates, made of metal or Glass, glass and coated with a light-sensitive Photographic emulsion, emulsion, were integral to early ...
were a common method of observation. Modern astronomers spend relatively little time at telescopes, usually just a few weeks per year. Analysis of observed phenomena, along with making predictions as to the causes of what they observe, takes the majority of observational astronomers' time.
Activities and graduate degree training
Astronomers who serve as faculty spend much of their time teaching undergraduate and graduate classes. Most universities also have
outreach
Outreach is the activity of providing services to any population that might not otherwise have access to those services. A key component of outreach is that the group providing it is not stationary, but mobile; in other words, it involves meetin ...
programs, including public telescope time and sometimes
planetariums, as a public service to encourage interest in the field.
Those who become astronomers usually have a broad background in physics,
mathematics
Mathematics is a field of study that discovers and organizes methods, Mathematical theory, theories and theorems that are developed and Mathematical proof, proved for the needs of empirical sciences and mathematics itself. There are many ar ...
, sciences, and
computing
Computing is any goal-oriented activity requiring, benefiting from, or creating computer, computing machinery. It includes the study and experimentation of algorithmic processes, and the development of both computer hardware, hardware and softw ...
in high school. Taking courses that teach how to research, write, and present papers are part of the higher education of an astronomer, while most astronomers attain both a
Master's degree
A master's degree (from Latin ) is a postgraduate academic degree awarded by universities or colleges upon completion of a course of study demonstrating mastery or a high-order overview of a specific field of study or area of professional prac ...
and eventually a PhD degree in astronomy, physics or
astrophysics
Astrophysics is a science that employs the methods and principles of physics and chemistry in the study of astronomical objects and phenomena. As one of the founders of the discipline, James Keeler, said, astrophysics "seeks to ascertain the ...
.
[
PhD training typically involves 5-6 years of study, including completion of upper-level courses in the core sciences, a competency examination, experience with teaching undergraduates and participating in outreach programs, work on research projects under the student's supervising professor, completion of a PhD thesis, and passing a final ]oral exam
The oral exam (also oral test or '; ' in German-speaking nations) is a practice in many schools and disciplines in which an examiner poses questions to the student in spoken form. The student has to answer the question in such a way as to demons ...
. Throughout the PhD training, a successful student is financially supported with a stipend
A stipend is a regular fixed sum of money paid for services or to defray expenses, such as for scholarship, internship, or apprenticeship. It is often distinct from an income or a salary because it does not necessarily represent payment for work pe ...
.[
]
Amateur astronomers
While there is a relatively low number of professional astronomers, the field is popular among amateurs
An amateur () is generally considered a person who pursues an avocation independent from their source of income. Amateurs and their pursuits are also described as popular, informal, self-taught, user-generated, DIY, and hobbyist.
History
H ...
. Most cities have amateur astronomy clubs that meet on a regular basis and often host star parties. The Astronomical Society of the Pacific is the largest general astronomical society in the world, comprising both professional and amateur astronomers as well as educators from 70 different nations.
As with any hobby
A hobby is considered to be a regular activity that is done for enjoyment, typically during one's leisure time. Hobbies include collecting themed items and objects, engaging in creative and artistic pursuits, playing sports, or pursuing other ...
, most people who practice amateur astronomy may devote a few hours a month to stargazing and reading the latest developments in research. However, amateurs span the range from so-called "armchair astronomers" to people who own science-grade telescopes and instruments with which they are able to make their own discoveries, create astrophotographs, and assist professional astronomers in research.
See also
* List of astronomers
* List of women astronomers
* List of Muslim astronomers
Medieval Islamic astronomy comprises the Astronomy, astronomical developments made in the Islamic world, particularly during the Islamic Golden Age (9thβ13th centuries), and mostly written in the Arabic language. These developments mostly took ...
* List of French astronomers
The following are list of French astronomers, astrophysicists and other notable French people who have made contributions to the field of astronomy. They may have won major prizes or awards, developed or invented widely used techniques or technolog ...
* List of Hungarian astronomers
* List of Russian astronomers and astrophysicists
* List of Slovenian astronomers
References
Sources
*
*
*
External links
American Astronomical Society
European Astronomical Society
International Astronomical Union
Astronomical Society of the Pacific
Space's astronomy news
{{Authority control
Astronomy
Science occupations