A for Andromeda
"A" series of German rockets
A star
a'a
AAA
AAO
Aaronson, Marc (1950-1987)
AAT
abacus
abalone
Abbott, Edwin Abbott (1838–1926)
Abbott, Ira H. (1906-)
ABC conjecture
abdomen
abducens nerve
abduction
Abel, Niels Henrik (1802-1829)
Abelian group
Abell 39
Abell cluster
Aberdeen Proving Ground
aberration, optical
aberration of starlight
abiogenesis
abiotic
ablation
Able
ABMA (Army Ballistic Missile Agency)
abort
abracadabra
abscess
abscissa
abscission
absolute
Absolute Astronomical Accelerometry
absolute magnitude
absolute space and time
absolute value
absolute zero
absorbed dose
absorber
absorptance
absorption
absorption band
absorption line
absorption nebula
absorption spectrum
absorptive feeder
abstract algebra
Abu’l Wafa (AD 940-998)
abundance, of elements
abundant number
Abyss, The
abyssal zone
acapulcoite
Acasta Formation
acceleration
acceleration due to gravity (g)
acceleration stress
acceleration tolerance
accelerator
accelerometer
ACCESS (Advanced Cosmic-ray Composition Experiment on the Space Station)
accessory nerve
accessory organ
accessory pigment
accommodation
accretion
accretion disk
accretionary lapilli
accretionary wedge
ACE (Advanced Composition Explorer)
acellular
acephalous
acetabulum
acetic acid
acetogens
acetone
acetyl coenzyme A
acetylcholine
acetylene (C₂H₂)
achene
Achernar (Alpha Eridani)
Achilles (minor planet 588)
Achilles tendon
achlamydeous
achondrite
achromatic
achrondoplasia
acid
acidic
acidophiles
Ackermann function
A-class asteroid
acosmism
acquisition
ACRIMSAT (Active Cavity Radiometer Irradiance Monitor Satellite)
acre
Acrux (Alpha Crucis)
ACRV (Assured Crew Return Vehicle)
ACT Catalog
actin
actinide
actinium
action
action at a distance
action potential
activation cross section
activation energy
active beam
active fault
active galactic nucleus
active galaxy
active optics
active region
active satellite
active site
active sun
active transport
activity
ACTS (Advanced Communications Technology Satellite)
acute
acute respiratory distress syndrome
Ad Astra Rocket Company
Adams, John (1735-1826)
Adams, John Couch (1819-1892)
Adams, Walter Sidney (1876-1956)
Adam's apple
Adamski, George (1891-1965)
adaptation
adapter skirt
adaptive optics
adaptive radiation
Addison, John (1672-1719)
addition reaction
additive
adduction
ADE (Air Density Explorer)
adenine
adenoids
adenosine diphosphate (ADP)
adenosine triphosphate (ATP)
adenovirus
ADEOS (Advanced Earth Observing Satellite)
Adhara (Epsilon Canis Majoris)
ADHD (Attention Deficit–Hyperactive Disorder)
adhesion
adiabatic process
adipose tissue
adjacent
admittance
Adrastea
adrenal gland
adrenaline
adrenocorticotropic hormone (ACTH)
adsorption
advance of perihelion
Advanced Composition Explorer (ACE)
Advanced Fiber-Optic Echelle spectrometer (AFOE)
ADVANCED PROPULSION CONCEPTS
Advanced Quantum/Relativity Theory Propulsion Workshop (1994)
advanced wave
adventitious
AE Aurigae
Ae star
AEM (Applications Explorer Mission)
aeolipile
aerenchyma
aerial
Aerial Phenomena Research Organization (APRO)
Aerial Target (A.T.)
aeroballistics
aerobe
Aerobee
aerobic
aerobraking
aerocapture
aerodynamics
AERODYNAMICS AND AERONAUTICS
aeroembolism
aerogel
Aerojet Corporation
aerolite
aeronautics
aeronomy
aeropause
Aeros
aerosol
aerospace
AEROSPACE ADMINISTRATORS
AEROSPACE AND RELATED COMPANIES
aerospace medicine
aerothermodynamic border
affine geometry
AFOE
AFSATCOM (Air Force Satellite Communications System)
afterburner
afterburning
afterglow
aftershock
aft-firing thrusters
agate
Agena
agglutinates
aging
AGN
Agnesi, Maria Gaetana (1718-1799)
agravic
Agrest, Matest M. (1915-)
Agrest, Mikhail
Ahnighito meteorite
Ahrens, Wilhelm Ernst Martin Georg (1872-1927)
AI Velorum star
aileron
AIM (Aeronomy of Ice in the Mesophere)
air breakup
Air Force Flight Test Center
Air Force Space Command
Air Materiel Command (AMC)
air start
Air Technical Intelligence Center (ATIC)
air-breathing engine
airfoil
airframe
airglow
airlock
airmass
airplane
airship
airspace
airways
Airy, George Biddell (1801-1892)
Airy disk
Aitken, Robert Grant (1864-1951)
Aitken Double Star Catalogue (ADS)
Akebono
Akiyama, Tokohiro (1944-)
Al Niyat (Sigma and Tau Scorpii)
Alais meteorite
alanine
Albategnius (al-Battani, Muhammad ibn Jabir) (c. 850-929)
albedo
albedo feature
Albertus Magnus (1193-1280)
Albireo (Beta Cygni)
Alcantara Launch Center
alchemy
alcohols
Alcubierre, Miguel
Alcubierre warp drive
Alcuin (735-804)
Alcyone (Eta Tauri)
Aldebaran (Alpha Tauri)
aldehyde
Alderamin (Alpha Cephei)
aldosterone
Aldrin, Edwin Eugene (“Buzz”), Jr. (1930-)
Alembert, Jean le Rond d' (1717-1783)
Alencon Spaceman
aleph
Alexander's Horned Sphere
Alexandra family (of asteroids)
ALEXIS (Array of Low Energy X-ray Imaging Sensors)
Alfirk (Beta Cephei)
Alfvén, Hannes Olof Gösta (1908-1995)
algae
ALGEBRA
algebra
algebraic curve
algebraic function
algebraic geometry
algebraic number
algebraic number theory
algebraic topology
Algieba (Gamma Leonis)
Algol (Beta Persei)
Algol star
Algonquin Radio Observatory
algorithm
algorithmic complexity
ALH 84001
Alhambra
Alhazen (Abu Ali al Hassan ibn al Haitham) (c. 965-c. 1040)
Alhena (Gamma Geminorum)
alien
Alien
alien abduction
alimentary canal
Alinda group (of asteroids)
Alioth (Epsilon Ursae Majoris)
aliphatic compound
aliquot part
Alkaid (Eta Ursae Majoris)
alkali
alkali metal
alkaline
alkaline earth metal
alkaliphile
alkaloid
alkanes
alkenes
Al-Khowarizmi (c. 780-850)
alkynes
Allais paradox
Allan Hills
Allegheny Observatory
allele
Allen, Irwin (1916-1991)
Allen Telescope Array (ATA)
Allende meteorite
allergy
allotropy
alloy
all-sky camera
all-sky survey
alluvium
ALMA
Almaak (Gamma Andromedae)
Almagest
almanac
Almaz
almost perfect number
Alnair (Alpha Gruis)
Alnath (Beta Tauri)
Alnilam (Epsilon Orionis)
Alnitak (Zeta Orionis)
ALOS (Advanced Land Observing Satellite)
Alouette
Alpha Centauri
Alpha Cygni star
alpha particle
Alpha² Canum Venaticorum star
alphamagic square
alphametic
Alphard (Alpha Hydrae)
Alphekka (Alpha Coronae Borealis)
Alpher, Ralph Asher (1921-2007)
Alpheratz (Alpha Andromedae)
Alphonsine Tables
Alphonsus
Al-Sufi, Abd al-Rahman (AD 903-986)
Altair (Alpha Aquilae)
altazimuth mounting
Altekruse puzzle
alternate
alternate mission
alternating current
ALTERNATIVE FORMS OF LIFE
altimeter
altitude
Aludra (Eta Canis Majoris)
aluminum
aluminum, powdered
aluminizing
Alvarez, Luis Walter (1911-1988)
alveolus
AM Canum Venaticorum star
AM Herculis star
Am star
Amalthea
Amazonian epoch
Ambartsumian, Viktor Amazaspovich (1908-1996)
Ambartsumian’s Knot
ambient condition
ambiguous figure
ambipolar diffusion
AMC
American Astronautical Society (AAS)
American Astronomical Society (AAS)
American Institute of Aeronautics and Astronautics (AIAA)
American Rocket Society
americium
Ames, Milton B. (1913-)
Ames Research Center
Ames room
amethyst
amicable numbers
amide
amine
amino acids
amino acids, in space
amino group
ammeter
ammonia
ammonia-based life
ammonite
ammonium perchlorate (NH₄ClO₄)
amnion
amniotic fluid
amniotic sac
amoeba
amoeboid
Amor group
amorphous
amount of substance
Ampère, André Marie (1775-1836)
ampere
amphibian
amphibole
amphoteric
amplitude
AMPTE (Active Magnetosphere Particle Tracer Explorer)
AMS (Alpha Magnetic Spectrometer)
amygdala
amylase
amyotrophic lateral sclerosis
anabiosis
anabolism
anacoustic zone
anaerobe
anaerobic
anagram
analemma
anallagmatic curve
analogous
analogy, argument from
analysis
ANALYTICAL CHEMISTRY
analytical geometry
analytical number theory
anamorphosis
Ananke
anaphase
anastigmat(ic)
ANATOMY AND PHYSIOLOGY
Anaxagoras of Clazomenae (c.500-c.428 BC)
Anaximander of Miletus (c.610-c.540 BC)
Anaximenes of Lampsacus (c.585-525 BC)
ancient astronaut hypothesis
ancient philosophy, related to the possibility of extraterrestrial life
Anders, William Alison (1933-)
andesite
Andřya Rocket Range
Andrews Air Force Base
androecium
androgen
android
Andromeda (constellation)
Andromeda Galaxy (M31, NGC 224)
andromonoecious
anemia
anemic spiral galaxy
anencephaly
anergolic propellant
aneurysm
Angara
Angelina (minor planet 64)
angina
angioplasty
angiosperm
angle
angle of attack
angle of incidence
Anglo-Australian Observatory
Anglo-Australian Planet Search
Anglo-Australian Telescope
angrite
Ĺngström, Anders Jonas (1814-1874)
angular diameter
angular momentum
angular momentum quantum number
angular separation
angular velocity
anhydrobiosis
anhydrous
ANI
Anik
aniline (C₆H₅NH₂)
animal
animal cell
animal model
animals in space
animals' mathematical ability
anion
anisotropy
ankle
annihilation
annual (plant)
annual ring
annual variation
annulus
anode
anomalous X-ray pulsar (AXP)
anomaly
anorthosite
anoxia
ANRO
ANS (Astronomische Nederlandse Satelliet)
ansa
Ansari X-prize
Ansbro, Eamonn
Ant Nebula (Menzel 3)
Antarctic Dry Valleys
Antarctic Search for Meteorites (ANSMET)
Antares (Alpha Scorpii)
antenna
antenna array
antenna directivity
antenna temperature
Antennae (NGC 4038 and NGC 4039)
anterior
anther
anthocyanin
Anthony, Piers (1934-)
anthro-, anthropo-
anthropic principle
anthropogenic
anthropoid
ANTHROPOLOGY
anthropomorphic
anthropomorphism
antibiotic
antibody
anticodon
antidiuretic hormone (ADH)
anti-g suit
antigen
antigravity
antigravity houses and hills
antihistamine
Antikythera Mechanism
antimagic square
antimatter
antimatter propulsion
antimatter-driven sail
antimony
antinode
Antiope (minor planet 90)
antiparticles
antiprism
antisense
antiseptic
antisolar point
antitail
Antlia (constellation)
Antlia Dwarf Galaxy
Antoniadi, Eugene Michael (1870-1944)
Antoniadi scale
anus
AO Cassiopeiae
aorta
Ap star
Apache Point Observatory (APO)
apastron
ape
apergy
aperiodic tiling
aperture
aperture synthesis
Apéry's constant
apex
APEX
aphelion
apical meristem
aplastic anemia
apoapsis
apochromatic
apocrine gland
apogee
apogee kick motor
apohele
Apollo (minor planet 1862)
Apollo 7
Apollo 8
Apollo 9
Apollo 10
Apollo 11
Apollo 12
Apollo 13
Apollo 14
Apollo 15
Apollo 16
Apollo 17
Apollo group
Apollo Project
Apollonius of Perga (c. 262-c. 190 BC)
Apollonius problem
Apollo-Soyuz Test Project
apolune
Apophis (minor planet 99942)
apoptosis
apothem
apotome
apparent horizon
apparent magnitude
apparition
appendicitis
appendix
applied mathematics
APRO
apsis
Apus (constellation)
Aqua
Aquarius (constellation)
Aquarius (spacecraft)
Aquarius Dwarf
aqueous humor
Aquila (constellation)
aquifer
Aquinas, Thomas (1225-1274)
Ara (constellation)
Arabian astronomy
Arabic numerals
arachnid
arachnoid membrane
Arago, Dominique Francois Jean (1786-1853)
Arago point
arbelos
arboreal
arc
arch
archaea
archaeobacteria
archeoastronomy
Arches Cluster
Archimedean solid
Archimedean spiral
Archimedean tessellation
Archimedes (c.287-212 BC)
Archimedes and the burning mirrors
Archimedes' cattle problem
Archimedes' principle
Archytas (c.428-c.350 BC)
arcjet
arc-second
Arcturus (Alpha Bootis)
area
area codes
Area 51
area rule
Arecibo message
Arecibo Observatory
Arecibo radio telescope
Arend-Roland, Comet (C/1956 R1)
areobiology
areography
Ares (launch vehicles)
Ares Vallis
Argand diagram
Argelander, Friedrich Wilhelm August (1799-1875)
Argo Navis
argon
ARGOS (Advanced Research and Global Observation Satellite)
argument
Argument from Design
argument of perihelion
Argus, Project
Argus radio telescope
Ariane
Arianespace
Ariel (moon of Saturn)
Ariel (UK satellites)
Aries (constellation)
Aries sounding rocket
Ariosto, Ludovico (1474-1533)
Aristarchus (crater)
Aristarchus of Samos (c.320-c.250 BC)
Aristotle of Stagira (384-322 BC)
Arisitotle's wheel
arithmetic
arithmetic mean
arithmetic sequence
Arizona Search for Planets
ark, interstellar
Arkhipov, Alexey V. (1959-)
armillary sphere
Armstrong, Neil Alden (1930-)
Army Ballistic Missile Agency (ABMA)
Arnold, Henry H. (Hap) (1886-1950)
Arnold, Kenneth (1915-1984)
aromatic compound
Arouet, Francois-Marie (1694-1778)
Around the Moon
Arp, Halton Christian (1927-)
array
Arrest, Heinrich Ludwig d’ (1822-1875)
Arrhenius, Gustaf (1859-1927)
Arrhenius, Svante August
arrow of time
Arrow paradox
arrhythmias
ARTEMIS (Advanced Relay Technology Mission)
Artemis Project, The
arteriography
arteriole
artery
arthritis
arthropod
articular capsule
artifacts, alien
artificial gravity
artificial intelligence
artificial life
ARTV (Advanced Reentry Test Vehicle)
Aryabhata the Elder (AD 476-c. 550)
Aryabhata (satellite)
Arzachel (Al-Zarqali, Abu Ishaq Ibrahim ibn Yahya) (1028-1087)
ASAT (antisatellite)
Asperger syndrome
Asbolus (minor planet 8405)
ASCA
ascending node
Asclepius (minor planet 4581)
aseptic
asexual reproduction
ash
ashen light
ASI (Agenzia Spaziale Italiano)
Asimov, Isaac (1920-1992)
ASLV (Advanced Satellite Launch Vehicle)
aspect
aspect ratio
assay
ASSET (Aerothermodynamic Elastic Structural Systems Environmental Tests)
associations, stellar
associative
astatine
asterism
Asterix
asteroid
asteroid belt
ASTEROIDS, CENTAURS, AND KUIPER BELT OBJECTS: INDIVIDUAL
ASTEROIDS AND OTHER MINOR PLANETS: TYPES AND GROUPS
asthenosphere
asthma
astigmatism
Astraglossa
Astro (shuttle science payload)
astro- (prefix)
Astro- (Japanese satellites)
Astro-E
Astro-F
ASTROBIOLOGY
astrobiology
Astrobiology Institute
astrobleme
astrochemistry
astrocyte
astrodynamics
astroengineering
Astrographic Catalogue
astroid
astrolabe
astrometric binary
astrometry
Astron
astronaut
astronautics
ASTRONAUTS AND COSMONAUTS
Astronomer Royal
ASTRONOMERS AND ASTROPHYSICISTS
Astronomical Almanac
ASTRONOMICAL CATALOGUES
astronomical clock
astronomical constants
astronomical extinction
Astronomical Nulling Interferometer (ANI)
ASTRONOMICAL QUANTITIES
Astronomical Society of the Pacific (ASP)
astronomical unit
Astronomische Gesellschaft Katalog (AGK)
astronomy
ASTRONOMY AND ASTROPHYSICS
astrophotography
astrophysics
astroseismology
astrosociology
Asuka
asymmetric carbon atom
asymmetric drift
asymptote
asymptotic freedom
asymptotic giant branch
A.T. (Aerial Target)
ATA
Atacama Large Millimeter Array
ataxite
Atchley, Jr., Dana W.
Aten group
Athena
Athena (launch vehicle)
Athena Precursor Experiment (APEX)
atherosclerosis
ATIC
Atiyah, Michael Francis (1929-)
Atlantic Missile Range
Atlantis (Shuttle orbiter)
Atlantis, legend of
Atlas (launch vehicle)
Atlas (moon)
ATLAS particle detetector
atmosphere
atmosphere (unit)
atmospheric braking
atmospheric extinction
atmospheric halo
ATMOSPHERIC PHENOMENA AND STRUCTURES
atmospheric pressure
atmospheric refraction
atmospheric trajectory
atmospheric window
ATNF
atom
ATOMIC AND NUCLEAR PHYSICS
atomic clock
atomic mass
atomic mass unit
atomic number
atomic orbital
atomism
Atoms For Peace Galaxy (NGC 7252)
Atomium, The
ATP
Atria (Alpha Trianguli Australis)
atrial natriuretic peptide (ANP)
atrial fibrillation
atrial septal defect (hole-in-the-heart)
atrium
atropine
ATS (Applications Technology Satellite)
attitude
attitude control
attitude jets
attractor
AU
Aubel's theorem
aubrite
auditory nerve
Auger effect
augite
augmentor
Augustine, Norman R. (1935-)
Aura
auricle
Auriga (constellation)
aurora
Australian National Radio Observatory
Australian Space Research Institute
Australia Telescope National Facility (ATNF)
australopithecine
autism
autocatalysis
autocatalytic
autogyro
auto-igniting propellant
auto-ignition temperature
autoimmune disease
Automated Transfer Vehicle
automorphic number
automorphism
autonomic nervous system
autopoeisis
autosomal dominant
autosome
autotrophs
auxin
Avdeyev, Sergei (1956-)
average
average thrust
averted vision
AVIATION PIONEERS
avionics
Avior (Epsilon Carinae)
Avogadro constant
Avrocar
axial period
axial rotation
axil
axis
axiom
axiom of choice
axion
axon
azimuth
azo compound
azathioprine
Azur