A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

H I region
H II region
H and K lines
H series (Japanese rockets)
H-1 (rocket engine)
Haas, Conrad (c. 1509–1579)
HabCat (Catalog of Nearby Habitable Systems)
Haber process
habitable zone
Hadar (Beta Centauri)
Hadley, John H. (1682–1744)
Hadley circulation
hadron
Hadwiger problem
hafnium
Hagen, John P. (1908–1990)
Hagoromo
Hahn, Otto (1879–1968)
hahnium
hail
hailstone sequence
hair
hairy ball theorem
Haise, Fred Wallace, Jr. (1933–)
Hakucho
HALCA (Highly Advanced Laboratory for Communications and Astronomy)
Haldane, J. B. S. (1892–1964)
Hale, Edward Everett (1822–1909)
Hale, George Ellery (1868–1938)
Hale, William (1797–1870)
Hale Observatories
Hale Telescope
Hale-Bopp, Comet (C/1995 O1)
half-cell
half-life
halide
halite
Hall, Asaph (1829–1907)
Hall effect
Hall effect thruster
Hall process
Halley, Edmond (1656–1742)
Halley's Comet
Halley-type comet
hallucination
hallucinogenic drug
halo, atmospheric
halo, galactic
halo orbit
haloalkane
halogen
halogenation
halophiles
halophyte
H-alpha
halteres
halting problem
Ham
ham sandwich theorem
Hamal (Alpha Arietis)
Hamilton, William Rowan (1805–1865)
Hamiltonian
Hammaguira
hamstring muscles
hand
handedness
hand-working metals
hanging valley
haploid
happy number
haptotropism
hard landing
hard palate
hardness
Hardy, G(odfrey) H(arold) (1877–1947)
Hargreaves, James (c. 1720–1778)
harmonic analysis
harmonic sequence
harmonic points
harmonics
Harmony Node 2 (on ISS)
Haro, Guillermo (1913–1988)
Haro galaxy
HARP (High Altitude Research Project)
Harriot, Thomas (c. 1560–1621)
Harrison, John (1693–1776)
Harshad number
Hartmann test
Haruka
Harvard College Observatory
Harvard SETI Group
Harvard-Arecibo off-line SETI
Harvard-Smithsonian Center for Astrophysics
Harvard-Smithsonian radio telescope
harvestman
Harvey, William (1578–1657)
Hat Creek Observatory
Hat Problem
Hatry, Julius (1906–2000)
Hausdorff, Felix (1868–1942)
haustorium
Haute-Provence Observatory
Hawking, Stephen William (1942–2018)
Hawking radiation
Hawksbee, Francis (1660–1713)
Haworth, Walter Norman (1883–1950
hay fever
Hayabusa (MUSES-C)
Hayashi, Chushiro (1920–2010)
Hayashi track
Haynes, Elwood (1857–1925)
HCMM (Heat Capacity Mapping Mission)
HD 10697
HD 37124
HD 69830
HD 75289
HD 98618
HD 110067: a 'perfect planetary system'
HD 114762
HD 130322
HD 134987
HD 168443
HD 177830
HD 187123
HD 189773 A
HD 192263
HD 195019
HD 209458
HD 210277
HD 217107
HD 222582
HE0107-5240
HE1327-2326
head
headache
head-tail galaxy
HEALTH AND DISEASE
HEAO (High Energy Astrophysics Observatory)
hearing
hearing aid
heart
heart attack (myocardial infarction)
heart attack warning signs
heart block
heart disease in women
heart disease risk factors
heart electrical system
heart failure
heart murmur
Heart Nebula (IC 1805)
heart palpitations
heart rate
heart surgery
HEART TOPICS
heart transplant
heart valve disease
heart valves
heartburn
heat
HEAT AND THERMODYNAMICS
heat balance
heat capacity
heat death
heat engine
heat of vaporization
heat pump
heat shield
heat transfer
Heaviside, Oliver (1850–1925)
heavy element
heavy water
heavy-lift launch vehicle
HED group
hedgehog
heel
Heesch number
Hegel, Georg Wilhelm Friedrich (1770–1831)
Hein, Piet (1905–1996)
Heinkel He 178
Heinlein, Robert A. (1907–1988)
Heisenberg, Werner Karl (1901–1976)
Heisenberg uncertainty principle
Hektor
Helene
heliacal rising
helicity
helicoid
helicon thruster
helicopter
heliocentric
heliocentric coordinates
heliograph
heliographic coordinates
heliopause
Helios (French reconnaissance satellites)
Helios (German solar probes)
helioseismology
heliosphere
heliostat
helium
helium burning
helix
Helix Galaxy (NGC 2685)
Helix Nebula (NGC 7293)
Hellas
Hellas Planitia
helmet streamer
Helmholtz, Hermann von (1821–1894)
Helmholtz resonator
Helmont, Jan Baptista van (1580–1644)
hematite
hematocrit
hematoma
heme
hemichordata
hemimorphite
Hemiptera
hemochromatosis
hemocoel
hemocyanin
hemoglobin
hemoglobinuria
hemolysis
hemolytic anemia
hemophilia
hemorrhage
hemorrhoids
hemothorax
hemp
hen
henry (H)
Henry, James Paget (1914–1996)
Henry, Joseph (1797–1878)
Henry, William (1774–1836)
Henry's law
Henyey track
HEO (highly elliptical/high Earth orbit)
HEOS (Highly Eccentric Orbiting Satellite)
heparin
hepatic artery
hepatic vein
hepatitis
heptagon
heptane
Heraclides of Pontus (c. 388–c. 315 BC)
Heraclitus (c. 540–c. 480 BC)
herb
herbaceous
Herbig Ae/Be star
Herbig-Haro object
herbivore
Hercules (constellation)
Hercules Cluster (Abell 2151)
Hercules Globular Cluster (M13, NGC 6205)
Hercules X-1
14 Herculis
heredity
Hermann grid illusion
hermaphrodite
Hermes
Hermite, Charles (1822–1901)
hernia
Hero of Alexandria (1st century AD)
Hero's formula
Herring illusion
Herschback, Dudley Robert (1932–)
Herschel, Caroline Lucretia (1750–1848)
Herschel, John Frederick William (1792–1871)
Herschel, (Frederick) William (1738–1822)
Herschel Space Observatory
Herschelian telescope
Hershey, Alfred Day (1908–1997)
hertz (Hz)
Hertz, Gustav Ludwig (1887–1975)
Hertz, Heinrich (1857–1894)
Hertzsprung, Ejnar (1873–1967)
Hertzsprung-Russell diagram
Herzberg, Gerhard (1904–1999)
Hess, Victor Franz (1883–1964)
Hess, Walter Rudolf (1881–1973)
Hess's law
HETE (High Energy Transient Experiment)
heterocyclic compound
heterodyne
heterostyly
heterotrophs
heterozygous
Hevelius, Johannes (1611–1687)
Hevesey, George Charles de (1885–1966)
Hewish, Anthony (1924–2021)
Hex
hexa-
hexadecimal
hexagon
hexahedrite
hexahedron
hexose
Heyrovsky, Jaroslav (1890–1967)
hibernation
Hidalgo
hidden dimensions
hidden variables theory
Higgs boson
High Accuracy Radial velocity Planetary Search (HARPS)
high blood cholesterol
high blood pressure (hypertension)
High Resolution Microwave Survey (HRMS)
higher dimensions
highest common factor
high-gain antenna
highly conserved sequence
high-temperature physics
high-velocity cloud
high-velocity star
Highwater
Hilbert, David (1862–1943)
Hilbert space
Hilda group
Himalia
Himawari
Hind, John Russell (1823–1895)
hindbrain
Hind's Crimson Star
Hind's Variable Nebula
hinge joint
Hinotori
Hinshelwood, Cyril Norman (1897–1967)
Hinton, Charles Howard (1853–1907)
hip joint
Hipparchus of Nicaea (190–125 BC)
Hipparcos
Hippias of Elis (fl. 5th century BC)
hippocampus
Hippocrates (c. 460–c. 377 BC)
hippopede
hippopotamus
Hirayama family
histamine
histidine
histogram
histology
histones
histoplasmosis
HISTORY OF ASTRONOMY
history of electricity
HISTORY OF MATHEMATICS
HISTORY OF SCIENCE
history of technology
Hiten
hive intelligence
hives
Hoag's Object
Hoba meteorite
Hobbes, Thomas (1588–1679)
Hobby-Eberly Telescope
Hockey Stick Galaxy (NGC 4656)
Hodgkin, Dorothy Mary Crowfoot (1910–1994)
Hodgkin's disease
Hodgkin's disease treatment
Hodierna, Giovanni Battista (1597–1660)
Hoerner, Sebastien von (1919–2003)
Hofmann, Augustus Wilhelm von (1818–1892)
Hofstadter, Douglas R. (1945–)
Hofstadter, Robert (1915–1990)
Hogben, Lancelot Thomas (1895–1975)
Hohmann, Walter (1880–1945)
Hohmann orbit
hole
hole in the heart
hole-in-a-postcard problem
hole-through-a-sphere problem
hole-through-the-Earth problem
holistic
Holland, John Philip (1840–1914)
Hollerith, Herman (1860–1929)
Holley, Robert William (1922–1993)
Holmberg, Erik Bertil (1908–2000)
Holmberg II Dwarf Irregular Galaxy
Holmes, Arthur (1890–1965)
holmium
Holocene
holodeck
holographic hypothesis
Holter monitor
homeomorphic
homeostasis
homeotherm
hominid
Homo
Homo erectus
Homo habilis
homogenization
homologous recombination
homologous series
homologue
homology
homotopy
homozygous
honey
Hooke, Robert (1635–1703)
Hooke's law
hookworm
Hoover, George W. (1915–1998)
HOPE (H-2 Orbital Plane)
horizon
horizon problem
hormone
hormone replacement therapy (HRT)
horn
hornblende
hornfels
hornito
Horologium (constellation)
Horowitz, Norman H. (1915–2005)
Horrocks, Jeremiah (c. 1618–1641)
horse family
horse latitudes
Horsehead Nebula (Barnard 33)
horsepower
horseshoe crab
horsetail
horst
host
"hot Jupiter"
hot spot
hot spring
hot subdwarf
HOTOL (Horizontal Takeoff and Landing vehicle)
Hounsfield, Godfrey Newbold (1919–2004)
hour (hr)
hour angle
hourglass
Hourglass Nebula
Houssay, Bernado Alberto (1887–1971)
hovercraft
howardite
Hoyle, Fred (1915–2001)
HR 4796A
HR 810
HST
Huang, Su-Shu (1915–1977)
Hubble, Edwin Powell (1889–1953)
Hubble constant
Hubble law
Hubble radius
Hubble Space Telescope
Hubble tension
Hubble's Variable Nebula (NGC 2261)
Huggins, Margaret Lindsay (1848–1915)
Huggins, Charles Brenton (1901–1997)
Huggins, William (1824–1910)
Hulse-Taylor Pulsar
human evolution
Human Genome Project
Human Research Facility
Humason, Milton Lasell (1891–1972)
Humason, Comet (1961e)
Humboldt, Friedrich Heinrich Alexander, Baron von (1769–1859)
Humboldt current
Hume, David (1711–1776)
humerus
humidity
hummock
humors
humpback whales, songs
hundred
hundred fowls problem
Hund's rules
Hungaria group
Hunter, J(ames) A(lston) H(ope)
Hunter, John (1728–1793)
Huntington's disease
hurricane
Hutton, James (1726–1797)
Hutton, Richard Holt (1826–1897)
Huxley, Thomas Henry (1825–1895)
Huygens, Christiaan (1629–1695)
Huygens Probe
Hyades
Hyakutake, Comet (C/1996 B2)
hyaline cartilage
hybrid
hybrid-propellant rocket engine
hybridization
Hycean planet
Hydra (constellation)
Hydra (organism)
hydrate
hydration
hydraulic action
hydraulics
hydrazine
hydrazone
hydride
hydrobot
hydrocarbon
hydrocephalus
hydrochloric acid
hydrocyanic acid
hydrodynamics
hydrofluoric acid
hydrofoils and air-cushion vehicles
hydrogen
hydrogen bond
hydrogen burning
hydrogen chloride
hydrogen cyanide
hydrogen fluoride
hydrogen peroxide
hydrogen spectrum
hydrogen sulfide
hydrogenation
hydrology
hydrolysis
hydrometer
hydrophily
hydrophone
hydroponics
hydrostatic equilibrium
hydrostatics
hydrothermal vent
hydroxide
hydroxyl radical
Hydrus (constellation)
Hygiea (asteroid)
hygrometer
hygroscopic
hymen
Hymenoptera
Hynek, J. Allen (1910–1986)
hyoid
Hypatia of Alexandria (c. AD 370–417)
hyperbaric chamber
hyperbola
hyperbolic function
hyperbolic geometry
hyperbolic orbit
hyperboloid
hypercalcemia
hypercube
hyperfactorial
hyperfine structure
hypergeometric function
hypergiant
hyperglycemia
Hyperion
hypernova
hyperon
hyperopia (farsightedness)
hyperreal number
hypersonic
hyperspace
hypersphere
hypersthene
hyperthermia
hyperthermophiles
hypervelocity impact
hypervelocity star
hypha
hypnosis
hypochlorite
hypochondria
hypocycloid
hypodermic syringe
hypodermis
hypoglossal nerve
hypoglycemia
hypersensitivity
hyperthermia
hypotension (low blood pressure)
hypothalamus
hypothermia
hypothyroidism
hypotrochoid
hypoxia
Hyracoidea
hysterectomy
hysteresis loop
HZ
HZ Herculis star