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
Haberdasher's Puzzle
habitable zone (HZ)
Hadar (Beta Centauri)
Hadley, John H. (1682-1744)
Hadley circulation
hadron
hadrosaur
Hadwiger problem
Hagen, John P. (1908-1990)
Hagoromo
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 cycle
Hale Observatories
Hale Telescope
Hale-Bopp, Comet (C/1995 O1)
Hale's polarity law
half-life
half-line
half-plane
halite
Hall, Asaph (1829-1907)
Hall effect
Hall effect thruster
Hall process
Halley, Edmond (1656-1742)
Halley's Comet
Halley-type comet
halo, atmospheric
halo, galactic
halo orbit
halo population
haloalkane
halogen
halophiles
H-alpha
halting problem
Ham
ham sandwich theorem
Hamal (Alpha Arietis)
Hamilton, William Rowan (1805-1865)
Hamilton circuit
Hamilton path
Hamiltonian
Hammaguira
hamstring muscles
HAN (hydroxyl ammonium nitrate)
hand
handedness
hand-held maneuvering unit
Hankel matrix
haploid
haploinsufficiency
happy number
hard landing
hard mockup
hard vacuum
Hardy, G(odfrey) H(arold) (1877-1947)
harmonic analysis
harmonic division
harmonic function
harmonic mean
harmonic sequence
Haro, Guillermo (1913-1988)
Haro galaxy
HARP (High Altitude Research Project)
HARPS (High Accuracy Radial Velocity Planetary Search)
Harriot, Thomas (ca. 1560-1621)
Harshad number
Hartmann test
Haruka
Harvard College Observatory
Harvard Revised Photometry (HR Photometry) Catalogue
Harvard SETI Group
Harvard-Arecibo off-line SETI
Harvard-Smithsonian Center for Astrophysics (CfA)
Harvard-Smithsonian radio telescope
harvest moon
Harvey, William (1578-1657)
Hat Creek Observatory
Hat Problem
Hatry, Julius (1906-2000)
Haughton-Mars Project
Hausdorff, Felix (1868-1942)
Hausdorff dimension
Haute-Provence Observatory (Observatoire de Haut-Provence)
Hawking, Stephen William (1942-)
Hawking radiation
Hayabusa (MUSES-C)
Hayashi, Chushiro (1920-)
Hayashi track
Hayes, John M.
HCMM (Heat Capacity Mapping Mission)
HD
HD 10697
HD 37124
HD 69830
HD 75289
HD 98618
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
head-tail galaxy
HEALTH AND DISEASE
HEAO (High Energy Astrophysics Observatory)
hearing aid
heart
heart attack (myocardial infarction)
heart attack warning signs
heart failure
heart murmur
heart rate
heart surgery
heart transplant
heart valve disease
heat
HEAT AND THERMODYNAMICS
heat barrier
heat capacity
heat engine
heat of vaporization
heat shield
heavy element concentration, related to occurrence of planets
heavy elements
heavy water
heavy-lift launch vehicle
HED group
heel
Heesch number
Hegel, Georg Wilhelm Friedrich (1770-1831)
Hein, Piet (1905-1996)
Heinkel He 178
Heinlein, Robert A. (1907-1988)
Heinsenberg uncertainty principle
Hektor (minor planet 624)
Helene
helical 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
helium star
Helix Galaxy (NGC 2685)
Helix Nebula (NGC 7293)
Hellas
Hellas Planitia
helmet streamer
Helmholtz, Hermann von (1821-1894)
hematite
hematocrit
hematopoietic stem cell
heme
hemochromatosis
hemocoel
hemocyanin
hemoglobin
hemoglobinuria
hemolysis
hemolytic anemia
hemophilia
henry (H)
Henry, James Paget (1914-1996)
Henry Draper Catalogue
Henyey track
HEO (highly elliptical/high Earth orbit)
HEOS (Highly Eccentric Orbiting Satellite)
hepatic
hepatitis
Heraclides of Pontus (c. 388-c. 315 BC)
Herbig Ae/Be star
Herbig-Haro object
Hercules (constellation)
Hercules Cluster (Abell 2151)
Hercules Globular Cluster (M13, NGC 6205)
Hercules X-1
14 Herculis
Hermann grid illusion
hermaphrodite
Hermes
Hermite, Charles (1822-1901)
hernia
Hero of Alexandria (1st century AD)
Hero's formula
Herring illusion
Herschel, Caroline Lucretia (1750-1848)
Herschel, John Frederick William (1792-1871)
Herschel, (Frederick) William (1738-1822)
Herschel Space Observatory
Herschelian telescope
Hertz, Heinrich (1857-1894)
hertz (Hz)
Hertzsprung, Ejnar (1873-1967)
Hertzsprung Gap
Hertzsprung-Russell diagram
Hesperian epoch
Hess, Victor Franz (1883-1964)
HET
HETE (High Energy Transient Experiment)
heterokaryotic
heterotrophs
heterozygous
heuristic argument
Hevelius, Johannes (1611-1687)
Hewish, Anthony (1924-)
Hex
hexa-
hexadecimal
hexagon
hexahedrite
hexahedron
hexose
hibernation
Hidalgo (minor planet 944)
hidden dimensions
hidden variables theory
Higgs boson
High Accuracy Radial velocity Planetary Search (HARPS)
high blood cholesterol
high blood pressure (hypertension)
high mass fraction
High Resolution Échelle Spectrometer (HIRES)
High Resolution Microwave Survey (HRMS)
high-energy radiation
higher dimensions
high-gain antenna (HGA)
highly conserved sequence
high-velocity cloud (HVC)
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
Hinotori
Hinton, Charles Howard (1853-1907)
hip joint
Hipparchus of Nicaea (190-125 BC)
Hipparcos
Hipparcos Catalogue
Hippias of Elis (fl. 5th century B.C.)
hippocampus
hippopede
Hirayama family
HIRES
histamine
histidine
histones
HISTORY OF ASTRONOMY
HISTORY OF SCIENCE
Hiten
hive intelligence
Hoag’s Object (PGC 54559)
Hoba meteorite
Hobby-Eberly Telescope (HET)
Hockey Stick Galaxy (NGC 4656)
Hodgkin's disease
Hodgkin's disease treatment
Hodierna, Giovanni Battista (1597-1660)
Hoerner, Sebastien von (1919-2003)
Hofstadter, Douglas R. (1945-)
Hogben, Lancelot Thomas (1895-1975)
Hohmann, Walter (1880-1945)
Hohmann orbit
hold
hold-down test
holding fixture
holding pond
hole
hole (topology)
hole in the heart
hole-in-a-postcard problem
hole-through-a-sphere problem
hole-through-the-Earth problem
holism
holistic
Holmberg, Erik Bertil (1908-2000)
Holmberg II Dwarf Irregular Galaxy
Holmberg radius
Holocene
holodeck
Holter monitor
homeomorphic
homeomorphism
homeostasis
homeotherm
hominid
hominoid
homokaryotic
homologous recombination
homologous series
homology
homomorphism
homosporous
homotopy
homozygous
Hooke, Robert (1635-1703)
Hooke's law
Hoover, George W.
HOPE (H-2 Orbital Plane)
Hopkins, Budd
horizon
horizon problem
horizontal branch
horizontal preflight checkout
Horologium (constellation)
hormone
hormone replacement therapy (HRT)
hornblende
hornito
Horowitz, Norman H. (1915-)
Horowitz, Paul (1942-)
Horrocks, Jeremiah (c. 1618-1641)
Horsehead Nebula (Barnard 33)
horst
host star
"hot Jupiter"
hot spot
hot subdwarf
hot test
HOTOL (Horizontal Takeoff and Landing vehicle)
hour
hour angle
hour circle
Hourglass Nebula (MyCn 18)
housekeeping
howardite
Hoyle, Fred (1915-2001)
HR 4796A
HR 810
HRMS
HST
Huang, Su-Shu (1915-)
Hubble, Edwin Powell (1889-1953)
Hubble constant
Hubble flow
Hubble law
Hubble radius
Hubble Space Telescope (HST)
Hubble’s Variable Nebula (NGC 2261)
Huggins, Margaret Lindsay (1848-1915)
Huggins, William (1824-1910)
Hulse-Taylor Pulsar (PSR 1913+16)
human artificial chromosome
human factors
Human Genome Project
Human Research Facility (HRF)
Humason, Milton Lasell (1891-1972)
Humason, Comet (1961e)
humerus
hummock
humoral immunity
humpback whales, songs of
hundred
hundred fowls problem
Hund's rule
Hungaria group
Hunsaker, Jerome C. (1886-1984)
Hunter, J(ames) A(lston) H(ope)
hunter’s moon
Huntington's disease
Hutton, Richard Holt (1826-1897)
Huxley, Thomas Henry (1825-1895)
Huygens, Christian (1629-1695)
Huygens Probe
Hyades
Hyakutake, Comet (C/1996 B2)
hybrid propellant
hybrid-propellant rocket engine
hybridization
Hydra (constellation)
Hydra (organism)
hydraulics
hydrazine
hydride
hydrobot
hydrocarbon
hydrocephalus
hydrochloric acid
hydrodynamics
hydrogen
hydrogen bond
hydrogen burning
hydrogen cyanide
hydrogen ion
hydrogen peroxide
hydrogen spectrum
hydrogen sulfide
hydrolysis
hydrophilic
hydrophobic
hydrostatic equilibrium
hydrostatics
hydrothermal vent
hydroxide
hydroxyl radical
Hydrus (constellation)
Hygiea (minor planet 10)
Hynek, J. Allen (1910-1986)
hyoid
Hypatia of Alexandria (c. AD 370-417)
hyperbola
hyperbolic geometry
hyperbolic orbit
hyperbolic spiral
hyperbolic velocity
hyperboloid
hypercube
hyperfactorial
hyperfine structure
hypergeometric function
hypergiant
hypergolic propellant
hypergravity
Hyperion
Hyperion photo gallery
hypernova
hyperon
hyperopia (far-sightedness)
hyperreal number
hypersensitization
hypersonic
hyperspace
hypersphere
hypersthene
hyperthermophiles
hypervelocity gun
hypervelocity impact
hypervelocity star
hypha
hypocycloid
hypodermis
hypoglossal nerve
hypotension (low blood pressure)
hypotenuse
hypothesis
hypothalamus
hypothermia
hypotrochoid
hypoxia
hysterectomy
hysteresis loop
HZ
HZ Herculis star