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from article Precession of equinoxes
Motion of the Earth's axis of rotation.
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from article Cosmic background radiation
Timeline of the origin and evolution of the universe from a hot, dense state (left) to the current star-and galaxy-filled cosmos that arose over eons of the universe’s history and through today (right). The cosmic microwave background, labeled the…
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from article Cosmic background radiation
The most detailed map ever made of the cosmic microwave background, a snapshot of the universe at 380,000 years of age, obtained by the Planck spacecraft during its observing run from 2009 to 2013. Anisotropies—tiny temperature fluctuations—are…
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from article Cosmic background radiation
The 15-meter horn antenna at Bell Telephone Laboratories in Holmdel, New Jersey where the first detection of the cosmic microwave background was made. (Credit: NASA)
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from article Venus Express
An artist's impression of the Venus Express spacecraft orbiting Venus. (Credit: ESA)
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from article Venus Express
False color image of cloud features of Venus at wavelength of 1.73 μm in the infrared, viewed by VIRTIS on Venus Express. (Credit: ESA/VIRTIS/INAF–ASF/Paris Observatory–LESIA)
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from article Venus Express
The science instruments onboard Venus Express. (Credit: ESA)
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from article Venus Express
The solar wind, illustrated in lines propagating from the Sun, as it interacts with the magnetosphere of Venus, generating a magnetotail (colored brown and emanating from the planetary body close to the Sun). Earth's magnetosphere, depicted in blue,…
Image
from article Venus Express
An artist's impression of an active volcano erupting on the surface of Venus. (Credit: ESA/AOES)
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from article Aircraft instrumentation
Cockpit displays and flight engineer's instruments in Boeing 747. (Boeing Co.)
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from article Aircraft instrumentation
Flight deck mock-up of Boeing 767 configuration for crew of three. (Boeing Co.)
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from article Aircraft instrumentation
Ring laser gyro operation. (Honeywell, Inc.)
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from article Aircraft instrumentation
Electronic attitude-director indicator (EADI). (Boeing/Collins)
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from article Aircraft instrumentation
Electronic horizontal-situation indicator (EHSI) map mode. (Boeing/Collins)
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from article Aircraft instrumentation
Caution and warning display. (a) Configuration of elements. (b) Location of elements on aircraft instrument panel. (Boeing Co.)
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from article Aircraft instrumentation
Two-crew engine-indication and crew-alerting system (EICAS). (a) Configuration of the elements. (b) Location of the elements as they occur on an aircraft instrument panel. (Boeing Co.)
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from article Light pollution
Photographs taken at night of the same house in Goodwood, Ontario, located about 60 km (37 mi) northeast of Toronto, Canada, before and after the August 2003 blackout. At left, before the blackout, sky glow is plainly visible. At right, after the…
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from article Light pollution
At left, the former Sixth Street Viaduct over the Los Angeles River in the city of Los Angeles, prior to a light pollution-reducing upgrade to the roadway's light fixtures completed by 2012. At right, replacement lighting reduced uplighting, and…
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from article Adaptive optics
Typical adaptive optics system using discrete components.
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from article Adaptive optics
Adaptive optical system using a laser beacon (guide star).
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from article Adaptive optics
Images of the Trapezium region in the Orion Nebula, obtained by using adaptive optics with a laser beacon reference source and a 241-actuator deformable mirror on a 1.5-m (59-in.) telescope. Fields of view are 40 arc-seconds square. (a) Uncorrected…
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from article Pisces (constellation)
Modern boundaries of the constellation Pisces, the Fishes. The celestial equator is 0° of declination, which corresponds to celestial latitude. Right ascension corresponds to celestial longitude, with each hour of right ascension representing 15° of…
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from article Sextant
Marine sextant.
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from article Sextant
Periscopic sextant for use in aircraft.
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from article Earth rotation and orbital motion
Excess length of day [length of day − 86,400 atomic Système International (SI) seconds], measured in milliseconds.
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from article Earth rotation and orbital motion
Couple produced by tidal friction.
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from article Earth rotation and orbital motion
Schematic representation of the Earth's orbit.
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from article Earth rotation and orbital motion
Equation of time.
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from article Earth rotation and orbital motion
Precession/nutation and polar motion.
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from article Air-traffic control
Terminal radar controller's plan view display. Aircraft positions are shown by radar returns. Display is centered on primary airport with parallel and intersecting runways. Range rings are spaced 5 mi (9 km) apart. Airspace within boundary and above…
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from article Solar neutrino
A composite of 25 separate images taken by NASA’s Solar Dynamics Observatory (SDO) between February 2013 and February 2014. The composite images indicate regions in the Sun’s mid-latitudes where the body is most actively erupting with solar flares.…
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from article Sloan Digital Sky Survey
Sloan Digital Sky Survey (SDSS) 2.5-m (98-in.) telescope at Apache Point Observatory, New Mexico. The secondary mirror is visible in the center of the aperture. The square structure surrounding the primary and secondary mirrors shelters them from…
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from article Sloan Digital Sky Survey
Spectrum of a galaxy (image inset) receding at around 6000 km s−1 (3700 mi s−1), or about 2% of the speed of light. The vertical line shows the wavelength at which one expects to observe the emission line Hα for an object at rest (656.3 nm). The…
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from article Sloan Digital Sky Survey
Distribution of galaxies within 4° of the celestial equator from the SDSS. In this polar plot, the radius indicates the distance from the Milky Way, and the angle is the right ascension. The diameter shown is 8 × 109 light-years. Blank areas have…
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from article Sloan Digital Sky Survey
Map of stars in the SDSS. Grayscale signifies density of stars on the sky. Several streams of stars are noticeable. Areas in background are those unobserved by the survey. (Courtesy of Vasily Belokurov; Sloan Digital Sky Survey)
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from article Sloan Digital Sky Survey
Image of Canes Venatici I, a recently discovered satellite of the Milky Way Galaxy. (Photo courtesy of Vasily Belokurov; Sloan Digital Sky Survey)
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from article Sloan Digital Sky Survey
Hubble sequence of galaxies, as observed by the SDSS. Elliptical galaxies (types marked E0 and E6) are old, spheroidal, and very massive. Spiral galaxies are on average less massive. While some spiral galaxies (S0 and Sa) tend to have very little…
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from article Binary and multiple asteroids
Asteroid 121 Hermione and its moonlet companion observed with the adaptive optics system mounted on the European Southern Observatory's Very Large Telescope [consisting of four 8.2-m (25-ft) telescopes] at six different times. The satellite revolves…
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from article Neutrino astronomy
An image of the IceCube Neutrino Observatory’s Antarctic lab at top with an illustration at bottom of the long strings of sensors deployed in a cubic kilometer of ice around the lab. These sensors detect the light given off by particles forming from…
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from article Neutrino astronomy
An illustration depicting how different kinds of cosmic “messengers” travel through space to detectors on Earth. Photons, particles of light, interact through the electromagnetic force with matter between their origin point and Earth, absorbing and…
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from article Neutrino astronomy
A Hubble Space Telescope image of Supernova 1987A twenty years after its initial explosion in a neighboring galaxy. A seminal event in neutrino astronomy, detectors captured neutrinos from the supernova before astronomers otherwise discovered its…
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from article Retrograde motion (astronomy)
A planetarium simulation of a retrograde loop for the planet Mars. Some retrograde loops are open like this one while others are closed. (Image with Zeiss ZKP3/B planetarium projector of Williams College's Hopkins Observatory, courtesy of Jay M.…
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from article Retrograde motion (astronomy)
Ptolemy's theory of retrograde motion. (a) Small circles, called epicycles, revolve on larger circles, called deferents. (b) To account for the unevenness of the seasons of the year, the planets orbit uniformly around a point known as the equant,…
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from article Retrograde motion (astronomy)
Copernicus's explanation of retrograde motion for the planet Mars. Planets appear to have retrograde motion because of an optical illusion as an inner planet passes the Earth or as the Earth passes an outer planet. (Courtesy of Jay M. Pasachoff and…
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from article Van Allen radiation
Motion of a proton trapped in the geomagnetic field.
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from article Van Allen radiation
Structure of Earth's radiation belts. Protons (E > 15 MeV) are shown on the right, and electrons (E > 0.5 MeV) are shown on the left. Darker shading indicates more intense fluxes of trapped particles.
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from article Van Allen radiation
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from article Van Allen radiation
Time variations in the magnetic activity index Kp and the associated changes in the flux of trapped electrons (E >0.5 MeV) at an altitude of 4 Re.
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from article Celestial sphere
Celestial sphere. The arrows indicate the right ascension (RA) and declination (Dec) of Sirius. (Wil Tirion)
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from article Underwater navigation
Acoustic navigation systems, which employ various equipment.
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from article Underwater navigation
Deep-ocean navigation transponder. This beacon is about 55 in. (140 cm) in length and 5 in. (12.5 cm) in diameter. (Sona Tech, Inc.)
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from article Underwater navigation
Submersible navigating from underwater acoustic transponders.
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from article Underwater navigation
Configurations of three types of pilotage sonars.
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from article Underwater navigation
Sonar for tracking of divers from an underwater habitat. Display cathode-ray tube shows positions of divers to diving officer.
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from article Electronic navigation system
Two-way (round-trip) ranging system.
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from article Electronic navigation system
One-way synchronous ranging system.
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from article Electronic navigation system
Effect of relative geometry on accuracy of hyperbolic navigation systems. Accuracy largely depends on θ1 and θ2, the crossing angles at users 1 and 2.
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from article Big bang theory
Timeline of the origin and evolution of the universe from a hot, dense state (left) to the current star-and galaxy-filled cosmos that arose over eons of the universe’s history and through today (right). (Credit: NASA)
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from article Big bang theory
A timeline of the universe's evolution, from the big bang through present day. (Credit: NASA/ESA)
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from article Big bang theory
The universe approximately 400,000 years after it was born. This map of the temperature of the cosmic microwave background radiation, obtained by the Planck spacecraft between 2009 and 2013, shows tiny variations (of a few microdegrees) in the ∼3 K…
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from article Big bang theory
A pie chart assembled from Planck mission results observing the cosmic microwave background radiation, from which approximate figures for the universe's composition can be derived. (Credit: ESA/Planck)
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from article Astronomical spectroscopy
Spectrum of the largest H II region in the irregular galaxy NGC 1156. The continuum comes from the underlying stellar population. Forbidden lines of neutral and doubly ionized oxygen (O I, O III), singly ionized nitrogen (N II), and singly ionized…
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from article Astronomical spectroscopy
Spectra of the star Sk-69° 22, one of the hottest, most luminous, and massive stars known, in the Large Magellanic Cloud. (a) Part of the optical spectrum, 0.375–0.478 μm. IS indicates absorption lines from interstellar gas. (b) Detailed spectrum of…
Image
from article Galileo mission
An artist's impression of the Galileo orbiter, with Jupiter in the background and the volcanic moon Io in the foreground. (Credit: NASA)
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from article Galileo mission
Galileo probe. All science instruments were housed in the descent module. (a) Probe prior to and during entry. (b) Exploded view. (c) Probe during descent.
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from article Galileo mission
Probe mission profile. Altitude is referenced to the level at which pressure is 1 bar. (1 bar equals sea-level surface pressure on Earth.) The last signal was received from the probe at 61.4 min after entry, near 24-bar pressure. 1 km = 0.6 mi.…
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from article Galileo mission
Galileo enhanced color composite image of Io taken on September 19, 1997, at a distance of more than 500,000 km (310,000 mi). Deposits of sulfur dioxide frost appear as white and grey hues, with other sulfurous materials contributing the yellow and…
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from article Galileo mission
View of Jupiter's Great Red Spot taken by Galileo on June 26, 1996. (Credit: NASA/JPL/Cornell University)
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from article Galileo mission
Mosaic of four Galileo high-resolution images of the Uruk Sulcus region of Ganymede, shown within the context of an image of the region taken by Voyager 2 in 1979, and further shown within a full image of Ganymede. The Galileo images were taken on…
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from article Galileo mission
Callisto, imaged by the Galileo orbiter in May 2001. (Credit: NASA/JPL/DLR)
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from article Galileo mission
Galileo orbiter image of Europa, based on observations from 1995 and 1998. (Credit: NASA/JPL-Caltech/SETI Institute)
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from article Galileo mission
An artist's impression of Galileo as it passed close to the small moon Amalthea. (Credit: Michael Carroll and NASA)
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from article Crux
Modern boundaries of the constellation Crux, the Southern Cross. The celestial equator is 0° of declination, which corresponds to celestial latitude. Right ascension corresponds to celestial longitude, with each hour of right ascension representing…
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from article Telescope
Multi-wavelength study of the core of the galaxy NGC 1512, revealing pockets of new star formation in both dust-obscured and clear regions. The Hubble Space Telescope obtained images of the galactic center in seven different wavelengths, from the…
Image
from article Telescope
A depiction of Galileo demonstrating the use of a telescope to a crowd in the 17th century. (Credit: Getty Images)
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from article Telescope
At the European Southern Observatory's Very Large Telescope (VLT) in Chile, one of the four 8.2-m unit telescopes beams a high-powered laser as part of its adaptive optics system. [Credit: ESO/A. Ghizzi Panizza (www.albertoghizzipanizza.com)]
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from article Telescope
Simplified optical diagram of a refracting telescope.
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from article Telescope
Refracting optical system used to photograph a star field.
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from article Telescope
Viewing a star with a reflecting telescope. For a small telescope, an observer at the prime focus shown would block the mirror, so various configurations and secondary mirrors are shown to provide the image at other locations. For larger telescopes,…
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from article Telescope
Diagrams of reflecting telescopes. (a) Cassegrain telescope, with either classical or Ritchey-Chrétien optics. (b) Newtonian telescope. The eyepieces or detectors are not shown.
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from article Telescope
The largest single telescope in the world, the 10.4-m (34.1-ft) Gran Telescopio Canarias, on La Palma, Canary Islands, Spain. (Credit: Instituto de Astrofísica de Canarias)
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from article Telescope
An artist's impression of the completed Giant Magellan Telescope, to be located at the Las Campanas Observatory in Chile. (Credit: GMTO Corporation)
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from article Telescope
Solar telescope configuration. (a) Swedish 1-m (40-in.) Solar Telescope of the Royal Academy of Sciences, located on La Palma, Canary Islands. (b) Diagram of the optical elements in the telescope. The 1-m lens is the largest in use.
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from article Telescope
The Hubble Space Telescope. (Credit: NASA)
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from article Pluto
Charon, pictured by New Horizons. (Credit: NASA/JHUAPL/SwRI)
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from article Herbig-Haro objects
Jet and bow-shock emission from Herbig-Haro 34. Two opposite jets run into the surrounding interstellar medium, where they terminate in Herbig-Haro objects with a characteristic bow-shock structure. The jets are composed of “bullets” of dense gas…
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from article Herbig-Haro objects
Spitzer Space Telescope infrared image and an optical Digital Sky Survey image of Herbig-Haro objects 46 and 47. The inset at the bottom left shows the optical image of the cloud in which the protostar is born and the associated Herbig-Haro objects…
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from article Herbig-Haro objects
Disk and jets associated with Herbig-Haro 30, showing changes between images taken in (a) 1995, (b) 1998 and (c) 2000 with the Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope. A slightly flared disk of dust and gas appears…
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from article Earth
The famous "Blue Marble" picture of Earth taken by astronauts during the Apollo 17 mission on December 7, 1972, while en route to the Moon. (Credit: NASA)
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from article Earth
Principal layers of Earth. (USGS)
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from article Earth
Global histogram (distribution of elevations) and hypsographic curve (cumulative elevations) of Earth's surface. (NOAA)
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from article Earth
Seafloor spreading. (USGS)
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from article Earth
Plate collisions: (a) continent-ocean plate collision; (b) continent-continent plate collision; (c) ocean-ocean plate collision. (USGS)
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from article Earth
Structure of the atmosphere. The log scale applies only to the ionization curve. 1 km = 0.6 mi; °F = (°C × 1.8) + 32.
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from article Star tracker
Strapdown satellite star tracker. (a) Mounting of system on the satellite. (b) Star tracker in housing. (Northrop Grumman Corp.)
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from article Star tracker
Silicon focal-plane arrays. (Northrop Grumman Corp.)
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from article Centaurus
Modern boundaries of the constellation Centaurus, the Centaur. The celestial equator is 0° of declination, which corresponds to celestial latitude. Right ascension corresponds to celestial longitude, with each hour of right ascension representing…
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from article Astronomical imaging
Cross-sectional view of the physical structure of an MOS capacitor. Positive voltage (usually a few volts) applied to the metal layer creates a depletion region in the semiconductor.
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from article Astronomical imaging
CCD components and readout. (a) Accumulated photoelectrons in a 3 × 3 array of capacitors. Reading the array: (b) The bottom row shifts into the serial register; all remaining rows shift down by one pixel in the parallel register. (c–e) Serial…
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from article Astronomical imaging
Gate structure in a three-phase buried-channel CCD. (a) Two pixels, in cross section. (b) Electron potential pn junction. Collection and barrier potentials on the gates isolate the pixels from each other during an exposure. Overlapping gates produce…
