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Flashcards by Omar Nassar, updated about 1 month ago
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Created by Omar Nassar
about 2 months ago
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| Question | Answer |
| Mercury | Mercury, the smallest planet (radius 2440 km, mass 3.30×10^23 kg), is closest to the Sun at 0.39 AU with an orbital period of 88 days. It has no atmosphere to retain heat, so surface temps swing from 430°C (day) to –180°C (night). Its surface is heavily cratered, like the Moon, with smooth plains formed by ancient volcanism. Mercury has a large iron-rich core (~85% of its radius) generating a weak magnetic field, unusual for such a small planet. Gravity = 3.7 m/s². Orbital velocity ≈ 47 km/s. Equation for orbital period: T = 2π√(a³/GM☉), where a = semi-major axis (0.39 AU). Radar shows water ice in permanently shadowed craters at poles. Key mission: BepiColombo (ESA/JAXA, en route). Mercury helps scientists study planetary differentiation, solar wind interactions, and conditions near the Sun. |
| Jupiter | Jupiter, the largest planet (radius 69,911 km, mass 1.898×10^27 kg), orbits at 5.2 AU with a 11.86-year period and rapid 9.9-hour rotation, producing strong equatorial bulge and banded cloud patterns. Atmosphere mostly H₂ and He with storms like the Great Red Spot. Gravity = 24.79 m/s², escape velocity ≈ 59.5 km/s. Probes: Pioneer 10 & 11, Voyager 1 & 2, Galileo (including atmospheric probe 1995), Ulysses flyby, Cassini flyby, New Horizons flyby, Juno orbiter. Jupiter has 95+ moons, including Galilean moons: Io (volcanically active), Europa (subsurface ocean), Ganymede (largest moon), Callisto (heavily cratered). Kepler’s Law T² = a³ applies for satellite orbital periods. Jupiter’s strong magnetosphere and radiation belts provide natural labs for magnetohydrodynamics and planetary magnetism. |
| Saturn | Saturn, the second-largest planet (radius 58,232 km, mass 5.683×10^26 kg), orbits at 9.58 AU with a 29.5-year period and rotates in 10.7 hours, producing noticeable oblateness. Its atmosphere is mostly H₂ and He with banded cloud layers and long-lived storms; notable are its rings composed of ice and rock particles from micrometers to meters in size. Gravity = 10.44 m/s², escape velocity ≈ 35.5 km/s. Probes: Pioneer 11, Voyager 1 & 2, Cassini orbiter (2004–2017, included Huygens probe landing on Titan). Saturn has 83 confirmed moons; Titan has a thick N₂ atmosphere and methane lakes, Enceladus ejects water ice geysers from a subsurface ocean, Mimas, Rhea, Iapetus, and Dione have unique surfaces and ring interactions. Kepler’s Law T² = a³ governs orbital periods of moons. Saturn provides insights into ring dynamics, gas giant atmospheres, and potential habitable ocean worlds like Enceladus. |
| Uranus | Uranus, an ice giant (radius 25,362 km, mass 8.681×10^25 kg), orbits at 19.2 AU with an 84-year period and rotates in 17.2 hours on a 98° tilted axis, causing extreme seasonal variations. Its atmosphere is mostly H₂, He, and CH₄, giving a blue-green color, with faint rings and 27 known moons including Miranda, Ariel, Umbriel, Titania, and Oberon. Gravity = 8.69 m/s², escape velocity ≈ 21.3 km/s. Only visited by Voyager 2 (1986 flyby), which discovered the tilted magnetic field, unusual rotation, and complex moon surfaces. Kepler’s Law T² = a³ applies for moon orbits. Uranus provides unique insight into axial tilts, ice giant composition, and planetary magnetic fields, crucial for understanding formation of outer Solar System planets. |
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Neptune
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Neptune, an ice giant (radius 24,622 km, mass 1.024×10^26 kg), orbits at 30.1 AU with a 165-year period and rotates in 16.1 hours, producing strong winds up to 2,100 km/h. Its atmosphere is mostly H₂, He, and CH₄, giving a vivid blue color, with faint rings and 14 known moons, including Triton, which orbits retrograde and has geysers indicating subsurface activity. Gravity = 11.15 m/s², escape velocity ≈ 23.5 km/s. Voyager 2 (1989 flyby) is the only probe to visit, revealing Neptune’s Great Dark Spot, moon surfaces, and magnetic field tilted 47° from rotation axis. Kepler’s Law T² = a³ governs satellite orbital periods. Neptune helps study ice giant structure, extreme weather, magnetospheres, and captured moons’ dynamics. |
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Pluto
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Pluto, a dwarf planet (radius 1,188 km, mass 1.309×10^22 kg), orbits at 39.5 AU with a 248-year period and has a 6.4-day rotation. Its surface is composed of nitrogen, methane, and carbon monoxide ices, with mountains, plains, and a thin N₂ atmosphere that expands when near perihelion. Gravity = 0.62 m/s², escape velocity ≈ 1.2 km/s. Probes: New Horizons (2015 flyby) revealed heart-shaped Tombaugh Regio, icy mountains, glaciers, and complex geology, along with five known moons including Charon. Pluto’s eccentric orbit (e=0.248) and 17° inclination make it a key object for studying Kuiper Belt dynamics, dwarf planet geology, and atmospheric escape processes. |
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Ceres
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Ceres, the largest object in the asteroid belt (radius 473 km, mass 9.39×10^20 kg), orbits at 2.77 AU with a 4.6-year period and rotates every 9.1 hours. Its surface is a mixture of water ice and hydrated minerals, with bright spots of sodium carbonate in Occator Crater indicating past or present cryovolcanism. Gravity = 0.27 m/s², escape velocity ≈ 0.51 km/s. Probes: Dawn (2015–2018 orbit) mapped surface features, composition, and internal structure, confirming a differentiated body with a rocky core and icy mantle. Ceres provides insight into early Solar System formation, planetary differentiation, and water distribution in small bodies. |
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Earths Moon
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The Moon, Earth’s only natural satellite (radius 1,737 km, mass 7.35×10^22 kg), orbits at 384,400 km with a 27.3-day period and is tidally locked, always showing the same face to Earth. Surface features include maria (basalt plains), highlands, and craters like Tycho; gravity = 1.62 m/s², escape velocity ≈ 2.38 km/s. Probes: Luna series, Ranger, Surveyor, Apollo missions (1969–1972, six crewed landings), Lunar Reconnaissance Orbiter (2009–present) mapped topography, composition, and water ice in shadowed craters. The Moon influences Earth’s tides and stabilizes axial tilt. Kepler’s Law T² = a³ applies to lunar orbit. Its regolith, formation from a giant impact, and volcanism provide insights into planetary formation, differentiation, and impact cratering in the inner Solar System. |
| Triton | Triton, Neptune’s largest moon (radius 1,353 km, mass 2.14×10^22 kg), orbits retrograde at 354,800 km with a 5.88-day period, indicating it was likely captured from the Kuiper Belt. Surface is icy with nitrogen and methane, featuring geysers and cantaloupe terrain from cryovolcanism. Gravity = 0.78 m/s², escape velocity ≈ 1.5 km/s. Probes: Voyager 2 (1989 flyby) revealed active geysers, thin atmosphere, and a young surface with few craters. Kepler’s Law T² = a³ applies for orbit calculations. Triton’s retrograde motion, cryovolcanism, and tidal heating provide critical data for studying captured moons, icy geology, and outer Solar System evolution. |
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25143 Itokawa
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25143 Itokawa is a near-Earth asteroid (length ~535 m, mass ~3.5×10^10 kg) of the S-type, orbiting the Sun at 1.3 AU with a 1.52-year period and rotating every 12.1 hours. Its surface is rubble-pile in structure, consisting of boulders, gravel, and regolith. Gravity = 0.0001 m/s², escape velocity ≈ 0.0003 km/s. Probes: Hayabusa (2003–2010) visited Itokawa, collected samples, and returned them to Earth, confirming its composition matches ordinary chondrite meteorites. Studying Itokawa provides insight into asteroid formation, small-body gravity, surface regolith behavior, and the link between meteorites and parent bodies. |
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Tempel 1
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Tempel 1 is a short-period comet (orbital period 5.5 years, perihelion 1.5 AU, aphelion 4.7 AU) composed of ice, dust, and organic compounds. Gravity is extremely low, ~10⁻⁴ m/s², escape velocity ≈ 1 m/s. Probes: Deep Impact (2005) released an impactor to study interior composition, revealing abundant water ice, dust, and organics. Stardust (2004 flyby) also observed the comet’s coma and tail. Tempel 1 provides critical data on cometary structure, evolution, and primordial Solar System materials, informing theories of water and organic delivery to Earth. |
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486958 Arrokoth
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486598 Arrokoth, a Kuiper Belt object (~36×18 km), orbits at 44.6 AU with a 298-year period, composed of two lobes joined together (contact binary) of ice and organic-rich materials. Gravity ≈ 0.0003 m/s², escape velocity ≈ 0.03 m/s. Probes: New Horizons (2019 flyby) provided high-resolution images of its surface, revealing a smooth, lightly cratered terrain, red coloration from tholins, and primordial shape suggesting gentle accretion in the early Solar System. Arrokoth offers insight into planetesimal formation, binary object evolution, and outer Solar System chemistry. |
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HL Tauri Protoplanetary Disk
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HL Tauri is a young T Tauri star (~0.5 million years old) in the Taurus molecular cloud, ~450 light-years from Earth, surrounded by a protoplanetary disk of gas and dust observed in millimeter wavelengths. Gravity at the star’s surface ≈ 0.3 g, escape velocity ≈ 400 km/s. Telescopes: ALMA provided high-resolution images revealing concentric rings and gaps, indicating early planet formation. HL Tauri’s disk helps scientists study accretion processes, dust coagulation, and how planetary systems form in the first million years, offering a benchmark for models of planet formation. |
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51 Pegasi (Star)
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51 Pegasi is a Sun-like star (~1.11 M☉, radius 1.24 R☉) located 50 light-years away in Pegasus, known for hosting the first confirmed exoplanet around a main-sequence star, 51 Pegasi b, discovered in 1995 via radial velocity method. 51 Pegasi b is a hot Jupiter (~0.47 MJ, ~0.05 AU orbital distance) with a 4.23-day period, tidally locked, and its mass and orbit were derived using the equation Δv = (K·P·√(1–e²))/(2π) for radial velocity amplitude K. This discovery confirmed that planets exist around other stars and initiated the modern exoplanet era, providing a template for studying close-in gas giants and stellar-planet interactions. |
| HD 209458 | HD 209458 is a Sun-like star (~1.1 M☉, 1.2 R☉) located ~159 light-years away in Pegasus, hosting the transiting exoplanet HD 209458 b (“Osiris”), a hot Jupiter (~0.69 MJ, radius 1.38 RJ) orbiting at 0.047 AU with a 3.5-day period. The planet’s atmosphere evaporates due to intense stellar radiation, producing a comet-like tail of hydrogen, carbon, and oxygen. Gravity on the planet ≈ 9.4 m/s². Transit depth ΔF = (Rp/Rs)² relates planet radius to stellar radius. Probes/Telescopes: Hubble Space Telescope detected atmospheric escape and absorption lines. HD 209458 b provides insight into close-in gas giants, atmospheric loss, and |
| HD 209458b | HD 209458 b, nicknamed “Osiris,” is a hot Jupiter exoplanet (~0.69 MJ, 1.38 RJ) orbiting the Sun-like star HD 209458 (~1.1 M☉, 1.2 R☉) at 0.047 AU with a 3.5-day period. It was the first exoplanet observed transiting its star (1999), allowing measurement of radius, mass, and atmospheric properties. The planet’s atmosphere evaporates due to intense stellar radiation, producing a hydrogen, carbon, and oxygen tail. Gravity ≈ 9.4 m/s². Transit depth ΔF = (Rp/Rs)² relates planet radius to stellar radius. Hubble detected atmospheric escape and absorption lines, revealing upper-atmosphere dynamics. HD 209458 b is a benchmark for studying close-in gas giants, tidal locking, and exoplanetary atmospheres. |
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Beta Pictoris
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Beta Pictoris is a young (~20 Myr) A-type star (~1.75 M☉, 1.8 R☉) ~63 light-years away in Pictor, surrounded by a debris disk with gas and dust. Beta Pictoris b, a massive exoplanet (~13 MJ, ~9 AU), was discovered via direct imaging in 2008, orbiting every ~20 years with surface temperature ~1700 K due to residual formation heat. Probes/Telescopes: VLT and other ground-based observatories captured direct images; Hubble observed disk warps caused by planetary perturbations. Gravity on Beta Pictoris b ≈ 250 m/s². The system is a benchmark for studying planet formation, disk-planet interactions, and early dynamical evolution of planetary systems. |
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Beta Pictoris B
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Beta Pictoris b is a massive exoplanet (~13 MJ, radius ~1.65 RJ) orbiting the young A-type star Beta Pictoris (~1.75 M☉, 1.8 R☉) at ~9 AU with a ~20-year period. Surface temperature ~1700 K due to residual heat from formation. Gravity ≈ 250 m/s², escape velocity ≈ 60 km/s. Discovered via direct imaging in 2008, it orbits within a dusty debris disk, creating warps and gaps observable by Hubble and VLT. The system provides critical insights into planet formation, early dynamical evolution, and disk-planet interactions, serving as a model for studying young planetary systems. |
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Bepi Columbo
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BepiColombo is a joint ESA/JAXA mission launched in 2018 to study Mercury. It consists of two orbiters: the Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO), designed to investigate Mercury’s surface, composition, magnetic field, exosphere, and magnetosphere. The spacecraft uses solar-electric propulsion and gravity assists from Earth, Venus, and Mercury to reach orbit in 2025. Key instruments include magnetometers, spectrometers, and imaging systems. BepiColombo builds on MESSENGER data, aiming to improve understanding of Mercury’s core, geological history, magnetic field generation, and its extreme space environment, providing high-resolution mapping, gravity field measurements, and insights into planet formation near the Sun. |
| Galileo | Galileo was a NASA mission launched in 1989 to study Jupiter and its moons, entering Jupiter orbit in 1995. It carried an atmospheric probe that descended into Jupiter’s atmosphere, measuring composition, temperature, and pressure. The orbiter mapped the Galilean moons (Io, Europa, Ganymede, Callisto), revealing Io’s volcanism, Europa’s possible subsurface ocean, and Ganymede’s magnetic field. Galileo studied Jupiter’s strong radiation belts, magnetosphere, and atmospheric dynamics, including the Great Red Spot and zonal winds. Gravity assists from Venus and Earth enabled its journey. The mission provided unprecedented data on gas giant systems, satellite geology, magnetic fields, and planetary formation, shaping models of giant planet evolution. |
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Juno
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Juno is a NASA mission launched in 2011 to study Jupiter’s composition, gravity field, magnetic field, and polar magnetosphere. It entered Jupiter orbit in 2016 using a highly elliptical polar orbit to avoid radiation belts. Instruments include a microwave radiometer to probe atmospheric composition and temperature, magnetometers for mapping the magnetic field, and JunoCam for imaging clouds and polar auroras. Gravity measurements allow determination of core mass and internal structure. Juno provides insights into Jupiter’s formation, planetary differentiation, and magnetic field generation, helping scientists understand gas giant evolution and Solar System formation. |
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Cassini
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Cassini was a NASA/ESA/ASI mission launched in 1997 to study Saturn, its rings, moons, and magnetosphere, entering orbit in 2004 and operating until 2017. It carried 12 instruments, including radar, spectrometers, and magnetometers, and deployed the Huygens probe, which landed on Titan in 2005, revealing lakes of methane and ethane and a thick nitrogen atmosphere. Cassini studied Saturn’s rings, Enceladus’ geysers, and magnetic environment, providing high-resolution mapping and gravity measurements. Gravity assists from Venus, Earth, and Jupiter enabled the journey. Cassini greatly advanced understanding of gas giant systems, icy moon habitability, ring dynamics, and planetary magnetospheres. |
| Voyager 2 | Voyager 2, launched by NASA in 1977, conducted a “Grand Tour” of the outer planets: Jupiter (1979), Saturn (1981), Uranus (1986), and Neptune (1989). It carried cameras, spectrometers, magnetometers, and plasma detectors to study planetary atmospheres, magnetic fields, rings, and moons. Voyager 2 discovered active volcanism on Io, intricate Saturn and Uranus rings, and Neptune’s Great Dark Spot. It provided gravity measurements, temperature, and composition data, and is now traveling through interstellar space, carrying the Golden Record with Earth sounds and images. Its mission revolutionized knowledge of the outer Solar System and planetary magnetospheres. |
| New Horizons | New Horizons is a NASA mission launched in 2006 to study Pluto, its moons, and Kuiper Belt objects. It conducted a flyby of Jupiter in 2007 for gravity assist and instrument calibration, then reached Pluto in 2015, providing high-resolution maps of its surface, including Tombaugh Regio, icy mountains, glaciers, and Charon. In 2019, it flew by Kuiper Belt object 486598 Arrokoth, revealing a contact binary with primordial surface features. Instruments include cameras, spectrometers, and particle detectors to study composition, atmosphere, and geology. New Horizons helps understand dwarf planets, Kuiper Belt objects, and the outer Solar System’s formation and evolution. |
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Dawn
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Dawn was a NASA mission launched in 2007 to study the two largest bodies in the asteroid belt, Vesta and Ceres, using ion propulsion. It orbited Vesta (2011–2012) and Ceres (2015–2018), mapping surface composition, topography, and gravity fields. Dawn discovered Vesta’s differentiated structure, giant impact basins, and Ceres’ cryovolcanic features like bright spots in Occator Crater. Instruments included cameras, spectrometers, and a gamma-ray/neutron detector. Gravity and orbital data helped determine internal structure and density. Dawn provided insights into early Solar System formation, planetary differentiation, asteroid belt evolution, and the role of water and ice in small bodies. |
| Lunar Reconnaissance Orbiter (LRO) | The Lunar Reconnaissance Orbiter (LRO), launched by NASA in 2009, maps the Moon’s surface in high resolution to study topography, composition, and potential resources. Instruments include cameras, a laser altimeter, a neutron detector, and a thermal mapper. LRO discovered water ice in permanently shadowed craters, measured surface temperatures, and created detailed maps of lunar terrain for future exploration. Gravity data improves models of the Moon’s internal structure. The mission provides crucial information for understanding the Moon’s geology, regolith properties, impact history, and potential sites for crewed missions. |
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Hayabusa
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Hayabusa, launched by JAXA in 2003, is a sample-return mission to the near-Earth asteroid 25143 Itokawa (~535 m). It rendezvoused with Itokawa in 2005, analyzed surface composition with cameras, spectrometers, and particle detectors, and collected dust samples using a touch-and-go mechanism. The spacecraft returned to Earth in 2010, confirming that Itokawa’s composition matches ordinary chondrite meteorites. Hayabusa provided critical data on asteroid surface structure, regolith behavior in microgravity, and techniques for future sample-return missions, advancing knowledge of small-body formation, evolution, and links to meteorites on Earth. |
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Deep Impact
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Deep Impact, launched by NASA in 2005, studied comet 9P/Tempel 1 by releasing an impactor to excavate subsurface material. The main spacecraft observed the ejecta with cameras and spectrometers, revealing water ice, dust, and organic compounds. Gravity on the comet ≈ 10⁻⁴ m/s², escape velocity ≈ 1 m/s. Deep Impact provided critical data on comet composition, structure, and evolution, offering insight into the early Solar System and the role of comets in delivering water and organics to Earth. |
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ALMA (Atacama Millimeter/submillimeter Array)
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ALMA (Atacama Large Millimeter/submillimeter Array) is an international telescope array in Chile, consisting of 66 high-precision antennas observing millimeter and submillimeter wavelengths. It studies cold objects like protoplanetary disks, molecular clouds, comets, and distant galaxies. ALMA’s high resolution allows imaging of planet-forming disks, such as HL Tauri, revealing rings, gaps, and dust structures, and measures molecular compositions to trace star and planet formation. Observations use interferometry: baseline B between antennas improves resolution θ ≈ λ/B. ALMA is key for understanding early planetary systems, disk evolution, and chemistry of the interstellar medium. |
| Hubble | The Hubble Space Telescope, launched in 1990, observes in ultraviolet, visible, and near-infrared wavelengths from low Earth orbit (~547 km). Instruments include cameras, spectrographs, and fine guidance sensors, enabling high-resolution imaging and spectroscopy. Hubble has studied planets, moons, comets, exoplanets (e.g., HD 209458 b), star formation, galaxies, and cosmology. Key contributions include measuring the Hubble constant, imaging protoplanetary disks, observing atmospheric escape on exoplanets, and discovering distant galaxies. Its stability allows precise measurements: diffraction limit θ ≈ 1.22 λ/D. Hubble revolutionized astronomy, providing a foundation for planetary science and astrophysics. |
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James Web Space Telescope (JWST)
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The James Webb Space Telescope (JWST), launched in 2021, observes in infrared (0.6–28 μm) from the Sun-Earth L2 point (~1.5 million km). Its 6.5 m segmented primary mirror and instruments (NIRCam, NIRSpec, MIRI, FGS/NIRISS) enable high-resolution imaging and spectroscopy of exoplanets, protoplanetary disks, distant galaxies, and early universe objects. JWST uses transit spectroscopy to analyze exoplanet atmospheres (e.g., HD 209458 b), measuring absorption ΔF = (Rp/Rs)². It can detect water, methane, CO₂, and other molecules, advancing understanding of planet formation, chemical evolution, and cosmology. JWST complements Hubble, extending observations into longer wavelengths and fainter objects. |
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