Astro200 PDF

ASTRO200 Constellations = takım yıldızı The big dipper = büyük kepçe takımyıldızı Celestial sphere = dünyanın merkezde olduğu ve çevreini saran, kutuplarla ve ekvatorlar çakışık halde bulunan hayali gökkubbe Azimuth (directon): Starts from North, measured along East, South, West and back to Nort...

ASTRO200 Constellations = takım yıldızı The big dipper = büyük kepçe takımyıldızı Celestial sphere = dünyanın merkezde olduğu ve çevreini saran, kutuplarla ve ekvatorlar çakışık halde bulunan hayali gökkubbe Azimuth (directon): Starts from North, measured along East, South, West and back to North Altitude (elevation): Starts from the horizon rises up to Zenith Zenith = Meridian = an imaginary half circle North \> Zenith\> South Longtitude (along the rotation directon of Earth) Lattitude (subtended from Equator) Altitude of the Celestal Pole = Your Geographc Latitude Similarly each object on the celestal sphere can be identified from two angles = Right Ascension (how far an object, in minutes) Declination (how far from equador, in degrees) Sidereal Month: The time required to complete one revolution around Earth with respect to background stars Synodic Month: The period of completing phase cycle (eg. New Moon to New Moon) → 29.5 days (takes longer than Sidereal Month) **Definition of an eclipse:** Any time one astronomical object casts a shadow on another. **Definition of Nodes:** The two points in each orbit (Moon\'s around the Earth and Earth\'s around the Sun) at which the Moon crosses the ecliptic plane. **Solar vs Sidereal Day** - Solar Day = 24h 00m 00s (noon/midnight to noon/midnight) - Sidereal Day = 23h 56m 4.098s **Synodic vs Sidereal Month** - Synodic Month = 29.5 days (due to phases) - Sidereal Month = 27.3 days **Tropical vs Sidereal Year** - Tropical Year = 365 days - 20 minutes (due to seasons) - **Reason**: Precession of Earth\'s axis. Each year the location of the equinoxes and solstices among the stars shifts about 1/26 000 of the way around the orbit. This amounts to 1/26 000 \~ 20 minutes - Sidereal Year = 365 days **Planetary Periods** - **Sidereal Period:** It is the time it takes to orbit the Sun. - **Synodic Period:** It is the time between being lined up with the Sun in our sky one time, and the next similar alignment. - **Conjunction:** elongation of 0 degree (inferior: **Sun** - Planet - Earth; superior: Planet - **Sun** - Earth) - **Opposition:** elongation of 180 degrees - **Quadrature:** elongation of 90 degrees Precession = devinim Elongation = uzanım Wiens law, wavelength is in inversely proportional to the absolute temperature moving charges create disturbance (consists of both E and B). H2 and O2 absorbs Radio waves (. \< 1 cm) H2O and CO2 absorbs \... Infrared waves Ozone layer › absorbs \... UV, X-ray, Gamma rays Ionosphere reflects \.... \> 10 m. (the layer is at 100 km above sea level) **BLACK BODY CURVE** An object that ***absorbs* all radiation** falling on it and it must **re-emit** the same amount of energy it absorbs. No real object absorbs and radiates as a perfect black body. However, the blackbody curve is a good approximation to the reality. As the object\'s temperature increases → radiation\'s peak frequency shifts → however shape of the curve remains the same Optical Telescope: It is the one designed to collect wavelengths of radiation that are visible to human eye. Telescope Types Refracting: a lens focuses the light (focuses Red and Blue light differently) As light passes through the lens some of it is absorbed by the glass. This is important for IR and UV observations. Reflecting: a mirror focuses the light **Types of Telescope Designs** Prime Focus, Single reflection Newtonian, Double reflection. Cassegrain, Double reflection Nasmyth / Coude, Triple reflection **Special Telescopes** Schmidt. A coma (bright central object having a tailed structure) appears as we move away from the center of the field of view. Its size increases further away from the center. To correct the coma a correcting lens introduced right before the beam enters to the tube: **Angular Resolution:** It is the factor that determines our ability to see the fine structure. Resolution is proportional with **wavelength** and is inversely proportional with to **mirror size** As wavelength increases. diffraction increases angular resolution increases therefore resolving the objects gets worse **How to increase the diameter of a telescope today?** Combine them in an hexagonal (like a honeycomb) construction and align them to focus like a single mirror. This type of telescopes are called **segmented mirror telescopes.** **High Resolution Observations** In theory you can reach 0.02\" with a 5 meter telescope. But in reality you cannot do better than 1\". Reason: Earth\'s turbulent atmosphere which blurs the image even before the light reaches our instrument. the best angular resolution is slightly **\< 1\"** So, to achieve the best possible seeing, telescopes are sited on mountain tops **Current best resolutions** Hubble Space Telescope - 2.4 meter - 0.05\" NTT (Chile) - 3.5 meter - 0.5\" (active optics) Keck Telescopes - 10.0 meter - 0.25\" Longer wavelength means poor angular resolution. However, radio astronomy has different advantages too: Observations can be carried out for 24 hours. Cloud, rain and snow don\'t interfere the observation Interferometry**:** Combine information from several widely spread radio telescopes The largest single mirror telescope is BTA-6 (6 meters) in Zelenchukskaya, Caucasus build in 1976. Next largest is Hale Telescope (5 meters) in Palomar Observatory, California constructed in 1948! REFRACTION = KIRILMA The first asteroid: Ceres (1801) **5** Dwarf Planet 1801 - Ceres (asteroid belt) 1930 - Pluto 2004 - Haumea 2005 - Makemake & Eris **10** Large Asteroids Ceres, Pallas, Juna, Vesta, Astraea, Hebe, Iris, Flora, Metis, Hygenia **239** Asteroids (\> 100 km in diameter) **1 trillion** Comets (estimated) **6339** known Comets (as of 2018) **2. Measuring the Planets** **Distance** Known by **Kepler\'s Law** **Orbital Period** Obtained by **observation**: repeated observation of its location on the sky **Radius** Known by its **angular size** **Mass** Known by **Newton\'s Law**: gravity of moon\'s orbits around the planets **Ceres** is the most difficult one because of its very weak gravity. Now **space probes** are used to measure these parameters **Sun** occupies **99.9%** of the solar system! **VENUS, URANUS AND PLUTO HAS A BACKWARD ROTATİON** 4\. Grouping Terrestrial Planets Naming: earth land; Earth like Inner: mercury, venus, mars, earth All have atmospheres, All atmospheres are completely different Earth and Mars have similar spin rates Earth and Mars have moons Earth and Mercury have measurable magnetic fields Venus and Mars have none Jovian Planets Naming: Jove; god Jupiter; Jupiter like Outer: Jupiter Saturn Uranus, Neptune Kuiper belt = Kuiper Kuşağı, Güneş Sistemi\'nin kenarında bulunan bir halkadır. Esas olarak uzay kayaları ve cüce gezegenlerden oluşur. Neptün\'ün yörüngesinin ötesine oturur.  Oort cloud = Küre yapılı, buzlu bir zırh Güneş Sistemi\'nin etrafını sarmaktadır ve buna günümüzde Oort Bulutu adı veririz. Bu zırh, 5.000 ila 10.000 Astronomik Birim (AB) uzakta yer alır. **Interplanetary Matter = Relatively Large Bodies** **Asteroids (in between Mars and Jupiter)** **Kuiper Belt objects (beyond Neptune)** **Small Bodies** **Comets (at the end the solar system)** **Meteoroids (everywhere in the solar system)** **Asteroids and Comets = Asteroids are small, rocky bodies that orbit the Sun much like planets, but they are much smaller than planets.** **Most asteroids are found within the relatively wide gap between the orbits of Mars and Jupiter that marks the asteroid belt.** **Note the Trojan asteroids at two locations in Jupiter's orbit.** **Apollo orbits: Earth-crossing.** **Amor orbits: Mars-crossing.** **The largest:** **Ceres - 940 km** **Pallas - 580 km** **Vesta - 540 km (showing volcanism)** **Asteroid types:** **C-type: Carbonaceous, dark** **S-type: Silicate (rocky)** **M-type: Metallic; iron and nickel** **Kirkwood Gap** **Comets move in highly eccentric paths that carry them far beyond the known planets.** **The Kuiper belt comets orbit the Sun in the same direction as the planets, and their orbits generally lie close to the plane of planetary orbits.** **Oort cloud, may extend more than one-fourth of the way to the nearest stars.** **Comets in this region have orbits around the Sun that are inclined at all angles to the plane of planetary orbits and go in every possible direction around the Sun.** getting **smaller** ➤ Getting **denser** ➤ Getting **hotter** ➤ STAR **Nebular Theory: cloud ➤ bulge ➤ disk** (A galaxy\'s bulge is a central, football-shaped structure composed of stars, gas, and dust) **Condensation Theory = old Nebular Theory + interstellar chemistry** **The terrestrial planets = *The great differences in their present-day appearance must therefore be the result of changes that have occurred through time.*** **\#1: mercury** **4.6 billion years ago, due to bombardment** **Phases of Mercury can be seen best when Mercury is at its maximum elongation. (28 degrees)** **Elongation = uzama** Mercury was long thought to be tidally locked to the Sun; measurements in 1965 showed this to be false. Rather, Mercury's day and year are in a 3:2 resonance; Mercury rotates **three times** while going around the Sun **twice**. **Caloris Basin**, very large impact feature; weird terrain on opposite side of planet. (Caloris Planitia, yaklaşık 1.550 km çapında, gayri resmi olarak Caloris olarak adlandırılan, Merkür üzerindeki büyük bir etki havzasında yer alan bir ovadır. Güneş Sistemindeki en büyük çarpma havzalarından biridir.) "Weird terrain" is thought to result from focusing of seismic waves. \#2: VENUS Slow, retrograde rotation of Venus results in large difference between solar day (117 Earth days) and sidereal day (243 Earth days); both are large compared to the Venus year (225 Earth days). 117 EARTH DAY = 1 VENUS DAY Dense atmosphere and thick clouds make surface impossible to see. Atmosphere is mostly carbon dioxide; clouds are sulfuric acid There are also permanent vortices at the poles; the origin of the double-lobed structure is a mystery ( VORTICE = GİRDAP) No magnetic field, probably because rotation is so slow Because Venus's atmosphere is much deeper and denser than Earth's, a much smaller fraction of the infrared radiation leaving the planet's surface escapes into space. The result is a much stronger greenhouse effect than on Earth and a correspondingly hotter planet. Two continent-like features: Ishtar Terra and Aphrodite Terra Surface is smoother. Ovda Regio, part of Aphrodite Terra. Cleopatra showing a double-ringed structure. lava channel in Venus's south polar region, known as Lada Terra These dome-shaped structures resulted when viscous molten rock bulged out of the ground and then retreated, leaving behind a thin, solid crust that subsequently cracked and subsided. The first direct view of the surface of Venus, radioed back to Earth from the Soviet *Venera 9* spacecraft, which made a soft landing on the planet in 1975. **Earth (\#3)** Surface Temperature = 290 K Inclination = 23.45 degree Escape Velocity = 11.2 km/s Earth = **99.9%**: Differentiated Layers + **0.1%**: Atmosphere+Magnetosphere **Troposphere** The layer where the ***convection*** is the energy transport mechanism Hava olayları. As the elevation increases, ionization increases **Origin of Earth\'s Atmosphere** **Primary Atmosphere** Common to whole solar system H, He, methane, ammonia, water vapor **Secondary Atmosphere** Outgased from planet\'s interior (e.g volcanic activity) **Volcanic gases** are rich in water vapor, methane, CO2, SO2, compounds **UV radiation** from the Sun decomposes the lighter and H-rich gases allowing H to escape Temperature drops ➤ Water vapor condenses ➤ **oceans are created** **Types of Seismic Waves** **P-waves (pressure)** They can travel through both liquids and solids **S-waves (Shear)** They come shortly after P-waves The speed of the wave depend on the density of the matter They don\'t travel in straight lines The velocity varies with depth Earthquakes = P + S WAVES Mantle \~ 3000 km thick (density: 5000 km/m3) Crust \~ 15 km Core: Ni, Fe and some other lighter elements) It is liquid However pressure near the center forces the material into solid state (even T is high) **What heated the Earth\'s center?** Earth grew by capturing material from its surroundings This increased its gravitational field and therefore speed of material striking to surface increased Therefore generated heat made the Earth molten. Earth began to differentiate. As heavy material sank to the center; More gravitational energy released, ➤ which caused interior temperature to increase further. Bombardment continued: ➤ a thin layer of surface continue to be molten Heavy elements like Uranium, Thorium and Plutonium release energy as they decay (break up) into lighter elements. So, the Earth has been cooling for the past 4 billion years **Earth\'s Magnetosphere** It is discovered by artificial satellites in late 1950s It is created by the planet\'s magnetic field. The magnetic field lines runs from South to North and they intersect the Earth\'s surface vertically. The poles are roughly aligned with Earth\'s spin axis. **Van Allen Belts**  The magnetosphere contains **two doughnut-shape zones** of high energetic charged particles above the surface 1\. Located about 3 000 km - catching **heavier protons** 2\. Located about 20 000 km - catching mostly **electrons** They are named as belts because their efficiency are the highest at the equator The particles in the belts originated from the Sun and they are carried by the solar wind. Therefore, the belts creates an invisible shield to protect the planet surface from energetic charged particles. The particles that can escape from Van Allen belts penetrates into lower layers of the atmosphere. Particles collide with air molecules They fall back to their ground states Their energy re-emit in visible spectrum; named as **Aurora** mostly in higher latitude regions TIDES Sun\'s tidal influence is about **half of Moon\'s** tidal influence. **Earth\'s Rotation** Earth\'s spin is slowing due to tidal bulge offset Therefore the Moon is spiraling slowly away from the Earth by 4 cm / year **Rayleigh scattering** **Mars (\#4)** Two moons(?) : Phobos, Deimos Mars day = 24.6 hours (similar to Earth\'s) **There is no evidence of plate tectonics** **Valles Marineris =** Huge canyon which is created by crustal forces **Olympus Mons** **The largest volcano** in the solar system **Mars Atmosphere** The troposphere, which rises to an altitude of about 30 km in the daytime, occasionally contains clouds of **water ice** or, more frequently, **dust** during the planet wide dust storms that occur each year. But it mostly contains **carbon dioxide** and it is **very thin**. Above the troposphere lies the stratosphere. Note the absence of a higher temperature zone in the stratosphere, indicating the absence of an ozone layer. Both moons are probably **captured asteroids**. **07 Outer Planets** **Divided into two main configuration:** Jupiter and Saturn Uranus and Neptune Mainly: Similar layers as Terrastials However the content is purely Hydrogen Hydrogen changes state and becomes liquid and metallic in lower layers. Upper layers contain clouds of ammonia and their compounds All four Jovians shows similar atmospheric conditions When a ball of gas rotates it will deform its structure. The deformation makes the object **elongated**. Faster along equator, Slower on poles Fast rotation of gas ball is also the reason of having a high magnetic field: **Dynamo Effect** Since Jovians are gaseous, centers of the magnetic fields (with respect to magnetic poles) don\'t always coincide with the planet\'s core; mostly for Uranus and Neptune moons\-- Jupiter: **4** major - **79** in total Saturn: **7** major - **62** in total Uranus: **5** major - **27** in total Neptune: **1** major - **14** in total They are mostly frozen rock. Exceptions: Io (Jupiter) - Lava flow Titan (Saturn) - Atmosphere, Methane in Liquid form Triton (Neptune) -- Atmosphere **Jupiter (\#5)** The colored bands in Jupiter's atmosphere are associated with vertical convective motion. Upwelling warm gas results in zones of lighter color; The darker bands overlie regions of lower pressure where cooler gas sinks back down into the atmosphere. Atmosphere= Mostly molecular hydrogen and helium Small amounts of methane, ammonia, and water vapor **Great Red Spot** It has existed for at least 300 years, possibly much longer. Color and energy source still not understood. **Could Jupiter have been a star?** No; it is far too cool and too small for that. It would need to be about 80 times more massive to be even a very faint star. \*The density and temperature increase with depth, and the atmosphere gradually liquefies at a depth of a few thousand kilometers\* It has a faint ring Four major moons: Io, Europa, Ganymede = It is the largest moon in the solar system; larger than Pluto and Mercury, Callisto **Saturn (\#6)** **Density**: 700 kg/m3 (less than water!) Atmosphere is mostly molecular hydrogen, helium, methane, and ammonia Dragon storm (a giant thunderstorm located in Saturn\'s Southern hemisphere; his is similar to the extreme conditions on jupiter at the site of its Great Red Spot) It creates aurorae Why rings: Too close to planet for moon to form---tidal forces would tear it apart. **Moons** Many of them are water ice medium sized: **Mimas, Enceladus, Tethys, Dione, Rhea, Iapetus** One large: **Titan =** Larger than Mercury and roughly half the size of Earth. **Uranus (\#7)** Discovered in 1781 by Herschel Uranus's axial tilt is 98°, Therefore the planet experiences the most extreme seasons known in the solar system. Two \"summers\": warm seasons, around the times of the two equinoxes. Two "winters": cool seasons, at the solstices. **Neptune (\#8)** **Neptune's Dark Spot.** Similar in structure to Jupiter's Great Red Spot. The entire dark spot is roughly the size of planet Earth. Moons of Uranus and Neptune Miranda (Uranus) Triton (Neptune) = Lakes of frozen water, all indicative of past surface activity.