Introduction to Astronomy

• Astronomy is a true science rooted in repeatable observations and experiments.
• Astronomy creates precise predictions and utilizes well-established sciences.
• A light year is an astronomical distance, where 1 ly = 4.607x10^12 km (~6 trillion miles).
• The speed of light (c) is a universal physical constant.

Branches of Astronomy

• Astrobiology studies the advent and evolution of biological systems in the universe.
• Astrophysics deals with the physics of the universe.
• Cosmology studies the origin and evolution of the universe.
• Planetary Science studies planets within the Solar System.
• Observational astronomy is the practice of observing celestial objects.
• Photometry studies how bright celestial objects are.
• Spectrometry studies the spectra of astronomical objects.
• Astrometry studies the position of objects in the sky.

Historical Models of the Universe

• Ptolemy, a Greek astronomer (~100 A.D.), proposed an Earth-centered universe (Geocentric Theory).
• Ptolemy's incorrect theory accurately predicted planetary motion for 1500 years.
• Nicholas Copernicus, a Polish astronomer, proposed a Sun-centered universe (Heliocentric Theory).
• Tycho Brahe, a Danish astronomer, favored a modified version of Ptolemy's theory and recorded precise observations of planets and stars.
• Johannes Kepler defined the Laws of Planetary Motions.
• Planetary motion law 1: Planets revolve around the sun in elliptical orbits.
• Planetary motion law 2: Planets move faster when closer to the sun.
• Planetary motion law 3: A mathematical formula can determine a planet's distance from the sun.
• In 1609, Galileo Galilei used a telescope to observe space objects.
• Galileo discovered craters and mountains on Earth's moon, 4 Jupiter moons, sunspots, and Venus phases.
• In 1687, Isaac Newton showed that all objects in the universe attract each other through gravity.
• In 1924, Edwin Hubble proved that other galaxies existed beyond the Milky Way.

Cosmology

• Cosmology studies the origin and evolution of the universe, from the Big Bang.
• NASA defines it as the scientific study of the large-scale properties of the universe.
• The universe includes all space and everything within it, like stars and planets.
• Early 1900s: Scientists debated whether the Milky Way contained all galaxies or just a collection of stars.
• Edwin Hubble calculated the distance to a fuzzy nebulous object and determined it lay outside the Milky Way.
• Hubble used General Relativity to conclude the galaxy is expanding, not static.
• Stephen Hawking determined that the universe is not infinite but has a definite size.
• The Big Bang Theory was proposed by Abbe Georges Eduard Lemaitre (1894-1966).
• A Belgian astrophysicist and priest contradicted Einstein's static universe.
• All the universe came from a dense, hot, supermassive ball about 13.7 billion years ago, then a violent explosion occurred spreading matter in all directions.
• The Big Bang was an expansion of space, not an explosion.
• A quark is one type of particle that makes up matter.
• Quark Soup is the universe made up of protons, neutrons, electrons, anti-electrons, photons, and neutrinos.
• In the first 3 minutes of the universe, light elements were formed during the Big Bang.
• Nucleosynthesis is the production of chemical elements from simple nuclei.
• Deuterium is an isotope of hydrogen.
• Helium is a chemical element lighter than air.
• Lithium is a silver-white element and the lightest metal.
• After 400 million years after the Big Bang, the universe began to emerge from cosmic dark ages during the epoch of reionization.
• Dark energy speeds up the expansion of the universe.
• The universe is almost entirely ordinary atoms or "Baryonic matter".
• Atoms make up 4.6% of the universe.
• The universe is 75% hydrogen and 25% helium.
• A tiny fraction of heavy elements includes 23% dark matter and 72% dark energy.

Spiral Galaxies

• Key features include a rotating disk with spiral arms, a central bulge, disk, and halo.
• Spiral galaxy compostion: stars, gas, dust, and dark matter which are ideal for star formation.
• The Milky Way is a barred spiral galaxy (SBc type).
• Spiral arms are bright regions with young stars, shaped by density waves.
• The central bulge is a dense core with older stars, often hosting a supermassive black hole.
• The disk holds the most matter and the halo contains globular clusters and dark matter.
• Normal Spirals include Sa (tight arms, large bulge) to Sc (loose arms, small bulge).
• Barred Spirals include SBa to SBc (Milky Way type: faint bar, loose arms).
• After the Big Bang, gas clouds clump and flatten into a disk due to gas collapse.
• Bulge formation: A dense center collapses first, creating older core stars.
• As gas cools, thick and thin disks develop.
• Density waves trigger star formation along arms when spiral arms form.
• Evolution: Gas replenishment sustains star formation, mergers can transform spirals into ellipticals.
• The Triangulum Galaxy (M33) is 60,000 light-years across, 40 billion stars and the smallest in the Local Group.
• NGC 6872 is the largest known spiral galaxies at 522,000 light-years across which is 5x the Milky Way.
• Diameter measurement techniques: angular size, isophotal diameter (D25), and Petrosian magnitude.
• Distance measurement techniques: parallax, redshift, and cosmic distance ladder.
• Luminosity is calculated from brightness, distance, and standard candles.
• The Lin-Shu Density Wave Theory states that spiral arms are density waves where gas/stars pile up.
• Compressed gas triggers new stars.
• Gravitational pull prevents arms from winding too tight.
• Observations match hydrogen cloud patterns, young star regions, and dust lanes.

Elliptical Galaxies

• They appear smooth, nearly featureless, lacking spiral arms or a disk as the definition and appearance.
• Stars move in random orbits, creating a uniform brightness that fades outward.
• Ellipticals are labeled "E" in Hubble's Tuning Fork Diagram, from E0 (spherical) to E7 (elongated).
• The shape depends on the observer's viewpoint.
• Size ranges from giant ellipticals (e.g., M87, IC 1101) to dwarf ellipticals (e.g., M32, M110).
• They contain older, reddish Population II stars with little to no new star formation.
• Giant and dwarf ellipticals often host supermassive black holes at their centers.
• M87 Contains a massive black hole, known for its relativistic jet.
• M49 is of the brightest galaxies in the Virgo Cluster.
• NGC 4889 is located in the Coma Cluster, hosting a supermassive black hole.
• IC 1101 is the largest known galaxy, spanning approximately 4 million lightyears.
• A compact satellite galaxy of Andromeda is M32.
• M110 is a dwarf elliptical galaxy orbiting Andromeda.
• NGC 147 & NGC 185 are small elliptical galaxies near Andromeda.
• Galaxy mergers, gravitational collapse and galactic cannibalism are theories of formation.
• Colliding galaxies mix stars randomly into an elliptical shape through galaxy mergers.
• Massive gas clouds collapse into an elliptical form through gravitational collapse.
• Large ellipticals absorb smaller galaxies through galactic cannibalism.
• They are common in dense galaxy clusters.
• Elliptical galaxies help researchers understand galaxy evolution, black holes, and dark matter.

Lenticular Galaxies

• Lenticular galaxies (type S0) were classified by Edwin Hubble in 1936.
• They bridge spiral and elliptical galaxies, having a disk-like structure without spiral arms.
• The disk appears biconvex (lens-like), especially when tilted from our line of sight.
• The star population is mostly old, low-mass stars (red, yellow, and white dwarfs).
• Lack of gas and dust prevents new stars from forming.
• Environmental stripping and galaxy collisions are theories of formation.
• Gas and dust is stripped away when the galaxy moves through dense clusters through environmental stripping.
• Merging spiral galaxies lose gas, creating lenticular galaxies through galaxy collisions.
• The thin disk is flat, contains older stars, and emits most of the galaxy's light.
• The thick disk is more dispersed, older stars with random orbits.
• The bulge is a dense, central region with stars in radial orbits; often houses a supermassive black hole.
• Globular clusters are spherical groups of ancient stars, mainly around the bulge and halo.
• The halo is diffuse, surrounds the galaxy, contains dark matter and old, low-metal stars.
• Lenticular galaxy composition: mostly old, metal-poor (Population II) stars.
• Dark matter provides gravitational stability and is inferred from star movement.
• Minimal interstellar medium: Little to no gas or dust, preventing star formation.
• A supermassive black hole is common and influences nearby star motion.
• Disk rotation is similar to spiral galaxies, but smoother without spiral arms.
• Bulge motion: Stars move in random, elliptical orbits (like elliptical galaxies).
• External movement: Found in dense clusters, often showing signs of past mergers or interactions.

Irregular Galaxies

• By definition, galaxies with no clear shape or structure, unlike spiral or elliptical galaxies.
• Irregular galaxies are made of stars, gas, and dust, appearing chaotic.
• They make up about 25% of all galaxies.
• Irregular galaxies contain both old and young stars, including hot, massive O and B stars.
• Irregular galaxies have a mass of 100 million to 100 billion times the Sun's mass.
• They have a diameter of 3,000 to 30,000 light-years.
• The luminosity is 10 million to 2 billion times the Sun's brightness.
• Irr I has some structure, hints of spiral arms (e.g., Large Magellanic Cloud).
• Irr II is completely chaotic, no recognizable structure (e.g., NGC 4449).
• Collisions with other galaxies and primordial irregularity are theories of formation.
• Gravitational interactions distort structure in collisions with other galaxies.
• Primordial irregularity is formed from early clumps of gas and dark matter, and never developed a structured form.
• Remnants of larger galaxies - Leftover fragments from past galaxy collisions.
• The Large Magellanic Cloud (LMC) is ~160,000 light-years away, 14,000 light-years in diameter, 10 billion solar masses, rapid star formation (e.g., Tarantula Nebula).
• The Small Magellanic Cloud (SMC) is ~200,000 light-years away, 7,000 light-years in diameter, 7 billion solar masses, possibly split by gravitational interaction with the LMC.
• IC 10 is ~2 million light-years away, intense star formation.
• Canis Major Dwarf: Closest satellite galaxy to the Milky Way, ~25,000 light-years away, 1 billion solar masses.
• NGC 4449is ~12 million light-years away, formed from galaxy interactions, rich in gas and dust, and active star formation.
• NGC 1569 ~11 million light-years away, rapid star formation for 100 million years due to past interactions.

Galaxy Formation and Evolution

• Galaxies are vast systems of stars, gas, dust, and dark matter held together by gravity.
• Studying galaxies helps in understanding how matter evolved and structured the universe.
• According to the Big Bang Theory, the universe began as a hot, dense point ~13.7 billion years ago.
• Top-Down Formation (Monolithic Collapse) was proposed in the 1950s by Eggen, Lynden-Bell, and Sandage (ELS).
• Galaxy formed from one large, turbulent protogalactic cloud, flattening over time.
• Inconsistent with modern evidence, stars in the halo show a wide range of ages.
• Bottom-Up Formation: Smaller gas clouds and dwarf galaxies merged to form larger galaxies over time.
• It explains younger stars in the halo and ongoing galaxy growth.
• Star formation: Gas and dust condense under gravity to form stars, enriching galaxies with new elements.
• Stellar winds and supernovae return material to fuel new star formation.
• During collisions and mergers, galaxies can collide, compressing gas clouds and triggering starbursts.
• Mergers can create larger galaxies or irregular forms.
• Star formation slows as gas depletes or external factors cut off fresh material during galactic aging and death.
• Galaxies transition to "red and dead" states dominated by older stars.
• Preventive Feedback blocks the inflow of cold gas, limiting star formation.
• Ejective Feedback expels gas, halting future star formation.
• Galaxies shift from "blue cloud" (active, star-forming) to "red sequence" (inactive, older stars) as their final stage.

Stars

• Over half of all stars have one or more partners.
• Systems range from pairs to complex groups with up to 7 stars.
• Binary stars are two stars orbiting each other and can include large, hot stars with smaller, cooler ones.
• Some pairs create eclipses, helping scientists measure star properties.
• Neutron star pairs can collide, creating heavy elements like gold and platinum.
• One star collapses into a white dwarf, neutron star, or black hole, stealing material from its companion, producing X-rays through X-ray binaries.
• X-ray Binaries helps study extreme physics like neutron star pulses and thermonuclear blasts.
• Star systems can have 3 or more stars, like Alpha Centauri (3 stars, one with a planet).
• TYC 7037-89-1: a six-star system with three binary pairs in a complex orbit.
• Star clusters are groups of stars born from the same gas cloud, held by gravity for millions or billions of years.
• They form from collapsing gas and dust.
• Stars can stay, disperse, or get ejected during formation.
• Old, massive clusters with tens of thousands to millions of stars, packed densely (50-450 light-years across) describe Globular clusters.
• Globular clusters form 8-13 billion years ago, found in the outer regions of galaxies.
• The Milky Way has ~150 globular clusters, some orbiting in reverse, that suggests they were captured from other galaxies.
• Open Clusters are smaller, younger, loosely bound clusters with tens to thousands of stars.
• The core of open clusters spans a few light-years, surrounded by a corona stretching tens of light-years.
• They are found in the Milky Way's disk, often in spiral arms and less stable and will spread out over time.
• An example is the Eagle Nebula with the famous "Pillars of Creation," a star-forming region 5,700 light-years away.
• Loose groupings of stars that formed together but are weakly bound by gravity and disperse over time are Stellar associations.
• Stellar associations are found near star-forming regions, often in spiral arms.
• OB Associations are hot, massive O- and B-type stars (young, blue, bright).
• R Associations are medium-mass, bright stars (3–10 times the Sun's mass).
• T Associations are low-mass, young T Tauri stars.
• The Orion OB1 Association includes Orion's Belt stars.
• The Scorpius-Centaurus Association is the closest OB association to the Sun.
• Characteristics of open clusters: Loosely packed, young stars (few dozen to thousands).
• Can be found in the galactic disk, often near spiral arms.
• Open clusters are unstable stars and disperse over millions of years.
• Pleiades (M45), "Seven Sisters," is an easily visible open cluster.
• The Hyades are the closest open cluster to Earth (in Taurus).
• The Beehive Cluster (M44) is bright and located in Cancer.
• The Double Cluster is a striking pair in Perseus.
• Characteristics of globular clusters: Dense, ancient clusters with thousands to millions of stars.
• A Globular cluster is found in the galaxy's halo, stable, and long-lasting (8–13 billion years old).
• Omega Centauri: Largest and most massive globular cluster.
• Messier 13 (Hercules Cluster): Bright, favorite for astronomers.
• Messier 22: Large cluster in Sagittarius.
• NGC 6397: One of the closest globular clusters to Earth.
• Keywest erlund1: One of the Milky Way's most massive young clusters.
• R136: Dense cluster at the core of the Tarantula Nebula.

Stars Cont

• Super Star clusters are extremely dense and massive clusters, often in starburst galaxies.
• The characteristics of a super star cluster is millions of young, hot stars packed tightly being potential precursors to globular clusters.

• Population I stars are young, metal-rich stars in spiral arms (e.g., the Sun).
• Population II stars are older, metal-poor stars in the halo and globular clusters.
• Population III stars are hypothetical first-generation stars (pure hydrogen and helium) and never observed directly but are inferred from models.
• Star clusters and stellar populations are key to understanding the formation, evolution, and structure of galaxies.
• O: Very hot, blue (>30,000 K) is a Spectral Types (MK System)
• B: Hot, blue-white (10,000–30,000 K) is a Spectral Types (MK System)
• A: White (7,500–10,000 K)is a Spectral Types (MK System)
• F: Yellow-white (6,000–7,500 K) is a Spectral Types (MK System)
• G: Yellow, like the Sun (5,000–6,000 K) is a Spectral Types (MK System)
• K: Orange (3,500–5,000 K) is a Spectral Types (MK System)
• M: Red, coolest (2,000–3,500 K) is a Spectral Types (MK System)
• L, T, Y: Cool brown dwarfs (infrared emitters) are other types of stars.
• C: Carbon stars (red giants rich in carbon) are other types of stars.
• S: Stars with zirconium oxide in spectra.
• W (Wolf-Rayet): Hot stars with strong winds and emission lines
• Ia: Luminous supergiants is the Luminosity Classes.
• Ib: Less luminous supergiants is the Luminosity Classes.
• II: Bright giants is the Luminosity Classes.
• III: Giants is the Luminosity Classes.
• IV: Subgiants is the Luminosity Classes.
• V: Main-sequence (dwarfs) — like our Sun (e.g., G2V) is the Luminosity Classes.
• sd (VI): Subdwarfs (lower luminosity) is the Luminosity Classes.
• D (VII): White dwarfs
• Measuring Stars: Distance is determined by Parallax which Measures position shift of nearby stars.
• Distance is determined by Standard Candles that uses objects like Cepheid variables with known brightness.
• Distance is determined by Spectroscopic Parallax that Compares spectral type and brightness.
• Measuring Stars: Brightness is determined by Apparent Magnitude that measures Brightness from Earth.
• Brightness is determined by Absolute Magnitude the true brightness at 10 parsecs (32.6 light-years).
• Measuring stars size: Stellar Radius is Calculation using luminosity and temperature (Stefan-Boltzmann Law).
• Measuring stars size: Interferometry combines multiple telescopes for high-res imaging.
• Measuring Temperature is performed by Spectroscopy which analyzes light spectrum to determine surface temperature.
• Star Composition is performed by Spectral Analysis that identifies chemical elements from absorption lines.
• Star Mass is performed by Binary Systems which uses orbital motion (Kepler's laws) to calculate mass.
• Star Mass is performed by Stellar Models that estimates mass from luminosity, temperature, and age.
• The Morgan-Keenan system classifies stars by temperature (spectral type) and brightness (luminosity class).
• Measurements of distance, brightness, size, temperature, composition, and mass help astronomers understand stars' physical properties and evolution.
• Stars appear to move in circles due to Earth's rotation due to diurnal motion.
• Earth's orbit causes seasonal changes in visible stars by annual motion.
• Angular change in position is proper motion.
• Motion toward/away from Earth (measured via Doppler shift) is the radial velocity.
• Total 3D motion which combines proper motion and radial velocity is the Space Velocity.
• The nearest star is Proxima Centauri (4.24 light-years), a red dwarf with planet Proxima b in the habitable zone.
• The Farthest Star is Earendel (12.9 billion light-years away), discovered by gravitational lensing.
• The Brightest Star is Sirius (-1.46 magnitude), a white main-sequence star with a white dwarf companion.
• The Largest Star is UY Scuti, a red supergiant ~1,700 times the Sun's radius.
• The Most Massive Star is L_MC (Luminous Blue Variable), ~300 times the Sun's mass.
• The Hottest Star is Wolf-Rayet stars (e.g., WR 102), ~210,000 K surface temperature.
• The Coldest Star is WISE 1828+2650, a brown dwarf with ~250 K temperature.
• The Most Luminous Star is Eta Carinae, which shines ~5 million times brighter than the Sun.
• The Sun is a G-type main-sequence star, 4.6 billion years old, that fuels life on Earth.
• The life cycle of low-mass stars involves a red giant and then a white dwarf.
• The life cycle of high-mass stars involves a supernova, neutron star and/or a black hole.
• Alpha Centauri: Closest system (~4.37 light-years) with 3 stars: Alpha Centauri A, B, and Proxima Centauri.
• Orion Nebula: Star-forming region with young stars in various stages of development.
• Pleiades (Seven Sisters): Open star cluster ~444 light-years away and visible to the naked eye.
• Constellations are groups of stars that form recognizable patterns and are used for navigation and locating celestial objects.
• There are 88 official constellations recognized by the International Astronomical Union (IAU).
• Circumpolar constellations are visible all year round from certain latitudes.
• Circumpolar constellations never dip below the horizon at specific latitudes and are alwayss visible.
• Polaris appears to always rotate creating movement around the celestial poles..
• The number of circumpolar constellations you see depends on how far you are from the equator.
• Ursa Major: Contains the Big Dipper and deep-sky objects like Bode's Galaxy (M81) and the Pinwheel Galaxy (M101) and is best seen in April.
• Ursa Minor's home is Polaris, the North Star, making it key for navigation and it is best seen in June.
• Cassiopeia is known for its W shape and includes the Pacman Nebula (NGC 281) and is best seen in November.
• Cepheus resembles a house, contains Garnet Star (a red supergiant) and Elephant's Trunk Nebula (IC 1396) and is best seen in November.
• Draco is a large, winding dragon with Thuban (an ancient North Star) and the Cat's Eye Nebula (NGC 6543) and is best seen in July.
• Carina contains Canopus (2nd brightest star) and the Carina Nebula (NGC 3372) and is best seen in March.
• Crux : The famous Southern Cross, used for navigation, with the Jewel Box cluster (NGC 4755) and its best seen in May.
• Centaurus's home to Alpha Centauri (closest star system to Earth) and Omega Centauri (massive star cluster) and its best seen in May.
• Triangulum Australe: A small triangular constellation with the bright star Atria and is best seen in August.
• Circumpolar constellations are visible year-round making them reliable for navigation.
• The northern constellations are Ursa Major, Ursa Minor, Cassiopeia, Cepheus, and Draco.
• The southern constellations are Carina, Crux, Centaurus, and Triangulum Australe.

Life Cycle of Star

• A star is a luminous sphere of hot plasma that is mainly hydrogen and helium and held together by gravity.
• Stars form the building blocks of galaxies and undergo a life cycle lasting from millions to trillions of years.
• Nebula: A large cloud of gas and dust (mostly hydrogen and helium) where stars are born during the Stellar Nebula and Protostar Stage.
• Protostar: Formed when gravity pulls gas and dust together, creating a hot, dense core.
• Brown Dwarf: If the protostar doesn't gather enough mass (< 0.08 solar masses), it becomes a "failed star," emitting only faint infrared light without hydrogen fusion.
• Stars create Nuclear fusion (hydrogen to helium) powers the star, keeping it stable through hydrostatic equilibrium (balance between gravity and outward pressure) during the Main Sequence Stage.
• Low mass stars: Slow fusion which can last billions of years (e.g., the Sun).
• Massive stars: Fast fusion that can last millions of years.
• When hydrogen runs out, the core contracts, and outer layers expand during the Post Main Sequence Stage:
• Red Giant (e.g., Aldebaran): 0.3–8 solar masses, cooler, which fuses helium into carbon/oxygen.
• Red Supergiant (e.g., Betelgeuse): >8 solar masses, larger, which fuses heavier elements like silicon and iron.
• End Star results:
• Red Giants → Planetary nebula → White dwarf.
• Red Supergiants → Supernova → Neutron star or black hole.
• Average Star (e.g., Sun) ends by: Forming a planetary nebula, leaving behind a white dwarf that slowly cools eventually becoming a theoretical black dwarf.
• Massive Star (e.g., Betelgeuse) is the last stage:
• Core becomes iron → Collapses rapidly → Supernova explosion.
• Result: Neutron star (8–15 solar masses) or black hole (>15 solar masses)

Interstellar Medium (ISM)

• Matter between stars in a galaxy made of gas, dust, and cosmic rays.
• Primordial Gas is leftover hydrogen and helium from the galaxy's formation and is a star origin of ISM material.
• Stellar Winds are stars that shed gas and dust throughout their lifetimes.
• Supernova Explosions eject heavy elements and gas into space.

• Cool Clouds (H I Regions) temperature ~100 K, are dense, are shielded from UV radiation.
• Twisted chaotic shapes visible in infrared/radio wavelengths.
• Intercloud Medium temperature is ~8,000 K, low-density (~0.1 atoms/cm³), partially ionized by starlight UV photons, and maintains pressure balance with cooler clouds.
• Essential for star formation; giant molecular clouds (GMCs) hold up to 1 million solar masses.
• Dense, cold cloud made of mostly H2 and CO just above absolute zero are molecular clouds.
• Coronal Gas is extremely hot (1 million K+), has very low density, formed from supernova bubbles.
• Expanding bubbles can merge into superbubbles, triggering star formation and filling ~20% of interstellar space.
• (Our Sun is in the Local Bubble).
• Cool Clouds make up 20% of ISM Mass Distribution.
• Intercloud Medium makes up 50% of ISM Mass Distribution.
• Molecular Clouds make up 20% of ISM Mass Distribution.
• Coronal Gas makes up 10% of ISM Mass Distribution

Galaxies & Star Dust

• Stellar winds shed hydrogen, helium, carbon, and silicon, forming dust grains.
• Supernovae blasts hot gas and dust into space, contributing to coronal gas and shock waves.
• Gas and Dust from Aging Stars creates A molecular clouds that form under pressure (e.g., from supernova shock waves).
• Gravity pulls dense regions inward, creating star clusters.
• Massive Stars in clusters generate winds and supernovae, dispersing material back to the
• ISM.
• Some Star material becomes locked in remnants like white dwarfs, neutron stars, or black holes, through recycling.
• During chemical enrichment, hydrogen transforms into heavier elements (carbon, nitrogen, oxygen), shaping galaxy evolution.

The Sun

• The Sun is the center of our solar system, held together by its gravity.
• drives Earth's seasons, weather, and climate.
• The latin word for Sun: "sol" → "solar.".
• The Sun is a medium-sized star among billions in the Milky Way.
• It's has been on Earth for about halfway through its 10-billion-year life and will expand into a red giant, then shrink to a white dwarf..
• Its composition is 75% hydrogen, 24% helium, 1% other elements (iron, nickel, oxygen, etc.).
• Nuclear fusion in the core converts hydrogen into helium, releasing energy.
• The sun is energy outputs 3.8 × 1026 watts (600 million tons of hydrogen converted to helium per second).
• Sun Energy Forms: visible light, infrared (heat), ultraviolet (UV) radiation, X-rays and gamma rays, and solar wind (charged particles).
• Core: Energy production is throughput Fusion.
• Radiative Zone: Energy slowly moves outward via radiation.
• Convective Zone: Hot plasma rises, cools, and sinks which can cause sunspots and magnetic activity.
• Photosphere: Visible surface (~5,500°C) releaseslight and heat.
• Corona: an extremely hot outer atmosphere that releases (~2 million °C).
• Apparent sun Motion: Sun appears to move due to Earth's rotation and orbit (ecliptic path and causes seasons).
• Real Sun Motion can be described:
• Orbits Milky Way's center (~230 million years per orbit).
• Rotates on its axis (differential rotation) with 25 days at the equator and 36 days at the poles.
• Wobbles around the solar system's barycenter (center of mass) due to planets' gravitational pull.
• Sun's Magnetic Field & Solar Cycle: Magnetic poles flip every ~11 years (solar cycle).
• During the solar maximum there are increased sunspots, solar flares, and coronal mass ejections .
• Space weather: Affects satellites, GPS, power grids, and Earth's magnetosphere
• Heliosphere: Sun's magnetic bubble extending through the solar system

The Sun structute

1. core that is extremely dense 15 million Kelvin where nucleur fusion happens
2. The Radiative zones and moves energy ouward there electromagnetic rediation
3. The convective zone has Hot gas rises cools and sinks like a boiling pot.
4. This is the photosphere

• "Surface" of the Sun — where visible light escapes (5,500°C).

5. This thin Hotter layer above photosphere emits UV light.

• Thin, hotter layer above the photosphere, emits UV light.

6. The Corona

• outermost super hot 1 million kelvin visible during solar eclipses.

Sun features

• Sunspots are Cooler, dark patches caused by strong magnetic fields, they appear in cycles, lasting days to months. Solar flares
• massivergy bursts from tangled magnetic fields snapping can disrupt Earth's communications.
• is a Constant stream of charged particles flowing from the Sun, affecting space weather.
• also known as Filaments, are huge arcs of cooler dense gas held up by magnetic fields — can last days to months. The Solar Wind Basic Solar info Type: G2 V yellow dwarf star · Age: ~4.5 billion years · Distance from Earth: ~93 million miles (150 million km) · Diameter: ~865,000 miles (1.4 million km) · Mass: 99.8% of the solar system's total mass Energy Production (Nuclear Fusion) · Process: Proton-proton chain reaction (hydrogen fuses into helium) · Core temperature: ~15 million Kelvin

Quasars

• Definition: Quasar = "Quasi-stellar radio source" are extremely luminous and distant objects powered by supermassive black holes at galaxy centers.

• Can be a trillion times brighter than the Sun, helping study the early universe.

• Quasars were first Discovered in 1950s and First Detected as star-like radio sources with unusual spectra.

• In 1963 Maarten Schmidt identified 3C 273, revealing its high redshift and vast distance, confirming it as a new type of celestial object. Quasars Have a point-like structure that appears star-like despite immense distance -extreme Luminosity: Outshines entire galaxies due to energy from accretion

• It has a unique spectra emits radiation across multiple wavelengths with broad and narrow emission lines. Disks Quazar Location: Found at the centers of distant galaxies, powered by supermassive black holes consuming surrounding matter. Component contributing to quazar brightness: Supermassive black hole and the core engine that produces millions to billions of solar masses.

• spinning superheated gas that emits intense radiation is the accretion disk

• high-speed particle streams boosting brightness also know as blazars are pointed if towards earth do to Relativistic jets.

• High-speed outflows affecting galaxy evolution and black hole growth is known Quasar winds.

Notable Quasars

• -3C 273: First identified quasar (2.4 billion light-years away). • RX J1131: Gravitationally lensed quasar, providing detailed X-ray data (6 billion light-years). •J043947.08+163415.7: One of the brightest-known quasars — which shines like 600 trillion Suns. • H1821+643: Hosts a massive black hole (3-30 billion solar masses) in the constellation Draco.

Quazar Conclusion

Quasars are vital tools for studying black holes, galaxy evolution, and the early universe.

• Their extreme brightness makes them valuable "time machines" for exploring cosmic history.
• Future technology will likely uncover even more about these powerful objects. Neutron Star Introduction: Neutron stars are dense remnants of massive stars that collapse after a supernova.
• They pack the mass of a giant star into a sphere about 20 km wide.
• Predict predicteded by theory, their discovery took decades.
• Form when a star 8–20 times the Sun's mass runs out of fuel and explodes during neutron star creation.
• The core collapses, merging protons and electrons into neutrons.
• Outer layers are ejected, leaving an ultra-dense, neutron-packed core. the sides and Mass is about 10 to 20 km wide comparable to Manhattan size.
• A sugar cube size piece of neutron star material weighs about one trillion kg like 3000 to create Buildings. Gravity is so strong that requires half the speed of light.

Neutron Stats and structure

Atmosphere: Thin hydrogen, helium, and carbon layer at ~2 million °C.

• Outer crust: Ions and electrons.
• Inner crust: Electrons, neutrons, and atomic nuclei influenced by magnetic fields.
• Outer core: Superconducting protons allow electricity to flow without energy loss.