Intro to Astrology

Introduction to Astronomy

ASTR100 (section 1) Fall 2017 page 8 Midterm Exam 3 - Study Guide o Star Clusters: group of stars close in space  Globular clusters  Nearly symmetrical, contains thousands of stars, old, distant from sun  Open clusters  Loose, ranges in age, dozens-several hundreds, appear separated  Stellar associations  Loose groups of extremely young stars, low mas

ASTR | 100 | Introduction to Astronomy | ASTR100 (section 1) Fall 2017 

ASTR100 (section 1) Fall 2017 page 9 Midterm Exam 1 - Study Guide The final exam will cover material from the entire semester; it is comprehensive. This study guide lists only the topics since the previous midterm (except, all equations and constants are included here); the final exam will also cover the topics from the previous three midterm study guides . Y

Chromosphere - “sphere of color”- 2 nd of 3 layers. Where reddish color is released. Not easily seen-bright Corona -only seen on a complete solar eclipse. Rays that extend kilometers of the sun’s surface. Diﬀerenal Rotaon - sun rotates with diﬀerent angular velocies. Proves nonsolid objects. -sun spots Aurora- northern lights. Only seen in the north. Produced by solar wind charging parcles Coronal Loops - corona is bent due to a magnec ﬂux. Found with sunspots. Solar Prominence- Large bright gaseous feature extending outwards from the sun’s surface. Solar Flash- sudden ﬂash of brightness near sun’s surface. Plasma medium becomes very hot. Releases energy Coronal Mass Ejecon- CME-massive burst of gas and magnec ﬁeld arising from corona being in solar wind Sun’s Core- Innermost part of the sun that takes up 20-25% of the solar radius. Hoest layer 15.7 mil K energy is transferred through photons Sun’s Convecve Layer - Sun’s outer layer. Temp is lower than radiave zone. Opaque. Chromosphere vis Sun’s Radiave Zone- Regulated by thermal convecon- primary mean of energy transfer Convecon - the concerted, collecve movement of groups or aggregates of molecules within ﬂuids and rheids, through advecon or through diﬀusion or as a combinaon of both of them Parallax- the diﬀerence the apparent posion of an object viewed from 2 diﬀerent lines of sight Arcsecond- Used to measure angular distance from equator- 1/3600 th of a degree Luminosity -total amount of energy released by a star galaxy of other astro object- related to brightness Center of mass- of distribuon of mass in space is a unique point where if a force acts on the object it will move but not rotate. Spectral Class- gives a star’s ionizaon state. Gives photosphere’s temperature and density Kelvin- unit of measure of temperature that is absolute. 1K=-459.67 degrees Fahrenheit Thermal Radiaon - electromagnec radiaon generated by the thermal moon of charged parcles. Black Body- a body that absorbs all incident electromagnec radiaon. Major emier at all energy levels Red Supergiants- largest stars by volume, but not by mass. High luminosity class I. Spectral K or M Red Giants- yellow-orange to red. K or M spectral. Class S stars and most carbon stars White Dwarf - compact star that is no longer generang energy through nuclear fusion at its core HRD- scaer plot of stars showing the relaonship between their luminosity and spectral types. Neutrino- small electrically neutral parcle associated with dark maer. Nuclear Fusion- Nuclear reacon where two fast moving nuclei collide and form one nucleus. Powers Stars Nuclear Fission: Nuclear reacon where nucleus splits forming two smaller ones, Releases a lot of energy Black hole: If the mass is greater than about 3 M Sun , then we are likely seeing (a black hole—as long as we can make sure the object really is a collapsed star.  Explosion of supernova leaves blackhole Molecular cloud: nebulae: interstellar cloud of dust, hydrogen, helium and other ionized gases Hydrostac Equillibrium- when liquid is at rest, or velocity is constant over me. External forces balanced Brown Dwarfs- substellar objects not massive enough to sustain hydrogen reacons in their core. Protoplanetary Disk - rotang disk of dense gas surrounding a new, T tauri, or Herbig star Protoplanetary Oulow- two connuous oulows of gas from the poles a star^ T Tauri Stars- stars found near molecular clouds with strong chromospheric lines Red Dwarf- small relavely cool star on the main sequence. Most common type of star Sphageﬁcaon- stretching of objects into long thin shapes. Near black holes. Nothing can withstand Gravitaonal Redshiﬅing- electromagnec radiaon is reduced in frequency. Weaker gravity ﬁeld Solar System: 4.6 billion years old Spectral lines are important- every element has their own Granular appearance on sun is due to convecve moon under. Sunspot light is redder and dimmer Hydrogen fusing into helium to power sun Magnec ﬁelds cause sunspots Corona =outer atmosphere Density of neutron star=atomic nucleus Colder temps help star formaon core collapse is due to fusion leaving iron blackholes are produced by supernovae of massive stars event horizon -nothing can escape white dwarf same size as earth pulsar - rapidly rotang neutron star gold is produced through supernova of high mass stars **ALL planets orbit counterclockwise around the Sun parcular star in a binary star system orbits the other in an ellipcal orbit with a semimajor axis of 3 AU and a period of 5 years. What is the sum of the masses of the two stars in the system? Kepler's Third Law (modiﬁed by Newton) is given below. P^2= a^3/ M1+M

ASTR | 100 | Intro to Astrology | study guides | Chromosphere - “sphere of colo

Astronomy : the study of the objects that lie beyond our planet Earth and the processes by which these objects interact with one another. AU (astronomical unit): average Earth-sun distance. Planet: a body of significant size that orbits a star and does not produce its own light (AKA: wanderer) -it takes Earth 1 year to go around the sun -Diurnal motion (daily motion) of the sky is from the Earth rotation. -a solar system consists of planets and other objects orbiting around a star, whereas a galaxy is a system consisting of an immense # of stars -an object orbiting the Sun in an ellipse can be said to be always accelerating -retrograde motion: apparent change in the movement of the planet through the sky (east to west) -prograde motion: planet moves west to east relative to the stars (line from earth to object rotates counterclockwise) The seasons -Seasons are caused by the tilt of Earth’s axis (23.5) -seasons on the southern half of the hemisphere are opposite of northern -difference between seasons gets more pronounced the farther north or south we travel from equator -Earth is CLOSEST to the sun JANUARY -sun: 2 effects making it warmer for earth: angle of sunlight, and length of time the Sun spends above the horizon -near the equator, all seasons are the same (12 hrs day 12 hrs night) - The Sun is north of the celestial equator from about March 21 to September 21, so at the North Pole, the Sun rises when it reaches the vernal equinox and sets when it reaches the autumnal equinox.  -sun rises in East and sets in West due to Earth’s rotation -in summer, sun is higher in the sky, in the winter sun is lower -solstices occur when sun is as max north/south of equator. Equinoxes occur when sun crosses celestial equator -sun is never directly overhead at noon at mid-northern latitudes Constellations -random projected patterns of stars on which we have defined patterns that differ from culture to culture (88). *every star is located in a constellation -If a star is 100 light-years away, the light we see from it tonight left that star 100 years ago and is just now arriving in our neighborhood. - Ecliptic : the great circle that is the apparent path of the Sun among the constellations in the course of a year -star trails: circles. Stars appear to move East to west about celestial poles (counterclockwise when looking North) -Earth’s orbit causes seasonal migration of stars -paths that stars make depend on an observer’s latitude (increase w latitude) Moon -rotates once per orbit; same face toward Earth at all times -Moon’s sidereal period (the period of its orbit about Earth measured with respect to the stars) is a little over 27 days -moon rotates on its axis the same amount of time it takes to rotate around Earth -differential forces tend to stretch Earth slightly into a prolate spheroid (a football shape), with its long diameter pointed toward the Moon. -quarter moon most easily seen during daytime -TIMELINE: day 1 new moon; day 4 waxing crescent; day 7 first quarter; day 10 waxing gibbous; day 14 full moon; day 18 waning gibbous; day 22 third quarter; day 26 waning crescent; day 28 (1) Tides -Water on the side of Earth facing the Moon flows toward it, with the greatest depths roughly at the point below the Moon.  On the side of Earth opposite the Moon, water also flows to produce a tidal bulge -tides result from actual flow of water over Earth’s surface toward the two regions below and opposite the Moon, causing the water to pile up to greater depths at those places and removing water from the other sides. -spring tide: 'springing forth' of the tide during new and full moon. Neap tide: (7 days after spring tide): period of moderate tides when the sun/moon are at right angles to each other Eclipses lunar eclipse : FULL MOON. Earth passes between the Moon and the Sun, and the Earth's shadow obscures the moon or a portion of it. The plane of the Moon’s orbit is at an angle to the plane of Earth’s orbit. solar eclipse : NEW MOON. Moon passes between the Earth and the Sun, blocking all or a portion of the Sun (moon casts shadow on earth) -umbra: region of total shadow, penumbra: partial shadow. Umbra: completely blocked, penumbra: partial blockage -can see more total eclipses of the Moon than sun because total lunar eclipse is visible over a larger part of Earth -region of Earth for Sun to pass through Zenith?? Within +/- 23.5 degrees of equator (tropics) Ptolemy system geocentric cosmology; starts by assuming that the  Earth   is stationary; at the center of the universe.   Eccentric motion (deviating from circular path; elliptical). Each planet orbits around a small circle (epicycle) Each epicycle orbits on a larger circle (deferent) This system is not centered exactly on Earth but on an offset point (equant) The Greeks needed all this complexity to explain the actual motions in the sky because they believed that Earth was stationary and that all sky motions had to be circular. Copernicus -sun centered (heliocentric). Earth rotates on axis, revolves around the sun (circular motion assumed). See apparent retrograde motion when we pass an outer planet Galileo

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