Significance Problems in Understanding Astronomy Problems

Home , Satellite galaxy

Astronomy 1. Introduction and An excellent book Observations on astronomy by Timothy Ferris 2. Sun and Solar System (1988, 2003)

Also, there are two 3. Stars (Stellar Evolution) excellent periodicals related to astronomy – Astronomy and 4. Galaxies Sky and Telescope

5. Universe (Deep Space, Expanding Universe, Hubble Red Shift, Cosmology)

1. Scale of the Universe Astronomy – Significance Earth orbit 300 million km (diameter) 1. Earth’s position in the solar system and Universe ~1 billion km (orbital path) 2. Origin of the Universe Solar System 12 billion km across -3 3. Natural interest in observing the night sky (~ 10 light years*) Nearest Star 4.27 light years Milky Way Galaxy 105 light years Problems in understanding astronomy Local Group of Galaxies 2. 5 million light years concepts: Observable Universe 13.3 billion light years 1. Scale (distance and time) * One light year ~1013 km, or ~10 trillion km (It takes about 1/1000 of a year, or about 9 hours for light to travel across the solar 2. Frame of reference (changing and 3-D) system; 4.27 years for light from the nearest star to reach Earth; 3. Vast distance and time (large numbers and 434 years for light from Polaris (the North star) to reach Earth; unfamiliar units/terminology) ~100,00 years for light from the most distant stars in the Milky Way, our galaxy, to reach Earth, and ~13.3 billion years for light from the most distant galaxies in the universe to reach Earth!)

http://hubblesite.org/newscenter/archive/releases/2004/07/ (~60 MB jpeg file; deep space photograph, all of the bright Light Year – A unit of distance - “how far light dots or images are distant galaxies) travels in one year” Calculate a light year (you could do this calculation!): ~300,000 km/s  the “speed of light” (start here, x60 s/min note units) ~18,000,000 km/min  note that units cancel/change x60 min/hr at each calculation ~1, 080, 000, 000 k/hkm/hr x24 hr/day ~25,920,000,000 km/day x365 days/yr ~9,460,800,000,000 km/yr  speed of light in km/yr) ~9,460,800,000,000 km  One light year (units = km) So, one light year is approximately 10,000,000,000,000 km, or,… 1013 km or,… 10 trillion km

1 Close-up of area in lower right corner of previous slide – Hubble Space Telescope (HST) these are all galaxies Ultra Deep Field Image (2003-04)  Can image 30th magnitude objects.  Required 400 orbits, 11.3 days or recording.  Image contains about 10,000 galaxies.  Area covers 1/12.7 million of the entire sky.  Like looking through an 2 ½ m (8 ft) long soda straw. With this view, astronomers would need about 50 Ultra Deep Fields to cover the entire Moon.  Hubble's keen vision (0.085 arc seconds) is equivalent to standing at the U.S. Capitol and seeing the date on a quarter 400 m (1/4 mile) away at the Washington monument.

http://news.discovery.com/space/zooms/oldest-galaxy-universe-hubble-110126.html http://news.discovery.com/space/zooms/oldest-galaxy-universe-hubble-110126.html 2011 Deep space image (after repair/upgrade of Hubble Close-up of upper left of previous slide Space Telescope (HST)

9 10

2. Frame of Reference – 3D and constantly changing (due to Earth’s rotation and seasons caused by tilt of axis of rotation) North star (Polaris)

Meteor

Stars in Milky Way (spiral) galaxy (left) and in an elliptical galaxy (right) which contains large numbers of red dwarf Time lapse photo stars. USAToday, December 2, 2010 http://antwrp.gsfc.nasa.gov/apod/ap991006.html

2 North star (Polaris)

Time lapse photo centered on Polaris (~ 8 hours) Time lapse photo

http://en.wikipedia.org/wiki/North_Star http://www.opencourse.info/astronomy/introduction/02.motion_stars_sun/northpole_malin.html

The Universe's Most Ancient Object The farthest and one of the very earliest galaxies ever seen in the universe appears as a faint red blob in this ultra-deep–field exposure taken with NASA's Hubble Space Telescope. This is the deepest infrared image taken of the universe. Based on the object's color, astronomers believe it is 13.2 billion light-years away.

The most distant objects in the universe appear extremely red because their light is stretched to longer, redder wavelengths by the expansion of the universe. This object is at an extremely faint magnitude of 29, which is 500 million times fainter that the faintest stars seen by the human eye.

The dim object is a compact galaxy of blue stars that existed 480 million years after the Big Bang, only four percent of the universe's current age. It is tiny and considered a building block of today's giant galaxies. Over one hundred such mini-galaxies would be needed to make up our Milky Way galaxy.

The Hubble Ultra Deep Field infrared exposures were taken in 2009 and 2010, and required a total of 111 orbits or 8 days of observing. The new Wide Field Camera 3 has the sharpness and near-infrared light sensitivity that matches the Advanced Camera for Surveys' optical images and allows for such a faint object to be selected from the thousands of other galaxies in the incredibly deep images of the Hubble Ultra Deep Field. OBSERVING Credit: NASA, ESA, G. Illingworth (University of California, Santa Cruz), R. Bouwens YEAR Looking Back in Time (after the Big Bang)  (University of California, Santa Cruz and Leiden University), and the HUDF09 Team 15 16

3. Vast Distances and Large Numbers… 3. Units of distance in astronomy: Number of stars in the universe (just recently km - not usually used except within the solar updated), in at least 3 trillion galaxies: system. 300 sextillion A.U. - Astronomical Units, equals distance from the Earth to the Sun, about 150 million km. (300 x 1021 or,… 3 trillion times 100 billion) Parsec angle - used when distances are dtdetermi ned dbth by the parall ax meth thdod; a parall ax 106 1,000,000 Million angle of 1 second of arc (1/3600 degrees angle) 109 1,000,000,000 Billion corresponds to a distance of 3.09 x 1013 km and 1012 1,000,000,000,000 Trillion is called one Parsec. Distant stars are 1015 1,000,000,000,000,000 Quadrillion measured in MegaParsecs (106 Parsecs). 1018 1,000,000,000,000,000,000 Quintillion Light Year - distance that light travels in one 1021 1,000,000,000,000,000,000,000 Sextillion year, ~9.5 trillion km, usually used for distance to galaxies and size of the known universe.

3 Names of Stars View from Earth 3. Vast 3. Vast

 Distances Distances and frame View from  and frame of of Earth Pointer Stars reference reference To North Star  Distant star Names of Stars

All of the objects that  Distant stars we see with the naked eye in the night sky are  Closer stars within the Milky Way We view the stars in the galaxy (can see two sky as if they were all equal other galaxies with distance from Earth (as on excellent viewing or Ursa Major (the big bear, a flat or spherical surface). binoculars and many Closer stars  Sun and or the big dipper, However, the distance to Earth galaxies with a The constellation Vega, perspective view) stars varies greatly. telescope) perspective view.

The Solar System Jupiter and the Galilean Moons as viewed through a Moons modern amateur telescope (25 cm Meade). Callisto

Jupiter Jupiter Europa Galileo Galilei Galileo’s observations of Jupiter’s Io moons demonstrated that moons Ganymede revolved (orbited) about a planet providing support for the Copernican theory that the Sun was the center of the solar system. http://en.wikipedia.org/wiki/Moons_of_Jupiter

Kepler’s 3rd law: Ganymede P2 ~ D3 Jupiter Period squared is proportional to Diameter cubed. The exact equation can be used to calculate the mass of a Period planet: (days)

Io Europa Ganymede Callisto Nights Diameter Jupiter has at least 63 moons. The largest (and mostly closest to the planet) were discovered by Galileo in 1610 and  (km) Johannes are called the Galilean moons Kepler

http://en.wikipedia.org/wiki/Moons_of_Jupiter http://kepler.nasa.gov/files/mws/OrbitsOfJupitersMoons.pdf

4 Close-up of Galilean Moons positions relative to Jupiter on the date and time shown (C = Callisto, E = Europa, I = Io, G = Ganymede). With the calculator (below) you can step through time (use 10 minute or 1 hour time steps) to see the orbits of the moons about Jupiter (viewed from Earth, approximately along the plane of the ecliptic.

Sky and Telescope javascript Jupiter’s moons orbit calculator: Sky and Telescope javascript Jupiter’s moons orbit calculator: http://www.skyandtelescope.com/wp-content/observing- http://www.skyandtelescope.com/wp-content/observing- tools/jupiter_moons/jupiter.html# tools/jupiter_moons/jupiter.html#

Moon rotating (animation from multiple images from the NASA LRO (Lunar Reconnaissance Orbiter): http://www.youtube.com/watch?v=sNUNB6CMnE8. The moon does rotate about once every 27 days so that we always see the same “side” of the Moon from Earth. The rotation rate is caused by gravitational “locking” of the Moon to the Earth. It tool 4 years of observations Here’s our view of the Moon. The Moon as it appears from Earth to gather the images for the animation. (northern hemisphere): http://en.wikipedia.org/wiki/Moon

The Solar System (Sun and planets not to scale; Figure 15.17, text) Orrery

Solar system model (Orrery, named after Boyle, Charles, fourthAn excellent earl of Orrery online (1674–1731 Orrery (for) viewing– note that the it planets is not at intrue orbit) scalecan be in founddistances at: http://gunn.co.nz/AstroTouror diameters! - main controls are speed, orbit brightness, planet size and zoom. (also: Orbits to scale http://www.pbs.org/wgbh/nova/space/tour-solar-system.html) 30

5 A Brief Tour of the Solar System Orrery

An excellent online Orrery (for viewing the planets in orbit) can be found at: http://www.gunn.co.nz/astrotour/ The Sun and planets drawn to scale (orbital ?data=tours/retrograde.xml - main controls are speed, orbit brightness, planet size and zoom. (also: positions not to scale) Figure 15.18, text) http://www.pbs.org/wgbh/nova/space/tour-solar-system.html) 31

Another view of the Solar System The terrestrial planets

The Sun and planets, diameters drawn to scale. Orbital The Sun and planets drawn to scale (orbital position not to position not to scale. (http://en.wikipedia.org/wiki/Planet). 33 scale) (http://en.wikipedia.org/wiki/Planet). 34

Sunspot (and The gas giant planets (Jovian planets) image of Earth for scale). Note sunspots “Today [May 19, 2016], sunspot AR2546 is directly facing EthJPEarth. J.P. Brahic photographed the behemoth active region from his backyard observatory on The Sun and planets drawn to scale (orbital position not to Uzès, France.” scale) (http://en.wikipedia.org/wiki/Planet). 35 ttp://spaceweathergallery.com/indiv_upload.php?upload_id=125887

6 Earth’s Moon (Figure 15.23, text) Figure 15.19, text

Mars (Figures 15.29 and 15.30, text)

Olympus Mons (and outline of Arizona for scale) Jupiter (and great red spot) (Figure 15.33, text)

Saturn (and rings) (Image from Hubble Space telescope; Figure 15.36, text) “On July 19, 2013, in an event celebrated the world over, NASA's Cassini spacecraft slipped into Saturn's shadow and turned to image the planet, seven of its moons, its inner rings -- and, in the background, our home planet, Earth.” (http://www.nasa.gov/ mission_pages/cassini/whycassini/jpl/cassini20131112.html#.UoTHPD8wLpf)

7 Moon

Zoom in to see Earth and Moon

Neptune (and great dark spot) (Figure 15.40, text)

Comet (dust and ion tail) orbiting the Sun (Figure 15.43, text) Asteroid Eros (Figure 15.42, text)

Planets and Solar System Websites Viewing the Night Sky Observing Stars – Apparent Magnitude (brightness; what we see without adjusting for distance to the star) and Absolute Magnitude (brightness adjusted for distance). The Sun has a brightness (apparent magnitude of -27; note that smaller magnitudes are brightest). http://www.nasa.gov/worldbook/planet_worldbook_update.html Faintest stars: Apparent Magnitude* http://en.wikipedia.org/wiki/Planet Naked Eye viewing 6 http://pds.jpl.nasa.gov/planets/ Binoculars 10 http://www.space.com/planets/ Amateur Telescopes 15 http://science.nationalgeographic.com/science/space/solar-system Modern Large Telescopes >25 http://www.buzzfeed.com/daves4/the-universe-is-scary Hubble Space Telescope 31 47 * Larger numbers are dimmer stars

8 Difference of Difference of a a factor of 2 in factor of 10,000 magnitude in brightness

The star magnitude scale is logarithmic

Measuring Distance to Stars: 1. The Stellar Parallax method

Example of lunar parallax: Occultation of Pleiades by the Moon This is the method referred to by Jules Verne in From the Earth to the Moon:

Another method is to take two pictures of the Moon at exactly the same time from two locations on Earth and (Figure 16.2, text) compare the positions of the Moon relative to the stars. Using the orientation of the Earth, those two position measurements, and the distance between the two locations Stellar Parallax – distance determined from parallax angle, the on the Earth, the distance to the Moon can be triangulated: smaller the parallax angle the greater the distance to the star. A parallax angle of 1 second of arc (1/3600 degrees angle) This is the method referred to by Jules Verne in From 13 corresponds to a distance of 3.09 x 10 km and is called one the Earth to the Moon. Parsec. Distant stars are measured in MegaParsecs. http://en.wikipedia.org/wiki/File:Stellarparallax2.svg

Measuring Distance to Stars: 1. The Stellar Parallax method Measuring Distance to Stars: 2. Brightness method

(Figure 16.2, text) Light spreads out with distance such that the 2 Stellar Parallax – Animation available at: brightness varies by 1/r , where r is the http://www.astro.ubc.ca/~scharein/a311/Sim.html distance. For example in the diagram above, the brightness at 4 m distance would be only 1/16th of the brightness at 1 m.

9 Measuring Distance to Stars: 2. Brightness method Measuring Distance to Stars: 2. Brightness method

   

Brightness Demo…  Absolute Brightness = 1,  Absolute Brightness = 4 Brightness Demo…  Absolute Brightness = 1,  Absolute Brightness = 4 Observer Distant Stars  o Observer Distant Stars  o

Example 1 Star A Star B Example 2 Star C Star D

  Star B is twice as far as A   Star D is twice as far as C 

The apparent brightness of A and B will be the same The apparent brightness of C will be 16 times as great D

Empirical relationship (determined by observations of stars having a Measuring Distance to Stars: 3. Brightness method known distance) between period of pulsation for variable stars and Variable Stars – Certain stars that have used up their main luminosity. Absolute magnitude for a star whose distance is unknown can be calculated from the determined luminosity and then the distance supply of hydrogen fuel are unstable and pulsate. RR Lyrae to the star calculated from the brightness method using the absolute variables have periods of about a day. Their brightness doubles and apparent magnitude and 1/r2 relationship. from dimest to brightest. Cepheid variables have longer periods, from one day up to about 50 days. Their brightness also doubles from dimest to brightest. Period ~3 days Period ~3 days Measure the indicates a period of the luminosity variable star, then (proportional to … see next slide absolute magnitude) of about 500.

http://zebu.uoregon.edu/~soper/MilkyWay/cepheid.html

American astronomer Henrietta Leavitt observed many Cepheid The Sun – A Typical Star variables in the Small Magellanic Cloud (a satellite galaxy to ours). She found the period-luminosity relation (below; reported in 1912). (http://zebu.uoregon.edu/~soper/MilkyWay/cepheid.html )

Period ~3 days indicates a luminosity (proportional to Main composition of the Sun Spectacular loops and absolute prominences are often visible on magnitude) of Hydrogen 73.46% the Sun's limb. about 500. Helium 24.85% Oxygen 0.77% Carbon 0.29% Iron 0.16% http://nineplanets.org/sol.html

10 The sun is one of over 300 billion stars in the Milky Way Galaxy. It is about 25,000 Comprising about 99.8632% of the total mass of the Solar System – light-years from the center of the galaxy, most of the remainder is Jupiter. and it revolves around the galactic center once about every 250 million years. The sun is a star with a diameter of approximately 1,390,000 km, about 109 times the diameter of Earth. The largest stars have a diameter about 1,000 times that of the sun .

Fewer than 5 percent of the stars in the Milky Way are brighter or more massive than the sun. But some stars are more than 100,000 times as bright as the sun, and some have as much as 100 times the sun's mass. At the other extreme, some stars are less than 1/10,000 as bright as the sun, and a star can have as little as 7% of the sun's mass. There are hotter stars, which are much bluer than the sun; and cooler stars, which are much redder. http://www.nasa.gov/worldbook/sun_worldbook.html http://en.wikipedia.org/wiki/Sun

Adapted from: http://missionscience.nasa.gov/sun/MysteriesOfTheSun_Book.pdf The Convection Zone The Corona Energy continues to move toward The ionized elements within the the surface through convection corona glow in the x-ray and currents of heated and cooled extreme ultraviolet wavelengths. gas in the convection zone. NASA instruments can image the Sun’s corona at these higher energies since the photosphere is quite dim in these wavelengths.

Radiative Zone ~2 million K Photosphere Core ~5800 K ~15 million K

The Radiative Zone Sun’s Core Energy moves slowly outward – taking more than 170,000 years to Energy is generated by radiate through the layer of the thermonuclear reactions (fusion) Sun and planets – diameters shown to same scale Sun known as the radiative zone. creating extreme temperatures deep within the Sun’s core. (http://nineplanets.org/sol.html) 64

Adapted from: http://missionscience.nasa.gov/sun/MysteriesOfTheSun_Book.pdf The Convection Zone The Corona Energy continues to move toward The ionized elements within the Nuclear Fusion in the Sun the surface through convection corona glow in the x-ray and (and other stars) – the currents of heated and cooled extreme ultraviolet wavelengths. gas in the convection zone. NASA instruments can image the proton-proton chain reaction: Sun’s corona at these higher energies since the photosphere is quite dim in these wavelengths. Note that the process starts with 4 protons and ends with one atom of helium-4 (4 Most Important! Radiative protons are fused into one Zone ~2 Sun’s Core helium-4 atom) plus large million K EnergyPhotosphere is generated energy release – the gamma Core ~5800 K particles that eventually ~15 million K by thermonuclear reactions (fusion, see convert to photons (electromagnetic radiation, or The Radiative Zone next slides) creating o Energy moves slowly outward – K is Kelvin (= C+ extreme temperatures light). taking more than 170,000 years to 273.15), sometimes deep within the Sun’s radiate through the layer of the listed incorrectly as Sun known as the radiative zone. “degrees Kelvin” core. 65 http://en.wikipedia.org/wiki/Nuclear_fusion

11 Nuclear Fusion in the Sun Nuclear Fusion in the Sun (and other stars) – the (and other stars) – the proton- proton-proton chain reaction: proton chain reaction: The decrease in mass (from The proton–proton chain 4 protons to 2 protons and 2 reaction occurs around neutrons) is only 0.7% but 9.2×1037 times each second in the energy release is large the core of the Sun. The Sun because of the equation releases energy at the mass- e=mc2. energy conversion rate of Also note that at the end of 4.26 million metric tons per 26 the reaction, there are still second, (3.846×10 W) or 10 two protons remaining, 9.192 × 10 megatons of TNT so the reaction continues as per second. (http://en.wikipedia.org/wiki/Sun) a chain reaction always releasing energy. http://en.wikipedia.org/wiki/Nuclear_fusion http://en.wikipedia.org/wiki/Nuclear_fusion

Nuclear Fusion in the Sun (and other stars) – the proton-proton chain reaction:

Reaction continues until the The “holes” (absorption bands) in the spectrum are Hydrogen (source of the due to absorption by compounds in the atmosphere protons) is nearly all converted to Helium. Energy from nuclear fusion in stars larger than the Sun (hotter and higher pressure core) is generated by the Carbon-Nitrogen-Oxygen (CNO), or other, chain reactions. http://en.wikipedia.org/wiki/Nuclear_fusion http://en.wikipedia.org/wiki/File:Solar_Spectrum.png

Sunspots are Life Cycle of the Sun temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They are caused by intense magnetic activity, In about another 5 billion years, the hydrogen will be nearly which inhibits depleted and the Sun’s core will collapse and heat up resulting convection, in helium fusion and the Sun will become a Red Giant with a forming areas of size that will probably extend out to the present orbit of Mars. reduced surface temperature. http://en.wikipedia.org/wiki/Sun http://en.wikipedia.org/wiki/Sunspot

12 Note 11 year cycle of sunspots http://en.wikipedia.org/wiki/Sun http://en.wikipedia.org/wiki/Sunspot

Galaxies – Typically consist of 1 billion to over 100 billion stars. Most are relatively flat. Stars in the galaxy revolve around a central area, and thus don’t collapse (at least not quickly) from gravity (similar to the solar system). Most galaxies (including the Milky Way) probably have black holes in the center of the galaxy accounting for a substantial part of its mass.

Types of Galaxies: Elliptical, Spiral, Irregular, Dwarf

A tour of some galaxies… Very bright stars have more shorter-wavelength radiation and higher temperatures. These measurements are from spectrometers. http://csep10.phys.utk.edu/astr162/lect/sun/spectrum.html

Spiral Galaxy M81 (NASA)

(Chapter 16, text)

Above: The Milky Wayy(p (panorama from Earth).

Right: Spiral galaxy NGC 2997 (similar to Milky Way).

(Chapter 16, text)

13 Spiral Galaxy Andromeda (Figure 16.17, text)

Panoramic Photo (seven frames stitched together; time lapse exposure; a quarter Moon provided the light to illuminate the mesas and foreground) of the Milky Way galaxy above Monument Valley, AZ (from Dec./Jan. 2012 issue of National Wildlife, www.nwf.org; http://www.nwf.org/News-and-Magazines/National- Wildlife/PhotoZone/Archives/2011/2011-National-Wildlife-Photo- (Figure 16.2, text) Contest-Winners.aspx) (Figure 16.19, text)

Stellar Evolution, Galaxies, and the Universe The Barred spiral galaxy The Sun – A Typical Star Spectacular loops and The mass of the Sun is large prominences are often enough to cause high visible on the Sun's limb. pressure and temperature Hydrogen is being in the core, converted to Helium resulting in the Sun. There in nuclear is a large amount of fusion! HdHydrogen rema iiining, so the Sun will exist for a long time.

Main composition It is important to know about the Sun! Not of the Sun: only is it the center of our solar system, it is (Figure 16.16, text) Hydrogen 73.46% also an important source of energy for the Helium 24.85% Earth, and the closest star that we can study Oxygen 0.77% to better understand stars, galaxies and the Carbon 0.29% universe! Iron 0.16% Adapted from: http://nineplanets.org/sol.html

The sun is one of over 100 billion stars in the Milky Way Galaxy. It is about 25,000 Comprising about 99.8632% of the total mass of the Solar System – light-years from the center of the galaxy, most of the remainder is Jupiter. and it revolves around the galactic center once about every 250 million years. The sun is a star with a diameter of approximately 1,390,000 km, about 109 times the diameter of Earth. The largest stars have a diameter about 1,000 times that of the sun .

14 Sun and planets (enlarged) – diameters shown at same scale (Adapted from: http://nineplanets.org/sol.html) )

Adapted from: http://nineplanets.org/sol.html 85 86

Adapted from: http://missionscience.nasa.gov/sun/MysteriesOfTheSun_Book.pdf Adapted from: http://missionscience.nasa.gov/sun/MysteriesOfTheSun_Book.pdf The Convection Zone The Corona The Convection Zone The Corona Energy continues to move toward The ionized elements within the Energy continues to move toward The ionized elements within the the surface through convection corona glow in the x-ray and the surface through convection corona glow in the x-ray and currents of heated and cooled extreme ultraviolet wavelengths. currents of heated and cooled extreme ultraviolet wavelengths. gas in the convection zone. NASA instruments can image the gas in the convection zone. NASA instruments can image the Sun’s corona at these higher Sun’s corona at these higher energies since the photosphere is energies since the photosphere is quite dim in these wavelengths. quite dim in these wavelengths.

Most Important! Radiative Radiative Zone ~2 Zone ~2 Sun’s Core million K Photosphere million K EnergyPhotosphere is generated Core ~5800 K Core ~5800 K ~15 million K ~15 million K by thermonuclear reactions (fusion, see

The Radiative Zone The Radiative Zone next slides) creating o Sun’s Core o Energy moves slowly outward – K is Kelvin (= C+ Energy moves slowly outward – K is Kelvin (= C+ extreme temperatures taking more than 170,000 years to 273.15), sometimes Energy is generated by taking more than 170,000 years to 273.15), sometimes thermonuclear reactions (fusion) deep within the Sun’s radiate through the layer of the listed incorrectly as radiate through the layer of the listed incorrectly as Sun known as the radiative zone. creating extreme temperatures Sun known as the radiative zone. “degrees Kelvin” deep within the Sun’s core. “degrees Kelvin” core. 87 88

Nuclear Fusion in the Sun Nuclear Fusion in the Sun (and (and other stars) – the proton- other stars) – the proton-proton proton chain reaction: chain reaction: The decrease in mass (from 4 Note that the process starts protons to 2 protons and 2 with 4 protons and ends with neutrons) is only 0.7% but the one atom of helium-4 (4 energy release is large because protons are fused into one of the equation helium-4 atom) plus large e = mc2. energy release – the gamma Also note that at the end of the particles that eventually convert reaction, there are still two to photons (electromagnetic protons remaining, radiation, or light). so the reaction continues as a chain reaction (requiring very high temperature and pressure) always releasing energy. http://en.wikipedia.org/wiki/Nuclear_fusion http://en.wikipedia.org/wiki/Nuclear_fusion

15 Nuclear Fusion in the Sun (and other stars) – the proton- Nuclear Fusion in the Sun proton chain reaction: (and other stars) – the proton-proton chain reaction: The proton–proton chain reaction occurs around Reaction continues until 9.2×1037 times each second in the Hydrogen (source of the core of the Sun. The Sun the protons) is nearly all releases energy at the mass- converted to Helium. energy conversion rate of Energy from nuclear fusion in 4.26 million metric tons per stars larger than the Sun 26 second, (3.846×10 W) or (hotter and higher pressure 10 9.192 × 10 megatons of TNT core) is generated by the per second. Carbon-Nitrogen-Oxygen (http://en.wikipedia.org/wiki/Sun) (CNO), or other, chain reactions. http://en.wikipedia.org/wiki/Nuclear_fusion http://en.wikipedia.org/wiki/Nuclear_fusion

Tools of Astronomy: 1. Samples – meteorites (abundance of elements). 2. Photography – telescopes (Earth-based and satellite; visible and invisible wavelengths) 3. Distance measurement – stellar parallax, brightness method (variable stars), Hubble red shift. 4. Brightness – absolute and apparent magnitude (classification). 5. Spectroscopy – continuous spectrum (amount of radiation at different wavelengths; provides temperature of surface of star), bright line and dark line spectra (provides composition).

93 http://en.wikipedia.org/wiki/File:Solar_Spectrum.png

Sunspots are Life Cycle of the Sun temporary phenomena on the photosphere of the Sun that appear visibly as dark spots compared to surrounding regions. They are caused by In about another 5 billion years, the hydrogen will be nearly intense magnetic depleted and the Sun’s core will collapse and heat up activity, which resulting in helium fusion and the Sun will become a Red inhibits Giant with a size that will probably extend out to the convection, present orbit of Mars. forming areas of reduced surface http://en.wikipedia.org/wiki/Sun http://en.wikipedia.org/wiki/Sunspot temperature.

16 Note 11 year cycle of sunspots http://en.wikipedia.org/wiki/Sun http://en.wikipedia.org/wiki/Sunspot

The Hertzsprung-Russell (H-R) Diagram

Sun agnitude (Sun = 1) = (Sun y M Luminosit Absolute

Very bright stars have more shorter-wavelength radiation and higher temperatures. These measurements are from spectrometers. (Figure 16.4, text) http://csep10.phys.utk.edu/astr162/lect/sun/spectrum.html Surface Temperature (K)

The Hertzsprung-Russell (H-R) Diagram

Hotter stars have shorter wavelength radiation and shorter lifetimes

Sun agnitude (Sun = 1) = (Sun y M

“Classification of Stars” (Figure 16.5, text) Luminosit Absolute Cooler stars have longer wavelength radiation and longer H-R diagram illustrating life cycle of a main (Figure 16.4, text) lifetimes sequence star (such as the Sun). Most of lifetime, Surface Temperature (K) star is on Main Sequence, then in dwarf stage.

17 Low Mass (Figure 16.12, text) Low Mass (Figure 16.12, text)

Medium Mass Medium Mass

High Mass High Mass

Life cycle of stars – National Geographic, March 2014

Life cycle of stars 103 104

Low Mass (Figure 16.12, text) Low Mass (Figure 16.12, text)

Medium Mass Medium Mass

High Mass High Mass

Life cycle of stars – National Geographic, March 2014 Life cycle of stars – National Geographic, March 2014

105 106

Supernova remnant Cassiopeia A, located about 10,000 light years from Earth. Trifid Nebula (birthplace of Stars, mostly H and He gases illuminated by hot young stars).

Neutron Star

(Figure 16.1, text)

(also, Figure 16.9, text)

18 The Helix Planetary Nebula (formed during a star’s collapse from a red giant to a white dwarf). Horsehead (mostly dark) Nebula in constellation Orion.

(also, Figure 16.8, text)

The Crab Nebula (in the constellation Taurus; The Veil Nebula (in the constellation Cygnus; the remains of the supernova explosion of A.D. the remains of a supernova implosion). 1054).

(Figure 16.15, text) (Figure 16.14, text)

Galaxies – Typically consist of 1 billion to over 100 billion Spiral Galaxy M81 (NASA) stars. Most are relatively flat. Stars in the galaxy revolve around a central area, and thus don’t collapse (at least not quickly) from gravity (similar to the solar system). Most galaxies (including the Milky Way) probably have black holes in the center of the galaxy accounting for a substantial part of its mass. Types of Galaxies: Elliptical, Spiral, Irregular, Dwarf A tour of some galaxies…

(Chapter 16, text)

19 (Figure 16.17, text)

(Chapter 16, text)

Above: The Milky Wayy(p (panorama from Earth).

Right: Spiral galaxy Panoramic Photo (seven frames stitched together; time lapse NGC 2997 (similar to exposure; a quarter Moon provided the light to illuminate the mesas Milky Way). and foreground) of the Milky Way galaxy above Monument Valley, AZ (from Dec./Jan. 2012 issue of National Wildlife, www.nwf.org; http://www.nwf.org/News-and-Magazines/National- Wildlife/PhotoZone/Archives/2011/2011-National-Wildlife-Photo- (Chapter 16, text) Contest-Winners.aspx) (Figure 16.19, text)

Spiral Galaxy Andromeda The Barred spiral galaxy

(Figure 16.16, text)

(Figure 16.2, text)

Elliptical galaxy ESO 325-G004. Most elliptical galaxies are very old and probably Cosmic Web (structure of the universe, how the result from two galaxies colliding. galaxies are distributed in the universe) Videos –

Where the Galaxies Are – Margaret Geller, 1991

NASA /Goddard Space Flight Center Scientific Visualization Center:

Cosmic Origins Spectrograph: Large Scale Structure of the Universe

http://svs.gsfc.nasa.gov/vis/a010000/a010200/a010223/index.html

Journey Through the Cosmic Web

http://svs.gsfc.nasa.gov/vis/a010000/a010100/a010118/index.html

http://en.wikipedia.org/wiki/Elliptical_galaxy 119

20 How to find a galaxy, Margaret Geller. View of a slice of the universe, Measuring Distance to Stars (and Galaxies): 3. The each yellow dot is a galaxy. Note pattern Hubble Red Shift (a Doppler Effect) of empty space Moving object emitting radiation and close spacing.

 Motion  Observer here Observer here sees longer sees shorter wavelength wavelength radiation (red radiation (blue shifted) shifted)

NOVA, https://www.youtube. Doppler Effect (and Red Shift) – Animation available at: com/watch?v=gAyZbpSW15U 121 http://www.astro.ubc.ca/~scharein/a311/Sim.html

Measuring Distance to Stars (and Galaxies): 3. The Hubble Red Shift (mostly a Doppler Effect) Moving object emitting radiation

 Motion  Observer here Observer here sees longer sees shorter Example of Doppler Effect – Observer senses different wavelength wavelength wavelengths (hears different sounds) from approaching and radiation (red radiation (blue receding ambulance. Note that the ambulance moving away shifted) shifted) results in longer wavelengths. The faster the ambulance is moving away, the longer the wavelength (lower frequency Doppler Effect (and Red Shift) – Animation available at: sound). (Figure 16.22, text) http://www.astro.ubc.ca/~scharein/a311/Sim.html

Hubble’s Law Hubble’s Law

slope ~ 500 km/s Hubble, 1929 Mpc

Hubble's law is a statement of a direct correlation between the The reported value of the Hubble parameter has varied widely over the distance to a galaxy and its recessional velocity as determined by the years, testament to the difficulty of astronomical distance measurement. red shift. It can be stated as: But with high precision experiments after 1990 the range of the reported values has narrowed greatly to values in the range of:

H0 is the slope of the line http://hyperphysics.phy-astr.gsu.edu/hbase/astro/hubble.html http://hyperphysics.phy-astr.gsu.edu/hbase/astro/hubble.html

21 Modern Hubble’s At all locations, Law Data objects are 1) Virtually all moving away and galaxies are moving more distant away from us, e.g. objects have they are redshifted. higher recession 2) The more distant velocity. the ggy,galaxy, the larger its redshift, that is the faster it is moving away. Hubble’s original 1929 data Expanding Universe – As the universe expands, the galaxies get farther apart (although some are gravitationally connected and collide/merge) and 19 One MegaParsec (Mpc) = 3 million light years = 3 x 10 km increase their red shift. http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/bigbang.htm http://ircamera.as.arizona.edu/NatSci102/NatSci102/lectures/bigbang.htm

129 130

Expanding universe modeled as the surface of a balloon - Imagine a balloon A with points A, B and C labeled. After 1 expanding the balloon, the distances B 2 change.

C Time 1 A 2 From Time 1 to Time 2, increase in distance A B to B is 1, A to C is 2. So, 4 velocity for A to C is twice is large as from A to B. More distant C objects have higher Hubble Ultra Deep Field 3D recession velocity. This is true for all locations Time 2 http://www.youtube.com/watch?v=oAVjF_7ensg 131 on the surface. Distances in Red 132

22 Cosmic Microwave Background Radiation

Cosmic Microwave Background Radiation

With a traditional optical telescope, the space between stars and galaxies (the background) is pitch black. But with a radio telescope, there is a faint background glow, almost exactly the same in all directions, that is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum, hence the name cosmic microwave background radiation. The CMB's serendipitous discovery in 1964 by American radio astronomers Arno Penzias and Robert Wilson was the culmination of Observations of background radiation of the universe from the 1990 NASA work initiated in the 1940s, and earned them the 1978 Nobel Prize. COBE (Cosmic Background Explorer) satellite http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation

Cosmic Microwave Background Radiation The CMBR is well explained as radiation left over from an early stage in the development of the universe, and its discovery is considered a landmark test of the Big Bang model of Two of COBE's principal the universe. When the universe was young, before the formation of investigators, George Smoot stars and planets, it was smaller, much hotter, and filled with a and John Mather, received the Nobel Prize in Physics in 2006 uniform glow from its white-hot fog of hydrogen plasma. As the for their work on precision universe expanded, both the plasma and the radiation filling it grew measurement of the CMBR. cooler. When the universe cooled enough, stable atoms could form. These atoms could no longer absorb the thermal radiation, and the http://www.astro.ucla.edu/~wright/CMB.html universe became transparent instead of being an opaque fog. The photons that existed at that time have been propagating ever since, The Cosmic Microwave Background Radiation measured by the COBE though growing fainter and less energetic, since exactly the same satellite almost precisely fits the backbody radiation curve corresponding to photons fill a larger and larger universe. This is the source for the 2.725 K (-270.425 oC) – a very cold temperature due to cooling of the term relic radiation, another name for the CMBR. universe (in the space between galaxies and stars) and the red shift. http://en.wikipedia.org/wiki/Cosmic_microwave_background_radiation

The scale of the Universe – Earth and the Solar System

Logarithmic Scale

137 138

23 The scale of the Universe – Beyond the Solar System

Logarithmic Scale

Evidence for Big Bang Theory Black Holes

1. Red Shift, universe expanding A black hole is a region of space whose gravitational force is so strong that nothing can escape from it. A black hole is invisible because it even traps 2. Distant galaxies receding faster light. The fundamental descriptions of black holes are based on equations in the theory of general relativity developed by the German-born physicist Albert Einstein. The theory was published in 1916. 3. Cosmic background radiation Characteristics of black holes 4. Abundance of elements in the universe is consistent with The gravitational force is strong near a black hole because all the black mathematical models and nuclear physics of Big Bang hole's matter is concentrated at a single point in its center. Physicists call evolution of the universe this point a singularity. It is believed to be much smaller than an atom's nucleus. The surface of a black hole is known as the event horizon. This is not a 5. Einstein’s general theory of relativity predicts expanding normal surface that you could see or touch. At the event horizon, the pull universe of gravity becomes infinitely strong. Thus, an object can exist there for only an instant as it plunges inward at the speed of light. 6. Formation of galaxies and large scale structure of the universe http://www.nasa.gov/worldbook/blackhole_worldbook.html

Black Holes Black Holes Formation of black holes Supermassive black holes According to general relativity, a black hole can form when a massive star Scientists believe that most galaxies have a supermassive black hole at the runs out of nuclear fuel and is crushed by its own gravitational force. center. The mass of each of those objects is thought to be between 1 While a star burns fuel, it creates an outward push that counters the million and 1 billion solar masses. Astronomers suspect that supermassive inward pull of gravity. When no fuel remains, the star can no longer black holes formed several billion years ago from gas that accumulated in support its own weight. As a result, the core of the star collapses. If the the centers of the galaxies. mass of the core is three or more solar masses, the core collapses into a singularity in a fraction of a second. There is s trong ev idence tha t a supermass ive blac k ho le lies a t the cen ter of the Milky Way. Astronomers believe this black hole is a radio-wave Galactic black holes source known as Sagittarius A* (SgrA*). The clearest indication that SgrA* Most astronomers believe that the Milky Way Galaxy -- the galaxy in which is a supermassive black hole is the rapid movement of stars around it. The our solar system is located -- contains millions of black holes. Scientists fastest of these stars appears to orbit SgrA* every 15.2 years at speeds that have found a number of black holes in the Milky Way. These objects are reach about 3,100 miles (5,000 kilometers) per second. The star's motion in binary stars that give off X rays. A binary star is a pair of stars that orbit has led astronomers to conclude that an object several million times as each other. massive as the sun must lie inside the star's orbit. The only known object that could be that massive and fit inside the star's orbit is a black hole. http://www.nasa.gov/worldbook/blackhole_worldbook.html http://www.nasa.gov/worldbook/blackhole_worldbook.html

24 The following slides are just for interest (if you are in Houston, I highly recommend visiting these locations) Because black holes are invisible, they are mostly detected (inferred) form the gravitational forces required for objects 1. From tour of NASA Johnson Space which revolve around them and from radiation from nearby Center (JSC) in Houston, Texas (seven regions (outside the event horizon) that are energized by the rapid motion of objects and gases and emit x-ray radiation. slides) 2. Saturn 5 Rocket displayed in building near JSC entrance gate (5 slides) Some useful references: Chaisson, E., Relatively Speaking: Relativity, Black Holes, and the Fate of the Universe, W.W. Norton & Company, New York, 254 pp., 1988. 3. Paleontology and Gem and Mineral Ferris, T., Coming of Age in the Milky Way, Anchor Books, New York, 495 pp., display at Houston Museum of Natural 1988. Science (11 slides) http://www.nasa.gov/worldbook/blackhole_worldbook.html 146

1. NASA and Purdue astronaut, Drew Feustel, landed back on Earth on 10/04/2018, at about 7:45 a.m. EDT. NASA video of descent and landing on Soyuz MS-08: https://www.youtube.com/watch?v= pxaX7CtdGAg or The Space Shuttle https://www.youtube.com/watch?v= GWusG5EW3dU Purdue Today Article (10/4/2018): https://www. purdue. edu/newsroom/ releases/2018/Q4/astronaut- feustel-scheduled-to-return-to- earth-on-thursday.html

148

The Space Shuttle on a 747

Astronaut suits – weighing 300 lbs

149 150

25 40 ft deep weight-less training pool with Space Station modules. Astronauts in their space suits spend 6-hour training sessions in the International Space Station (ISS) modules for training. pool. Drew Feustel’s training in the pool was for over 800 hours. 151 152

Soyuz spacecraft. Upper left – module for returning to Earth from the ISS; two parts are jettisoned in the upper atmosphere before landing. Upper right – capsule 2. The Saturn V was an American human-rated expendable rocket (111 m holding the astronauts. Lower left long, 2,970,000 kg) used by NASA between 1967 and 1973. The three-stage – astronauts in the capsule. liquid-fueled super heavy-lift launch vehicle was developed to support the Apollo program for human exploration of the Moon and was later used to launch Skylab, the first American space station. https://en.wikipedia.org/wiki/Saturn_V 153 154

Capsule 

Saturn V on launch pad 

 Space Capsule

 Propulsion Rockets

155 156

26 Neil Armstrong on the Moon, Apollo 11, July, 1969 Neil Armstrong, Michael Collins and Buzz Aldrin – astronauts for Apollo 157 11 and Moon Landing, July, 1969. 158

3. Fossils, gems and minerals displayed at the Houston Museum of Natural Science (http://www.hmns.org/ - some photos are also online here) 159 160

161 162

27 163 164

Jaws of Giant Shark - 3 meter opening

165 166

Gold

167 168

28 169