8 The giant planets

8 The giant planets

8.1Giant planets are large, cold, and massive

8.1.1 Overview

Brown, Mike. How we discovered planet X,” Astronomy, 44, 6, June 2016, pp. 20-25

Sheppard, Scott S. “The hunt for planet X,” Sky and Telescope, 134, 4, October 2017, pp. 16-21

8.1.2 Characteristics of the giant planets

Dunham, David. “Preliminary results from Triton cover-up,” Sky and Telescope, 135, 2, February 2018, p. 13

8.1.3 Composition of the giant planets

8.1.4 Rotation of the giant planets

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9 Small bodies of the Solar System

9 Small bodies of the Solar System

9.1 Dwarf planets may outnumber planets

9.1.1 Overview

  1. Kelly Beaty, “Dwarf planet Haumea has a ring,” Sky and Telescope, 135, 2, February 2018, p. 12

9.2 Moons as small worlds

9.2.1 Overview

9.2.2 Geologically active moons

9.2.3 Possibly active moons

9.2.4 Formerly active moons

9.3 Asteroids are pieces of the past

9.3.1 Overview

9.3.2 Asteroid Groups

Beatty, J. Kelly. “Astronomers spot first-known interstellar ‘comet,’” Sky and Telescopes (October 25, 2017). Accessed at http://www.skyandtelescope.com/astronomy-news/astronomers-spot-first-known-interstellar-comet/

Beatty, J. Kelly. “A visitor from interstellar space,” Sky and telescope, 135, 2, February 2018, p. 10 ‘Oumuamua

Clark, Stephen. “An interstellar interloper is dashing through our Solar System,” Astronomy Now (February 28, 2018) accessed at https://astronomynow.com/2017/11/22/an-interstellar-interloper-is-dashing-through-our-solar-system/

9.3.3 Asteroid composition

9.3.4 Visits to asteroids

Chang, Kenneth, “A metal ball the size of Massachusetts that NASA wants to explore,” A version of this article appears in print on January 10, 2017, on p. D2 with the headline: “Lost world: A planetary core, without the planet.” Accessed at https://www.nytimes.com/2017/01/06/science/nasa-psyche-asteroid.html Retrieved April 13, 2018

9.4 Comets are clumps of ice

9.4.1 The homes of the comets

  1. Alan Stern, “New Horizons explores the Kuiper Belt,” Astronomy (46, 2, February 2018, pp. 26-31)

9.4.2 The orbits of comets

9.4.3 Anatomy of an active comet

9.4.4 Visits to comets

9.5 Comet collisions still happen today

9.5.1 Overview

9.6 Meteorites are remnants of the early Solar System

9.6.1 Origins of meteorites

9.6.2 Types of meteorites

9.6.3 Meteorites and the history of the Solar System

10 Measuring the Stars

10 Measuring the Stars

10.1 The luminosity of a star can be found from the brightness and the distance

10.1.1 We use parallax to measure distances to nearby stars

10.1.2 The brightness of a star

10.1.3 Finding luminosity

10.2 Radiation tells us the temperature, size, and composition of stars

10.2.1Wien’s law revisited: The color and surface temperature of stars

10.2.2 Atomic energy levels

10.2.3 Emission and absorptions lines are the spectral fingerprints of atoms

10.2.4 Classification of stars

10.2.5 Information from spectral lines

10.2.6 The Stefan-Boltzmann law and finding the sizes of stars

10.3 The mass of a star can be determined in some binary systems

10.3.1 Binary stars orbit a common center of mass

10.3.2 Kepler’s third law and total mass of a binary system

10.4 The H-R diagram is the key to understanding stars

10.4.1 The H-R diagram

10.4.2 The main sequence

104.3 Stars not on the main sequence

11 Our Star: The Sun

11 Our Star: The Sun

11.1 The structure of the Sun is a matter of balance

11.1.1 Hydrostatic equilibrium

11.1.2 Nuclear fusion

11.1.3 The proton-proton chain

11.1.4 Observing the heart of the Sun with neutrinos

Byrd, Deborah, “Now We Know Earth Blocks Neutrinos,” Earth|Human World, November 27, 2017, accessed at http://earthsky.org/earth/earth-blocks-neutrinos-icecube-south-pole.

11.2 Energy in the Sun’s core moves through radiation and convection

11.2.1 Energy transport

11.2.2 Helioseismology

11.3 The atmosphere of the Sun

11.3.1 Observing the Sun

11.3.2 The solar spectrum

11.3.3The Sun’s outer atmosphere: Chromosphere and corona

11.4 The atmosphere of the Sun is very active

11.4.1 Solar activity is caused by magnetic effects

11.4.2 Sunspots and changes in the Sun

11.4.3 The effects of solar activity on Earth

12 Evolution of Low-Mass Stars

12 Evolution of Low-Mass Stars

12.1 Life of a main-sequence star follows a predictable path

12.1.1 Changes in structure

12.1.2 Helium ash in the center of the star

12.2 A star runs out of hydrogen and leave the main sequence

12.2.1 Electron-degenerate matter in the helium core

12.2.2 Hydrogen shell burning

12.2.3 Evolution of the star on the H-R diagram

12.3 Helium begins to burn in the degenerate core

12.3.1 Helium burning and the triple-alpha process

12.3.2 A helium flash

12.4 The low-mass star enters the last stages of its evolution

12.4.1 Moving up the asymptotic giant branch

12.4.2 Stellar mass loss

12.4.3 The post-AGB star

12.4.4 White dwarfs

12.5 Star clusters are snapshots of stellar evolution

12.6 Binary stars sometimes share mass, resulting in novae and supernovae

12.6.1 The flow of mass from an evolving star to its companion

12.6.2 Evolution of a close binary system

12.6.3 The second star evolves

12.6.4 A stellar cataclysm

_________. “Amateur astronomer makes once-in-lifetime discovery,” Astronomy Now, February 23, 2018, accessed March 1, 2018 at https://astronomynow.com/2018/02/23/amateur-astronomer-makes-once-in-lifetime-discovery/?utm_source=Astronomy+Now+Newsalert&utm_campaign=84903d39e5-AN+NewsAlert%3A+4+November+2017&utm_medium=email&utm_term=0_e789188a36-84903d39e5-163724113&mc_cid=84903d39e5&mc_eid=1fe40eabec

13 Evolution of High-Mass Stars

13 Evolution of High-Mass Stars

13.1 High-mass stars follow their own path

13.2 High-mass stars go out with a bang

13.2.1 Introduction

13.2.2 The final days in the life of a massive star

13.2.3 The core collapses and the star explodes

Young, Monica, “The star that wouldn’t die,” Sky and Telescope (135, 2, February 2018, p. 12

13.3 Supernovae change the galaxy

13.3.1 Introduction

Melott, Adrian L. “How supernovae have affected life,” Astronomy, 46, 4, April 2018, pp. 44-49. The article focuses on the effect of supernovae characterized by the explosion of stars, on the life on planet Earth. Topics discussed include the implication of the blue light generated by supernovae on the depletion of the Earth’s ozone, the impact of the cosmic waves consists of atomic nuclei and protons on human life, and the effect of the rays on increasing the Earth’s flux of muons on the ground.

13.3.2 The energetic and chemical legacy of supernovae

13.3.3 Neutron stars and pulsars

13.3.4 The Crab Nebula: Remains of a stellar cataclysm

13.4Einstein moved beyond Newtonian physics

13.4.1 The speed of light in a vacuum

13.4.2 Time dilation

13.4.3 The implications of relativity

13.5 Gravity is a distortion of spacetime

13.5.1 Free fall and free float

13.5.2 Spacetime as a rubber sheet

13.5.3 The observable consequences of general relativity

Betz, Eric, Robert Naeye, and Jake Parks. “The first observation of a gravitational wave source,” Astronomy, 46, 2, February 2018, p. 10

Carlisle, Camille M. “LIGO sees its smallest black hole binary yet,” Sky and Telescope, 135, 2, February 2018, p. 11

Govert Schilling, “When neutron stars collide,” Sky & Telescope (135, 2, pp. 32-39)

13.6 Black holes are a natural limit

13.6.1 Overview

13.6.2 Properties of black holes

13.6.3 “Seeing” black holes

Monica Young, “Decoding a black hole jet,” Sky and Telescope, 135, 2, February 2018, p. 13

Shoreless Seas, Stars Uncounted

Shoreless Seas, Stars Uncounted[1]

A fantastical float down the Milky Way.

The realm of fairy-story is wide and deep and high and filled with many things: all manner of beasts and birds are found there; shoreless seas and stars uncounted; beauty that is an enchantment, and an ever-present peril; both joy and sorrow as sharp as swords. In that realm a man may, perhaps, count himself fortunate to have wandered, but its very richness and strangeness tie the tongue of a traveler who would report them.

— J. R. R. Tolkien, “On fairy-Stories”

We journey down the Heavenly River, the Milky Way. As in the quote from Tolkien above, the “richness and strangeness” of this realm in the sky are so great they defy our attempts to describe them.

The fantastic Milky Way river. One of the major points of Tolkien’s essay is that the wonder at the heart of fantasy can sometimes be found even in its simplest stories, those usually considered to be aimed at children. But who would have thought that this wonder, or a large part of it, could also be found in the section of the Milky Way from Scutum to Sagittarius?

Do we have in the summer Milky Way “all manner of beasts and birds” as we do in Faerie (the realm at the heart of fairy-story)? Certainly. We have constellation beasts and birds galore—Scorpius (the scorpion), Sagittarius (half-man/half-horse), Serpens (the serpent), Delphinus (the dolphin), Vulpecula (the fox), Cygnus (the swan), Aquila (a soaring eagle), and Lyra (not just a lyre, but at one time, a stooping eagle or vulture). We also have a bevy of strange “beasts” from the “astrophysical zoo”—things like the variable stars Chi (χ) Cygni and Beta (β) Lyrae, and the visible remnants of the most bizarre stellar corpses, like the Dumbbell and Ring Nebulae, derived from solar-mass stars dying to become white dwarfs, and the more elusive Veil Nebula, derived from a massive star dying in a supernova to become a neutron star or black hole.

The summer Milky Way also has “stars uncounted” and, if not “shoreless seas,” at least the shoreless bank of a celestial river, for the edges of the Milky Way band fade off imperceptibly. Are there in the Milky Way joys and sorrows as sharp as swords? Well, with larger aperture telescopes there are innumerable blade-edge sharp images of the stars that incite joy in the observer. And you know in winter there’s a sword—Orion’s—as sharp as joys or sorrows.

Scutum to Sagittarius: a Milky Way river torrent of grandeur. Do we go over a kind of waterfall when we reach the Scutum Star Cloud with its foreground telescopic “avalanche of stars” (or spate of stars) called the star cluster Messier 11? Do we then pour down past the equilateral triangle formed by the Gamma Scuti Star Cloud, M16 (the Eagle Nebula), and M17 (the Omega Nebula)? And onward, through the intense bright “foam” of M24 (the Small Sagittarius Star Cloud), flanked by the open clusters M25 and M23, until we arrive at a vision of the broadly spread central bulge (or river delta?) of the Milky Way with M20 (the Trifid Nebula), M8 (the Lagoon Nebula), and the gorgeous Large Sagittarius Star Cloud? And don’t forget Sagittarius’s supreme globular cluster, M22, which hangs just upper left of the star at the top of the Sagittarius Teapot, and the pair of big naked-eye clusters levitating above Scorpius’s stinger, MG and M7.

River Anduin or path of souls? Tolkien’s fantasy river Anduin has a waterfall, Rauros. Downstream stand the grand cities Osgiliath and Minas Tirith. But maybe the Milky Way more closely resembles the path that dead souls take to their final destination near Antares as envisioned by some Native Americans. If the latter is true, then what do we make of Mars and Saturn passing through that high holy ground this year? (2016)

[1] Fred Schaaf, “Shoreless Seas, Stars Uncounted,” Sky and Telescope (132, 3, September, 2016, p. 45).