Category: Non-Fiction

Do You Hear What I Hear?

My final astronomy discussion topic attempts to answer “Why are some wavelengths of radio emission better than others in searching for extraterrestrial civilizations?”

Plot of Earth's atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation.
Plot of Earth’s atmospheric transmittance (or opacity) to various wavelengths of electromagnetic radiation.

 

Radio waves can travel immense distances without being significantly altered by interstellar medium.  They penetrate dust and gas and are the logical choice for interstellar communication.  Astronomers have been listening for signs of extraterrestrial life using the radio spectrum since the 1950s and 60s – long before scientists had discovered the means of detecting exoplanets.  But the sheer number of both radio frequencies and directions to search proved daunting and raised question like “Which frequencies should be used to maximize the odds of detecting an alien signal?”

Continue reading “Do You Hear What I Hear?”

Universal Song Remains the Same and Beyond All the Light We Cannot See

For such a small chapter, this week’s topic on Cosmology has some large and deep concepts.  I’m attempting to delve into “How did the period of inflation cause the universe to become homogeneous and isotropic?”

Definitions

Big Bang ~ Universe began as an extraordinarily hot, dense primordial atom of energy and caused expansion, just like an explosion.  Before that moment, nothing existed, not even space and time.  Rather, the explosion created spacetime, which continues to expand.  (Comins, 446)

Inflationary Epoch ~ During this epoch, the universe became so large that today we can only see a tiny portion of it and that is limited by the speed of light.  The growth and size of the observable universe occurred in a very brief time.  (Comins, 451)

Cosmic microwave background (CMB) ~ If the universe began with a hot Big Bang, then calculations indicated the energy remnants should still fill all of space today. The entire universe’s temperature should be only a few kelvins above absolute zero.  This radiation’s blackbody spectrum peak should lie in the microwave section of the radio spectrum.  (Comins, 446)

Isotropy of CMB ~ The cosmic microwave background radiation is almost perfectly isotropic – the intensity is nearly the same in every observable direction.  Isotropy isn’t just limited to observed blackbody radiation, but is also found on a large scale when exploring the number of galaxies found in different directions.  (Comins, 448)

Homogeneity ~ The uniformity with distance (the numbers of galaxies stays roughly constant with respect to both distance and direction) of the universe is homogeneous. (Comins, 449)

Fine-Tuning Big Bang

Any viable theory of cosmology, including the Big Bang, must explain the isotropy and homogeneity of the universe.  Numerous refinements have been posited and as a result the theory now provides an accurate scenario for the evolution of universe from a tiny fraction of a second after it formed and onward to today.  (Comins, 449) Continue reading “Universal Song Remains the Same and Beyond All the Light We Cannot See”

Just A Sun-Day Drive Around the Galactic Neighborhood

This week I’m tackling the subject of our Sun’s motion through the Milky Way Galaxy and approximately how long one orbit is.

The Milky Way Galaxy has two major spiral arms, named the Perseus Arm and the Scutum-Centaurus Arm.  There are also smaller less pronounced arms, including the Sagittarius Arm, the Norma Arm, The Local Arm (aka the Orion Spur) and the Outer Arm.  Our solar system resides in the Orion Spur (Local Arm), branching off from the larger Perseus Arm.  During the summer months in the northern hemisphere, we predominantly observe the Sagittarius Arm, including the galactic center, which appears as steam from the Tea Pot asterism in the constellation Sagittarius.  (Gaherty, 2016)  Over the winter, we’re looking away from the galactic center and through the Perseus Arm.  (Comins, 396)

Artist’s concept of what astronomers now believe is the overall structure of the spiral arms in our Milky Way galaxy. The sun resides within a minor spiral arm of the galaxy, called the Orion Arm. Image via NASA and Wikimedia Commons.

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Stellar Death Blasts

This week I discuss types of supernovae, specifically relating to the scenario where “Hydrogen lines are prominent in Type II supernovae but absent in Type Ia.  Type Ia supernovae decline gradually for more than a year, whereas  Type II supernovae alternate between periods of steep and gradual declines in brightness. Type II light curves therefore have a step-like appearance.  Explain!”

Supernovae are classified as Type I or Type II depending upon the shape of their light curves and the nature of their spectra.

The question I really wanted to ask is ‘What happened to Type I or Ib?’ and the answer to that question was easily found in this chart:

Supernovae Taxonomy
Supernovae Taxonomy

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Flashy, Bizarre, Weird Degeneracy

Just in time for Halloween, my topic this week focuses on electron degeneracy pressure specifically to delve into how “A degenerate gas does not expand when the temperature increases as an ordinary gas does.”

In 1923, Arthur Stanley Eddington derived a formula to relate the luminosity of a star to its mass, and in the same year correctly interpreted high-density, white dwarf stars as being formed of matter so dense that atomic electrons have collapsed from their orbits, a substance we now call degenerate matter. (Levy, p. 116)

Young giant stars of a certain size, between .4 and 2 solar masses, have helium rich cores squeezed by gravitational force into a crystal-like solid.  At these pressures, the atoms become completely ionized, separately into nuclei and electrons and are so closely crowded together that become influenced by the Pauli exclusion principle phenomenon.  Two identical particles are not allowed to exist in the same place and time.  As the electrons are pressed closer and closer together, the exclusion principle forces many of them to move faster and faster so they do not become ‘identical’ (meaning occupying the same space and moving with the same speed of adjacent electrons) and consequently this motion increases the repulsion between the electrons.  This state provides pressure in the core preventing it from collapsing and is referred to by astronomers as degeneracy.  Thus, low-mass giants with helium-rich cores are supported by electron degeneracy pressure. (Comins, p. 335)

Very high density matter, the structure of which is modified by the intense gravity. Particles, which must “squeeze”, create the degeneracy pressure.

If that wasn’t bizarre enough, here’s where it gets weirder:  A degenerate core’s pressure does not change with temperature.  Continue reading “Flashy, Bizarre, Weird Degeneracy”

Books I Loved 2017 Edition

At the end of September I reached that point in the year when I could shake off all my various book club obligatory reading and get down to the serious business of reading the books I bought for myself all year long.  Not every year gives me a break where I can read what I want.  I often have to squeeze in my ‘must read’ books between the two to three other books I read per month for various discussion groups and book clubs.  Don’t get me wrong.  I very much enjoy reading outside my comfort zone and would not give up the wonderful discussions and cherished friendships I’ve nurtured through a shared love of reading.

Moss "Loved-It" Shelf YTD 2017

Most years, I read between 75 and 100 books; last year I read 88 and as of today I’ve read 99 thus far in 2017.  And only about ten percent make it onto my ‘loved-it’ shelf (the equivalent of a five-star rating).  This year had a few more than normal and will probably end with two to three more on the shelf before year’s end (because I’m now reading what I’ve had on hold for most of the year).

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Absolute Magnitude Luminates Absolutely

This week I want to discuss “What might cause the closer of two identical stars to appear dimmer than the farther one?”

Apparent Magnitude: A measurement of the brightness of stars without regard to their distance from Earth.

  • The scale in use today starts with the star Vega and an apparent magnitude of 0.0
  • Objects brighter than Vega are assigned negative numbers.  For example. Sirius, the night’s brightest star, has an apparent magnitude of -1.44
  • The scale was extended to include the dimmest stars visible through binoculars and telescopes.  For example, a pair of binoculars can see stars with an apparent magnitude of +10

Ignoring distance for a moment, all other things being equal, the closer of two identical stars will appear brighter (have a smaller apparent magnitude) to us than the more distant star.  When we account for the difference in distance, we use either or two measurements:  absolute magnitude and luminosity.

Absolute Magnitude: The brightness a star would have at a distance of ten parsecs (10 pc) or 32.6 ly. Continue reading “Absolute Magnitude Luminates Absolutely”

Solar Cycle Stranger Things

I’ve reached the halfway point through my Introduction to Astronomy class. This week marks the eighth week of fifteen, sixteen if you count the first week where we just spent time getting to know each other and exploring the textbook and getting the lab software, Starry Night, installed and licensed. Last week, we reached the outer limits in the Kuiper Belt and Oort Cloud of our solar system where only comets and Voyagers I and II have ventured. Now we’ve snapped back to study our closest star, Sol, or more commonly just the Sun. My topic for discussion responds to the following question:

Why is the solar cycle said to have a period of 22 years, even though the sunspot cycle is only 11 years long?

Some surface features on our active Sun vary periodically in an eleven year cycle.  The Sun’s magnetic fields which cause the surface changes vary over a twenty-two year cycle.  The relatively cool and slightly darker regions, commonly called sunspots, are produced by local concentrations of the Sun’s magnetic field piercing the photosphere.  The latitude and number of sunspots on average vary during the same eleven year cycle.  But the hemisphere where the Sun’s north magnetic pole anchors during one eleven year cycle will have south magnetic poles during the next.  Because it takes a full twenty-two years for the magnetic poles to return to their original orientation astronomers refer to the entire solar cycle.   The magnetic dynamo model posits that many transient features of the solar cycle are caused by the effect of differential rotation and convection on the Sun’s magnetic field.  The Sun’s differential rotation (different speeds at different latitudes) causes its magnetic field to become increasingly stretched like a rubber band.  The bands can’t break so they periodically untangle themselves with the help of trapped gases which leak out (sunspot) and gradually settle back under the photosphere, when the sunspot disappears.  The most recent reversal of the Sun’s magnetic field occurred in 2013.  We are currently at the tale end of Solar Cycle 24.  (Comins, 2015, p.  272-83)

Continue reading “Solar Cycle Stranger Things”

No, Chicken Little, the Sky is Not Falling

My topic for discussion this week will attempt to answer the question:

Why do astronomers believe that the debris that creates many isolated meteors comes from asteroids, whereas the debris that creates meteor showers is related to comets?

But first, I want to share two things that serendipitously fell from my Twitter feed (@mossjon) today.  Today’s APOD (Astronomy Picture of the Day @apod) featured the unusual mountain on Ceres (Comins, 2015, p. 239).

What created this unusual mountain? Ahuna Mons is the largest mountain on the largest known asteroid in our Solar System, Ceres, which orbits our Sun in the main asteroid belt between Mars and Jupiter. Ahuna Mons, though, is like nothing that humanity has ever seen before. For one thing, its slopes are garnished not with old craters but young vertical streaks. One hypothesis holds that Ahuna Mons is an ice volcano that formed shortly after a large impact on the opposite side of the dwarf planet loosened up the terrain through focused seismic waves. The bright streaks may be high in reflective salt, and therefore similar to other recently surfaced material such as visible in Ceres’ famous bright spots. The featured double-height digital image was constructed from surface maps taken of Ceres last year by the robotic Dawn mission. (“APOD: 2017 October 9 – Unusual Mountain Ahuna Mons on Asteroid Ceres,” 2017)

The second thing that immediately caught my eye today was an episode of Astronomy Magazine‘s “The Real Reality Show” entitled “How an Asteroid Killed Off the Dinosaurs” covered late in Chapter 8 of our textbook (Comins, 2015, p. 263-4) and which also bonked me on the head via my Twitter feed:

[youtube https://www.youtube.com/watch?v=_6WAu0mtZRk?rel=0]

(“Real Reality Show: How an Asteroid Killed Off the Dinosaurs | Astronomy.com,” 2015)

But enough from our sponsors.  On with the real show and convincing Chicken Little that the sky is indeed not falling.

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Blue and Green with Envy

In this week’s discussion topic, I attempt to answer the question “Why are Uranus and Neptune distinctly bluer than Jupiter and Saturn?”

On Uranus and Neptune, the methane absorbs red, orange and yellow light, reflecting back the blue.  In contrast, Jupiter and Saturn have only minor trace amounts of methane and quite a bit more hydrogen and ammonia.

This view of Uranus was recorded by Voyager 2 on Jan 25, 1986, as the spacecraft left the planet behind and set forth on the cruise to Neptune Even at this extreme angle, Uranus retains the pale blue-green color seen by ground-based astronomers and recorded by Voyager during its historic encounter. This color results from the presence of methane in Uranus’ atmosphere; the gas absorbs red wavelengths of light, leaving the predominant hue seen here. Image Credit: NASA/JPL

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