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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To Not Blame Those Sent for Being Sent

via We Veterans Thank You

Two score and four years ago, my uncle returned from the Vietnam War to being ‘cursed, ridiculed’ and possibly assaulted because we blamed the soldiers for our government’s execution of foreign policy.  And I do mean ‘our’ government, since, for better or worse, our government is of, by and for the people.  We did this.  There is no one else we can blame.

In the intervening decades until his retirement in 1998, he returned from other wars to a very different homecoming.  For that, I’m eternally grateful.  By the time he returned from both Gulf Wars, I was no longer in the second grade where I was oblivious and sheltered from world events, but during a time when I had children of my own in grade school whom I wanted safe and sound.

For his service and sacrifice, he has my gratitude.  As do all his contemporary veterans.

War is an unpleasant business. Some wars are necessary; some are not. Regardless, it is terrible to send our sons and daughters to kill or be killed. But, until we learn not to practice war anymore, I’m happy that America has learned not to blame those sent for being sent.

— Col. Ronald Andrea, USAF, Retired

 

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To Serve Quietly (or Not) Against the Dying of the Light

This morning I woke early, as I nearly always do, but with a melancholic mood fogging my mind.  Two Hallmark movies and a cup of hot tea later and I still could not shake the malaise.  I turned off the television and grabbed the closest half-finished book handy and continued my perusal of Cosmic Discoveries with David Levy.  The subtitle for chapter nineteen was a quote I’ve heard many times but which I had never read the original source.  Since the chapter also started with another quote from the same work with a byline to the poet, I decide there’s no time like the present to read the original poem.

My tablet was charging across the room so I grabbed my smartphone and searched on the phrase and poet and got a crazy amount of hits – no surprise.  I read the Wikipedia article first to get some background on the poet and the when and partial why he wrote his now famous and often quoted poem.  Next, I returned to my results (from Wikipedia) and selected the first hit that contained the complete short poem.

I read it three times, because I read somewhere or was told by someone you should always read a poem three times.  I didn’t make it through the third stanza of the first reading before I couldn’t see my screen for the tears.  Damn poets! And at one point in my life I actually aspired to be a poet.  But life pretty much crushed the creativity out of me so I just enjoy those who had more courage than I to pursue their creative spark.

Good men, the last wave by, crying how bright
Their frail deeds might have danced in a green bay,
Rage, rage against the dying of the light.

— Dylan Thomas, ‘Do Not Go Gentle Into That Good Night

Reading this poem today reminded me of the sometimes quiet, always courageous sacrifices willingly given to us by our military service men and women.  Their continuing fight against the dying of the light allows me, my family, my friends, my acquaintances, my coworkers – all of us living in this great country that is the home of the brave and the land of the free – because of them.

Thank you, veterans, for your service.

Thank you for not going gently into any night and raging against the dying of the light to keep us safe and free.

Thank you.

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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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Library Version of ‘My Dog Ate My Homework’

I volunteer behind the circulation desk of my local library a few hours a week.  I look forward to my weekly chance to greet and assist our patrons.  Every minute is an opportunity for a new adventure or discovery.  As with most journeys, I experience and savor the high points and persevere through the more challenging bumps.

I empathized with a patron who returned a canine mauled book with a trade paperback edition replacement in hand. Unfortunately, according to our circulation policies specific to lost of damaged items, we can’t accept replacements purchased by patrons, but must charge for the replacement cost, plus a small handling fee. Why not take the replacement from the patron? In the case of print books, it’s usually because the bindings available from retail outlets won’t hold up as well as print editions bound for library circulation.

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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

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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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