Looking Outward and Learning

The Summer Triangle

By Tomruen at en.wikipedia - Own workTransferred from en.wikipedia, Public Domain, https://commons.wikimedia.org/w/index.php?curid=11126314

Copyright © 2018

By Ralph F. Couey

Except cited references and images

Cheryl and I have started to spend an evening here and there at Ala Moana Beach Park as a way of decompressing from the pressures of our daily responsibilities.  It's a nice place from which to watch the sunset, as our Facebook friends have noted recently.  Usually by that time, the tourists have largely cleared out, so we end up with a relatively empty stretch of sand.  One of the delights is an unobstructed view of the sky as it darkens, and the appearance of stars, one by one as Earth's great beacon moves below the horizon.

I have been sitting in the back yard doing this for a few weeks and while it is peaceful and relatively cool, I don't get a huge sky view because of houses and trees.  Also, recently I acquired a free app on my phone called, appropriately enough, Skyview.  It's easy to use.  Activate it, point the phone at a particular star, and the app identifies it for you.  Granted, it's a bit cumbersome, but still, it is a great educational tool for those taking their first tours of the sky.

So, this week I learned about the asterism called "The Summer Triangle."  It consists of three of the brightest stars in the sky, Deneb, Altair, and Vega, the brightest, or Alpha stars of their respective constellations.  (An asterism, by the way, is a stationary pattern of stars in the sky smaller than a constellation.)  Never satisfied with simple answers, I undertook the task of educating myself about these bright points of light.



This grouping has been recognized by humans for at least 2,600 years.  Because the nature of those stars provides a method by which humans can find their place on this planet, they have also been known as the "Navigator's Triangle."

Deneb is the brightest star in the constellation Cygnus the Swan.  It is characterized as a blue-white supergiant and is rated the 19th most luminous object in the sky.  It's distance from here is a matter of some debate, the nuts and bolts of which I won't attempt to explain.  The current estimates run from about 1500 to 2600 light years away.  What is known is that Deneb is around 200,000 times more luminous than Earth's star, and 200 times larger.  Like all giant stars, it's lifespan is far shorter than our star, and in fact has already begun to cool and expand as it has used up it's supply of hydrogen in the core.  Deneb's fate is uncertain, but it may become a red supergiant, finally exploding into a supernova a few million years from now.

Deneb

https://coraskywalker.files.wordpress.com/2010/05/deneb5.jpg

Altair is the alpha star in the constellation Aquila the Eagle.  This constellation is also home to the famous, evocative, and stunningly beautiful "Pillars of Creation" captured by the Hubble Space Telescope.  Altair is a relatively close 16.7 light years distant from Earth.  One of the unusual aspects of this star is it's very high rotational speed, about 180 miles per second.  By comparison, Earth's sun rotates at a comparatively sedate 1.2 miles per second.  Because of this, the star is not round, but oblate in appearance, confirmed when Altair became the first star ever directly imaged.  It is about 2 times the sun's size and mass, and eleven times brighter.  Also a short-lived star, Altair will last only about a billion years before it's outer layers begin to puff away, eventually leaving a small but incredibly dense white dwarf.

Altair, the first direct image of an extra-solar star.

By Altair_PR_image6.jpg: Ming Zhao, John Monnierderivative work: [[User:Omnidom 999|Omnidoom 999]] [[User Talk:Omnidom 999|'''ⁿسالكانⁿ''']] (talk) - Altair_PR_image6.jpg, Public Domain, https://commons.wikimedia.org/w/index.php?curid=6026702

A dust disk has been detected around the star, but is thought to be leftover debris from the star's formation and not a nursery for planets.

The third partner in this trio is Vega, the brightest star in the constellation Lyra the Harp.  It is a blue-tinged white main-sequence star, about 25 light years from Earth.  Like Altair, the star has an extremely high rotational speed, 170 miles per second and is therefore also oblate in shape.  It is twice the sun's mass, about 2.7 times the sun's circumference, and 40 times brighter.  Again a short-lived star, Vega, like Altair, is halfway through it's billion-year lifespan and will eventually become a red giant.  When the outer layers are finally shed, a small white dwarf will remain.

Vega in near infrared light, showing the dust disk.

By Courtesy NASA/JPL-Caltech/University of Arizona - Jet Propulsion Laboratory, Public Domain, https://commons.wikimedia.org/w/index.php?curid=651561

Vega has been called the most important star in the sky except the sun.  In 1850, it was the first star to be photographed, the first star to have it's EM spectra measured, and the first star to have an orbiting dust disk discovered.  Modern analysis strongly suggests the presence of several Neptune or Jupiter-sized planets orbiting the star.  Because of known wobbles in Earth's polar axis (called precession) Vega was the northern pole star 12,000 years ago, and will be again about 13,000 years hence.  The current pole star, the one aligned along Earth's axis, is the star known as Polaris.  Interestingly, because of the alignments, Earth's sun is Vega's pole star.  Vega has held a prominent place in the legends and histories of every human culture, and still fascinates today.

This kind of information fascinates me, although excessively boring to others.  When I look up at the night sky, my mind is filled with questions, most of which are unanswerable.  I understand that I am not looking at a static image, but thousands of objects that are evolving, changing, being born, and dying.  From here, those points of light appear to be placidly beautiful.  But up close they are often very violent and deadly places.  With the continuing gains in sensor capability, our knowledge and understanding of the universe will continue to increase.  But like many such inquiries, the discovery of one answer will generate a hundred new questions, and the quest begins anew.

Does the knowledge  of that vast unknown make me feel small and insignificant?  Sometimes.  But more and more often, I understand so much more clearly how precious life is, how short a life can be, and the absolute need not to waste either.

It is, you might say, my responsibility to the universe.