StarWatch: Moravian College Astronomy

StarWatch for the greater Lehigh Valley

JUNE 2016

JUNE STAR MAP | MOON PHASE CALENDAR | STARWATCH INDEX | NIGHT SKY NOTEBOOK

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1033 JUNE 5, 2016: Living in the Matrix: Isaac Asimov’s short story, The Last Question, poses the query whether entropy, the wearing down of a system, in this case the universe, could be reversed. The story begins in 2061, but spans trillions of years as humanity expands into the cosmos, eventually populating it in its entirety. During the seven segments of the story, an “automatic computer” continues to reinvent itself assuming more responsibility for the regions of space into which humankind has advanced. With each reinvention, the computer grows smaller and more powerful until in the end, it becomes the consciousness of the universe, joining as one the minds of all humanity stretched across the vastness of space and time. During each segment in the narrative the computer is asked, “Can entropy be reversed?” After trillions of years of analysis, the computer finalizes an answer which is both shocking and yet benign in every aspect. Read The Last Question at http://www.physics.princeton. edu/ph115/LQ.pdf to find out. Related to Asimov’s story is the query of whether our universe is, in reality, a computer simulation. It was the topic of the 17th Annual Isaac Asimov Panel Debate (Google this) held on April 5 at the American Museum of Natural History in NYC. The group included three theoretical physicists, a cosmologist, a philosopher, and host, Neil deGrasse Tyson. During the discussions, members described the successes that we have achieved in our attempts to model quarks, the building blocks of matter/energy in the universe, and cosmic rays. If the universe is completely quantifiable, then with a computer large enough, we should be able to simulate it. Like computer programs, glitches occur; and the universe is no stranger to these. It defied the laws of nature just after its creation, allowing for the formation of hydrogen and helium that eventually evolved into sentient beings as well as its brief expansion faster than the speed of light. However, in the end the panel, except for Tyson, felt strongly about the premise that the matrix was not for us.

1034 JUNE 12, 2016: Don’t Ignore the Moon: It wasn’t so long ago that I abhorred having a moon in the sky when I made astronomical observations. When you consider what East Coast observers have to contend with, it is a small miracle that anyone wants to look up at all. Nearly half of the nights are mostly cloudy to cloudy, light pollution is everywhere, and the numbing cold of damp winter evenings creates a substantial increase in the prep time just needed to be out-of-doors. At Moravian College in Bethlehem, PA, all of these factors come into play, including the wind, since our nearly five-story sky deck is at tree line, too high for the airstream to be abated easily by ground objects. So the moon has become my really good friend. Yes, it can be bright, but it allows virtually everything to be seen distinctly against the black rooftop; and on clear evenings, Luna really doesn’t hinder the observation of double stars, star clusters, planets, or itself. That has probably been the most important lesson that I have learned about the moon. Because of its closeness, on average about 240,000 miles from Earth, it presents a wealth of detail that cannot be matched by any other celestial object. I have spent hours slowly traveling with my telescope along the moon’s terminator, the region where day turns into night. It is here that shadows are the longest and the smallest changes in surface elevation are easily revealed, like a craggy crater wall stretching its exaggerated silhouette 40 or 50 miles across its pan-shaped floor. Even if you don’t own a telescope or binoculars, watch the moon this week as it blossoms from just over first quarter (half on-half off, light to the right), on Sunday to nearly full by week’s end. On Tuesday, June 14, Luna is above the bright star Spica of Virgo the Virgin. By the 16th, 17th, and 18th, Luna passes above Mars, red Antares (Scorpius), and Saturn respectively, headed towards its full phase on the morning of June 20, summer solstice. Good observing!

1035 JUNE 19, 2016: Highest Sun, Lowest Moon: A curious situation happens on June 20, the summer solstice. On this date the sun reaches its highest position north of the equator, and for a location of 40 degrees north latitude, this will position the sun at an altitude of nearly 73.5 degrees above the horizon. At the exact moment of summer solstice (6:34 p.m. EDT), Sol will be positioned directly over the Tropic of Cancer, defining this extreme location on the surface of the Earth. I had always wondered as a kid, if I traveled to this location, would I really see a white, dashed line painted across the landscape similar to what I had observed on a globe of our planet? Not quite, I eventually discovered. The moon is also full on this date, but approximately 12.5 hours earlier (7:02 a.m. EDT) than the actual moment of the solstice. For the moon to be full, it must be exactly opposite in celestial longitude to the position of the sun. Since the due south position of the sun (1:04 p.m. EDT) is highest for the year, and the moon must be opposite to the sun to be full, this represents the lowest due south position of a full moon in 2016. If you live in Philadelphia, the moon is due south at 12:51 a.m. EDT, on the morning of June 20, six hours before being officially full. Luna will be just over 30 degrees above the horizon. This is actually quite high for the “lowest” full moon of the year. The moon’s orbital plane is tilted to the plane of the Earth’s orbit, the ecliptic, by five degrees. By definition the sun must always be on the ecliptic, but the moon is rarely on the ecliptic unless it is crossing it, and these crossing positions called nodes sweep around the entire sky in an 18.61 year interval. This means that the lowest full moon of a year can occur within the range of 21.5 degrees to 31.5 degrees in altitude for individuals living at 40 degrees north latitude. If you live north of that latitude, simply subtract the difference in your latitude to obtain the minimum and maximum extremes for the summer full moon, and add the difference in latitude if you live south of 40 degrees north. The moral of this story is that nothing is as simple as it seems in astronomy.

1036 JUNE 26, 2016: Gravity Waves Confirmed for Second Time: When I introduce astronomy to my classes, I can’t help touching upon the four forces of nature which govern our natural world: the strong, the weak, the electromagnetic, and gravity. “Which of these forces is the strongest?” I query. “Well, it’s clearly gravity,” is the standard answer. Jump off a building and gravity will kill you. “Well not exactly,” I explain. Gravity will cause you to accelerate towards the center of the Earth, but your very rapid deceleration upon hitting the pavement is what kills you. Because matter is mostly empty space, the more fundamental question is “Why don’t we simply pass through the pavement and just keep on going?” All matter is composed of protons and neutrons which form the nuclei of atoms, but atomic nuclei are surrounded by a haze of electrons. When you get very close to the pavement in your death plunge, the electrons of your body repel the outermost electrons of the pavement, and you STOP really, really fast. Gravity is the weakest of the four forces, but it governs how the universe behaves—how space (dimensions) and time get stretched and squeezed by the presence of matter as predicted by Einstein a century ago in his general theory of relativity. What better way to detect these fluctuations than with the dance between two massive black holes spiraling into each other and then amalgamating themselves into one. This scenario has now been detected twice by the Laser Interferometer Gravitational-Wave Observatory (LIGO), the most recent event announced on June 16, detailing the gravitational distortions created by two black holes, 7.5 and 14.2 solar masses that merged. About one solar mass was converted into gravitational energy that traveled at light speed for 1.4 billion years to reach LIGO. That was a whisper compare to LIGO’s first detection of the amalgamation of two 30 solar mass black holes last December 26. Refinements will continue to make LIGO more sensitive so that the detection of less massive events may soon be seen on a weekly basis.

[June Star Map]

[June Moon Phase Calendar]