StarWatch: Moravian College Astronomy

OCTOBER 2017

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

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lunar phases

1102 OCTOBER 1, 2017: Bright Moon—Summer Triangle Overhead: This is the week of the Harvest Moon (October 5), a time of the year when successive full and nearly full moonrises occur with the smallest amount of time between them. Farmers harvesting their crops long after sundown would be able to continue their work by the light of the full to nearly full moon. All this week the nighttime sky is going to be moon-splashed, leaving only the brightest stars visible. That can be good or bad; bad if you’re one my students trying to see objects from Collier’s Sky Deck because now moonlight plus city lights equal even less stars on a clear evening; good if you are trying to learn the operation of a complex telescope because the light of a full or nearly full moon will allow the scope and its various parts, even the direction sheets, to be seen and read with little difficulty. So, look at the moon. It has lighter and darker regions. Many of the darker maria are circular in shape, a result of titanic meteorites striking the moon about 3.85 billion years ago. All except for one struck the nearside of the moon, the hemisphere which is continuously positioned towards Earth. The age of the maria are about three billion years old while the highlands or the whiter areas are at least a billion years older and represent the original crust of the moon. Look straight up and you’ll see the three bright stars of the Great Summer Triangle. The heavens are filled with triangles, any three stars not in a “straight” line, but the GST is bright and will be visible in the light of a luminous full moon. It is not a constellation, but rather an asterism, a group of stars which form a well-known picture; however, it is not officially recognized by the International Astronomical Union, the congress of professional astronomers. The GST is composed of the stars Vega (Lyra the Harp), Altair (Aquila the Eagle), and Deneb (Cygnus the Swan). In order of brightness they are Vega, Altair, and Deneb. In fact, Deneb is noticeably the faintest of the triad, but looks can be deceiving. Altairis closest at about 16 light years, Vega at 26 light years away, but Deneb is an astounding 1425 light years in distance. If it were possible to switch Deneb for the sun, our planet would be toast within a few moments. Deneb produces 54,000 times the energy of our sun each second. Finding the distances to stars allowed astronomers to move these objects mathematically to a standard distance unit so their luminosities could be compared. Deneb is the most distant first magnitude star in the sky. So when Luna is full, look at the moon and the brightest stars. There is still something worthwhile to be seen. Good observing!

1103 OCTOBER 8, 2017: Alone in the Universe? Not Likely!: “The universe is a pretty big place. If it’s just us, seems like an awful waste of space.” That quote from Carl Sagan’s book, Contact, is a good summation of how he probably felt about extraterrestrial life, but keep in mind that Sagan’s opinion was nonscientific because nowhere in our universe except for Earth had self-replicating organisms ever been discovered. However, just like our emergence from the Greek geocentric theory where the cosmos orbited around the Earth, to the heliocentric belief where the sun took center stage, inferential evidence began to mount that Earth’s lone position might not be as singular as originally thought. Galileo saw moons orbiting Jupiter, the phase changes of Venus, a rough lunar surface, and sunspots rotating with the sun as proof that Earth centrists were wrong. James Bradley’s discovery (1728) that our orbital motion minutely changes the direction of light coming from stars, like how walking through rain changes the relative directions of the drops falling from the sky, was the first concrete proof that Earth moved through space; even though by the eighteenth century, all astronomers believed in Copernicus’ heliocentric views. Likewise, the circumstantial evidence is mounting for extraterrestrial life. Take Mars as an example. We recognize that Mars contains a large amount of water ice beneath its surface (Phoenix lander—2008). We know that up to 3.5 billion years ago, Mars was very wet. There were briny oceans, fresh water lakes, and rivers on the Red Planet. We see this in the mapped topography of Mars, but also in the stratified sedimentary rocks and clay deposits that have been photographed and chemically analyzed by past and current rovers. In addition, present day seepage of liquids, most likely water, have been observed numerous times through repeated satellite photography of promising water-produced features. Curiosity, now climbing slowly up the huge central hill in Mars’ Gale Crater, “sniffed” puffs of methane in the Martian atmosphere (December 2014), an indication of possible metabolic processes. The rocks of Gale crater have also yielded organic chemicals (chlorobenzene and dichloroalkanes—March 2015)). In addition, Enceladus and Titan, moons of Saturn; Europa, a moon of Jupiter; and Triton, Uranus’ largest satellite, are all possible candidates for life. In 1838 Friedrich Bessel proved the Copernican theory to be correct by successfully observing the parallax of a nearby star, 61 Cygni, the tiny shift of position created by our Earth’s revolution around the sun and our observations of that star from two different perspectives. Between Bradley and Bessel slightly over a century went by. I think it will be only a few more decades before the same discoveries are made regarding extraterrestrial life. We will, then, no longer be alone in this “pretty big place” called the universe.

1104 OCTOBER 15, 2017: Comet Sneaking Past Capella: “Comets are like cats: they have tails, and they do precisely what they want.” This quote from David H. Levy’s book, Comets: Creators and Destroyers, sums up what can be expected during a cometary apparition. Comets don’t even have to have a tail. Sometimes, there are big surprises, but in most cases, the disappointments win. Comet Kohoutek, discovered on March 7, 1973 by the Czech astronomer, Luboš Kohoutek, ranks most notable. When first witnessed, it was the brightest comet ever seen for its large distance from the sun. Astronomers, extrapolating its brilliance forward to when it would be closest to Sol, expected it to dazzle the evening skies of January 1974. Hyped as the “comet of the century,” some astronomers thought that Kohoutek might become 50 times brighter than the planet Venus, which would share the same part of the sky when the comet was visible. As comets go, Kohoutek was bright, but it was more like 1600 times fainter than Venus, yet still a naked eye object from suburbia. Living in Allentown, I only saw it using binoculars, and for me that was a disappointment. Presently, there is another comet in the sky that has done some unusual things. C/2017 O1 (ASASSN), discovered on July 19 by the All Sky Automated Survey for Supernovae (ASAS-SN) at the Cerro Tololo Inter-American Observatory in northern Chile, underwent a 100-fold increase in brightness shortly after it was found. It has continued to remain about 15 times brighter than predicted, and is now a binocular object (8th magnitude) near the bright star Capella in the evening sky. C/2017 O1 will reach perihelion, its closest distance to the sun, 139 million miles, on October 14. The comet will continue to move nearer to Earth during the next four days, reaching a minimum distance of 67 million miles by October 18. If C/2017 O1 has another upsurge in brightness, similar to the outburst last summer, it will rocket into naked eye visibility. That’s a very big “if,” but because of its proximity to luminous Capella, the sixth brightest star of the nighttime sky, it may just be worth trying to find it. Binoculars will be mandatory unless the comet brightens again. Be outside by 11 p.m. looking towards the northeast. The bright star in that direction will be Capella. On October 10 the comet is within seven degrees of Capella; on the 15th, the angular separation is just over eight degrees. By October 20, the distance has grown to just under 13 degrees. Most common binoculars produce a field of view of about seven degrees. A map with the comet’s changing positions can be located at http://www.astronomy.org/StarWatch/October/index-10-17.html#10-15-17. The distances to several stars from Capella in Auriga the Charioteer have also been noted to help to judge the angular separation of the comet while making observations. View around 11 p.m. for greatest map accuracy. Much success!

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OCTOBER 22, 2017: Andromeda Worthy

For a few days it seemed as if fall was in the air. The skies cleared, and my students finally saw the stars under a moonless firmament from the Sky Deck on top of the Collier Hall of Science and from Shooting Star Farm, east of Hellertown. From the Sky Deck it is possible to determine the basic framework of constellations formed by brighter luminaries. Students can count about 75 stars from center city Bethlehem, but from Shooting Star Farm, at least 10 times that amount can be witnessed with the Milky Way straddling as least half of the sky. On a good night at Shooting Star Farm, especially in the fall, the Andromeda Galaxy can be viewed with the unaided eye as a fuzzy patch of light. Its distance is about 2.5 million light years, the farthest that the human eye can peer into space. In other words, traveling on a light beam at 186,000 miles per second, the ultimate speed limit of our universe, it would require 2.5 million years to reach this assemblage of about 600 billion stars. To see whether your site is Andromeda worthy, go outside at about 10 p.m. on a crisp, fall evening and look due south. Vaulting upward about three-quarters of the distance from the horizon to the zenith will be found the four stars that compose the body of a great horse. They form a square, the Great Square of Pegasus the Flying Horse. The steed transits the heavens upside down, so it will be the star to the upper left in the square that will be of most interest, Alpheratz, where what appears to be the “back legs” of the horse are joined to his body. The “back legs” sweep away from Pegasus’ body in two large arcs, the bottom curve brighter than the top. They are not actually legs at all, but rather Andromeda, the daughter of Cassiopeia, the eventual wife of Perseus the Hero. You are now ready to find the Andromeda Galaxy. Using binoculars if you have them, jump from the middle star of the lower arc to the middle star of the upper arc of stars that create Andromeda. Again, as far up, will be another star that is always binocular from center city Bethlehem and suburbia. Right next to it will be a small football-shaped, fuzzy patch of light, the Great Galaxy in Andromeda. Find a locator map for the Andromeda Galaxy at http://www.astronomy.org/StarWatch/October/index-10-17.html#10-21-17. If you can see it with the unaided eye from where you live, your observing location will be “Andromeda worthy,” a wonderful place to view the nighttime heavens.

By using this map it should easy to locate the Andromeda Galaxy with binoculars from a rural or suburban location. Gary A. Becker map using Software Bisque’s, The Sky.

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OCTOBER 29, 2017: All Hallows’ Eve

Many years ago, I had the pleasure of eavesdropping on a conversation between two of my Allen students. One was trying to persuade the other to visit a haunted house in New Jersey, near Philadelphia, where 20 dollars offered an individual access to 20 “floors” of horror. Each level survived netted the participant a dollar in return, but according to the persuader, no one had ever made it past floor 18. Contemplating death and terror for most of us is something to avoid, yet each year at the very end of October, we celebrate Halloween, a sort of “nose thumbing” to our successful efforts in eluding the Grim Reaper for yet another year. All Hallows’ Eve, October 31, has its roots steeped in astronomy, just like Groundhog Day, February 2, and May Day, May 1. They fall on what are called cross-quarter days, approximately at the midpoints between the four seasonal markers of the sun each year: the winter solstice (low sun), the vernal equinox (mid-sun position), the summer solstice (high sun), and the autumnal equinox (mid-sun again). If you think about it, the cross-quarter day of October 31 is an excellent time to celebrate our vanquishing of death for yet another year. The comfortable period of summer warmth and abundant light is well beyond us. Our focus upon darkness and the cold of an encroaching winter season overwhelms our psyches as the sun treks lower in our daily noontime sky, rising later each morning and setting earlier each evening. Leave it to the pastoral Celts to have envisioned the harvest festival, Samhain (sa-win), meaning summer’s end, and the Gaels (also Celts) of present-day Ireland and southwest Scotland to add a touch of the macabre to this celebration. They believed that the veil separating the worlds of the living and the dead thinned on Halloween permitting the creatures of the netherworld—the souls of the dead, ghosts, fairies, and demons to move freely about our world. Sacrifices of animals and plants were made to the deceased, and bonfires were lit to help to guide these ghouls along their paths and keep the departed separated from the living. Offerings of food and drink were left outdoors to appease and persuade these creatures from entering homes. Later people dressed in costumes, performed tricks and antics on others to receive a treat, thus ushering in our more modern ritual of “trick or treating.” The response of the Church to these popular frolics was to usher in the more serious All Saints’ Day on November 1 and All Souls’ Day on the 2nd; but in the end, Christianity was unsuccessful in ending Halloween, the night of the living dead. Happy All Hallows’ Eve to everyone!