StarWatch: Moravian College Astronomy

APRIL 2021

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1285 APRIL 4, 2021: Rebirth: Spring and rebirth always go hand in hand, so much so, that it is really a cliché that begs for a deeper meaning. We need to examine it further. • For rebirth, there has be a death first. A flower withers in the fall. Ruined gardens, stalks of once lovely plants like our dahlias and daylilies, move me to tears as I witness each fall the beauty of our garden dying with the first frosts and eventually the onslaught of winter. • This rebirth is also mirrored in the universe. Stars also go through life cycles too. They are born in stellar nurseries, large clouds of gas and dust where shock fronts from the death and birth of other stars affects their coalescence. Dependent upon their masses and the subtle, inward nudge of gravity, these protostars begin their journey from youth to decline. Our sun is approaching the middle of its 11-billion year existence, having been formed from the debris of as many as two former massive stars that each flowered, lived out their existences, and then ejected most of their masses back into the universe in fiery supernova events, only to be rekindled into new beacons of thermonuclear light. Our sun will not follow the same evolutionary path as its predecessors. In about five billion years, Sol will begin to expand into a red giant when it depletes its core hydrogen, finally settling into death as a white dwarf, a lifeless hulk of degenerate matter that will continue to cool for trillions of years. Before this happens, the sun in its red giant phase will bequeath back to the universe 30 to 70 percent of its hydrogen to be mixed with the primordial hydrogen of the Big Bang and supernovas to form new stars. More massive stars will go supernova, exploding in huge “fireworks” displays that can be visible to the edge of the universe, seeding their surroundings with all of the naturally occurring elements, the stardust that has allowed for the evolution of you and me. What remains after these titanic detonations are neutron stars and possibly even black holes, so massive, dense, and consumptive, that in the latter not even light can escape. Astronomers can see the remnants of supernovas, white dwarfs, and black holes, as well as evidence for how the demise of these objects represent the precursors for new life, which bring us back to humanity. • The ancient Egyptians believed in resurrection so much so that they prepared tombs for their remains, stocking them full of earthly possessions and even statuary representing the servants which would help them in the afterlife. They saw their existence mirrored in the newness and dying of the day and the seasons. Today, Christians also see a spiritual rebirth as many prepare to celebrate Easter. Those age-old concepts are at play here as 2.4 billion believers celebrate Christ’s entrance into Jerusalem, the Last Supper, His betrayal and death, and finally Christ’s ultimate triumph in His resurrection. The idea of resurrection/rebirth is imbued in our religious traditions, just like it is echoed in the universe. • If a new star can be reborn from the “ashes” of a star that has died, then perhaps we can too. In a way that is what “the resurrection of the body” means, dead to living; the grave is not the end. • That is a hopeful message for the arrival of spring, if you’re a flower, a tree, a star, or a human wondering about the universe from a decidedly unique and bold perspective. From the ashes of death springs new life.

1286

APRIL 11, 2021: The Winter Journey

Decades ago, while perusing the British Museum in London, I came across the last pages of Antarctic explorer, Robert F. Scott’s journal, the final words that he wrote before he froze to death around March 29, 1912. Flanking Scott in his tent were his good friends, Edward Wilson and Henry Bowers. Previously, Lawrence Oates and Edgar Evans had died returning from the Pole. Scott was just 11 miles south of One Ton Depot where abundant supplies were stored for their successful return from the South Pole. • Seven months later, the diary was retrieved by Apsley Cherry-Garrard, the youngest member of the British Antarctic Expedition. Cherry, as his friends called him, wrote The Worst Journey in the World (1922), a vivid and humbling account of the Antarctic expedition of 1910-1913. In it is a chapter called The Winter Journey, where Cherry, Wilson, and Bowers embarked on a five-week trek across the Antarctic ice to retrieve Emperor penguin eggs from a rookery 70-miles distant. The goal was to discover the different stages of embryonic maturation in the eggs. • On June 27, 1911 they departed, three men towing behind them two sledges in tandem with a total weight of 792 pounds. Cherry writes, “It is midday but it is pitchy dark, and it is not warm.” Keep in mind that the seasons are reversed in Antarctica. It was winter. The sun never rose at 78 degrees south latitude during the entire five weeks that they were gone. • It took them 19 days to reach their destination, including a relatively short three-day blizzard in which they were hunkered in their tent. Throughout the outward trek the temperature was seldom warmer than -50 degrees F. During one rest period their thermometer read -77.6 degrees; consequentially, they continually fought against frostbite. The water froze inside of Cherry’s blistered fingertips, creating excruciating pain as he marched. His teeth cracked and broke from chattering. Cherry could not wear his glasses because every exhalation coated his lenses with a thin layer of frost, so in the darkened conditions, he was basically blind. Their beards by the end of a day’s slog were blocks of ice. As they sweated while laboring with the sledges, the moisture was wicked away from their skin only to refreeze in the next layer of fabric, making their garments as stiff as armor. On a warmer night, tucked deep within their reindeer sleeping bags, the ice in their clothing would melt, seeping into their bags. Clothing and bags would then refreeze within 15 seconds after emerging from their warmer tent. It sometimes took them an hour just to reenter their frozen sleeping gear during their next rest period because they had to melt their way into the bags. • They got within two miles of the rookery, pitched their tent, and over a period of several days, constructed a shelter made from stone with a canvas roof. Upon returning from the rookery, the group had to endure another three-day blizzard which destroyed their stone refuge, while blowing away their tent with supplies. Luckily, their tent was recovered a half mile downslope with most of their gear intact. They would have perished without it. Returning, the three staggered into base camp on August 1, 1911. Their frozen clothes had to be cut from their bodies. The moral of this story for me has been, no day, no week, or month could ever be as torturous as The Winter Journey. They recovered five Emperor penguin eggs. Three made it back to England. Photographs are below.

The not so happy British Antarctic Expedition Polar Party reached the South Pole one month after the respected Norwegian explorer Roald Amundsen had planted his country’s flag at the bottom of the world. Left to right Lawrence Oates, Robert Falcon Scott, and Edgar Evans are standing; Henry Bowers and Edward Wilson are sitting. Image by Henry Bowers, January 18, 1912...

Members of the Winter Journey before departure are from left to right, Henry Bowers, Edward Wilson and Apsley Cherry-Garrard.

Left to right, Edward Wilson, Henry Bowers, and Apsley Cherry-Garrard enjoy a meal after returning from the Winter Journey.

Five Emperor penguin eggs were recovered by Winter Journey members. Three were brought back to England. Two eggs were broken in Cherry-Garrard's mittens when he slipped and fell on the ice making his way back to the rock shelter from the rookery.

1287 APRIL 18, 2021: Season of Galaxies: Have you ever noticed that after the brilliant starscapes of winter comes the blandness of spring? The heavens no longer resound with the same beauty as the winter sky. That is because we live in one of the arms of a pancake-shaped spiral galaxy called the Milky Way, and our night views into space change with the seasons. • The Milky Way is about 100,000 light years in diameter, but in our locale, 27,000 light years from the center, its thickness shrinks to roughly 1000 light years in depth. Keep in mind that a light year is equivalent to the distance that light travels in one year. One light year is slightly less than 5.9 trillion miles, a vast distance, but still small compared to the 52 billion light year span of our universe. • The solar system is tipped with respect to our galaxy with the Earth-sun plane, called the ecliptic, tilted at a 60-degree angle to the galactic plane. This creates four distinct views during the year serendipitously in sync with the seasons. During the winter months our nighttime vista of the heavens points us towards the outer regions of the Milky Way, through the Orion arm along the gas and dust rich galactic plane where new star generation is commonplace. Here we observe the dazzling luminaries of Orion the Hunter. They will burn brightly for a mere 10-million years as compared to the 10-billion year expected history of our much fainter sun. Our sun will live 1000 times longer than the stars that compose the outline of the Hunter. Such vivid stars as Betelgeuse and Rigel are just momentary bursts of luminescence when compared to the history of our galaxy and even to the sun. • As the Northern Hemisphere begins to lean towards the sun, Sol has climbed higher into the sky, the days have lengthened, and our orbital location with respect to the galaxy has provided us with new nighttime vistas. As darkness calls, Orion has now retreated into the southwestern corner of the sky and sets about an hour after sundown. A whole new constellation of stars has taken center stage, but these luminaries lack the vibrancy of the winter sky because they are cooler and spaced farther apart from each other. The Earth’s rearward vista is now pointed above the galactic plane into deep space. Because this region is less thick, there is simply less matter, and therefore, less gas, dust, and stars to peer through from a galactic perspective, making spring the optimal time to view faraway galaxies. • The sky is peppered with clusters of them, such as the Virgo, Leo, Coma (Berenices), and Ursa Major clusters. If these galactic assemblages were in the plane of the Milky Way, they would be obscured by the copious amount of dust from untold supernova events that have occurred throughout our galaxy’s 13-billion-year history. So when you gaze skyward in the spring, more photons of light from deep space are reaching your eyes, maybe even some from the Big Bang itself. Spring is the wondrous season for the sighting of galaxies.

1288 APRIL 25, 2021: Leo Roars into Spring: Last week’s StarWatch talked about how the brilliance of the winter heavens has turned into the seemingly blandness of our current spring sky. Our nighttime view into space is no longer positioned towards the dusty, hydrogen rich galactic plane of our Milky Way galaxy, but rather away from it, allowing us to see much deeper into space. Even with a more subdued sky, there are still a few good gems to stimulate an interest in looking up. • One of the best star patterns of the spring season is Leo the Lion, now nearly due south after evening twilight. A backwards question mark known as the Sickle (used for cutting grain) delineates his head and the thick fur of his mane. Leo’s most luminous star, Regulus, as well as the heart of the lion, is placed where the period of the backwards question mark is located. From the Latin it means “the little king,” appropriate for the “king of the beasts.” Leo’s hindquarters are defined by three relatively bright stars Denebola, Zosma, and Chertan which form a triangle. The brightest of the grouping is Denebola, which in Latin translates to “little tail.” Although male lions possess long tails with a tuff of hair at their ends, Leo’s tail and tuff were literally cut off by the Egyptian astronomer, Conon, in order to save himself from execution. Conon had advised Queen Bernice to sacrifice her long beautiful tresses to Venus in order to secure the safe return from battle of her husband, Ptolemy III. Ptolemy returned and Bernice made her sacrifice, but the hair was stolen. When asked to explain under the penalty of death, Conon created from Leo’s tuff, Coma Berenices, the hair of Queen Bernice, right on the spot. • Leo dates back to the earliest days of Egyptian astronomy and is one of the first visual aids. Leo warned people of the presence of lions during the summer. In its annual trek among the stars, the high sun passed close to the luminaries of the Lion, creating according the Egyptians, the overpowering heat of the summer months. What better animal to represent them but the most powerful beast in the world, a lion? • The association goes even further because in Egypt the summer months were considered to be “the time of the lions.” The unrelenting heat drove the dangerous beasts from their hillside lairs into the cooler, more populated Nile River valley. • However, because of the wobbling of the Earth’s axis, a 26,000-year cycle called precession, Leo is no longer the king of the summer sky. Over the millennia, the sun’s yearly position has gradually shifted nearly 60 degrees to the west, so that currently Sol is positioned in Taurus the Bull during June and Gemini in July. • To find Leo, first locate the Big Dipper high in the NNE right after dark. If you follow the two pointer stars, Dubhe and Merak, downward, the North Star will be found. See a star map here. Travel in the opposite direction, and Leo will be bisected. It is as simple as that. You’ll be viewing one of my favorite constellations of the spring and a herald of the warmer weather which will follow. Roar away, Leo! Summer is on track. Ad Astra!