StarWatch: Moravian College Astronomy

MAY 2021

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

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lunar phases

1289 MAY 2, 2021: Where are the Planets?: I was thinking about Jupiter and Saturn the other day, and the beautiful Christmas pageant they enacted when they dramatized some of the more visual aspects of the Star of Bethlehem to people all over the world. Jupiter approached Saturn within six minutes of arc, 1/10 of a degree, on December 21 of last year. Lehigh Valley skies were cloudy on the 21st and the 22nd, but the evening of December 23 was clear enough to see and photograph the conjunction. A few weeks later, the sun caught up to the widening pair, and they disappeared from sight for over a month. • The winter dragged on, the sun moving eastward about one degree each day, and the two planets continued to separate in the morning sky with faster orbiting Jupiter gaining a wider lead. • This week, the pair can be found about 15 degrees apart, low in the southeast at 4:30 a.m. They are now far enough from the sun to be seen in a dark sky. If you view on Monday morning, May 3, you will see a nearly third quarter moon approaching Saturn. At third quarter the moon is half on, half off with the sun’s light to the left. The following morning, May 4, a fat waning crescent moon forms a near equilateral triangle below Jupiter and Saturn. By Wednesday, the moon trails Jupiter, close to the SSE horizon by 4:30 a.m. If you are out and about, look high in the east, and you’ll also get a good look at my favorite asterism of the high sun months, the Great Summer Triangle, composed of three bright stars, which in order of their apparent brightness are Vega, Altair, and Deneb. Vega and Altair are relatively close to us at 25 and 16 light years respectively, but the faintest luminary, Deneb, is the real powerhouse of the group. At roughly 1600 light years distant, Deneb shines with an approximate luminosity of 67,000 suns. • After sundown the west showcases the three other planets that can be viewed without optical aid—Mercury, Venus, and Mars, although Venus will be better placed in a couple of weeks. Wait until Tuesday, May 4, and be at your observing location 45 minutes after sundown for a very interesting gathering of Mercury and the Pleiades (Seven Sisters). Use binoculars if you want to see the much fainter Pleiades. Their separation will be two degrees or four lunar diameters, and located seven degrees above the horizon, about one binocular field of view. • Mercury and a razor thin crescent moon tangle with each other on Thursday, May 13. At the same time, Mars will lie at the feet of Castor, the fainter of the two stars that represent the heads of the Gemini Twins. A better chance to catch Mars will be on May 15 when the God of War lies not quite 2.5 degrees from the crescent moon. Two days later on May 17, Mercury reaches its greatest eastern elongation from the sun. Afterwards, the Messenger God begins to slide backwards, sideswiping Venus (less than one half degree apart) very near to the WNW horizon on May 28 as it heads back towards the sun. The pair will be one binocular field of view above the horizon 30 minutes after sundown. Mercury is positioned between the Earth and sun on June 11. All of the naked eye planets are waiting to be discovered in the morning and the evening sky throughout the month of May. Keep looking up this spring. Ad Astra!

1290

MAY 9, 2021: Extraterrestrial: Avi Loeb

When it comes to alien life, there are three types of people: those who disbelieve it outright, those who concede intelligent life can exist elsewhere in the universe, and those who believe extraterrestrial life has made its presence known on Earth already. • I concede that I am of the third type, and I have been for decades before the media hype turned my position into something ludicrous. Apparently, I have received some vindication from the former chair of the Harvard Astronomy Department, Avi Loeb, who wrote Extraterrestrial, Houghton Mifflin Harcourt Publishing Company, 2021, regarding a peculiar event that started on October 19, 2017. Telescopic images from Haleakala Observatory in Hawaii showed an anomalous object that immediately caught the attention of astronomers. • If you saw the discovery on a photograph, you would not be impressed, but the research that surrounded this sighting catapulted Loeb into his startling conclusions. Everyone agreed that because of its hyperbolic orbit, this interloper was not of this world or solar system. It was an interstellar traveler. The observed object, seen from over 20 million miles distant, had an “elongated disk, was highly reflective, showed no signs of outgassing that might be expected with the discovery of a new comet or even an asteroid, and it deviated from its calculated orbital path.” • The object was named Oumuamua, Hawaiian for “scout,” which left me wondering for whom was it scouting? • With regards to what was seen on the telescopic images from Haleakala Observatory in Hawaii, there were anomalies: an extrasolar visitor passing through our solar system, on its way to realms unknown, the first of its kind ever discovered. • The scientific community won’t say it is a piece of extraterrestrial technology even though that is a possible interpretation. They concluded that Oumuamua was peculiar, maybe an exotic comet, but just a naturally occurring “interstellar” visitor that deviated from its trajectory in some unexplained fashion. • Loeb postures that taking into consideration all of its peculiarities, “there is roughly a one in a trillion chance that Oumuamua was simply a unique rock.” Still with all of the observational data favoring alien technology, Loeb concedes that although it may be just a “rock,” he is critical of mainstream astronomers who refuse to include the possibility of an extraterrestrial interpretation. • To me, the odd pattern of the trajectory was the statement that made me pause. As Loeb points out, it would be difficult not to compare it with the objects we have launched into space, like the Pioneer and Voyager spacecrafts. Then too, if Oumuamua is truly of alien origin, it opens a whole new Pandora’s box of questions—uncomfortable ones for some. Humanity may not take kindly to lose its self-derived, unique status in the cosmos. The book makes me wonder. What does a flyby accomplish? To gather information naturally; to learn, to grow, “to go where no one has gone before…” • I hope a benign civilization would have such positive aims. Regardless, Earth has already alerted the nearest hundred plus light years of space surrounding it with radio and TV transmissions. Perhaps some extraterrestrial civilization has gotten the message about us and are “phoning home” right now about their latest observations.

1291 MAY 16, 2021: A Primer on the Life Cycle of Our Sun: We call the sun an average star, but it is really more on the brighter side than average. It will be powering itself for 11 billion years by spontaneously changing the simplest element, hydrogen, into helium deep within its Earth-sized core. • Born in an open cluster of stars 4.6 billion years ago, Sol was most likely the second generation of stars created within that grouping. The sun was conceived from a denser knot of gas and dust collected after the energy from the earliest stars began cleaning out “the nest” with their overpowering energy production. In the dust and gas cloud that would give birth to our sun, gravity contracted the mass. In the center, the protosun was hidden from sight by blankets of dust, becoming denser and hotter until temperatures reached about 16 million degrees Fahrenheit (9 million Kelvin), and hydrogen spontaneously began to be fused into helium • The fusion of hydrogen was uneven at first, producing great bursts of energy, followed by relative periods of quiescence. When the sun was active, the leftover grains of dust were heated and melted; the gases pushed away, setting the stage for the accretion of the planets. • However, what happened to the open cluster to which the sun was associated? It did not possess enough mass for the gravity of the system to hold itself together. Gradually over hundreds of millions of years, it evaporated, the outer members wandering away from the cluster, causing the remaining stars to drift ever farther away from each other until Sol found itself orphaned, alone in its 250-million-year passage around the Milky Way Galaxy. For probably the last 4.3 billion years, the sun, planets, dwarf planets, moons, and the other bits and pieces of matter that the sun dragged along with it have been silently and uneventfully orbiting the galaxy. • The sun began its hydrogen burning existence as a smaller but slightly hotter star with about 30 percent less luminosity. This means that when life began on our planet, perhaps as early as four billion years ago, it had to struggle with an atmosphere devoid of oxygen and much colder than it is today. • During the last four eons, helium has been squeezed into the sun’s core, causing it to become hotter, our daystar to become larger, cooler on its surface, but slightly more luminous, producing the temperate conditions we experience today. This natural warming trend will continue for another five to six billion years, causing conditions on Earth to heat until in about one billion years, Earth will experience a runaway greenhouse effect when the oceans boil and force sentient life to explore and colonize new worlds. • When the sun’s core finally runs out of hydrogen, thermonuclear fusion will shift to a thin shell surrounding the core. Because of its increased energy production, Sol will rapidly grow larger, its outer layers cooled through the expansion process, but overwhelmed by the increase in its surface area, making the sun into a more luminous, red giant star for a billion years or so. As hydrogen becomes depleted in the sun’s energy producing shell, Sol’s vitality will begin to oscillate wildly, eventually culminating in a burst of energy that will drive its outer layers into space, creating a planetary nebula with the hot, inert core of the sun exposed, now a white dwarf, slowly cooling for eternity in the depths of space as it circles the galaxy. There is no happy ending to this story, so enjoy the sun while you’ve got it, a middle-aged star still brimming with life-giving warmth.

1292 MAY 23, 2021: The Lunar Eclipse You Won’t See: We are so close and yet so far away from seeing the total lunar eclipse which will grace the Pacific Ocean skies this May 26. Hawaii will be the most favored location, while the East Coast is the least preferred area for observing any part of this event. • To be eclipsed means to be hidden. A solar eclipse occurs when Sol, the sun, is hidden from view by the moon. These types of eclipses must always occur during the day and at the time of a new moon. A lunar eclipse has the full moon hiding in the shadow of the Earth. This can only happen at night. • The problem with the May 26 lunar eclipse is that because of the diminished darkness of summer, night will be turning into day everywhere in the continental US before the eclipse ends. • Why am I so disappointed? Although there must be at least two lunar eclipses occurring each year, and there can be as many as five, not all circumstances will favor your location for viewing it as is the case for the May 26 event. And then, of course, there is the weather which is not foreseeable until a few days before the event. • Many years ago, I remember one student boastfully comment to my class that once you had seen one lunar eclipse, then you had seen them all. There was no need to waste your time to see another. Nothing could be further from the truth. When the moon becomes totally immersed in the Earth’s shadow, the small amount of sunlight that is reaching the moon’s surface must be refracted (bent) into Earth’s shadow by the atmosphere before it can reach the moon. That light is coming from all of the places around the globe where the sun is either rising or setting. The atmospheric transparency in these locations will determine the amount of color and brightness of the lunar eclipse. It is also the location where the atmosphere reddens the sun’s light the most, creating similar colors on the moon. At the location where the boundary of the Earth’s shadow is closest to the moon, colors can change into oranges, yellows, white, and even blues. Pollutants, particularly those that reach into the stratosphere of Earth’s atmosphere, above seven miles in midlatitudes, can dramatically affect how the eclipse will look. As an example, the moon literally disappeared at the time of totality during the December 9, 1992 total lunar eclipse. Exposures of several seconds that normally reveal beautiful images highlighting the varying colors falling onto the moon’s surface were lengthened to several minutes. When I got my film back from processing (before the digital revolution), the lunar northern hemisphere was still very underexposed, but the southern hemisphere looked fine. The lighting effects produced on the moon were the product of the intense volcanic eruption of Mt. Pinatubo on June 12, 1991, the second most violent explosion of the twentieth century. That single event ejected more than 2.4 cubic miles of ash as high as 22 miles above the Earth’s surface, well into the stratosphere. • The recent lunar eclipses that I have seen have been colorful and bright, nothing like the 1992 event, so to have a total lunar eclipse right at your doorstep and not witness it depresses me. We will just have to wait until November 19 when a deep partial lunar eclipse will be visible across the continental US, and at a time that will allow us to witness the entire event; that is unless you’d like to travel to Hawaii for this one. Ad Astra!

1293 MAY 30, 2021: Spooky Eclipse Sunrise: Get ready for a weird sunrise on June 10. That’s because Sol will be covered by a good portion of the moon at that time. In eastern PA about 75 percent of the sun will be gone. This is more coverage for us than the 2017 total solar eclipse which crossed the country from Oregon to South Carolina; however, for most of the country it will be a nonevent. Nowhere on Earth will observers see the moon completely covering the sun; so all the subdued lighting effects which make total solar eclipses so overwhelming will be missing. Still, seeing that much of the sun obscured is an exciting experience if you have never had the opportunity of witnessing any type of solar eclipse. • What makes our location so special is that Sol rises near maximum coverage, and may create a scimitar looking sun in addition to all of the other atmospheric effects which accompany a sunrise. The problem with our location is that observers need a flawless ENE horizon to capture all of the optical and atmospheric effects. Moving eastward to Montauk Point, New York or to Boston, Massachusetts allows observers to catch the sun at a higher altitude at maximum coverage, but the sun rises less eclipsed. Going westward causes the sun to rise later after maximum coverage. • The reason that I am hyping this partial eclipse is because I saw a similar event on August 11, 1999 from the Schoodic Peninsula (Acadia National Park) in Maine. I was scheduled to escort a group of umbraphiles to the Black Sea to observe a total solar eclipse, but the Balkans War had heated up again. Most of our tour members cancelled which put a kibosh on the trip for my wife and me, but there was a lemon to lemonade aspect to this story. A friend of mine, Ben Walter, an eclectic marine biologist, who owns an exclusive bed and breakfast, Oceanside Meadows Inn, near the Schoodic Peninsula, asked if I would speak about this eclipse to guests at his Summer Institute for the Arts and Sciences which he hosted each year. This eclipse was total at sunrise just 170 miles to the east of Schoodic which meant that the sun would rise over the waters of Down East Maine nearly eclipsed with about 95 percent of the sun missing. Ben even investigated chartering a plane to rendezvous with the moon’s shadow at sunrise. He found one, Martha Steward’s private jet—she was summering in Bar Harbor—but her asking price of around $7,000 per person nixed that idea. • I scouted out a beautiful sunrise location the day before the eclipse under perfectly clear skies. My eclipse presentation was delivered that same evening highlighting the solar eclipses that had occurred over Ben’s 1820 barn where the presentation was given. All participants received special eclipse glasses to view the event safely • E-day found my wife and me and several dozen eclipse participants on Blueberry Hill in Acadia National Park under a completely gray, cloudy sky except for a sliver of clear horizon in the northeast. Dawn looked very normal, but as the sun approached the horizon, more and more of it was becoming hidden by the moon, creating colorful clouds bathed in reds and lavenders. At sunrise the portion of the sun not blocked by the moon looked like a flattened scimitar climbing out of the Atlantic waters, a real showstopper. • I doubt if the June 10 sunrise eclipse will be as outstanding because less of the sun will be covered, but southeastern Pennsylvania is in the best position for a repeat of the 1999 event. Next week, I’ll write about safe solar observing techniques. You can see pictures of the 1999 partial solar eclipse in Maine below.