StarWatch: Moravian University Astronomy

JANUARY 2025

JANUARY STAR MAP | MOON PHASE CALENDAR | STARWATCH INDEX | NIGHT SKY NOTEBOOK | EVENING SKY MAP

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lunar phases

1481 JANUARY 5, 2025: Full Moon to Occult Mars on the 13th: Dances are happening among the planets and the moon in the heavens, but we rarely glimpse the best moves. Their motions across the heavens and their inclinations to the plane of the solar system vary enough so that nearly every time they pass each other, one is above or below the other and too far apart to deem the occurrence astronomically significant. However occasionally, their orbital paths cross when they are both present simultaneously, creating an occultation where the moon covers a much smaller planet or star. * Even when an occultation occurs, it is far from a done deal that you can witness the event. That is because the moon is close to us, and the planets are much farther away. Occultations are limited to a relatively small geographic area and are more local events, differing greatly from a lunar eclipse, where everyone on the nighttime side of Earth can view the event. Location is critical because the Earth's 8000-mile diameter can change the moon's position by as much as two degrees. * Then, the Earth's rotation must be considered. The occultation could occur during the day, making it even more difficult or virtually impossible to observe, depending upon the phase of the moon and its location to the sun, or it could be happening on the other side of the Earth during our daytime period. * What if the occultation occurs at 3 a.m.? That's a lovely time to rise and shine from a warm, cozy bed and greet the day. What if it's cloudy, too windy, or bone-numbingly cold? There are at least a dozen excuses for the dance to go unseen, but the occultation in a week (Monday) negates many of them. * The full moon will be occulting Mars, which is currently at its brightest (Magnitude -1.4) in the early evening of January 13. The occultation occurs for Philadelphia at 9:19-13 p.m. That translates to 13 seconds after 9:19 p.m. For my location in southern Lehigh County, the moon begins encroaching upon Mars at 9:19-56 p.m., and for Harrisburg, 9:17-24 p.m. You can go to http://www.lunar-occultations.com/iota/planets/0114mars.htm to discover a city closer to your location for specific times. The link only worked for me if I copied and pasted it into my browser. * It will take about 31 seconds for the moon to occult Mars completely, so part of the enjoyment of watching this event will be witnessing Mars' slow disappearance, which will be very different from a star that winks out instantly when covered by the moon. * You will need some type of optical aid to watch Mars being occulted. A monocular or binoculars will suffice, but a telescope will allow you to scrutinize Mars slowly being covered by the moon. The last time the moon and Mars tangled from the East Coast was December 7, 2022. Watching the moon approach Mars even one hour before the celestial event was challenging. A thin but decreasing cloud layer marred the scene, but when the veil finally lifted, perhaps 30 minutes before the closest approach, I could not see Mars without an optical aid. Visual acuity and the tremendous differences in brightness and contrast between the moon and Mars, over 30,000 times, overwhelmed my eyes making Mars unobservable. * While you are enjoying the moon cuddling up to Mars, Pollux and Castor, the heads of the Gemini Twins, will only be four and eight degrees above Luna, respectively. * For my location, Mars begins reappearing at 10:34-58 from Mare Smythii, a lunar sea along the equator partially visible on the easternmost limb of the moon's near side. It was named for the 19th-century British astronomer and Navy Admiral, Sir William Henry Smyth. Hoping for clear skies and much success in viewing this special event. Ad Astra!

1482

JANUARY 12, 2025: The Paradox of Algol the Demon Star

There is a star in the constellation of Perseus the Hero, Algol, currently visible high in the east by 7 p.m. It was known to the Greeks and Romans as the Demon Star. In Perseus' star pattern, it became the eye of Medusa, the snake-laden head of the Gorgon Monster, lobbed off when Perseus went on his quest to slay her and rid his kingdom of the evil Polydectes, the king of Seriphos. It was a difficult feat because anyone looking into her eyes was immediately changed into stone. On his way home, Perseus used the Medusa's powers to rescue the beautiful Andromeda from the "jaws" of Cetus the Sea Monster by changing him into granite. * This star in ancient times was known to be variable, winking every 2.87 days for about 10 hours, losing 1.3 magnitudes of brightness, an intensity difference of 3.3 times when it bottomed for two hours at minimum illumination. You can track the dimming of this star by visiting the Sky and Telescope magazine link here. Click Initialize to Today and the times of minimum light for Algol will appear displayed in Universal Time for nearly a month. Subtract five hours from UT to obtain Eastern Standard Time or four hours when we are on Eastern Daylight Time. * The strange story about Algol is that it is a triple star system with a luminous B8 main sequence (hydrogen-burning) star about 3.5 times more massive than the sun and 95 times more luminous in the light that the human eye can see. It is orbited every 2.87 days by a dying KIII (giant) luminary, a much cooler yellow-orange star, 4.5 times the sun's luminosity, but with 0.85 the sun's mass. In its main sequence hydrogen burning days, it seems to have been a star similar to our sun, much less massive than the B8 main component of the Algol system which it orbits. The third star plays no role in the story. * The hotter B star has a diameter of 2.9 times that of the sun, while the K giant is 3.5 times Sol's diameter. Algol fades when the larger K-giant partially eclipses the smaller, hotter B star. However, there was a problem with this eclipsing binary system that astronomers immediately realized. * The longevity of a star is a function of its mass, with higher mass luminaries like the B star living a much shorter life than the lower mass dying K giant. Put in another way, as a regular hydrogen-burning star, the K giant should have been around for 10-15 billion years or even longer, while the B star should only have less than one billion years of longevity. And that was the paradox. How could a star possibly as old as the universe itself be in orbit around a star that could not even be a billion years old? * The inconsistency was resolved when it was realized that the cooler K giant must have been originally a more massive and brighter luminary than the B star that it was now orbiting, and the higher mass star would have lived a shorter life as a hydrogen-burning luminary. When the star evolved into a giant, it became so huge that hydrogen was transferred onto the other less massive component, destined to live a much longer life. The original higher-mass star's life was drastically altered as it lost mass, and its temperature and luminosity decreased as the mass transfer continued, allowing the original less massive component to evolve into the more massive B star that we see today. * You can view the dimming of Algol by following my instructions in this blog and then going outside five hours after or before minimum light to see the Demon Star shining more brightly in the nighttime sky. Much success in seeing Algol wink. Ad Astra!

This sequence of images shows the Moon occulting Mars on the evening of January 13, 2025. The disappearance began at 9:18-57 (computer prediction (9:19-56) and continued for approximately 37 second, ending at 9:19-34. I first became aware of Mars'emergence from Mare Smythii at 10:34-25 with the disk of Mars tangent to the lunar limb at 10:34-52 (computer prediction 10:34-58). Conditions were clear, calm, and without frost. Gary A. Becker composite image...

1483 JANUARY 19, 2025: Ready for the Great Planetary Alignment?: The motions of the planets, the sun, and the moon intrigued the ancients, fostering astrology, which used the characteristics of these celestial objects and their positioning to one another to predict the fate of nations, kings, and eventually, the lives of ordinary people. Often when the planets aligned, the soothsayers of the heavens predicted calamitous events, not just ages ago but even in the present. The alignment of planets occurring right now, more aptly should be called a parade or procession. * The misconception surrounding planetary alignments is that the wanderers stack up behind one another, their gravitational attractions wreaking havoc on the poor Earth, particularly causing earthquakes or volcanic eruptions because of their mutual gravitational attractions. More about that in a moment. * From west to east on January 19, right after dark, the planetary ordering from west to east will be Saturn, Venus, Neptune, Uranus, Jupiter, and finally Mars. Remember that you will need binoculars or a small telescope to see Uranus and Neptune, but they will be in the sky. See a map below. I picked the 19th to observe because Venus and Saturn will be only 2.5 degrees apart, which is a nice pairing in binoculars, but the parade will be visible weeks into the future. The angle of separation across the evening sky from the first to the last planet will be just over 128 degrees, a little more than a third of a circle's circumference. If the sun and Mercury are included, the angular distance becomes 168 degrees, nearly half of a circle's circumference. There is no "stacking effect" going on here. * Let's turn to the gravitational effects of a planetary alignment. Undoubtedly, the sun's gravity controls the motions of the planets and all solar system objects that orbit around it. Still, Sol is not the principal contributor to differential gravity, which can cause the crust on opposite sides of a fault to move, creating an earthquake. The best example to explain differential gravity is found in a low mass black hole. Dropping straight into the structure, you would find your feet closer to the singularity of the black hole's center than your head. The gravitational attraction of the singularity would pull harder on your feet than on your head, causing you, as a very unhappy astronaut, rapidly to stretch, a process that was termed spaghettification by the late, wheelchair toting, Stephen Hawking, who had a rather wild sense of humor. * While the force of attraction that keeps Earth in orbit around Sol results from the product of the masses divided by the square of the distance between them, differential gravitation results from the cube of the distance between the two bodies. This squared versus cubed factor of distance creates an incredible enhancement in the ability of nearby objects to have a more significant pulling effect than high-mass objects that are farther away. * Although the moon is only 1/27,000,000 the sun's mass, Luna is about 400 times closer to the Earth than the sun. Completing the math using relative units for mass, the amount of matter an object contains as one for the Earth, and the Earth-sun distance also equaling one yields the tidal effects (differential gravitation) of the moon to be over twice that of the sun. So how could Jupiter, 1/1000th the sun's mass, but at best about four times the sun's distance from the Earth, have any noticeable tidal effect on our planet? It simply cannot, and neither can any of the other planets even if they were stacked one behind the other. Nuclear war, runaway global warming, and a rash of pandemics could cause a global extinction of humanity, but planetary alignments are just not in the stars. To a much greater extent, the moon, followed by the sun, creates the tides that average about three feet in the open oceans and six inches on the land. * More about this planetary parade when the moon enters the scene at the end of next week. Much success in observing the current procession of planets in the evening sky. They are worth seeing. Ad Astra!

1484 JANUARY 26, 2025: