The Backyard Astronomer

June 2021
Mars, Cancer, and the Beehive Cluster

For the past couple of months the scientific community has been intently focused on Mars. 

M44 by Stuart Heggie, NASA-JPL

Every 26 months our planets align in a way that shortens travel time from Earth to Mars to about nine months, and as more countries develop space programs, more robotic explorers are sent to the red planet during this window. In 2021 the UAE orbiter Hope arrived on February 9, China’s Tianwen-1 entered orbit on February 10, and the NASA Perseverance rover touched down on February 18. 

Perseverance carried with it the Ingenuity helicopter, which has spent the last month proving the first powered flight on another world, and on May 14 Tianwen-1 released the Zhurong rover, making China only the second country to successfully land a rover on the Martian surface.

Mars by Joel Cohen


Mars is easily identifiable with the naked eye, its deep red hue due to high levels of oxidized iron in its crust. Basically the whole planet has rusted over the last couple billion years.

The arrivals of the orbiters and landers in February signaled a (relatively) close approach of our two planets. For most of 2021 they have been moving farther from one another, making Mars lower and dimmer in our night sky.

Sinking closer to the setting sun, Mars enters the constellation Cancer on June 8. As the month wanes, you may be able to catch one last conjunction with Mars passing just 0.5 arc-minutes from the Beehive Cluster M44 on June 23, just minutes after sunset, low in the western sky.

The Beehive Cluster – Messier 44 – is one of the nearest open clusters to Earth. Ptolemy referred to it as the “nebulous mass in the breast of Cancer,” proving how easily identifiable it is with the naked eye. Galileo resolved 40 stars within the cluster, though we now count at least 1,000 stars spread across 39 light-years, close enough to be gravitationally bound with one another. At least three exoplanets are known to orbit stars within the Beehive Cluster.

If you are lucky enough to catch the conjunction of this open cluster and our neighboring planet, both should easily fit within the field of view of your telescope or binoculars. With the right magnification, one can resolve some nebulosity from the Beehive Cluster and the Martian polar ice cap.

May 2021
Scorpius, Antares, and Globular Clusters

A quick moral mythology: Orion felt that he was such a great hunter that he once boasted to Artemis, goddess of the Wilderness, that he would kill every animal on earth. Rightfully unsettled by this proclamation, Artemis sent a scorpion to kill Orion before he could make good on his claim. The ensuing battle was epic.

Till Credner, allthesky.com

Zeus, observing all of this from on high, snatched up the two duelists and placed them in the sky as a lesson to mortals forever to curb their pride. It is also said that Orion now hunts across the heavens for the winter months but is chased away every spring by the return of the scorpion.

M4 by Jeff Stillman

As we enter the spring months of 2021, the scorpion is again rising in the eastern sky. This constellation consists of 18 main stars, one clearly outshining the rest. Antares is the 15th-brightest star in the sky, often called the “rival of Mars” from its visibly red hue.

A wide-field view with binoculars reveals a unique ball of light just 1.3 degrees west of Antares, known as Messier 4. M4 is a globular cluster, which initially will appear as a fuzzy cotton ball covering a swath of sky about the size of the Moon.

M4 was the first globular cluster to have individual stars resolved by astronomers in the 18th century. Having spent more than 250 years analyzing this dense gravity well, we now estimate over 20,000 stars are packed into an area just 27 light-years across. 

Once you locate M4 with your wide-field view, switch to a telescope or more magnifying eyepiece and you will begin to resolve some of the outlying stars and see how densely packed the center of this cluster truly is.

From M4, move slightly northwest to find another globular cluster. Messier 80 contains several hundred thousand stars spread across approximately 95 light-years. Despite having many more stars, M80 is less visible through binoculars due to its distance, at 3,200 light-years, as opposed to the much closer M4 at 7,200.

April 2021
The Whirlpool Galaxy

As early telescopes developed beyond Galileo’s rudimentary first models, astronomers around the globe began to make astonishing revelations.

Joel Cohen

Charles Messier initially began sketching and cataloging anything that was not a comet using a four-inch refracting telescope, adopting the Latin word for “cloud,” which he used to classify his objects as either a star cluster or “nebula.” He documented Messier 51 in 1773 as one of these first 110 objects. William Parsons again observed M51 in 1845 with a 72-inch reflecting telescope, resolving what he dubbed the first spiral nebula. His 1845 drawing clearly defines what we now know to be a spiral galaxy, however it was not until the 1920s that Edwin Hubble, using the 100-inch Hooker telescope at Mount Wilson Observatory in Los Angeles, proved that our Milky Way was just one of an untold number of galaxies spinning through the cosmos.

Sketch by William Parsons, 1845

Modern astronomers now use the relationship of M51 and neighboring NGC 5195 to study how galaxies interact. Due to its near-constant observation, three recent supernovae have been observed in M51, in 1994, 2011, and 2019. Just in September 2020 a potential exoplanet was detected in M51 using the eclipsing-transit method for observing distant stars. If confirmed, this would be the first planet discovered outside our galaxy. By way of comparison, all the current exoplanetary candidates in the Milky Way galaxy are within a radial distance of no more than 25,000 light-years. The candidate in the Whirlpool Galaxy is 31 million light-years distant.

Today many amateur astronomers enjoy M51 or the Whirlpool Galaxy as a good place to learn how to hop from star to star in search of other objects in the sky. The basic spiral structure of the galaxy can be seen with a good pair of binoculars or small telescope, and is relatively easy to find through much of the year. Start at the Big Dipper, locating the last two stars in the handle. Moving southwest 3.5 degrees at a near right angle, the Whirlpool Galaxy and its companion galaxy are unmistakable, first as an elongated fuzzy gray ball, then resolving in greater detail with larger scopes.


March 2021
The Northern Equinox

Beginning, middle or end, depending on how you look at it

About 90% of Earth’s population lives in the Northern Hemisphere, so many of our astronomical traditions relate directly to how the sun, moon, and stars move across the northern night skies and northern weather patterns.

A prime example of this is the northern equinox, which we most commonly refer to as the spring or vernal equinox, although if one resides south of the equator, it’s more correctly the fall or autumnal equinox. On this day the center of the sun is directly perpendicular to the equator.

Derived from the Latin aequus (“equal”) and nox (“night”), March 20 and September 23 represent the two points in the year that most closely approximate equal times of day and night across the planet.

Ancient cultures did not recognize the exact angle of the sun relative to the center of the earth, but rather that the sun would rise and set directly east and west. The equinox also became a date for the beginning of many annual calendars and subsequent regional festivals.

The Persian and Indian calendars both begin on the day of or day immediately following the northern equinox, and are still used today in their respective countries. The Babylonians began their calendar on the first new moon following the March equinox, celebrating the return of the goddess Inanna from the underworld. The Jewish Passover and Christian Easter are both calculated based on the first full moon after the vernal equinox. 

The equinox is a perfect time to do home science projects. You can wake up with the sun and measure for yourself the exact hours of daylight. Find a local sundial (Sharlot Hall Museum!) or make one yourself, align it using a compass to magnetic north, and find what the solar time is at your home.

Last but not least, maybe we can bring back broom-balancing and pretend it’s real science!


February 2021
Monoceros and the Christmas Tree Cluster

The hollow between Orion, Canis Major (the Great Dog) and Gemini (the Twins) is a relatively dark area. Though the stars are difficult to see with the naked eye due to modern light pollution, in this void is a less-known and relatively modern constellation.

Image courtesy Joel Cohen, Prescott Valley 2021

Monoceros – ‘mono’ meaning ’one’ and ‘ceros’ meaning ‘horn,’ or the Unicorn — is a simple seven-point constellation, though only two of the stars are usually discernible without the aid of binoculars or telescope. Dutch mapmaker Petrus Plancius first noted the Unicorn in 1612, with others following through the 17th century. With better telescopes William Herschel studied the area in 1781, becoming the first to discover that Beta Monocerotis, the brightest of the constellation’s stars, is actually three separate entities, observed as a curved line of pale blue-yellow stars. He later described this triple-star system as “one of the most beautiful sights in the heavens.”

Using a telescope to starhop around the dark areas among these constellations, you can find a slew of other heavenly surprises. The Rosette Nebula (NGC 2244) is known for its ring shape and dense nebulosity. The open cluster Messier 50 and NGC 2506 will appear as fuzzy cotton balls in the smallest apertures, and larger scopes can begin to define many close stars.The real highlight of Monoceros, though, is NGC 2264, the Cone Nebula. Appearing as though a celestial bowling ball was thrust down a foggy lane, parting the fog around  it, a dark cone imparts densely defined edges to a large diffusion of nebulous clouds. At 2,600 light-years distant it is one of the closer nebulae to Earth, and covers a large swath of space with star-forming elements to create its stellar nursery. Along with the Fox Fur Nebula, this diffuse nebula is often referred to as the Christmas Tree Cluster due to its triangular shape with a star at the apex.

Take your binoculars or telescope out and start at the bright star Betelgeuse in Orion, exploring the area just below and down to the Hunter’s belt. As you scan the sky, moving downward toward the Beta Monocerotis triple-star system, you’ll be surprised at what you find.


January 2021
Eclipses

What do you call it when 

     the Moon is directly between the Earth and the Sun? — a solar eclipse.

     the Earth is directly between the Moon and the Sun? — a lunar eclipse.

      the Sun is directly between the Earth and the Moon? — an apocalypse!

The word ‘eclipse’ stems from the Greek ekleipsis, meaning, “failure to appear.” Between two and five times each year the Sun fails to appear, either partially or in full, due to the orbital mechanics of Earth, Sun and Moon. As the Earth swings around the Sun and the Moon spins around the Earth, their orbits periodically line up to where they are on a direct line, causing the Moon’s shadow to cover a small portion of the Earth’s surface.

“Small” is a relative term here, as we experienced on August 21, 2017, when the shadow of the Moon traversed from the Pacific northwest to the southeast United States. Where the shadow completely blocks out light from the sun, we call it ‘totality.’ While the path of totality in 2017 covered thousands of miles and amazed millions of onlookers, we know that the Earth’s surface is mostly uninhabited, covered by dense forest, vast desert, frozen tundra or open ocean. So many eclipses go unseen, able to cross thousands ofmiles of the Pacific Ocean with few if any human viewers.

Eclipse-chasers from around the world reserve hotels and campsites years in advance to get views of these rare events.

In central Yavapai County we were able to observe a partial eclipse in 2017, with the Moon covering at most 76% of the Sun. Sometimes we see partial eclipses where the Moon is slightly farther from Earth in its orbit, causing it to block out the center of the Sun, leaving a ring of light around the Moon. This is called an annular eclipse, such as that seen at the Grand Canyon on May 20, 2012. Also called a Ring of Fire eclipse, these events make for great images, but only with the proper equipment — even the small ring of light radiating from the Sun can damage your eyes. The next annular eclipse visible in our area will come on October 14, 2023.

Just a few months later, a total solar eclipse will once again grace the skies of North America on April 8, 2024. The path of totality will cross Mexico and Texas, continuing over much of the Midwest and almost directly over Indianapolis and Buffalo, then on to northern Maine.

Should you want to travel for a view of totality, book your reservations now! Eclipse-chasers from around the world reserve hotels and campsites years in advance to get views of these rare events. If you don’t intend to travel, mark your calendar to keep an eye out for local events to celebrate with amateur astronomers and skywatchers locally.

December 2020
Orion

We know the holiday season is upon us when strands of color light the night. 

Homes, businesses, pets and even an iconic tree along the highway are all adorned with lights representing hues across the spectrum.

At home the celebratory scenes carry over from outside to inside, blanketing every room of our house.  We love this time of year and the joy we receive from all the lights and colors around our community.

One can enjoy these splendid colors gracing the night any time of the year, just by looking to the heavens.  The constellation Orion is full of colors, though you might need a pair of binoculars or a small telescope to define some of them. Deep red/oranges and bright blue/whites are all easily discernible against the inky backdrop.

The easiest grouping of stars to find is the belt of The Hunter. Three stars in a nearly straight line rise almost vertically above the eastern horizon each evening. Just to the lower right of the bottom star in the belt is The Hunter’s sword, a cluster of three more stars that contain the Orion Nebula. Even the smallest viewing instruments can begin the resolve the beautiful colors of this hydrogen-rich star nursery 1,300 light years from earth. Larger and more advanced scopes will often photograph this nebula with various filters to accentuate the variety of elements comprising this massive cloud of star dust.

Working around the perimeter of the constellation, the left shoulder of Orion is Betelgeuse, one of the largest stars visible to the naked eye, apparent by the bright red hues it emits. Continuing clockwise around the belt are Bellatrix, Rigel, and Saiph, each with a cool blue-white tone.

Varying in distance from about 250 to over 2,000 light years, the stars in the Orion constellation give the amateur astronomer the perfect opportunity to learn their new equipment and the sky. Take a few evenings this month and use different eyepieces to look at the stars and nebulae in Orion. There are three nebulae and multiple double-star systems, How many can you find?