I associate April evenings with the arrival in the ENE of the bright orange star Arcturus, in the constellation Bootes, the Herdsman. A red giant, Arcturus is the fourth brightest star in the entire night sky. It’s 37 light years away — the light you see tonight is what Arcturus looked like in 1984.

Arcturus is Greek for ‘Guardian of the Bear,’ the ‘Bear’ being the neighboring constellation, Ursa Major (Latin for ‘Great Bear’). A curve following the tail of Ursa Major passes through Arcturus and leads to Spica, the brightest star in Virgo, the second largest constellation in the heavens.

Extending the curve of the tail of the Big Dipper (left center) down and to the right takes you to Arcturus (the bright star, just above the junipers). The faint constellation Coma Berenices is at right center.

During the entire month of April, for an hour or so after darkness falls, the Zodiacal Light is faintly visible in the west. The Zodiacal Light is sunlight reflecting off of small interplanetary particles.

The springtime Zodiacal Light is the thin cone of light in the middle of the photo, angling slightly to the left and reaching up to the Pleiades star cluster (just left of center). The springtime Zodiacal Light is difficult to see from our communities because there’s significant light pollution from the Santa Fe area, the Penitentiary of New Mexico, and the Albuquerque area.

April Planets:

Mars continues to fade as it moves to the opposite side of its orbit, as seen from Earth. During April, it’s visible in the west as it moves from Taurus into Gemini.

Mars (top, left of center) threads the needle between the Pleiades (above and to the right of the partially obscured Moon) and the Hyades (left of center) star clusters. The International Space Station (the white streak to the left) almost occults first magnitude Aldebaran.

At the end of April, Mercury begins to climb out of strong evening twilight, becoming an easy evening object in May.

Just below Mercury in the twilight glare, Venus has also moved to the east of the Sun. It, too, will become an easy evening object, beginning in May.

Jupiter and Saturn are now morning objects, rising before dawn in the constellation Capricorn.

April Spotlight:

Coma Berenices is a constellation few pay attention to – it has no bright stars; it’s not on the ecliptic, so no planets pass through it; and there’s no pattern to its stars, unlike neighboring Leo’s lionesque profile. Yet, since moving to Santa Fe, Coma Berenices has become one of my favorite constellations.

The constellation looks like a faint sprinkle of stardust and our dark skies make Coma Berenices easy to see and appreciate — the constellation’s practically invisible in suburban and urban settings.

A satellite in high Earth orbit passes through the Coma Star Cluster in the constellation Coma Berenices.

The reason Coma Berenices looks to some like an open star cluster is because part of the constellation is one. The Coma Star Cluster consists of about 40 stars, located in the northwest part of the constellation. The cluster is relatively close to our solar system, so the stars appear spread out, even to the unaided eye.

More importantly to astronomers, Coma Berenices is home to a large cluster of galaxies, known as the Coma Cluster. With over 1,000 galaxies, the Coma Cluster, along with the Leo Cluster, comprise the Coma Supercluster of galaxies. So, this seemingly barren part of the sky is chock-full of deep sky objects.

Until about 2,000 years ago, the stars comprising current day Coma Berenices were considered part of the constellation Leo. Coma Berenices was first recognized as a constellation in its own right in the 1500s. It’s the only modern-day constellation named for a historical figure: Berenice II.

Berenice II married Ptolemy III, becoming Queen of Egypt in 246 BC. The Egyptian people worshipped Berenice II as a goddess – she was considered the protector of sailors, helping them avoid fatal shipwrecks.

When Ptolemy III went to battle in the Third Syrian War, Berenice II said that if her husband safely returned, she’d cut off her long tresses as a votive offering. She placed her cut tresses in a temple, only to learn that her hair had disappeared by the following day. Ptolemy III’s court astronomer claimed that the goddess Aphrodite had placed the tresses in the sky, in honor of Berenice II’s ‘sacrifice’ (My wife recently cut my hair; the birds used my cut tresses as nesting material. As of last night, there were no new constellations).

One aboriginal tribe in Australia described the asterism we call Coma Berenices as a ‘small flock of birds drinking rainwater from a puddle in the crotch of a tree.’ Personally, I like that better than the royal hair story.

April Night Sky Events:

April 11: New moon.

April 14: This is the last evening to view the Zodiacal Light before moonlight interferes for two weeks.

April 22-23: The Lyrid meteor shower peaks on the night of the 22nd and morning of the 23rd. Under optimal conditions, about 20 meteors per hour can be seen. Some shower meteors are known as ‘Lyrid fireballs’ for their brightness and the lingering trains they leave in their wakes.

A Lyrid drops straight down toward the pre-dawn horizon, appearing to just miss Jupiter. Saturn is to the left of Jupiter; Mars is near the left edge. The center of the Milky Way galaxy is on the right side of the photo.

April 26: As the Sun sets, a full supermoon rises in the east, in the constellation Virgo. A supermoon is a full moon occurring when the Moon is closest to the Earth. It’s slightly larger than an average full moon.

The March 28th full moon was a borderline supermoon.

April 30: See if you can find Mercury and Venus setting in the WNW during twilight.

There’s a new kind of pollution showing up in our night skies and it’s getting worse.

Just a few years ago, when I saw an occasional streak of light on a photo of the night sky, my initial presumption was that it was a meteor. Now, I see streaks on many night sky photos and I assume they’re satellites in Earth orbit.

A dozen satellites photo-bombed this image of the Milky Way.

Satellites are critical to modern life. They provide communications and internet access; they collect data to forecast the weather and climate; they observe changes in the Earth’s surface; they provide navigation aid; and they help keep our country safe, to name but a few examples.

The biggest and brightest satellite in Earth orbit (excluding the Moon) is the International Space Station (ISS), the only satellite with humans aboard. Under the right conditions (i.e., the level of darkness and the optimal angle of reflection between the Sun, the ISS, and the observer), the ISS is the brightest object in the night sky, with the exception of the Moon.

The International Space Station (lower right) and an Iridium communication satellite (top center) bracket the Andromeda Galaxy (center). The Iridium satellite flared when sunlight hit its door-sized solar panel. Satellites appear as slowly moving ‘stars,’ but show as lines on this time exposure photo. The constellation Cassiopeia is at the left; the Double Cluster of Perseus is at lower left.

Satellites used to be so expensive to launch into Earth orbit that only governments had the resources to do it. However, through competition with private industry, launch costs have significantly decreased and the number of satellites in orbit is now increasing at an alarming rate. Consider the following statistics:

  • There are approximately 5,000 stars in the night sky that can be seen with the naked eye. About 2,000 of these can be seen at any given time, the other 3,000 being below the horizon.
  • According to n2yo.com, a site that tracks satellites, there are over 6,000 satellites in Earth orbit and the number increases every year. About half of these satellites are no longer operational (these estimates exclude classified satellites, whose numbers are unknown).

It’s worth noting that, in the last three years, SpaceX has launched over 1,000 Starlink communication satellites into Earth orbit. These Starlinks are placed into orbit in groups that look like satellite trains, slowly and silently drifting as they follow one another across the sky. They’re quite beautiful to see, but they’re becoming a real nuisance to astronomers and astrophotographers. I applaud the efforts made to make Starlink satellites less visible, but the camera still sees what the unaided eye may miss.

A ‘train’ of a dozen Starlink communication satellites cross the Double Cluster of Perseus. The satellites look like slowly drifting stars that seem to follow one another, but appear as lines on this time exposure photo. I believe that the satellites’ paths don’t overlap because the Earth is rotating beneath them. Note the two other satellites traveling in a different orbit that appear to intersect with the Starlink train toward the bottom left (their proximity is a matter of perspective).

In addition to satellites, there’s a lot of ‘space junk’ up there (e.g., spent rocket boosters). The website n2yo.com is currently tracking more than 22,000 objects in Earth orbit. That number, too, grows annually.

It’s true that some satellites are too faint to be seen and, because most satellites are in low Earth orbit and shine by reflected sunlight, they’re mostly seen for an hour or two after dark and before dawn. But, as the sheer number of satellites and pieces of space debris increase, satellites will soon be placed in higher orbits – resulting in more satellites, seen for longer periods of time. Euroconsult estimates that, within seven years, there will be 15,000 satellites in Earth orbit. That’s a ratio of three satellites to every one visible star – think about that.

The US Commerce Department has the authority to regulate American satellites. If something isn’t done to better regulate the number of satellites and make them less reflective, we’ll soon have a situation in which the night sky is in perpetual motion – observing this night sky of the near future will be like having a psychedelic LSD trip without the LSD! And I thought airplanes were the bane of astrophotographers…

However, proper satellite regulation will be difficult to achieve because the US is not the only country placing satellites in orbit — there are almost 100 countries or partnerships capable of launching satellites today.

I’m not ‘anti-satellite,’ I know they’re beneficial to humankind. But, at least paint them black or make them non-reflective, so they aren’t visible. Three satellites for every visible star will destroy our night skies. And while the number of visible stars in the sky is constant during our lifetime (ignoring the effects of light pollution), the number of satellites will eventually increase beyond the projected 15,000. We could end up with a satellite to star ratio of 5:1 or even 10:1. Where do we draw the line? Do we wait until the satellite trains become runaway trains?

One last point – ‘what goes up, must come down.’ Satellite orbits eventually decay, causing them to fall back to Earth. Gravity wins every time. Do we want 15,000 satellites raining down upon Earth over a period of years? Granted, 70% of the Earth is covered by water, so only 4,500 of the 15,000 should hit land (OK, some portion of these might completely burn up upon re-entry). Satellite re-entry is one of the reasons all satellites and space debris are continuously monitored.

Nobody’s been hurt by a falling satellite (yet). But, the odds increase as we launch more and more satellites over our heads.

I’m in no way suggesting that Save The Night Sky 285 take on satellite-related issues. Organizations like the United Nations Office For Outer Space Affairs and the US Commerce Department, as well as advocacy groups like the Union of Concerned Scientists exist to grapple with these challenges.

But, if something doesn’t change real soon, it may be time for me and others to get a new hobby!

The Zodiacal Light is a faint cone of light, sometimes seen in the west for an hour or so after dark. It can also appear in the east, about an hour before dawn. According to Encyclopedia Britannica, the Zodiacal Light can best be seen in the west during February and March and in the east in September and October.

This faint glow is sunlight from below the horizon reflecting off of small particles orbiting the Sun in the plane of the ecliptic (the path against the stars that the Sun appears to follow as the Earth orbits it). The Zodiacal Light is visible around the time of the spring and autumnal equinoxes, when the ecliptic is at a steep angle with respect to the horizon.

Since the Zodiacal Light is quite faint, it can only be viewed on clear, dark nights. From the 285 corridor, the pre-dawn Zodiacal Light is easily visible since our eastern skies are quite dark. However, seeing the Zodiacal Light in the west after dark has become increasingly difficult in our area, primarily due to the light dome from the greater Albuquerque area and the bright lights of the prison.

While various resources indicate that the pre-dawn Zodiacal Light is visible in ‘September and October’ or ‘near the autumnal equinox,’ I’ve viewed it from my home in Eldorado as early as the latter half of June and as late as mid-January.


Pre-dawn Zodiacal Light, as seen from Galisteo on June 30, 2020. Note how the Zodiacal Light presents a shallow angle to the horizon since it’s 12 weeks shy of the autumnal equinox. Venus is the bright ‘star’ on the horizon, just left of center and below the Pleiades star cluster.

The pre-dawn Zodiacal Light, photographed from Eldorado on January 17, 2021. You can see the upper half of Scorpius and first magnitude Antares above the horizon in the center of the photo.

Currently, the Zodiacal Light is conveniently located in the western sky, just after dark. See if you can view it, despite the nearby light pollution. I saw and photographed it this week.


The evening Zodiacal Light in the WNW, shining up between the light dome of the greater Albuquerque area (left) and the prison lights (right). The photo was taken just after dark on March 7. The angle of the Zodiacal Light is steep since the Spring Equinox is only two weeks away. Note that the evening Zodiacal Light leans toward the left, while the pre-dawn Zodiacal Light, shown in the earlier photos, leans toward the right. In both instances, the Zodiacal Light follows the angle of the ecliptic.

We need to protect our dark skies, so we can continue to see this ghostly interplanetary light.

Mercury-Jupiter Conjunction of Friday March 5, 202

Eric Saltmarsh


If you went outside just after dawn on Friday, you were treated to a close conjunction of the planets Mercury and Jupiter, in the constellation Capricorn. The planets rose together in the ESE about 5:15am MST.

On that morning, Mercury and Jupiter were separated by only 0.6 degrees. Jupiter, at magnitude -2.0, is the brighter planet, with dimmer Mercury at magnitude 0.6. Saturn, magnitude 0.7, is also in the vicinity, to the pair’s upper right.

If you look for these planets on more than one morning, notice how quickly Mercury and Jupiter appear to converge before conjunction, then separate afterward. Mercury is the real speedster here since, by virtue of its proximity to the Sun, it has a much higher orbital speed than distant, sluggish Jupiter.

These relationships are explained by Johannes Kepler’s three laws of planetary motion, published early in the 17thcentury:

  1. The orbit of a planet is an ellipse, with the Sun at one of the two foci.
  2. A line segment joining a planet and the Sun sweeps out equal areas during equal intervals of time.
  3. The square of a planet’s orbital period is proportional to the cube of the length of the semi-major axis of its orbit.

Cutting to the chase, Kepler’s laws confirm that planets orbiting closer to the Sun travel faster than planets farther from the Sun.

In the case of Mercury and Jupiter, Mercury, the innermost planet, travels around the Sun at 107,000 miles per hour versus Jupiter’s 29,000 miles per hour. Mercury’s orbit is much smaller than Jupiter’s, as well. Since a year is the time it takes a planet to complete one revolution around the Sun, a year on Mercury is equivalent to 88 Earth-days. A year on Jupiter is equivalent to 11.9 Earth-years.

Mercury & Jupiter, Tuesday March 2
Mercury & Jupiter, Tuesday March 2

Mercury & Jupiter, Wednesday March 3
Mercury & Jupiter, Wednesday March 3

Both phots were taken at the same time. Jupiter is higher on the 3rd because it rises earlier each day. Mercury looks like it hasn’t moved in the last 24 hours, but in actuality, it has reduced its apparent distance from Jupiter by one-third.

 

 

Take-Aways

  • Bright or high color temperature outdoor night lighting threatens bird health and safety
  • The AMA warns that outdoor night lighting with color temperature greater than 3000 K is a danger to people, too
  • Street lights that are no brighter than necessary, and has color temperature less than 3000 K, is safest for birds and people

Streetlights and Wildlife

Tom Jervis, President, Sangre de Cristo Audubon Society


In the 21st century, we are accustomed to think of light as something that happens when you flip a switch.  But as recently as 100 years ago, artificial light was something that limited and dim.  It was not until after the Second World War that the technology to generate vast quantities of electrical energy and transform that into astonishing levels of illumination, among other social benefits, became widespread. With the recent advent of inexpensive and highly efficient light-emitting diode (LED) technology, our capability to bring very high illumination levels took a great leap forward.

Wildlife evolved to live with the natural day-night cycle and seasonal variation in that pattern. Most living things, including humans and many plants, are exquisitely tuned to these circadian rhythms by internal clocks that keep our body processes functioning properly.

Modern LED technology, particularly high color-temperature (blueish) lighting, has created a serious problem for wildlife beyond that already created by our sprawl into areas not previously affected buy our civilization. There are two issues with area lighting such as streetlights. The first is the intensity of illumination and how well it is directed to those places where it is wanted and needed. LED lighting is generally better directed than the commonly used light fixtures of the recent past and it is easier to control to prevent “trespass light” going where it is not needed. Because it is so efficient, however, it is too easy to create a glare problem both for humans and for wildlife if direct and reflected light are too intense.  The second issue with LED lighting has to do with the color temperature of the light. LEDs come in color temperatures from about 1000 K to 10.000 K or more.  The higher the temperature, the more blueish the light is; the lower the temperature the more yellow to red it is. Note that this is independent of the intensity—usually measured in lux (lumens per square foot)—of the illumination.

Macaw. c. Sam Finn

 

For wildlife, particularly birds and insects, the problem is compounded by the color temperature of the lighting. Birds and insects “see” in the ultraviolet (UV) and high-color temperature lights contain significant UV light. Lights of any kind disturb the day-night rhythm that animals expect, but the intense blueish light of high temperature LEDs amplifies the effects.

Wood Duck. c. Sam Finn

Research has shown that blueish light from high color temperature LEDs is particularly disturbing to birds, many of whom migrate at night, navigating by the stars and Moon. They are confused by overly-bright lights, disrupting their migration patterns and causing them to be “trapped’ by these lights until they collapse from exhaustion. Higher levels of light pollution were associated with more species during migration—evidence that light pollution attracts migratory birds to cities across the U.S. Research has also found that cities contained the greatest numbers of migratory bird species during spring and autumn migration.  This is cause for concern, as it shows that the influence of light pollution on migratory behavior is strong[i].

Research in Germany on the Blue Tit, a chickadee-like bird, has demonstrated that artificial lighting results in the males starting to sing earlier in the morning, and that  females start to build their nests earlier in the season. The researchers also documented disruption in the mating behavior of the birds, resulting in more “extra pair” matings[ii].

Insects are also attracted to light, more so by light with a high UV content. Research has shown that populations of insects living near to artificial lights include more predator and scavenger species than populations living in similar, but darker, conditions. This shift can affect the survival rates of different species and have effects on birds and mammals that feed on those species. Interestingly, the effects were seen during the day, as well as at night, so these population shifts are ongoing[iii]. Mammals, many of whom are nocturnal, so bright artificial lighting, particularly high color-temperature LED lighting, is bad for them as well, disrupting their circadian rhythms, their foraging and hunting behaviors, and their ability to avoid predators[iv].

Ruby-crown Kinglet. c Tom Taylor
Ruby-crown Kinglet. c Tom Taylor

 

Finally, the American Medical Association (AMA) issued a rare warning and guidelines on how communities can choose LED streetlights to “minimize potential harmful human health and environmental effects.”[v] The AMA’s statement recommends that outdoor lighting at night, particularly street lighting, should have a color temperature of no greater than 3000 Kelvin (K).

So high levels of lighting, particularly UV-rich LED lights, is bad for animals disrupting the behaviors which evolution has prepared them for life in the world. But at the same time, we need artificial lighting for the protection of public health, safety, and security. Fortunately, there are solutions.  The same technology that produces UV-rich and overly bright lights also makes it possible to make lights at a lower color-temperature with more than adequate intensity for public purposes. In a review of artificial lighting for the National Park Service[vi], the authors concluded that for the particular case of roadway lighting, that “Where light is essential, fixtures should be full cutoff and shielded to minimize glare from any non- road site …. The best overall choice for spectrum is probably yellow (e.g., low-pressure sodium or yellow/amber LED).”

The choice is ours to make.  We can have the social benefits of artificial lighting with minimal disruption of the natural world if we choose the right lighting source. Low color temperature LEDs provide public safety and security and are efficient and low-cost to operate. That is the path we should take.

Dig Deeper!

[1] Cities can help migrating birds on their way by planting more trees and turning lights off at night, <https://theconversation.com/cities-can-help-migrating-birds-on-their-way-by-planting-more-trees-and-turning-lights-off-at-night-152573>.

[2] Artificial night lighting affects dawn song, extra-pair siring success and lay date in songbirds, Bart Kempenaers, Pernilla Borgström, Peter Loës, Emmi Schlicht and Mihai Valcu, Current Biology, 20 1735, 2010.

[3] Street lighting changes the composition of invertebrate communities: Thomas W. Davies, Jonathan Bennie, and Kevin J. Gaston; Biology Letters, Volume 8, Issue 5, 23 May 2010.

[4] Ecological Consequences of Artificial Night Lighting. Catherine Rich & Travis Longcore (eds). 2006. Island Press. Covelo, California. Pages 15-42. http://www.urbanwildlands.org/ecanlbook.html.

[5] http://www.ama-assn.org/ama/pub/news/news/2016/2016-06-14-community-guidance-street-lighting.page.

[6] Artificial Night Lighting and Protected Lands : Ecological Effects and Management Approaches, Travis Longcore and Catherine Rich, Natural Resource Report NPS/NRSS/NSNS/NRR—2017/1493, National Park Service, Fort Collins, Colorado.

 

 

Mars & The Pleiades
Mars (lower left) passing beneath the Pleiades in Taurus on March 1, 2021

This week, Mars, ‘the Red Planet,’ is making a close passage beneath the Pleiades star cluster. It will be 17 years before Mars and the Pleiades hook up again, so take a moment and check this out while they’re still close together. You can find Mars and the Pleiades just past overhead as darkness falls. They set in the WNW around midnight.

Currently, Mars shines at magnitude 0.9, not nearly as bright as it was at opposition last fall. But, its reddish-yellow color creates a fine contrast with the blue stars of the Pleiades.

About 450 light-years away, the Pleiades (a.k.a., the Seven Sisters) is the closest open star cluster to our solar system. There are 1,000 to 3,000 stars in this dipper-shaped cluster. The stars of the cluster are less than 100 million years old and are considered to be of intermediate age. The brightest stars are hot blue stars, however, most of the Pleiades are faint stars at the red end of the spectrum.

Faint wisps of reflection nebulae, like blue cirrus clouds, seem to surround the brightest stars in the cluster. The nebulae is believed to be unrelated to the cluster, the stars just passing through the dust clouds as they travel together through space. A small telescope or camera-mounted star-tracker is needed to photograph the nebulae

The Pleiades in Mythology

Ancient stories of the Pleiades abound. In Greek mythology, the Pleiades are the seven daughters of the titan Atlas and the sea-nymph Pleione.

In one version of the myth, these seven sisters committed suicide when their father, Atlas, was eternally doomed to shouldering the heavens, as punishment for his part in the ‘Battle of the Gods,’ a decade-long war for control of the universe, fought between the titans or old gods and the new Olympian gods (the Olympian gods won).

After Atlas was forever occupied holding up the sky, the hunter Orion pursued each of his daughters. Zeus, the Sky god and head of all gods on Mount Olympus, placed the Seven Sisters in the sky to keep Orion at bay. Zeus then placed Orion in the sky, where the hunter chases in vain the seven daughters of Atlas across the firmament (unbeknownst to the ancient Greeks, the Pleiades star cluster is moving toward Orion!).

According to one Native American tale, seven young Kiowa women were surrounded by bears. Appealing to the Great Spirit, the ground beneath the women’s feet began to rise, freeing them from their predators. The bears clawed at the new cliffs beneath the flat-topped ground where the women safely resided. As the bears gouged the sides of the cliffs, the ground rose higher, pushing the women into the sky as stars. The butte where the women were saved from the bears is now known as Devils Tower, located in northeastern Wyoming.

In India, the stars are known as Krittika, the six mothers of the six-faced war god, Murugan. To the Japanese, the star cluster is known as ‘Subaru,’ which means clustering or unifying.

In the Lascaux Caves in southwestern France, an ancient pictograph portrays the Pleiades as a six-starred dipper cluster in the shoulder of a bull (Taurus). This rock painting is estimated to be 17,000 years old.

Mars and the Pleiades This Week

Mars will be slightly closer to the Pleiades over the next two nights, making its closest approach on Wednesday (March 3). The planet will then move away from the cluster as it heads for neighboring Gemini.

No optical aid is necessary to view Mars and the Pleiades, although binoculars will help. It’s best to view this spectacle shortly after dark, before Mars and the Pleiades descend into the glare of the prison lights and the light dome of Santa Fe and communities just to the north.

Mars (lower left) and the Pleiades (upper right) on March 1, 2021. The star trails, due to the length of exposure, help show the color contrast between reddish-yellow Mars and the blue stars in the cluster. Reflection nebulae can barely be discerned, especially near the star, Merope (the lower left star in the ‘dipper’).