Lunar Lunacy

Next Wednesday (January 31) the world will be treated to a trio of rare lunar occurrences, all at the same time. A blue moon, super moon, and total lunar eclipse all fall on the same date. What are all of these? Let’s break it down one item at a time.

Humans love to name things, and a blue moon is simply when a second full moon happens in a single calendar month. Our first full moon was on New Year’s Day, which in itself is one of those rare events that people seem to think means something. Sometimes the moon actually does appear to be blue, but that is usually due to atmospheric issues like pollution.

A super moon is when the moon reaches its closest approach to Earth (the moon’s perigee). Our orbit around the sun isn’t round, it’s slightly elongated. The moon’s orbit of us is the same. When the moon is near or at perigee, it appears slightly larger than usual. It’s barely even noticeable to the human eye.

Diagram showing the moon's elliptical orbit (NASA image)

A lunar eclipse is when the moon passes through Earth’s shadow. This event only happens during a full moon, when the sun fully lights the side of the moon facing Earth. This puts Earth between the sun and moon. A solar eclipse requires a new moon, and places the moon between sun and Earth. During a lunar eclipse, the moon sometimes appears red. It’s also known as a blood moon. Next week we are treated to the rare super blue blood moon. That’s a mouthful!

Diagram showing the sun, earth, and moon positions during
an eclipse (Smithsonian Air and Space Museum)

NASA photo of a blood moon

The best lunar eclipse I’ve ever seen was in 2015. The eclipse began before moonrise, so by the time it came up over Mount Rainier it was already red. This time, I'll get to see it on my way to work, assuming we have clear skies.

Lunar eclipse over Mount Rainier

Partial phase of a lunar eclipse

Species of the Month

January has been a snowy month for me, so it seems fitting that the Species of the Month be equally snowy. A few weeks ago we learned about the snowy owl, but now we’ll look at another white bird from the cold, snowy north- the snow goose.

Scientific name: Anser caerulescens

Kingdom: Animalia (animals)

Class:   Aves (birds)

Order: Anseriformes (ducks, geese, and swans)

Range: Summer range is eastern Arctic Canada and Greenland; winter range is Gulf Coast and Midwest states. They don’t fly nonstop, so there is migratory habitat in between.

Habitat: Tundra, marshes, tide flats, prairies, farmland

Lifespan: 20 years, on average

Diet: Roots, grasses, sedges

Predators: Arctic foxes, jaegers, eagles

Conservation Status: No special conservation status

Other Information: The snow goose has two color morphs, white and dark gray (known as blue goose). Blue goose was originally considered a separate species. Snow geese are a popular game bird. Due to rising populations, they are considered an agricultural pest in some areas. The black mark on the bill is sometimes referred to as lipstick or the grin patch. They mate for life. The female incubates the eggs while the male stands guard over her. They sometimes nest near snowy owls, which may deter predators. Nesting colonies can contain tens of thousands of birds. The snow goose is model for the National Wildlife Refuge System's logo.

National Wildlife Refuge System's logo

This week's information comes from University of Michigan's Animal Diversity Web. Photos are from Missouri Department of Conservation, except the logo.

Snow goose

Blue goose color morph

Thousands of snow geese in flight

Let it Snow

When I was younger, I always wondered why the weatherman could tell us with absolute certainty that it would rain on Thursday, there’d be a thunderstorm at 4:30 on Saturday, and it would be sunny and warm all day Sunday. But when winter sets in there’s snow in the forecast, it was always a lot of “maybe” and “it could”. Now that I’m older and wiser, I can see that a lot of forces are at play when it comes to building a snowflake. What determines whether the weather will be snow, sleet, or just cold rain? Snow requires the right amount of moisture at the right temperature, plus cold enough temperatures from cloud to ground.

Ideally, air temperature should be at least 15̊ F, but not higher than about 40̊ F for it to snow. Warmer air holds more moisture, making it more likely for snow to form, as long as the temperature stays within that narrow threshold.

Part of the uncertainty regarding snow, I think, is my location. All my life I have lived relatively close to the ocean, that great body of temperature-moderating water. The ocean slowly absorbs summer heat, then slowly radiates that stored heat through the winter, keeping the nearby air relatively warm, compared to the middle part of the continent. While it may be cold enough for snow to form in the clouds and stick on the ground, sometimes that warm ocean air forms a layer in between. When that happens, the snow melts and refreezes into sleet pellets or remains liquid rain and freezes on contact with the surface- freezing rain. 

Elevation is one of the factors that matters in predicting precipitation type. Usually, higher elevations are cooler. In my Pennsylvania life that doesn’t matter much, but in Washington it could be the difference between a blizzard and a downpour. There, the snow level (elevation at which snow becomes rain) is a moving target, changing by the day or even hourly. Forecasts from fall through spring frequently mention the snow level, and occasionally it drops to sea level. I once witnessed the spectacle of the snow level moving down the side of a mountain across the road from my cabin. I stood in the rain, waiting for the school bus, as the snow steadily marched downhill. By the time the bus arrived it was snowing where I stood.

Today's snow information comes from the National Snow and Ice Data Center. That nifty chart up above is from Weather Wiz Kids. And don't forget to follow Nature Minute on Facebook if you haven't already.

Snowy Owl Irruption

If you happen to see a white owl flying around, odds are you haven’t been accepted to Hogwarts. This winter, the northern US is being treated to a snowy owl irruption. What’s an irruption? It’s a sudden population increase followed by a mass dispersal.

Snowy owls typically inhabit the Arctic: northern Canada, Alaska, even Russia and Scandinavia. When there is abundant prey, there is more reproduction and higher offspring survival. That population increase makes things a little crowded though. When the young are ready to fledge the nest, they will migrate farther than usual from home in order to establish their own territories. Established owls, feeling the pinch, might also spread out. The higher the population, the farther they fly to get away from other owls. 

Snowy owls are used to open, treeless areas in the Arctic
(US Fish and Wildlife Service)

Areas that don’t normally see snowy owls are reporting a sudden influx. Depending on where, just two or three owls might count as a sudden influx. New York, New Jersey, and Michigan are just a few of the places that I know of that getting these visitors from the Great White North.

I thought about driving to the Jersey shore to try my luck at finding the snowbird recently seen at Island Beach State Park. Reason quickly returned, as I decided against spending hours waiting in bitter cold temperatures for something that might not happen. I don’t expect good odds of seeing one at home with. During the week, I waste my daylight at work and on weekends it’s been too cold to leave the house. Unlike snowy owls, I prefer a warmer climate. 
This week's information comes from the Audubon Society and UM's Animal Diversity Web.

Snowy owl in flight (US Fish and Wildlife Service)

Snowy owl I found in Washington (in captivity at Northwest Trek)

Star of Wonder

Science is very good at explaining things and can even solve a mystery that has no remaining witnesses. Science is able to tell us how long ago a frozen cave man lived, and even how he died. One mystery that science has been unable to explain, but has offered many possible solutions to, is the Star of Bethlehem that the Magi followed. The star is mentioned in the gospels, and many biblical events have been confirmed by archaeology. But is the star a legend, a myth, a miracle, or something perfectly logical?

There are several astronomical phenomena that could explain the star. People at the time were very astute when it came to sky watching, as the stars and moon were (and still are) great navigational aids, so anything out of the ordinary appearing in the sky would have been noticed and documented. Some examples of astronomical phenomena that could have occurred on the First Noel include a planetary conjunction, a nova, a supernova, and a comet.

A planetary conjunction is when two or more planets appear very close to each other in the night sky, and may even appear to be a single object. Just such an event- a Jupiter and Saturn conjunction- took place in the year 7 BC, just outside the accepted date of Jesus’s birth (6 BC- 4 BC). The timing is very close and the position in the sky is correct, but the planets were not close enough to appear as a single star and while the conjunction may have led the Magi in the general direction of Bethlehem from Jerusalem, but did not stand over Bethlehem as stated in the Bible. 

Conjunction of Venus and Jupiter, 2015

A nova (“new star”) is star that suddenly flares up many times in magnitude. It is given this term because in most cases, it is a star that ordinarily is not visible to the naked eye. Similar to a nova is a supernova, a star which has exploded. Chinese and Korean records indicate either a nova or supernova occurred in the year 5 BC, which also fits the timeframe for the nativity. Unlike the planets, however, a nova or supernova would remain in a fixed position in the sky. 

Remnants of 1987 supernova (NASA)

A comet is best described as a dirty snowball orbiting the sun. Depending on location and trajectory, they can become visible to the naked eye as they approach the sun. The period of visibility and brightness vary from comet to comet, but as an object in orbit, it would certainly move about the sky. Chinese records indicate a comet appearing in the year 5 BC, which is within the accepted time of Jesus’s birth. The comet’s location in the sky would have it preceding the Magi first to Jerusalem, then to Bethlehem. It even appeared during spring, which is when it is believed he was born, even though we celebrate Christmas in December. That’s a different story for a different blog. 

Comet ISON (NASA)

Over 2000 years later, the great mystery of the Star of Bethlehem may finally have an answer thanks to forensic astronomy and the meticulous records of the Chinese. Was it really a comet, a completely rational cosmic occurrence, which led the Magi to Bethlehem? If so, did divine intervention place the comet where it needed to be at the right time? That question might never be answered.

This week's information comes from two sources. Speculation about conjunctions and comets comes from Colin J. Humphreys and the speculation about novae and supernovae comes from Mark Kidger.