Guest Voices: Archeoastronomical Sites in Africa

Our guest post this week is by J. Craig Wheeler, Yanagisawa Regents Professor of Astronomy at The University of Texas at Austin and former president of the American Astronomical Society.

Like ancient people everywhere, Africans looked in wonder at the sky and struggled to make sense of it. Evidence that they did so with creativity and insight has been slow to permeate academic studies of archeoastronomy and wider public understanding. There is evidence in myths and calendars, but more concretely in ancient megalith observatories.

6500 year old Megalith at Nabta in Southern Egypt. Photo courtesy of F. Wendorf.

Nabta Playa in southern Egypt is the oldest known astronomical site in the world. It was created some 6500 years ago, 5000 years before Stonehenge. The circle of standing stones allowed the Neolithic people to determine when the solstices and rainy seasons occurred. Monstrous stones, some more than 9 feet tall, were dragged for more than a mile to construct Nabta. For three weeks before and after a solstice, the standing stones would have cast no shadow in the noonday sun, due to their proximity to the equator. There is an east-west sighting among the megaliths, as well as a north-south lineup. There have been several other alignments found, but their significance is yet to be determined.

The megaliths of Ng’amoritung’a stand on the shores of Lake Turkana in Kenya. There are 20 peculiar polygonal basalt columns that are of order 2000 years old. While there is some controversy, there are suggestions of possible alignments of nineteen of the twenty stones with seven stars and constellations popularly used for astronomical purposes; Triangulum, the Pleiades, Aldebaran, Bellatrix, Central Orion, Saiph, and Sirius.

Jens Finke at the 2000 year old site of Ng'amoritung'a on the shore of Lake Turkana in Kenya. Photo by Maria Helena Barreira.

Many current treatises on archeoastronomy discuss the wonderful Mayan cosmology and evidence for paleoastronomy in Europe and elsewhere, but make little or no mention of ancient astronomy in Africa. Given the evidence of Nabta Playa and Ng’amoritung’a, it seems very likely that other evidence for the ancient astronomy of Africa awaits in other places, to be discovered with proper care and attention by the people of Africa.

Astronomy in Africa- News and Updates

Photo of Richat structure as taken from space Credit: NASA/ESA

• Last week, South Africa’s KAT-7 telescope reached a milestone by producing the first atomic hydrogen spectral line images of a nearby galaxy. Hydrogen gas emits radio emission in a spectral line (the light given off at a specific frequency by an atom or molecule) at a very specific frequency. “Observations of the neutral hydrogen content of galaxies help to form a picture of how galaxies have evolved over cosmic time and show how our own galaxy, the spiral galaxy called the Milky Way, has developed,” said SKA Director Bernie Fanaroff. KAT-7 (Karoo Area Telescope) is a 7-dish working prototype of the planned 64-dish MeerKAT radiotelescope. When built, MeerKAT will be the most sensitive centimetre- wavelength radio telescope in the southern hemisphere.

• An astronaut currently aboard the International Space Station– which recently flew over the Sahara desert– has taken an image of the Richat structure in Mauritania. This structure, a geological formation in the Maur Adrar Desert, forms a conspicuous bull’s-eye in the desert, making it a frequent sighting by astronauts.

Cosmic Connections

Bedu moon mask, Nafana, Ivory Coast, mid 20th century (National Museum of African Art collection)

Soul washer's disc, Akan, Ghana, late 19th- early 20th century (National Museum of African Art collection)

                            

Guest Voices: Bird Navigation by the Stars

Our guest post this week is by Emily Murgia, Education Programs Specialist with the Friends of the National Zoo.

For centuries of travel, man has looked to the skies for guidance and direction.  But we’re not the only ones.  Studies show that birds, too, use stars to find their way.

Bird migration is the seasonal movement of birds.  Birds migrate to find food or to breed, and may travel long distances to do so. But whether the trip is long or short, it is not so much the destination but the journey.  How exactly do birds know how to get from point A to point B?

Migrating shorebirds

Migratory birds use a variety of cues to know where to go.  For example, some use prevailing wind patterns.  Wind patterns are seasonal, so birds can travel with the wind to reach their destination.  Some birds use landmarks in the form of topographic features (i.e. coastlines, rivers, mountain ranges) to navigate.  Others may use the small grains of a mineral called magnetite that can be found just above their nostrils.  Like a compass, these minerals react to the Earth’s magnetic field and can tell the bird which direction is true north.  Day fliers, on the other hand, use the sun and its position in the sky to tell direction, utilizing the setting sun to identify west.

Then there are the night fliers.  Along with a combination of the methods described above, these birds also use the stars to navigate.

Indigo bunting

The indigo bunting, a small songbird of North America’s east coast, is one such star gazer.  Having studied the indigo bunting, scientists have determined that birds start to learn the star patterns around the North Star starting at a very young age.  Having memorized the constellations that surround this reliable due north icon, birds can migrate at night.

Birds learn the constellations at a young age; those birds that are unable to observe the stars early on are then unable to migrate successfully.  Not seeing the stars is becoming a problem late in a bird’s life, as well.  As cities grow, so does their light emittance.  Light pollution is clouding the skies and is creating dangerous mazes of reflective glass buildings for the birds to navigate.

Birds all over the world are experiencing difficulties migrating.  Along with light pollution, habitat destruction is affecting the birds’ ability to travel, limiting feeding and resting space, as well as homes.  The Smithsonian’s Migratory Bird Center is doing its part to “foster greater understanding, appreciation, and protection” for migrating birds.

The National Zoo is home to many African birds.  Come visit us in DC to see hornbills, pygmy falcons, cranes, and more!  Help us build our African animals a new home and get some new neighbors! Learn more by visiting with our African Animal Ambassadors on weekends in May or visiting our website to find out how you can help.

Astronomy in Africa- News and Updates

Artist's impression of the SKA dishes. Credit: SPDO/TDP/DRAO/Swinburne Astronomy Productions.

• The current news dominating conversations in astronomy across Africa is the recommendation for South Africa to host the Square Kilometre Array over Australia. The Square Kilometre Array (SKA) will be the world’s largest and most sensitive radio telescope, addressing a wide range of fundamental questions in physics, astrophysics, cosmology and astrobiology. It will comprise thousands of radio wave receptors (antennas) and will extend out to distances of 3,000 km from a central core region. The recommendation, made by the SKA Site Advisory Committee, is not yet final- meetings will be held this week to write comments to support the recommendation, which will inform the final decision of where SKA will be located.

• The European Parliament has recently called for greater collaboration with Africa in the field of radio astronomy. The southern African sky has the advantage of low levels of radio frequency interference, and very little light pollution. Judith Sargentini, a Vice-Chair for Delegation for relations with South Africa: “In adopting this Written Declaration, Europe’s elected representatives have sent a strong message to their fellow policymakers about the future of European cooperation with Africa. They have recognised that radio astronomy has a bright future in Africa and that Europe can play a valuable role in it.”

Exploring the Cosmos

Welcome! As we inch closer to the June 20 opening of African Cosmos: Stellar Arts, Cosmos Diary will serve as a space to explore the meaning the cosmos holds for various cultures past and present, and to discover the rich astronomical knowledge found in artistic traditions across Africa.

Look for weekly posts highlighting current astronomy news and research coming out of Africa and showcasing select artworks to be featured in the exhibition. In addition, we’ll feature regular guest posts from artists to astronomers discussing the subject of cultural astronomy and the various ways in which African science, art, and cultural expression intersect.

Take a moment to observe the main image of this blog- an untitled work from a series titled “Zulu” by contemporary South African artist Gavin Jantjes. This painting of the “Zulu” series–“zulu” meaning sky or heavens– refers to the Khoi San peoples’ myth that recounts how a girl dancing around an evening fire threw glowing embers into the night sky, where they remained as a wide, shimmering pathway illuminating the celestial firmament – the Milky Way.

What do you find yourself imagining as you look toward the sky?