A web exclusive story from Astronomy magazine

Northwest Passages

© Eugenesergeev | Dreamstime
Captain Cook and the Orion Spiral Arm

By Jon Lomberg

In the late 1700s, British explorer James Cook went out in search of the great Northwest Passage. In the process, he made tremendous maps. And now, remarkably, these precise polar maps have proven invaluable in the 21st Century as tools for contemporary scientists studying long-term climate change.

Working with astronomers Jeff Goldstein and Leo Blitz, I made a map of the Milky Way as best we knew it in 1992. That map served as the design basis for a Galaxy Garden that now sits in Captain Cook, Hawaii. Like James Cook and his early maps, my painting and the gardens it has inspired serve as a reminder that our view of the world — and the galaxy — we live in continues to grow and change as our ability to view it improves, year by year.

“The Resolution beating through the Ice, with the Discovery in the most eminent danger in the distance” on 18 August, 1778 off Icy Cape, Alaska — Cook’s farthest journey north. John Webber (1792)

In search of the Northwest Passage

We associate Cook with the islands of the Pacific for many reasons: his 1768 expedition to Tahiti to observe the transit of Venus, his first contact with Hawaii, and his discovery of Australia and Sydney Harbor. But even if he had never visited these happy isles, he would have been ranked as an all-time great navigator, mapmaker and the first great polar scientist.

In 1776, Cook set out to search for the Northwest Passage connecting the Pacific and Atlantic Oceans. If Cook had found an open Northwest Passage, it would have crowned his already illustrious career. But after months battling the sea ice, his ship and crew needed a spot for some R&R. What better spot than Hawaii? Cook did not realize that he was arriving on a miraculous floating island at the beginning of the special season of the god Lono. His evident power and wealth of metal (very rare in Hawaii) confirmed Hawaiians’ suspicions he must be Lono. Nothing was too good for him and his lucky crew. He unwittingly sailed away in his magical ship just as the festival of Lono was ending, further confirming his divine status to the Hawaiians.

Cook’s arrival in Kealakekua Bay, as depicted by John Webber, an artist who traveled with Cook. John Webber (1785)

But sailing down the coast, Cook encountered a great storm and his ship was dismasted. Since the Hawaiians had been so friendly, it seemed natural to return there for repairs. But this was not in the script. From the islanders’ viewpoint, here he comes back, his ship battered and bruised, not godlike at all. They realized he was just a human, a stranger expecting more divine hospitality. The price of pigs and papayas skyrocketed. Tensions grew, culminating in an ugly incident regarding a stolen boat that ended February 14, 1779, with Cook’s death in Kealakekua Bay at the hands of angry islanders. He became one more casualty of the quest for the Northwest Passage.

Unfolding the map

Those contemplating the effects of contact with an advanced extraterrestrial civilization often point to Cook’s fate as a cautionary tale about the difficulties inherent in first contact scenarios, with danger to both sides if intents are misunderstood. Such musings were at one time the merest fantasy. But in recent decades, the Search for Extraterrestrial Intelligence (SETI) has people now thinking of themselves in galactic terms, and we are indeed sending spacecraft — the Pioneers, Voyagers, and New Horizons — beyond the solar system and into the galaxy. What explorations might be taking place right now in the vast stretches of the Milky Way?

I’m a bit of a mapmaker myself, or at least I help others make their maps. As an artist, I have helped astronomers visualize, and thus explore, our Milky Way galaxy. This kind of exploration is far more comfortable than Cook’s, but no less thrilling. We are discovering for the first time the geography of the galaxy we are part of. I wanted to help people understand that fact by providing an explorable model of the Milky Way, a project realized with the creation of a unique piece of floral, astronomical art in 2007.

The Galaxy Garden is the world’s first floral map of the Milky Way. Jon Lomberg

The Galaxy Garden is one of many displays in the Paleaku Peace Gardens, located in Captain Cook, Hawaii. Heidy and Pierre Lesage ©

A few miles from the same Kealakekua Bay where Cook was killed, at the privately owned Paleaku Peace Gardens, is the Galaxy Garden, the worlds’ first large-scale, explorable model of the Milky Way galaxy, mapped as accurately as modern astronomy allows. Different plants represent the stars, dust and nebulae that form our galaxy. Each spotted leaf is a starfield, each flower a glowing nebula. At 100 feet in diameter, the scale of the garden is 1,000 light-years per foot, 83 light-years per inch. Most of the stars we see with the naked eye are on the same leaf as the Sun.

On the scale of the Galaxy Garden, most of our Sun’s nearest neighbors (and the brightest stars in our sky) fall on the same single leaf. Jon Lomberg

Walking along the spiral arms of the Galaxy Garden provides a unique experience of galactic scale and geography.

The Galaxy Garden’s mailing address is, appropriately enough, in Captain Cook, Hawaii. Skilled mapmakers have provided the knowledge based on the most cutting-edge exploration and mapping — but this time not of Earth, but of the vast Milky Way galaxy in which we are a tiny part. (But certainly not an insignificant one — we figured it all out, didn't we? Just as Cook’s tiny expedition mapped the expansive polar ice, our tiny planet is discovering the larger galaxy around us.)

The design of the garden was based on a piece of artwork, a large acrylic on canvas I did on commission for the Smithsonian’s National Air and Space Museum in Washington, D.C., for the gallery “Where Next Columbus?” that was open from 1992 to 2007. That work represented the most accurate map of the Milky Way at the time. The position of the Sun is marked with a small yellow plus symbol.

Not much has changed since then.

Exploring the Galaxy Garden gives a visitor a sense of galactic geography unequalled by any other experience on this planet.

Our spiral arm

Spiral arms are largely visual structures, easily identified by the human eye’s tendency to connect discrete blobs into linear features, (as early astronomers saw the famous but nonexistent canals of Mars by linking dark areas into lines). We can think of the arms as marking the flow in the galaxy’s material, in the same way waves display the flow in the ocean. Areas of star formation follow the spiral density waves that compress the gas as they move around the galaxy, a process I visualized metaphorically in my painting Galactic Wave, inspired by the famous Japanese woodcut by Hokusai, where the breaking waves form new stars as they revolve around the galactic center.

Galactic Wave marries the feel of an ancient Japanese woodcutting with the image of a galaxy as it forms stars. © Jon Lomberg

Sometimes there are little spurs branching off the larger curves. Our solar system is in the Orion Arm, long thought to be a small spur branching off the larger Sagittarius Arm. It was called the Orion “Arm” as a token of respect because we are in it — it is really just a minor feature of a real arm, further demotion of any sense of our cosmic specialness. If you superimpose the standard compass directions onto the painting, where right is east and left is west, the branch point between the Orion and Sagittarius Arms is northwest of the Sun in the galaxy.

In the Galaxy Garden, I put a small bench at the branch point — Philosophers Bench, as it became known — as a spot to look down the length of the short Orion Arm to the rest of the garden and the long slope to the shoreline and ocean horizon. Very contemplative — but not good for traffic flow, since the way in is also the way out. Furthermore, the portion of the Galaxy containing out Solar System is naturally a place of the highest interest to visitors — when you see a group photograph, you look for yourself first — and traffic is heaviest there.

There is certainly no physical barrier at the branch point between arm and spur in the actual galaxy. Gas and stars move freely through it. But in turning our galaxy into a garden, our layout did form a sort of barrier, more like a dead end, in the Sun’s little corner of the Galaxy Garden.

The Galaxy Garden’s Orion Arm shortly after planting (top) and more recently (bottom). © Jon Lomberg

Life mirrors art

The Galaxy Garden has stirred the imagination of many thousands of visitors since it was created in 2007 with generous funding from the Change Happens Foundation, which is also supporting the creation of a new Galaxy Garden at the Delaware AeroSpace Education Foundation (DASEF). And Europe’s first Galaxy Garden is being built next to the Planetarium of Pamplona in Spain. I’ve been working with both projects to adapt the Galaxy Garden to these new locations, built on lessons learned in almost 10 years of operation of the Galaxy Garden in Hawaii.

Remembering the barrier in the first Galaxy Garden, I thought for these new gardens we should consider adding a gap between the Orion and Sagittarius Arms permit the traffic to flow through, with visitors leaving opposite the way they entered. But was that modification glaringly incorrect astronomy or acceptable artistic license?

The author’s daughter points to the single leaf containing the Sun and so many other familiar stars. Jon Lomberg

While pondering this, I got an email from my astronomer collaborator Leo Blitz, with whom I worked on both the Portrait of the Milky Way and the Galaxy Garden. Our mapping really represents his expert understanding and current knowledge of galactic structure. He told me there was new paper he wanted to show me, which involved some remapping of the Orion Arm. I told him about the new gap I wanted, and he replied, “That’s exactly what the paper has discovered!” and sent me the paper showing the data to prove it.

It’s not often the universe conforms so exactly to our wishes!

Mapping the galaxy is not as physically challenging as Cook’s efforts, but it is intellectually no less demanding. It’s a case of not seeing the forest for the trees. Because we are inside the galaxy, we can't see what the whole thing looks like. There is so much impeding our visual exploration when we look at the galaxy’s distant regions. Most of the visual barrier (like Cook’s walls of ice) consists of walls of black dust clouds, opaque to light — the accumulated ash from generations of burning stars. If the vast disk of our Milky Way is likened to a pizza, we have an anchovies’ eye view of the pizza. We can lift up an anchovy, but no spacecraft can travel the thousands of light-years above the disk to get a picture of the shape of the galaxy’s spiral arms.

So we have to infer the shape from what we can see from our vantage point. Radio astronomers study the universe at wavelengths other than visible light, chiefly in the long-wavelength regions. They can use the wavelengths that pass through the dark dust clouds to map the clouds of hydrogen that form the great bulk of our galaxy.

Philosophers Bench sits in an ideal spot to contemplate the Orion Arm of the Galaxy Garden, as well as the garden’s view straight down to the beach. © Jon Lomberg

By careful measurement of motion in these gas clouds, their distance can be determined, and radio maps of the galaxy can be made. By characterizing the radio emissions from sources that are also visible in ordinary light, radio astronomers like Leo Blitz can then guess where star clusters and other objects are in the parts of the galaxy invisible to the eye, based on radio readings. Maps of the shape of spiral arms are the result.

Previous maps had suggested the branching of our Orion Arm from the larger Sagittarius Arm. New results now suggest otherwise.

This figure from Xu et al., 2016, shows a view of galaxy, but you have to flip it vertically in your mind to compare it with the newly revised Portrait of the Milky Way. The dotted blue line shows the shape of the Orion Arm when we thought it was a spur. The solid line shows the newly discovered separation. The Sun is the red circular symbol; the red star denotes the center of the Milky Way. Xu et al., The local spiral structure of the Milky Way, Science Advances, 2016

The title of the paper Leo sent me is “The Local Spiral Structure of the Milky Way” and it appeared in 2016 in the prestigious journal Science Advances. The first author is Ye Xu of the Purple Mountain Observatory in Nanjing, China. The leader of the overall effort to get accurate distances to star-forming regions in the galaxy is Mark Reid from the Center for Astrophysics in Cambridge, Massachusetts. The paper presents distance measurements for eight star-forming regions in our local Orion Arm. Such regions are the main visual markers of the spiral arms. Their results show the Orion Arm is somewhat longer than previously thought, with a “pitch angle” (the arm’s angle with relation to the galactic center ecliptic) running parallel to the Sagittarius and Perseus Arms — known major spiral arms of the galaxy.

The Orion Arm as it appeared in the original Milky Way painting in 1992. © Jon Lomberg

The Northwest Passage of the Orion Arm, as we now understand it. © Jon Lomberg

In conclusion: The Orion Arm may be a more appropriate name than previously thought. More like an arm than a spur, Orion shows a cleaner, more pronounced separation from the Sagittarius Arm.

Looking at the galaxy in conventional compass terms, the gap provides a Northwest Passage through the galaxy, and through the Galaxy Garden as well — without taking artistic license!

I have revised my Portrait of the Milky Way to reflect these new changes, as well as other advances in galactic geography made since the original painting was done in 1992. These include the exoplanets discovered by the Kepler Telescope, the Sagittarius Dwarf Galaxy, and the encircling starstream associated with it. A poster of this artwork is now available through Astronomy magazine.

The final revised and accurate Portrait of the Milky Way; you can purchase this painting as a high-quality poster through Astronomy magazine. © Jon Lomberg

The blue dots represent a typical 1 percent of the exoplanets discovered by Kepler in its search space, looking from the Sun toward the Northwest Passage. The Sun is the tiny yellow dot just to the right of the rightmost blue exoplanet. © Jon Lomberg

Jon Lomberg is an artist and writer who lives in Kona, Hawaii. He was Design Director for NASA’s Voyager Golden Record and Emmy-Award winning Chief Artist for the original Carl Sagan COSMOS series. He is shown here in the very young Hawaii Galaxy Garden at the fountain representing the supermassive black hole at the galactic center.

A work in progress

The Orion Arm takes about 220 million years to revolve around the galactic center. As it does so, it will not retain its form like a log floating down a river. Rather it will move as a cloud does, growing at a leading edge and fading out of view at the trailing edge. At some point it may merge with another arm or fade away entirely as new arms replace the old, over the course of eons.

But for all future human history, our home in the galaxy will be the Orion Arm, separated from its larger, interior neighbor by a Northwest Passage of sorts. I wonder if this little fable is telling us something about how gas flow, the motion of stars, and other “traffic” shapes the galaxy’s spiral structure. As above, so below? I leave that to the astronomers. But for visitors to my Galaxy Gardens in Captain Cook, Delaware, and Pamplona, the Orion Arm’s Northwest Passage is an aid both to exploring and learning about our home galaxy.

Global warming revealed

On Nov. 21, 2016, the Northwest Passage is open sea from the Pacific Ocean to Hudson’s Bay, a route Cook could certainly have navigated. NOAA

So careful were Cook’s records, so accurate his navigation and mapping of the ice, that they provide climate scientists with the earliest reliable benchmark of polar conditions at that time, vital information for tracking the evolution of polar ice over the centuries. Since Cook’s records were made before the Industrial Revolution (nominally dated in 1800), they provide uniquely valuable insight into the changes our technology has been making to the planet’s climate.

And one of the strongest pieces of evidence that global warming is real is the fact that the Northwest Passage is now open for business in the summer, expanding the reach of luxury cruise ships, as well as shortening the route for container and tanker ships. The navies of the North are vying for this strategic position. Yet Cook could not get within hundreds of miles of it — the ice has already retreated that far since his time.