Mysterious Light Sources

I got my first telescope in 2017, in time for the Great American Eclipse. I started paying attention to the concept of light pollution, including finding detailed maps of what places had high or low amounts of light pollution. After looking up nearby areas that were potentially good for stargazing, I got curious, and started just looking around at what all the light pollution was from. Of course, the vast majority of light pollution is from cities: street lights, industrial zones, parking lots. But sometimes, it’s from something else.


My first find was when looking over my home state of Maine. At first glance, everything looks normal. Bright spots for the two biggest cities, Portland and Bangor. Scattered lights over the whole coast. Pitch black over Baxter State Park.


But wait, what’s that other bright spot? It looks almost as bright as Portland. I’m not familiar with a city there.


Zooming in, we can see that it is… nothing. Just a bend in a river.


Switching to google maps satellite mode, we can see that there definitely isn’t a city there. But there is this large, flat building.


What kind of building produces a city’s worth of light pollution? At the time it wasn’t labeled on google maps, so I switched to street view and tried to find signs. I googled random guesses. Somehow, I found it. It’s a tomato farm called Backyard Farms. The tomatoes are in a massive green house. And while most of the time the tomatoes grow by sunlight, the winter hours in Maine are very short, and so this greenhouse augments its growing season with an enormous array of yellow lamps. And this makes it the single greatest source of light pollution in the entire state.

North Dakota

If you looked at this light pollution map of the United States, you might start to wonder after a minute; what is this sprawling metropolis in North Dakota?


Zooming in, we can see that its location is not the only odd feature. While the light pollution of most urban areas is relatively smooth and peaks in a small number of central places, this phenomenon seems to be quite blotchy.


Again, switching to google maps, we see an intense lack of urbanization. Zooming in all the way reveals the truth.


If you don’t recognize the shadow, this is an oil field. The light pollution comes from the associated gas flares. These flares are deliberate, continuously burning fires, and they convert methane, a potent greenhouse gas, into CO2, a much less potent greenhouse gas.


While the entire subject is rife with controversy, oil fields continue to shape our landscapes. Here’s a strange looking nebula in Texas.


And here is a constellation of offshore oil rigs in the Gulf of Mexico.



Lastly, I was wondering to myself what the light pollution around Mauna Kea looked like. Mauna Kea is a mountain in Hawaii that hosts a dozen of the world’s finest astronomical observatories. It has near-perfect viewing conditions, including being above most of the water vapor in the atmosphere. But it still shares an island with two hundred thousand people, who are producing a noticeable amount of light. So what does the map say?


Panning over to Hawaii, we see that Honolulu is by far the biggest source of light pollution. Fortunately, it’s over 200km away from Mauna Kea, and doesn’t contribute to light pollution there. But the big island does seem to have its own major source. What could it be?


Zooming in, we see that it’s pretty point-like, symmetric and centralized. But there’s no city there.


Instead, there’s a volcano. Kīlauea, as an active volcano, regularly has literal glowing lava occupying the caldera. The amount of light changes with the level of eruption activity. Fortunately, at least according to the map, the light pollution doesn’t quite reach the summit of Mauna Kea.



Like daytime satellite mapping, night time light pollution maps are an extremely useful tool. Their uses go beyond recreational exploring and picking a good place to use your telescope; they can be used by environmental scientists to track wildfires, by economists to estimate GDP of countries, or by intelligence agencies to detect undisclosed industrial facilities.

Can you find any mystery light sources on the map?

Just Curious

Today is the 50th anniversary of the Apollo 11 moon landing. You have probably heard this, because the first moon landing often tops lists of the most significant historical events. It is a cause for celebration of humanity and what we are capable of in the best of times.

Yet many of us ardent space fans have quite mixed feelings about the anniversary, because we have not “been back”. Humanity has not sent a person past low-earth orbit since the end of the Apollo program when Eugene Cernan climbed back into the lunar lander on December 14, 1972.

This is a good time to reflect on our values. It’s not obvious to me that we should have gone to the moon back in 1969. It was ultimately politically motivated, and paid for by taxpayer money. Maybe we should have done something else with that money, like ending the Vietnam war faster. I don’t know. I wasn’t there.

But that was then. What should we do now? We get to decide. NASA is currently pursuing a directive to go back to the moon, as they have been many times since 1972. Their failure to get back has a lot of causes, but a major one is that the populace isn’t rallying for it. Constituents rallied for Apollo for as long as it was a competition with the USSR. After a few half-billion dollar Apollo missions, they started getting tired. They started noticing other problems.

How do you want us to be spending our collective economic fruits? If everyone was a clone of me, then the NFL’s $15 billion revenue would instead be used to double NASA’s budget. But I wouldn’t put everything we have into space exploration; there are too many things that matter. How would you allocate it? And how do you want to be spending your own resources? How much do you want to be exploring the world, going on road trips, discovering new and fascinating people and phenomena, and how much do you just want to make sure that your sister feels better when she gets sick?

As mammals we all have deep drives to conserve and ensure our comfort and survival. As humans, we also have something else; something that helps give meaning to survival. Sometimes, it’s just looking at an object on a shelf and thinking, what is this? You pick it up to inspect it with a look in your eyes. You are not and never were going to buy it. You don’t need to use it for a task. There are another hundred thousand objects in this store. You were just curious.

A bird off in the distance is doing something that catches your eye. It’s circling and dancing around a tree top in a strange way. It periodically lands and takes off again. You watch it for a while, thinking about life as a bird. Is it doing a mating dance? Is it looking for its nest? Is it trying to intimidate some other creature? You’re not going to look it up. You’re not going to film it and ask an ornithologist. You’re just curious. You ask your friends who live nearby. They say they think they’ve seen birds doing that when it gets especially hot and dry. Interesting, you say. The conversation moves on. You’re just curious.

You walk down the street and see someone crouched down, painting a tiny flower on a fire hydrant. They look so happy. Two blocks later, you see someone performing gestures of prayer. They look at peace. When you get back to your apartment, you look at your small garden and smile. You decide to tend to it, and while you do, you think about people. What makes them happy? Why do they do what they do? Why do they find things beautiful? As you garden, you decide that you will start asking people. You gaze down onto the street with a look in your eyes.

Sometimes the curiosity is fleeting, and sometimes it lingers. Sometimes it alerts you to a concern. Sometimes it leads you on a half-day quest to understand, and sometimes it lights a fire inside you, and you acquire an almost paralyzing fixation on the question. You drive your car past your house because you are thinking about the question. You change your careers to better investigate the question. You leave your social support network to move across the country to work with others on the question. You establish an institute and you petition policy makers and you become chief administrator of an entire governmental department to answer the damn question.

I don’t know why we look over horizons and wonder what’s beyond, and I don’t know whether it’s ultimately calibrated toward helping the species survive. I don’t know whether we should have gone to the moon in 1969. But when I think of what we’ve done, I feel a joy that can be fueled no other way, and I would be happy for you to join me on our quest to answer these questions. Let us always take care of ourselves and our loved ones along the way, let us always consider the allocation of resources with utmost somberness, and let us never lose that look in our eyes.

Where no spacecraft has gone before

The list of bodies in the solar system unvisited by human devices is tantalizingly short. But there’s one object that many people might be surprised to find out we haven’t sent probes to; the sun.

On 12 August 2018, NASA’s Parker Solar Probe began to make its way closer to the sun than any man-made object before it, and there are a couple reasons why its journey was challenging to design. The obvious one is that the sun is hot; it took decades to invent and perfect insulators, sensors and solar panels that could handle the heat. But the other reason has to do with orbital mechanics; it is significantly harder to go straight to the sun than it is to leave the solar system.

How could this be? Right away we can tell that it’s not about distance. Jupiter is five times further than the sun, yet we’ve gone there nine times. The key is that “going places” in space is effortful in a totally different way than going places on the surface of the earth. Rocket scientists don’t think in terms of distance.

On earth, getting some place is hard because there’s friction everywhere, and stuff in the way. When you walk or run, every time you put your foot down, the ground reabsorbs much of the energy from the last step. Cars in neutral roll to a stop after a few hundred feet. Even jet engines have to burn huge amounts of fuel just to push through the drag of the air. Since there is resistance along every meter or mile, travel is effortful per unit distance; per unit of stuff you have to push past.

In space there is nothing resisting motion, so distance is in some sense free. Once you get up to speed, you just stay that speed. Of course it does still take time to go that distance, but it doesn’t cost any more “effort” (which is usually fuel, for a spacecraft).

I just said “you stay that speed”, but more accurately, you stay at that “energy level”. Travelling through a gravitational field changes your trajectory. Things also get more complicated because those sources of gravity are points in space, which means that travellers will end up rotating around them. Rotation always makes things less intuitive.

I find it very useful to imagine the physical analogy of the sun “sinking” down into space, causing a big gravity well. When other bodies are near the sun, they feel the sloped edges of the gravity well, and want to move toward it. But if those bodies are also moving sideways, then they can just roll around the sides of the well like marbles without ever falling in. This video gives a real-world demonstration.

The Earth orbits the sun in a circular path, and therefore stays the same speed all the way around. But comets, for example, orbit the sun in a path called an ellipse. For part of their path they are a small distance from the sun and moving quickly, and for another part of their path, they are a large distance from the sun and moving slowly. They whip around the gravity well in bursts. But at any given time, the “kinetic” energy from its speed and the “potential” energy (the energy an apple has before falling from a tree) adds up to the same energy level. Travelling the path of the orbit will shift the balance of the two kinds, but the total remains the same.

So if your current path takes you to where you want to go, you can just wait; but if your destination is at a different “energy level”, you have to change your energy to match it. (And then wait.) There’s also the question of what we measure our energy level with respect to; for our purposes, we’ll use the most dominant body in the system, namely the sun.

If you want to orbit the sun close to its surface, you need a small energy level with respect to the sun. The earth, since it is relatively far from the sun, has a large energy level with respect to the sun. If you are on the earth, you share the same energy level.

Consider the gravity well analogy above. If the earth is a marble rolling around the well endlessly, and the space probe is a tiny micro-marble, and the probe separates from earth, it will also just roll around the gravity well at the same distance. The sun’s pull doesn’t imply that the probe can just “give up” and drop into the well; it has to lose the kinetic energy it has, and then the sun’s pull will drop its orbit closer.

Therefore, if you are coming from earth like a newly built space probe and you want to get to the sun, you have to get rid of a lot of the energy of your current level. In space, getting rid of energy is as hard as gaining it. There’s no friction to drain it from you. So to change your energy level, you have to push or pull on other stuff. To change your energy level a lot, you can either push or pull really hard, push or pull on a lot of stuff, or just not weigh very much to start with. The Parker Solar Probe will use all three strategies.

The Delta IV series. The Parker Solar Probe launched on the rightmost rocket. Source: Wikimedia Commons

To push really hard, you want a big, big rocket. Parker launched on the Delta IV Heavy, which was the most capable rocket in operation from 2011 (when the Space Shuttle retired) until this year (with the launch of the Falcon Heavy). The Delta IV is a hefty machine; it could haul a few cars into orbit in one go. Parker, weighing less than a smart car, is going a lot farther away (or “faster away”) than earth orbit, so it requires the Heavy variant. This rocket is three Delta IV boosters bolted together, with the second stage on top of the middle booster. It could take up a school bus and the Hubble at the same time. But Parker still isn’t satisfied. It has a need; a need for speed. So it uses that unallocated payload capacity to bring up its own personal third-stage rocket. The Parker Solar Probe is the only mission that has needed a third stage on top of the Delta IV Heavy.

But in truth, this isn’t nearly enough. So after all the rockets burn, the Probe is headed toward Venus to pull on a lot of stuff. Parker will be performing seven gravity assists from Venus during its mission. When any two bodies move past each other in space, they pull on each other through gravity. Depending on your reference frame, this causes one of them to speed up, and the other to slow down. In our case, Parker will be using Venus to lose energy with respect to the sun, therefore falling deeper into the sun’s gravity well. Since planets have an enormous amount of mass, Venus will only speed up an infinitesimal amount, but Parker will feel a huge change.

Ultimately, the Probe will manage to lose enough energy to get within 4.5 solar diameters from the sun. This course takes it directly through the corona, a thin layer of physical sun stuff. This stuff doesn’t act like we expect it to; it’s hundreds of times hotter than the sun’s surface below. Heliophysicists have been unable to account for this fact using remote observations. So to solve this mystery, we will have to go to the heart of it.

You can follow the Parker Solar Probe’s progress toward the sun by following NASA Sun & Space on twitter.

The Parker Solar Probe being mounted inside the payload fairing of the Delta IV Heavy. On the top of the probe is the sunshield; the grey sphere in the middle is the fuel tank for the third stage, which detached after firing. Source: Goddard Media Studios

Getting closer

In recent months, two of my hobbies have been amateur telescopy and spectating at orbital rocket launches. Conceptually, these are kin; one brings the universe closer to us, and the other brings us closer to the universe. But experientially, they don’t share much. One is silent, rigid, and tests your patience, the other is an explosion of matter and emotions, gone before you can grasp it.

If there’s anything I’m optimizing for at a launch, it is to “be there”. Everyone knows that rockets go up, just as everyone knows that babies are born. But it is something different to be there. You can watch a live stream of a launch, just as you can watch the superbowl on TV. But even though you see what happens at the same time as everyone else, it is something different to be there.

I don’t know how or why, but some part of the mind knows, and cares deeply, about the distinction between knowing and experiencing. So after I saw my first launch I thought, how can I get closer? How can I increase the intensity of my experience? During that first launch I had used binoculars, and they helped me resolve significantly more detail. So… why not watch a launch through a telescope?

Now, let’s just be clear that this is a ridiculous idea. Finding a still object in the night sky is a tricky endeavor. If it’s really bright like the Mars or Vega you can point and shoot, but for most cases you want a “finder” scope, a smaller, low magnification scope that’s aligned with the big one. It’s far easier to find an object at lower magnification where you can see lots of surrounding context, and then switch to a higher magnification for detail, than to start at higher magnification and only be able to see a few nearby stars for orientation. Furthermore, if the object is moving, it’s tricky to keep up. Most things in the night sky don’t seem to move, but everything has an apparent motion of at least at the rate that the earth rotates. The highest magnification my equipment gets is ~500x, and at that rate the earth takes it out of the viewing field in maybe 15 seconds. I’ve caught planes in the scope before, and it was pretty cool, but you definitely had to be on your toes to keep up with it. Obviously a rocket goes faster than a plane.

Nevertheless, I’m at a place in my life where it’s good for me to practice the virtue of empiricism. So I dragged the gear all the way to Vandenberg and set it up in broad daylight. I was with three other friends and we’re watching a Falcon 9 take up a batch of Iridium satellites. (You can see the original webcast for this launch here). From the closest public viewing spot on Ocean Ave, you can’t actually see the launch facility. Though it’s only 3.5 miles away, the Air Force had an understandable desire that their base not be easily visible, so there’s a hill in the way, just high enough to cover it all. So I couldn’t just point the scope at the rocket on the pad, wait for liftoff, and track it from there. I’d have to catch it in the air.

While we wait, I put in the eyepiece. Normally during an astronomy session, I start looking at something with the lower-magnification eyepieces and work my way up. In this case, my moving target gives me no time to switch them out. I want to see the rocket at the highest magnification I can, but that will also make it harder to find and track in the scope. So I pick an eyepiece in the middle, with a 10mm focal length, giving me 65x magnification. I make sure it’s focused, using the one distant building we can see.

As an aside, I was also curious as to whether the exhaust flames could be seen through the solar viewing glasses we all bought for the eclipse of August 2017. The exhaust has the extraordinary brightness quality of the sun, while being obviously not as bright (otherwise viewing launches would be a discouraged act).

At the exact prescribed time, we see the column of flames rise over the hill, and I grab the eclipse glasses. It takes a second for my eyes to adjust to the darkness (because the launch is during the day) but indeed I can see the flames through the glasses. This puts a very high lower bound on their brightness; much brighter than a lightbulb.

As soon as that’s established, I run over to the scope. With the rocket rising fast, I crouch behind it and slew it to where I think the rocket will be by the time I stand up and get my eye in the eyepiece. Bingo. It’s early enough in the burn that the vehicle still subtends a very large angle in the sky, and its brightness also leaves a halo to follow. But it’s still moving, so I immediately have to get my bearings and start to guide the scope upwards.

Screenshot from 2018-07-15 22-00-29
The Falcon 9 during ascent. The exhaust plume spreads out as the atmospheric pressure drops, making the nozzle effectively underexpanded.

The detail is beautiful. I can see the bulb of the payload fairings, I can see the landing legs, I can see the grid fins. If it were rotated correctly, I’m sure I could read the SpaceX logo. I follow its steady rise, up and up and up. I wish I had a camera where my eye is. I lose it for a second, but I follow its orange halo back. Since rockets always end up going away from you, the fuselage tips over and becomes increasingly foreshortened. And since the atmospheric pressure around the rocket is decreasing as it gains altitude, the flames start to fan out. The Falcon 9 has eight engines in a circle and one in the center, making a pattern of flames that ends up looking something like a flower. This pattern is very clear through the scope. The flames spread wider, and consequently get dimmer. After a couple minutes, the flames cut out. There’s no announcer at this viewing spot, so I yell out “main engine cut off!” in case anyone is interested. I see the long white blur split in two, and the pieces drift apart. “Stage separation!” At 50 miles up, the pieces are really tiny, but still discernible. I see flames again. “Second stage ignition!”

Now there are two objects in my view. One of them, carrying the payload, is accelerating toward space under 210,000 pounds of thrust. The other, a charred and spent 16-story machine, is in freefall. I have about four seconds before one of them goes out of view. The booster is landing in the ocean; there’ll be no boost-back burn, but there will be an entry burn to slow it down. The second stage is small and only getting smaller. I decide to let it go.

To my surprise, I see some angular puffs of white come from the top of the first stage. They’re so rapid and dim that they seem more like a light blinking than a rocket engine. I later learn that these are cold nitrogen thrusters, pressurized cans of gas used to make very slow but precise changes to the rocket’s orientation. (You can see these in the webcast starting here.) They appear sporadically, clearly the result of real-time calculations of the rocket’s current position.

Though the booster is now falling to the ground, it’s still travelling away from me and toward the deep pacific ocean. The sheer distance between us gives the sky the chance to obscure it with the blueness of Rayleigh scattering. I lose sight of the now infinitesimal machine.

After almost three minutes of continuous viewing, I step away from the scope and look up for the first time. There’s a fantastic contrail extending to the southeast, and it casts its own shadow in the mist of the upper atmosphere. Besides that, it’s over. There is nothing more to see. Even the crackle has faded. I look around at my friends, realizing that they had a completely different experience than me. That… was awesome. But also… it felt pretty similar to just watching a webcast. It actually felt less like “being there”. After some reflection, I concluded that the fact that I couldn’t easily switch between looking through the scope and looking at the sky, like one can with binoculars, was a critical factor. I could only use one eye. I couldn’t place what I was seeing in my surrounding context; I couldn’t connect it with the sounds I was hearing; I couldn’t see all the people around me reacting. It was worth doing, but I’m very glad I tried it during my second launch viewing. I’ll have to find some other way to get closer.

The Maiden Launch of the Falcon Heavy

The second reason to see a live rocket launch is the crowd. Their energy is irreproducible. Humanity cares about this. Ten minutes before launch, the cheering at Kennedy Space Center starts in ripples.

We all shuffle around anxiously, fussing over the perfect spot. I pull up google maps and try to triangulate the exact direction it will come from. I get pretty confident. But I know it won’t matter after the first five seconds. From seven miles away, we’re all getting pretty much the same view. I put my phone away.

It’s five minutes away, and John Insprucker comes onto the webcast. I’ve never heard him so happy. He gives a review of the mission, but we know what’s going to happen. We know what we came here to see. Despite the giant screen and the big speakers, he’s just another one of the crowd, here to celebrate with us.

There’s nothing to think about now. I watch the clock and wait. T -1:00. I remember to start the decibel meter on my phone. I put my phone away for the last time. We stare and watch. The crowd can’t handle it anymore; we start to count down.

It gets to zero, and I see nothing. I hear nothing. The trees take the sight of ignition from me, and the distance its rumble. From webcast we can tell that things are fine. We wait long seconds until finally people start to cheer.

“I see it, it see it!”
“There it is!”
“Go baby, go!”

The rumble begins to sweep over the field and the crowd bursts into cheering and applause. I catch my first glimpse of it through a sparse tree. The rocket is a spot of brilliance, climbing slowly through the sky. If it lasts long enough, it will come out the other side.

Videos of the launch will show the flames as a splotch of white pixels, capped out at the brightness of the screen. Here at the Cape I get to learn that the exhaust is a tiny point of blazing light. It’s much brighter than a candle or fire. It has the brightness quality of the sun, but much less so. The closest thing I can think of is when I saw burning magnesium, only this is yellow instead of blue. It’s too far and too bright to see the body of the rocket. I’ll see plenty of that afterwards.

My heart is still; it’s waiting. I don’t know what’s going to happen. This isn’t a movie, and anything could happen. I have to pay attention, because it matters. We are all in this together, humanity, and I need to know whether what we’ve done has worked.

The rocket climbs through a different layer of the atmosphere and starts to make a contrail. I raise my binoculars and follow it from here.

I’ve seen enough live-streamed launches to know what this part looks like. The exhaust plume is widening out like a flower because the atmospheric pressure is dropping. Technically that’s all lost momentum that could have been used to push the rocket forward, but the nozzle is designed to operate optimally at sea level.

The seconds drift by, and it feels unreal. I can tell by the width of the plume that the side boosters are going to drop soon. With the rocket almost lost into the haze of Rayleigh scattering, the webcast calls out BECO; booster engine cutoff. I see the now dim orange flame switch off into white smoke, and little diffuse streams start coming out the sides. The boosters are falling.

At each new event, the webcast call out, and the cheering of the crowd pulses and washes over itself. It never dies down completely. I lose sight of the booster trail through the distance and a cloud. I bring the binoculars down and give my mind a rest. We have a while before anything else will be seen. The center core is too far downrange; all that will come from the webcast. I look around the sky and take in the sight of my first rocket contrail. I remember the decibel meter on my phone. It was never very loud; roaring, rippling, crunching, yes, but less loud than the airplane ride here.

I wander over to get a better view of the screen. They switch to the payload camera. Music begins and builds up, and precisely at the climax, they call out fairing separation, and in a flash of light the Starman in his roadster are visible against the blue earth. Never before have so many cheered for fairing separation, and never before in the 21st century have so many felt represented by a human figure in space.

The artistic peak has been achieved, but the show is not over. We must have missed the boostback burn behind the cloud, but people start to see the boosters now. I squint and shift and follow other people’s pointing. Eventually, I see them. Two specks, bright white, but lit only by the sun. I raise my binoculars.

Have you ever seen a tower falling from the sky? In a sight like no other, these machines drifted through the air, both bizarrely out of place and designed exclusively for this purpose.

The Falcon booster is 16 stories tall. Imagine standing in front of a 16 story tower; now imagine it falling through the air. Through the binoculars I saw two of those, clear as day. Enough to distinguish the charred landing legs from the white body, and writing on the side. These towers are in freefall, and in absolute control of their destination. They fall with confidence, diving like the bird of their namesake, conserving their energy for the last few seconds.

Something will happen between now and those final moments. We know what we hope happens. We have done all we know how to ensure it. And now we must watch.

The giants begin their entry burn, and the retro-thrusting engulfs their bodies in flame. They are blazing points of light in the sky now, those twin birds of fury, and we howl for their return. They sear the sky and the entry burn ends. As they resume freefall toward the horizon, we don’t know whether we will see the final landing burn before they disappear behind the building in front of us.

Just a few degrees above the building, the flames appear once more, and the roar of the crowd follows. They float down in levitation, blink out of view, and the webcast confirms; “The Falcons have landed.”

BA-BOOM. BA-BOOM. As if celebratory fireworks, the pair of double sonic booms returns our celebratory calls. Of course, they weren’t generated on landing; they were generated 30 seconds ago on descent, delayed by as much time as it would have taken the rockets to get to us when the sound was made.

My voice is sore. This part of the mission has been completed to perfection. The rest we will have to learn later. The fate of the center core remains unknown. My mind is left to itself now, amongst the thousands of other witnesses.

The first reason to see a live rocket launch is because it is real.