by Michio Kaku
Planet Nine’s Le Verrier is Batygin, who, as 2014 turned into 2015, took to every blackboard and computer simulation he had at his disposal to think over Sheppard and Trujillo’s hypothesis using math that only few people in the world understand. He spent more than a year, along with Brown, trying to figure out why these objects were clustered together in space.
Before Planet Nine, Batygin knew little about observing and Brown didn’t know much about theory, but Planet Nine cannot be found without both. If anyone knew the theory behind how planetary bodies behaved in space, it was Batygin. By 2014, he was a renowned theoretical astrophysicist, and the following year, was named among Forbes 30 Under 30. He had first distinguished himself at the age of twenty-two, when he proved mathematically that our solar system was unstable—a problem Isaac Newton himself had hoped to solve—and that eventually (a few billion years from now) Mercury could either fall into the sun or collide with Venus, which would result in Mars’s ejection from the solar system. Now Brown and Batygin faced a version of the same question Le Verrier asked of himself 169 years ago: what is happening beyond where we can see?
Part of their job was first to try to find a solution less extreme—like a passing star or a galactic anomaly—than a giant undiscovered planet far off in the depths of the solar system, because, a hidden planet? That was absurd. But finally, in the spring of 2015, they both agreed, the only other explanation for this clustering of Kuiper Belt objects was indeed a planet—a big one. On January 20, 2016, they made the announcement proposing that our solar system has a giant planet orbiting far away from everything else. They told all astronomers with access to the most powerful telescopes to go and find it. They wanted to find it too.
Hale Pōhaku. Monday, December 3, 2018. 2:30 a.m.
We met in the cafeteria. It is suggested that all people observing on the summit spend several hours at base camp to adjust to the altitude to prevent dizziness, slurred speech, and death. The summit of the mountain is 13,796 feet and has only 60 percent of the oxygen found at sea level. We were up literally before dawn to begin adjusting to the observing schedule that would now be:
10:30 p.m.: Wake up and eat (Breakfast? Dinner?)
11 p.m.: Leave for the telescope
Midnight to 6 a.m.: Observe
Groggy and grunting, both Brown and Batygin dragged their feet down the stairs of the dorm’s living room. They do their thinking at base camp and their struggling at the summit. (According to Brown, “Thinking at fourteen thousand feet is not a good idea.”) Over Froot Loops and Cheerios, they carefully ran over their own computer simulations with updated search parameters, making inside jokes to each other and giggling. They sometimes debate the location of the planet for hours at a time. At this particular moment, Brown was not only certain that Planet Nine’s semimajor axis—that is, the mean distance of the sun along its orbit—was 310, but he was just about willing to stake his life on it. Batygin disagreed: “The reason that we’re here right now is because it might not be at 310, it might be at 400.” Brown said, looking at me, “Like I said to Konstantin, if we don’t get any data, I’m done with this crap, I’m out.”
“Yeah, but you say that every time,” said Batygin.
To me, “He reminds me that I say that every time.”
“It’s not like you’re doing any actual work.”
“I’m actually doing a lot. It actually takes me a long time.”
It went on like this. At issue was how many data points they were using in their simulations. Brown had two, but Batygin thought this was wrong, and felt that Brown’s room for error (aka, “the wall”) was too small. While they consider themselves “regular Caltech nerds,” this was also a reference to Game of Thrones, since all the distant Kuiper Belt objects are cold and living “beyond the wall.” Quick, someone hold the door for this fight:
“You know where else it could be?” said Batygin. “800 AU.”
“Pshhh.”
“What is the error bar wall? If you try to fit the wall—”
“I don’t try to fit the wall.”
“If you did—”
“I don’t try to fit the wall. You try to fit the wall.”
“If you tried to fit the wall.”
“I wouldn’t.”
This type of friendly, extremely nerdy, almost-marital bickering is typical of Brown and Batygin, and maybe even expected from two guys who have spent the past few years re-creating the solar system together. They each run simulations that begin at some point in the past four billion years. Since we can’t go back in time to see what could have placed Planet Nine where it is or to actually find out where it is, they each re-create the growth of the planets over time. Their simulations can take from three days to three months to run, and they start them after all of the large planets have formed, some three to four billion years ago. In 2018 alone they ran more than two thousand Planet Nine parameters with different masses and locations, averaging thirty-eight new solar systems a week. As a result, the slight variations in data are what keep Brown and Batygin bickering and in check.
In order to find their planet, they need to use one of the most powerful telescopes on Earth to capture the light coming from such a great distance. The Subaru Telescope, which was first named the Japanese National Large Telescope, is owned and operated by the National Astronomical Observatory of Japan. Among telescopes its size, Subaru has the largest field of view and magnification available of any Earth-based telescope, which is why this is their only hope of finding the planet. The special camera on Subaru, the Hyper Suprime-Cam, is the real trick. At 10 feet high and 870 megapixels, it is able to focus down to the width of a human hair. The next day, they would try after an entire year without any usable data. This is the search for Planet Nine.
At 4 p.m., we went to bed.
Hale Pōhaku. Monday, December 3, 2018 (still). 11:15 p.m.
Brown speed-walked into the cafeteria, threw his black messenger bag onto one of the chairs of the round table, and with wide eyes whisper-yelled, “HOW IS THE WEATHER AT THE SUMMIT!?” The thirty-second walk from the dorms to the common building was not great. It was raining. There was fog. Batygin and Surhud More, an astronomer and collaborator from the Japanese science team, were prepared with an answer. “Only 10 percent humidity at the summit,” More replied, trying to settle Brown’s nerves. Over the past three years Brown and Batygin have made five trips to the Subaru Telescope on Mauna Kea. Of the eighteen and a half days they have spent observing, only eight and a half nights have produced useful data. This was no time for fog, almost a four-letter word but not quite.
The parking lot at Hale Pōhaku is paved, while most of the road to the summit is not. A sign at the edge of the parking lot reminds visitors to stop and switch into four-wheel drive for the twenty-five-minute drive up the mountain. This delineation between paved road and unpaved road is a reminder that the journey is dangerous, it takes effort, caution. We must have patience, we must move slowly and remember this is a temporary visit. Our oxygen is about to be reduced by 40 percent, and we will see fewer stars because there is less oxygen in our blood to help our eyes focus. We drove at approximately four miles per hour with just the power of our headlights to prevent us from driving one foot to the right and plummeting down the mountain to our death.
I have been to the tops of mountains, but none like the summit of Mauna Kea. It is not just its meaning and value to the Hawaiian people that might influence the feeling there. When I stepped out of the car, I was grabbed by the wind, encircled, wrapped, and marked—human foreigner. It was cold, below freezing, and it was dark. Nearly the darkest part of any night is around midnight, but after my eyes adjusted, somehow there was a little light. Our bodies’ survival mechanisms kick in, pupils are automatically dilated, opened up as wide as possible. In darkness like this we are vulnerable and our animal brains know it. It is the same feeling I imagine I would have if suddenly placed on Mars. This land is not for humans. There is barely any o
xygen, there is almost no water in the air. There is no life around, no plants, no birds, nothing—these rocks are the beginning and end of everything. Just enough light from the stars overhead reflected off the bright white paint of the domes. There were no smells. The wind hit me again like a giant palm to my body. Even the sound of the dirt and stone below my shoe was foreign, like stepping on glass but not quite. It was a sound I had never heard. I was not where I had been. I felt reverent and intrusive, almost disoriented. With each crunch of rock under my shoe I was reminded that this is old land. Original land. Volcanoes are monoliths formed from fire and water and air—a million-year-old history cracked and ached below my feet.
The mountain last saw fire from its peak 4,500 years ago. It was toward the end of the Bronze Age. Humans began to use the plow. The world’s population was only 25 million, and writing would soon begin in Sumeria and Egypt. I felt suddenly as though I had intruded on the past. Standing there being nearly blown over by the wind and pricked with the cold air felt like being in what in Celtic culture they call a “thin place.” The saying goes that the distance between heaven and earth is only three feet apart, but in a thin place, that distance collapses. Oftentimes it is used to describe the moment when a person is about to take their last breath, or right before they take their first. Where heaven meets the Earth—this is Mauna Kea.
For Hawaiians this mountain is sacred. The highest peak in all the Hawaiian islands, it is what they call a wao akua, which translates to “home of the gods.” The summit of the Mauna, or mountain, is the place where the gods live. Mauna Kea, in English, translates to “white mountain,” a nod to the snow-capped peaks, but the full name is Mauna a Wakea, or god of the sky. Traditionally, only religious leaders and Hawaiian royalty were allowed to travel to the top, the place for shrines, burials, and ceremonies. The summit has never been just for anyone—only those with the right could ascend the mountain and be in the presence of the gods. For this reason the use of the summit as a place for large telescopes and observing has been highly contested by the Native Hawaiian community, considering construction on the mountain as a desecration of their most sacred land. Now “science city” dominates it. Whether you believe in god, or the gods, or heaven or hell, or nothing at all, the summit of this ancient mountain and this sacred place felt as though the distance between the unreachable stars and the top of the Earth had collapsed and for as long as we were there, we existed in the thin place.
Mauna Kea, Subaru Observing Control Room. Tuesday, December 4, 2018. Midnight.
At 14,000 feet Brown’s fears of fog no longer mattered. “I can’t believe it’s so clear!” he said. After taking the elevator up to the third floor where the observing room is, they both nearly ran in, set down their stuff, and immediately got to work. Brown had his laptop open before his jacket was off and Batygin was already on a computer typing in a code that would deliver images to him during the night. They needed to get the telescope calibrated and focused on the patch of sky they would be observing. An engineer and support observer were each at their own computers next to the main screen, which had a countdown clock that read “Time to Completion.” In this instance, they were calibrating the telescope. It counted down: 136, 135, 134, 133. One computer screen hung from the top of the room that showed multiple views of various control rooms, one of which was in Tokyo where, every morning, they greet the Japanese team. Brown and Batygin had the last half of the night, midnight to 6 a.m., for observing. They would observe with half-nights for four days, and the last three they would get the run of the telescope from sundown to sunrise.
The countdown reached zero, and the sound of a cuckoo clock went off. This sound marked the end of calibration. They were ready to observe. It also “cuckooed!” every time an exposure finished. Their plan was to capture about one hundred fields on every half-night, weather permitting. The fields functioned like circles on a map, marking the total viewing area of the telescope: around nine full moons’ worth. Every exposure lasted sixty seconds, and with each one came a new image of the sky. Batygin’s job was to look at random stars in the images to measure their width. The more circular the stars appeared in the camera, the better the seeing was. If he clicked on a star and it appeared jagged, it meant there was upper atmospheric turbulence; if it was slightly oval, the telescope was out of focus; if it appeared washed out, it meant that there was fog. All of this messed with their ability to capture a precise point of light. That’s a problem when your entire task is to capture a precise point of light. The windier the conditions, the more the stars’ light would smear across what is called an arc second. And to find Planet Nine they needed all arc second readings to be under 2.0, ideally under 1.0. Planet Nine likely travels—at the most—two arc seconds a night, so if the winds are too high in the upper atmosphere, so much that it’s smearing the stars into two or three arc seconds wide, the data become unusable. Think of zero arc seconds as being a perfect point in the sky; as the arc seconds creep up, the light gets blurrier, smearing out a little to the sides and blocking whatever possible planet might be hiding behind.
Brown named each field with four numbers in a spreadsheet and kept a log of stars’ arc seconds that Batygin randomly clicked on in that field. If the “seeing” was bad, Brown would make a note in the log and they would have to go back and reimage that field. This is where observing becomes less romantic and more like a creepy radio number station. They would wait to take about ten images, and Batygin would then read off the numbers in batches: “4817 is 1.4. 4918 is 0.9. 4919 is 1.05. 5319 is 1.1. 5318 is 1.4,” and so on.
Minutes after starting up the cameras, they were collecting data. The weather was holding so spirits were high. Maybe a bit too high? Up at 14,000 feet one can get what is called an “altitude high,” which happens when the brain is deprived of oxygen. Some people get cranky, some get sleepy and mellow. Batygin gets happy. More, even, than normal. Every time he comes up to the summit, he has to use oxygen so he knew he was due for some air. There was a first aid cabinet with personal oxygen tanks that you strap around your waist with a belt and prewrapped plastic nose inserts. It was 12:45 a.m. and Batygin had not yet plugged in.
He was in the thick of collecting star data and writing down the next set of numbers to read off to Brown when he opened an image of stars. The sensors on the camera, all 116 of them, collect so much of the sky that as soon as you start to zoom in on any photo, not only do you fill the screen with so many stars that it looks like TV static, but galaxies appear, asteroids, you name it. The screen becomes littered with space stuff. With a black-and-white image open, he pointed to the screen and said, “I think I found Planet Nine!” He was joking, but to Brown’s ears, he sounded way too happy. Brown jumped up out of his seat, grumbled “Oh man” under his breath, and walked to the first aid cabinet for a monitor to test Batygin’s oxygen. It was below 70. His lips had turned a little purple, and he was way too excited to be up at midnight and working. Brown was worried about him, but Batygin laughed it off, with a facetious dying message to his wife: “Just tell Olga I love her.” He unwrapped the plastic tubes that strap around your head and placed them inside his nose. “I’m about to get way less happy,” Batygin said, half disappointed, half warning us all. He flipped the switch on the oxygen tank, the batteries started up, and he took in one long deep breath.
The control room had more than two dozen computer monitors, most of which have specific readouts: the temperature of the telescope mirror, precipitation, wind speed, etc. Above the computers was a shelf with five speakers that each trace back to a microphone placed on the telescope. Every time the camera’s shutter opened and closed it made a sound like Optimus Prime mid-transformation. The volume was up loud so that staff could walk to the break room for coffee and still hear the shutter open and close, which it does every sixty seconds, followed by a cuckoo to mark the successful download of the exposure. Open, sixty seconds, close, “cuckoo!”
Subaru collects a lot of light and fr
om a large swath of the sky. As a result, every night the team’s data contained hundreds of asteroids and Kuiper Belt objects, many that have never been seen before. Under normal circumstances, these appearances would warrant follow-up, and even excitement, but there is an urgency to this search. Brown and Batygin don’t have time to chase these things night after night, which is what is required to “discover” something. These objects are just light that is collected and discarded. As Batygin and More sorted through images, measuring the seeing in each field, discussing numbers and computer codes, a new image came through and they zoomed in. Against the blue of the computer screen, a massive spiral galaxy appeared. It had a wispy ghostlike body with long, almost jellyfish-like tendrils that stretched around on itself. We leaned over to look at the picture and said, “Oh wow!” which warranted a quick half-joking reply from Brown: “Ugh, galaxies. Those are the worst.”
The trouble with looking for one thing in the sky is that our galaxy is full of stars, 100 billion of them, most of which annoy Brown to no end. If Planet Nine exists, it is so faint and so far away that it can easily get overpowered by a regular show-hogging ham of a star. The absolute worst place to look for Planet Nine is into the plane of our galaxy where a lot of those stars live. By 2 a.m., another package of Pop-Tarts had been opened. The numbers were coming in over 1.4—not great. Brown decided they should move the telescope and begin observing on the other side of the galactic plane. They sent the request to the telescope operators to calculate how long the slew would take. They told him that because of the time of night, to get around the plane of the galaxy would take forty minutes. “Forty minutes!” Brown exclaimed, “Shit, shit, fuck, fuck.”
Forty minutes is a long time. I was told that it costs a dollar a second to use this telescope, and forty minutes is a lot of observing time lost when you only have six hours in one night to find a planet. He decided they would wait a few more hours until the galactic plane had moved overhead, so the slew that would have taken forty minutes would only take ten. They would keep observing with the 1.4s until the 4 a.m. slew.
