Was ‘Oumuamua a rock or an alien scout? Harvard astronomer talks controversial hypothesis in new book
Ari Loeb, who suggested in 2018 that the mysterious object was an alien craft, is back to discuss the evidence.
- 'Oumuamua is the first known object we've observed coming to our solar system from somewhere beyond it.
- Most experts think it was just a very odd rock, but not everyone is so sure.
- Harvard astronomer Ari Loeb says the evidence is more consistent with it having been a light-sail spacecraft.
If we became especially interested in another solar system and wanted to send an exploratory craft, how would we do it? Even the nearest solar system—Proxima Centauri is its sun—is about 40,208,000,000,000 kilometers from here, so there's no way our scout could carry enough fuel to get there. Might we could use something like a light, or solar, sail? Light-sail craft already exist, and they do work.
Harvard University astronomer Avi Loeb made headlines in 2018 when he suggested that the extra-solar object 'Oumuamua—which, after all, does mean "scout" in Hawaiian—was just such a craft sent to have a look at our solar system. Since then, if anything he's become even more convinced, and Loeb has just published his reasoning and other thoughts in a new book, "Extraterrestrial: The First Sign of Intelligent Life beyond Earth."
But it's a rock
Credit: M. Kornmesser, European Southern Observatory (top)/ K. Meech et al., NASA (bottom)
The visual image that comes to mind in thinking about 'Oumuamua is the artist's rendition (above top) that was released by the European Southern Observatory when the object was discovered on its way out of our solar system in 2017. Listening to Loeb's claims, one may think, "What light sail? It's a rock."
However, it's all too easy to forget that this ubiquitous image is just an artists' rendition after all, based on the assumption that our visitor was a rock. It need not have looked like this at all. We have no idea what 'Oumuamua really looked like, since the image at the bottom shows the best look at the object we really got.
What is a light sail?
The camera on Planetary Society's Light Sail 2 capture an image of northern Brazil
Credit: Planetary Society
A light sail is a spacecraft constructed from panels of a lightweight, reflective material such as Mylar or polyimide treated with a metallic reflective coating. When photons from a star, such as our Sun, hit the sail, they give it a small push. When the photons bounce back off of the sail, they give it another one. It doesn't take much of a shove to move a light sail through a vacuum of space, and it's believed light sails can pick up quite a lot of speed as they go. Loeb himself is involved in the Breakthrough Starshot project that envisions light-sail craft shooting through space at 100 million miles an hour.
The first functioning light sail, LightSail Sail 2 was sent aloft by the Planetary Society in June 2019, and is currently orbiting the Earth. This year, NASA plans to deploy the NEA Scout mission that will send an 86-square-meter light sail off from Moon orbit to explore the near-Earth asteroid Itokawa.
To Loeb, the object's apparent appearance and behavior doesn't suggest a rock.
First off, what appears to be 'Oumuamua's shape—described as being about 100 meters long and resembling either a cigar or pancake—doesn't describe previously seen comets or asteroids. Second, 'Oumuamua was also exceptionally bright, 10 times moreso than space rocks typically seen whizzing around our solar system. This high level of reflectivity would consistent with a shiny, metallic surface.
Finally, 'Oumuamua accelerated as it whipped around the sun as if it was picking up energy from the star. While such behavior is common when comets speed up, pushed forward by evaporating gasses from the sun's warm, no such gases were observed with 'Oumuamua.
With all this in mind, Loeb, along with co-author Shmuel Bialy, published a controversial paper in Fall of 2018 in the Astrophysical Journal Letters hypothesizing the object might be an extraterrestrial craft. The paper suggested that maybe "'Oumuamua is a lightsail, floating in interstellar space," perhaps "debris from advanced technological equipment." It also posited an admittedly more "exotic" possibility, "that 'Oumuamua may be a fully operational probe sent intentionally to Earth vicinity by an alien civilization."
Needless to say, the paper was met with a great deal of excitement. Did 'Oumuamua signify the presence of intelligent life beyond our solar system, or—as many scientists felt—was such conjecture unworthy of serious consideration?
Welcome to 2021
As the title of his new book implies, Loeb continues to assert the validity of his earlier analysis, demanding that the scientific community at least consider the possibility that 'Oumuamua was an exploratory craft.
One of the underlying themes of the book is Loeb's concern about the "health" of a scientific community that can't even entertain a hypothesis such as his and Bialy's. (This month, Scientific American published an extended and thought-provoking interview with Loeb.) In the book and interview, Loeb attributes his notoriety to an overreaction by the scientific community to his 2018 paper. While much of the book is autobiographical, Loeb claims he isn't interested in his own fame, and he recently stepped down from Harvard's Astronomy department.
"My message is that something is wrong with the scientific community today in terms of its health," Loeb told Scientific American, adding that too many in the science community are motivated by ego and self-image, when science should be about taking risks and trying to understand the world.
"People ask why I get this media attention. The only reason is because my colleagues are not using common sense," Loeb said. "Contrast string theory and multiverses with what I and many others say, which is that based on the data from NASA's Kepler mission, roughly half of the galaxy's sunlike stars have a planet about the size of the Earth, at about the same distance of the Earth from the sun, so that you can have liquid water on the surface and the chemistry of life as we know it. So if you roll the dice on life billions of times in the Milky Way, what is the chance that we are alone?"
An elegant, 400-year-old means of navigating the stars takes flight.
- The Planetary Society is about to launch LightSail 2, a crowdfunded light sail craft.
- LightSail 2 uses photons from the sun as fuel.
- Space X's Falcom Heavy rocket will carry LightSail 2 aloft, 720 kilometers up.
In a 1608 letter to his friend Galileo Galilei, the German astronomer Johannes Kepler described his idea for space travel thusly:
"Provide ships or sails adapted to the heavenly breezes, and there will be some who will brave even that void."
Observing one of the 75-year transits of Earth by what would come to be known as Halley's Comet, he'd correctly intuited that the widening of that comet's tail, or coma, was produced by sunlight pushing material out and away from the main object.
Kepler seemed to immediately see the possibilities — i.e., a light sail.
Now — no later than June 24, 2019, as of this writing — the Planetary Society will be launching what they hope will be the first controlled light sail ever to enter and maintain Earth orbit. Their crowdfunded Lightsail 2 will ride aboard a Space X Falcon Heavy rocket departing from Launch Complex 39A at NASA's Kennedy Space Center in Florida for a year-long orbit.
"This is history in the making — LightSail 2 will fundamentally advance the technology of spaceflight," says Bill Nye, CEO of the Planetary Society.
The pieces of Kepler's dream have been falling into place bit by bit since that letter to Galileo. The discovery of photons in the late 1800s by James Clerk Maxwell revealed the energetic particles in light whose momentum could be transferred to other objects.
Friedrich Zander envisioned the "tremendous mirrors of very thin sheets" propelling craft through space, and then Carl Wiley foresaw a solar sail as a shiny, reflective, parachute-like material opening in the direction of sunlight.
By 1976, Carl Sagan went on TV to show off a demonstration model of a light sail craft, enthusing about the amazing technology and its potential.
Among Sagan's students some 40 years ago was Nye, a frequent Big Think contributor. The Society was founded by Sagan, Bruce Murray and Louis Friedman in 1980. In 2005, the Society launched the world's first light sail craft, the Cosmos 1, aboard a submarine-based ICBM. Unfortunately, it was lost when the ICBM failed before allowing Cosmos 1 a chance to fly on its own.
About the Planetary Society
The Planetary Society is the world's largest non-profit space organization, crowdfunded by over 50,000 members from over 100 countries, and supported by hundreds of volunteers. The Society was founded as outlet for the general public's interest in space, a level of interest not always reflected in governmental budgets. In addition to mounting projects such as the LightSail craft, the Society serves as an educational connection between the scientific community and the general public, advocates for robust governmental funding of space programs, and provides anyone an opportunity to get involved in some real space science.
The Society’s Lightsail craft
At the center of each frankly beautiful LightSail craft is a cubesat. While we tend to think of satellites as large, bus-sized objects, they can be much smaller for simpler missions. The cubesat for the upcoming LightSail 2, for example, is about the size of a loaf of bread.
At launch, the cubesat and sails are encased in four solar panels. Once in orbit, the panels swing up into operational position, exposing the cubesat and stored sails.
The sails themselves are four shiny Mylar sheets 4.5 microns thick — that's thinner than a human hair. They're next pulled outward by four cobalt-alloy booms that extend like tape measures. The process takes about three minutes. When deployed, the triangular sails together form a square that's just 32 square meters, about the size of a boxing ring.
The primary force to be overcome by LightSail craft is atmospheric drag, its collision with gas particles in the Earth's upper atmosphere. Think of it as friction that causes a satellite to slow and thus drop from orbit. In order for a craft to catch enough photon "propellant" — and to be high enough to get away from the upper atmosphere, its orbit needs to be above about 700 kilometers.
The Society has built two LightSail craft.
Image source: Planetary Society
Around 2014, NASA offered the Society a free ride aboard an Atlas V rocket as part of the agency's Educational Launch of Nanosatellites (ELaNa) program. Even though the Lightsail craft would be placed into orbit below the necessary 700-kilometer height, the Society decided to use one of their LightSails to test the mechanics of the sail deployment system.
Dubbed "LightSail 1," the sails successfully unfurled, as this selfie taken by LightSail 1 attests.
Image source: Planetary Society
And now LightSail 2
The second craft, now known and "LightSail 2," was slightly modified — particularly its software — according to insights gleaned during the first mission. It's scheduled as of this writing to go up from Kennedy Space Center in Florida later this month aboard a SpaceX Falcon Heavy as part of the U.S. Air Force's STP-2 mission from Kennedy Space Center in Florida.
This time, LightSail 2 will be carried within another, slightly larger satellite, Prox-1, developed by students at Georgia Tech. The Prox-1 will be placed into orbit around 720 meters up, and a week later will launch LightSail 2.
After a few days of diagnostics, LightSail 2 will open up its solar arrays, and then a day later, unfurl its sails. Over the next month, it will continually re-position its sails relative to the sun to raise its orbit — this is the main part of the mission, the actual solar sailing.
Mission complete, the craft will orbit for about a year before drag takes its toll, and LightSail 2 burns up plummeting down through the atmosphere. During this year, its position will be tracked via ground-based laser ranging, and it may be visible to the naked eye. The Society will offers an online dashboard that can tell you where and when to look up to se this most elegant spacecraft.