Imagine a map on a computer screen showing the gravitational pull of nearby stars. Imagine a total pull so strong that it bends the Earth’s rotation.
Imagine, too, that there is a planet nearby, a gaseous world so dense that its core is filled with dense air, from which it could produce enormous bursts of high-energy radiation that could also warp Earth’s position. Now, imagine that the Earth is a solar system, orbiting a sun that is very similar to our own. This is what the first planet in this proposed solar system looks like, and it may contain most of the elements necessary for life, including oxygen.
This is the vision of Tom Barclay, a NASA scientist and leading expert on planets outside our solar system.
For the past five years, Barclay has spent time at NASA’s California Institute of Technology working on the follow-up to “Planet Hunters,” the citizen-science project that scientists began exploring the Milky Way with in 2011. That project relied on volunteers of all backgrounds to take detailed photographs of galaxies and catalog stars that they found to be the most common star in each of those galaxies.
Two years ago, the Planet Hunters volunteer team discovered a strange spectral signal that had never been seen before. Based on the best observations astronomers had ever gathered about the galaxy, the signal was clearly from a planet orbiting around one of its stars. But astronomers couldn’t find the planet using the most sophisticated telescopes in the world, such as Hubble or Spitzer. In the time that elapsed between then and now, an average citizen could have done the same work using their smartphones, Barclay says.
When a scientist was finally able to follow the Planet Hunters signal, he discovered a planet whose density closely matched that of our own planet. What’s more, in the presence of the planet’s sun, a hot planet, the star was barely flaring. In the universe as a whole, these signals from a small fraction of galaxies show strong, highly energetic bursts. If the planet were the star of a large nearby star, that flare would kill the planet. On Earth, the planet’s only chance of survival would be a quiet pull from another star that would gradually kill the planet.
“It was amazing to see,” Barclay says. “Now that we’ve got this confirmation, we’re going to try to get that information together in a way that’s low-effort. That’s what ‘Planetary Assembly’ is all about.”
Lorraine Lederman is a senior scientist at the National Research Council and co-chair of the 2017 meeting of the scientific community that was convened by the Academy of Sciences to consider the question of planetary assembly of planets.
“The expectations are quite high, and this is an exciting possibility to start with,” Lederman says.
The discovery, if confirmed, would be first of a solar system outside our galaxy. The second, as James Hansen of NASA’s Goddard Institute for Space Studies noted, would be the birth of the first planet outside our solar system.
Hansen has a theory of origin for our solar system: Our sun formed as the start of a new star around 13.8 billion years ago. He’s worked out a number of theories, such as the Big Bang, but has mostly been happy just watching the progression of our sun. He found the Planet Hunters signal much more satisfying than theory.
“It would be a fascinating surprise,” he says.