Life on Earth exists because of the sun and our distance from it. Without that star and the energy it gives off, we’d be what NASA once described as a “lifeless ball of ice-coated rock.” Luckily, we are far enough from it, and as of right now, it’s not radiating so much light as to make our planet uninhabitable. In some ways, we’re in the sweet spot, and researchers may have discovered many more such connections.
Stars in the Milky Way may have 100 billion planets — two, on average, per star — in their habitable zone, the area far enough from the star to avoid the planet getting scorched but close enough for it to potentially hold liquid water, according to new research from the Australian National University and the Niels Bohr Institute in Denmark.
That number, 100 billion, may seem beyond comprehension, but “this result is actually not controversial,” Steffen Jacobsen, a PhD student in Astrophysics and Planetary Science at Niels Bohr, told weather.com. Previous studies, he said, have predicted tens of billions of these planets. “In that sense, what we find is not surprising. Practically every researcher in the field expects there to be many, many planets in the habitable zone and many, many Earth-like planets.”
The potential for liquid water means the potential for life beyond Earth — assuming, that is, that water is as important to the evolution of life there as it was on our planet. “If you have liquid water, then you should have better conditions for life, we think,” Jacobsen said. “Of course, we don’t know this yet. We can’t say for certain.” Solving that mystery is part of the thrill for researchers looking for extraterrestrial life.
In this case, Jacobsen and colleagues used a theory called the Titius-Bode law for their calculations. They looked at 151 of the nearly 400 planetary systems NASA’s Kepler mission has collected data on, omitting systems with just two planets and focusing on those with four, five or even 10. Put simply, Titius-Bode says that within a single planetary system, a pattern exists in the distance between planets. In other words, “if you know where the four planets lie [in a five-planet system], then you can calculate where the fifth one will lie,” Jacobsen explained.
This is important because right now these planets are purely theoretical, and within the 151 systems, just 77 planets made the researchers’ short list for possibility of actual discovery.
Now it’s up to the field at large to comb through scores of data to determine whether Kepler actually has already spotted some of these planets and we just didn’t know it. “Some of these planets are so small the Kepler team will probably have missed them in the first attempt because the signals we get are so weak. They may be hidden in the noise,” he said. “You may miss them … unless you know where to look and unless you know what to look for.”
That, in a nutshell, is the crux of this work. “Our research indicates that there are a lot of planets in the habitable zone and we know there are a lot of stars like the one we’re looking at. We know that means we’re going to have many billions of planets in the habitable zone,” according to Jacobsen. If that’s true, “that would be very good news for the search for life.”
The research, “Using the inclinations of Kepler systems to prioritize new Titius–Bode-based exoplanet predictions,” was published Wednesday, Mar. 18, 2015 in Monthly Notices of the Royal Astronomical Society.
