The Milky Way contains, at the very minimum, at least 100 billion planets, a new study from Caltech has concluded. That alone sounds like an enormous number, but when you consider that the Milky Way is just one of countless galaxies, the number of planets in the Universe must be nearly unfathomable.
The new research, performed by astronomers at the California Institute of Technology (Caltech), has provided further solid evidence that planetary systems, like ours, are extremely common. “The team made their estimate while analyzing planets orbiting a star called Kepler-32 — planets that are representative, they say, of the vast majority in the galaxy and thus serve as a perfect case study for understanding how most planets form.”
“There’s at least 100 billion planets in the galaxy — just our galaxy,” says John Johnson, assistant professor of planetary astronomy at Caltech and coauthor of the study, which was recently accepted for publication in the Astrophysical Journal.
“It’s a staggering number, if you think about it,” adds Jonathan Swift, a postdoc at Caltech and lead author of the paper. “Basically there’s one of these planets per star.”
“The planetary system in question, which was detected by the Kepler space telescope, contains five planets. The existence of two of those planets have already been confirmed by other astronomers. The Caltech team confirmed the remaining three, then analyzed the five-planet system and compared it to other systems found by the Kepler mission.”
“The planets orbit a star that is an M dwarf — a type that accounts for about three-quarters of all stars in the Milky Way. The five planets, which are similar in size to Earth and orbit close to their star, are also typical of the class of planets that the telescope has discovered orbiting other M dwarfs, Swift says. Therefore, the majority of planets in the galaxy probably have characteristics comparable to those of the five planets.”
This planetary system isn’t unique, but because of our view of it, completely edge-on, it allows us to easily detect the planets in the system. “Due to this rare orientation, each planet blocks Kepler -32’s starlight as it passes between the star and the Kepler telescope.”
“By analyzing changes in the star’s brightness, the astronomers were able to determine the planets’ characteristics, such as their sizes and orbital periods. This orientation therefore provides an opportunity to study the system in great detail — and because the planets represent the vast majority of planets that are thought to populate the galaxy, the team says, the system also can help astronomers better understand planet formation in general.”
“I usually try not to call things ‘Rosetta stones,’ but this is as close to a Rosetta stone as anything I’ve seen,” Johnson says. “It’s like unlocking a language that we’re trying to understand — the language of planet formation.”
How exactly the Kepler-32 system formed isn’t clear, but the researchers think that their analysis puts constraints on the possibilities. “For example, the results suggest that the planets all formed farther away from the star than they are now, and migrated inward over time.”
The researchers note that having such a large number of planets in the galaxy has important implications for people. “It’s really fundamental from an origins standpoint,” says Swift, who notes that because M dwarfs shine mainly in infrared light, the stars are invisible to the naked eye. “Kepler has enabled us to look up at the sky and know that there are more planets out there than stars we can see.”
Some more thoughts that:
“Various estimates have been made as to how many planets might support simple or even intelligent life. However, these estimates have large uncertainties, because the complexity of cellular life may make biogenesis highly improbable. For example, Dr. Alan Boss of the Carnegie Institution of Science estimates there may be a ‘hundred billion’ terrestrial planets in our Milky Way Galaxy, many with simple life forms. He further believes there could be thousands of ‘civilizations’ in our galaxy.”
This way of thinking of course ignores that forms of alien ‘life’ could be completely different than what is known as life on the Earth, or understandable to ‘humans’.
And many astronomers and researchers in the field seem to operate under a misunderstanding of what ‘evolution’ is. As much research has reinforced, there is no ‘evolutionary’ drive towards complexity, ‘intelligence’, or ‘civilization’. There is simply an appropriate adaption to changing circumstances and ‘participation’ within those circumstances, or extinction.
That way of thinking about alien life also ignores the possibility that life is extremely common, because it didn’t originate on the Earth. Panspermia and associated ideas could very well have truth to them, maybe ‘life’ began with the universe.
Image Credits: NASA/JPL/Caltech; NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger