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Looking For Jupiter-Class Planets Indicates Solar Systems Like Ours Are Rare (theconversation.com)
An anonymous reader writes: A high school senior from New York analyzed data for more than 1,100 stars and pinpointed the frequency of Jupiter analogs (planets with similar mass and orbital period to Jupiter) to 3%. He published his results in a paper for the Astrophysical Journal. The relative rarity of Jupiter-like planets indicates that true solar system analogs should themselves be rare. By extension, given the important role that Jupiter played at all stages of the formation of the solar system, Earth-like habitable planets with similar formation history to our solar system will be rare.
It's rather premature to declare all those systems devoid of planets when our primary means for detecting possible planets is when they pass between our planet and their star at the same time we observe them. Jupiter takes 12 years to make an orbit. As a simple logic problem, that means that we have to one opportunity to observe Jupiter passing between Sol and some sort of earth-analog in another system.... and that makes the HUGE assumption that that earth-analog is aligned with the solar system's orbital plane. If the earth analog happens to be staring down north-south on Sol, it isn't going to detect any planets.
There are a few other ways to detect planets, but those are special cases, again, very rare, and detecting very unique planets.
Detecting Sol-like systems is still extremely difficult.
Jupiter has an orbital period of 12 years. From what I've understood it takes 3 passes to confirm an exoplanet, meaning 0-12 years to initial discovery + 2*12 = 24 years for a Jupiter-class planet. It's only been 23 years since the first exoplanet was discovered in 1992 and detection capability has improved much since then, so it's way too early to tell. Maybe you can start making semi-educated guesses from lack of candidates, but that too seems premature. In another 15-20 years, we'll have much better answers.
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At roughly 3%, that means about 100x as many Jupiter analogs in our galaxy as there is carbon dioxide in our atmosphere (by percentage).
At roughly 3%, that means there are only about 10 billion Jupiter analogs in our own galaxy of roughly 300 billion stars.
Yes, 'rare' is a relative word especially when you are dealing with numbers that seem to be beyond human comprehension.