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-------------------------- 2770 - EXOPLANETS - are we alone?
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- Calculate the number of alien civilizations in the Milky Way. Are you ready to do the math?
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- This is 2020 and over 4,164 exoplanet have been discovered. so far. With all those sister planets it has led to renewed interest in the timeless question: "Are we alone in the universe?"
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- With so many planets to choose from and the rate at which our instruments and methods are improving, the search for life beyond Earth is kicking into high gear.
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- These discoveries have inspired many new studies regarding the ongoing search for extraterrestrial intelligence (SETI). This includes the “Calculator’ to address the statistical likelihood of advanced life in our galaxy.
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- The Drake Equation Calculator expresses this probabilistic argument mathematically. Start multiplying the profanities.:
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----------------- N is the number of civilizations with which we could communicate
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----------------- R* is the average rate of star formation in our galaxy
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----------------- fp is the fraction of those stars which have planets
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----------------- ne is the number of planets that can support life
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----------------- fl is the number of planets that will develop life
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----------------- fi is the number of planets that will develop intelligent life
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----------------- fc is the number of civilizations that would develop transmission technologies
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----------------- L is the length of time that these civilizations would have to transmit their signals to space
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- While this equation was intended to stimulate debate about the probability of ETIs, it was also significant because of its basic implications. Even if one treats all the variables conservatively, they still get an “N” result in the dozens or the hundreds. Basically, even if life is very rare in our galaxy, there ought to be at least a few civilizations out there that we could make contact with.
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- The principle applied to the existence of life in our universe states that in lieu of other evidence, one should never assume that humanity is special or unique. When applied to the question of whether or not humanity is alone in the universe a more modern version of the Drake Equation is mathematically expressed as:
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------------------------------ N = N* * FL * FHZ * FM * (L/T')
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----------------- N is the number of civilizations we can communicate with:
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----------------- N* is the total number of stars within the galaxy
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----------------- fL is the percentage of those stars that are at least 5 billion years old
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----------------- fHZ is the percentage of those stars which host a suitable planet for supporting life
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----------------- fM is the percentage of those stars with sufficient metallicity, allowing for advanced biology and an advanced civilization
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----------------- L is the average lifetime of an advanced civilization
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----------------- t' is the average amount of time available for life to develop
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- Combined with the latest astrophysical data on these values, they came up with an average estimate of 36 civilizations.
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- Let's assume that the ACC told us that there were potentially hundreds of civilizations in our galaxy and that the nearest one is located about 159 light-years away.
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- Let us also assume we had a ship that is similar in mass to the ISS (420 metric tons, 463 U.S. tons) and that it could accelerate 1 g (9.8 m/s) until we reached 99% the speed of light.
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- Based on these variables, the Space Travel Calculator tells us that it would take 161.4 years to reach the nearest ETI, though only 10 years would pass for the crew (since we're using Einsteinian physics).
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- Apparently, the ship would also need about 11.66 million metric tons of fuel mass to make the journey. So yeah, that mission won't be happening anytime soon. But it was a fun exercise.
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- Exoplanet discoveries have given astronomers a good idea of how many stars have planets, and how often they orbit within a star's habitable zone. If we assume that an Earth-like planet would eventually form life.
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- It is widely assumed that since modern humans only emerged about 200,000 years ago (whereas planet Earth is over 4.5 billion years old), that SETI should only be looking at stars that are 4.5 billion years or older.
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- Predicting how many extraterrestrial civilizations are out there will continue to involve a lot of uncertainty. As time goes on, and the instruments we use to conduct SETI research improve, astronomers will learn more about these variables. From this, we can expect that estimates on the likely number of ETIs in our galaxy to become more tightly constrained.
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- Some significant developments need to happen before we can answer the question "Are we alone?" with any confidence:
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- We will get better at detecting Earth-like planets in the habitable zone and even be able to detect what's in their atmospheres (if they have one). This might lead to a more targeted SETI search, which should increase our chances.
- We could build a radio telescope on the dark side of the moon to get away from the radio noise of the Earth, enabling us to increase our sensitivity to any alien transmissions.
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- The search for ETIs will continue, and will benefit immensely from next-generation instruments, like the James Webb and Nancy Grace Roman space telescopes, and other new methods that are becoming available.
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- At the same time, probability studies and probabilistic arguments will help us narrow the search parameters. If they are out there, we are sure to find them eventually.
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- Over the next decade, 2020’s, several very powerful telescopes will come online. Observing time on these ‘scopes will be in high demand, and their range of targets will span a whole host of topics in astronomy, astrophysics, and cosmology.
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- How will astronomers know where to spend their precious exoplanet observing time? Planets form in debris disks around young stars. But it’s hard to see inside those dusty disks and spot the actual planets with the telescopes and instruments we currently have.
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- A recent survey targeted young stars less than 500 million years old. They were nearby stars, within 150 parsecs (490 light years) of us. There were 104 stars, including 38 that were previously imaged. The researchers were also able to resolve 26 debris disks and 3 proto-planetary / transitional disks.
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- It is often easier to detect the dust-filled disk than the planets, so you detect the dust first and then you know to point your James Webb Space Telescope or your Nancy Grace Roman Space Telescope at those systems, cutting down the number of stars you have to sift through to find these planets in the first place.
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- Looking at the images of the disks in this study is like looking at the Kuiper Belt in our own Solar System. The Kuiper Belt is a frigid area in the distant Solar System, 40 times further from the Sun than Earth is. The material in the Belt of rocks, ice, and dust was left over from the planet forming stage in our Solar System’s development.
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- The Kuiper Belt was named in honor of Dutch-American astronomer Gerard Kuiper, who postulated a reservoir of icy bodies beyond Neptune. The first Kuiper Belt object was discovered in 1992. We now know of more than a thousand objects there, and it’s estimated it’s home to more than 100,000 asteroids and comets there over 60 miles across.
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- The Gemini Study captured 26 images of debris disks around certain stars. Of those, 25 had holes in the disks, which are evidence of a young planet sweeping up gas and dust as it forms. Some of them were previously known, but seven of the 26 are newly identified.
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- One of the things that makes the “Gemini Planet Imager” so effective is its coronagraph. The venerable Hubble has a coronograph, which blocks the light of distant stars, making it easier to see other detail around the star. But it’s coronograph isn’t near as effective and high-tech as the GPI’s. Using its coronagraph, GPI is able to see to within one astronomical unit of the stars it targets.
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- The researchers used the GPI to look at stars that were exceptionally bright in the infrared. Not because of the output of the star itself. But because high infrared output indicates the presence of a disk, which emits infrared light. GPI is powerful enough to observe near-infrared light scattered by tiny dust particles no larger than one micron, or a thousandth of a millimeter.
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- One of the fascinating aspects of studies like this is what it might tell us about our own home here in our Solar System. What would it have looked like if it had been imaged in its infancy.
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- If you dial back the clock for our own solar system by 4.5 billion years, which one of these disks were we? Were we a narrow ring, or were we a fuzzy blob? Our Solar System is a relatively, calm, sedate place compared to most young solar systems.
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- There’s no way we’ll ever know what our own Solar System looked like in its infancy. But the same processes that formed our system are at play in every system. Ours might only be special because of our precious life-supporting Earth.
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- Our understanding of young stars, and the solar system that evolve around them is taking shape. Even ten years ago, we weren’t nearly as knowledgeable as we are now.
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- When our next generation of telescopes comes online over the next decade or so, our knowledge will grow by leaps and bounds. And this Gemini study will be part of it.
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- July 3, 2020 2770
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--------------------- Saturday, July 4, 2020 -------------------------
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