Extraterrestrials - Why They're Almost Certainly Out There... | Chris Crowe | TEDxJohnLyonSchool

Planet Earth is an incredible place, our Sun provides energy for all our habitats, our climates and the millions of species of life that live here, but is the Earth the only one for thousands of years, humanity has wondered, given the immensity of the space, could there be another Earth out there? Which could be home to intelligent life As an astronomer, this question has always fascinated me as a child. I often lay awake in my bed late at night wondering, given how vast the universe is, could there be other life forms driven in their beds wondering the same thing until the 1990s, when there were no other planets orbiting around other stars.

Today I would like to share with you what we now know about the distant Earth. How many do we think there are out there? How many can have the conditions for life and why? I'm sure

they

're definitely out there somewhere, even if

they

never say that our amazing solar system is home to eight planets. Nine If you feel bad about downgrading Pluto to a dwarf planet, only one of these planets is close enough to the Sun to melt ice into liquid water, but not too close to boil water into steam in the atmosphere. If our planet were significantly smaller, the solar wind would strip away our atmosphere, leaving it inhospitable to life as we know it.

If the Earth were much larger, it would be hotter. and more volcanic, we would all be stronger, slower and heavier, and because the pull of gravity will be much stronger, we would all have our feet on the ground, life has evolved to adapt to a wide range of conditions in the earth, from high pressure. from the trenches at the bottom of the oceans to the snowy peaks of mountains, if it can evolve in such a wide range of environments here, maybe if it forms in other places it can also evolve, etc., how many planets could this be? possible in our universe? orbiting a distant star is called planet EXO.

One way we can detect these exoplanets is by looking for the small dip in brightness that we see when the planet passes in front of its star. Every time the planet completes its orbit, we observe the same fractional decay. In brightness, the chance of seeing this drop in brightness is quite small because the planet and the star have to be perfectly aligned from our point of view, but if we are looking at millions of stars, at least some of their planets will be in the correct place. At the right time, for a distant alien looking towards our Sun, the probability that it will see Earth, Mars or Venus, passing in front of our star is about 1%, which means that the chances we have of observing a system similar planetarium around a distant star.

It's about the same about 1% NASA's Kepler satellite spent

almost

10 years observing the same patch of sky looking for these small variations in brightness. Kepler was retired last year on the 388th anniversary of the death of Johannes Kepler and had discovered more than two thousand five hundred exoplanets, these planets could be smaller than Earth, although even larger than Jupiter, but what is even more surprising that the planets he discovered are all the planets he overlooked if we apply this idea of ​​the fortunate alignment of the planet and its star to all the data about the exoplanet discovered so far we see that in our part of the Milky Way there is approximately the same number of planets than stars.

The most recent count is about 4,000 exoplanets discovered and we now know that a small fraction of them contain water. When a planet passes in front of its star, light from the star will shine through the planet's atmosphere, but not all of the light will pass through the atmosphere, it will absorb certain frequencies of light, this gives us a clue about the chemical composition of the atmosphere. and We can obtain a unique signature of water in the atmosphere of these distant planets last year. NASA announced the discovery of water vapor in the atmosphere of the planet Wasp 39b.

Wasp 39b is a huge Saturn-side planet nearly 700 light-years from Earth, where the sunny side reaches a scorching 800 degrees Celsius. This temperature will be too high for life's proteins to form as they have on Earth, but this study is a great demonstration of how we can accurately identify and locate these aquatic worlds last month, a team from Canada. and a group from London shared their findings when they used the Hubble Space Telescope to observe an exoplanet with the catchy name k2 18b that passes in front of its home star every 33 days k2 18b is about 100 light years away and is about eight times its size. size. of our planet Earth, which is why it is considered a super Earth.

KCU 18b is the first exoplanet we have detected that has water in the atmosphere but in the habitable zone around its star. So how many planets should we expect to have water? Hydrogen and oxygen Hydrogen is one of the fundamental components of the universe formed in the Big Bang 14 billion years ago. Oxygen is formed in the cores of stars through nuclear reactions. As stars evolve and die, they can distribute their oxygen throughout the galaxy, which can then continue to form water with hydrogen. Studies show that most of the oxygen in our galaxy is in the form of water or carbon monoxide.

A study published in 2018 by a group in the US showed that 35% of all exoplanets are larger than Earth. should be watery ocean worlds, this claim can be tested with a generation of exoplanet satellites in the neck, such as the transiting exoplanet survey satellite that was launched last year. These super-Earths are something like small versions of Uranus or Neptune. Thick atmospheres of water vapor covering vast oceans at extremes. Temperatures and pressures What does this mean for our galaxy? The most recent count of the number of stars in our galaxy is between 200 and 300 billion. A huge number. How can you visualize 200 billion?

Imagine filling a tennis court about a meter deep with the sand you need. about 200 billion grains of sand We now know that one in five Sun-like stars hosts an Earth-sized exoplanet in the habitable range around its star If one in five stars is like our Sun, that means Our Milky Way could host tens of billions of potentially habitable Earth-sized planets is incredible, so next time you look at the thousands of stars in the night sky, the nearest Sun-like star with an EXO planet similar to Earth in the habitable zone is probably only 20 light years away. away and can be seen with the naked eye.

It seems incredible to me, but what does this mean when we grow even more? Our universe is full of beautiful galaxies. This image is from Hubble's ultra-deep field, a composite of about ten years of data taken in a chunk of space about the same size as the head of a pin held at arm's length. This image published last year contains more than 15,000 galaxies. If each of these galaxies has on average a composition similar to that of our Milky Way, that means there could be more of them in our part of the universe. of ten quadrillion trillion potentially habitable Earth-sized planets is incredible and the real number is likely ten times greater because these are only the ones that can be seen with the Hubble Space Telescope ten quadrillion trillion is a huge number If you fill the entire UK with several meters of sand, it takes about that many grains of sand, so it's an exciting time to be alive.

All of the data and studies I have mentioned today are publicly available and can be downloaded for free online with tools to visualize and process the data. Astronomy is now a very data-rich science, there is always more data than there are scientists available to process it. One of the things I've tried to do as a teacher is encourage students to enjoy physics and astronomy so they can download the data themselves and try playing with it. Try to resolve some of these unanswered questions in this exciting field. I will encourage all young people to try to get involved in this exciting field game with data.

Access some of these problems yourself and try to answer some of these unsolved mysteries. In short, we have now discovered over 4,000 exoplanets in our part of the Milky Way. We think that about 10% of the stars in our Milky Way could host an Earth-like planet in the habitable range that could have liquid water. Could there be life? on any of these planets, well, I think we're tantalizingly close to answering that question, but if I had to bet, I'd use the words of Benjamin Franklin and say it's safer than death and taxes, thank you.