A the stronomy is in the middle of a data revolution, a time of enormous discovery. Humans have been watching the stars for thousands of years, but modern telescopes and computers are rapidly accelerating our understanding. We know a lot more than we did 20 years ago, and now we are much closer to answering questions about whether life exists elsewhere in the cosmos, how our planet came here, our cosmic origins and final destiny.
clear night the stars shine in the sky and often we can see the luminous planets of our solar system in orbit, like us, around our sun. Until the beginning of the 90s, we had no idea if there were other planets around the stars in the sky. Astronomers suspected it, but they had no way of showing it. In the last decade we have found thousands of people in orbit around foreign stars and we have a better idea than they are common. A considerable fraction of stars probably have their own planets, their own worlds are brought around them in the most extraordinarily diverse solar systems.
Look at the stars, though, and you can not see any of their planets. They are tiny and do not give much light to them. Even with powerful telescopes it is difficult to see a planet directly, because the light of its parent star is otherwise brilliant. Instead, astronomers have come up with ingenious methods to find them. One is the "staggering" effect: a planet just makes its mother star oscillate as it orbits around it, the star feels a slight gravitational pull from the smaller planet. In 1995 Swiss astronomers Michel Mayor and Didier Queloz used the telescope of the Haute Provence Observatory in France to identify a star, 51 Pegasi b, which was swinging as expected. He revealed a planet similar in size to Jupiter, but so close to his star that it takes only four days to orbit around it, much faster naturally than the Earth or any planet in our solar system.
Astronomers have found a huge loot of planets using NASA's Kepler satellite, launched in 2009 and ending its spectacular mission in 2018. Kepler was designed to identify the planets crossing in front of their parent stars, looking for the slight darkening effect of the planet that blocks the light of the stars. Kepler has found thousands of planets in this way, including many whose complete orbit around their star takes only a few hours or days. Some are so close to their star that their surface must be entirely molten lava. He showed us solar systems with multiple planets and some planets orbiting around two stars: the "Tatooine" planets, which take their name from the imaginary house of Luke Skywalker. Some planets are larger than Jupiter, some are as small as our moon. Most were found by professional astronomers, but even amateurs found them, using pattern recognition to extract data online from Kepler's mission and capture planets that automated searches had missed. Now we think that there are more planets than stars in the sky.
We want to find out how likely a planet as habitable as the Earth exists and, even better, to find one. In the elusive "Goldilocks" zone, conditions must be correct: not too hot and not too cold. Astronomers have already found some dozens of planets like this, including at least three in the Trappist I solar system, found in 2015 around one of our nearest stars. Trappist I has seven planets, all similar in size to the Earth, and at least one has an ocean of liquid water. Studying these planets and some of the hundreds of millions of potentially habitable planets in our Milky Way galaxy is the goal of ambitious new projects. The NASA's Transite Exoplanet Survey Satellite (Tess), launched in 2018, is expected to find more than 20,000 new planets. The most interesting will be examined in greater detail by the James Webb Space telescope, the successor of the Hubble Space Telescope, due to the flight in 2020.
The stars in the sky host this wealth of solar systems, but also have a vital role to play as the large factories of nature. Consider gold: where does it come from? Astronomers have long wondered how gold has become part of the Earth's ingredients. We know that it is the stars themselves that make what our bodies are made of, including mainly carbon and oxygen. The British-American astronomer Cecilia Payne-Gaposchkin elaborated for the first time in the 20s that the stars are mostly just hydrogen and helium. The intense heat in the heart of the stars can melt these small atoms together into the slightly larger ones, which are then expelled into space when the stars explode at the end of their life. These recycled remains will later be present at the birth of new stars like our sun and will eventually create new planets like ours. But the alchemy of making gold has long been a mystery. Gold has much larger atoms than carbon and oxygen and can not be created in the nucleus of a star. The explosions of individual stars could create some, but not enough
In 2017 astronomers concluded that another way in which gold is generated is during intense collisions of neutron star pairs. Neutron stars are the strangest of nature. They are incredibly dense, the result of crushing a star bigger than our sun in a space a few miles away, after it has been left without fuel that made it burn bright. A spoon of neutron star weighs as much as a mountain. We can not see them with normal telescopes, but they emit radio waves. The stars circle around and, if oriented to the right, their radius of radio waves sweeps away the Earth regularly, like a beacon lighthouse. The astronomer Jocelyn Bell Burnell discovered for the first time one of these stars in November 1967 using a radio telescope built by her (with Anthony Hewish) as a doctoral student at the University of Cambridge. The pulses of the radio waves she had seen from the star were so regular, that they came every second, which they initially called LGM-1 for "Little Green Men", joking for half considering it could be a signal from the aliens.
a pair of these neutron stars hover around the other, their gravity is so strong that it deforms the weft of space-time itself. A gravitational wave ripples towards the outside, subtly shrinking and then expanding the space and everything inside it, over and over again, as it passes. On 17 August 2017, the observatory on the gravitational laser interferometer in the United States (Ligo) and the Virgo detector in Italy experienced an outbreak of these waves passing through the Earth. Using lasers to measure the precise length of two 4 km long tubes positioned at right angles, they directly measured the small squeezing and stretching of the tubes. For the first time they were perceiving two neutron stars, capturing the last two minutes of their lives as they turned thousands of times around one another before colliding.
The Ligo and Virgo teams immediately alerted astronomers from around the world, so they could look for consequences. It was still during the day in Hawaii and Chile, home to many of the largest telescopes, so they had to wait until late at night. The astronomer Ryan Foley and his team from the University of California at Santa Cruz were the first to locate a burst of light coming from the collision, using the Swope telescope at the Las Campanas Observatory in Chile In turn, they alerted the community so that other telescopes could swing to take a closer look. In the end it was seen by 70 observers on all seven continents and from space. What they had discovered was a kilonova and by studying the explosion, astronomers could say that it had produced enormous quantities of gold and platinum, much more than the entire weight of the earth. That particular collision took place too far to have produced gold on the finger, but in the end it was the decisive proof that a collision closer to that of the house could have created the Earth's gold.
The stars, source of heat and light and of our very bodies, give an impression of permanence. Here they are, night after night. However, we already know that they will change. Their positions in the sky will gradually shift, as our solar system moves around the Milky Way galaxy, our biggest billions of stars home. And in the end they will stop burning bright, and new ones will be born. Within astronomy, my particular expertise is cosmology, in which I ask questions about the life story of the whole universe. As a professor at Princeton University, I also teach university students and instruct young scientists to ask and answer their questions about the cosmos.
At the end of the twentieth century astronomers had begun to consider a great change at the horizon. If we look beyond our galaxy of the Milky Way, we find a sea of galaxies, each a collection of billions of stars, disseminated in space. A century ago, astronomers Edwin Hubble and Georges Lemaître have shown that galaxies are moving away from one another on average. Space itself is growing. But the attraction of the gravity of all the galaxies one towards the other should tend to slow down the growth of space, just as a ball thrown into the air stops and then falls back down again. . So the astronomers turned to wonder if the space would one day stop growing altogether and then start to shrink. Billions of years in the future, could all galaxies fall one against the other, invade our cocoon of local stars and mark the end of the universe as we know it?
The key to responding to this situation was to measure how fast space is growing and comparing it with its growth in the past. Of course you can see in the past looking far into space, in places where the light started a long time ago. Using a series of telescopes in Chile, Hawaii and the Canary Islands, rival teams of astronomers have made new measurements of distant galaxies, using extremely bright explosive stars as cosmic markers. The teams, led by Brian Schmidt at the Mount Stromlo Observatory in Australia, and Saul Perlmutter at the University of California at Berkeley, measured galaxies whose light rose up to 7 billion years ago. In 1998 both announced the same astonishing discovery, which was that space was not slowing down at all. Instead, the galaxies seemed to move away from each other faster and faster. It was strange as if I threw a ball in the air, and it would accelerate and move your hand away from the sky. In the early 2000s, other measurements of the universe were telling the same story, and in the last decade the tests became incontrovertible. We still do not know yet why this is happening. Astronomers refer to whatever it is causing as "dark energy", a form of energy that we have not yet identified. It could be the energy of the empty space itself, or something completely new. It is a mystery waiting to be solved.
This new discovery means that we no longer expect all galaxies in space to crash into us again. We're probably safe from that fate. But our Milky Way is still on a collision course with at least one other galaxy. We are flying towards Andromeda, the galaxy closest to the Milky Way, at a speed of over 50 miles per second, and we can not go back. In a few billion years, we will inevitably collide and mix our stars together. Every living thing in our solar system will see a spectacular change in the night sky when it happens, but the spaces between the stars are so large that it is unlikely that anyone can physically collide. Our sun will simply be part of a bigger house.
This future vision of our cosmos, our revolutionary discoveries of new worlds around the stars and our understanding of how the inner workings of the stars create the fabric of our lives are just some of the exciting discoveries of this century. A common thread is that the great advances of astronomy bring groups of scientists working together, using telescopes all over the world and in space, coupled with powerful computers. The questions we are asking ourselves can not, for the most part, be solved by people who work alone. As a result, the community is international. Meet an astronomer anywhere in the world and most likely are asking the same questions about the existence of life elsewhere, our place in space and the cosmic history of how we got here. And with the birth of many magnificent new telescopes for the next decade, we can expect together to take further steps forward in our understanding of the night skies and the larger universe over the next 20 years. We know, based on past experience, that the most exciting discoveries will probably be the ones we least expected.
• Our Universe by Jo Dunkley: An Astronomer & # 39; s Guide was published by Pelican on January 31st.