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2017 Nobel Prize in physics — our place in the universe

Yesterday the buzz started about the announcement of the 2017 Nobel Prize in physics.

Here’re some samples of articles on the joint award to three scientists. A testimony to research on the cosmic microwave background radiation (and understanding of the universe’s evolution) and advances in observational astronomy.

• Washington Post > “Nobel Prize in physics awarded for research on exoplanets and the structure of the universe” (October 8, 2019) > “Our view of our place in the universe will never be the same again.

By studying the earliest moments after the birth of the universe, [cosmologist] James Peebles of Princeton University developed a theoretical framework for the evolution of the cosmos that led to the understanding of dark energy and dark matter — substances that can’t be observed by any scientific instruments but nonetheless make up 95 percent of the universe.

Fellow laureates [astronomers] Michel Mayor and Didier Queloz of the University of Geneva revolutionized astronomy, the Nobel Committee said, when in 1995 they announced the discovery of a large, gaseous world circling a star 50 light-years from our sun — the first extrasolar planet found around a sun-like star. In the decades since, scientists have detected thousands more of these exoplanets, and astronomers now think our universe contains more planets than stars.

• CNET > “Nobel Prize in physics: 2019 winners made significant cosmological discoveries” (October 8, 2019) > “The award goes to a trio of scientists for giving us a new understanding of the universe.

Half of the award went to James Peebles, a physicist with Princeton University, for developing a theoretical framework that traces the the history of the universe, from the Big Bang to present day. His contributions to the Big Bang model and other work led to insights that just 5% of the universe is known matter — everything from stars to plants to humans — and the remaining 95% is unknown dark matter and dark energy.

The other half was jointly awarded to Michel Mayor, an astrophysicist with the University of Geneva, and Didier Queloz, an astronomer with the University of Geneva and University of Cambridge, for the first discovery of a planet outside our solar system. In October 1995, the two scientists discovered the first exoplanet in the Milky Way, planet 51 Pegasi b. Since their initial discovery, more than 4,000 exoplanets have been found in our home galaxy, according to the Royal Swedish Academy of Sciences.

• Space.com > “Nobel Prize in Physics Honors Scientists Who Transformed Our Ideas About the Cosmos” (October 8, 2019)

The Nobel Prize in physics has been awarded to three scientists for unraveling the structure and history of the universe and for changing our perspective of Earth’s place in it.

Canadian-American James Peebles of Princeton University received one-half of the Nobel “for theoretical discoveries in physical cosmology,” the Royal Swedish Academy of Sciences said this morning. The other half will be shared by Swiss scientists, Michel Mayor and Didier Queloz, “for the discovery of an exoplanet orbiting a solar-type star,” the Academy said. Mayor is a professor at the University of Geneva in Switzerland, and Queloz is at both the University of Geneva and the University of Cambridge in the U.K.

Mayor and Queloz announced the first discovery of an exoplanet, or a planet outside our solar system, orbiting a sun-like star in October 1995. Using custom-made instruments at the Haute-Provence Observatory in southern France, the duo was able to see 51 Pegasi b, a gas giant comparable to Jupiter, according to the Nobel Prize organization.

• SmithsonianMag > “Three Win Physics Nobel for Showing Our Place in the Cosmos” (October 9, 2019) – Half goes to cosmologist James Peebles for work on cosmic background and dark matter and half goes to the team that discovered the first exoplanet

“This year’s Nobel laureates in physics have painted a picture of the universe far stranger and more wonderful than we ever could have imagined,” Ulf Danielsson of the Royal Swedish Academy of Sciences said while announcing the winners. “Our view of our place in the universe will never be the same again.

Michael Turner of the University of Chicago and the Kavli Foundation tells the New York Times’ Kenneth Chang and Megan Specia that Peebles has been a leader in almost all of the key discoveries in cosmology for over 50 years. “Jim has been involved in almost all of the major developments since the discovery of the cosmic microwave background in 1965 and has been the leader of the field for all that time,” he says.

CalTech physicist Sean Carroll tells the Associated Press’ Seth Borenstein and David Keyton that Peebles’ win is likely the first Physics Nobel awarded for purely theoretical cosmology. In the past, most astronomy awards have been for observations of cosmic phenomenon. But Peebles work and the tools he created enabled much of the work that has taken place in the last half century.

In the 1960s, what cosmologists knew about the universe was rudimentary, the Times reports. Cosmologists didn’t know how far away objects were, how old the universe was, or how it is structured. Most ideas were just guesses that varied from scientist to scientist.

• Wired > “How Two Nobel Laureates Spotted the First Exoplanet” by Rhett Allain (October 9, 2019) – Swiss scientists “started a revolution in astronomy” by noticing a tiny stutter in the starlight.

We didn’t even know if planets were common or rare in the universe—a question with big implications for the possible existence of alien life.

It was quite a feat of scientific sleuthing. Mayor and Queloz looked at a star in the Pegasus constellation called 51 Pegasi, which is 50.45 light years away. We can see the light given off by the star, but at that distance the angular size of the source is too small for telescopes to resolve. In other words, we can’t really see the star itself. And if you can’t see the star, you certainly can’t see a much smaller planet circling it.

So how’d they do it? With physics, of course. As with all things, the best way to understand it is to build a model. So, let’s construct a simple model of the first exoplanet ever detected. [Diagrams and Python software script included in article for calculating star’s wobble – change in velocity due to gravitational interaction with orbiting planet.]

That looks like a big fluctuation only because the scale on the y axis is so tiny. Look closely and you can see that the [starlight] wavelength ranges between 500.00000 nm and 500.00031 nm [from Doppler shift due to changes in star’s veocity]. That’s an extremely small shift, and thus it’s very difficult to detect. But wait—it gets worse! We’re assuming the star is wobbling toward and away from us. But what if the planet’s orbit shakes the star up and down with respect to Earth? In that case, we wouldn’t see any wavelength shift. We’d never know there was a planet there.

Sound challenging? Now you know why it took until 1995, and why Mayor and Queloz are being honored for their achievement. The Nobel Prize committee said they “started a revolution in astronomy.” Indeed, using the method they pioneered, along with some other creative techniques, astronomers have since detected more than 4,000 exoplanets in the Milky Way. Who knows, we may yet find one with its own brilliant scientists.

• Phys.org > “Humans will not ‘migrate’ to other planets, Nobel winner says” (October 9, 2019)

Humans will never migrate to a planet outside of Earth’s solar system because it would take far too long to get there, Swiss Nobel laureate Michel Mayor said Wednesday.

“If we are talking about exoplanets, things should be clear: we will not migrate there,” Mayor told AFP near Madrid on the sidelines of a conference when asked about the possibility of humans moving to other planets.

Using custom-made instruments at their observatory in southern France, Mayor and Queloz in October 1995 discovered what had previously only existed in the realm of science fiction—a planet outside Earth’s solar system.

“These planets are much, much too far away. Even in the very optimistic case of a livable planet that is not too far, say a few dozen light years, which is not a lot, it’s in the neighbourhood, the time to go there is considerable,” he added.

“… We must take care of our planet, it is very beautiful and still absolutely liveable.”

The 77-year-old said he felt the need to “kill all the statements that say ‘OK, we will go to a liveable planet if one day life is not possible on earth’.”

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