As I regularly state, I am an experimental atomic, molecular and optical physicist, meaning that this year's Nobel Prize in Physics for Cosmology and The Discovery of extrasolar planets is what I normally endure.I'm glad to leave detailed descriptions of what the three new winners in the capable hands of Ethan "Starts With A Bang" Seals have done, is an indirect connection to my field of research, which is one
The half Nobel Prize split by Michel Mayor and Didier Q ueloz "for the discovery of an e xoplanet orbiting a solar-type star" is based on the "radial velocity method" to detect planets in orbit around another star. This takes advantage of the fact that while stars are much larger than planets – the mass of the sun is millions of times the size of the earth's mass – they are not fixed in space. The gravitational force between a star and a planet affects both bodies equally, which means that they both move in response. The orbit of the planet is much more dramatic thanks to the smaller mass, but the star also traces an ellipse that is complementary to the orbit of the planet but much, much smaller.
This means that a orbiting exoplanet makes its home star. Wiggle lightly and give it a speed along our line of sight that changes as orbit progresses – first slightly towards us, then slightly away, then up again us and so on. If you can measure that speed, you can analyze it to extract all sorts of information about the size and shape of the orbit, the mass of the planet, and so on.
(There is another complementary method of detecting exoplanets, which is to look for the slight obscuration that occurs when a planet is placed between us and its star, which was not included in this Nobel Prize Basis of a future price.)
How do you measure this speed, considering that the stars are many light-years away and you can not make them glow with a radar? Well, you use the Doppler effect, a shift in the frequency of a wave that depends on the relative velocity of the source, which is the physics behind the "EEEEEEEEE-OWWWWWWWW" noise, even surprisingly small children Knowing that it's a fast-moving car: when a car moves toward you, engine noise is shifted to a higher pitch ("EEEEEE") and lower pitch when it drifts away (the "OWWWW"), and just as it happens, it quickly changes from one to another.
The same physics applies to light waves, but because the speed and frequency of the light are so much higher, the size of the displacement is G is far less obvious: for visible light with a wavelength of about 500 nanometers emitted by a star moving 1 meter per second (a not unreasonable standard for interesting planet-star combinations), the frequency change is about three Billionth of the frequency of light, compared with a shift of about 10% of the frequency of radiated sound waves A driving car.
How do you measure such a small layer? Very, very carefully – that's why it's worth a Nobel Prize. Atomic, molecular and optical physics also come into play here, because we make painstakingly accurate measurements of light frequencies.
There are two pieces you need for radial velocity measurement: First, you need to know the frequency of the light emitted by the star very well, and second, you need to know the frequency of the light that you use very much well know, know. In both cases, this depends on the quantum physics of the atoms: every atom in the periodic table absorbs and emits light at a discrete set of frequencies equal to the energy difference as electrons move between quantum states. This means that the light of a lamp, which contains a specific element and is fed into a spectrograph, creates a unique set of narrow, bright lines. Starlight with a wide frequency spectrum that passes through a gas sample is absorbed in narrow areas, which appear as dark absorption lines – essentially shadows – when fed into a spectrograph.
These spectral lines are like we Identify the composition of distant objects in the Universe by matching their emitted and absorbed light frequencies with those known from elements measured here on Earth. That's also what Mayor and Queloz (and many other people) used to determine the speed of distant stars: they found lines that could be identified with certain elements here on Earth, and watched them for tiny frequency shifts that coincided with changed the time. Again, the displacement they sought was tiny, but they could challenge them by following many lines. In the first article about their discovery, they said that they used about 5,000 different lines in the visible spectrum. Without the careful spectroscopic measurements that enabled the identification of all these lines, they would not have been able to do so.