infrared

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If photons are infrared, that is, they have a bigger wavelength, it will be harder for them to be absorbed and cross the nebula. Therefore, looking at the infrared with telescopes specially designed for this purpose allows us to see through the dust and interstellar gas, towards the stars that are beyond the nebulae.

absorption in an interstellar medium

visible light

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If photons that try to go through the gassy cloud have wavelengths of the visible spectrum, they would end up been absorbed by the cloud. The energy of these photons would be transferred to the cloud, and as such its temperature rises; these photons end their trip here. This explains why nebulae are similar to veil and hide their visible light form the stars behind them.

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The interstellar medium

During an interstellar travel crossing our galaxy a photon will pass by gas clouds, which are the places where new stars are born. The wonderful Orion Nebula is an example of these clouds.

infrared

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photons from a exoplanet

Despite the fact an exoplanet does not give off visible light, it does give off infrared light, which our eyes cannot see, but our telescopes can! In this case the photons we watch are produced directly on the surface of the exoplanet and thus are easier to catch.

visible light

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Photons from a Star

Photons emitted by a star bounce off the exoplanet’s atmosphere. To detect these kinds of photons is very difficult due to the fact that among all the photons emitted by the star, only a few reach the exoplanet, and of these only a few bounce towards the Earth.

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exoplanet

alpha Centauri B

proxima Centauri

If the photons are produced by other stars that aren't the sun the time that takes them to reach Earth is longer. For the star closest to the Sun, Proxima Centauri, photons need more than 4 years to get to the Earth.

detecting photons from an exoplanet

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Birth of a photon in the Sun

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photosphere

fusion: Is the process in which two Hydrogen atoms unite to form a Helium atom. A sub product of this reaction is a photon, which is released when both Hydrogen atoms fuse.

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hydrogen

Helium

The interior layers of the Sun are very dense and full of atoms, which means that the photon will bounce in all direction and will start to lose energy.

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A photon will need between 10,000 to 200,000 years to get to the photosphere, despite its incredible speed of 300 000 km/s. Finally, in eight minutes and 20 seconds it will reach the Earth, which is located 150 million km from the Sun.

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Dispersion in the atmosphere

The photons that arrives form the Sun are dispersed by atmospheric molecules (changing their original path). Because of this, the sky shines every time at day in all directions.

Los fotones azules son mucho más propensos a ser dispersados, debido a que su longitud de onda es más corta, por esta razón, durante el día, vemos el cielo azulado y brillante.

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Sun

Refraction

A Phenomenon that happens when photons are divered from their original path when they cross a drop of water.

The deviation angle depends on the wavelength: blue photons are more diverted than the red. So, all colours are separated and we can see the rainbow.

Sol

The photon and the visible light

Photons are produced by the Sun, by stars and also by a flash of a camera

The human eye its only capable to sense the part of the photon's spectrum, those are the photons that compose the visible light.

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Camera
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Different wavelength
Its symbol is gamma: (𝛾)

300.000 km/s

Speed in empty space

Photon

It's a massless particle, that travels at speed of light, besides being a particle, it is an electromagnetic wave.

Hombre

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journey of the photon

Have you ever wondered why the sky is bright during the day? Have you noticed that the blue sky is not even? Do you know what a rainbow is and why we see it that way? These and other fascinating phenomena are closely related to light, more precisely to the particles that form light: photons. Let's follow the mapping of some photons sent out from different places in the Universe to the thin atmosphere layer that surrounds our planet, so as to understand their behaviour and some of the phenomena that they cause. But before, let's try to understand some things about this particle.