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contenidos

  1. The trip of the photon

  2. Planet formation

  3. How stars are born

  4. A cosmic dance

  5. The ages of the Universe

  6. The sky and its stars

  7. Wenulewfv the word that dream us

  8. The observation of Light

  9. A window to the Universe

  10. An astrophotographer in Santiago Chile

  11. Mysteries of the Cosmos

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editorial

THE MEMORY OF THE RIVERS
While the sweet scent of the canelo
and the laurel medicine trees
rose to the skies
the Parents of my Parents glimmered
as they gazed at the Southern Cross.

Elicura Chihuailaf
Translation: Camila Yver

Cities gather us in different ways, we dwell them, walk around its streets and avenues attending our own eagerness. Many cities have rise over us with huge buildings that show the ability of societies to overcome our scale, and so in a display of phenomenal energy, cities keep moving.

Now days, electric light seems to be a primary need for todays society. Cities and their lights shine over the night sky, blinding our eyes of the ordinary exercise of looking to the starry night that practice our ancestors. Those who have been in the Atacama Desert know that once is late night, looking at the stars there is a different experience, from the one we are used to when we look at the stars from our “shining” cities. This thought becomes most significant while we start to think about our everyday experience. Have we lost something in the way?

Our culture as human beings, have always been related to the night sky observation. Today, new planetary systems are discovered weekly, observation tools and instruments are increasingly sophisticated; we can look at the origin of the Universe and make an image of it. We live in a fast and fascinating era in which we can dazzle with images of supernova’s explosions, nebula clouds and faraway galaxies. The understanding of what “surround us” changes radically and Astronomy raises new questions, challenging the limits of our comprehension. Now we can look farther and farther and so wider the horizon becomes.

Facing this prospect, we propose to add different points of view. Contributing to the astronomical reflection from different angles, being the scientific perspective one in many others possible. Because we are interested in poetry, music, art and design, also in casual conversation, laughter, awkwardness and contradictions, in things that move and those who stay quiet, we are interested in large and small questions of humanity.

This first edition of Galatic Magazine is the number cero and has as main subject the Birth, the origin of things and also the origin of this project. This is a starting point of a conversation that we hope will spread in time, and so will convene many voices and many views.

Javier Quintana

Galactic Magazine
08

The observation of Light

TEXT Ignacio Toledo

ILLUSTRATION Toro

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Science is a discipline that looks after the comprehension of the Universe that surrounds us. The understanding of this matter is gotten by the observation and the conception of hypothesis or theories that could explain what we have watch during the observation and validate, rectify or modify hypothesis already formulated.

There are different areas that form part of science. Some areas like biology or chemistry, for example, can keep up a research in controlled conditions with possibilities of repeating several times a specific test, making the work more manageable and with the possibility to make every measurement and observation that’s necessary. No often, for Astronomy is not that easy to make these kind of experiments: it’s not possible to move planets as we would like, or travel through the stars to take samples or pick-up material from a gas cloud to be analyzed in a lab. How could we try to understand the Universe by the scientific method, if what we want to study and comprehend is beyond our reach?

This answer was several points: first we need a method to study the universe by scientific observation; secondly, we have to develop interpretation models that could explain what we see; third, we need a system that could validate, or not, these models. The Light Observation, it’s a systematic process that gathers light followed by the analysis of the information obtain from the sky, this is the main tool that astronomy has for the first part to be accomplish. Today’s huge telescopes and observatories are a clear sign of this process.

To understand how relevant is the Light Observation for Astronomy, we could start with Richard Feynman’s analogy. Let’s imagine an insect in the edge of a swimming pool, which its only sensitive to the water waves, because it doesn’t count with other kind of sense like sight or hearing. In moments of calm there aren’t waves in the water and for the insect is the same feeling we live when we are in a dark room, which means, that the insect has no clue of what is around him and can only assume that nothing is happening in the pool.

Suddenly, another insect fells somewhere in the pool, and so small waves are produced, our insect can now detect these waves, and can also obtain information of what its happening in the entire swimming pool. Then, our insect starts to catch different waves in the water that come from different directions, these waves are very similar to the waves made by the first insect that fell in the water, son now he assume that many other insects have fell in the swimming pool. After this happens, huge waves with different characteristics are affecting the water: A person has just dive into the pool! Also waves made by kids playing around in the water are different, if some one is swimming around, changes also if the size of the pool is different or if the insect is in the sea.

The light is an amount of waves, but in the space not in the water. These are electromagnetic waves and despite these have different physical characteristics as the water waves, the electromagnetic waves have a similar behaving than the waves described in Feynman’s analogy. These waves are produce instead by objects and events that occurred in space, which we are able to catch and read into. The electromagnetic waves also have different “shapes”, depending the kind of event, incidence or circumstance that produced the waves. Humans are capable to see only some electromagnetic wave length, known as visible light, while other waves can’t be sight.

In this image, the red points mark the amount of times that the wave oscillates in one second. Also, if we measure the distance between each red point, we will get the wavelength.

It is very important to distinguish the shape of the light, to infer the kind of event that produced it. For this astronomers use two different wave properties: length and frequency. The wavelength is the distance between two maximums and two minimums in a waveform, while the frequency is the amount of times that the wave oscillates in one second (Hertz). Length and frequency are then the attributes that help us to describe and define the type of light we are studying.

These two attributes are related by a constant: the speed of light, therefore we could use both mutually. The relation between these two it is explained in this scientific formula:

c = η × λ

Speed of light is c, which is approximately 3×10⁸ meters per second, the light’s wavelength is λ (lambda) measured in meters, and η (nu) is the frequency measured in Hertz.

The light it is showed to us in different ways, which allow us to talk about different types of light, that goes from the highly energetic Gamma ray with an extremely short wavelength and at the same time, an extremely large frequency (high temperature), to Radio waves that have large wavelength and consequently a very short frequency (low temperature). The light characterization allows us to describe a variety of physical and astronomical events that are related to the range of the waves. Therefore, we could define the optimal conditions where the observatories must be located in relation to the atmospheric conditions, the altitude and the type of telescope accurate to catch each electromagnetic wavelength. There is a range within the electromagnetic spectrum that do not gets through the atmosphere, in this case we say that the atmosphere is opaque to them. Because of this reason, telescopes must be installed in satellites that are beyond the atmosphere. Here we explain the electromagnetic spectrum with its main range and characteristics.

Electromagnetic Waves

Microwave & Radio

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MILKY WAY
Credits: ESA Planck LFI and HFI Consortia (2010) & Haslam et al
Frequency:

Less than 3×10¹¹ Hz

Wavelength:

More than 1×10ˉ³ m

Telescope Type:

Antennas or radio telescopes, same as the ones used in broadcasting. Like the infrared, there are some range of the wavelength are affected by the atmosphere, therefore, high and dry locations are needed for de studying this kind of light.

Associated Phenomenon:

Cold Universe, which means, mainly gas clouds and dust that could form new stars and planets. This kind of telescopes allows the observation of the early moments of the formation of stars, planets and galaxies.

Infrared

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MILKY WAY
Credits: WISE / NASA / JPL-Caltech / UCLA & IRAS / NASA
Frequency:

Between 4×10¹⁴  y 3×10¹¹ Hz

Wavelength:

Between 7×10ˉ⁷  y 1×10ˉ³ m

Telescope Type:

Generally these are similar to the optical telescopes, with the difference that these must be located in very high and dry landscapes, so they can catch wavelength that only could be detected in these areas. This is the reason why we need space and terrestrial telescopes to study the light that comes form the space.

Associated Phenomenon:

Every star release this kind of radiation, only that are the small stars, smaller that the Sun, the ones that emit more. This light its capable to get through clouds of dust, that for example exists in our galaxy, and therefore these light it is an incredible opportunity to observe the center of the Milky Way. The dust clouds, also emit and infrared radiation. This is a very wide range of frequency, that although, we can’t see we could fell it as warm or temperature.

Visible Light

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MILKY WAY
Credits: Nick Risinger & WHAM / VTSS / SHASSA / Finkbeiner
Frequency:

Between 7,5×10¹⁴  y 4×10¹⁴ Hz

Wavelength:

Between 4×10ˉ⁷  y 7×10ˉ⁷ m

Telescope Type:

These would be the classic optical lenses telescopes. This radiation gets through the atmosphere and is affected by the weather conditions. Most of the observatories located in Earth are for the observation of this kind of wavelength.

Associated Phenomenon:

Mostly stars in their stable period – as our Sun – also, these telescopes are use to observe nebulae. This light is catch by the normal human sight. But as is affected by weather conditions, there are better places than others to locate these optical telescopes.

Ultraviolet

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ANDROMEDA GALAXY
Credits: NASA/JPL-Caltech
Frequency:

Between 3×10¹⁶  y 7,5×10¹⁴ Hz

Wavelength:

Between 1×10ˉ⁸  y 4×10ˉ⁷ m

Telescope Type:

Space telescopes, due almost most of the light its absorbed by the atmosphere.

Associated Phenomenon:

Objects warmer than our Sun, mostly stars in their early or last periods of their evolution, as young massive stars or very old stars. This light it’s observed for the study of the chemical composition, density and interstellar medium’s temperature.

Gamma Ray And X Ray

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MILKY WAY
Credits: Fermi & ROSAT
Frequency:

Between 3×10¹⁹  y 3×10¹⁶ Hz

Wavelength:

Between 1×10ˉ¹¹  y 1×10ˉ⁸ m

Telescope Type:

This radiation it’s completely absorbed by the atmosphere, and so it is possible to make a direct observation from the space with telescopes that have optical instruments specially designed.

Associated Phenomenon:

These waves are related to objects at very high temperatures, cataclysmic events as supernova explosions and black hole’s nearby events; or any phenomenon that produced a big amount of energy. That’s the reason why these waves have the largest frequency of the spectrum.

  • Gamma Ray And X Ray

  • Ultraviolet

  • Visible Light

  • Infrared

  • Microwave & Radio

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λ= Wavelength / η= Frequency / T= Temperature

λ= Wavelength / η= Frequency / T= Temperature