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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
03

How stars are born

TEXT Paul Elliot

ILLUSTRATION Telly Gacitúa & Toro

  • PDF
Cat paw Nebula
Illustration: V. Vergara.

When we look up into the night sky we can see many stars and if you’re lucky you may even be able to see a few galaxies (The Large and Small Magellanic Clouds, and of course, our very own Milky Way stretched across the sky). But how do such things come to be? Who made the stars and scattered them across the sky for us to gaze at? It all starts with the collapse of clouds.

If all around the universe every piece of matter was evenly spaced and stationary what would happen? Well… not a lot, and that’s just no fun. But let’s say we have a cloud of “stuff” out in space and we perturb it a bit, give it a little poke in the right direction, what will we see? Well if you’re lucky it just might start to contract and that’s where things get interesting…

Here I must introduce two very important types of energy to further explain this process; kinetic energy and gravitational potential energy. The kinetic energy is basically the movement of the particles in the cloud it increases when the speed of the particles increase. The gravitational potential energy is due to the force of gravity (the clue’s in the name right). If you take two bodies of mass, let’s say the Earth and the Moon, there is a gravitational force between them that keeps them orbiting each other. Or looking at it a different way; there is a certain amount of energy required to un-bind the system and overcome gravity; this is the gravitational potential energy and it depends on distance between the two objects.

Aside: In order for you to appreciate the scale of this process think about this. The cloud of stuff (gas and dust), is huge; it would take you years and years to travel from one end to the other if you were a photon with a speed of 300 000 meters per second! Whereas once the star has formed it would only take you a second or two. Also if you’re thinking about watching a cloud collapse into a star you may want to start now, as it’s going to take a million years to happen.

Before is born a star is submerged under a disk of dust and gas. After 4600 millions years becomes a star as our Sun. After spending most of its life in this stage, the star starts to heat up gradually, expanding and intensifying its tone until it becomes a red giant.

So back to the process, the cloud is collapsing, more and more matter is being packed into a smaller space; it’s getting more dense. This also means that the average distance between the particles is getting smaller i.e. the gravitational potential energy is decreasing, so where is that energy going? Well, that energy is being converted into kinetic energy; into the movement of the particles, isn’t physics beautiful!

The cloud gets smaller and smaller, the particles move faster and faster and that means it gets hotter and hotter. Every object with a temperature above -273°C (the coldest temperature possible, pretty chilly I know) emits radiation, energy. What type of radiation depends on its temperature, every one of us is emitting it right now you just can’t see it. So the cloud is radiating away energy as it collapses but eventually in the hottest part of this cloud, its core, this radiation can’t escape so easily, it starts to build up and the temperature goes through the roof, around 1 000 000°C (not so chilly!). Once these temperatures are achieved nuclear fusion starts, in the core of the star and hey presto, our star is born! This process of fusion powers a star, like our Sun, for many hundreds of billions of years, long enough for us to evolve, which is pretty handy really.

So now that the two types of energy (kinetic and gravitational potential) are now roughly equal, the star neither contracts or expands, it is in what we call equilibrium. We can sit back and bathe in the radiation from the Sun, just make sure you put on your suncream.