Did the First Stars Shine Light ?

Recent studies show they might have not. Powered with energy, resulted from the interaction between ordinary matter and dark matter, and having masses between 400 to 200,000 times that of the Sun, these so-called "dark stars" could have been the first structures to ever populate the universe.

It is now widely believed that dark energy and dark matter represent more than three quarters of our universe, and the formation of stars might have been greatly influenced by their presence through annihilation interactions. Though it has not yet been discovered or directly observed, dark energy is quickly being included in most of the theories related to the birth of the universe and its current configuration.

A study carried at the University of Utah predicts the existence of giant dark stars that might exist even today, which though cataloged as stars do not emit light in the usual way, thus they are much harder to spot, and might be observed by studying the gamma ray emissions, neutrino and antimatter, that can be associated to a large cold cloud formed of molecular hydrogen which would normally emit extremely energetic particles.

However, according to astrophysicist Paolo Gondolo, these predictions remain mostly theoretical since there are no simulations that could reveal the evolution of these structures. Nevertheless, the existing simulations point that they could have a lifespan from a few months to more than 600 million years, or even billions of years existing since the birth of the universe.

Such "brown giants" could be similar to the so-called "brown dwarf", small stars roughly the size of the planet Jupiter. This would be the first time when the role of dark matter would be accounted for in the process of star formation. Dark matter has been predicted in 1998, from the observations of the visible universe which revealed that not only was the universe expanding, but the speed at which this process was taking place was growing exponentially, somehow affecting the effect of the gravitational fields exerted by the galaxies. From this effect astrophysicists approximated that ordinary matter represents only about 4 percent of the total energy in the universe.

It is now generally believed that dark matter is composed mostly of massive elementary particles that present weak interactions with the normal matter, thus the discovery of such "neutralinos" might solve the mystery related to the origin of mass in the universe.

About 13 billion years ago an anomaly from which an enormous amount of pure energy originated suddenly occurred. Part of that pure energy was converted into normal matter, anti-matter and possibly dark-matter, that eventually suffered an expansion. The remnant energy of the 'explosion' can be observed today, in the Cosmic Microwave Background radiation, which presents certain temperature fluctuations that match exactly the pattern of galaxies seen in the universe. Though most of the matter created was dark matter, it also incorporated small amounts of normal matter in the form of hydrogen and helium gas.

Observations and examples of how stars form suggest that these clouds of molecular hydrogen and helium collapse on theirselves under the influence of gravity, inside proto-stellar clouds that start to cool and shrink to become more compact, until the nuclear fusion reaction to turn hydrogen into helium kicks in.

The new model related to stellar formation predicts that the dark matter particles inside these clouds annihilate each other, resulting in the creation of the quark particles and their anti-particles. The interaction is supposed to be izotermic, thus the extra heat generated keeps the cloud from cooling down, preventing the initiation of the fusion reaction inside the star, stopping the forming of a star for certain periods of time, thus spawning a dark star.

These structures could be as large as 2,000 astronomical units, as a result of the fact that the cloud of gas cannot collapse. Quark annihilation produces gamma rays emissions, neutrinos and other antimatter particles, that can be used to identify dark stars.

Also, this theory might be able to explain how some of the heaviest of the chemical elements formed in the nuclear fusion reaction. However, evidence found so far points that dark stars cannot evolve into regular stars, so they were not able to produce heavy elements such as carbon. Black holes could also have their origins in these structures that might be able to form stars so compact that light from their surface could never escape so they collapse into black holes due to their short lives.

On the other hand, scientists take into consideration the fact that dark stars could actually be quite long lived and turn into conventional stars.