Cosmic dust annoyed astronomers because they prevented them from observing their distant stars. But cosmic dust also poses one of the great mysteries in astronomy.
Donal York, professor of astronomy and astrophysics at the University of Chicago, said: 'We not only don't know what it is, but we don't know where it was made and how it came out. visible in the universe '.
But now York and Adolf Witt of the University of Toledo and colleagues have observed a binary star system that has all the features astronomers suspect is related to the emergence of cosmic dust. . The Journal of Astrophysics will publish an article about the team's discovery in March.
The binary star system, named HD 44179, is in something they call the Red Rectangle Red rectangle, in fact a cluster of gas and dust (nebulae) in the midst of stars about 2,300 light-years from Earth. .
According to the researchers, one of the two stars is in a form that is considered to be a source of dust. These two stars, unlike the sun, burned off the hydrogen in their cores. Given the names of post-AGB stars, these objects break down after burning off the initial hydrogen until they can generate enough heat to ignite the new fuel, which is helium.
Dust in the solar wind
During transitions that take place over tens of thousands of years, these stars lose their outer atmosphere. Dust can form in the cooling layer, in which the radiation pressure emitted from the inner part of the star blows away the dust with a large amount of gas.
In each of these systems, the double disk of the post-AGB star can form around a smaller, smaller, and smaller star. York explained: 'When the disk is formed, they often create rays that blow a portion of the material away from the original system, bringing matter into the universe'. This seems to be the phenomenon that Witt's group has observed in the Red Rectangle, perhaps the most typical example discovered so far. This finding is of great significance because cosmic dust plays a key role in scientific hypotheses about star formation.
York said: 'If a cloud of dust gas dissipates due to its gravitational pull, it will immediately become hotter and start to evaporate.' Something, perhaps dust, must cool the cloud right away to prevent it from heating again.
The giant star in the Red Rectangle is a group of stars that are too hot to allow dust to build up in their atmosphere. Surrounding them is the giant dust belt. Witt's team observed pairs of stars for about 15 hours during 7 years using a 3.5 m diameter telescope located at Apache Point Observatory, New Mexico. Witt, an honorary professor of astronomy, said: 'Our observations have demonstrated that the gravitational interaction between the giant Red Rectangle and a nearby companion star like the sun has made material escapes the outer part of the giant star '. Part of the material stopped at the disk of dust surrounding the smaller star. Gradually, over nearly 500 years, matter moved into a smaller star in a spiral.
Bipolar operation
Just before this event occurred, the smaller star ejected a small amount of matter accumulated by two gas rays in two different directions called 'bipolar rays'.
The amount of matter left from the outer part of the big star stops at the disk around both stars where it will cool. 'Heavy components like iron, nickel, silicon, calcium and carbon condensed into solid particles once they leave the system, we observe these particles in the form of dust among stars.'
Cosmic dust formation does not appear under a telescope because they last only about 10,000 years - a short period of time compared to the life of a star. Astronomers have observed other objects similar to the Red Rectangle in the Milky Way's neighbor galaxy. This shows the process that Witt's team observed is quite common when viewed based on the life cycle of the galaxy.
Witt said: 'Processes similar to the process we are observing in the Red Rectangle nebula may have occurred hundreds of millions of times since the formation of the Milky Way galaxy.
Witt and York first met at the University of Yerkes Observatory (Chicago) where Lew Hobbs, now an honorary professor of astronomy and astrophysics, joined. Other co-authors include Julie Thorburn of Yerkes Observatory, Uma Vijh of Toledo University, and Jason Aufdenberg, Embry-Riddle Aviation University in Florida.
The group was set up to achieve a modest goal: to find Red Rectagle's source of ultraviolet radiation. Red Rectagle has several phenomena that require far ultraviolet radiation as an energy source. 'The problem is that very bright central stars in the Red Rectangle are not hot enough to produce the necessary UV radiation' . That's why Witt and his colleagues started the search process.
The results showed that both stars in this binary system were not UV radiation sources, but the hot area inside the gas disk surrounding the smaller star (with a temperature of about 20,000 degrees). Witt said: 'Our observations have brought more useful things than we could dream of.'