Even though we are millions upon millions of miles away from the nearest star, scientists developed fairly accurate theories for the evolution of stars. Mostly all stars are found in large groups— on the order of over hundreds of billions to trillions of stars – called galaxies.

Our planet, Earth, orbits one of about one hundred billion stars in the Milky Way galaxy. A galaxy, like our Milky Way, can span a distance of up to 100,000 light years, where one light year is the equivalent of some 5.8 trillion miles. Due to the geometry and size of these galaxies, star formation is possible. Without these special characteristics, stars would not be able to form at the rate they do. However the discovery of star formation at steady rates in dwarf galaxies shook the foundations of current star formation theory – because according to theory, they should not be able to form stars.

This apparent hole in current stellar evolution theory has been tackled by many astronomers around the world. Among them is Dr. Caroline Simpson. Dr. Simpson is an Associate Professor in the FIU physics department and an FIU Honors College Fellow. She has been working extensively alongside Dr. Diedre Hunter, an astronomer at the Lowell Observatory in Arizona and Dr. Bruce Elmegreen, a theorist at the Watson IBM Research Center since 1998, to determine what makes these galaxies tick.

Dwarf galaxies are exactly that – really small galaxies. In comparison to the Milky Way, most dwarf galaxies are 85% smaller (around 6700 light years across), containing around a 30 billion stars. Star formation in spiral-shaped galaxies like the Milky Way occurs primarily two ways. First, since there is massive amount of material available in the galaxy, stars form due to the accumulation of interstellar hydrogen gas and molecular clouds, localizing due to mutual gravitation. Eventually, over the span of millions of years, enough interstellar matter amalgamates for the gravitational force to create intense pressures at the core of the newly formed star, thus allowing for nuclear fusion to occur – the central “generator” of the star. Second, spiral density waves aid in the process of speeding up this formation process in spiral galaxies. Density waves are regions of dense matter which move through the galaxy, eventually colliding with regions of stationary matter, thereby collapsing the cloud faster than it would have on its own.

Dwarf galaxies have neither of the above two properties in order to support star formation. “The spiral galaxies have this compression mechanism, so it’s easier for them to make stars,” said Dr. Simpson. “However, for a galaxy to physically support spiral density waves propagating through it, it has to have a certain minimum mass. Dwarfs don’t have that mass requirement – they’re too small; kind of like a blob of a galaxy actually.”

Over the past 15 years, Dr. Hunter has amassed data on over 130 various dwarf galaxies. Most of the data from the survey of these galaxies was done over a range of wavelengths from the radio end of the spectrum to X-rays and ultraviolet. Looking at the galaxies in various wavelengths of light reveals different information. An ultraviolet image detects hot, young stars. Looking at the galaxy in infra-red reveals regions where older stars and dust clouds are located.

The radio end of the spectrum, which Dr. Simpson specializes in, uncovers regions of hydrogen gas in the galaxies – the raw material of the stars. With the radio end of the spectrum available to her, Dr. Simpson looks at the interplay between the star formation and the material from which they form. Various interactions lead to different scenarios of formation behavior, but frankly speaking, it is anything but a simple process. Looking at various dwarf galaxies, in our “local” neighborhood of the universe, there are dwarf galaxies forming stars, others exhibiting odd behavior in star formation and some which do not form stars at all. The question remains as to the inner workings of each dwarf galaxy and trying to form a collective model to explain it all. “The devil is in the detail – looking at the smaller scale process we see that because [the dwarf galaxies] are so small, they’re susceptible to small changes,” explained Dr. Simpson.

Dr. Simpson and her colleagues have already sent another proposal to work at the Very Large Array (VLA) Radio Telescope located in New Mexico, on the plains of San Augustine. The proposal includes observing time of at least 300 hours (typical proposals ask for around 30 – 50 hours). This study intends to further understand the inner workings of these mysterious “blobs” of galaxies, which will be conducted over a 2-3 year span. Dr. Simpson will analyze individual aspects of these dwarf galaxies while Dr. Hunter along with Dr. Elmegreen will work on a more general star formation model for these galaxies.

Dwarf galaxies are very interesting subjects. They are now thought to have been building blocks of the earlier universe, where many dwarf galaxies merged together, forming the now known regular-sized galaxies. Those which weren’t lucky enough to merge remained in their miniscule forms. In actuality, most of the universe is made of dwarf galaxies. Out of the 35 or so galaxies in our local cluster of galaxies (a diameter spanning 10 million light years), only 3 are actually regular spiral galaxies: Andromeda, the Milky Way and the Triangulum galaxy. The other 30 or so are dwarf galaxies.

When asked what effect these studies might have on everyday life, Dr. Simpson’s reply was short and effective. “What use is a newborn baby?” In other words, the potential wrought by a new discovery or theory is unknown. Only time will tell.