Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

The universe just became a little simpler

18.06.2003


Using images from the Hubble Space Telescope, astronomers have concluded that two of the most common types of galaxies in the universe are in reality different versions of the same thing. In spite of their similar-sounding names, astronomers had long considered “dwarf elliptical” and “giant elliptical” galaxies to be distinct objects. The new findings, which appear in this month’s edition of The Astronomical Journal, fundamentally alter astronomers’ understanding of these important components of the universe.


Artist’s impression of two black holes evacuating the center of a galaxy. Credit: Gabriel Perez Diaz; MultiMedia Service; Instituto de Astrofísica de Canarias (IAC).



Galaxies, the building blocks of the visible universe, are enormous systems of stars bound together by gravity and scattered throughout space. There are several different types, or shapes. For example, the Milky Way galaxy, in which the Earth resides, is a “spiral” galaxy, so named because its disk-like shape has an embedded spiral arm pattern. Other galaxies are known as “irregular” galaxies because they do not have distinct shapes. But together, dwarf and giant elliptical galaxies are the most common.

For the past two decades, astronomers have considered giant elliptical galaxies, which contain hundreds of billions of stars, and dwarf elliptical galaxies, which typically contain less than one billion stars, as completely separate systems. In many ways it was a natural distinction: not only do giant elliptical galaxies contain more stars, but the stars are more closely packed toward the centers of such galaxies. In other words, the overall distribution of stars appeared to be fundamentally different.


Alister Graham and Rafael Guzmán from the University of Florida decided to take a second look at the accepted wisdom. Expanding on work started by Graham at the Instituto de Astrofísica de Canarias (IAC) in Spain, the pair analyzed images of dwarf elliptical galaxies taken by the Hubble Space Telescope and combined their results with previously collected data on over 200 galaxies. The resulting sample revealed distributions of stars displaying a continuous variety of structures between the allegedly different dwarf and giant galaxy classes - in other words, these two types were just relatively extreme versions of the same object. Moreover, there was one rather interesting caveat.

In recent years, Graham said, a number of studies had revealed that the innermost centers of giant elliptical galaxies - the inner 1 percent - had been scoured out or emptied of stars. Astronomers suspect that massive black holes are responsible, gravitationally hurling away any stars that ventured too near and devouring the stars that came in really close. This scouring phenomenon had tended to dim the centers of giant elliptical galaxies, which ran counter to the trend that bigger galaxies tend to have brighter centers. The dimming phenomenon was one reason astronomers had concluded dwarf and giant galaxies must be different types.

Together with Ignacio Trujillo of the Max-Planck Institut für Astronomie in Germany and Peter Erwin and Andres Asensio Ramos of the IAC, Graham addresses this phenomenon in a separate article that appears in the same issue of The Astronomical Journal. Building on recent revelations showing a strong connection between the mass of the central black holes and the properties of their host galaxies, Graham and his colleagues introduced a new mathematical model that simultaneously describes the distribution of stars in the inner and outer parts of the galaxy. “It was only after allowing for the modification of the cores by the black holes that we were able to fully unify the dwarf and giant galaxy population,” Graham said.

“This helps to simplify the universe slightly because we can replace two distinct galaxy types with one,” said Graham. “But the implications go beyond mere astronomical taxonomy. Astronomers had thought the formation mechanisms for these objects must be different, but instead there must be a unifying construction process.”

Sidney van den Bergh, former director and researcher emeritus at the Dominion Astrophysical Observatory at the National Research Council of Canada in Victoria, said Graham and Guzmán’s result puts to rest a “very puzzling” question.

“In astronomy, like in physical anthropology, there is a deep connection between the classification of species and their evolutionary connections,” van den Bergh said. “The bottom line is that the new work of Graham and Guzmán has made life a little bit simpler for those of us who want to understand how galaxies are formed and have evolved.”

Alister Graham | alfa
Further information:
http://www.iac.es/gabinete/noticias/2003/m06d16.htm

More articles from Physics and Astronomy:

nachricht Pulses of electrons manipulate nanomagnets and store information
21.07.2017 | American Institute of Physics

nachricht Vortex photons from electrons in circular motion
21.07.2017 | National Institutes of Natural Sciences

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Manipulating Electron Spins Without Loss of Information

Physicists have developed a new technique that uses electrical voltages to control the electron spin on a chip. The newly-developed method provides protection from spin decay, meaning that the contained information can be maintained and transmitted over comparatively large distances, as has been demonstrated by a team from the University of Basel’s Department of Physics and the Swiss Nanoscience Institute. The results have been published in Physical Review X.

For several years, researchers have been trying to use the spin of an electron to store and transmit information. The spin of each electron is always coupled...

Im Focus: The proton precisely weighted

What is the mass of a proton? Scientists from Germany and Japan successfully did an important step towards the most exact knowledge of this fundamental constant. By means of precision measurements on a single proton, they could improve the precision by a factor of three and also correct the existing value.

To determine the mass of a single proton still more accurate – a group of physicists led by Klaus Blaum and Sven Sturm of the Max Planck Institute for Nuclear...

Im Focus: On the way to a biological alternative

A bacterial enzyme enables reactions that open up alternatives to key industrial chemical processes

The research team of Prof. Dr. Oliver Einsle at the University of Freiburg's Institute of Biochemistry has long been exploring the functioning of nitrogenase....

Im Focus: The 1 trillion tonne iceberg

Larsen C Ice Shelf rift finally breaks through

A one trillion tonne iceberg - one of the biggest ever recorded -- has calved away from the Larsen C Ice Shelf in Antarctica, after a rift in the ice,...

Im Focus: Laser-cooled ions contribute to better understanding of friction

Physics supports biology: Researchers from PTB have developed a model system to investigate friction phenomena with atomic precision

Friction: what you want from car brakes, otherwise rather a nuisance. In any case, it is useful to know as precisely as possible how friction phenomena arise –...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Closing the Sustainability Circle: Protection of Food with Biobased Materials

21.07.2017 | Event News

»We are bringing Additive Manufacturing to SMEs«

19.07.2017 | Event News

The technology with a feel for feelings

12.07.2017 | Event News

 
Latest News

NASA looks to solar eclipse to help understand Earth's energy system

21.07.2017 | Earth Sciences

Stanford researchers develop a new type of soft, growing robot

21.07.2017 | Power and Electrical Engineering

Vortex photons from electrons in circular motion

21.07.2017 | Physics and Astronomy

VideoLinks
B2B-VideoLinks
More VideoLinks >>>