Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Cosmic Portrait of a Perturbed Family

07.11.2005


ESO PR Photos 34/05 show in amazing details a group of galaxies known as Robert’s Quartet. Based on data collected with the FORS2 multi-mode instrument on ESO’s Very Large Telescope, they reveal galaxies in interaction with enhanced star formation.


Robert’s Quartet [1] is a family of four very different galaxies, located at a distance of about 160 million light-years, close to the centre of the southern constellation of the Phoenix. Its members are NGC 87, NGC 88, NGC 89 and NGC 92, discovered by John Herschel in the 1830s. NGC 87 (upper right) is an irregular galaxy similar to the satellites of our Milky Way, the Magellanic Clouds.

NGC 88 (centre) is a spiral galaxy with an external diffuse envelope, most probably composed of gas. NGC 89 (lower middle) is another spiral galaxy with two large spiral arms. The largest member of the system, NGC 92 (left), is a spiral Sa galaxy with an unusual appearance. One of its arms, about 100,000 light-years long, has been distorted by interactions and contains a large quantity of dust.

The quartet is one of the finest examples of compact groups of galaxies. Because such groups contain four to eight galaxies in a very small region, they are excellent laboratories for the study of galaxy interactions and their effects, in particular on the formation of stars.



Using another set of VLT data also obtained with FORS2, astronomers [2] were able to study the properties of regions of active star formation ("HII regions" [3]) in the sister members of Robert’s Quartet. They found more than 200 of such regions in NGC 92, with a size between 500 and 1,500 light-years (see ESO PR Photo 34b/05). For NGC 87, they detected 56 HII regions, while the two other galaxies appear to have far fewer of them.

For NGC 88, however, they found two plume-like features, while NGC 89 presents a ring of enhanced stellar activity. The system is thus clearly showing increased star formation activity, most probably as the result of the interaction between its members. The sisters clearly belong to a perturbed family.

The quartet has a total visual magnitude of almost 13, i.e. it is about 600 times fainter than the faintest object that can be seen with the unaided eye. The brightest member of the group has a magnitude of about 14. On the sky, the four galaxies are all within a circle of radius of 1.6 arcmin, corresponding to about 75,000 light-years.

[1]: The group of galaxies was known as a Compact Group since 1977 by J.A. Rose, under the designation Rose 34. Robert’s Quartet is also known under the less poetic name of AM 0018-485 from the Catalogue of Southern Peculiar Galaxies and Associations, compiled in 1987 by astronomers Halton "Chip" Arp and Barry Madore. But who is Robert then? As discovered by Australian amateur astronomer Mike Kerr, Arp and Madore named Robert’s Quartet after Robert Freedman who generated many of the updated positions of galaxies in the catalogue. The astronomers clearly had a very good sense of humour as the catalogue also contains a system of galaxies called Wendy (ESO 147- 8; for Wendy Freeman) and another called the Conjugal galaxy (ESO 384- 53)!

[2]: The astronomers are S. Temporin (University of Innsbruck, Austria), S. Ciroi and P. Rafanelli (University of Padova, Italy), A. Iovino (INAF-Brera Astronomical Observatory, Italy), E. Pompei (ESO), and M. Radovich (INAF-Capodimonte Astronomical Observatory, Italy). (The article describing this result is available in PDF format at http://www.ast.cam.ac.uk/%7Esb2004/posters/files/Temporin.pdf)

[3]: The radiation of young hot stars embedded in an interstellar cloud is able to heat the surrounding gas, resulting in the apparition of an emission nebula that shines mostly in the light of ionized hydrogen (H) atoms. Such nebulae are therefore often referred to as "HII regions". The well-known Orion Nebula is an outstanding example of that type of nebula.

Henri Boffin | alfa
Further information:
http://www.eso.org/outreach/press-rel/pr-2005/phot-34-05.html

More articles from Physics and Astronomy:

nachricht A 100-year-old physics problem has been solved at EPFL
23.06.2017 | Ecole Polytechnique Fédérale de Lausanne

nachricht Quantum thermometer or optical refrigerator?
23.06.2017 | National Institute of Standards and Technology (NIST)

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: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>