Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Theft of a million stars

15.02.2006


Using ESO’s Very Large Telescope, a team of Italian astronomers reveal the troubled past of the stellar cluster Messier 12 – our Milky Way galaxy ‘stole’ close to one million low-mass stars from it.



Globular clusters move in extended elliptical orbits that periodically take them through the densely populated regions of our galaxy, and then high above and below the plane (the ’halo’). When venturing too close to the innermost dense regions of our galaxy, (the ’bulge’), a globular cluster can be perturbed and its smallest stars ripped away.

The astronomers, led by Guido De Marchi of the European Space Agency, measured the brightness and colours of more than 16 000 stars within the Messier 12 cluster with one of the Unit Telescopes of ESO’s VLT at Cerro Paranal in Chile. The team could study stars that are 50 million times fainter than those seen with the unaided eye.


"In the solar neighbourhood and in most stellar clusters, the least massive stars are by far the most common. But our observations with the VLT show this is not the case for Messier 12," said De Marchi.

"It is however clear that Messier 12 is surprisingly devoid of low-mass stars. For each solar-like star, we would expect roughly four times as many stars with half that mass. Our VLT observations only show an equal number of stars of different masses."

The team estimated that Messier 12 lost four times as many stars as it still has. That is, roughly one million stars must have been ejected into the halo of the Milky Way, probably because it ventures too close to the galactic centre during its orbit.

"Our result is at odds with previous estimates of the cluster orbit, made over a decade ago, but is perfectly in line with a new analysis based on the Hipparcos reference data. In other words, Hipparcos data and our result go hand-in-hand to show that previous models of the cluster orbit were inaccurate," said De Marchi.

The total remaining lifetime of Messier 12 is predicted to be about 4500 million years, or about a third of its present age. This is very short compared to the typical expected globular cluster’s lifetime, which is about 20 000 million years.

In 1999, the same team found another example of a globular cluster that lost a large fraction of its original content. They hope to discover and study many more clusters like these, since catching clusters while being disrupted should clarify the dynamics of the process that shaped the halo of our home galaxy, the Milky Way.

“This can tell us how globular clusters interact with the Milky Way and how they have ‘replenished’ the galactic halo with old stars over millions of years. But if we want to know exactly how these clusters orbit the Galaxy and what the galactic halo really looks like, we must wait for ESA’s 3D mapping mission Gaia,” said De Marchi.

Guido De Marchi | alfa
Further information:
http://www.esa.int/esaSC/SEM07XLVGJE_index_0.html

More articles from Physics and Astronomy:

nachricht Squeezing light at the nanoscale
17.06.2018 | Harvard John A. Paulson School of Engineering and Applied Sciences

nachricht The Fraunhofer IAF is a »Landmark in the Land of Ideas«
15.06.2018 | Fraunhofer-Institut für Angewandte Festkörperphysik IAF

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: AchemAsia 2019 will take place in Shanghai

Moving into its fourth decade, AchemAsia is setting out for new horizons: The International Expo and Innovation Forum for Sustainable Chemical Production will take place from 21-23 May 2019 in Shanghai, China. With an updated event profile, the eleventh edition focusses on topics that are especially relevant for the Chinese process industry, putting a strong emphasis on sustainability and innovation.

Founded in 1989 as a spin-off of ACHEMA to cater to the needs of China’s then developing industry, AchemAsia has since grown into a platform where the latest...

Im Focus: First real-time test of Li-Fi utilization for the industrial Internet of Things

The BMBF-funded OWICELLS project was successfully completed with a final presentation at the BMW plant in Munich. The presentation demonstrated a Li-Fi communication with a mobile robot, while the robot carried out usual production processes (welding, moving and testing parts) in a 5x5m² production cell. The robust, optical wireless transmission is based on spatial diversity; in other words, data is sent and received simultaneously by several LEDs and several photodiodes. The system can transmit data at more than 100 Mbit/s and five milliseconds latency.

Modern production technologies in the automobile industry must become more flexible in order to fulfil individual customer requirements.

Im Focus: Sharp images with flexible fibers

An international team of scientists has discovered a new way to transfer image information through multimodal fibers with almost no distortion - even if the fiber is bent. The results of the study, to which scientist from the Leibniz-Institute of Photonic Technology Jena (Leibniz IPHT) contributed, were published on 6thJune in the highly-cited journal Physical Review Letters.

Endoscopes allow doctors to see into a patient’s body like through a keyhole. Typically, the images are transmitted via a bundle of several hundreds of optical...

Im Focus: Photoexcited graphene puzzle solved

A boost for graphene-based light detectors

Light detection and control lies at the heart of many modern device applications, such as smartphone cameras. Using graphene as a light-sensitive material for...

Im Focus: Water is not the same as water

Water molecules exist in two different forms with almost identical physical properties. For the first time, researchers have succeeded in separating the two forms to show that they can exhibit different chemical reactivities. These results were reported by researchers from the University of Basel and their colleagues in Hamburg in the scientific journal Nature Communications.

From a chemical perspective, water is a molecule in which a single oxygen atom is linked to two hydrogen atoms. It is less well known that water exists in two...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Munich conference on asteroid detection, tracking and defense

13.06.2018 | Event News

2nd International Baltic Earth Conference in Denmark: “The Baltic Sea region in Transition”

08.06.2018 | Event News

ISEKI_Food 2018: Conference with Holistic View of Food Production

05.06.2018 | Event News

 
Latest News

A sprinkle of platinum nanoparticles onto graphene makes brain probes more sensitive

15.06.2018 | Materials Sciences

100 % Organic Farming in Bhutan – a Realistic Target?

15.06.2018 | Ecology, The Environment and Conservation

Perovskite-silicon solar cell research collaboration hits 25.2% efficiency

15.06.2018 | Power and Electrical Engineering

VideoLinks
Science & Research
Overview of more VideoLinks >>>