Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Young Stars in Old Galaxies - a Cosmic Hide and Seek Game

26.06.2002


Surprise Discovery with World`s Leading Telescopes



Combining data from the NASA/ESA Hubble Space Telescope (HST) and the ESO Very Large Telescope (VLT), a group of European and American astronomers have made an unexpected, major discovery.

They have identified a huge number of "young" stellar clusters, only a few billion years old , inside an "old" elliptical galaxy (NGC 4365), probably aged some 12 billion years. For the first time, it has been possible to identify several distinct periods of star-formation in a galaxy as old as this one.


Elliptical galaxies like NGC 4365 have until now been considered to have undergone one early star-forming period and thereafter to be devoid of any star formation. However, the combination of the best and largest telescopes in space and on the ground has now clearly shown that there is more than meets the eye. This important new information will help to understand the early history of galaxies and the general theory of star formation in the Universe.

Do elliptical galaxies only contain old stars?

One of the challenges of modern astronomy is to understand how galaxies, those large systems of stars, gas and dust, form and evolve. In this connection, a central question has always been to learn when most of the stars in the Universe formed. Did this happen at a very early stage, within a few billion years after the Big Bang? Or were a significant number of the stars we now observe formed much more recently?

Spectacular collisions between galaxies take place all the time, triggering the formation of thousands or even millions of stars, cf. ESO PR Photo 29b/99 of the dramatic encounter between NGC 6872 and IC 4970. However, when looking at the Universe as a whole, most of its stars are found in large elliptical galaxies (this refers to their form) whose overall appearance has so far led us to believe that they, and their stars as well, are very old, indeed among the oldest objects in the Universe.

These elliptical galaxies do shine with the diffuse, reddish glow normally associated with stars that are many billions of years old. However, what is really the underlying mix of stars that produces this elderly appearance? Could perhaps a significant number of much younger stars be "hiding" among the older ones?

Whatever the case, this question must obviously be looked into, before it is possible to claim understanding of the evolution of these old galaxies. It is a very challenging investigation and it is only now that new and more detailed observations with the world`s premier telescopes have been obtained that cast more light on this central question and thus on the true behaviour of some of the major building blocks of the Universe.

Cosmic archaeology

In order to identify the constitutents of the stellar "cocktail" in elliptical galaxies, a team of European and American astronomers [2] observed massive stellar clusters in and around several nearby galaxies. These clusters, referred to as "globular" because of their shape, are present in large numbers around most galaxies and together they form a kind of "skeleton" within their host galaxies.

These "bones" receive an imprint for every episode of star formation they undergo. Thus, by reading the ages of the globular clusters in a galaxy, it is possible to identify the past epoch(s) of active star formation in that galaxy.

This is like digging into the ruins of an ancient archaeological city site and to find those layers and establish those times when the city underwent bursts of building activity. In this way, by the study of the distribution and ages of the globular clusters in an elliptical galaxy, astronomers can reveal when many of its stars were formed.

A surprise discovery

The team combined images in visual light of a number of galaxies from Hubble`s Wide Field and Planetary Camera 2 (WFPC2) with infrared images obtained with the multi-mode ISAAC instrument on the 8.2-m VLT ANTU telescope at the ESO Paranal Observatory (Chile). When measuring very accurately the colours of the globular clusters in one of these galaxies, NGC 4365 that is a member of the large Virgo Cluster of galaxies, they discovered to their great surprise that many of these clusters are only a few billion years old, i.e. much younger than the age of most other stars in that galaxy, roughly 12 billion years.

In fact, the astronomers were able to identify three major groups of globular clusters in NGC 4365. First, there is an old population of clusters of metal-poor stars, then there are some clusters of old, but metal-rich stars and now, seen for the first time, a third population of clusters with young and metal-rich stars.

"We needed the combination of the Hubble and the VLT with the latest space- and ground-based astronomical technology to break this new ground", says group leader Markus Kissler-Patig from the European Southern Observatory Headquarters in Garching (Germany). "Once we had found those young clusters, we then went on to observe them spectroscopically with another of the world`s giant telescopes, the 10-m Keck on Hawaii - and this fully confirmed our results."

A new important clue to the evolution of the Universe

This is a surprising discovery since the stars in giant elliptical galaxies were until now believed to have formed exclusively early on in the history of the Universe.

However, it is now clear that some of the old galaxies may have been hiding their true nature and have indeed experienced much more recent periods of major star formation.

This is priceless new information for the current attempts to understand the early history of galaxies and the general theory of star formation in the Universe.

More information

The information presented in this Press Release is based on a research article that has been accepted for publication in the European journal "Astronomy & Astrophysics" ("Extragalactic Globular Clusters in the Near-Infrared: II. The Globular Cluster Systems of NGC 3115 and NGC 4365" by Thomas H. Puzia, Stephen E. Zepf, Markus Kissler-Patig, Michael Hilker, Dante Minniti and Paul Goudfrooij; astro-ph/0206147).

Richard West | alfa
Further information:
http://www.eso.org/outreach/press-rel/pr-2002/pr-11-02.html

More articles from Physics and Astronomy:

nachricht Engineering team images tiny quasicrystals as they form
18.08.2017 | Cornell University

nachricht Astrophysicists explain the mysterious behavior of cosmic rays
18.08.2017 | Moscow Institute of Physics and Technology

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: Fizzy soda water could be key to clean manufacture of flat wonder material: Graphene

Whether you call it effervescent, fizzy, or sparkling, carbonated water is making a comeback as a beverage. Aside from quenching thirst, researchers at the University of Illinois at Urbana-Champaign have discovered a new use for these "bubbly" concoctions that will have major impact on the manufacturer of the world's thinnest, flattest, and one most useful materials -- graphene.

As graphene's popularity grows as an advanced "wonder" material, the speed and quality at which it can be manufactured will be paramount. With that in mind,...

Im Focus: Exotic quantum states made from light: Physicists create optical “wells” for a super-photon

Physicists at the University of Bonn have managed to create optical hollows and more complex patterns into which the light of a Bose-Einstein condensate flows. The creation of such highly low-loss structures for light is a prerequisite for complex light circuits, such as for quantum information processing for a new generation of computers. The researchers are now presenting their results in the journal Nature Photonics.

Light particles (photons) occur as tiny, indivisible portions. Many thousands of these light portions can be merged to form a single super-photon if they are...

Im Focus: Circular RNA linked to brain function

For the first time, scientists have shown that circular RNA is linked to brain function. When a RNA molecule called Cdr1as was deleted from the genome of mice, the animals had problems filtering out unnecessary information – like patients suffering from neuropsychiatric disorders.

While hundreds of circular RNAs (circRNAs) are abundant in mammalian brains, one big question has remained unanswered: What are they actually good for? In the...

Im Focus: RAVAN CubeSat measures Earth's outgoing energy

An experimental small satellite has successfully collected and delivered data on a key measurement for predicting changes in Earth's climate.

The Radiometer Assessment using Vertically Aligned Nanotubes (RAVAN) CubeSat was launched into low-Earth orbit on Nov. 11, 2016, in order to test new...

Im Focus: Scientists shine new light on the “other high temperature superconductor”

A study led by scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg presents evidence of the coexistence of superconductivity and “charge-density-waves” in compounds of the poorly-studied family of bismuthates. This observation opens up new perspectives for a deeper understanding of the phenomenon of high-temperature superconductivity, a topic which is at the core of condensed matter research since more than 30 years. The paper by Nicoletti et al has been published in the PNAS.

Since the beginning of the 20th century, superconductivity had been observed in some metals at temperatures only a few degrees above the absolute zero (minus...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Call for Papers – ICNFT 2018, 5th International Conference on New Forming Technology

16.08.2017 | Event News

Sustainability is the business model of tomorrow

04.08.2017 | Event News

Clash of Realities 2017: Registration now open. International Conference at TH Köln

26.07.2017 | Event News

 
Latest News

A Map of the Cell’s Power Station

18.08.2017 | Life Sciences

Engineering team images tiny quasicrystals as they form

18.08.2017 | Physics and Astronomy

Researchers printed graphene-like materials with inkjet

18.08.2017 | Materials Sciences

VideoLinks
B2B-VideoLinks
More VideoLinks >>>