The unusual cluster Terzan 5
The unusual cluster Terzan 5
The location of the star cluster Terzan 5
Around the star cluster Terzan 5
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Using ESO’s Very Large Telescope and other telescopes a fossilised remnant of the early Milky Way harbouring stars of hugely different ages has been revealed by an international team of astronomers. This stellar system resembles a globular cluster, but is like no other cluster known. It contains stars remarkably similar to the most ancient stars in the Milky Way and bridges the gap in understanding between our galaxy’s past and its present.
Terzan 5, 19 000 light-years from Earth in the constellation of Sagittarius (the Archer) and in the direction of the galactic centre, has been classified as a globular cluster
for the forty-odd years since its detection. Now, an Italian-led team
of astronomers have discovered that Terzan 5 is like no other globular
cluster known.
The team scoured data from the Multi-conjugate Adaptive Optics Demonstrator [1], installed at the Very Large Telescope, as well as from a suite of other ground-based and space telescopes [2].
They found compelling evidence that there are two distinct kinds of
stars in Terzan 5 which not only differ in the elements they contain,
but have an age-gap of roughly 7 billion years [3].
The ages of the two populations indicate that the star
formation process in Terzan 5 was not continuous, but was dominated by
two distinct bursts of star formation. “This requires the Terzan 5
ancestor to have large amounts of gas for a second generation of stars
and to be quite massive. At least 100 million times the mass of the
Sun,” explains Davide Massari, co-author of the study, from INAF, Italy, and the University of Groningen, Netherlands.
Its unusual properties make Terzan 5 the ideal candidate
for a living fossil from the early days of the Milky Way. Current
theories on galaxy formation assume that vast clumps of gas and stars
interacted to form the primordial bulge of the Milky Way, merging and
dissolving in the process.
“We think that some remnants of these gaseous clumps
could remain relatively undisrupted and keep existing embedded within
the galaxy,” explains Francesco Ferraro from the University of
Bologna, Italy, and lead author of the study. “Such galactic fossils
allow astronomers to reconstruct an important piece of the history of
our Milky Way.”
While the properties of Terzan 5 are uncommon for a
globular cluster, they are very similar to the stellar population which
can be found in the galactic bulge,
the tightly packed central region of the Milky Way. These similarities
could make Terzan 5 a fossilised relic of galaxy formation, representing
one of the earliest building blocks of the Milky Way.
This assumption is strengthened by the original mass of
Terzan 5 necessary to create two stellar populations: a mass similar to
the huge clumps which are assumed to have formed the bulge during galaxy
assembly around 12 billion years ago. Somehow Terzan 5 has managed to
survive being disrupted for billions of years, and has been preserved as
a remnant of the distant past of the Milky Way.
“Some characteristics of Terzan 5 resemble those
detected in the giant clumps we see in star-forming galaxies at
high-redshift, suggesting that similar assembling processes occurred in
the local and in the distant Universe at the epoch of galaxy formation,“ continues Ferraro.
Hence, this discovery paves the way for a better and more complete understanding of galaxy assembly. “Terzan
5 could represent an intriguing link between the local and the distant
Universe, a surviving witness of the Galactic bulge assembly process,”
explains Ferraro while commenting on the importance of the discovery.
The research presents a possible route for astronomers to unravel the
mysteries of galaxy formation, and offers an unrivaled view into the
complicated history of the Milky Way.
Notes
[1] The Multi-Conjugate Adaptive Optics Demonstrator (MAD) is a prototype multi-conjugate adaptive optics system which aims to demonstrate the feasibility of different MCAO reconstruction techniques in the framework of the E-ELT concept and the second generation VLT Instruments.
[3] The two detected stellar populations have ages of 12 billion years and 4.5 billion years respectively.
More Information
This research was presented in a paper entitled “The age of the young bulge-like population in the stellar system Terzan 5: linking the Galactic bulge to the high-z Universe”, by F. R. Ferraro et al., which will be published in the Astrophysical Journal.
The team is composed of F. R. Ferraro (Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Italy) , D. Massari (INAF - Osservatorio Astronomico di Bologna, Italy & Kapteyn Astronomical Institute, University of Groningen, Netherlands), E. Dalessandro (Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Italy; INAF - Osservatorio Astronomico di Bologna, Italy) , B. Lanzoni (Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Italy), L. Origlia (INAF - Osservatorio Astronomico di Bologna, Italy), R. M. Rich (Department of Physics and Astronomy, University of California, Los Angeles, USA) and A. Mucciarelli (Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Italy).
ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
Links
Contacts:
Francesco Ferraro
Università degli Studi di Bologna
Bologna, Italy
Tel: +39 051 20 9 5774
Email: francesco.ferraro3@unibo.it
Davide Massari
INAF - Osservatorio Astronomico di Bologna
Bologna, Italy
Tel: +51 2095318
Email: davide.massari@oabo.inaf.it
Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Notes
[1] The Multi-Conjugate Adaptive Optics Demonstrator (MAD) is a prototype multi-conjugate adaptive optics system which aims to demonstrate the feasibility of different MCAO reconstruction techniques in the framework of the E-ELT concept and the second generation VLT Instruments.
[2] The researchers also used data from the Wide Field Camera 3 on board the NASA/ESA Hubble Space Telescope and NIRC2 (the Near-Infrared Camera, second generation) at the W. M. Keck Observatory.
More Information
This research was presented in a paper entitled “The age of the young bulge-like population in the stellar system Terzan 5: linking the Galactic bulge to the high-z Universe”, by F. R. Ferraro et al., which will be published in the Astrophysical Journal.
The team is composed of F. R. Ferraro (Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Italy) , D. Massari (INAF - Osservatorio Astronomico di Bologna, Italy & Kapteyn Astronomical Institute, University of Groningen, Netherlands), E. Dalessandro (Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Italy; INAF - Osservatorio Astronomico di Bologna, Italy) , B. Lanzoni (Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Italy), L. Origlia (INAF - Osservatorio Astronomico di Bologna, Italy), R. M. Rich (Department of Physics and Astronomy, University of California, Los Angeles, USA) and A. Mucciarelli (Dipartimento di Fisica e Astronomia, Università degli Studi di Bologna, Italy).
ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.
Links
Contacts:
Francesco Ferraro
Università degli Studi di Bologna
Bologna, Italy
Tel: +39 051 20 9 5774
Email: francesco.ferraro3@unibo.it
Davide Massari
INAF - Osservatorio Astronomico di Bologna
Bologna, Italy
Tel: +51 2095318
Email: davide.massari@oabo.inaf.it
Richard Hook
ESO Public Information Officer
Garching bei München, Germany
Tel: +49 89 3200 6655
Cell: +49 151 1537 3591
Email: rhook@eso.org
Source: ESO
