Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Stars are promiscuous

30.04.2002


Blue stragglers (ringed) are irresistable to others.
© NASA/Hubble


Succession of relationships keeps heavenly bodies young

Astronomers have uncovered a scandalous degree of promiscuity in the cosmos. Clusters where stars gather more densely than usual are veritable hotbeds of partner-swapping. Some stars engage in half a dozen or so relationships during their lifetime1.

Star clusters range from loose groups of ten thousand or so stars to dense globular clusters of a million or more. They exist throughout galaxies like ours - from near the Galactic Centre to far outside the main galaxy body. In the centre of a globular cluster, star density can be more than 10 million times that around our own Sun.



Jarrod Hurley and Michael Shara, astronomers at the American Museum of Natural History in New York, have carried out state-of-the-art computer simulations of star clusters on new, purpose-built hardware called GRAPE-6.

GRAPE stands for ’gravity pipe’, a system devised in the mid-1990s to calculate the behaviour of thousands of stars moving under the influence of one another’s gravitational fields. In principle, every star influences every other one, so these calculations are very demanding.

Previous generations of GRAPE made many simple and unrealistic assumptions about the interactions between stars in clusters. GRAPE-6 follows the lives of individual stars in a population of 50,000 or so in great detail.

Clusters are so dense that two stars often become bound into binary systems. These pirouette around their common centre of mass. Some stars can even get trapped in groups of three or more. Hurley and Shara were surprised to find that these partnerships can form and break many times in a star’s life; so a star could have several different partners in close succession.

This promiscuity takes its toll. When they get together, stars can undergo profound character changes. In particular, they can coalesce or pull material from their partner to form larger, more massive stars.

Ménages and mergers

The researchers followed one particular star that began life as an object much like the Sun, but bound in a binary system with another star of about half its mass. First, this pair had a short-lived ménage-à-trois with a smaller star. They then got together with a triple system in a group of five.

After some dramatic exits from the group, the initial star, now aged about 3.5 billion, merged with another, doubling its mass. It then hooked up with another star of similar mass; they eventually coalesced to form a star with about four times the Sun’s mass. This found itself in another foursome, before merging again to make a still more massive star, which blew off much of its outer material and ended up, 4.3 billion years after the initial star formed, as a white dwarf.

This lurid case history "is not at all rare", say Hurley and Shara. Cluster stars are constantly reinventing themselves.

A star such as the Sun gets gradually hotter, bluer and brighter as it ages. But astronomical observations have revealed that many stars in clusters show a different relationship between colour, brightness and age.

For example, globular clusters contain so-called blue straggler stars. These are much older than the Sun but look, judging from their colour and brightness, almost as young. Merging with or cannibalizing other stars may rejuvenate blue stragglers. Indeed, Hurley and Shara say that, once a star has become a blue straggler, it is irresistible to others: subsequent relationships "are almost inevitable".

References

  1. Hurley, J. R. & Shara, M. M. The promiscuous nature of stars in clusters. Astrophysical Journal, 570, 184 - 189, (2002).

PHILIP BALL | © Nature News Service

More articles from Physics and Astronomy:

nachricht From the cosmos to fusion plasmas, PPPL presents findings at global APS gathering
13.11.2018 | DOE/Princeton Plasma Physics Laboratory

nachricht A two-atom quantum duet
12.11.2018 | Institute for Basic Science

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: A Chip with Blood Vessels

Biochips have been developed at TU Wien (Vienna), on which tissue can be produced and examined. This allows supplying the tissue with different substances in a very controlled way.

Cultivating human cells in the Petri dish is not a big challenge today. Producing artificial tissue, however, permeated by fine blood vessels, is a much more...

Im Focus: A Leap Into Quantum Technology

Faster and secure data communication: This is the goal of a new joint project involving physicists from the University of Würzburg. The German Federal Ministry of Education and Research funds the project with 14.8 million euro.

In our digital world data security and secure communication are becoming more and more important. Quantum communication is a promising approach to achieve...

Im Focus: Research icebreaker Polarstern begins the Antarctic season

What does it look like below the ice shelf of the calved massive iceberg A68?

On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.

Im Focus: Penn engineers develop ultrathin, ultralight 'nanocardboard'

When choosing materials to make something, trade-offs need to be made between a host of properties, such as thickness, stiffness and weight. Depending on the application in question, finding just the right balance is the difference between success and failure

Now, a team of Penn Engineers has demonstrated a new material they call "nanocardboard," an ultrathin equivalent of corrugated paper cardboard. A square...

Im Focus: Coping with errors in the quantum age

Physicists at ETH Zurich demonstrate how errors that occur during the manipulation of quantum system can be monitored and corrected on the fly

The field of quantum computation has seen tremendous progress in recent years. Bit by bit, quantum devices start to challenge conventional computers, at least...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

“3rd Conference on Laser Polishing – LaP 2018” Attracts International Experts and Users

09.11.2018 | Event News

On the brain’s ability to find the right direction

06.11.2018 | Event News

European Space Talks: Weltraumschrott – eine Gefahr für die Gesellschaft?

23.10.2018 | Event News

 
Latest News

The dawn of a new era for genebanks - molecular characterisation of an entire genebank collection

13.11.2018 | Life Sciences

Fish recognize their prey by electric colors

13.11.2018 | Life Sciences

Ultrasound Connects

13.11.2018 | Awards Funding

VideoLinks
Science & Research
Overview of more VideoLinks >>>