Blue stragglers (ringed) are irresistable to others.
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.
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".
PHILIP BALL | © Nature News Service
The taming of the light screw
22.03.2019 | Max-Planck-Institut für Struktur und Dynamik der Materie
21.03.2019 | Max-Planck-Institut für Polymerforschung
DESY and MPSD scientists create high-order harmonics from solids with controlled polarization states, taking advantage of both crystal symmetry and attosecond electronic dynamics. The newly demonstrated technique might find intriguing applications in petahertz electronics and for spectroscopic studies of novel quantum materials.
The nonlinear process of high-order harmonic generation (HHG) in gases is one of the cornerstones of attosecond science (an attosecond is a billionth of a...
Nano- and microtechnology are promising candidates not only for medical applications such as drug delivery but also for the creation of little robots or flexible integrated sensors. Scientists from the Max Planck Institute for Polymer Research (MPI-P) have created magnetic microparticles, with a newly developed method, that could pave the way for building micro-motors or guiding drugs in the human body to a target, like a tumor. The preparation of such structures as well as their remote-control can be regulated using magnetic fields and therefore can find application in an array of domains.
The magnetic properties of a material control how this material responds to the presence of a magnetic field. Iron oxide is the main component of rust but also...
Due to the special arrangement of its molecules, a new coating made of corn starch is able to repair small scratches by itself through heat: The cross-linking via ring-shaped molecules makes the material mobile, so that it compensates for the scratches and these disappear again.
Superficial micro-scratches on the car body or on other high-gloss surfaces are harmless, but annoying. Especially in the luxury segment such surfaces are...
The Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) at the Large Binocular Telescope (LBT) in Arizona released its first image of the surface magnetic field of another star. In a paper in the European journal Astronomy & Astrophysics, the PEPSI team presents a Zeeman- Doppler-Image of the surface of the magnetically active star II Pegasi.
A special technique allows astronomers to resolve the surfaces of faraway stars. Those are otherwise only seen as point sources, even in the largest telescopes...
Researchers at Chalmers University of Technology and the University of Gothenburg, Sweden, have proposed a way to create a completely new source of radiation. Ultra-intense light pulses consist of the motion of a single wave and can be described as a tsunami of light. The strong wave can be used to study interactions between matter and light in a unique way. Their research is now published in the scientific journal Physical Review Letters.
"This source of radiation lets us look at reality through a new angle - it is like twisting a mirror and discovering something completely different," says...
11.03.2019 | Event News
01.03.2019 | Event News
28.02.2019 | Event News
22.03.2019 | Life Sciences
22.03.2019 | Life Sciences
22.03.2019 | Information Technology