The chemical uniformity of stars in the same cluster is the result of turbulent mixing in the clouds of gas where star formation occurs, according to a study by astrophysicists at the University of California, Santa Cruz. Their results, published August 31 in Nature, show that even stars that don't stay together in a cluster will share a chemical fingerprint with their siblings which can be used to trace them to the same birthplace.
"We can see that stars that are part of the same star cluster today are chemically identical, but we had no good reason to think that this would also be true of stars that were born together and then dispersed immediately rather than forming a long-lived cluster," said Mark Krumholz, professor of astronomy and astrophysics at UC Santa Cruz.
This computer simulation shows the collision of two streams of interstellar gas, leading to gravitational collapse of the gas and the formation of a star cluster at the center. The left side shows the density of interstellar gas (redder indicates higher density), and the right side shows the two "tracer dyes" added to show how the gas from the two streams mixes together during the collapse. Circles indicate stars.
Credit: Y. Feng and M. Krumholz
Our sun and its siblings, for example, probably went their own ways within a few million years after they were born, Krumholz said. The new study suggests that astronomers could potentially find the sun's long-lost siblings even if they are now on the opposite side of the galaxy.
Krumholz and UC Santa Cruz graduate student Yi Feng used supercomputers to simulate two streams of interstellar gas coming together to form a cloud that, over the course of a few million years, collapses under its own gravity to make a cluster of stars. Studies of interstellar gas show much greater variation in chemical abundances than is seen among stars within the same open star cluster. To represent this variation, the researchers added "tracer dyes" to the two gas streams in the simulations. The results showed extreme turbulence as the two streams came together, and this turbulence effectively mixed together the tracer dyes.
"We put red dye in one stream and blue dye in the other, and by the time the cloud started to collapse and form stars, everything was purple. The resulting stars were purple as well," Krumholz said. "This explains why stars that are born together wind up having the same abundances: as the cloud that forms them is assembled, it gets thoroughly mixed. This was actually a bit of a surprise. I didn't expect the turbulence to be as violent as it was, so I didn't expect the mixing to be as rapid or efficient. I thought we'd get some blue stars and some red stars, instead of getting all purple stars."
The simulations also showed that the mixing happens very fast, before much of the gas has turned into stars. This is encouraging for the prospects of finding the sun's siblings, because the distinguishing characteristic of stellar families that don't stay together is that they probably disperse before much of their parent cloud has been converted to stars. If the mixing didn't happen quickly enough, then the chemical uniformity of star clusters would be the exception rather than the rule. Instead, the simulations indicate that even clouds that don't turn much of their gas into stars produce stars with nearly identical chemical signatures.
"The idea of finding the siblings of the sun through chemical tagging is not new, but no one had any idea if it would work," Krumholz said. "The underlying problem was that we didn't really know why stars in clusters are chemically homogeneous, and so we couldn't make any sensible predictions about what would happen in the environment where the Sun formed, which must have been quite different from the environments that give rise to long-lived star clusters. This study puts the idea on much firmer footing and will hopefully spur greater efforts toward making use of this technique."
This research was supported by the National Science Foundation and NASA.
Tim Stephens | Eurek Alert!
Creation of coherent states in molecules by incoherent electrons
23.10.2017 | Tata Institute of Fundamental Research
Taming 'wild' electrons in graphene
23.10.2017 | Rutgers University
University of Maryland researchers contribute to historic detection of gravitational waves and light created by event
On August 17, 2017, at 12:41:04 UTC, scientists made the first direct observation of a merger between two neutron stars--the dense, collapsed cores that remain...
Seven new papers describe the first-ever detection of light from a gravitational wave source. The event, caused by two neutron stars colliding and merging together, was dubbed GW170817 because it sent ripples through space-time that reached Earth on 2017 August 17. Around the world, hundreds of excited astronomers mobilized quickly and were able to observe the event using numerous telescopes, providing a wealth of new data.
Previous detections of gravitational waves have all involved the merger of two black holes, a feat that won the 2017 Nobel Prize in Physics earlier this month....
Material defects in end products can quickly result in failures in many areas of industry, and have a massive impact on the safe use of their products. This is why, in the field of quality assurance, intelligent, nondestructive sensor systems play a key role. They allow testing components and parts in a rapid and cost-efficient manner without destroying the actual product or changing its surface. Experts from the Fraunhofer IZFP in Saarbrücken will be presenting two exhibits at the Blechexpo in Stuttgart from 7–10 November 2017 that allow fast, reliable, and automated characterization of materials and detection of defects (Hall 5, Booth 5306).
When quality testing uses time-consuming destructive test methods, it can result in enormous costs due to damaging or destroying the products. And given that...
Using a new cooling technique MPQ scientists succeed at observing collisions in a dense beam of cold and slow dipolar molecules.
How do chemical reactions proceed at extremely low temperatures? The answer requires the investigation of molecular samples that are cold, dense, and slow at...
Scientists from the Max Planck Institute of Quantum Optics, using high precision laser spectroscopy of atomic hydrogen, confirm the surprisingly small value of the proton radius determined from muonic hydrogen.
It was one of the breakthroughs of the year 2010: Laser spectroscopy of muonic hydrogen resulted in a value for the proton charge radius that was significantly...
23.10.2017 | Event News
17.10.2017 | Event News
10.10.2017 | Event News
23.10.2017 | Physics and Astronomy
23.10.2017 | Earth Sciences
23.10.2017 | Health and Medicine