Astronomers have identified two fundamental transitions in the physics of stars related to age that may help further refine the Milky Way's age. The results appear in the 18 August 2006 issue of the journal Science, published by AAAS, the nonprofit science society.
Using the Hubble Space Telescope, Harvey B. Richer and colleagues peered into the faintest stars in the globular star cluster NGC 6397 with Hubble's advanced camera for five days to capture high-resolution images of the faint stars.
"The light from these faint stars is so dim that it is equivalent to that produced by a birthday candle on the Moon, as seen from Earth," says Richer of the University of British Columbia in Vancouver and lead author of the Science article.
"These are the deepest images yet taken of a globular star cluster," said Science Associate Editor Joanne Baker. "They present a double whammy that will appear in future textbooks.
"By tracing the tiniest and faintest members of the population of stars in the cluster, the study reports the threshold mass at which a star becomes large enough to burn hydrogen by fusion and, second, the onset of molecular hydrogen being formed in the cooling atmospheres of dying white dwarfs."
Both effects confirm earlier theoretical predictions.
The research revealed the mass that determines which stars will burn hydrogen through fusion and live many billions of years and which ones will never grow large enough to be self-sustaining. Stars that are not self-sustaining only live about 1 billion years at most.
Richer and colleagues also detected a characteristic change in the color of white dwarfs in the cluster that is related to the onset of molecular hydrogen being formed in the cooling atmospheres as the white dwarfs die.
With this information in hand, astronomers can learn more about the physics of low mass stars and white dwarfs and perhaps improve the estimate of the ages of these stars and the universe.
"These stars, which died long ago, were among the first to have formed in the universe," said Richer. "Pinning down their age narrows down the age range of the universe.
"We also will use the white dwarfs to determine the age of the cluster to an accuracy of a few hundred million years. This will eventually confront models of star formation in the early universe."
Richer will present the team's findings at a AAAS/Science press conference during the General Assembly of the International Astronomical Union in Prague, Czech Republic, on Thursday, 17 August, 2006.
Natasha Pinol | EurekAlert!
From the cosmos to fusion plasmas, PPPL presents findings at global APS gathering
13.11.2018 | DOE/Princeton Plasma Physics Laboratory
A two-atom quantum duet
12.11.2018 | Institute for Basic Science
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...
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...
On Saturday, 10 November 2018, the research icebreaker Polarstern will leave its homeport of Bremerhaven, bound for Cape Town, South Africa.
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...
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...
09.11.2018 | Event News
06.11.2018 | Event News
23.10.2018 | Event News
14.11.2018 | Materials Sciences
14.11.2018 | Health and Medicine
14.11.2018 | Life Sciences