Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Alternative stellar lifestyle: Common, curious, solved at last

09.12.2015

Starting around 1950, a series of advances formed a clear and accepted picture of how individual stars are born, evolve and die. As they age, the changing patterns of color, light output, size and lifespan of stars are predictable. Every star like the sun will become a red giant, a planetary nebula and finally a white dwarf.

But half of all stars are in binaries -- pairs of stars that orbit each other. Half of binary stars orbit so close that gravitational interaction significantly affects their evolution and demise. Today, scientists led by Robert Mathieu, a professor of astronomy at the University of Wisconsin-Madison, and his former student Natalie Gosnell confirmed one of the possible explanations for a common group of exceptions: the blue stragglers.


Birth of a blue straggler star. Left: A normal star in a binary system gravitationally pulls in matter from an aging companion star that has swelled to a bloated red giant that is a few hundred times its original size. Right: After a couple hundred million years, the red giant star has burned out and collapsed to the white dwarf that shines intensely in ultraviolet wavelengths. The companion star has bulked up on hydrogen siphoned from the red giant to become much hotter, brighter and bluer.

Credit: NASA/ESA, A. Feild (STScI)

Blue stragglers look younger and brighter than their age would suggest -- skirting, in other words, the clean, clear rules of stellar evolution. Since their discovery in 1953, blue stragglers have been begging for explanation. Had two stars collided to form a more massive star? Was a blue straggler "stealing" gas from a companion star?

In recent years, based on observations at the WIYN telescope at Kitt Peak, Arizona, Mathieu and his students have established that over three-quarters of blue stragglers, in fact, have stellar companions.

This week, in a paper in The Astrophysical Journal, Gosnell, Mathieu and colleagues identified the orbital partner that was parasitized by the blue straggler. The victim, they found, was a red giant that donated hydrogen gas for eons until it was eventually transformed into a white dwarf -- the old, small, bright and dense remnant of a red giant.

The researchers used the Hubble Space Telescope to study the "colors" of far ultraviolet light coming from blue stragglers and their companions. At a distance of 5,500 light years, the blue straggler binary appears as a single point of light, but by analyzing the amount of ultraviolet light, the researchers saw the unmistakable signal of a white dwarf.

The study builds on a series of logical deductions. The stars being studied were identified as members of a binary pair because they periodically move closer to and further from Earth -- the hallmark of an orbiting pair of stars. Their optical color and intensity marked them as blue stragglers. They are bright in the far ultraviolet, a trademark of a hot white dwarf. And finally, for the white dwarfs to still be hot and detectable, they can only be 300 million years old. "These blue stragglers were formed 'yesterday,'" says Mathieu.

White dwarfs form when certain stars lose their outer atmospheres. The mass "must be going somewhere," Gosnell says, "and that's to the companion normal star, which is close enough to attract the mass through gravity. Therefore, the white dwarf is left over after adding mass to a star, which becomes the blue straggler."

The study expands our understanding of a major area of stellar evolution. If half of all stars are in binaries, and half of the binaries are, like the blue straggler, close enough to have gravitational interaction, then "these stars are not just an afterthought, a contaminant to our neat picture," Gosnell says. "We need to bring this 25 percent of all stars into the fold, so we can say we really understand how stars evolve."

If scientists don't know how the blue stragglers formed, they are in a poor position to understand how they will evolve and die, adds Gosnell, who is now a postdoctoral fellow at the University of Texas. "Of course, we still have a third of the blue stragglers to figure out. I think we also have some stellar collisions in there."

"Our understanding of single-star evolution is one of the great intellectual achievements of the last century," says Mathieu. "We began with points of light in the sky, and with the application of new instrumentation, the physics breakthroughs of the last century, and computers, we took those points of light and turned them into a narrative of star life.

"For the evolution of single stars like our sun, by and large, we got it right, from birth to death. Now we're starting to do the same thing for the one-quarter of stars that are close-orbiting binaries. This work allows us to talk not about points of light, but about the evolution of galaxies, including our own Milky Way. That's a big deal, and getting it right is an even bigger deal."

###

David Tenenbaum, 608-265-8549, djtenenb@wisc.edu

Robert Mathieu | EurekAlert!

More articles from Physics and Astronomy:

nachricht Tune your radio: galaxies sing while forming stars
21.02.2017 | Max-Planck-Institut für Radioastronomie

nachricht Breakthrough with a chain of gold atoms
17.02.2017 | Universität Konstanz

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: Breakthrough with a chain of gold atoms

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

In the field of nanoscience, an international team of physicists with participants from Konstanz has achieved a breakthrough in understanding heat transport

Im Focus: DNA repair: a new letter in the cell alphabet

Results reveal how discoveries may be hidden in scientific “blind spots”

Cells need to repair damaged DNA in our genes to prevent the development of cancer and other diseases. Our cells therefore activate and send “repair-proteins”...

Im Focus: Dresdner scientists print tomorrow’s world

The Fraunhofer IWS Dresden and Technische Universität Dresden inaugurated their jointly operated Center for Additive Manufacturing Dresden (AMCD) with a festive ceremony on February 7, 2017. Scientists from various disciplines perform research on materials, additive manufacturing processes and innovative technologies, which build up components in a layer by layer process. This technology opens up new horizons for component design and combinations of functions. For example during fabrication, electrical conductors and sensors are already able to be additively manufactured into components. They provide information about stress conditions of a product during operation.

The 3D-printing technology, or additive manufacturing as it is often called, has long made the step out of scientific research laboratories into industrial...

Im Focus: Mimicking nature's cellular architectures via 3-D printing

Research offers new level of control over the structure of 3-D printed materials

Nature does amazing things with limited design materials. Grass, for example, can support its own weight, resist strong wind loads, and recover after being...

Im Focus: Three Magnetic States for Each Hole

Nanometer-scale magnetic perforated grids could create new possibilities for computing. Together with international colleagues, scientists from the Helmholtz Zentrum Dresden-Rossendorf (HZDR) have shown how a cobalt grid can be reliably programmed at room temperature. In addition they discovered that for every hole ("antidot") three magnetic states can be configured. The results have been published in the journal "Scientific Reports".

Physicist Dr. Rantej Bali from the HZDR, together with scientists from Singapore and Australia, designed a special grid structure in a thin layer of cobalt in...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Booth and panel discussion – The Lindau Nobel Laureate Meetings at the AAAS 2017 Annual Meeting

13.02.2017 | Event News

Complex Loading versus Hidden Reserves

10.02.2017 | Event News

International Conference on Crystal Growth in Freiburg

09.02.2017 | Event News

 
Latest News

Impacts of mass coral die-off on Indian Ocean reefs revealed

21.02.2017 | Earth Sciences

Novel breast tomosynthesis technique reduces screening recall rate

21.02.2017 | Medical Engineering

Use your Voice – and Smart Homes will “LISTEN”

21.02.2017 | Trade Fair News

VideoLinks
B2B-VideoLinks
More VideoLinks >>>