Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Astronomers Discover New Type of Pulsating White Dwarf Star

05.05.2008
Discovery helps solve riddle of where the carbon white dwarfs come from, and what happens to their hydrogen and helium

University of Texas at Austin astronomers Michael H. Montgomery and Kurtis A. Williams, along with graduate student Steven DeGennaro, have predicted and confirmed the existence of a new type of variable star, with the help of the 2.1-meter Otto Struve Telescope at McDonald Observatory. The discovery is announced in today's issue of Astrophysical Journal Letters.

This research was funded by the National Science Foundation and the Delaware Asteroseismic Research Center.

Called a "pulsating carbon white dwarf," this is the first new class of variable white dwarf star discovered in more than 25 years. Because the overwhelming majority of stars in the universe--including the sun--will end their lives as white dwarfs, studying the pulsations (i.e., variations in light output) of these newly discovered examples gives astronomers a window on an important end point in the lives of most stars.

A white dwarf star is the leftover remnant of a sun-like star that has burned all of the nuclear fuel in its core. It is extremely dense, packing half to 1.5 times the sun's mass into a volume about the size of Earth. Until recently, there were thought to be two main types of white dwarfs: those with an outer layer of hydrogen (about 80 percent of white dwarfs), and those with an outer layer of helium, whose hydrogen shells have somehow been stripped away (the other 20 percent).

Last year, University of Arizona astronomers Patrick Dufour and James Liebert discovered a third type of white dwarf star. For reasons that are not understood, these "hot carbon white dwarfs" have had both their hydrogen and helium shells stripped off, leaving their carbon layer exposed. Astronomers suspect that these could be among the most massive white dwarfs of all, the remnants of stars slightly too small to end their lives in a supernova explosion.

After these new carbon white dwarfs were announced, Montgomery calculated that pulsations in these stars were possible. Pulsating stars are of interest to astronomers because the changes in their light output can reveal what goes on in their interiors--similar to the way geologists study seismic waves from earthquakes to understand what goes on in Earth's interior. In fact, this type of star-study is called "asteroseismology."

So, Montgomery and Williams' team began a systematic study of carbon white dwarfs with the Struve Telescope at McDonald Observatory, looking for pulsators. DeGennaro discovered that a star about 800 light-years away in the constellation Ursa Major, called SDSS J142625.71+575218.3, fits the bill. Its light intensity varies regularly by nearly two percent about every eight minutes.

"The discovery that one of these stars is pulsating is remarkably important," said NSF astronomer Michael Briley. "This will allow us to probe the white dwarf's interior, which in turn should help us solve the riddle of where the carbon white dwarfs come from and what happens to their hydrogen and helium."

The star lies about ten degrees east northeast of Mizar, the middle star in the handle of the Big Dipper. This white dwarf has about the same mass as our Sun, but its diameter is smaller than Earth's. The star has a temperature of 35,000 degrees Fahrenheit (19,500 C), and is only 1/600th as bright as the Sun.

None of the other stars in their sample were found to pulsate. Given the masses and temperatures of the stars in their sample, SDSS J142625.71+575218.3 is the only one expected to pulsate, based on Montgomery's calculations.

The astronomers speculate that the pulsations are caused by changes in the star's carbon outer envelope as the star cools down from its formation as a hot white dwarf. The ionized carbon atoms in the star's outer layers return to a neutral state, triggering the pulsations.

There is a chance that the star's variations might have another cause. Further study is needed, the astronomers say. Either way, studying these stars will shed light on the unknown process that strips away their surface layers of hydrogen and helium to lay bare their carbon interiors.

Diane Banegas | EurekAlert!
Further information:
http://www.nsf.gov

More articles from Physics and Astronomy:

nachricht APEX takes a glimpse into the heart of darkness
25.05.2018 | Max-Planck-Institut für Radioastronomie

nachricht First chip-scale broadband optical system that can sense molecules in the mid-IR
24.05.2018 | Columbia University School of Engineering and Applied 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: Powerful IT security for the car of the future – research alliance develops new approaches

The more electronics steer, accelerate and brake cars, the more important it is to protect them against cyber-attacks. That is why 15 partners from industry and academia will work together over the next three years on new approaches to IT security in self-driving cars. The joint project goes by the name Security For Connected, Autonomous Cars (SecForCARs) and has funding of €7.2 million from the German Federal Ministry of Education and Research. Infineon is leading the project.

Vehicles already offer diverse communication interfaces and more and more automated functions, such as distance and lane-keeping assist systems. At the same...

Im Focus: Molecular switch will facilitate the development of pioneering electro-optical devices

A research team led by physicists at the Technical University of Munich (TUM) has developed molecular nanoswitches that can be toggled between two structurally different states using an applied voltage. They can serve as the basis for a pioneering class of devices that could replace silicon-based components with organic molecules.

The development of new electronic technologies drives the incessant reduction of functional component sizes. In the context of an international collaborative...

Im Focus: LZH showcases laser material processing of tomorrow at the LASYS 2018

At the LASYS 2018, from June 5th to 7th, the Laser Zentrum Hannover e.V. (LZH) will be showcasing processes for the laser material processing of tomorrow in hall 4 at stand 4E75. With blown bomb shells the LZH will present first results of a research project on civil security.

At this year's LASYS, the LZH will exhibit light-based processes such as cutting, welding, ablation and structuring as well as additive manufacturing for...

Im Focus: Self-illuminating pixels for a new display generation

There are videos on the internet that can make one marvel at technology. For example, a smartphone is casually bent around the arm or a thin-film display is rolled in all directions and with almost every diameter. From the user's point of view, this looks fantastic. From a professional point of view, however, the question arises: Is that already possible?

At Display Week 2018, scientists from the Fraunhofer Institute for Applied Polymer Research IAP will be demonstrating today’s technological possibilities and...

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

In focus: Climate adapted plants

25.05.2018 | Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

 
Latest News

In focus: Climate adapted plants

25.05.2018 | Event News

Flow probes from the 3D printer

25.05.2018 | Machine Engineering

Less is more? Gene switch for healthy aging found

25.05.2018 | Life Sciences

VideoLinks
Science & Research
Overview of more VideoLinks >>>