Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

White Dwarf Lost in Planetary Nebula

05.06.2008
Call it the case of the missing dwarf.

A team of stellar astronomers is engaged in an interstellar CSI (crime scene investigation). They have two suspects, traces of assault and battery, but no corpse.


This image of the planetary nebula SuWt 2 reveals a bright ring-like structure encircling a bright central star. The central star is actually a close binary system where two stars completely circle each other every five days. The interaction of these stars and the more massive star that sheds material to create the nebula formed the ring structure. The burned-out core of the massive companion has yet to be found inside the nebula. The nebula is located 6,500 light-years from Earth in the direction of the constellation Centaurus. This color image was taken on Jan. 31, 1995 with the National Science Foundation's 1.5-meter telescope at the Cerro Tololo Inter-American Observatory (CTIO) in Chile. CTIO is part of the National Optical Astronomy Observatory, which has its headquarters in Tucson, Ariz.

The southern planetary nebula SuWt 2 is the scene of the crime, some 6,500 light-years from Earth in the direction of the constellation Centaurus.

SuWt 2 consists of a bright, nearly edge-on glowing ring of gas. Faint lobes extend perpendicularly to the ring, giving the faintest parts of the nebula an hourglass shape.

These glowing ejecta are suspected to have been energized by a star that has now burned out and collapsed to a white dwarf. But the white dwarf is nowhere to be found.

The mystery deepened when researchers obtained ultraviolet observations in the early 1990's with NASA's International Ultraviolet Explorer satellite, expecting to see signs of a faint but very hot star. But no ultraviolet radiation was detected.

Instead, at the center of the nebular ring are two suspicious characters: a pair of tightly bound stars that whirl around each other every five days, neither one of which is a white dwarf. These stars are hotter than our Sun (their spectral class is A), but they are still not hot enough to make the nebula glow. Only a flood of ultraviolet radiation, such as that from the missing white dwarf, could do that.

The study is being conducted by Katrina Exter and Howard Bond of the Space Telescope Science Institute in Baltimore, Md., and a team of British and American colleagues. Their extensive photometry and spectroscopy of the binary show that both stars are larger than main-sequence stars of their masses. This may imply that they have started to evolve toward becoming red giants. Both stars also appear to be rotating more slowly than expected; they would be expected to always be facing the same sides toward each other, but they do not.

The astronomers suggest a simple explanation for the facts at the scene: the stars at the center of SuWt 2 were born as a family of three, with the A stars circling each other tightly and a more massive star orbiting further out. This allowed room for the massive star to evolve to become a red giant, which only then engulfed the pair of A stars. Trapped inside the red giant in what astronomers call a "common envelope," the pair spiraled down toward the core, causing the envelope to spin faster. Eventually, the outer layers of the red giant were ejected in the plane of the orbit, producing the ring-shaped nebula seen today.

The unusually slow spins of the two A stars may have been another consequence of their victimization by their massive sibling.

The ground-based observations were obtained with telescopes at the Cerro Tololo Inter-American Observatory, Chile; the New Technology Telescope at the European Southern Observatory, Chile; the Anglo-Australian Telescope, Australia; and the South African Astronomical Observatory.

Ultraviolet radiation from the exposed hot core of the red giant would have caused the nebula to glow. If the giant's core were of high enough mass, it would then shrink and cool off rapidly to a faint white dwarf, which might explain its current invisibility.

Their results are being presented today at the 212th meeting of the American Astronomical Society in St. Louis, Mo. Other members of the team are Keivan Stassun (Vanderbilt University, Tenn.), Pierre Maxted and Barry Smalley (Keele University, UK), and Don Pollacco (Queen's University, UK).

The Hubble Space Telescope is a project of international cooperation between NASA and the European Space Agency (ESA) and is managed by NASA's Goddard Space Flight Center (GSFC) in Greenbelt, Md. The Space Telescope Science Institute (STScI) conducts Hubble science operations. The institute is operated for NASA by the Association of Universities for Research in Astronomy, Inc., Washington, DC.

Ray Villard | newswise
Further information:
http://hubblesite.org/news/2008/21
http://www.stsci.edu

More articles from Physics and Astronomy:

nachricht Seeing the quantum future... literally
16.01.2017 | University of Sydney

nachricht Airborne thermometer to measure Arctic temperatures
11.01.2017 | Moscow Institute of Physics and Technology

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: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

Im Focus: Newly proposed reference datasets improve weather satellite data quality

UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration

"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...

Im Focus: Repairing defects in fiber-reinforced plastics more efficiently

Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.

Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Multiregional brain on a chip

16.01.2017 | Power and Electrical Engineering

New technology enables 5-D imaging in live animals, humans

16.01.2017 | Information Technology

Researchers develop environmentally friendly soy air filter

16.01.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>