Featured Research

from universities, journals, and other organizations

New Type Of Proto-Planetary Nebula Hints At Stellar Superwind

Date:
September 9, 1999
Source:
University Of Illinois At Urbana-Champaign
Summary:
The discovery of a new type of low-surface-brightness reflection nebula around aging stars has provided important clues about how stars lose mass and form planetary nebulae.

The discovery of a new type of low-surface-brightness reflection nebula around aging stars has provided important clues about how stars lose mass and form planetary nebulae. "The results from a recently completed optical imaging survey of proto-planetary nebula candidates has shown us that stars don't lose mass in a spherically symmetric way at the ends of their lives," said Margaret Meixner, a professor of astronomy at the University of Illinois. "Some other process of mass loss, such as an axisymmetric superwind, is occurring."

As certain types of stars age, their stellar winds create glowing envelopes of gas and dust called planetary nebulae. Intermediate-mass stars, like the sun, move through a transitional proto-planetary nebula stage on their way to becoming planetary nebulae. "One of the most significant changes that occurs during the transition is the emergence of axisymmetry in the circumstellar shell of gas and dust," Meixner said. "While most stars show a high degree of spherical symmetry, most planetary nebulae display either bipolar or elliptical symmetry. Therefore, the departure from spherical symmetry must take place somewhere along the evolutionary sequence between the two phases."

To investigate potential morphological trends during the transition, Meixner and colleagues Toshiya Ueta (a U. of I. graduate student) and Matthew Bobrowsky (a research scientist at Orbital Sciences Corp.) studied 27 candidate proto-planetary nebulae with the Hubble Space Telescope. "The Hubble's high-resolution imaging capabilities allowed us to identify low-surface-brightness reflection nebulosities around 21 of the candidate objects," Meixner said. "All 21 nebulae showed varying degrees of asphericity, and we clearly recognized two basic types of structure."

In the first type of structure, never before observed in proto-planetary nebulae, a bright, central star is embedded in a faint, elliptically elongated shell of gas and dust. In the second type, the central star is partially or completely obscured by a bipolar structure. "The fact that we see elliptical structures in addition to bipolar structures helps to constrain the time scale of when the shaping process occurred," Meixner said. "The intrinsic axisymmetry of these reflection nebulosities demonstrates that the axisymmetry frequently found in planetary nebulae predates the proto-planetary nebula phase."

Meixner and her colleagues suggest that the axisymmetry found in proto-planetary nebulae could be created by an equatorially enhanced stellar superwind. The onset of the superwind would initiate the morphological shift from spherical to axial symmetry, becoming more pronounced in planetary nebula.

Meixner presented her team's findings at a special conference on asymmetrical planetary nebulae, held Aug. 3-6 at the Massachusetts Institute of Technology.


Story Source:

The above story is based on materials provided by University Of Illinois At Urbana-Champaign. Note: Materials may be edited for content and length.


Cite This Page:

University Of Illinois At Urbana-Champaign. "New Type Of Proto-Planetary Nebula Hints At Stellar Superwind." ScienceDaily. ScienceDaily, 9 September 1999. <www.sciencedaily.com/releases/1999/09/990909080653.htm>.
University Of Illinois At Urbana-Champaign. (1999, September 9). New Type Of Proto-Planetary Nebula Hints At Stellar Superwind. ScienceDaily. Retrieved July 25, 2014 from www.sciencedaily.com/releases/1999/09/990909080653.htm
University Of Illinois At Urbana-Champaign. "New Type Of Proto-Planetary Nebula Hints At Stellar Superwind." ScienceDaily. www.sciencedaily.com/releases/1999/09/990909080653.htm (accessed July 25, 2014).

Share This




More Space & Time News

Friday, July 25, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

This Week @ NASA, July 25, 2014

This Week @ NASA, July 25, 2014

NASA (July 25, 2014) Apollo 11 celebration, Next Giant Leap anticipation, ISS astronauts appear in the House and more... Video provided by NASA
Powered by NewsLook.com
Space to Ground: Coming and Going

Space to Ground: Coming and Going

NASA (July 25, 2014) One station cargo ship leaves, another arrives, aquatic research and commercial spinoffs. Questions or comments? Use #spacetoground to talk to us. Video provided by NASA
Powered by NewsLook.com
How A Solar Flare Could Have Wrecked Earth's Electronics

How A Solar Flare Could Have Wrecked Earth's Electronics

Newsy (July 25, 2014) Researchers say if Earth had been a week earlier in its orbit around the sun, it would have taken a direct hit from a 2012 coronal mass ejection. Video provided by Newsy
Powered by NewsLook.com
Raw: ISS Cargo Ship Launches in Kazakhstan

Raw: ISS Cargo Ship Launches in Kazakhstan

AP (July 23, 2014) The Progress 56 cargo ship launched from the Baikonur Cosmodrome in Kazakhstan Wednesday. NASA says it will deliver cargo and crew supplies to the International Space Station. (July 23) Video provided by AP
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

Environment News

Technology News



Save/Print:
Share:

Free Subscriptions


Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

Get Social & Mobile


Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

Have Feedback?


Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
Mobile: iPhone Android Web
Follow: Facebook Twitter Google+
Subscribe: RSS Feeds Email Newsletters
Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins