Featured Research

from universities, journals, and other organizations

Star With Midriff Bulge Eyed By Astronomers

Date:
July 27, 2001
Source:
NASA/Jet Propulsion Laboratory
Summary:
For the first time ever, a star spinning so fast its mid-section is stretched out has been directly measured by an ultra-high-resolution NASA telescope system on Palomar Mountain near San Diego.

For the first time ever, a star spinning so fast its mid-section is stretched out has been directly measured by an ultra-high-resolution NASA telescope system on Palomar Mountain near San Diego.

"Measuring the shape of this star, Altair, was as difficult as standing in Los Angeles, looking at a hen's egg in New York, and trying to prove that it's oval-shaped and not circular," said Dr. Charles Beichman, chief scientist for astronomy and physics at NASA's Jet Propulsion Laboratory, Pasadena, Calif.

Altair is a well-known member of the Summer Triangle, clearly visible in the summer night sky across the United States. Scientists using the Palomar Testbed Interferometer, which links multiple telescopes, measured the star's radius at different angles on the sky. They noticed the size of the star varied with changing angles, which was the first tip-off that Altair is not perfectly round.

"This surprising observation led to a bit of challenging detective work to properly interpret the data," said principal investigator Dr. Gerard van Belle of JPL. "We measured the size of another star, Vega, at the same time, which didn't change with angle, so we knew this wasn't just a fluke of the telescope."

Previous studies of Altair raised the prospect that the star might have midriff bulge, but never before had the shape been measured directly. Earlier measurements of the star's spectrum, or light-wave pattern, had hinted that Altair was rotating very fast. When a gaseous orb, like a star, spins fast enough, it tends to expand at the middle, like a beach ball that is squeezed at the top and bottom.

Altair is a perfect example -- it rotates at least once every 10.4 hours, and the new Palomar observations reveal the diameter at its equator is at least 14 percent greater than at its poles. For a star that spins slowly, this effect is miniscule. For example, our Sun rotates once every 30 days and has an equator only .001 percent greater in diameter than its poles.

By measuring Altair's size at separate positions along its edge, van Belle and his colleagues determined that Altair rotates at a speed of at least 210 kilometers per second (470,000 miles per hour) at the equator. Future studies may pin down the speed more precisely.

"Determining the shape of another star helps us learn about the forces that control the shape and structure of all stars, including our star, the Sun," Beichman said. "This tells us more about the Sun's behavior and ultimate fate."

The Palomar Testbed Interferometer has three 50-centimeter (20-inch) telescopes. To study Altair, the telescopes were used two at a time. The combined light from the telescope pairs provided sharpness comparable to a telescope as large as a football field.

"Altair is the twelfth brightest star in the sky -- you'd think that everything there is to know about this star would have been discovered already," said co-investigator Dr. David Ciardi of the University of Florida, Gainesville. "It's a good example of the surprises you're going to encounter when you are able to look at even familiar stars with unprecedented resolution."

The Palomar Testbed Interferometer is paving the way for the Keck Interferometer, Space Interferometry Mission and Terrestrial Planet Finder, all part of NASA's Origins program. The program will hunt for Earthlike planets that might harbor life around other stars. "In the long run, we'll use these interferometric capabilities to search for planets around nearby stars. This is an important first step," said Beichman.

Van Belle and Ciardi co-authored the Altair paper, scheduled to appear in the October 1 issue of the Astrophysical Journal, with Robert Thompson of JPL and the University of Wyoming, Laramie; Dr. Rachel Akeson of the JPL/Caltech Infrared Processing and Analysis Center, Pasadena, Calif.; and Dr. Elizabeth Lada of the University of Florida, Gainesville.

Their research was funded by NASA's Office of Space Science, Washington, D.C., along with the National Science Foundation. Palomar Observatory is owned and operated by the California Institute of Technology in Pasadena, which also manages JPL for NASA. The Palomar Testbed Interferometer was designed and built by a team of JPL researchers led by Drs. Mark Colavita and Michael Shao. Funded by NASA and managed by JPL, the interferometer is located at the Palomar Observatory near the historic 200-inch Hale Telescope.

Images and animation of Altair are available at http://www.jpl.nasa.gov/images/stars/index.html . Information on the Palomar Testbed Interferometer is available at http://huey.jpl.nasa.gov/palomar . Information on NASA's Origins Program is available at http://origins.jpl.nasa.gov .


Story Source:

The above story is based on materials provided by NASA/Jet Propulsion Laboratory. Note: Materials may be edited for content and length.


Cite This Page:

NASA/Jet Propulsion Laboratory. "Star With Midriff Bulge Eyed By Astronomers." ScienceDaily. ScienceDaily, 27 July 2001. <www.sciencedaily.com/releases/2001/07/010727094638.htm>.
NASA/Jet Propulsion Laboratory. (2001, July 27). Star With Midriff Bulge Eyed By Astronomers. ScienceDaily. Retrieved July 23, 2014 from www.sciencedaily.com/releases/2001/07/010727094638.htm
NASA/Jet Propulsion Laboratory. "Star With Midriff Bulge Eyed By Astronomers." ScienceDaily. www.sciencedaily.com/releases/2001/07/010727094638.htm (accessed July 23, 2014).

Share This




More Space & Time News

Wednesday, July 23, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Raw: Cargo Craft Undocks from Space Station

Raw: Cargo Craft Undocks from Space Station

AP (July 22, 2014) A Russian Soyuz cargo-carrying spacecraft undocked from the International Space Station on Monday. The craft is due to undergo about ten days of engineering tests before it burns up in the Earth's atmosphere. (July 22) Video provided by AP
Powered by NewsLook.com
NASA Ceremony Honors Moon Walker Neil Armstrong

NASA Ceremony Honors Moon Walker Neil Armstrong

AP (July 21, 2014) NASA honored one of its most famous astronauts Monday by renaming a historic building at the Kennedy Space Center in Florida. It now bears the name of Neil Armstrong, the first man to walk on the moon. (July 21) Video provided by AP
Powered by NewsLook.com
Neil Armstrong's Post-Apollo 11 Life

Neil Armstrong's Post-Apollo 11 Life

Newsy (July 19, 2014) Neil Armstrong gained international fame after becoming the first man to walk on the moon in 1969. But what was his life like after the historic trip? Video provided by Newsy
Powered by NewsLook.com
This Week @ NASA, July 18, 2014

This Week @ NASA, July 18, 2014

NASA (July 18, 2014) Apollo 11 yesterday, Next Giant Leap tomorrow, Science instruments for Europa mission, and more... Video provided by NASA
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