Researchers have found evidence suggesting that stars rich in carbon complex molecules may form at the center of our Milky Way galaxy - and it helps solve a mystery. Namely, why have telescopes never detected carbon-rich stars at the center of our galaxy even though they have found these stars in other places?
This discovery is also significant because it adds to our knowledge of how stars form heavy elements like oxygen, carbon and iron and and then blow them out across the universe, making it possible for life to develop.
The team of scientists analyzed the light emitted from 40 planetary nebulae – blobs of dust and gas surrounding stars -- using Spitzer's infrared spectrograph. They analyzed 26 nebulae toward the center of the Milky Way -- a region called the "Galactic Bulge" -- and 14 nebulae in other parts of the galaxy. The scientists found a large amount of crystalline silicates and polycyclic aromatic hydrocarbons, two substances that indicate the presence of oxygen and carbon.
The "Cat’s Eye" nebula, or NGC 6543, is a well-studied example of a "planetary nebula." Such objects are the glowing remnants of dust and gas expelled from moderate-sized stars during their last stages of life. Our own sun will generate such a nebula in about five billion years. NASA’s Spitzer Space Telescope has studied many such planetary nebulae in infrared light, including a variety of more distant ones, which have helped scientists identify a population of carbon-bearing stars near our galaxy's center. The infrared emission from the Cat's Eye is generated by a variety of elements and molecules. The bright inner region of this nebula shows a complex structure reminiscent of a feline eye. Outside this compact region lies a series of other structures representing material that was ejected slightly earlier in the central star's life, when it was a giant star. The image is a composite of data from Spitzer’s infrared array camera. Light with a wavelength of 3.6 microns is rendered as blue, 5.8 microns is displayed as green and 8.0 microns is represented in red. The brightness of the central area has been greatly reduced to make it possible to maintain its visibility while enhancing the brightness of the much fainter outer features. Overall colors have been enhanced to better show slight variations in hue. Credit: NASA/JPL
This combination is unusual. In the Milky Way, dust that combines both oxygen and carbon is rare and is usually only found surrounding a binary system of stars. The research team, however, found that the presence of the carbon-oxygen dust in the Galactic Bulge seems to be suggestive of a recent change of chemistry experienced by the star.
"The dust surrounding the stars emits very strongly at infrared wavelengths," says Pedro García-Lario, a research team member who is on the faculty of the European Space Astronomy Center, the European Space Agency's center for space science. He co-authored a paper on this subject in the February 2009 issue of the journal Astronomy&Astrophysics.
The scientists hypothesize that as the central star of a planetary nebula ages and dies, its heavier elements do not make their way to the star's outer layers, as they do in other stars. Only in the last moments of the central star's life, when it expands and then violently expels almost all of its remaining outer gasses, does the carbon become detectable. That's when astronomers see it in the nebula surrounding the star.
"The carbon produced through these recurrent 'thermal pulses' is very inefficiently dredged up to the surface of the star, contrary to what is observed in low-metallicity, galactic disk stars," said García-Lario. "It only becomes visible when the star is about to die."
This study supports a hypothesis about why the carbon in some stars does not make its way to the stars' surfaces. Scientists believe that small stars -- those with masses up to one-and-a-half times that of our sun -- that contain lots of metal do not bring carbon to their surfaces as they age. Stars in the Galactic Bulge tend to have more metals than other stars, so the Spitzer data support this commonly held hypothesis. Before the Spitzer study, this hypothesis had never been supported by observation.
This aging and expelling process is typical of all stars. As stars age and die, they burn progressively heavier and heavier elements, beginning with hydrogen and ending with iron. Towards the end of their lives, some stars become what are called "red giants." These dying stars swell so large that if one of them were placed in our solar system, where the sun is now, its outermost border would touch Earth's orbit. As these stars pulsate – losing mass in the process – and then contract, they spew out almost all of their heavier elements. These elements are the building blocks of all planets, including our own Earth (as well as of human beings and any other life forms that may exist in the universe).
The paper is co-authored by José Vicente Perea-Calderón of the European Space Astronomy Center in Villanueva de la Cañada, Spain; Domingo Anibal García-Hernández of the Instituto de Astrofísica de Canarias, on Spain's Tenerife island; Ryszard Szczerba of the Nicolaus Copernicus Astronomical Center in Torun, Poland; and Matt Bobrowsky of the University of Maryland, College Park.
NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Spitzer Space Telescope mission for NASA's Science Mission Directorate, Washington. Science operations are conducted at the Spitzer Science Center at the California Institute of Technology, also in Pasadena. Caltech manages JPL for NASA.
- PHYSICAL SCIENCES
- EARTH SCIENCES
- LIFE SCIENCES
- SOCIAL SCIENCES
Subscribe to the newsletter
Stay in touch with the scientific world!
Know Science And Want To Write?
- Is The X(5568) A True Resonance ?
- The Five Stages Of A Dying Theory
- Chess is Smart and Sexy! The Mysterious Psychology of Chess Intelligence 2/3
- Should Pregnant Women Be Concerned About BPA?
- Something is wrong in the Arctic
- Order Patterned With Chaos - How Climate Is Predicted For Decades - With Exact Forecasts Only For Days
- Baby Boomers Unbound: Marijuana Surges In The Elderly
- "Hi mr walker quick question is nibiru real alot of people saying it is sorry to bother you im just..."
- "Anybody else having problems trying to see comments ..."
- "Anybody else having problems reading comments on here ..."
- "I might also mention Trump's wall to protect his Scottish golf course from climate change flooding..."
- "I though Calsen has been on top since 2013...."
- The Alzheimer's-Amyloid Hypothesis Confirmed? Not So Fast
- Abortion Rate in U.S. Falls 21% in One Decade
- Child Mummy May Change Timeline for Smallpox
- On Proposed Tanning Bed Ban for Teens, New Study Urges FDA to Act
- Fear Of Dying Got You Down? Retail Therapy Can Help
- It’s Not Brain Surgery, But do you Know What is? Brain Surgery!