“Kitchen Smoke” Molecules in Nebula Offer Clues to the Building Blocks of Life

Combination of three color images of NGC 7023 from SOFIA (red & green) and Spitzer (blue) show different populations of PAH molecules. Credits: NASA/DLR/SOFIA/B. Croiset, Leiden Observatory, and O. Berné, CNRS; NASA/JPL-Caltech/Spitzer.

Using data collected by NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) and other observatories, an international team of researchers has studied how a particular type of organic molecules, the raw materials for life – could develop in space. This information could help scientists better understand how life could have developed on Earth.

Bavo Croiset of Leiden University in the Netherlands and his collaborators focused on a type of molecule called polycyclic aromatic hydrocarbons (PAHs), which are flat molecules consisting of carbon atoms arranged in a honeycomb pattern, surrounded by hydrogen. PAHs make up about 10 percent of the carbon in the universe, and are found on the Earth where they are released upon the burning of organic material such as meat, sugarcane, wood etc.  Croiset’s team determined that when PAHs in the nebula NGC 7023, also known as the Iris Nebula, are hit by ultraviolet radiation from the nebula’s central star, they evolve into larger, more complex molecules. Scientists hypothesize that the growth of complex organic molecules like PAHs is one of the steps leading to the emergence of life.

Some existing models predicted that the radiation from a newborn, nearby massive star would tend to break down large organic molecules into smaller ones, rather than build them up. To test these models, researchers wanted to estimate the size of the molecules at various locations relative to the central star.

Croiset’s team used SOFIA to observe Nebula NGC 7023 with two instruments, the FLITECAM near-infrared camera and the FORCAST mid-infrared camera. SOFIA’s instruments are sensitive to two wavelengths that are produced by these particular molecules, which can be used to estimate their size. The team analyzed the SOFIA images in combination with data previously obtained by the Spitzer infrared space observatory, the Hubble Space Telescope and the Canada-France-Hawaii Telescope on the Big Island of Hawaii.

The analysis indicates that the size of the PAH molecules in this nebula vary by location in a clear pattern. The average size of the molecules in the nebula’s central cavity, surrounding the illuminating star, is larger than on the surface of the cloud at the outer edge of the cavity.

In a paper published in Astronomy and Astrophysics, The team concluded that this molecular size variation is due both to some of the smallest molecules being destroyed by the harsh ultraviolet radiation field of the star, and to medium-sized molecules being irradiated so they combine into larger molecules. Researchers were surprised to find that the radiation resulted in net growth, rather than destruction.

“The success of these observations depended on both SOFIA’s ability to observe wavelengths inaccessible from the ground, and the large size of its telescope, which provided a more detailed map than would have been possible with smaller telescopes,” said Olivier Berné at CNRS, the National Center for Scientific Research in Toulouse, France, one of the published paper’s co-authors.

For more information on SOFIA, go to: www.nasa.gov/sofia

For more information SOFIA Science, go to: https://www.sofia.usra.edu/

Dr. Dana Backman
SOFIA Science Center, NASA Ames Research Center, Moffett Field, California

Kassandra Bell
SOFIA Science Center, NASA Ames Research Center, Moffett Field, California

Editor: Kassandra Bell

Source: NASA/SOFIA

Need to Track Organic Nano-Particles Across the Universe? NASA's Got an App for That

Image of a nebula taken by NASA’s Spitzer Space Telescope.

Image Credit: NASA/Jet Propulsion Laboratory

 

Scientists at NASA's Ames Research Center in Moffett Field, Calif., today released a significant expansion and upgrade to a public, online database that houses a unique and extensive collection of information about a family of complex, carbon-rich molecules that are both widespread and abundant throughout the universe. Scientists believe more than 20 percent of the carbon in the universe is tied up in this extensive family of compounds, collectively know as polycyclic aromatic hydrocarbons, or simply PAHs.

Using the Ames-developed PAH Infrared Spectroscopic Database, scientists will now have access to data on hundreds more compounds and several powerful new tools –including an advanced web app and a dedicated astronomical software package – to map the distribution of this life-essential element and track its role across the universe.

"Analyzing the PAH emission bands with the web app, new tools, and expanded database provides a powerful new way for astronomers to trace the evolution of cosmic carbon and, at the same time, probe conditions across the universe,” said Christiaan Boersma, a research fellow at Ames who designed and developed many parts of the web app and tools. "We have expanded the computational spectral collection to 700 spectra, including those of extremely large PAHs composed of hundreds of carbon atoms, and the experimental collection to 75 spectra."

Over the past 20 years, NASA scientists experimentally measured and computed PAH spectroscopic signatures to track and analyze the unexpected, widespread PAH emission originating from deep space. NASA made the original collection of spectra and accompanying software available online four years ago.

The approach of analyzing the infrared spectra emitted by everything from dying stars to clouds of gas and dust to entire galaxies using the one-two punch of known PAH spectra and the new, blind, algorithm-driven codes now available, provides a unique look into the evolution of cosmic PAHs.

In addition to substantially increasing the number of spectra available, the new version of the database includes powerful, astronomer-friendly tools that mimic the PAHs’ response to the local space environment and makes it possible to understand which types of PAHs are present in different regions of space. It also allows astronomers to tie these evolutionary changes to variations in local conditions such as those due to the radiation field, physical shape and history of the region.

"PAHs are so widespread and abundant in space that they don't just witness the conditions in their cosmic neighborhoods, they are active participants in many astronomical phenomena," said Louis Allamandola, an astrophysics researcher at Ames. "PAHs both are an important source of carbon for young, primordial planets, and influence how quickly they can form. For example, very bright PAH emission comes from places where new stars and exo-planets are forming."

NASA's Spitzer Space Telescope managed and operated by NASA's Jet Propulsion Laboratory in Pasadena, Calif., detected the PAH signature across the universe and showed PAHs were already forming only a couple of billion years after the Big Bang. Because their spectral signature is very sensitive to their local environment, especially radiation levels, the temperatures of PAHs in space can vary from nearly minus 450 degrees Fahrenheit to roughly 1,000 degrees, after which they break apart.

“Since PAHs are so sensitive to local conditions, analyzing the PAH bands as we did here represents a powerful new astronomical tool to trace the evolution of cosmic carbon and, at the same time, probe conditions in objects spanning the universe,” said Allamandola.

The upgraded database allows scientists to determine how the PAH signature changes across this vast range of temperatures. Astronomers need simply to upload the spectra of their favorite celestial object into the website and see which PAH classes are needed to reproduce their spectra.

"This capability is a major step forward because it allows astronomers to directly tie their astronomical spectra to the spectra of individual, bona-fide PAHs, not generic, model dependent, mythical, cosmic material," said Allamandola. "And they can do all this on their mobile devices like iPads and iPhones, as well as personal computers."

PAHs in space are probably made the same way soot is made in the combustion engines that power trucks and cars here on Earth. In addition to astronomical applications, the expanded PAH database and powerful new software also is a useful research tool for scientists, educators, policy makers, and consultants working in the fields of medicine, health, chemistry, fuel composition, engine design, environmental assessment, environmental monitoring and protection, and nanotechnology.

This work was supported by NASA's Astrobiology and Laboratory Astrophysics Programs and Carbon in the Galaxy Consortium under the auspices of the Astrophysics Research and Analysis Program.

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Rachel Hoover
NASA's Ames Research Center, Moffett Field, Calif.

Blushing Dusty Nebula

This close-up of an area in the northwest region of the large Iris Nebula seems to be clogged with cosmic dust. With bright light from the nearby star HD 200775 illuminating it from above, the dust resembles thick mounds of billowing cotton. It is actually made up of tiny particles of solid matter, with sizes from ten to a hundred times smaller than those of the dust grains we find at home. Both background and foreground stars are dotted throughout the image. Researchers studying the object are particularly interested in the region to the left and slightly above centre in the image, where dusty filaments appear redder than is expected.

North is down, East is right. The field of view is 3.3 arcminutes. The image is a composite of four images obtained through blue, green, near-infrared and H-alpha filters.Credit: NASA & ESA

Images: Image 1 -Image 2 - Print Layout

Videos: Video 1 - Video 2

A recent NASA/ESA Hubble Space Telescope image of part of NGC 7023, or the Iris Nebula, highlights a perfect dust laboratory in the sky.

On Earth, we tend to find dust nothing more than a nuisance that blankets our furniture and causes us to sneeze. Cosmic dust can also be a hindrance to astronomers because cameras using visible light cannot see through it. However, studying cosmic dust in detail helps astronomers to pin down the ingredients of the raw mixture that eventually gives birth to stars.

This close-up of an area in the northwest region of the large Iris Nebula seems to be clogged with cosmic dust. With bright light from the nearby star HD 200775 [1] illuminating it from above, the dust resembles thick mounds of billowing cotton. It is actually made up of tiny particles of solid matter, with sizes from ten to a hundred times smaller than those of the dust grains we find at home [2]. Both background and foreground stars are dotted throughout the image.

NGC 7023 is a reflection nebula, which means it scatters light from a massive nearby star, in this case, HD 200775. Reflection nebulae are different from emission nebulae, which are clouds of gas that are hot enough to emit light themselves. Reflection nebulae tend to appear blue because of the way light scatters, but parts of the Iris Nebula appear unusually red.

Researchers studying the object are particularly interested in the region to the left and slightly above centre in the image, where they find dusty filaments to be redder than expected. An unknown chemical compound, most likely based on hydrocarbons, is responsible for the red tinge. The high resolution and sensitivity of Hubble’s instruments allow astronomers to study the area in detail. Images and spectra are only part of the analysis. On Earth, scientists are performing additional laboratory tests to assess better the exact chemical composition of the nebula.

NGC 7023 was discovered by Sir William Herschel in 1794; the nebula is in the constellation of Cepheus, the King, in the northern sky. NGC 7023 is approximately 1400 light–years from Earth and about six light-years across. This aethereal image was taken by Hubble's Advanced Camera for Surveys. Astronomers also used Hubble’s Near Infrared Camera and Multi-Object Spectrometer (NICMOS) instrument to try to determine which chemical elements are present in the nebula.

Notes for editors:

North is down, East is right. The field of view is 3.3 arcminutes. The image is a composite of four images obtained through blue, green, near-infrared and H-alpha filters.

[1] HD 200775 is about ten times the mass of the Sun.

[2] The typical sizes of cosmic dust grains range between a few hundredths of a micron and several microns.

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

These observations were obtained by a team led by Karl Gordon from the Space Telescope Science Institute in Baltimore, Maryland, USA.

Contacts:

Colleen Sharkey
Hubble/ESA, Garching, Germany
Tel: +49 89 3200 6306
Cell: +49 151 153 73591
E-mail: csharkey@eso.org