Organic conundrum in Large Magellanic Cloud

Jun 23, 2014 by Robert Massey
Spitzer image of the Large Magellanic Cloud. Credit: NASA/JPL-Caltech/STScI

(Phys.org) —A group of organic chemicals that are considered carcinogens and pollutants today on Earth, but are also thought to be the building blocks for the origins of life, may hold clues to how carbon-rich chemicals created in stars are processed and recycled in space.

Scientists have studied how polycyclic aromatic hydrocarbons (PAHs) are created in an aging population of stars in the Milky Way's , the Large Magellanic Cloud. They have found that the types of PAH found in the atmospheres of these stars are much more varied than the PAHs observed in our own galaxy. The results will be presented by Dr Mikako Matsuura of UCL on Monday 23 June at the National Astronomy Meeting in Portsmouth.

"We were surprised because previous measurements of PAHs in in the Large Magellanic Cloud were very similar to those in the Milky Way," said Matsuura. "Our studies suggest these organic molecules are processed and change their composition soon after they are ejected by dying stars to fill the matter within the galaxy. Dying stars in the neighbouring galaxy are richer in carbon than the Milky Way's stars, so are more likely to trigger these wide varieties of organic compounds."

Matsuura and an international team observed 24 carefully selected stars with the Spitzer Space Telescope and analysed the light to find features linked to PAHs. Stars are powered by nuclear fusion in their cores, converting hydrogen to helium. Towards the end of their life, low-mass stars like the Sun consume all their hydrogen in the stellar core and start to convert helium to oxygen and carbon. Eventually, they run out of fuel and expel their outer layers, creating a nebula around a central white dwarf. The gas and molecules from this nebula are mixed over time into the Interstellar Medium. The team focused their study on that appeared to be in the process of fusing carbon.

"We think that, as the central star evolves, the increasingly energetic radiation effects the compositions of the PAHs, leading to more varieties. However, once the PAHs are mixed into the Interstellar medium, this variability decreases," said Matsuura. "One possibility for this contrast is that ultraviolet radiation might change the profiles of the PAHs. Another is that PAHs are re-processed further in the Interstellar Medium, changing their composition."

Explore further: New molecules around old stars

add to favorites email to friend print save as pdf

Related Stories

New molecules around old stars

Jun 17, 2014

(Phys.org) —Using ESA's Herschel space observatory, astronomers have discovered that a molecule vital for creating water exists in the burning embers of dying Sun-like stars.

Image: Glowing jewels in the galactic plane

Apr 29, 2014

The majority of the stars in our Galaxy, the Milky Way, reside in a single huge disc, known as the Galactic Plane, spanning 100 000 light-years across. The Sun also resides in this crowded stellar hub, lying ...

3D map shows dusty structure of the Milky Way

Jun 23, 2014

(Phys.org) —A team of international astronomers has created a detailed three-dimensional map of the dusty structure of the Milky Way – the star-studded bright disc of our own galaxy – as seen from Earth's ...

NASA develops key to cosmic carbon's molecular evolution

May 14, 2013

(Phys.org) —Scientists at NASA's Ames Research Center, Moffett Field, Calif., now have the capability to systematically investigate the molecular evolution of cosmic carbon. For the first time, these scientists ...

The 'Serpent' star-forming cloud hatches new stars

May 30, 2014

(Phys.org) —Stars that are just beginning to coalesce out of cool swaths of dust and gas are showcased in this image from NASA's Spitzer Space Telescope and the Two Micron All Sky Survey (2MASS). Infrared ...

Recommended for you

Can astronomy explain the biblical Star of Bethlehem?

Dec 24, 2014

Bright stars top Christmas trees in Christian homes around much of the world. The faithful sing about the Star of Wonder that guided the wise men to a manger in the little town of Bethlehem, where Jesus was ...

Hubbles spies the beautiful galaxy IC 335

Dec 24, 2014

This new NASA/ESA Hubble Space Telescope image shows the galaxy IC 335 in front of a backdrop of distant galaxies. IC 335 is part of a galaxy group containing three other galaxies, and located in the Fornax ...

Image: Multicoloured view of supernova remnant

Dec 22, 2014

Most celestial events unfold over thousands of years or more, making it impossible to follow their evolution on human timescales. Supernovas are notable exceptions, the powerful stellar explosions that make ...

Ultra-luminous X-ray sources in starburst galaxies

Dec 22, 2014

Ultra-luminous X-ray sources (ULXs) are point sources in the sky that are so bright in X-rays that each emits more radiation than a million suns emit at all wavelengths. ULXs are rare. Most galaxies (including ...

When a bright light fades

Dec 22, 2014

Astronomer Charles Telesco is primarily interested in the creation of planets and stars. So, when the University of Florida's giant telescope was pointed at a star undergoing a magnificent and explosive death, ...

User comments : 1

Adjust slider to filter visible comments by rank

Display comments: newest first

fetzpahs
not rated yet Jun 23, 2014
The two-step mechanism is plausible. Higher energies open up many more reaction pathways, forming less energetically-favored isomers. But subsequence reactions go with thermodynamic stability and make for condensed structures.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.