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Archive for July 25, 2013

ALMA Sheds Light On Mystery Of Missing Massive Galaxies


Three-dimensional view of ALMA observations. Credit: ALMA (ESO / NAOJ / NRAO) / Erik Rosolowsky

Three-dimensional view of ALMA observations. Credit: ALMA (ESO / NAOJ / NRAO) / Erik Rosolowsky

Galaxies — systems like our own Milky Way that contain up to hundreds of billions of stars — are the basic building blocks of the cosmos. One ambitious goal of contemporary astronomy is to understand the ways in which galaxies grow and evolve, a key question being star formation: what determines the number of new stars that will form in a galaxy?

The Sculptor Galaxy, also known as NGC 253, is a spiral galaxy located in the southern constellation of Sculptor. At a distance of around 11.5 million light-years from our Solar System it is one of our closer intergalactic neighbours, and one of the closest starburst galaxies visible from the southern hemisphere. Using the Atacama Large Millimeter/submillimeter Array (ALMA) astronomers have discovered billowing columns of cold, dense gas fleeing from the centre of the galactic disc.

“With ALMA’s superb resolution and sensitivity, we can clearly see for the first time massive concentrations of cold gas being jettisoned by expanding shells of intense pressure created by young stars,” said Alberto Bolatto of the University of Maryland, USA lead author of the paper. “The amount of gas we measure gives us very good evidence that some growing galaxies spew out more gas than they take in. We may be seeing a present-day example of a very common occurrence in the early Universe.”

Full Story: http://www.eso.org/public/news/eso1334/
Also: http://www.nrao.edu/pr/2013/starburst-bust/
Also: http://www.mpia.de/Public/menu_q2.php?Aktuelles/PR/2013/PR_2013_06/PR_2013_06_en.html

Starburst Wind Keeps Galaxies ‘Thin’


Unlike humans, galaxies don’t have an obesity problem. In fact there are far fewer galaxies at the most massive end of the galactic scale than expected and scientists have long sought to explain why. A new, UMD-led study published in the journal Nature suggests that one answer lies in a kind of feast and fast sequence through which large galaxies can keep their mass down.

Galaxies become more massive by ‘consuming’ vast clouds of gas and turning them into new stars. The new study shows in unprecedented detail how a burst of star formation in a galaxy can blow most of the remaining star-building gas out to the edge of the galaxy, resulting in a long period of starvation during which few new stars are produced.

“For the first time, we can clearly see massive concentrations of cold molecular gas being jettisoned by expanding shells of intense pressure created by young stars,” says lead author Alberto Bolatto of the University of Maryland. “The amount of gas we measure gives us very convincing evidence that some growing galaxies blow out more gas than they take in, slowing star formation down to a crawl.”

Full Story: http://umdrightnow.umd.edu/news/starburst-wind-keeps-galaxies-%E2%80%98thin%E2%80%99

Solar System’s Youth Gives Clues To Planet Search


Disk isotopes modeling results. Image courtesy of Alan Boss

Disk isotopes modeling results. Image courtesy of Alan Boss

Comets and meteorites contain clues to our solar system’s earliest days. But some of the findings are puzzle pieces that don’t seem to fit well together. A new set of theoretical models from Carnegie’s Alan Boss shows how an outburst event in the Sun’s formative years could explain some of this disparate evidence. His work could have implications for the hunt for habitable planets outside of our solar system. It is published by The Astrophysical Journal.

One way to study the solar system’s formative period is to look for samples of small crystalline particles that were formed at high temperatures but now exist in icy comets. Another is to analyze the traces of isotopes—versions of elements with the same number of protons, but a different number of neutrons—found in primitive meteorites. These isotopes decay and turn into different, so-called daughter, elements. The initial abundances of these isotopes tell researchers where the isotopes may have come from, and can give clues as to how they traveled around the early solar system.

Stars are surrounded by disks of rotating gas during the early stages of their lives. Observations of young stars that still have these gas disks demonstrate that sun-like stars undergo periodic bursts, lasting about 100 years each, during which mass is transferred from the disk to the young star.

Full Story: https://carnegiescience.edu/news/solar_system%E2%80%99s_youth_gives_clues_planet_search

Ancient Snowfall Likely Carved Martian Valleys


Credit: Image from NASA

Credit: Image from NASA

Valley networks branching across the Martian surface leave little doubt that water once flowed on the Red Planet. But where that ancient water came from — whether it bubbled up from underground or fell as rain or snow — is still debated by scientists. A new study by researchers at Brown University puts a new check mark in the precipitation column.

The study finds that water-carved valleys at four different locations on Mars appear to have been caused by runoff from orographic precipitation — snow or rain that falls when moist prevailing winds are pushed upward by mountain ridges. The new findings are the most detailed evidence yet of an orographic effect on ancient Mars and could shed new light on the planet’s early climate and atmosphere.

Full Story: http://news.brown.edu/pressreleases/2013/07/snow