Subscribe to our free daily newsletters
. 24/7 Space News .




Subscribe to our free daily newsletters



STELLAR CHEMISTRY
Why is massive star formation quenched in galaxy centers?
by Staff Writers
La Palma, Canary Islands (SPX) Nov 30, 2017


Magnetic fields control the collapse of the molecular clouds in the nuclear ring of the galaxy NGC 1097. As a result, formation of massive stars is suppressed in zones of strong magnetic field (contours).

The current cosmological model to explain our universe, the "Big Bang" model, aims to describe all the phenomena we observe, which includes the galaxies and their evolution from earliest times to the present day. One of the major problems faced by the standard form of this model is that it has predicted a star formation rate -speed at which new stars are born- which is far too big.

All the star forming material in galaxies should have been turned into stars when the universe had only a fraction of its present age, 13,8 billion years. However, over half the galaxies we see, mainly the spirals, are very actively forming stars right now.

This discrepancy between theoretical prediction and observation has forced to look much more closely at processes which can slow down the rate of star formation during the lifetimes of galaxies, collectively known as "star formation quenching". Without quenching the standard Big Bang model fails to predict the universe as we know it.

There have been a number of mechanisms proposed for quenching, for example "feedback" from supernovae or active galactic nuclei which breaks up the star forming clouds and reduces the star formation rate, but the measurement and verification of yet other possible processes is of great importance. One of this mechanisms has just been published in Nature Astronomy led by the Instituto de Astrofisica de Canarias (IAC) researcher, Fatemeh Tabatabaei. The study points to magnetic fields and cosmic rays as responsible for massive stars forming slowly.

Studying in great detail the star formation parameters of the central region of the spiral galaxy NGC 1097, they concluded that the presence of a relatively large magnetic field is acting as a quenching agent, due to a magnetic field that exerts a pressure within a gas cloud which can slow down or stop its tendency to collapse and form stars. But the results have gone further, because researchers have shown that this mechanism is in fact working around the center of NGC 1097.

They combined observations in the visible and the near infrared from the Hubble Space Telescope with radio observations from the Very Large Array and the Submillimeter Array to explore the effect of the turbulence, stellar radiation, and magnetic field on massive star formation in the galaxy's nuclear ring.

This ring contains a number of clearly distinct zones where stars are forming inside huge molecular cloud complexes. The principal result they obtained was an inverse relation between the star formation rate in a given molecular cloud and the magnetic field within it: the larger the field the slower is the star formation rate.

"To do this, we made a specific separation of the magnetic field and its energy from other sources of energy in the interstellar medium, which are the thermal energy, and the general non-thermal but non-magnetic energy" explains Fatemeh Tabatabaei.

"Only by combining the high quality observations at very different wavelengths could we do this and when we separated these energy sources the effect of the magnetic field was surprisingly clear". Almudena Prieto, another of the authors adds in the same sense: "although I have been working on the central zone of NGC 1097 at optical and infrared wavelengths for some time, only when we took into account the magnetic field could we realize its relevance in decreasing the rate at which stars are formed".

This result has several interesting consequences and throws light on several types of interrelated astrophysical puzzles. Firstly, as the magnetic field does not allow very large molecular clouds to collapse and form stars, star formation can occur only after the clouds break up into smaller clouds. This means that this region will have a higher fraction of low-mass stars than in other zones of the galaxy.

The tendency of very massive galaxies to contain a high fraction of low-mass stars at their centers is a recent discovery, and is still in some ways controversial, but is reinforced by the work reported here. Also of interest is the fact that the presence of supermassive black holes in the centers of galaxies does tend to enhance the nuclear magnetic field, so that this quenching mechanism should be most effective in the bulges of galaxies.

Research Report: "Discovery of massive star formation quenching by non-thermal effects in the center of NGC 1097"

STELLAR CHEMISTRY
Astronomers reveal nearby stars that are among the oldest in our galaxy
Atlanta GA (SPX) Nov 23, 2017
Astronomers have discovered some of the oldest stars in our Milky Way galaxy by determining their locations and velocities, according to a study led by scientists at Georgia State University. Just like humans, stars have a life span: birth, youth, adulthood, senior and death. This study focused on old or "senior citizen" stars, also known as cool subdwarfs, that are much older and cooler i ... read more

Related Links
Instituto de Astrofisica de Canarias
Stellar Chemistry, The Universe And All Within It


Thanks for being here;
We need your help. The SpaceDaily news network continues to grow but revenues have never been harder to maintain.

With the rise of Ad Blockers, and Facebook - our traditional revenue sources via quality network advertising continues to decline. And unlike so many other news sites, we don't have a paywall - with those annoying usernames and passwords.

Our news coverage takes time and effort to publish 365 days a year.

If you find our news sites informative and useful then please consider becoming a regular supporter or for now make a one off contribution.

SpaceDaily Contributor
$5 Billed Once


credit card or paypal
SpaceDaily Monthly Supporter
$5 Billed Monthly


paypal only

Comment using your Disqus, Facebook, Google or Twitter login.

Share this article via these popular social media networks
del.icio.usdel.icio.us DiggDigg RedditReddit GoogleGoogle

STELLAR CHEMISTRY
Building for a future in space: An interview with Dava Newman and Gui Trotti

Space Farms: 'Mark Watney in The Martian Was Right to Add Poop to the Soil'

New motion sensors major step towards cheaper wearable technology

Does the Outer Space Treaty at 50 need a rethink

STELLAR CHEMISTRY
ISRO eyes one rocket launch a month in 2018

Russia to build launch pad for super heavy-lift carrier by 2028

Mechanisms are critical to all space vehicles

Russia loses contact with satellite after launch from new spaceport

STELLAR CHEMISTRY
Earthworms can reproduce in Mars-like soil

Opportunity Greets Winter Solstice

NASA builds its next Mars rover mission

Scientists developed a new sensor for future missions to the Moon and Mars

STELLAR CHEMISTRY
Nation 'leads world' in remote sensing technology

China plans for nuclear-powered interplanetary capacity by 2040

China plans first sea based launch by 2018

China's reusable spacecraft to be launched in 2020

STELLAR CHEMISTRY
Going green to the Red Planet

Orbital ATK purchase by Northrop Grumman approved by shareholders

UK space launch program receives funding boost from Westminster

Need to double number of operational satellites: ISRO chief

STELLAR CHEMISTRY
Quantum optics allows us to abandon expensive lasers in spectroscopy

Spin current from heat: New material increases efficiency

New catalyst controls activation of a carbon-hydrogen bond

Math gets real in strong, lightweight structures

STELLAR CHEMISTRY
Scientists identify key factors that help microbes thrive in harsh environments

Exoplanet Has Smothering Stratosphere Without Water

Scientists study Earth's earliest life forms in Nevada hot spring

Traces of life on nearest exoplanets may be hidden in equatorial trap

STELLAR CHEMISTRY
Pluto's hydrocarbon haze keeps dwarf planet colder than expected

Jupiter's Stunning Southern Hemisphere

Watching Jupiter's multiple pulsating X-ray Aurora

Help Nickname New Horizons' Next Flyby Target




Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News






The content herein, unless otherwise known to be public domain, are Copyright 1995-2017 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. All articles labeled "by Staff Writers" include reports supplied to Space Media Network by industry news wires, PR agencies, corporate press officers and the like. Such articles are individually curated and edited by Space Media Network staff on the basis of the report's information value to our industry and professional readership. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement