The properties of pre-stellar cores

January 18, 2016
A false-color infrared image of a young, star-forming dust cloud with several embedded cores (identified in red). A new infrared study of 3218 cores in various stages of development has enabled astronomers to categorize the temperatures, densities, and evolutionary characters of young stellar nurseries. Credit: NASA/Spitzer and P. Myers

Stars like the Sun begin their lives as cold, dense cores of dust and gas that collapse under the influence of gravity until nuclear fusion is ignited. These cores contain hundreds to thousands of solar-masses of material and have gas densities about a thousand times greater than typical interstellar regions (the typical value is about one molecule per cubic centimeter). How the collapse process occurs in these embryos in poorly understood, from the number of stars that form to the factors that determine their ultimate masses, as well as the detailed timescale for stellar birth. Material, for example, might simply fall freely to the center of the core, but in most realistic scenarios the infall is inhibited by pressure from warm gas, turbulent motions, magnetic fields, or some combination of them.

Astronomers are actively studying these issues by observing young stars in the process of being born. The in these natal cores (or clumps), however, makes them opaque in the optical, thus requiring observations at other wavelengths, in particular infrared, submillimeter, and radio. In the early stages of star formation, an embryonic star heats the surrounding dust cloud to temperatures between about ten and thirty degrees kelvin before stellar winds and radiation blow the material away and expose the newborn star. CfA astronomers Andres Guzman and Howard Smith, together with their colleagues, have completed an analysis of 3246 star-forming cores, the largest sample ever done. The cold cores themselves were discovered with the APEX submillimeter-wavelength sky survey and then observed in sixteen submillimeter spectral lines; the spectral information enabled the astronomers to determine the distance to each core as well as to probe its chemistry and internal gas motions. The new paper combines these results with far-infrared measurements taken by Herschel Space Observatory surveys. The Herschel data allow the scientists to calculate the dust density, mass, and temperature of each core; the large dataset then permits useful statistical comparisons between cores with varyious parameters.

Sources in the sample fall generically into four categories: quiescent clumps, which have the coldest temperatures (16.8K) and the least infrared emission, protostellar clumps, which are sources with the youngest identifiable stellar objects, ionized hydrogen regions, which are cores within which the stars have ionized some of the surrounding gas, and "photo-dissociation" cores, the warmest of the set, which have dust temperatures around 28K, are slightly more evolved and brighter than the ionized hydrogen cores. Although the groups overlap in their properties, the large sample enables the scientists to conclude that, on average, in the quiescent clumps the dust temperature increases towards the outer regions, whereas the temperatures in protostellar and ionized hydrogen cores increase towards the inner region, consistent with the idea that they are being internally heated. The latter also tend to have dust densities that increase more steeply than the quiescent cores. This study has also identified a population of particularly cold and infrared-dark objects that are probably still in the stages of contraction, or else for some reason have had their star formation aborted. The new paper and its catalog are just the beginning: now that the dust in all these cores has been well characterized, astronomers can associate chemistry with dust temperature, for example, and study subgroups that might represent different stellar masses in gestation.

Explore further: Hot cores in dark clouds

More information: Far-Infrared Dust Temperatures and Column Densities of the MALT90 Molecular Clump Sample. arxiv.org/abs/1511.00762

Related Stories

Hot cores in dark clouds

December 6, 2011

(PhysOrg.com) -- The earliest stages in the life of a star are among the most mysterious. This is primarily because stars form inside dark clouds of material that block optical light, and because they form relatively quickly, ...

Stellar embryos

January 23, 2012

(PhysOrg.com) -- Stars form as gravity coalesces the gas and dust in interstellar clouds until the material produces clumps dense enough to become stars. But precisely how this happens, and whether or not the processes are ...

Astronomers get rare peek at early stage of star formation

March 14, 2012

(PhysOrg.com) -- Using radio and infrared telescopes, astronomers have obtained a first tantalizing look at a crucial early stage in star formation. The new observations promise to help scientists understand the early stages ...

Embryos of stars

February 16, 2015

Stars like the Sun begin their lives as cold, dense cores of dust and gas that gradually collapse under the influence of gravity until nuclear fusion is ignited. Exactly how the critical collapse process occurs in these embryos, ...

The physical properties of dense molecular clouds

June 25, 2015

Small, dense interstellar clouds of gas and dust, containing hundreds to thousands of solar-masses of material, are suspected of being the precursors to stars and stellar clusters. These so-called cores, with gas densities ...

Inferring the star formation rates of galaxies

November 23, 2015

Our Milky Way galaxy produces on average a few new stars every year across the entire system. Massive young stars emit large amounts of ultraviolet radiation which heats the local dust, and so the star formation process results ...

Recommended for you

First stars formed even later than previously thought

August 31, 2016

ESA's Planck satellite has revealed that the first stars in the Universe started forming later than previous observations of the Cosmic Microwave Background indicated. This new analysis also shows that these stars were the ...

Dawn sets course for higher orbit

August 31, 2016

After studying Ceres for more than eight months from its low-altitude science orbit, NASA's Dawn spacecraft will move higher up for different views of the dwarf planet.

Galaxy cluster discovered at record-breaking distance

August 31, 2016

A new record for the most distant galaxy cluster has been set using NASA's Chandra X-ray Observatory and other telescopes. This galaxy cluster may have been caught right after birth, a brief, but important stage of evolution ...

The rise and fall of galaxy formation

August 30, 2016

An international team of astronomers, including Carnegie's Eric Persson, has charted the rise and fall of galaxies over 90 percent of cosmic history. Their work, which includes some of the most sensitive astronomical measurements ...

10 comments

Adjust slider to filter visible comments by rank

Display comments: newest first

plasmasrevenge
2.3 / 5 (15) Jan 18, 2016
Although we are led to believe that this is an open-ended inquiry, the very first sentence starts with the confining assumption that it is gravity which instantiates the process ...

"... and gas that collapse under the influence of gravity until nuclear fusion is ignited ..."

Right away, we are unable to draw any analogies to the terrestrial phenomenon of ball lightning, which might also explain for us why we see so many rogue high-velocity stars roaming around.

And when the subject of ionization comes up, it is presented as a secondary effect ...

"... ionized hydrogen regions, which are cores within which the stars have ionized some of the surrounding gas ..."

But, this is obviously taking the expected conclusion for granted, because there is no way to validate (and not any observable attempt here) that the ionization began right here rather than simply being drawn in by electromagnetic forces.
plasmasrevenge
2.3 / 5 (15) Jan 18, 2016
Also, notice no mention in the article of the most perplexing observations announced for the Herschel mission, at http://sci.esa.in...lky-way/ ...

(1) No mention of the filamentation which precedes star formation, or that stars form along the filaments all at once!

(2) No mention that these filaments are observed to draw matter from the surrounding space.

(3) No mention that these filaments branch, much like lightning, and exhibit some level of self-similarity.

And nothing at all that we've learned from observing laboratory plasmas over the last century appears relevant to this author, even as numerous astrophysical and plasma textbooks today point out in the intro that it's 99% of what we see w/ telescopes.

Is it really true that the weakest force can do everything they assume here? Why try so hard to ignore the electric force, in light of these observations?
wduckss
1 / 5 (10) Jan 18, 2016
3,246 stars for another one the wrong hypothesis, instead of presenting the results.
Where in the "vacuum" force to produce a collapse? Compressive forces are the same in all directions, gravity creates terribly slowly new bodies.
".. Until nuclear fusion is ignited." Where is radiation? They ate the aliens? That is why our magma and lava horrible the radioactive?
Osiris1
1 / 5 (4) Jan 18, 2016
If the pre-stellar ignition core contained the mass of thousands of stellar cores, then it would go directly to the black hole end game. Long before the pre-stellar core got to that size, gravitational forces would stimulate fusion, probable at the sub solar mass stage. Else why is our Sun a star and not a dead rogue planet awaiting black hole suicide.
jonesdave
3.9 / 5 (7) Jan 18, 2016
@Plasma,
Why should real scientists do the work on a woo proposal? The data is available (including a total lack of evidence for the required currents in these filaments), so why isn't the EU resident genius on star formation writing his paper up as we speak?
There have been plenty of papers on the observation and nature of these filaments:
http://arxiv.org/abs/1312.6232
And plenty more here: http://sci.esa.in...aid_2=16

Ask those authors why they haven't considered ball lightning, or whatever it is you are so miffed about.
I could do it on your behalf, if you'd prefer, and then publish the replies here.
NiteSkyGerl
3.5 / 5 (8) Jan 19, 2016
What a load of cranks.

Bite me.
jljenkins
3.7 / 5 (6) Jan 19, 2016
Osiris1 1 /5 (2) 19 hours ago
If the pre-stellar ignition core contained the mass of thousands of stellar cores, then it would go directly to the black hole end game.


Classic conspiracy idiot. No appreciation of scale, an inability to conceptualize veridical models, and an absolute belief in any casual arm-chair image that crosses what passes for a mind.

We're talking about 1,000 molecules per cubic centimetre. The heat and solar winds generated in the main collapse easily blow the cloud apart/away.

Maybe spend more time reading and less time with stupid self-aggrandizing posts?
jonesdave
4.2 / 5 (5) Jan 19, 2016
Osiris1 1 /5 (2) 19 hours ago
If the pre-stellar ignition core contained the mass of thousands of stellar cores, then it would go directly to the black hole end game.


Classic conspiracy idiot. No appreciation of scale, an inability to conceptualize veridical models, and an absolute belief in any casual arm-chair image that crosses what passes for a mind.

We're talking about 1,000 molecules per cubic centimetre. The heat and solar winds generated in the main collapse easily blow the cloud apart/away.

Maybe spend more time reading and less time with stupid self-aggrandizing posts?


Trust me, some of these people are not very good at science. They do ignorance for a passtime. You'll get used to it.
Frosted Flake
5 / 5 (1) Jan 21, 2016
I'm impressed astronomers are observing stars before they light.
SHREEKANT
1 / 5 (1) Jan 26, 2016
"Stars like the Sun begin their lives as cold, dense cores of dust and gas that collapse under the influence of gravity until nuclear fusion is ignited." 

2nd OPINION:

Why & how dense core formed? What is the initial thing that unite? What is the reason of pulling force [as per present science – gravity] that act on initial building materials? Why nuclear fusion is ignited?

I am agree that formation of STARS begin their lives as cold, dense core of dust & gas.

But it is true for primary stars not for our sun because our sun is now secondary star.

http://swarajgrou...res.html

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.