Astronomers find a universal correlation that could unify the study of star formation

October 25, 2018, Astronomy & Astrophysics
Credit: Astronomy & Astrophysics

Star formation is one of the most important research fields in astrophysics. This process, in which gravitational instabilities cause the collapse of gas to form more compact structures and finally stars, encompasses a broad range of physical scales. These include star-forming galaxies on the large scale, individual young stars with envelopes and circumstellar disks on the smaller scale, and intermediate scales that include giant molecular clouds and protostellar cores.

In the last decades of the 20th century, astronomers established a well-known relation for the intermediate-large scales called the Kennicutt-Schmidt Law. More recent versions of this law establish that the so-called (SFR), which measures the pace at which stars are formed in a galaxy or a molecular cloud, is proportional to the amount of dense gas mass present in that galaxy or molecular cloud. The previous relation confirms that the star formation rate measured in galaxies is related to the mass of gas that is transformed into stars, which are located in the that those galaxies host, given that it is here where the material that will form stars is found.

On the other hand, at the small scale of star formation, it is also known that there is a correlation between the mass accretion rate, which measures the pace at which circumstellar gas falls on to a star in formation, and the mass of the protoplanetary disks that surround . It is only recently that this second correlation has been confirmed observationally, at least in the star forming regions where both parameters have been measured accurately.

In a work recently published in the Astronomy & Astrophysics journal and led by researcher Ignacio Mendigutía, the authors have compiled the available data for the SFRs and the dense gas masses of a sample of galaxies and a representative group of molecular within the Milky Way, and the available data for the accretion rates and disk masses of a representative sample of young stars also in our galaxy.

What they have found is surprising. A unique correlation emerges between the data compiled, encompassing no less than 16 orders of magnitude and relating very different physical scales: individual, young stars, molecular clouds, and galaxies. Mendigutía says, "We have found a correlation between the pace at which gas transforms into stars and the dense gas mass directly associated to star formation. This is probably one of the widest empirical relations ever observed, given that it encompasses an enormous range of scales: from sizes of hundreds of thousands of light-years in galaxies, to sizes comparable to our solar system in stars."

The researchers suggest a "bottom-up" hypothesis to explain this discovery and propose future observations to test it. According to their hypothesis, the correlation in galaxies and molecular clouds would result from the smaller-scale relation between the individual stars hosted by them. "After the initial surprise, the fact that what we observe in individual stars correlates with whole is what one would expect if measurements on both scales are correct," concludes Mendigutía.

Explore further: How disc galaxies work

More information: I. Mendigutía et al. A global correlation linking young stars, clouds, and galaxies, Astronomy & Astrophysics (2018). DOI: 10.1051/0004-6361/201833166

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2 / 5 (8) Oct 25, 2018
"Mendigutía says, "We have found a correlation between the pace at which gas transforms into stars and the dense gas mass directly associated to star formation. This is probably one of the widest empirical relations ever observed, given that it encompasses an enormous range of scales: from sizes of hundreds of thousands of light-years in galaxies, to sizes comparable to our solar system in stars."

This latter part (to sizes comparable to our solar system in stars.") reminds me of what granville mentioned in another physorg forum wrt (paraphrasing) a "solar system-sized region full of trillions of Stars that lies close to the alleged Black Hole at the centre of Sagitarrius A (Sgr A*).
Perhaps granville's hypothesis is also correct.

2.6 / 5 (5) Oct 25, 2018
I think that those conditions, even though they are not 'stellar' energy conditions, but getting down to planet, moons and rings, even moons of moons, and asteroid belts with their own regions disturbed by the stellar wind and charging particles, whether to help accrete or repel, as they may.

And then drop a few orders again for ionization and energy release at photon level, quarks and gluons seem to have their own versions in hadronic and leptonic versions of same.

Scale up again to galaxy clusters and then super-clusters, where perhaps star growth slows, but the black holes appear to Feed and Feed. And this is likely even carried further towards both ends so that one resembles the other at various, pertinent scales.

In the sky we may be looking at what a quark-gluon plasma liquid looks like from the inside of the big bang in the first seconds or so. Frozen in time, seemingly, to us, until we look at their atomic fractal iterations and see the speed T correlation difference.
3.2 / 5 (9) Oct 25, 2018
Perhaps granville's hypothesis is also correct.

Two chances of that - none, and f*** all.
2.6 / 5 (5) Oct 26, 2018
Hmmm....and what force is scale-independent? Hint: not gravity.
3 / 5 (4) Oct 26, 2018
What is not to like? (Translation: *16* oom? Wow!)

Incidentally, this hierarchical process is in tension with the early giant protoclusters found [ ], but both are still very much LCDM compliant. Clearly we don't know all the details of star, galaxy, cluster formation yet.

Hmmm....and what force is scale-independent?

Relevance? The processes are largely results of GR (gravity) whether the scale is the universe, its filament maturation, clusters, galaxies, clouds and stars. And it does not matter whether or not the interactions are scale independent, what matters is that the processes are. C.f. how black body radiation is the same for the universe (cosmic background radiation) down to the smallest pore in a solid body (lab scale), despite that QED is not scale independent [ https://en.wikipe...dynamics ].

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