What's slowing the universe's star formation rate?

According to a new study, magnetic fields may explain why the universe's star formation rate is so much slower than those predicted by cosmic models.

According to the Standard Model of the universe, the cosmos should have reached peak star formation several billion years ago. All the stars in the universe should have already formed and star-making materials should be scarce.

Of course, that's not what astronomers see when they look through their telescopes. The universe is still making stars some 13.8 billion years after the Big Bang.

But what accounts for the star formation slowdown?

The slowing of star formation is known as quenching, and scientists have considered several mechanisms as explanations for the phenomenon. The latest analysis suggests cosmic rays and magnetic fields explain quenching.

When astronomers modeled the spiral galaxy NGC 1097, they found magnetic forces in the galaxy's center put forces on gas clouds that prevent matter from collapsing and forming stars.

Scientists combined visible and the near-infrared renderings of NGC 1097 captured by the Hubble Space Telescope and Very Large Array with radio observations from the Very Large Array and the Submillimeter Array. The data revealed the effects of turbulence, stellar radiation and magnetic fields on star formation rates.

Their analysis showed an inverse relationship between the magnetic field and star formation within a molecular cloud -- the larger the magnetic field, the slower the rate of star formation.

"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," astronomer Fatemeh Tabatabaei said in a news release. "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."

Scientists have been studying NGC 1097 for some time, but this is the first time astronomers considered the effects of its magnetic fields on star formation.

Researchers published their work in a new paper published this week in the journal Nature Astronomy.

The revelation has implications for astronomers' understanding of the star formation process, specifically among galactic centers. If large clouds with large magnetic fields limit star formation, stars can only begin to form when molecular clouds become fragmented. As a result, galactic centers are more likely to yield low-mass stars -- a prediction that's borne out by recent astronomical surveys.

Why is massive star formation quenched in galaxy centers?
La Palma, Canary Islands (SPX) Nov 30, 2017
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 ... read more

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