This very detailed enhanced-color image from ESO’s Very Large Telescope shows the dramatic effects of very young stars on the dust and gas from which they were born in the star-forming region NGC 6729.

Credit: ESO/Sergey Stepanenko

Stars and their formation remain key to understanding everything we know about solar systems like ours. But how stars form and ultimately spawn rocky planets on which life can flourish is still not understood with the kind of certainty that one would expect in this age of high-powered computer simulations and space-based telescopes.

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Stars actually get their start in giant molecular clouds of gas and dust, like those found in the nearby Orion Nebula. Roiling forces deep inside these giant clouds cause matter to knot into clumps that eventually collapse under the weight of their own gravity. Not unlike empty buildings undergoing controlled demolitions, as these clumps collapse, their centers begin to heat and differentiate into hot cores and protostars.

Then over timescales of tens of millions of years, these protostars turn into full-blown hydrogen-burners, fusing hydrogen into helium. The remaining gas and dust around these protostars can in theory form planets, asteroids or even comets.

Yet many questions remain, including the following:

Why is the cosmos so predisposed to making low mass M dwarfs? That is, cool red dwarf stars which range in mass from as small as a tenth up to about half the mass of our Sun.

“This influences almost everything in astrophysics, not just the number of potentially habitable planets, but the distribution of heavy elements over space and time in the universe, the supernova rate, and the properties and evolution of galaxies,” Stella Offner, an astronomer at the University of Texas at Austin, told me.

These red dwarf stars make up an estimated 75 percent of stars in the cosmos. But why? One idea which I noted in a recent issue of Astronomy magazine is that the most common stellar mass is somehow correlated with the minimum mass at which nuclear fusion can begin. However, there is no theoretical agreement on this conundrum.

— Why is the formation of stars so inefficient?

The giant clouds that form stars can contain tens of thousands of solar masses of gas, says Offner. But she says observations suggest that less than 5% of this gas actually forms stars.

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That’s partly because these giant star-forming molecular clouds are transient, Sally Dodson-Robinson, an astronomer at the University of Delaware in Newark, told me. These clouds, she says, get dispersed by galactic tides, blown away by winds from the young, intermediate-mass stars they form, and most dramatically get broken up by supernovae.

And as Dodson-Robinson points out, when the universe had nothing except hydrogen, helium, and trace amounts of lithium, there was no easy way to cool down clumps of dense gas enough for gravity to take over and make them collapse. That’s because heavy metals act to absorb a cloud’s heat, enabling it to cool until it becomes gravitationally unstable.

This image from the APEX telescope, of part of the Taurus Molecular Cloud, shows a sinuous filament of cosmic dust more than ten light-years long.

Credit: ESO/APEX (MPIfR/ESO/OSO)/A. Hacar et al./Digitized Sky Survey 2. Acknowledgment: Davide De Martin.

— How does a star’s metallicity content impact the production of habitable planets?

“Planet-forming disks with high concentrations of elements such as silicon, iron, and oxygen have more raw material for planet formation than disks with low metallicity,” said Dodson-Robinson.

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But because the galaxy’s metal content built up as byproducts of supernovae over cosmic time, Dodson-Robinson says that planets that formed early in the galaxy’s history may be silicate-rich and lack the metallic iron-nickel core that is a signature characteristic of our own Earth. She notes that it’s Earth’s liquid outer iron-nickel core that enables our protective geomagnetic field which deflects charged lethal solar wind particles and cosmic rays.

So the universe’s very oldest planets, says Dodson-Robinson, might not be as protected from harmful particles as we are.

— Do we have a better understanding of planet formation than star formation?

Katelyn Allers, an astronomer at Bucknell University in Lewisburg, Pa., says no. We know much more about star formation than we do about planet formation, Allers told me. For one thing, astronomers can study stars as they are forming. For planets, she says, we only have a few examples that might indicate exoplanets in formation. So, she says, we don’t have as much empirical data on planet formation.

“Given the great differences between the planets and moons in our own solar system, it’s difficult to develop a theoretical model that explains all types of planets,” said Dodson-Robinson.

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That’s not to say that stars are simpler than planets, she says, but the mass of a star is incredibly deterministic. In essence, Dodson-Robinson says that a star’s mass controls its luminosity and lifetime.

Yet Offner says we are still missing quite a bit when it comes to understanding star formation.

Even with the fastest supercomputers, Offner says we are not able to follow the scale of an average stellar birth cloud, of some 30 light years in diameter, down to the formation of an individual star. And because gas and dust obscure the earliest stages of star formation on scales of less than a 100 Earth-Sun distances, astronomers also miss such observational details, Offner says. This is a problem for both stellar theory and observations, she says.

Ultimately answering such questions may help us understand what sort of life might start where and around what type of star. We do know that life here on Earth was profoundly affected by our Sun’s peak radiation wavelengths.

“Light with wavelengths between 400 and 700 nanometers travels through earth’s atmosphere very well, so our eyes use that kind of light to see,” said Dodson-Robinson. In contrast, life on a planet orbiting an M dwarf star, she says, would have no need to develop vision in the optical or ultraviolet because red dwarfs don’t put out much optical light.

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By the same token, Dodson-Robinson says that although we haven’t needed to evolve radiation-protective skins, that doesn’t mean it can’t be done.

Many astrobiologists think that habitable zones around orange dwarf stars are still best for the evolution of intelligent life. That’s because, among other things, they are a bit longer lived than our Sun.

“Given that intelligent life has taken pretty much half of our Sun’s lifetime to develop, having a longer lifetime is certainly a plus,” said Allers.

But as Offner points out, we’re here around a G-type star talking about all this. Thus, she argues, stars longer lived than ours aren’t a prerequisite for the evolution of intelligent life.

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(******** )This extremely comprehensive enhanced-color image from ESO’s Huge Telescope reveals the significant results of extremely young stars on the dust and gas from which they were born in the star-forming area NGC 6729.

Credit: ESO/Sergey Stepanenko

Stars and their development stay essential to comprehending whatever we understand about planetary systems like ours. However how stars form and eventually generate rocky worlds on which life can grow is still not comprehended with the sort of certainty that a person would anticipate in this age of high-powered computer system simulations and space-based telescopes.

SHORT ARTICLE CONTINUES AFTER AD

Stars in fact get

their start in huge molecular clouds of gas and dust, like those discovered in the neighboring Orion Nebula. Roiling forces deep inside these huge clouds trigger matter to knot into clumps that ultimately collapse under the weight of their own gravity. Not unlike empty structures going through regulated demolitions, as these clumps collapse, their centers start to heat and distinguish into hot cores and protostars.

Then over timescales of 10s of countless years, these protostars become full-blown hydrogen-burners, merging hydrogen into helium. The staying gas and dust around these protostars can in theory type worlds, asteroids or perhaps comets.

(************ )Yet numerous concerns stay, consisting of the following:

Why is the universes so inclined to making low mass M overshadows? (*************** ) That is, cool red dwarf stars which vary in mass from as little as a tenth as much as about half the mass of our Sun.

“This affects practically whatever in astrophysics, not simply the variety of possibly habitable

worlds, however the circulation of heavy aspects over area and time in deep space, the supernova rate, and the residential or commercial properties and development of galaxies,” Stella Offner, an astronomer at the University of Texas at Austin, informed me.

These red dwarf stars comprise an approximated 75 percent of stars in the universes. However why? One concept which I kept in mind in a current concern of Astronomy publication is that the most typical outstanding mass is in some way associated with the minimum mass at which nuclear blend can start. Nevertheless, there is no theoretical arrangement on this dilemma.

— Why is the development of stars so ineffective?

(************ )The huge clouds that form stars can include 10s of countless

solar masses of gas, states Offner. However she states observations recommend that less than 5% of this gas in fact forms stars (************************ ).

SHORT ARTICLE CONTINUES AFTER AD

That’s partially due to the fact that these huge star-forming molecular clouds are short-term, Sally Dodson-Robinson, an astronomer at the University of Delaware in Newark, informed me. These clouds, she states, get distributed by stellar tides, blown away by winds from the young, intermediate-mass stars they form, and the majority of drastically get separated by supernovae.(********* )

And as Dodson-Robinson explains, when deep space had absolutely nothing other than hydrogen, helium, and trace quantities of lithium, there was no simple method to cool off clumps of thick gas enough for gravity to take control of and make them collapse. That’s due to the fact that heavy metals act to soak up a cloud’s heat, allowing it to cool till it ends up being gravitationally unsteady.

(**** )

(****** )

This image from the PEAK telescope, of

part of the Taurus Molecular Cloud, reveals
a sinuous filament of cosmic dust more than
10 light-years long.

Credit: ESO/APEX( MPIfR/ESO/OSO)/ A. Hacar et al./ Digitized Sky Study 2. Recommendation: Davide De Martin.(***********

)

— How does a star’s metallicity material effect the production of habitable

worlds?

(*********
)

” Planet-forming disks with high concentrations of aspects such as silicon, iron, and oxygen have more basic material for world development than disks with low metallicity,” stated Dodson-Robinson.

(************** )SHORT ARTICLE CONTINUES AFTER AD

However due to the fact that the galaxy’s metal material developed as by-products of supernovae over cosmic time, Dodson-Robinson states that worlds that

formed early in

the galaxy’s history might be silicate-rich and do not have the metal iron-nickel core that is a signature quality of our own Earth. She keeps in mind that it’s Earth’s liquid external iron-nickel core that allows our protective geomagnetic field which deflects charged deadly solar wind particles and cosmic rays. (********* )

So deep space’s extremely earliest worlds, states Dodson-Robinson, may not be as safeguarded from hazardous particles as we are.

— Do we have a much better understanding of world development than star development?

Katelyn Allers, an astronomer at Bucknell University in Lewisburg, Pa., states no. We understand a lot more
about star development than we do about world development, Allers informed me. For something, astronomers can study stars as they

are forming. For worlds, she states, we just have a couple of examples that may suggest exoplanets in development. So, she states, we do not have as much empirical information on world development.

” Offered the terrific distinctions in between the worlds and moons in our own planetary system, it’s hard to establish a theoretical design that describes all kinds of worlds, “stated Dodson-Robinson. (********* )(************* ) SHORT ARTICLE CONTINUES AFTER AD(*************** )

(************ )That’s not to state that stars are easier than worlds, she states, however the mass of a star is exceptionally deterministic.

In essence, Dodson-Robinson states that a star’s mass manages its luminosity and life time.

Yet Offner states we are still missing out on a fair bit when it concerns comprehending star development.

Even with the fastest supercomputers, Offner states we are unable to follow the scale of

a typical outstanding birth cloud, of some30 light years in size, down to the development
of a specific star. And due to the fact that gas and dust obscure the earliest phases of star development on scales of less than a100 Earth-Sun ranges, astronomers likewise miss out on such observational information, Offner states. This is an issue for both outstanding theory and observations, she states.

(************ )Eventually responding to such concerns might assist us comprehend what sort of life may begin where and around what kind of star. We do understand that life here in the world was exceptionally impacted by our Sun’s peak radiation wavelengths.

Light with wavelengths in between400 and700 nanometers takes a trip through earth’s environment effectively, so our eyes utilize that sort of light to see,” stated Dodson-Robinson. On the other hand, life on a world orbiting an M dwarf star, she states, would have no requirement to establish vision in the optical or ultraviolet due to the fact that red overshadows do not put out much optical light.(********* )(************* ) SHORT ARTICLE CONTINUES AFTER AD (*************** )