Study of galaxy Segue 1 suggests it may be a fossil from the early universe

Apr 09, 2014 by Bob Yirka report
The portion of sky in which astronomers found the Segue 1 dwarf galaxy. Credit: Marla Geha/W.M. Keck Observatory.

(Phys.org) —A trio of space researchers studying the galaxy Segue 1 has found that its red giant stars are made mostly of hydrogen and helium, with very few heavy elements, suggesting the galaxy stopped evolving not long after its formation. In their paper uploaded to the preprint sever arXiv (and soon to be published in Astrophysical Journal) the team describes observation data they've obtained regarding the galaxy and why what they've found might mean Segue 1 is the oldest observable galaxy in the night sky.

Scientists have known about Segue 1 for some time—it's both close to us (just 75,000 light years away) and very small, with just few hundred . In this new effort, Anna Frebel with MIT, Joshua Simon with Carnegie Mellon University and Evan Kirby with the University of California studied the makeup of red giants in Segue 1 and found they are made up mostly of hydrogen and helium. This implies that the stars came about due to the explosions of massive stars—prior research has shown that it's smaller star explosions that result in forming heavy with metals (because the smaller stars create the heavier elements). Prior research has also shown that higher mass stars tend to blow up at a much younger age than low mass stars. Also when stars explode in general, they release material that winds up being used in new star formation. As the process repeats, more stars with heavy metals are created. But not Segue 1—for some reason the evolution process simply stopped, leaving the galaxy in very nearly the same condition it was shortly after forming. Why this happened is a mystery, though there is one theory—it's based on reionization.

Reionization theory suggests that shortly after the universe was born, ionized gasses began to cool allowing the formation of atoms and eventually stars. Those stars eventually blew up releasing radiation that served as fuel for more reionization. New stars cannot form from ionized gasses, of course, so if certain parts of space had stars that caused a lot of reionization, the creation of new stars would have been impossible—the evolution of such a galaxy would simply stop.

Thus far, Segue 1 is the only such galaxy to have been found, but if the reionization theory is correct, it's likely there are many more, researchers just can't see them because they are too far away.

Explore further: Ellipticals and spirals comprise two different populations of "green" galaxies

More information: Segue 1: An Unevolved Fossil Galaxy from the Early Universe, arXiv:1403.6116 [astro-ph.GA] arxiv.org/abs/1403.6116

Abstract
We present Magellan/MIKE and Keck/HIRES high-resolution spectra of six red giant stars in the dwarf galaxy Segue 1. Including one additional Segue 1 star observed by Norris et al. (2010), high-resolution spectra have now been obtained for every red giant in Segue 1. Remarkably, three of these seven stars have metallicities below [Fe/H] = -3.5, suggesting that Segue 1 is the least chemically evolved galaxy known. We confirm previous medium-resolution analyses demonstrating that Segue 1 stars span a metallicity range of more than 2 dex, from [Fe/H] = -1.4 to [Fe/H] = -3.8. All of the Segue 1 stars are alpha-enhanced, with [alpha/Fe] ~ 0.5. High alpha-element abundances are typical for metal-poor stars, but in every previously studied galaxy [alpha/Fe] declines for more metal-rich stars, which is typically interpreted as iron enrichment from supernova Ia. The absence of this signature in Segue 1 indicates that it was enriched exclusively by massive stars. Other light element abundance ratios in Segue 1, including carbon-enhancement in the three most metal-poor stars, closely resemble those of metal-poor halo stars. Finally, we classify the most metal-rich star as a CH star given its large overabundances of carbon and s-process elements. The other six stars show remarkably low neutron-capture element abundances of [Sr/H] < -4.9 and [Ba/H] < -4.2, which are comparable to the lowest levels ever detected in halo stars. This suggests minimal neutron-capture enrichment, perhaps limited to a single r-process or weak s-process synthesizing event. Altogether, the chemical abundances of Segue 1 indicate no substantial chemical evolution, supporting the idea that it may be a surviving first galaxy that experienced only one burst of star formation.

via NatureNews

add to favorites email to friend print save as pdf

Related Stories

New tool for galactic archaeology

Apr 07, 2014

(Phys.org) —Reconstructing the history of our Galaxy has just become a whole lot easier, thanks to a team of international astronomers led by Dr Luca Casagrande from the Research School of Astronomy and ...

Image: The NGC 5194 spiral galaxy

Jan 28, 2014

The Whirlpool Galaxy, also known as M51 or NGC 5194, is one of the most spectacular examples of a spiral galaxy. With two spiral arms curling into one another in a billowing swirl, this galaxy hosts over ...

Not all who wander are lost

Jan 09, 2012

(PhysOrg.com) -- Some stars have orbits that take them to interesting places, and they have interesting stories to tell about how they were formed. For more than a decade, the Sloan Digital Sky Survey (SDSS) ...

Recommended for you

Kepler proves it can still find planets

Dec 18, 2014

To paraphrase Mark Twain, the report of the Kepler spacecraft's death was greatly exaggerated. Despite a malfunction that ended its primary mission in May 2013, Kepler is still alive and working. The evidence ...

User comments : 12

Adjust slider to filter visible comments by rank

Display comments: newest first

katesisco
1 / 5 (1) Apr 09, 2014
Well. because it so close we see this oddity.
Methuselah stars are near by also. There is the Magellenic clouds that seem strangely reminiscent of a fractured large galaxy. Our missing energy/mass could be just magnetic energy bound up in globular clusters.
Might I suggest the loss of a compressive magnetic field would leave the stars without any impulse to change, either by implosion or explosion.
Tuxford
1.4 / 5 (5) Apr 09, 2014
There is a more likely theory: Mostly only the massive giants are visible at this distance. And the massive giants have grown from within in relative isolation. The bigger they get, the faster they grow, spawning new hydrogen from deep within their cores where fertile conditions exist. Hence with the accelerated growth of hydrogen within, the concentration of heavy metals within the star is reduced.

No need to postulate remnants of the big bang nonsense. Just acknowledge the obvious. Not that hard really. Or cling to to the fantasy. Disneyland is fun for children. It is time astronomers became intellectual adults.
Fisty_McBeefpunch
5 / 5 (8) Apr 09, 2014
"...spawning new hydrogen from deep within their cores where fertile conditions exist."

"Hence with the accelerated growth of hydrogen within, the concentration of heavy metals within the star is reduced."

"It is time astronomers became intellectual adults."

Could you please explain your new hypothesis of nucleosynthesis?
Tuxford
1 / 5 (5) Apr 09, 2014
You must be new, otherwise you would ignore this, and go back to fantasizing, like most here. These concepts are a direct consequence of this model, however inconvenient to fanciful minds.

http://starburstf...mulator/

http://starburstf...l_G.html
Fisty_McBeefpunch
5 / 5 (8) Apr 09, 2014
Ok. I read it. When I got up to this, "These entities are too small to ever be individually observed by physicists measuring instruments, but they are hypothesized to diffuse freely through space and to spontaneously react with one another." I realized why you are ignored. Thanks though.
Tuxford
1 / 5 (4) Apr 09, 2014
Most don't have a clue about the implications of systems dynamics. Carry on.
Accounts
5 / 5 (1) Apr 12, 2014
@tuxford

There is a more likely theory: Mostly only the massive giants are visible at this distance. And the massive giants have grown from within in relative isolation. The bigger they get, the faster they grow, spawning new hydrogen from deep within their cores where fertile conditions exist. Hence with the accelerated growth of hydrogen within, the concentration of heavy metals within the star is reduced.

No need to postulate remnants of the big bang nonsense. Just acknowledge the obvious. Not that hard really. Or cling to to the fantasy. Disneyland is fun for children. It is time astronomers became intellectual adults.


And what standing do you have to make such a huge accusation? And why doesn't anyone seem to agree with your "obvious" (and laughable) statement?
Tuxford
1 / 5 (4) Apr 12, 2014
Standing??? Always looking for a higher authority to confirm your view, like most here? Let us bow in front of the alter of science. Afterall, it has led us to the almighty Huge Bang Fantasy. I prefer rather to think logically about the situation, rather than indulge in unseen dimensions, expanding nothingness, and mythical 'god' particles.

Without some background in systems dynamics, you just can't possibly get it. It is a rather recent science, grounded in engineering principles.

In any case, with the preponderance of recent observations continuing to stack up in favor of this 'laughable' theory, despite the fanciful protestations, I remain confident about who will have the last laugh. But please, enjoy the fantasy. Be happy.

JohnGee
5 / 5 (1) Apr 12, 2014
Huge Bang... you do realize the term "big bang" was coined by Fred Hoyle to poke fun at the idea? You were beaten to the punch a long time ago, by the last respected astrophysicist not to accept the "primeval atom" theory. There's a reason he was the last.
Accounts
5 / 5 (1) Apr 12, 2014
@Tuxford.

Standing??? Always looking for a higher authority to confirm your view, like most here? Let us bow in front of the alter of science. Afterall, it has led us to the almighty Huge Bang Fantasy. I prefer rather to think logically about the situation, rather than indulge in unseen dimensions, expanding nothingness, and mythical 'god' particles.

--------------------------

Like I thought. No standing whatsoever. None. Just you, your mouth, your thumb and turning blue.

- Greg

Read more at: http://phys.org/n...html#jCp
GSwift7
5 / 5 (2) Apr 15, 2014
Most don't have a clue about the implications of systems dynamics


But even young children have a fairly good BS-ometer from about the age of six. It improves with vocabulary, but the basic skill is there early, for MOST people.
GSwift7
5 / 5 (1) Apr 15, 2014
Standing??? Always looking for a higher authority to confirm your view, like most here?


At least an educated and credible authority.

Most cranks and crackpots who complain about the BB theory, dark matter/energy, etc. fail to realize that the bulk of serious physics work is being done with the express purpose of replacing those ideas with something more specific and descriptive, which is consistent in a broader context. We WILL replace our current theories of QFT and GR with 'something else' eventually. However, that replacement will happen as a result of testing and observation. The fact that present theory isn't perfect does not validate hair-brained nonsense that you pulled out of your ear.

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.