Detailed age map shows how Milky Way came together

Detailed age map shows how Milky Way came together
Credit: University of Notre Dame

Using colors to identify the approximate ages of more than 130,000 stars in the Milky Way's halo, Notre Dame astronomers have produced the clearest picture yet of how the galaxy formed more than 13.5 billion years ago.

Astrophysicist Daniela Carollo, research assistant professor in the Department of Physics at the University of Notre Dame, and Timothy Beers, Notre Dame Chair of Astrophysics, along with research assistant professor Vinicius Placco and their colleagues published their findings in Nature Physics, including a chronographic (age) map that supports a hierarchical model of . That model, developed by theoreticians over the past few decades, suggests that the Milky Way formed by merging and accretion of small mini-halos containing stars and gas, and that the oldest of the Milky Way's stars are at the center of the galaxy and younger stars and galaxies merged with the Milky Way, drawn in by gravity over billions of years.

See the "Age structure of the Milky Way's halo" animation at www3.nd.edu/~vplacco/map/index.html

"We haven't previously known much about the age of the most ancient component of the Milky Way, which is the Halo System," Carollo says. "But now we have demonstrated conclusively for the first time that ancient stars are in the center of the galaxy and the younger stars are found at longer distances. This is another piece of information that we can use to understand the assembly process of the galaxy, and how galaxies in general formed."

Using data from the Sloan Digital Sky Survey, in which Notre Dame is a partner, the scientists identified more than 130,000 blue horizontal-branch stars, which burn helium in their cores, and exhibit different colors based on their ages. They are the only type of star whose age can be estimated by color alone. The technique they employed is one that Beers helped develop about 25 years ago when he was still a postdoctoral fellow.

The mapped stars show a clear hierarchy, with the oldest stars near the center of the galaxy, and younger stars further away.

"The colors, when the stars are at that stage of their evolution, are directly related to the amount of time that star has been alive, so we can estimate the age," Beers says. "Once you have a map, then you can determine which stars came in first and the ages of those portions of the galaxy. We can now actually visualize how our galaxy was built up and inspect the stellar debris from some of the other small galaxies being destroyed by their interaction with ours during its assembly."

Carollo explains that initial gas clouds containing primordial material, such as hydrogen and helium, formed the first stars. Clouds with various masses and gas content behaved differently: the smaller clouds formed one or two generation of stars (older objects) and then merged with other clouds and ended in the center of the galaxy pulled in by gravity, while larger mass clouds formed multiple generation of (younger objects) before they merged.

Still larger galaxies, such as the Milky Way, grew as their gravity pulled in and forced mergers with these smaller galaxies.

Today, it is only possible to use these techniques in our own galaxy and in the dwarf satellite galaxies that surround the Milky Way. But, the James Webb Space Telescope, set to be launched in 2018, is expected to gather much more data from distant , including the first glows from the Big Bang. Using the aging method that Beers' Galactic Archaeology group at Notre Dame employed, that data can fill in pieces of the puzzle on our own galaxy's formation, as well as questions about how the universe came into being.


Explore further

Astrophysicists produce the first age map of the halo of the Milky Way

More information: D. Carollo et al, The age structure of the Milky Way's halo, Nature Physics (2016). DOI: 10.1038/nphys3874 , http://arxiv.org/abs/1607.08628
Journal information: Nature Physics

Citation: Detailed age map shows how Milky Way came together (2016, September 6) retrieved 15 September 2019 from https://phys.org/news/2016-09-age-milky.html
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Sep 06, 2016
uh oh they used the dreaded 'm' word "merger." I mean... the data fit the prediction of the model, but I'm sure that won't stop random internet buffoons from telling us how people who've never spent a moment of their lives learning science have more credibility than people who've done it for years. (or how outdated scientific ideas are better or whatever the buffoonery du jour is.)

Sep 06, 2016
"The colors, when the stars are at that stage of their evolution, are directly related to the amount of time that star has been alive, so we can estimate the age,"

A very big assumption, based on lesser assumptions, all beginning with a guess.
Science?

Sep 06, 2016
"But now we have demonstrated conclusively for the first time that ancient stars are in the center of the galaxy and the younger stars are found at longer distances.

More merger mania on full display.

Right then, explain the counter-evidence. 'Their discovery shows that stars can, in fact, form very close to the Milky Way's central black hole.'
http://phys.org/n...tic.html

'Another puzzling characteristic of the GC, the astronomer's abbreviation for the galactic center, is the fact that it contains the three most massive clusters of young stars in the entire galaxy.'
http://phys.org/n...lky.html

'Hubble Space Telescope has found a rare class of oddball stars called blue stragglers in the hub of our Milky Way...'
http://phys.org/n...ars.html

Anyway, stragglers are not necessarily so young, just low metallicity due to internal rapid growth.

RNP
Sep 07, 2016
@Tuxford

"But now we have demonstrated conclusively for the first time that ancient stars are in the center of the galaxy and the younger stars are found at longer distances.

More merger mania on full display.

Right then, explain the counter-evidence. ...............................


Can you explain how ANY of the articles you mention are "counter-evidence" for the importance of mergers in the formation of galaxies? I ask because none of the authors of the papers concerned would agree with you. So, tell us, what do *you* know that they do not?

Sep 07, 2016
So, I've tried the ignore philosophy before, and... I see its merit in theory. But in practice, I'd rather any other reader coming into the thread know that there will inevitably be trolls along a certain line of thought, and that their views don't represent anything resembling 'science.' Yes, in theory, the votes on posts could be used to filter comments, but they don't always work that way either, since you can find some posts get inverted voting as more cranks dominate one conversation.

Sep 07, 2016
You're arguing with a bratty 15 year old girl. Blame phys.org for not doing their job and exposing us to risks like that
..........and you're 5'-6" tall and weigh 275 lbs living in an armchair & gaze in mirrors wishing 80% of you was missing.

What makes you any better when you don't address the subject matter & sling personal innuendo around? You Asstro-physicists are all alike, taking after the zany personality traits of godfather Zwicky & all the tired theories that Astrologer ever came up with.

RNP
Sep 07, 2016
@Benni
And how is your post addressing the issue?

Sep 07, 2016
We're all just feeding a troll at this point. Benni won't go away until the mods do something about him/her, and even then, he/she will likely create a proxy account to continue ranting into a comment section on a layman-oriented science news site for... reasons?

@Benni, nobody is listening to you anymore. You post nothing constructive. You just rant about Zwicky, gloat about being able to solve differential equations, and denigrate anyone who doesn't conform to your viewpoint... which is what, exactly? It's gotten lost in all the vitriol you post.

Is it that all the all of astronomy (and various other fields of science) is/are a farce, and you've got (or know of) some alternative (set of) theory/theories that actually explain actual observations that nobody else can understand because they're not earth-shatteringly brilliant like you?

I would ask what possible reward exists for your behavior, but I've ceased to care what your answer would be!

Sep 07, 2016
But....you are responding to his post....so clearly at least one confused person is, or did you forget to count yourself....understandable.

Read more at: http://phys.org/n...html#jCp


Hearing (seeing) pointless insults and ranting and listening (reading and absorbing) the pointless insults and ranting are two very different things.

Your fervent responses and condescension towards those that voice displeasure at what fits every definition of a troll makes me wonder if you are in fact the same person. My ignore list grows...

Sep 09, 2016
Carollo explains that initial gas clouds containing primordial material, such as hydrogen and helium, formed the first stars

Perhaps someone can please tell me just how did these first stars form out of these clouds of gas all by themselves? How exactly did they get past that enigmatic stage of self-ignition in spite of all the physical odds stacked against such an occurrence, no matter how dense the cloud gets?

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