A giant stellar void in the Milky Way

August 1, 2016
An artist's illustration of the Milky Way, the galaxy we live in, with the locations of the newly discovered Cepheid stars marked by the yellow points. The previously known objects, located around the sun (marked by a red cross), are indicated by small white dots. The central green circle around the core of the galaxy marks the location of the 'Cepheid desert.' Credit: University of Tokyo

A major revision is required in our understanding of our Milky Way Galaxy according to an international team led by Prof Noriyuki Matsunaga of the University of Tokyo. The Japanese, South African and Italian astronomers find that there is a huge region around the centre of our own Galaxy, which is devoid of young stars. The team publish their work in a paper in Monthly Notices of the Royal Astronomical Society.

The Milky Way is a containing many billions of stars with our Sun about 26,000 from its centre. Measuring the distribution of these stars is crucial to our understanding of how our Galaxy formed and evolved. Pulsating stars called Cepheids are ideal for this. They are much younger (between 10 and 300 million years old) than our Sun (4.6 billion years old) and they pulsate in brightness in a regular cycle. The length of this cycle is related to the luminosity of the Cepheid, so if astronomers monitor them they can establish how bright the star really is, compare it with what we see from Earth, and work out its distance.

Despite this, finding Cepheids in the inner Milky Way is difficult, as the Galaxy is full of interstellar dust which blocks out light and hides many stars from view. Matsunaga's team compensated for this, with an analysis of near-infrared observations made with a Japanese-South African telescope located at Sutherland, South Africa. To their surprise they found hardly any Cepheids in a huge region stretching for thousands of light years from the core of the Galaxy.

Noriyuki Matsunaga explains: "We already found some while ago that there are Cepheids in the central heart of our Milky Way (in a region about 150 light years in radius). Now we find that outside this there is a huge Cepheid desert extending out to 8000 light years from the centre."

An artist's impression of the implied distribution of young stars, represented here by Cepheids shown as blue stars, plotted on the background of a drawing of the Milky Way. With the exception of a small clump in the Galactic center, the central 8,000 light years appear to have very few Cepheids, and hence very few young stars. Credit: The University of Tokyo

This suggests that a large part of our Galaxy, called the Extreme Inner Disk, has no . Co-author Michael Feast notes: "Our conclusions are contrary to other recent work, but in line with the work of radio astronomers who see no new being born in this desert."

Another author, Giuseppe Bono, points out: "The current results indicate that there has been no significant star formation in this large region over hundreds of millions years. The movement and the chemical composition of the new Cepheids are helping us to better understand the formation and evolution of the Milky Way."

Cepheids have more typically been used to measure the distances of objects in the distant Universe, and the new work is an example instead of the same technique revealing the structure of our own Milky Way.

Explore further: Astronomers uncover hidden stellar birthplace

More information: Noriyuki Matsunaga et al. A lack of classical Cepheids in the inner part of the Galactic disk, Monthly Notices of the Royal Astronomical Society (2016). DOI: 10.1093/mnras/stw1548 , http://arxiv.org/abs/1606.07943

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32 comments

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Ultron
1 / 5 (6) Aug 02, 2016
Amazing discovery, one of confirmations I needed.
katesisco
1.4 / 5 (9) Aug 02, 2016
Well, if the imaginary bh are mazed light and a surplus creates an ejection, one might well expect to see gas clouds like Smith's Cloud boomeranging back into the galaxy. After all, astronomers have found that bh are the same size and place as far back as our telescopes can peer.
Somehow I suspect this issue will acquire the label of 'gravity waves.'
katesisco
1.7 / 5 (6) Aug 02, 2016
The reference to the science supporting the statement that bh are the same size at the beginning of the universe as now is in Extreme Cosmos, by Bryan Gaensler, PhD.
epoxy
Aug 02, 2016
This comment has been removed by a moderator.
jonesdave
4.2 / 5 (10) Aug 02, 2016
Well, if the imaginary bh ................


Determine the orbital parameters of a star around Sagittarius A*. From that, determine the mass of the object that it is orbiting. Suggest what that (unseen) mass may be. Report back. Show your working.
(copying other people's work, who have already done this, is allowable).
Phys1
4 / 5 (8) Aug 02, 2016
@epoxy
Any references? If you are right this is additional proof for DM.
jonesdave
4 / 5 (8) Aug 02, 2016
The reference to the science supporting the statement that bh are the same size at the beginning of the universe as now is in Extreme Cosmos, by Bryan Gaensler, PhD.


I'm sure as hell not buying a book; a peer reviewed paper would be better, please.
Da Schneib
4.2 / 5 (10) Aug 02, 2016
One's immediate impression is that the black hole and its effects have shut down star formation in this void, and the first question is how it has done so. Recent findings that hot hydrogen emitted from the regions surrounding active galactic nuclei in other galaxies inhibits star formation seem to give a reason for this. It's speculation at this point, but we should get a really close look at this when the JWST starts observing the center of our galaxy in a few years, and more powerful and sensitive orbital X-ray telescopes come on-line to supplement the JWST's data in another spectral range so we can see both hot gas in X-rays and stars in infrared.
IMP-9
5 / 5 (6) Aug 02, 2016
The reference to the science supporting the statement that bh are the same size at the beginning of the universe as now is in Extreme Cosmos, by Bryan Gaensler, PhD.


Doesn't matter who you're citing, it's still wrong. That simply cannot be determined yet. The highest redshift known quasar is the z=7 Mortlock quasar. Even then the universe was 750 million years old. But in that case we have one quasar at redshift 7, we don't see the population only the most extreme value. You cannot determine from this single quasar that the mass function of black holes in unchanged even to redshift 7, much less the rest of the history of the universe. Just going by the most extreme value we know of SMBHs 10 times more massive than the Mortlock QSO. You're looking at extremely biased values, you can't conclude anything without looking to lower luminosities at high redshift.
JongDan
2.3 / 5 (3) Aug 02, 2016
Well, if the imaginary bh ................


Determine the orbital parameters of a star around Sagittarius A*. From that, determine the mass of the object that it is orbiting. Suggest what that (unseen) mass may be. Report back. Show your working.
(copying other people's work, who have already done this, is allowable).

Alternately, if you believe the attraction is electromagnetic in nature, calculate the charge instead of the mass. Then you can calculate the pressure required to keep those two charges from simply exploding into space by repulsive forces by using radius estimates. You can use the highest reasonable estimates btw.
epoxy
Aug 02, 2016
This comment has been removed by a moderator.
antialias_physorg
3.9 / 5 (7) Aug 02, 2016
One's immediate impression is that the black hole and its effects have shut down star formation in this void

Being centerd on Saggitarius A* it might give an indication how long the BH was dormant and when the last activity occured. Switch from low to high activity should coincide with a shock front at which new stars form. Might be worth looking for such a shock front outside the galactic disc. If one is found at the same distance as the region of "no new stars" then that could be an interesting clue.
jonesdave
4.2 / 5 (10) Aug 02, 2016
Well, if the imaginary bh ................


Determine the orbital parameters of a star around Sagittarius A*. From that, determine the mass of the object that it is orbiting. Suggest what that (unseen) mass may be. Report back. Show your working.
(copying other people's work, who have already done this, is allowable).

Alternately, if you believe the attraction is electromagnetic in nature, calculate the charge instead of the mass. Then you can calculate the pressure required to keep those two charges from simply exploding into space by repulsive forces by using radius estimates. You can use the highest reasonable estimates btw.


And the evidence for something that can supply an attractive force equivalent to ~ 4 million solar masses is? Failing that, what is the theory of something that could supply such a force? Is it falsifiable? What should we expect to see? Where is it written up? Who wrote it?
Phys1
3.9 / 5 (7) Aug 02, 2016
There is absolutely no connection with the current subject. What does a 1 ly scale cusp have to do with an 8000 ly void?
"The influence radius of the supermassive black hole at the Galactic Center is about 2–3 parsecs (pc), and a Bahcall–Wolf cusp if present would extend outward to a distance of about 0.5 pc from the supermassive black hole. "
Tuxford
1.8 / 5 (10) Aug 02, 2016
"We already found some while ago that there are Cepheids in the central heart of our Milky Way (in a region about 150 light years in radius). Now we find that outside this there is a huge Cepheid desert extending out to 8000 light years from the centre."

Again, LaViolette's model offers a potential explanation (which immediately comes to mind):
1) Stars are largely moving outward from the core where many are born from new matter periodically ejected from the core.
2) Near the denser matter region near the core, stars grow most rapidly, frequently becoming unstable variables.
3) As they reach a less dense region, growth rates abate, becoming more stable (void).
4) As they reach the outer regions, they have slowly grown larger still, becoming more unstable again.

Hate the model. Sure. But it fits, once again. What does you favorite fantasy model offer instead, besides more confusion?

http://phys.org/n...ays.html
rderkis
3 / 5 (3) Aug 02, 2016
Wow, this is the first article I have seen, where the comments are to the point and logical, with nobody using the words stupid, dumb, ignorant etc. :-)
But I have faith in people and the fact that it will degrees into name calling.
Scroofinator
1 / 5 (2) Aug 02, 2016
You shut your dumb mouth rderkis, your ignoramusly stupid comment is stupid.

Lol, feel better now?

In all seriousness though, I believe this ties to the way that galaxies form. The most logical theory I've heard is that galaxies are formed from giant molecular clouds, and when they reach what is called jean's instability, the point at which gravity is so great it collapses (there are other factors as well), the cloud goes nova from the inside out. At the center is the SMBH, and the surrounding area would have had much of the matter pushed out from the nova.
Scroofinator
1 / 5 (1) Aug 02, 2016
I also don't find it implausible that in the violence of the explosion that stars could be formed, which would be the these older stars we observe. Outside the void the nova isn't strong enough, so the idea of a more classic star nursery makes sense.
vidyunmaya
1 / 5 (4) Aug 03, 2016
Sub: astronomy to catch-up with Cosmology Vedas interlinks
Galactic centre phenomena.
Astronomers seem to be unaware of my illustrations outlined in my book-I set 9000 Light years near milky-way in steps- that need horizontal integration to Vertical mode integration.
Cosmic consciousness to Cosmology revision-2000- book available at LULU.
I displayed my illustrations during COSPAR 2013.
Plasma regulated Electromagnetic Phenomena in magnetic Field environment- Galaxy Digest helps to bridge the gap-Cosmology Vedas interlinks-15 books available.
TimLong2001
not rated yet Aug 03, 2016
The last gammaray burst may have transported particles in the region farther from the center of the galaxy. These "Seyfert plumes" have decayed into the spiral arms. The central black hole, Sagittarius A*, may have gobbled up the close-in material, or is the result of it?
Scroofinator
1 / 5 (1) Aug 04, 2016
The central black hole, Sagittarius A*, may have gobbled up the close-in material, or is the result of it?

I'm not a fan of the idea that SMBHs get that size by consuming matter. First, there's no way to test the theory. Second, if stellar mass BHs are formed by the collapse of a star, why wouldn't SMBHs form in a similar manner, only with a much more massive gas cloud?
ElectricBoobVerses
Aug 04, 2016
This comment has been removed by a moderator.
Scroofinator
1.8 / 5 (5) Aug 04, 2016
@Scruffy How do measurements of gas motion near the galactic center fail to directly provide data about that?

Well Booby given how we can't even properly predict the motion of a simple gas cloud that orbited SagA*, I'd say that it fails pretty hard to predict how a black hole would actually form that big.
http://earthsky.o...ys-heart
Captain Stumpy
3.7 / 5 (6) Aug 04, 2016
Well Booby given how we can't even properly predict the motion of a simple gas cloud that orbited SagA*
@scroof
wait... what?

so, according to you, complexity is equivalent to failure?

we also can't accurately predict the weather 3 months in the future...
but does that mean we can't predict 3 days out or that we can't measure the atmospheric movement, etc?
(we're running AVG. 90% accuracy on that one here in my area... don't know about yours)

no, it doesn't

It just means that there is a complexity issue that that highly complex interactions mixed with large multi-part simulations is hard to do

accuracy is also determined by error bars, measurement devices, time/timing, application, consistency and a lot more

ElectricBoobVerses
Aug 04, 2016
This comment has been removed by a moderator.
Scroofinator
2 / 5 (4) Aug 04, 2016
so, according to you, complexity is equivalent to failure?

Man you come up with some dumb stuff. It's a failure because their model failed, not because of complexity, but because of a lack of understanding.

They have all the data of the event and still can't figure out why they were wrong. Even if they consider the more "complex" scenario of two stars engulfed in the gas cloud (which we would be able to observe btw), they still can't make the model work.

Stop trying to make excuses. Complexity... bah

jeffensley
not rated yet Aug 04, 2016
Could a single (or more likely two geometrically balanced) BH's (or other "dark" bodies) orbiting the central one create this effect? It's as if there is a gravitational sweeper of sorts orbiting that region. Small enough to not destroy already formed stars but big enough to rob new ones of material...
Captain Stumpy
3 / 5 (2) Aug 04, 2016
Could folks report @vidyunmaya each time he posts? It's pure spam, no different than the work-from-home types
@electricboobverses
it wont do any good... i know of at least 10 people who do it regularly, along with certain other posters

.

because of a lack of understanding.
@scroof
really?
where?
show the evidence
They have all the data of the event
and you know this for a fact?
really?

again: evidence?

perhaps you should take your own advice: Stop trying to make excuses

there is evidence, and there is belief in something
you believe you are right about something but have no evidence
the scientific method, however, follows the evidence and, eventually, will figure out the problem because (yep, you guessed it) it follows the evidence

you're arguing the "god of the gaps" argument - because we don't know now we won't know later
Scroofinator
2.3 / 5 (3) Aug 04, 2016
show the evidence

They failed to predict the orbit of g2 (and still can't), they fail to understand why there is this void we are commenting on.

again: evidence?

Just google G2 SagA* and you'll find a plethora of articles stating how many observatories and satellites were trained on the event. If you honestly don't think there is sufficient data then this discussion is over.
Enthusiastic Fool
5 / 5 (3) Aug 05, 2016
@Tux

Again, LaViolette's woo offers a potential embarassment:
1) Stars are largely moving outward from the core where many are born from new matter periodically ejected from the core.
2) Near the denser matter region near the core, stars grow most rapidly, frequently becoming unstable variables.
3) As they reach a less dense region, growth rates abate, becoming more stable (void).
4) As they reach the outer regions, they have slowly grown larger still, becoming more unstable again.

Your "model" lacks a mechanism for why old stars bunch up in the middle while you claim new stars move out radially from the Sgr A*. This would imply the greatest density of young stars would be at the center and drop off proportionally with the root of the distance. This is not what the article says at all. If the void was completely empty of all stars then periodic outbursts from a "core star" might explain the void but that's not the case.
Enthusiastic Fool
5 / 5 (3) Aug 05, 2016
@Tux cont.

Furthermore, if all the stars in the center were moving out radially then stars on the far side of the core from us would be redshifted and stars on the close side would be blue shifted. Where's the paper to support that idea?

Cephids as rapidly growing unstable stars which age then stabilize due to lack of growth? before becoming young unstable stars again when they've migrated out far enough? The ideas you present here are so half cocked I can't even come up with a coherent way to refute them. Your stars change age, composition, and behavior through unexplained mechanisms which makes it seem like you are taking the evidence here and making shit up on the fly. Your "model" allows you to make "predictions" after the fact and it doesn't even fit the evidence or logic.
Tuxford
1 / 5 (2) Aug 05, 2016
Your "model" allows you to make "predictions" after the fact and it doesn't even fit the evidence or logic.

It is not my model. Just fitting the observation into the model. Clearly you don't understand the model. So you call it names. (That is preferrable to acknowledging a lack of understanding. Just too much for any self-respecting intellectual egomaniac to bear!)

The article ASSUMES variables to indicate young stars. I was talking only about variables, and how their population might change with distance from the core, according to LaViolette's model. He might disagree. Ask him. I said nothing about age of stars, just their tendency to grow over time.

Please try to argue with correct facts. Thanks.

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