NASA Spacecraft Discovers the Universe is Less Crowded Than We Thought (cnet.com) 37
An anonymous reader shares a report: While we might think of space as a vast sea of blackness, all we have to do is look up at night to see that it's punctuated by countless stars, galaxies and even a few planets visible to the naked eye. Scientists recently used data from NASA's New Horizons mission out beyond Pluto to measure just how dark the cosmic background really is. What they found has implications for what we thought we knew about the makeup of the entire universe. In short, space is so dark there can't be as many galaxies out there, adding their faint glow to the backdrop, as astronomers have previously estimated.
"It's an important number to know -- how many galaxies are there?" Marc Postman of the Space Telescope Science Institute said in a statement Tuesday. "We simply don't see the light from 2 trillion galaxies." That was the earlier estimate derived from Hubble Space Telescope observations, but a new study forthcoming in the Astrophysical Journal and co-authored by Postman suggests the total number of galaxies in the universe is probably in the hundreds of billions rather than the trillions. Interestingly, this is closer to an even earlier figure guessing there were around 200 billion galaxies. That was based on Hubble data from the 1990s.
"It's an important number to know -- how many galaxies are there?" Marc Postman of the Space Telescope Science Institute said in a statement Tuesday. "We simply don't see the light from 2 trillion galaxies." That was the earlier estimate derived from Hubble Space Telescope observations, but a new study forthcoming in the Astrophysical Journal and co-authored by Postman suggests the total number of galaxies in the universe is probably in the hundreds of billions rather than the trillions. Interestingly, this is closer to an even earlier figure guessing there were around 200 billion galaxies. That was based on Hubble data from the 1990s.
So, does this add to the missing mass? (Score:5, Interesting)
If there are fewer galaxies and we already know what they weigh, does that mean we need even more "dark matter"?
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imo, they just cut back on processing power for the simulation because our astronomical theories have been making the bill too high
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No. Dark matter is needed to explain observations of gravitational effects within galaxies and galaxy clusters. It doesn't matter a whole lot how many galaxies and clusters are out there in addition to the ones that can be observed. We assume the laws of physics are the same across the universe.
Just wait. Give it some time (Score:1)
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unlikely, the universe is too damn big. We couldn't fill the volume out to pluto's furthest 50 AU trek with garbage, there isn't enough planetary material.
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I have confidence in humanity's ability to mine the asteroid fields and turn them into single-use disposable products. I just wish we had the willpower to not do it.
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wouldn't be a problem, consider all the "garbage" a supernova makes... that just condensed into our solar system 5 billion years ago. Enough plastic garbage will just condense and undergo fusion with a hydrogen and carbon/nitrogen cycle like our sun.
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I have confidence in humanity's ability to mine the asteroid fields and turn them into single-use disposable products. I just wish we had the willpower to not do it.
That doesn't refute the GP's point--turn all the asteroids into trash, and you have... exactly as much mass worth of trash as you do asteroids, which on the scale of the solar system are quite sparse.
Science Fiction stories (Score:3)
This has always concerned me about Science Fiction stories that have vast galactic civilizations: is there enough matter to build the massive structures that some story lines envisage?
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How big are we talking about, there was one story by famous author (40+ years ago) about protagonists using time dilation to go billions of years into the future and seeing a civilization assembling filaments of galaxies to thwart the plans of some opposing one, all before the universe ended.
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Re:Science Fiction stories (Score:5, Informative)
As for the spheres, such as the ones in Roger McBride Allen's Ring of Charon series, again, there should be sufficient amount of matter in our own solar system to create a sphere around the Sun.
Considering some of the other solar systems we have detected with multiple planets the size of Jupiter or Saturn, there seems to be enough matter to create these structures so long as you don't go overboard.
Re:Science Fiction stories (Score:4)
One AU is 1.5e11 meters.
The area of a Dyson Sphere at one AU would be 4*PI*R^2 = 2.8e23.
The mass of Jupiter is 1.9e27 kg.
So that is about 6700 kg per square meter. That should be plenty.
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Also it's not (necessarily) supposed to be a sphere all around it but rather you can hang up multiple collectors around the star. Don't have to build it all at once.
A bit of overreach? (Score:4, Insightful)
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They have a better estimate than before. That's what progress looks like.
There are many explanations for this data (Score:5, Interesting)
One hypothesis is that there is more dust between galaxies than estimated that is absorbing the light they measured. That dust could be one part of the "dark matter" puzzle. Another hypothesis is that dark matter consists of particles that simply cannot exist (and therefore not detectable here) in the presence of galactic gravitational fields but absorbs light like the matter we can observe.
Its exciting information that coupled with something like the Hubble Deep Field image for the entire sky would give us useful data.
My intuition is that this is the case, but certainly not the complete answer for the dark matter puzzle or full evidence useful for estimating the number of galaxies.
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Dark matter is the place holder for the gravitational effects we observe within galactic clusters and acting upon galaxies.
Distant galaxies and clusters don't come into the calculations, so the number of them wouldn't change anything.
Total universal mass is calculated from the "cosmic background radiation."
It's a confusingly similar name, but new horizons is mapping the "cosmic optical background"
The cosmic background radiation isn't effected by dust at all.
That energy was produced at a time in the universe
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>The cosmic background radiation isn't effected by dust at all
Although I hadn't mentioned the cosmic microwave background, since it is redshifted higher frequency radiation, it must have traversed through some space after dust could have formed. Also, I don't understand why dust couldn't affect electromagnetic radiation including microwaves - it certainly does afaik and I used to wo
Interesting data. (Score:2)
It is interesting data, but there's so many questions in my silly idiot brain about what it means that I have to think there's some astrophysicists literally doing cartwheels trying to come up with explanations.
Some quick, off the cuff, hobby-level interest in astrophysics ideas:
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The previous estimate was made using the Hubble Deep Field image, where they pointed Hubble at one of the emptiest spots they could see and left it there for a month collecting as many photons as they could. The image, while stunningly beautiful, surprised astronomers by the stunning number of galaxies. It's certainly possible that there just happens to coincidentally be more galaxies in this view than there would be in any other random direction. On the other hand it's also possible that the issue lies
Confused (Score:3)
I'm kind of confused by the article on hubblesite. It starts off with the quote about there not being enough light to account for two trillion of galaxies and so there must be fewer galaxies than thought, but by the end of the article, it's talking about there being more light than can be accounted for, and possibly more galaxies than previously thought. This bit;
So, what could be the source of this leftover glow? It’s possible that an abundance of dwarf galaxies in the relatively nearby universe lie just beyond detectability. Or the diffuse halos of stars that surround galaxies might be brighter than expected. There might be a population of rogue, intergalactic stars spread throughout the cosmos. Perhaps most intriguing, there may be many more faint, distant galaxies than theories suggest.
I'm assuming I misread or misunderstood something, anyone want to enlighten me?
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We can't know as we can't observe it as we don't live in space!
- AAAAH!!
- You see. It's true.
YouTube: S.P.O.C.K. - In Space No One Can Hear You scream. [youtube.com]
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As best I can interpret it, they identified the light from galaxies and different light from an unknown source. The first was lower than expected but the second was higher than expected (or perhaps not even expected).
Since NH's cameras can see in different wavelengths, perhaps they used this info as a rough spectrograph to separate galaxy light from non-galaxy light.
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Hi, enlightenment is my specialization. The next text is according to my skimming of the article [hubblesite.org]. First of all, the overall detected light has to get removed the light from sort-of local sources, that is anything within this galaxy. Notice that is is quite involved, mostly due to dispersion of light on dust, etc.
After that, you remove light from other galaxies. You start with removing light of bright galaxies, then you continue with a removal of light of dimmer galaxies. At some point the ambient light arou
You don't see the light! (Score:1)
That is different from them not being there.
Baby don't see mommy either, when the hands are in-between.
So... did we do anything to check if maybe there is more obstruction than we thought?
Gravitational anti-lensing by dark something?
Two problems. (Score:1)
Aren't we supposed to live in a (large?) cluster of galaxies within the or the second biggest void we know of? I assume that affect what you think of the rest of the universe if you don't take that into account because if you look nearby in that case it would seem denser than what it may be in general then again look a bit further and it wouldn't seem so.
Also this is just the observable universe, it's assumed to be like 93 billion light years across right? The problem is that we can't see stuff which would
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Where did I say it affected the age?
I've never said whatever you interpreted it and are replying to.
What I am saying is that we can't see light which haven't reached us and the 93 billion light years across isn't the size of the universe it's the size of THE OBSERVABLE universe.
And that's very relevant because it seem weird to talk about 200 billion galaxies in a universe you don't know how large it is. I assume they mean 200 billion galaxies IN THE OBSERVABLE UNIVERSE. As the universe is expanding at dista
Miss Universe (Score:1)
There's a Miss Philadelphia contest, there's a Miss Pennsylvania contest, a Miss America contest and even a Miss Universe contest....
I wonder why the town of Big Beaver, Pennsylvania has never had a beauty contest?
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Why is Miss Universe always from earth?
Re:Miss Universe (Score:4, Funny)
We only publicize the Earth results. Our candidate for Miss Universe can't travel to the main competition, and the hosting organization refuses to host the main competition on Earth, so in compromise, allow Earth's citizens to believe they have the right to refer to her as Miss Universe.
Re:Miss Universe (Score:4, Funny)
I bought a universal remote today (Score:3, Funny)
- and I'm rather dissatisfied...
It does not control the Universe. Not even remotely.