Astrophysics and Cosmology - Discuss the Universe here

[area51drone]

Here's a really cool photo I just found that shows just how big M31 is compared to the moon (in the sky)..  it's a composite meaning the moon was photographed separately, but it's still incredible how so few people have ever seen Andromeda compared to their obvious knowledge of the moon which is so much smaller, yet far brighter.

http://apod.nasa.gov/apod/ap061228.html

[GeorgieForPresident2216]

Here's a really cool photo I just found that shows just how big M31 is compared to the moon (in the sky)..  it's a composite meaning the moon was photographed separately, but it's still incredible how so few people have ever seen Andromeda compared to their obvious knowledge of the moon which is so much smaller, yet far brighter.

http://apod.nasa.gov/apod/ap061228.html

It's pretty amazing when you see it laid out like that.  I've only ever been able to see it out of the corner of my eye, and only once or twice.

[zeebo]

I'm pretty sure even in my 'scope I've only really seen the bright core of Andromeda they mentioned.  To pick up those wispy arms you need more optical horsepower I think. 

I do remember reading somewhere that it is the farthest object away you can see with the naked eye, which is pretty cool.  And I suspect most people don't realize how much crazier far away it really is. 

The bright star Vega is only 25 lt. yrs. away, while Andromeda is 2.5 million lt. yrs. from us ... 100,000 times farther away.   

[area51drone]

I was shocked how easy it was to see when I got my gen3 night vision.  It really surprised me because the only time I had ever viewed it before was through my telescope.   Obviously we'll never see it so beautiful with our naked eye, but just the fact that it's so enormous and just sitting there slightly too dim for the average person to make out on a dark night, and far too dim for anyone in populated areas to ever see...   it's like a gem sitting plain in the open, just waiting for people to discover it.   Of course with the NV monocular, it's still just a green fuzzy blob, but it's plain as day.

Speaking of the NV, a few weeks ago I accidentally left the cover over the amplifier tube, and put it up to my eye with the unit on.  I was *shocked* that I could still see through the cover.    It is an excellent example of how "empty" matter is, even a 1/8" thick piece of black matte plastic.      All those photons getting through something that you'd never be able to see through with your naked eye.   I had fun testing out other materials to see how opaque they really were.

[zeebo]

I was shocked how easy it was to see when I got my gen3 night vision....

Something to ponder whilst checking out Andromeda, is that the light you're picking up started it's journey to us around the very beginning of the Stone Age:

The Stone Age or Paleolithic Period is the name archaeologists have given to the beginning of archaeology--that part of the earth's history that includes the genus Homo and our immediate ancestor Australopithecus. It began approximately 2.5 million years ago, in Africa, when Australopithecus began making stone tools, and ended about 20,000 years ago, with big-brained and talented modern humans spread all over the world.

[Robert Ghostwolf's Ghost]

Something to ponder whilst checking out Andromeda, is that the light you're picking up started it's journey to us around the very beginning of the Stone Age:

The Stone Age or Paleolithic Period is the name archaeologists have given to the beginning of archaeology--that part of the earth's history that includes the genus Homo and our immediate ancestor Australopithecus. It began approximately 2.5 million years ago, in Africa, when Australopithecus began making stone tools, and ended about 20,000 years ago, with big-brained and talented modern humans spread all over the world.

I've long wondered if any of the stars we see every night went super nova millions of years ago and we just don't know it yet.  It would be cool to look up some night at the same moment the light from the explosion reached us, especially if it was a star in one of the prominent constellations.

[GeorgieForPresident2216]

I've long wondered if any of the stars we see every night went super nova millions of years ago and we just don't know it yet.  It would be cool to look up some night at the same moment the light from the explosion reached us, especially if it was a star in one of the prominent constellations.

Although Andromeda is at 2 1/2 million light years or so, most of the stars you can clearly make out at night are only dozens, or maybe up to a few hundred light years away.  I haven't taken a survey but that seems to be my observation whenever I look them up.  Even then, it is only the largest stars which you can see at that distance so they are prime candidates for supernova, but I think scientists have a pretty good idea which nearby stars are primed to go supernova anytime in the next few tens of thousands of years.  If a distant star even in a nearby satellite galaxy went supernova, it's possible you could see that.

This isn't really my area of interest -- I'm more interested in the physics of the universe than specific stars -- so take my observations for what they're worth  . 

[Robert Ghostwolf's Ghost]

Although Andromeda is at 2 1/2 million light years or so, most of the stars you can clearly make out at night are only dozens, or maybe up to a few hundred light years away.  I haven't taken a survey but that seems to be my observation whenever I look them up.  Even then, it is only the largest stars which you can see at that distance so they are prime candidates for supernova, but I think scientists have a pretty good idea which nearby stars are primed to go supernova anytime in the next few tens of thousands of years.  If a distant star even in a nearby satellite galaxy went supernova, it's possible you could see that.

This isn't really my area of interest -- I'm more interested in the physics of the universe than specific stars -- so take my observations for what they're worth  .

Knowledge of astronomy isn't my super power, so I really don't know how any of that would work.  I'll go along with your observations, because they're undoubtedly worth a lot more than my wild speculations.  I just think it would be cool to look up one night and see one of the stars in the Big Dipper or Orion suddenly flare up to several times its normal size, kind of like the way big rain storms suddenly pop up out of nowhere on a weather radar loop.

[GeorgieForPresident2216]

Knowledge of astronomy isn't my super power, so I really don't know how any of that would work.  I'll go along with your observations, because they're undoubtedly worth a lot more than my wild speculations.  I just think it would be cool to look up one night and see one of the stars in the Big Dipper or Orion suddenly flare up to several times its normal size, kind of like the way big rain storms suddenly pop up out of nowhere on a weather radar loop.

Oh, it would be cool.  Scientists don't get a lot of opportunity to study them.  However, such a close star exploding probably wouldn't be so good for us.  Then again, I'd have to check that out

[Robert Ghostwolf's Ghost]

Oh, it would be cool.  Scientists don't get a lot of opportunity to study them.  However, such a close star exploding probably wouldn't be so good for us.  Then again, I'd have to check that out

Yeah, it's only cool as long as your planet doesn't get scorched to a cinder in the process.  Nobody likes it when that happens.  I'd settle for seeing one that's beyond the danger zone. 

[zeebo]

Although Andromeda is at 2 1/2 million light years or so, most of the stars you can clearly make out at night are only dozens, or maybe up to a few hundred light years away.  I haven't taken a survey but that seems to be my observation whenever I look them up. ...

Yep, here's my go-to list, for easy reference.

http://en.wikipedia.org/wiki/Brightest_stars

Btw I just noticed that Deneb, which just cracks the top 20, is much farther away than most, at ~2600 lt. yrs., meaning it must be a very bright star.  Apparently it's luminosity is around 200,000 times that of our sun.

[zeebo]

...I just think it would be cool to look up one night and see one of the stars in the Big Dipper or Orion suddenly flare up to several times its normal size...

As long as we're not looking down the "gamma ray gunbarrel".   

[area51drone]

Oh, it would be cool.  Scientists don't get a lot of opportunity to study them.  However, such a close star exploding probably wouldn't be so good for us.  Then again, I'd have to check that out

Supposedly more than 100 light years doesn't pose a problem?   I just watched the stuff on super novas and they find like 100-200 of them every year now, by looking at many galaxies night after night.   I think the last one they saw that lit up like a new naked eye star was in the late 80's, and if I remember it was 170k light years away maybe?

[GeorgieForPresident2216]

Supposedly more than 100 light years doesn't pose a problem?   I just watched the stuff on super novas and they find like 100-200 of them every year now, by looking at many galaxies night after night.   I think the last one they saw that lit up like a new naked eye star was in the late 80's, and if I remember it was 170k light years away maybe?

I was thinking about the same one, Supernova 1987A which occurred in the Large Magellanic Cloud -- a satellite galaxy unfortunately only visible in the Southern Hemisphere.  I thought this had been the only visible one (unaided) recorded in modern times but thought I'd better look it up -- sure enough, it appears to be the only one of note, at least, since 1604.  I think some others may have been visible as well but more distant and faint.  Actually I thought 1987A had some sort of twin in '87 or '88, but I guess I was getting mixed up.  I suppose as you say they don't necessarily need them to be naked eye visible to study them.

[wr250]

Supposedly more than 100 light years doesn't pose a problem?   I just watched the stuff on super novas and they find like 100-200 of them every year now, by looking at many galaxies night after night.   I think the last one they saw that lit up like a new naked eye star was in the late 80's, and if I remember it was 170k light years away maybe?

there have been gamma ray bursters from within 10000's of  light years away that produce measurable atmospheric changes.

in addition there is evidence that a gamma ray burster initiated a mass extinction  at least once in the earths past 

[zeebo]

New Horizons, afer eight years and eight months, has passed Neptune's orbit, and is on it's way to Pluto by next summer.

http://science.nasa.gov/science-news/science-at-nasa/2014/25aug_newhorizons/

Don't worry Pluto, you'll have your day!

[attachimg=1]

[Mr. Fidget]

Excerpt: "Scientists think that the universe’s information may be contained in the same way and that the natural “pixel size” of space is roughly 10 trillion trillion times smaller than an atom, a distance that physicists refer to as the Planck scale."

Do we live in a 2-D hologram?

Story: http://www.fnal.gov/pub/presspass/press_releases/2014/2-D-Hologram-20140826.html

Pictures: http://www.fnal.gov/pub/presspass/press_releases/2014/2-D-Hologram-20140826-images.html

mf

[GeorgieForPresident2216]

Excerpt: "Scientists think that the universe’s information may be contained in the same way and that the natural “pixel size” of space is roughly 10 trillion trillion times smaller than an atom, a distance that physicists refer to as the Planck scale."

Do we live in a 2-D hologram?

Story: http://www.fnal.gov/pub/presspass/press_releases/2014/2-D-Hologram-20140826.html

Pictures: http://www.fnal.gov/pub/presspass/press_releases/2014/2-D-Hologram-20140826-images.html

mf

Not a 2-D hologram, but possibly something akin to  stick of RAM filled with memory addresses.

[Agent : Orange]

Hey everyone

Great to see so much lively discussion going on! I wanted to pop my head in and say hi, and let you all know that I exist now in a superposition of states, simultaneously working my ass off and posting on coastgab. Blink and you will find me in one or the other.

Also, all this talk of exploding stars makes me think of one of the most compelling topics, the question of what those explosions leave behind.
In some cases you get one of these: http://www.spacetoday.org/DeepSpace/Stars/Magnetars/MagnetarSGR1806_20.html
http://content.usatoday.com/communities/sciencefair/post/2011/04/magnetar-star-crust-measured/1#.U_3EeGPCY1g

[zeebo]

Thanks for dropping by A:O.  Catch you next time you're "in phase".

In the meantime, check this out.  Neutrinos forged in the heart of the sun have been detected.

[area51drone]

I just found a new home away from bellgab...   I went to see if slooh.com had improved, but just found more marketing junk.    Came across this instead:  http://www.nightskiesnetwork.com

[DigitalPigSnuggler]

In some cases you get one of these: http://www.spacetoday.org/DeepSpace/Stars/Magnetars/MagnetarSGR1806_20.html
http://content.usatoday.com/communities/sciencefair/post/2011/04/magnetar-star-crust-measured/1#.U_3EeGPCY1g

Oooo, magnetars...my favorites!  Dish, girlfriend!

[onan]

I just found a new home away from bellgab...   I went to see if slooh.com had improved, but just found more marketing junk.    Came across this instead:  http://www.nightskiesnetwork.com

1 and a half stars... no horse porn.

[zeebo]

"Astronomers have mapped the cosmic watershed in which our Milky Way Galaxy is a droplet. The massive structure, which the research team dubs the Laniakea Supercluster, extends more than 500 million light-years and contains 100,000 large galaxies."

Laniakea: Our Home Supercluster

[attachimg=1]

The Milky Way (blue dot, center) lives in the outskirts of Laniakea (orange), a galactic supercluster 520 million light-years across. Galaxies (white dots) flow along streams (white lines) toward a central point.


Laniakea: Our home supercluster

[area51drone]

That was very interesting Zeebo, thanks.  What I found most intriguing was the tentacles of the super clusters seem to flow away the common seam (as in the red/black image where they mention that they're shearing apart).    What is causing this obvious seam?  You'd think it would be much more disjointed/irregular, but it almost reminds me of a north/south magnetic field line structure of a bar magnet!

[zeebo]

...What is causing this obvious seam?  You'd think it would be much more disjointed/irregular...

Yes if I understand it right that seam (between superclusters) appears to be like a ridgeline of a watershed, where galaxies flow on one side or the other.  But it's like this uniform break, not a jagged gravitational tangle I'd expect, which I agree is curious.

Also, I wanna know, what is this "Great Attractor"?  I mean what could be so colossal that it's pulling streams of galaxies towards it?  I can only think this is something on a scale way beyond our human comprehension.

[Agent : Orange]

A short gasp while I surface for air

http://newsoffice.mit.edu/2014/alpha-magnetic-spectrometer-detects-positrons-0918

... and back into the depths I go

[Camazotz Automat]

A short gasp while I surface for air

... and back into the depths I go

[Agent : Orange]

The BICEP2 results on primordial gravitational waves have been extremely controversial (and rightly so) since they were announced. Now the Planck team has thrown their hat in the ring with an argument that there may still be a signal but it can't be as powerful as BICEP2 originally indicated because of the dust. Planck did a census of the dust and came up with it's own analysis which showed up a few days ago on the arXiv. For a shorter summary, see
http://arstechnica.com/science/2014/09/gravity-wave-evidence-disappears-into-dust/

The issue isn't yet completely resolved, but it does seem like it must be that at lest part of the signal (maybe all of it) might be due to cosmic dust. In November the Planck and BICEP2 teams are releasing a joint paper, so that will say more about the state of the detection or non-detection of primordial gravitational waves from BICEP2.

Science in action!

[GeorgieForPresident2216]

The BICEP2 results on primordial gravitational waves have been extremely controversial (and rightly so) since they were announced. Now the Planck team has thrown their hat in the ring with an argument that there may still be a signal but it can't be as powerful as BICEP2 originally indicated because of the dust. Planck did a census of the dust and came up with it's own analysis which showed up a few days ago on the arXiv. For a shorter summary, see
http://arstechnica.com/science/2014/09/gravity-wave-evidence-disappears-into-dust/

The issue isn't yet completely resolved, but it does seem like it must be that at lest part of the signal (maybe all of it) might be due to cosmic dust. In November the Planck and BICEP2 teams are releasing a joint paper, so that will say more about the state of the detection or non-detection of primordial gravitational waves from BICEP2.

Science in action!

This is a good illustration of why one team's result does not constitute science in the absence of repeatability.  I think I personally put too much faith in that result as it seemed to verify a number of fundamental but as yet undemonstrated principles.