how much of the outer universe can we see from where we are?

[boo]

in terms of looking out of the milky way to the other galaxies in the outer universe 

how much of it can we see from our location in the milky way?

for exmaple, imagining the milky way disc was a clock

if we are at 6 o clock now ,in the milky way,  that if we were at 7 o clock, or 3 o clock we would see a whole different selection of galaxies?

or can we already see the full 360 degrees of the observable universe from where we are using the instruments we have?

unless you guessed, im no scientist, so go easy please LOL

[MigL]

The central 'hub' of our galaxy lies in the direction of the constellation Sagittarius.
Stars and nebulae are so dense in that direction that anything beyond it is effectively obscured.
( in some EM wavelengths much more than others )

The galaxy is, of course, rotating with a period of approx. 200 000 years, so the field of view is slowly, but constantly, changing.

[Janus]

About 10% of the universe is "hidden" from our view by the bulk of our own galaxy (20% if you only consider the visible part of the spectrum).   This won't change much due the rotation of the galaxy as this is mostly due to having to view through the disk of the galaxy.

 

[Ghideon]

2 minutes ago, Janus said:

About 10% of the universe is "hidden" from our view by the bulk of our own galaxy

Would we be able to "see" gravitational events in that direction, such as massive black holes merging? 

 

[Markus Hanke]

14 hours ago, Ghideon said:

Would we be able to "see" gravitational events in that direction, such as massive black holes merging? 

 

Yes, though perhaps not visually. But you would still be able to detect the gravitational radiation emitted by such an event, since gravitational waves cannot be shielded by ordinary matter.

[Airbrush]

On 10/22/2020 at 7:52 AM, Janus said:

About 10% of the universe is "hidden" from our view by the bulk of our own galaxy (20% if you only consider the visible part of the spectrum). 

Very interesting.  It is hard for me to believe that the narrow band of the Milky Way, that we can see in the sky, hides 20% of visible light from the universe.  Consider that narrow band compared to the entire sky, as viewed from the northern and southern hemispheres, surely we must see more of the observable universe than only 80% of it.  Can you provide a source for your claim that the galaxy obscures 20% of visible light from the entire universe?  Thank you, no hard feelings. 🙂

Edited October 26, 2020 by Airbrush

[Janus]

2 hours ago, Airbrush said:

Very interesting.  It is hard for me to believe that the narrow band of the Milky Way, that we can see in the sky, hides 20% of visible light from the universe.  Consider that narrow band compared to the entire sky, as viewed from the northern and southern hemispheres, surely we must see more of the observable universe than only 80% of it.  Can you provide a source for your claim that the galaxy obscures 20% of visible light from the entire universe?  Thank you, no hard feelings. 🙂

https://en.m.wikipedia.org/wiki/Zone_of_Avoidance

[MigL]

I would have thought that to be true when viewing through the center of the galactic disk.
But I would have thought that, when viewing towards the outer rim of the disk, infrared and microwaves would easily get through, even as most visible wavelengths would be appreciably attenuated by gas/dust and a lot fewer stars.

edit
And I guess I thought wrong.
Although I do see mention of that effect in your link, Janus.

Edited October 27, 2020 by MigL

[Danijel Gorupec]

On 10/22/2020 at 12:42 AM, MigL said:

The galaxy is, of course, rotating with a period of approx. 200 000 years...

I guess, you forgot to add three more zeros.

[Airbrush]

12 hours ago, Janus said:

https://en.m.wikipedia.org/wiki/Zone_of_Avoidance

"When viewing space from Earth, the attenuation, interstellar dust, and stars in the plane of the Milky Way (the galactic plane) obstruct the view of around 20% of the extragalactic sky at visible wavelengths. As a result, optical galaxy catalogues are usually incomplete close to the galactic plane."

Thanks for the link.  This still doesn't make sense to me, because it is counter-intuitive.  The galactic plane is a narrow band we see across only ONE side of the sky at night.  That narrow band does not look like 20% of the sky.  So the "attenuation" must be not only looking toward the center of the galaxy but all around us on the galactic plane, right?  Not just the "zone of avoidance" which lurks behind the central band of the Milky Way, which conceals what the Milky Way is heading for, right?

Edited October 27, 2020 by Airbrush

[MigL]

7 hours ago, Danijel Gorupec said:

I guess, you forgot to add three more zeros.

Yeah, 200 mill, not 200 thou.

 

49 minutes ago, Airbrush said:

The galactic plane is a narrow band we see across only ONE side of the sky at night.

Yeah, as I said I thought the same thing, however, we are located near the Orion arm of the galaxy, about 30 000 LY from the galactic center, and about 20 000 LY from the edge of the galactic disk. And there s enough gas, dust and stars between us and the edge to block most of our view.
The zone of avoidance s a band that encircles us.

[Janus]

1 hour ago, Airbrush said:

"When viewing space from Earth, the attenuation, interstellar dust, and stars in the plane of the Milky Way (the galactic plane) obstruct the view of around 20% of the extragalactic sky at visible wavelengths. As a result, optical galaxy catalogues are usually incomplete close to the galactic plane."

Thanks for the link.  This still doesn't make sense to me, because it is counter-intuitive.  The galactic plane is a narrow band we see across only ONE side of the sky at night.  That narrow band does not look like 20% of the sky.  So the "attenuation" must be not only looking toward the center of the galaxy but all around us on the galactic plane, right?  Not just the "zone of avoidance" which lurks behind the central band of the Milky Way, which conceals what the Milky Way is heading for, right?

That "Narrow band" is a lot wider than it looks to the naked eye. You are only seeing that part that is bright enough.

As an example, consider the Andromeda galaxy.  To the naked eye it looks like a small fuzzy spot, but if you could see it in full, it would appear like this in the sky.

Several times wider than a full Moon. 

What we see by naked eye is just the nucleus of the galaxy. But just because we don't see the disk by naked eye doesn't mean that it doesn't hide the light from galaxies behind it.

 

[Bufofrog]

21 hours ago, Janus said:

As an example, consider the Andromeda galaxy.  To the naked eye it looks like a small fuzzy spot, but if you could see it in full, it would appear like this in the sky.

Along those same lines, many people don't realize that those beautiful pictures of nebulae, like the Orion nebula, are not something that a person could see no matter their location in space.  Even if you were relatively close to the Orion nebula it would just look like a diffuse haziness in the night sky.  Time lapsed and stacking of images makes the really nice pictures.

[boo]

On 10/27/2020 at 3:42 PM, Janus said:

That "Narrow band" is a lot wider than it looks to the naked eye. You are only seeing that part that is bright enough.

As an example, consider the Andromeda galaxy.  To the naked eye it looks like a small fuzzy spot, but if you could see it in full, it would appear like this in the sky.

Several times wider than a full Moon. 

What we see by naked eye is just the nucleus of the galaxy. But just because we don't see the disk by naked eye doesn't mean that it doesn't hide the light from galaxies behind it.

 

its such a pity that andromeda doesnt actually look like this to the naked eye

[Airbrush]

On 10/27/2020 at 8:42 AM, Janus said:

That "Narrow band" is a lot wider than it looks to the naked eye. You are only seeing that part that is bright enough.

What we see by naked eye is just the nucleus of the galaxy. But just because we don't see the disk by naked eye doesn't mean that it doesn't hide the light from galaxies behind it.

So the dust clouds towards the center of the galaxy are much broader than the band of visible stars.  Also, since we are not on the edge of the galaxy, there are dust clouds all around us in our spiral arm, and others, blocking starlight on the plane of the galaxy, right?