Furthest observed object...

Factual Questions
1

I have two questions that arent really related:

Seems pretty straightforward. What’s the furthest object from earth that has ever been obvserved and how many lightyears away was it?

Second question is, how exactly can an image of the Milky Way galaxy be captured? I mean, I cant take a picture of the exterior of my house, if I’m still in my room.

Thanks,

culov

2

The Milky Way question - IANA Astronomer, but I believe that they view what they can from here, and then extrapolate what the Milky Way looks like, by comparing what they can ascertain about it, to other similar galaxies. Et voila, a picture of what our galazy should look like…

The furthest object is something they saw with Hubble - check out http://hubblesite.org - I’m sure they list it somewhere there…

Hope that helps.

3

The most distant object that I could find is a quasar at redshift Z = 6.4. But there’s probably a more distant one now. In March 2000, the most distant quasar we’d found was at redshift 5.5, and in July 1997 it was 4.92.

The thing is, redshift is related to distance, but it’s hard to say exactly how. Look at the last table on this page. The row for which Z = 6.5 corresponds to a light travel time of anywhere from 9.62 to 12.18 billion years, depending on the cosmological parameter Omega. I think that the low end (Omega = 0.1) is what we usually go with, so 12.18 billion years sounds about right. Normally we say that this means that the quasar is 12.18 billion light-years away. Of course technically the quasar has moved since the time we’re observing it, and distances are more complicated in cosmology anyway, but that’s the most basic answer.

Good question, and you’re right. No such photo exists. It’s all either drawings or photos of other galaxies. [SDStaff Chronos on the Milky Way’s shape]

4

The furthest “object” (if you can call it that) observed is the Cosmic Background Radiation (aka Cosmic Microwave Background). You can’t look any further because the universe is opaque beyond that point. Or, the universe was opaque before that time. (Looking further away in distance means looking further back in time.)

5

The Cosmic Microwave Background (CMB) is at a redshift of 1000, by the way.

6

Thanks for quickly answering my questions everyone!

-culov

7

I quite like the map of the Milky Way galaxy on this page,
http://anzwers.org/free/universe/milkyway.html
put together from three different sources, including the study mentioned in Chronos’s staff report.

SF worldbuilding at
http://www.orionsarm.com/main.html

8

The CMB isn’t really a single object. If you meant like a star or something like that, then the quasar mentioned above is your goal. There may be new things happening soon. Swift, a satellite due for launch early next year, may detect huge explosions from the first generation of stars born in the Universe. They would be at a redshift of 10-16 or so; that means they are 13 or so billion light years away. They formed 200 million years after the Universe itself formed.

As to the second question, mapping the Galaxy can be done in many ways. Gas clouds trace the shape of the spiral arms, and these can be seen all the way across the Milky Way using radio waves, for example. Infrared pierces the veil of dust as well, allowing stars to be observed that are otherwise invisible to optical light. Other methods abound.

So we can make a map of what our house-- the Galaxy-- must look like, even though we’ve never been outside it. It also helps to know what other galaxies look like for comparison too.