How big is the universe?
I am preparing a presentation to 16 year old students about "How big is the Universe", mainly about how it is measured. I wondered if you know what is the current record holder for the most distant object from Earth. If you could point me at a URL with pictures I would be grateful. So far I have found this BBC article but it is a little short on astronomical detail and may not be up to date.
You might say that the most distant object visible from Earth is the Cosmic Microwave Background, the remaining heat from the Big Bang which is visible all around us. The Background is found at a distance of about 15 billion light-years from us in all directions. It appears as a smooth, even distribution of thermal radiation with a temperature of about 3 degrees Kelvin. Have look at The COBE site for more info on how the CMB is observed.
If you're picky about what you call an "object," the CMB may not qualify. The most distant objects observed are generally quasars, famously bright nuclei of active galaxies. Quasars are found out to a redshift of about z=6, or about 12 billion light years. (The CMB is at a redshift value of 1000.) Which particular object is the farthest changes almost every week--- there's a lot of stuff out there! Usually, the images of these objects are about the size of a camera pixel, and so don't look very impressive. In any case, you can see the photos from the Keck run of an object at redshift z=5.4 at the Keck Public Site. Have fun!
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