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Recent Podcast
A Tour of NGC 5128 Flare
A Tour of NGC 5128 Flare
Astronomers have found a pair of extraordinary objects that dramatically burst in X-rays. This discovery, made using data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton observatory, may represent a new class of explosive events. (2016-10-20)

Video Podcasts: The Incredible Two-Inch Universe

Step 4: The Realm of Galaxies

Now let's switch scales one last time, and shrink the entire continent-sized galaxy down to 2 inches:
  • Size of Sun and Stars - Individual stars are invisible, smaller than atoms, at this 2-inch scale. The bright specks in this galaxy image come from the added light of thousands of stars.
  • Location of Sun - 1/2 inch (about 1 cm) from edge of 2-inch galaxy image
  • Distance to Andromeda Galaxy, the Nearest Spiral - 5 feet (1.5 m) at this scale - hold the two galaxy images apart with your arms spread wide.
  • Distance to Farthest Galaxies Observed by Hubble Telescope - 4 miles (6.5 km). In the Hubble image of the "Ultra Deep Field" almost all the fuzzy spots of light are distant galaxies. Because light takes time to travel through space, we see the farthest of these not as they are now, but as they were 12 billion years ago.
  • Size of the Whole Universe? - No one could be infinite.
  • Light Travel Time - It would take 100,000 years for a beam of light to cross our galaxy and 2.5 million years for light to travel from the Andromeda Galaxy to us.
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