• Starburst galaxy: Forming stars at rate ~100x faster than Milky Way; star formation often triggered by interaction
• Galaxy interaction: Anything from tidal force, to outright collision. Grazing minor mergers can trigger formation of spiral structure, major mergers can destroy spirals and leave ellipticals
• Galaxy formation: Bottom-up growth: smaller galaxies absorbed by larger galaxies (contrast to top-down star formation process)
• Dark matter in clusters:Can detect via (1) motions of galaxies (2) retention of hot gas (3) strength of gravitational lensing

• Minor merger: Large galaxy absorbs much smaller galaxy; doesn't wreck spiral structure in large galaxy, provides method of growth
• Major merger: Two similarly sized galaxies collide; end result will probably be a large elliptical galaxy
• Group: Small (up to ~50) group of galaxies held together by gravity. The Milky Way is part of the Local Group, along with Andromeda
• Cluster: Large (up to several thousand) group of galaxies held together by gravity, like the Virgo cluster.
• Supercluster: Cluster of clusters; scales 10s of Mpc, 10s of thousands of galaxies involved

The aircraft's 555-mile-per-hour speed (mach 0.85) provided 175-seconds of total eclipse for the passengers to take pictures and record other data. In contrast, persons on a stationary ship on the Arctic sea below would have seen - provided no clouds blocked the view - the moon's 139-mile wide shadow speed past them at 2,740 mph, providing a noticeably shorter total eclipse lasting 132 seconds.

No planetarium in the world could have produced so impressive a natural spectacle as the sun and moon did in the cobalt-blue heavens; although the sight lasted less than 3 minutes, the fantastically beautiful skyscape more than repaid the participants, many of whom were already up before dawn to ready themselves for a round-trip flight of 12 hours.