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Downtime
STScI will be performing network upgrades on the following dates:
  • Sat 17 Apr 2021, 7:00 AM - 2:00 PM EDT (11:00 - 18:00 UTC)
  • Sat 24 Apr 2021, 7:00 AM - 4:00 PM EDT (11:00 - 20:00 UTC)
  • Sat 1 May 2021, 7:00 AM - 4:00 PM EDT (11:00 - 20:00 UTC)
  • Sun 2 May 2021, 7:00 AM - 4:00 PM EDT (11:00 - 20:00 UTC)
  • Sat 8 May 2021, TBD
  • Sun 9 May 2021, TBD
Services may be unavailable or interrupted during these times.

Planetary Nebula Example Spectrum

This figure shows the shortest wavelength portion of the Astro-1 HUT spectrum of the central star in NGC 1535, a high excitation planetary nebula. The downward dips (marked with tick marks) result from absorption by atomic and molecular forms of hydrogen in the surrounding nebula. The largest dip, with an adjacent emission peak at slightly larger wavelength, is produced by a fast wind of material emanating from the central star. (Figure from C. W. Bowers et al. 1995, ApJ, 444, 748.)