Skip to ContentGo to accessibility pageKeyboard shortcuts menu
OpenStax Logo
Astronomy 2e

Key Terms

Astronomy 2eKey Terms
active region
an area on the Sun where magnetic fields are concentrated; sunspots, prominences, flares, and CMEs all tend to occur in active regions
aurora
light radiated by atoms and ions in the ionosphere excited by charged particles from the Sun, mostly seen in the magnetic polar regions
chromosphere
the part of the solar atmosphere that lies immediately above the photospheric layers
corona
(of the Sun) the outer (hot) atmosphere of the Sun
coronal hole
a region in the Sun’s outer atmosphere that appears darker because there is less hot gas there
coronal mass ejection (CME)
a solar flare in which immense quantities of coronal material—mainly protons and electrons—is ejected at high speeds (500–1000 kilometers per second) into interplanetary space
differential rotation
the phenomenon that occurs when different parts of a rotating object rotate at different rates at different latitudes
granulation
the rice-grain-like structure of the solar photosphere; granulation is produced by upwelling currents of gas that are slightly hotter, and therefore brighter, than the surrounding regions, which are flowing downward into the Sun
Maunder Minimum
a period during the seventeenth century when the number of sunspots seen throughout the solar cycle was unusually low
photosphere
the region of the solar (or stellar) atmosphere from which continuous radiation escapes into space
plage
a bright region of the solar surface observed in the light of some spectral line
plasma
a hot ionized gas
prominence
a large, bright, gaseous feature that appears above the surface of the Sun and extends into the corona
solar flare
a sudden and temporary outburst of electromagnetic radiation from an extended region of the Sun’s surface
solar wind
a flow of hot, charged particles leaving the Sun
sunspot
large, dark features seen on the surface of the Sun caused by increased magnetic activity
sunspot cycle
the semiregular 11-year period with which the frequency of sunspots fluctuates
transition region
the region in the Sun’s atmosphere where the temperature rises very rapidly from the relatively low temperatures that characterize the chromosphere to the high temperatures of the corona
PreviousNext
Order a print copy
Citation/Attribution

This book may not be used in the training of large language models or otherwise be ingested into large language models or generative AI offerings without OpenStax's permission.

Want to cite, share, or modify this book? This book uses the Creative Commons Attribution License and you must attribute OpenStax.

Attribution information
  • If you are redistributing all or part of this book in a print format, then you must include on every physical page the following attribution:
    Access for free at https://openstax.org/books/astronomy-2e/pages/1-introduction
  • If you are redistributing all or part of this book in a digital format, then you must include on every digital page view the following attribution:
    Access for free at https://openstax.org/books/astronomy-2e/pages/1-introduction
Citation information

© Jul 8, 2024 OpenStax. Textbook content produced by OpenStax is licensed under a Creative Commons Attribution License . The OpenStax name, OpenStax logo, OpenStax book covers, OpenStax CNX name, and OpenStax CNX logo are not subject to the Creative Commons license and may not be reproduced without the prior and express written consent of Rice University.