Astronomy Picture of the Day (Unofficial)

Astronomy Picture of the Day for 2021-11-23 12:30:01.738594

Astronomy Picture of the Day (Unofficial) at

Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2021 November 23
The featured image shows the Sun in X-ray light as
shown by NASA's NuSTAR satellite -- superimposed on an image
in ultraviolet light taken by NASA's Solar Dynamic Observatory.
Please see the explanation for more detailed information.

The Sun in X-rays from NuSTAR
Image Credit: NASA, NuSTAR, SDO

Explanation: Why are the regions above sunspots so hot? Sunspots themselves are a bit cooler than the surrounding solar surface because the magnetic fields that create them reduce convective heating. It is therefore unusual that regions overhead -- even much higher up in the Sun's corona -- can be hundreds of times hotter. To help find the cause, NASA directed the Earth-orbiting Nuclear Spectroscopic Telescope Array (NuSTAR) satellite to point its very sensitive X-ray telescope at the Sun. Featured here is the Sun in ultraviolet light, shown in a red hue as taken by the orbiting Solar Dynamics Observatory (SDO). Superimposed in false-colored green and blue is emission above sunspots detected by NuSTAR in different bands of high-energy X-rays, highlighting regions of extremely high temperature. Clues about the Sun's atmospheric heating mechanisms come from NuSTAR images like this and shed light on solar nanoflares and microflares as brief bursts of energy that may drive the unusual heating.

Tomorrow's picture: stellar sisters


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Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
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Fire baaaaaaaaaaaaaaaall!!! 🔥

JanKusanagi @identi.ca at 2021-11-23T20:49:35Z