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.

2022 October 17
The featured image shows X-ray rings surrounding GRB 221009A.
Please see the explanation for more detailed information.

X-Ray Rings Around a Gamma Ray Burst
Image Credit: NASA Swift Obs.; Data: B. Cenko (NASA's GSFC), A. Beardmore (U. Leicester) et al.; Processing: J. Miller (U. Michigan)

Explanation: Why would x-ray rings appear around a gamma-ray burst? The surprising answer has little to do with the explosion itself but rather with light reflected off areas of dust-laden gas in our own Milky Way Galaxy. GRB 221009A was a tremendous explosion -- a very bright gamma-ray burst (GRB) that occurred far across the universe with radiation just arriving in our Solar System last week. Since GRBs can also emit copious amounts of x-rays, a bright flash of x-rays arrived nearly simultaneously with the gamma-radiation. In this case, the X-rays also bounced off regions high in dust right here in our Milky Way Galaxy, creating the unusual reflections. The greater the angle between reflecting Milky Way dust and the GRB, the greater the radius of the X-ray rings, and, typically, the longer it takes for these light-echoes to arrive.

Tomorrow's picture: a flowering aurora < | Archive | Submissions | Index | Search | Calendar | RSS | Education | About APOD | Discuss | >

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC,
NASA Science Activation
& Michigan Tech. U.


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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.

2022 October 18
The featured image shows a foreground lake in Sweden
with the Milky Way Galaxy above in on the left and a green
auroral over on the right. At first glance, it may look like
the aurora is a flower growing out of the Milky Way stem.
Please see the explanation for more detailed information.

Milky Way Auroral Flower
Image Credit & Copyright: Göran Strand

It is possible that the stem of our Milky Way could bloom into a flower. It may appear that way in the featured all-sky image. The central plane of our home galaxy can be seen on the left. The sky's center is dominated by bright green-glowing oxygen on the right side of the picture. The two are not connected due to the fact that the red parts of the Aurora are in Earth's atmosphere. 10 trillion times further away, we can see the stars and nebulas of the Milky Way. The picture was taken across a small lake in northern Sweden. As our Sun's magnetic field develops into an active part of its 11-year cycle, it's likely that we'll see more Auroras near both of Earth's poles.

Tomorrow's picture: galaxy grab

< | Archive | Submissions | Index | Search | Calendar | RSS | Education | About APOD | Discuss | >

Authors & editors: Robert Nemiroff (MTU) & Jerry Bonnell (UMCP)
NASA Official: Phillip Newman Specific rights apply.
NASA Web Privacy Policy and Important Notices
A service of: ASD at NASA / GSFC,
NASA Science Activation
& Michigan Tech. U.