APOD: 2021 December 18

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

December 18th, 2021.
See the explanation. Clicking on the picture will bring you to the download page.
The highest resolution version is available.

Stephan's quintet.
The Hubble Legacy Archive is a image credit.
Bernard Miller has a processing and Copyright.

This eye-catching image was constructed with data from the extensive Hubble Legacy Archive and features Stephan's Quintet, the first identified compact galaxy group. Only four of the five galaxies are locked in a dance of repeated close encounters. It's easy to spot the odd man out. There is an overall cast of the interacting galaxies. They have loops and tails that are grown under the influence of disruptive tides. The interacting group is not part of the predominantly bluish galaxy, which is 40 million light-years distant. Stephan's Quintet is within the boundaries of the high flying constellation. This field of view spans about 500,000 light-years and is estimated to be the distance of the four interacting galaxies. Astronomers can identify another galaxy, called NGC 7320C, that is 300 million light-years away, by moving just beyond this field. It would bring the quartet back up to five.

The picture is five in a row.

Robert Nemiroff is an author and Jerry Bonnell is an editor.
Phillip Newman has specific rights.
NASA has a privacy policy on the internet.
There is a service at NASA.
& Michigan Tech. U.

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

December 19th, 2021.
The featured image shows a sunset.
There are five planets in a row.
Please see the explanation for more detailed information.

Italy has planetary alignment.
The image is copyrighted by Antonio Finazzi.

It is not a coincidence that planets line up. All of the planets are in the plane of the ecliptic. Earth dwellers are likely to see the planets in a single band when viewed from inside the plane. It is a coincidence that three of the bright planets are in the same direction. The coincidence was captured earlier this month. The planets Venus, Saturn, and Jupiter were all pictured together in a line just after sunset from the San Fermo Hills. Earth's Moon is joining the alignment with the more distant Uranus. There are clouds in the sky towards the Sun. The planetary alignment should continue for the rest of the month as the comet fades.

There is a graduate student research position open.
Tomorrow's picture is a comet fireball.

Robert Nemiroff is an author and Jerry Bonnell is an editor.
Phillip Newman has specific rights.
NASA has a privacy policy on the internet.
There is a service at NASA.
& Michigan Tech. U.