Small nether world

Pluto is like a departed friend.

See the end note about enlarging illustrations.

It is at opposition on July 19, but don’t expect to be able to see it.

Many still wish for the little planet back. Discovered in 1930, it was demoted, amid much debate, from major planet to dwarf planet in 2006.

It departed outward, below the equator in 1988, past the orbit of Neptune in 1999, below the ecliptic in 2018. It is now distant by more than 34 astronomical units (AU, Sun-Earth distances), 22° down in the southern hemisphere, dimmer (at magnitude more than 14) than thousands of stars. Like the god of the underworld for which it is named, Pluto is plumbing the abyss of space.

That’s nonsense, of course: a planet on an outward leg of its orbit is rising away from the Sun, like a stone lobbed upward. Pluto will slow to its aphelion, the most distant point of its orbit, 49 AU away, in 2114.

Here is part of our space view of the outer planets, on page 115 of Astronomical Calendar 2022:

Our book Uranus, Neptune, Pluto tells the tangled human story of Pluto’s discovery, and the recent discovery of what an interesting little world it is. This is one of the book’s illustrations, in a section about the relation of Pluto’s orbit to that of Neptune, of which it was once as satellite.

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ILLUSTRATIONS in these posts are made with precision but have to be inserted in another format.  You may be able to enlarge them on your monitor.  One way: right-click, and choose “View image” or “Open image in new tab”, then enlarge.  Or choose “Copy image”, then put it on your desktop, then open it.  On an iPad or phone, use the finger gesture that enlarges (spreading with two fingers, or tapping and dragging with three fingers).  Other methods have been suggested, such as dragging the image to the desktop and opening it in other ways.

Sometimes I make improvements or corrections to a post after publishing  it.  If you click on the title, rather than on ‘Read more’, I think you are sure to see the latest version.  Or you can click ‘Refresh’ to get the latest version.

This weblog maintains its right to be about astronomy or anything under the sun.