Holland in the Sky: Night Watch and Starry Night

Since December 17, the Netherlands has two new far outposts: the planet Night Watch and the star Starry Night. The IAU, the International Astronomical Union, asked us to come up with a name for those two celestial bodies, which were previously known under the somewhat boring character combinations HAT-P-6 and HAT-P-6b. The inhabitants of the 111 other countries affiliated with the IAU were also assigned a cosmic duo, as part of the NameExoWorlds campaign.

Rembrandt and Van Gogh

Out of 6,000 suggestions submitted by the public, the national jury chose a shortlist of five name twins, of which Nijntje (Miffy) and Moederpluis (Mother Bunny) were the most popular in an election. But on second thought, that wasn’t such a good idea, for legal reasons. And so it became Night Watch and Starry Night, after the famous paintings by Rembrandt and Van Gogh. With the added advantage that these names, with all thier ch-sounds, are virtually unpronouncable for foreigners.

Star Sterrennacht and planet Nachtwacht, named by the Dutch public after a request by the International Astronomic Union, scematically rendered with the right dimensions and distance
Starry Night and Night Watch with distances and dimensions to scale

We cannot go there, at least not in the foreseeable future: Nachtwacht and Sterrennacht are 910 light-years away. So even a spaceship that can travel at the speed of light takes almost a millennium for a one way trip.

Precise

The star is visible with a telescope, the planet is not; it was discovered by subtle variations in the brightness of its mother star. It’s amazing how many precise data about the layout and dimensions of Nachtwacht can be derived through this method. The planet is 1.33 times as large as Jupiter: its diameter is 190,000 kilometers. The distance to Sterrennacht is only 7,800,000 kilometers, one twentieth of the distance from the Earth to the Sun. The orbital period is therefore very short: a year on Nachtwacht is slightly shorter than four Earth days.

Artist impression of the "Dutch" planet Nachtwacht (Night Watch) as a red, white and blue gas giant
Tricolore planet

Tricolore

What Nachtwacht looks like: we have no idea. It is most likely a gas giant, something like Jupiter but a little bit bigger. A sphere with no fixed surface and with cloud bands in the rotational direction of the planet. The same visualization pops up in every media report and on Wikipedia, showing a typical gas giant. To me it seems to be drawn too close to its star, probably for the dramatic effect.

But if we do not know for now, we can of course assume that the cloud bands on planet Nachtwacht are alternately red, white and blue, the colors of the Dutch flag. I leave it to the planetary scientists to find out what chemical processes in the atmosphere would cause that striking color scheme. Earth’s water clouds are white, the atmosphere of Neptune has the right shade of blue so especially the red is still a mystery. Anyway, I just came back from a virtual voyage I made to the planet in order to produce an alternative artist impression.

Artist impression of the planet Nachtwacht (Night Watch), a red, white and blue gas giant, with two of ots moons as well as parent star Sterrennacht (Starry Night)
Nachtwacht, Sterrennacht, Schellingwou and Wormskerk

Moons

We also see two of Nachtwacht’s moons on this picture. Their existence has not yet been scientifically proven, but they will undoubtedly be there; the gas giants in our own solar system also have dozens of them. I propose naming those satellites after characters in the painting Night Watch. I call that light gray one top right Schellingwou, the purple one on the left in the background is called Wormskerk.

Mystery

And that bright spot at the bottom right, what’s that? To be honest, I don’t really know. A spaceship? A tiny moonlet? A photon torpedo? Or just a lens effect? Well, it’s good to have at least some mysteries left.

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