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tkdguy

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  • 2 weeks later...

Marcus house brings the weeks news on the last day of 2022, and then doest a retrospective of the year's launches.  Sure, it's mostly Space-X, putting up Starlink satellites, but there is a lot of private space going up. THis year really had a very hig Optempo, and Elon promises more in 2023.

 

 

 

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  • 2 weeks later...
On 1/22/2023 at 10:53 AM, Scott Ruggels said:

 Tech 8 Non Jump Capable Traveller?

https://www.nextbigfuture.com/2023/01/avatar-movie-valkarie-antimatter-rocket-design-is-a-real-design.html

 

 

Apparently the ship from Avatar, and Avatar: The Way of Water is a real ship design.

 

On the detectability of Antimatter Propulsion Spacecraft

 

Plausible designs are detectable, and recognizable out to a few hundred parsecs.  Probably further out now (that paper is from 1986).

 

(The author also wrote a follow-up article some years later which I haven't seen, because I'm too cheap to pony up 15 quid for a reprint from the British Interplanetary Society)

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Weekly Space News, by the cheerful Australian, Marcus House
 

 

U.S. Air Force shoots down a high altitude "not a balloon" Over the Yukon. (with Canadian Permission)

https://www.msn.com/en-us/news/other/high-altitude-object-shot-down-over-northern-canada/ar-AA17ndgF

 

"Cylindrical Object" may be one of those Tic Tac shaped things the Navy spotted a few years ago. Canadian Forces get dibs on the wreckage.

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A new paper in Nature leaves me thinking more and more that there's lots of wholly unimagined weird stuff out past Neptune (along the bizarre circumstances of the Kuiper Belt object Arrokoth, past which the New Horizons spacecraft flew a couple years back, and was found to be a contact binary of two roughly disk-shaped small objects).  The paper is almost certainly behind the paywall.  ESA (European Space Agency) has a press release not behind a paywall here, though that lacks the "crunchy bits" of data I prefer to read before passing on news.

 

The trans-Neptunian object 50000, named Quaoar, is about 555 km in diameter.  It has a small satellite, named Weymot, about 80 km in diameter, orbiting Quaoar about 24 Quaoar radii out.  The TNO itself was discovered from Mt Palomar in 2002; the moon was discovering using HST in 2006.  Both were detected by direct imaging.

 

The new paper reports discovery of a ring around Quaoar, discovered by observing four occultations of stars.  An occultation is when one body "walks in front of" another and blocks it from view temporarily.  (An eclipse can be an occultation, but the word occultation is preferred when you're observing at least one "point object", usually a star far in the background, and its light is blocked by a much closer -- usually Solar System -- object which you may or may not be able to detect by any other means.)  Timing exactly when and for how long the background star "blinks out" gives you indications of a very precise position of the occulting body and its dimensions, since you usually have a pretty good idea of the occulting object's orbit around the Sun.  If the occulting object has an atmosphere, seeing a gradual "fade-out" of the background star as the occulting object drifts in front of it can give you information about the extent and structure of that atmosphere.  If you can get a number of observers scattered across Earth to observe a given occultation event, you can get a lot of information about shape, size, etc.

 

The ring is inhomogeneous, i.e., it is not uniformly dense all the way around.  That sort of thing has been seen before; at least one of the rings of Uranus is denser in some places than others.  (Because occultations are not like images and don't give you measurements of the complete ring, only at very specific points on it, it seems possible to me that the ring is in fact incomplete, that is, it's better described as an arc rather than a full ring.)  The surprise is that ring is out at 7.4 Quaoar radii from the TNO.  That is well outside the classical Roche limit of Quaoar, which is the distance inside which tidal forces of the central body will disrupt (tear apart) a decent-size moon.  All the other ring systems we know about, including the one around another TNO named Haumea (which was discovered some 6-8 years back, also by occultation), are inside that limit.  (In general, there's nothing stopping material that distance from the central body from clumping up and forming a moon.)  They do some dynamical calculations about rings out that far.  Maybe a clue is that both Haumea's ring and Quaoar's ring are in 1:3 spin-orbit resonance with their central bodies (that is, the orbital period of a ring particle is 3 times the rotation period of the central body), though that may also be a coincidence.

 

On a more general basis, occultation studies are kind of the ultimate form of opportunism; it requires that you know the position of a star extremely precisely, and that some Solar System object is going to walk in front of it in circumstances you can observe.  That's a low-odds bet, generally.  The ongoing GAIA mission is producing high-precision stellar motion and position measurements literally by the million, and it is those that enabled this published study of Quaoar to be done.

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