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tkdguy

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Speaking of occultations... The latest episode of NOVA, "Star Chasers of Senegal," centers on a project to measure the Trojan asteroid Orus by means of its occultation of a star. This occultation was only visible from Senegal. NASA and a local astronomer recruited a bunch of Senegalese amateurs to record the occultation from many locations, enabling a highly accurate inference (they hope) of Orus' size and shape. This matters because NASA is sending a probe out to fly by several Trojan asteroids, including Orus, and it would be embarrassing to have the probe crash into Orus because they didn't know how big it is.

 

I found it a nifty linkage between the most cutting-edge astronomical exploration -- NASA probes! -- and amateur astronomers whose telescopes had, it looked like, eight inch or so lenses or mirrors? Well within the reach of ordinary hobbyists.

 

There's other interesting stuff about the history of practical astronomy in Senegal and the Islamic world generally. Before that, the Senegal/Gambia region has scads of megalithic circles, like smaller and simpler versions of Stonehenge. Yup, at least some of these ancient stones are calendar sites, aligned to mark the solstices and equinoxes. The culture that built them, however, is apparently unrecorded. Vide my discussion of calendar sites in The Mystic World, the Gambia might be a place to send the PCs in a mage-centric adventure...

 

Dean Shomshak

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There's a long but very complete old paper discussing the 1983 occultation by Pallas (one of the first four asteroids discovered) of a naked-eye bright star here.  It's free access.  A dozen pages list the observing sites and (usually) the observers at those, which now is interesting only if you knew some of the people involved.  (I could have been one of them, but my apartment had suffered a fire less than 3 weeks prior to the event and my life was badly disrupted.)  Finally on page 1652 it shows all the synched occultation traces on a single figure, tracing out the asteroid shape, and a map showing the locations of the observers.  More details are shown on subsequent pages.

 

It pays to recall that the event was in 1983, and the paper came out in 1990.  In 1983 no comet or asteroid had been seen close-up yet.  Comet Halley was visited in 1986 by ESA's Giotto probe, giving our first-ever image of a comet; the first asteroid image came when the Galileo spacecraft flew past Gaspra in 1991 and returned that image.  So at the time this was done, this massive occultation effort was groundbreaking stuff.  Even now, coming up on 40 years later, Pallas has not been visited by spacecraft, though there are now images from the VLT which show some details.

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Neutrino astronomy update, from an article in the March 2023 issue of Scientific American.

 

Astronomers at the IceCube Neutrino Astronomy, located in Antarctica, believe they have identified at least one extragalactic source of very high energy neutrinos: the galaxy NGC 1068, a.k.a. Messier 77. IceCube registers the direction of the neutrinos it detects. It's detected millions of events; out of these, at least several dozen seem to come from this galaxy, 47 million light-years away. These neutrinos are also notable for extremely high energies.

 

So what's making them? The supermassive black hole in NGC 1068's core. The black hole is "active," gobbling up matter, which gets compressed, heated to incredible temperatures, spun around to nearly the speed of light, and generally forced into conditions in which it radiates lots of energy. Astrophysicists have proposed a few ways this could result in the production of ultrahigh-energy neutrinos. And a lot of them:

 

"Fewer than 100 NGC 1068 neutrinos were detected at Earth, but they would have been diluted as they traveled across the vast volume of space. Accounting for this reduction, the astronomers say the total number of neutrinos generated by the black hole must be so huge that they carry away a billion times as much energy as the Sun emits."

 

This brings the number of known sources of astronomical neutrinos to three: the Sun, Supernova 1987A, and now NGC 1068. Astronomers hope to identitfy other sources as well.

 

Dean Shomshak

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As I read once in a different context, "Ah, Nature. You never cease to amaze and terrify me."

 

So glad that supermassive black holes are all safely far away.

 

(Possibly should have posted this in the "Hey Cancer, Stop Trying to Destroy the Universe" thread in NGD, instead.)

 

Dean Shomshak

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