4 ms·

> An event like this is quite rare where the light from a bright star is blocked (or occulted) by an asteroid happening every few decades at most. > a previous

> An event like this is quite rare where the light from a bright star is blocked (or occulted) by an asteroid happening every few decades at most. > a previous occultation of Leona in September 2023 Seems contradictory. Do they mean rare for any given star?

makomk 3y ago
From what I can tell the star that it occulted in September was much too dim to be visible with the naked eye, whereas this is one of the brightest and most easily visible and distinctive stars in the night sky.
- xorbax 3y ago
  If you're accepting a dim star only visible through space instruments I imagine it happens near-constantly Having it happen to a star you're actually aware of and can see tonight is pretty cool
svat 3y ago
The key word is "bright". It's clearer in the other article: https://skyandtelescope.org/astronomy-news/asteroid-will-cover-betelgeuse-may-reveal-its-visible-surface/ https://skyandtelescope.org/astronomy-news/asteroid-will-cov... > An occultation of a 1st-magnitude star is rare — such an event is visible from Earth only every few decades and > That changed on September 13, 2023: In advance of the December event, Leona occulted another object, this time of a 12th-magnitude star. It makes sense: there are only a few bright (1st-magnitude) stars so occultation of them is rare, while there are a lot of stars in the sky so occultation of some (dim) star is not very rare. ———— Edit: We can come up with a more explicit expression. If each individual star has an occultation once every k days, then "at least one of N stars" has an occultation roughly once every 1/(1-(1-1/k)^N) ≈ k/N days. So if with N=22 (the number of 1st-magnitude stars: https://en.wikipedia.org/w/index.php?title=First-magnitude_star&oldid=1169525927#Table_of_the_22_first-magnitude_stars https://en.wikipedia.org/w/index.php?title=First-magnitude_s... ) this is once in 40 years (say), then with N = 10000 stars you'd see about once a month.

makomk 3y ago

From what I can tell the star that it occulted in September was much too dim to be visible with the naked eye, whereas this is one of the brightest and most easily visible and distinctive stars in the night sky.

xorbax 3y ago
If you're accepting a dim star only visible through space instruments I imagine it happens near-constantly Having it happen to a star you're actually aware of and can see tonight is pretty cool

svat 3y ago

The key word is "bright". It's clearer in the other article: https://skyandtelescope.org/astronomy-news/asteroid-will-cover-betelgeuse-may-reveal-its-visible-surface/ https://skyandtelescope.org/astronomy-news/asteroid-will-cov... > An occultation of a 1st-magnitude star is rare — such an event is visible from Earth only every few decades and > That changed on September 13, 2023: In advance of the December event, Leona occulted another object, this time of a 12th-magnitude star. It makes sense: there are only a few bright (1st-magnitude) stars so occultation of them is rare, while there are a lot of stars in the sky so occultation of some (dim) star is not very rare. ———— Edit: We can come up with a more explicit expression. If each individual star has an occultation once every k days, then "at least one of N stars" has an occultation roughly once every 1/(1-(1-1/k)^N) ≈ k/N days. So if with N=22 (the number of 1st-magnitude stars: https://en.wikipedia.org/w/index.php?title=First-magnitude_star&oldid=1169525927#Table_of_the_22_first-magnitude_stars https://en.wikipedia.org/w/index.php?title=First-magnitude_s... ) this is once in 40 years (say), then with N = 10000 stars you'd see about once a month.