319 Leona
en.wikipedia.orgIt appears that astronomers are already preparing for the upcoming occultation of 319 Leona with Betelgeuse.
Researchers in this July 2023 presentation note:
> Leona’s Long Rotation Period (430h) complicates determination of its size and shape.
> So it is VERY IMPORTANT that some OTHER occultations by Leona be observed from multiple stations BEFORE December 12, to take best advantage of this unique opportunity.
[0] https://occultations.org/publications/rasc/2023/2023Dec12Leo...
And there is already at least one other set of observations reported on arXiv from a September 2023 occultation:
> The stellar occultation by (319) Leona on 13 September 2023 in preparation for the occultation of Betelgeuse
> This represents an extraordinary and unique opportunity to analyze the diameter and brightness distribution of Betelgeuse's photosphere with extreme angular resolution by studying the light curve as the asteroid occults the star from different points on Earth and at different wavelengths. Here we present observations of another occultation by Leona on 13 September 2023 to determine its projected shape and size in preparation for the December 12th event.
[1] https://arxiv.org/abs/2309.12272
(Amazing that it was posted ~8 days after the observations were made!)
Why must the observations of other occultations be done before and not immediately after?
The recording of the meeting discussing the presentation [0] notes three issues with occlusions by Leona:
1. There is uncertainty with regard to the path, i.e. exactly where will it be projected on the surface of the Earth.
2. Size of Leona is uncertain, hence the expected magnitude of the decrease in brightness of Betelgeuse as a result of occultation was uncertain. A bigger decrease means that it's easier to get the public involved in observing.
3. The group looking at this is doing citizen science. They need to know the above in order to decide how much to involve public because this is something where if the above is known, then the public can participate with DSLR cameras and record light curves suitable for astronometric analysis.
[0] https://www.youtube.com/watch?v=ok7hJ_2DPhM&ab_channel=IOTAA...
That's quite the slow tumble. Back in high school a person in the area with a big fancy computerized telescope let a bunch of us physics students come up to do experiments. My partner and I decided to try to plot light curves for some famous asteroids and we were able to confirm that they were still rotating as last observed over periods that let us do this overnight.
> On 12 December 2023 Leona will occult Betelgeuse as seen from southern Europe.
> On 12 December 2023 at about 01:09–01:27 UT, Leona will occult Betelgeuse as seen from southern Europe, Turkey, Greece and Sicily.[14] The 14th magnitude asteroid will occult Betelgeuse (block or reduce the light) for about 12 seconds. Betelgeuse is expected to dim by about 3 magnitudes.[16] Light curve studies of the event may help understand the distribution of brightness over the disk of Betelgeuse.
Betelgeuse is the 10th brightest star. It's dimming by a factor of ~16, but will still be visible, which surprises me. Does anyone know whether this is because (a) Betelgeuse's diffuse disc is wider than the asteroid's, (b) Betelgeuse will refract around the asteroid, or (c) something else? I'm guessing (b) but don't know much about this.
The primary source of the 3 magnitude dimming is this data: https://www.asteroidoccultation.com/2023_12/1212_319_82912_S...
It seems to be based on a very crude estimation, see the data near the bottom. It estimates Betelgeuse to have an angular diameter of 48.10 milli-arcseconds, and the astroid's angular diameter to 46.0 milli-arcseconds, which works out to a 11.7 dimming factor.
But the summary there says this?:
> In the case of an occultation, the combined light of the asteroid and the star will drop by 13.72 mag to 14.22 mag (the magnitude of the asteroid) for at most 11.620 seconds.
Which suggest complete blockage of the star's light.
Per wikipedia, dimming by 3 magnitudes means Betelgeuse will still be at +3-+4.6, which is probably too dim to be seen in a city, but still plenty bright.
> This section needs expansion with: details about the unusual occultation. You can help by adding to it. (May 2022)
Asteroids are very valuable targets in the solar system. It's because they're low delta vee to get to, and don't require high thrust since they don't have a deep and steep gravity well. This means electric propulsion can be used. Trip times might be long though.
One could extract materials from asteroids and bring them anywhere in space with low delta vee budgets.
what is this particular asteroid made of? Iron?
Nevermind. It's a C-type asteroid.
https://en.wikipedia.org/wiki/C-type_asteroid
A chunk of coal mixed with pebbles
Just one example:
If you want to go anywhere in space with chemical propulsion, most of your mass will likely be oxygen. For example oxygen-hydrogen rockets often have 6:1 mass ratio of oxygen to hydrogen. SpaceX Raptor has 3.6:1.
Having a low delta vee source of oxygen is potentially extremely valuable.
Hydrocarbons and water also are very useful.
Is this as a heads up due to it's upcoming occultation of Betelgeuse or...?