New from NASA's Universe of Learning:
Cosmic Canvas Program Guides, creative, hands-on activities that explore observation and model making through art and science.
The free guides are designed for facilitators of all backgrounds. They include science background information, helpful links, and tips for adapting activities – no science expertise needed.
I was on the project team that created these guides, and I think they are really good. You should check them out. Links below ⬇️
[2312.02636] A new meteor shower from comet 46P/Wirtanen expected in December 2023 https://arxiv.org/abs/2312.02636
Context. Comet 46P/Wirtanen is a near-Earth object (NEO) for which no associated meteor shower has ever been reported. Aims. This study is aimed at improving our understanding of why there has been no observed shower activity for this NEO to date, as well as to consider whether any past activity could be uncovered from the post-prediction results. Methods. The usual dynamic tools for meteoroid streams were used to describe the behavior of the particles ejected by the comet. The resulting modeled meteoroid stream was thoroughly inspected for collisions between the stream and the Earth. Results. The results show a possible encounter forecast for December 12, 2023, between 8:00 and 12:30 UT. The slow entry velocity is typically known to cause dim meteors. The activity level of the shower is highly uncertain due to the absence of reported past showers. Conclusions. Overall, the most optimal observations on the forecasted day would be achieved from Eastern Australia, New Zealand, and Oceania. These observations will help constrain the size distribution of meteoroids from comet 46P/Wirtanen in the millimeter range.
[2311.03310] The Distance to the Stars https://arxiv.org/abs/2311.03310
The distance to the stars is a fundamental parameter, which is determined via two primary methods - parallax and luminosity. While the parallax is a direct trigonometric method, the luminosity distance is usually influenced by interstellar extinction. As long as the optical properties of dust grains are wavelength-dependent this contamination can be corrected. With increasing grain size, however, the extinction properties become grey, i.e. they contribute at wavelengths but can no longer be detected by photometry. However, as the grain size increases, the extinction properties become grey, meaning these particles contribute by a constant at wavelengths below 1 mic, making them undetectable by photometry in the optical. In this study, we compare the parallactic and luminosity distances of a pristine sample of 33 well-known early-type stars with non-peculiar reddening curves and find that the luminosity distance overestimates the parallactic distance in 80% of the cases. This discrepancy can be removed when incorporating a population of large, submicrometer-sized dust grains in a dust model that provides grey extinction which diminishes the luminosity distance accordingly.
Kelly Lepo
Joe Heafner
Bill Montana
Joe Heafner