Although the Cold Dark Matter Theory predicts the merger of dwarf galaxies, this image captures the first example to be studied in detail. From cosmotography.com/images/dwarf_galaxy_dark_matter.html.

Boise State Physics will host Prof. Yao-Yuan Mao of University of Utah on Friday, Oct 6 for our First Friday Astronomy lecture. Prof. Mao will talk about his work on low-mass galaxies and dark matter, and if the weather permits, we’ll stargaze on Boise State’s Quad after the lecture. In the meantime, let’s explore some of the most common questions people have about dark matter.

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https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022JE007605

Suspended dust mass over time. Vertical lines mark the start of constant-speed descent (solid), visually detected dust lifting under the helicopter (dotted), and touchdown (dashed). The curves for sols 58, 61, 76, and 193 were obtained with the right eye, sol 69 with the left eye, and sol 64 with each eye (right eye dashed). From sol 64, there were times with the helicopter out of the field of view that were not measured.
Friction velocity and helicopter altitude. The Rabinovitch et al. (2021) model, adapted for atmospheric density of 0.020 kg/m3, 2,800 rpm, and Thrust:Weight = 1, is shown as a red dashed line. Horizontal lines show representative thresholds for a conventional model (Shao & Lu, 2000) and a low-pressure model (Swann et al., 2020); the calculated thresholds are for mobilization of sand (200 diameter, 3,200) and aggregates (500 μm, 380 kg/m3). Vertical solid lines show representative altitudes at which dust lifting was seen during landing and traverse; dotted lines are extended upward to 2x the model prediction.
Artist’s depiction of the annular solar eclipse.

On the morning of Saturday, Oct 14, the Sun will transform into the eye of Sauron, a dark circle wreathed in otherworldly flame. Sauron’s gaze will cross the surface of the Earth from the Pacific Ocean, through the Pacific-Northwest and Southwest, and down the spine of Central America, before fizzling out of the east coast of Brazil. Though not as dramatic as total eclipses, annular eclipses like this one are more rare, owing to the eccentricities of orbital mechanics. And the same celestial forces have also woven a tapestry of occultations connecting the Oct 14 eclipse back to the founding of the Cologne Cathedral, a turning point in modern science, and the dawn of a new age.

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This is a reprint of a blog post originally run Jun 2022.
Gravitational lensing of distant galaxies observed by Hubble. From https://www.nasa.gov/content/discoveries-highlights-shining-a-light-on-dark-matter.

Although our current understanding of gravity, the theory of general relativity, arose only one hundred years ago, scientists were speculating about exotic gravitational effects going back to before the word “scientist” even existed. Today, astronomers employ gravity in a variety of ways to study the cosmos, to look for planets outside our solar system and even to weigh some of the largest celestial bodies in existence. These measurements have shed light on some of the darkest of astronomical mysteries.

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From https://webbtelescope.org/resource-gallery/articles. (This is a slightly updated reprint of an article originally run Nov 2021.)

An artist’s concept of the Webb Space Telescope. From https://solarsystem.nasa.gov/missions/james-webb-space-telescope/in-depth/.

NASA’s James Webb Space Telescope (JWST), scheduled to launch on December 18, will primarily use its spectrographs – specialized instruments that capture and spread out light like a rainbow – to study exoplanets. By analyzing this data, known as spectra, researchers will be able to measure exoplanets’ compositions and chemistries. Spectra will help refine what we know about any exoplanet Webb observes, including massive gas giants, mid-sized ice giants, and smaller rocky exoplanets (some of which could be similar to Earth). In a few cases, JWST will deliver images of exoplanets to reveal more about them.

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