Category Archives: Astronomy

An Interstellar Visitor?

Astronomers are now working on determining if a recently discovered asteroid is an interstellar visitor. The first observations of this asteroid were made by a team of researchers at the University of Hawaii's Pan-STARRS 1 telescope on Haleakala in Hawaii (Figure 1). Continue reading

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Estimating Asteroid Sizes Using Excel 2D Data Table

I recently gave a seminar on how to design products using Thermoelectric Coolers (TECs). During this presentation, I showed the audience how to generate various tables and graphs using Excel data tables. I was surprised to learn that no one in the audience had ever seen an Excel data table in action. Since the middle of a seminar on TECs is probably not the best time to divert to some Excel training, I decided to prepare a simpler example the would be easier to understand on first exposure. Continue reading

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Calculate Eclipse Path Width

Yesterday, a reader asked me how to compute the totality path width for the eclipse that will cross the US on 21 Aug 2017. I wrote a post on how to perform this calculation years ago. NASA has published a path width value of 114.7 km. This width will actually vary a bit as the shadow moves across the Earth because the distance change slightly between all the bodies involved. Also, the Earth and Moon are not perfectly round, which I assume. NASA has very detailed models that even include the variations due to mountains and valleys on the Moon. Continue reading

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Old-School Selling of the Exploration of Mars

My youngest son has been fascinated with Elon Musk's plans for colonizing Mars. He is not that different from his old man because in my youth Wernher von Braun (Figure 1) had me captivated with his plans for human-crewed missions to Mars. As I described von Braun's plans for exploring Mars to my son, I realized the both Musk and von Braun applied similar state-of-the-art marketing approaches. Continue reading

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Ion Propulsion Math

NASA has a project known as Dawn that put a space probe in orbit around the asteroids Vesta and then Ceres. CSPAN presented an excellent Dawn mission briefing given by Marc Rayman, the Mission Director and Chief Engineer. One of the most interesting aspects of the Dawn spacecraft is its use of an ion thruster to maneuver it from one destination to another. This post presents some simple math that can be used to determine some of its key performance characteristics. Continue reading

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Interstellar Radio Communication Misfire

There were an interesting series of news articles recently about the detection of a possible radio signal from the star HD164595. The actual detection occurred about a year ago, but it came to the public's attention after an astronomer mentioned it in a recent presentation. Close inspection of the results indicate that the transmission was either from a Russian military satellite or electronic noise sources down on Earth. Continue reading

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View of Jupiter From Satellite Metis

The arrival of the Juno spacecraft at Jupiter has motivated me to take a look a closer look at the Jovian system. I was surprised to see that we have cataloged 67 moons, sixteen of which have been discovered since 2003 and are not yet named. One moon that was new to me is called Metis (Figure 2), which is Jupiter's innermost moon. It is very tiny and resides within Jupiter's main ring. Continue reading

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Asteroid Size Estimation

I often see announcements of Near-Earth Objects (NEOs) in the scientific press. For asteroids, these announcements are usually accompanied by a size estimate of the asteroid. In this post, I will discuss a commonly used formula for the effective spherical diameter of an asteroid based on its normalized brightness (i.e. absolute magnitude). Continue reading

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Asteroid Impact Damage Estimate

I have seen a number of articles in the popular scientific press about asteroid 1997 XF11 and the close approach it made to Earth back in June. The June approach was not that close – ~27 million kilometers. The closest approach is expected in 2028 and will be 980,000 km or 2.4 times the average Earth-Moon distance. Continue reading

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Planetary Atmosphere Leakage

I have always been interested in the fact that some planets have atmospheres and others do not. At the time of formation, planets have a primary atmosphere that consists largely of light elements (hydrogen and helium) – Earth has a secondary atmosphere formed outgassing from tectonic activity and comet impact residue. For small bodies, these low-molecular weight elements escape into space. I had never looked at how these gases escaped until I recently found a Wikipedia article about how gases escape from planetary atmospheres (e.g. Figure 1), and the math and physics involved were too enticing to pass up. Continue reading

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