Category Archives: Astronomy

Halo Orbit

John F. Lindner February 7, 2022 5:43 PM

The Webb telescope has fully deployed and arrived at its halo orbit about the second Earth-Sun Lagrange point. But how can it orbit an empty point in space? In the accompanying animated sequence of inertial space diagrams, a star (red) … Continue reading →

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Astronomy Christmas Gift

John F. Lindner December 25, 2021 5:11 PM

I awoke early this Christmas morning to watch the successful launch of the James Webb Space Telescope. I remember the genesis of the telescope a quarter of a century ago when it was called the Next Generation Space Telescope. (The … Continue reading →

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Part Science, Part Art, Part Luck

John F. Lindner November 14, 2021 5:50 PM

Launched just last month, Lucy will be the first spacecraft to visit Jupiter’s trojan asteroids, rocky swarms that orbit about 60 degrees ahead and behind Jupiter in its orbit. Hal Levison, Lucy’s Principal Investigator, has described Lucy’s complicated trajectory, which includes an Earth … Continue reading →

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Dandelin Spheres

John F. Lindner September 6, 2021 9:11 PM

In 1609, Johannes Kepler first described how planets orbit the sun in ellipses. Kepler understood an ellipse as both the locus of points whose distances from two foci sum to a constant and as the intersection of a cone and a plane. But how … Continue reading →

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Free-Fall Spinning Tunnels

John F. Lindner April 28, 2021 9:01 PM

Jump into an evacuated hole drilled straight through a uniform, static Earth-like sphere. Accelerate to 7.9 km/s (or 18 000 m.p.h.) at the center, then decelerate back to zero at the antipodes 42 minutes later! Step out of the hole upside down — … Continue reading →

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Mars Sky Crane

John F. Lindner February 19, 2021 10:29 PM

At the NASA press conference today, chief engineer Adam Steltzner presented three iconic images of the space age: Armstrong’s photo of Aldrin on the lunar surface, Voyager 1’s photo of Saturn and its rings from above the ecliptic, the Hubble … Continue reading →

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Nightfall

John F. Lindner January 28, 2021 1:17 PM

NASA’s Transiting Exoplanet Survey Satellite (TESS) has discovered a sextuply-eclipsing sextuple star system. I think of “Nightfall”. The six stars of TCY 7037-89-I orbit each other in three binary pairs, as in the schematic. The primaries are slightly larger and … Continue reading →

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Losing Betelgeuse

John F. Lindner January 16, 2020 6:51 PM

At my computer Tuesday evening, I receive a message from a university physics chat that is both thrilling and chilling: LIGO + Virgo report a “burst” gravitational wave event, possibly due to a core-collapse supernova (or a binary collision where … Continue reading →

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Black Hole Radii

John F. Lindner April 10, 2019 9:42 PM

I set the alarm for 8:55 AM. Brutal, but I wanted to watch live the National Science Foundation Event Horizon Telescope news conference. I was expecting the first image of a black hole, and the EHT team did not disappoint. … Continue reading →

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The Longest Day

John F. Lindner March 31, 2019 9:52 PM

The December solstice is the longest day of the year, despite being the northern hemisphere’s shortest daylight. Earth’s sidereal day is the time to rotate 360° with respect to distant stars, about 23 hours and 56 minutes, and its solar day … Continue reading →

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