The Bussard ramjet won’t work as well as you think it could. A new study does the math on John Fishback’s contribution to the ramjet—gathering protons from the interstellar medium for the ramjet’s fusion drive via a magnetic scoop—and concludes that while it’s physically possible, there are substantial constraints: the cut-off speed is lower than expected, limiting the effects of time dilation, and the magnetic field would have to be something like 4,000 km wide and 150 million km long in order to work. In other words: for certain very preposterous values of physically possible. [Universe Today]
Astronomy & Space
Exoplanets Capable of Sustaining a Rich Biosphere Are Probably Rare
Just because a planet is in its star’s Goldilocks zone doesn’t mean it’ll be capable of supporting an Earth-like biosphere. A new study focuses on the amount of radiation in the wavelengths usable by photosynthetic plants; “the team discovered that stars around half the temperature of our Sun cannot sustain Earth-like biospheres because they do not provide enough energy in the correct wavelength range. Oxygenic photosynthesis would still be possible, but such planets could not sustain a rich biosphere.” Red dwarfs—where many exoplanets have been discovered—have only a third the Sun’s temperature; stars that are brighter and hotter than the Sun have lifespans too short for life to have a chance to evolve. In other words, the Sun is in a very narrow sweet spot. [Universe Today]
How Mars Landings Became More Accurate
This Scientific American article looks at how landings on Mars have gotten more and more precise, shrinking the “landing ellipse” from 300 km × 100 km (Viking) to 7.7 km × 6.6 km (Perseverance), which enables landings in places other than wide undifferentiated plains. Some locales will be still be off-limits for some time: “For instance, scientists cannot propose landing on high-altitude features such as Olympus Mons because the atmosphere overhead is too tenuous to sufficiently slow down a spacecraft. Regions with very rough terrain or steep slopes are also off-limits, even with [Terrain Relative Navigation]. Furthermore, features such as polar ice caps, canyons, lava tubes and sand dunes offer poor prospects for wheeled rovers and would require alternate forms of mobility.”
How Mission Control’s Giant Displays Worked
In a 19-minute YouTube video, Fran Blanche explains how those big screens at Mission Control worked during the Apollo era. Stop and think about it: they were displaying information in ways that computers wouldn’t be able to do for decades. The displays were produced mechanically, by multiple projectors using glass slides to project images on the screen. The projectors could move spaceship icons across the screen like a graphical sprite, or use plotters to scratch a flight path across a slide to represent a flight path, using telemetry data processed in real time by mainframe computers. [Boing Boing]
A class-action antitrust lawsuit has been filed against telescope companies Celestron and Sky-Watcher, alleging price-fixing by their parent company, Synta, with its ostensible competitor, Ningbo Sunny, which owns Meade. Together Synta and Ningbo Sunny sell 80 percent of all telescopes in the United States, and the suit alleges that the companies agreed to avoid competing with each other, leaving one or the other company alone in a given market segment; see the court filing. None of the claims has been proven in court. Meade has already lost a lawsuit alleging price fixing and collusion brought by competitor Orion Telescopes, in which Orion was awarded more than $50 million in damages; Meade filed for bankruptcy. This new lawsuit draws on court documents from the Orion case.
Star Maps Reviewed
New book review! I review the third edition of Nick Kanas’s Star Maps: History, Artistry, and Cartography (Springer Praxis, 2019) in the March 2020 issue of Calafia, the journal of the California Map Society. The issue is now available for download (PDF), as are earlier issues of Calafia.
Update: The review is now available at The Map Room.
Amazon (Canada, UK) | Apple Books | Bookshop
The Stellina Smart Telescope
DP Review looks at the Stellina smart telescope, an all-in-one “observation station” that serves as telescope (an 80mm ƒ/5 apo refractor), digital camera and self-aligning mount. No eyepieces, just a camera, which can stack multiple exposures to achieve something better than a small scope on a small mount could otherwise achieve. All of these things were available when I was messing around with telescopes a decade or so ago, but not in a single, integrated unit. It took work to achieve results like this; now it takes … $4,000. Ow.
Further Reading on the Apollo Program
We marked the 50th anniversary of Apollo 11 last week, which means that the next step is to put all our moon-landing related nostalgia away until the next milestone anniversary, or until another of the remaining Apollo astronauts dies.1
If, on the other hand, all this attention has piqued your interest in the moon landings, the Apollo program, and the history of crewed spaceflight generally speaking, I have some suggestions as to what you should watch and read next. There are, of course, plenty of books and documentaries on this subject, but these will give you a general overview, with increasing levels of detail.
‘Colder Than Mars’
I have a bone to pick with news stories that declare, hyperbolically, whenever a location is in the midst of a deep freeze, that it’s “colder than Mars”—stories like this one from CTV News or this one from The Atlantic.
What exactly do they mean by “colder than Mars”? Mars is a planet—one that, like Earth, has an atmosphere, albeit thin, and weather and seasons. Mars can get as cold as –143°C (–226°F) and as warm as 35°C (95°F) in spots. Mars’s mean temperature is
It turns out that what reporters really mean is the current temperature at Gale Crater, as measured by the Rover Environmental Monitoring Station on the Curiosity rover. It also turns out that there’s a handy widget that gives the current conditions as measured by REMS. As I write this, the air temperature on Mars is –19°C and the ground temperature is –6°C (the difference is because the air is so thin).
Since it’s –19°C right now where I live, yes, Mars—or at least Gale Crater, which is not the same thing (again: apples to oranges)—is just as cold. But temperatures as high as 20°C (68°F) and as low as –127°C (–197°F) have been recorded at Gale Crater. It’s no trick for a Martian summer to be warmer than a Canadian winter, but even the daytime highs of a Martian winter can be warmer than a Canadian winter. Because the air is so thin, the Martian surface heats quickly when it’s sunny, and the temperature can swing as much as 100 degrees.2
I know that hyperbole is an essential part of talking about how goddamn cold it is out there (see also: using wind chill instead of temperature), but honestly, Mars isn’t a useful point of reference.
Photographing the Eclipse
So I mentioned that I might try to get a photo of the solar eclipse, weather permitting? In the end, weather permitted — in fact, everything that could have prevented us from observing or photographing the eclipse failed to do so: clouds were intermittent until after the maximum, the tall trees around our house didn’t block our view, and we were even able to find all the gear we needed in time (some hadn’t been unpacked yet).
I used my usual method for photographing the sun: a digital SLR connected to my 5-inch Schmidt-Cassegrain telescope at prime focus, using a visual solar filter. It turned out well: despite the heat (atmospheric shimmer, you see), the filter (Mylar) and the need to focus manually, I managed more than a few clear shots. Above is a shot from the eclipse’s maximum extent (it was a partial eclipse here). I’ve uploaded a few other photos here.
You know, I think this is the first time I’ve done any solar observing or photography in more than five years. I’m glad I found an excuse to do it again.