Astronomer

The Measure of All Things: How Two French Astronomers Nearly Lost Their Lives Revolutionizing the World with the Invention of the Meter

“The fundamental fallacy of utopianism is to assume that everyone wants to live in the same utopia.”

The Measure of All Things: How Two French Astronomers Nearly Lost Their Lives Revolutionizing the World with the Invention of the Meter

In her memoir, the trailblazing astronomer Caroline Herschel recounted frequently having to “measure the ground with poles” when she first began making astronomical observations in the 1780s. It seems odd that something as grand and lofty as studying the heavens would necessitate something this humble and earthbound, but this seemingly mundane task is important for two reasons — it reminds us that astronomers were the original measurers of everything we know, but it also raises the question of what the ground was measured in. For it wasn’t until a generation later that the measures of the world were standardized, thanks to the French astronomers Pierre Méchain and Jean Baptiste Joseph Delambre, who set out to unite humanity by creating a single measure: the meter, arguably the most impactful mathematical concept since the invention of zero, central to everything from the speed of light and our basic understanding of the universe to the daily practicalities of shoe sizes, doorframe dimensions, and driving speed limits. Over and over during their seven-year quest for peace through mathematical perfection, they stumbled and fell and got back up, nearly losing their heads to the guillotine on multiple occasions as they toiled to create an equalizing measurement that would “encompass nothing that was arbitrary, nor to the particular advantage of any people on the planet.”

Jean Baptiste Joseph Delambre and Pierre Méchain

Historian Ken Alder tells the story of Delambre and Méchain’s ambitious, improbable, and heroic feat in The Measure of All Things: The Seven-Year Odyssey and Hidden Error That Transformed the World (public library). He casts the stakes:

In June 1792 — in the dying days of the French monarchy, as the world began to revolve around a new promise of Revolutionary equality — two astronomers set out in opposite directions on an extraordinary quest. The erudite and cosmopolitan Jean-Baptiste-Joseph Delambre made his way north from Paris, while the cautious and scrupulous Pierre-François-André Méchain made his way south. Each man left the capital in a customized carriage stocked with the most advanced scientific instruments of the day and accompanied by a skilled assistant. Their mission was to measure the world, or at least that piece of the meridian arc which ran from Dunkerque through Paris to Barcelona. Their hope was that all the world’s peoples would henceforth use the globe as their common standard of measure. Their task was to establish this new measure — “the meter” — as one ten-millionth…

Astronomers detect oldest known stardust in distant galaxy

illustration of galaxy dust
DISTANT DUST Observations from an array of telescopes in Chile show that a distant, young galaxy (illustrated above) is filled with dust probably produced by the first supernova explosions in the universe.

Astronomers may have spotted some of the earliest stardust ever created in the cosmos.

Astrophysicist Nicolas Laporte of University College London and colleagues detected the dust in a galaxy seen as it was when the universe was only 600 million years old. “We are probably seeing the first stardust of the universe,” Laporte says. The observations, published online March 8 in the Astrophysical Journal Letters, could help astronomers learn more about an early period known as cosmic reionization, when ultraviolet radiation stripped electrons from hydrogen atoms.

“Dust is ubiquitous in nearby and more distant galaxies, but has, until recently, been very difficult to detect in the very early universe,” says University of Edinburgh astrophysicist Michal Michalowski, who was not involved in the study. “This paper presents the most distant galaxy for which dust has been detected.”

The galaxy, called A2744_YD4, lies behind a galaxy cluster called Abell 2744. That cluster acts as a gravitational lens, magnifying and brightening the distant galaxy’s light by about a factor of two. Laporte and colleagues observed the galaxy with ALMA, the Atacama Large Millimeter/submillimeter Array in Chile, which revealed the dust.

ALMA observations reveal that the galaxy A2744_YD4 (inset) is rich…

Astronomers Find Seven ‘Earth-Like’ Planets Orbiting a Cool Star

Astronomers say they’ve discovered seven Earth-sized planets in tight orbit around a cool, dim star about 39 light-years from us—and all seven are located in the habitable zone that could potentially host life. This is the first time a planetary system oriented to this kind of star has been detected—and its discovery holds the potential to lead us to a lot more exoplanets. An international team of researchers reported their findings in a letter published today in the journal Nature.

“It’s the first time we have seven planets in this temperate zone … that can be called terrestrial,” lead author Michaël Gillon, of Belgium’s Université de Liège, said in a press briefing. “So many is really, really surprising.”

TRAPPIST-1 is an ultracool dwarf star that’s 1/80th the brightness of the Sun and similar in size to Jupiter. All seven planets in its system are within 20 percent of the size and mass of Earth, and their density measurements indicate they’re likely of rocky composition. They’re clutched by TRAPPIST-1 in tight orbits—all would fit well within the orbit of Mercury. But unlike in our solar system, where such closeness to a hot star renders life impossible, the TRAPPIST-1 planetary system, with its cool celestial heart, could potentially host liquid water and organic molecules.

The first three planets were spotted in early 2016 by some of the same researchers involved in the current findings, including Gillon. As the planets cross in front of the star during their orbits, they cause the star, which emits light in the infrared, to briefly dim. Such transits, or eclipses, provide a common way for astronomers to detect exoplanets.

Using telescopes in Chile, South Africa, Spain, the UK, and Morocco, the researchers followed up on these transit signals multiple times in 2016, most notably in late September with a 20-day, nearly continuous monitoring of the star using the Spitzer Space Telescope, currently located about 145 million miles from us in an Earth-trailing orbit around the Sun. By moving our view off the Earth, researchers were able to detect 34 separate transits. This turned out to be the result of seven planets—six in near-resonant orbit—crossing in front of their home star. (The transit of the seventh was detected only once, so the orbit of this planet, known as TRAPPIST-h, hasn’t been determined yet.)

The planets have relatively narrow surface temperature fluctuations—about 100 degrees—despite their proximity to their home star. (Compare that to Mercury, which has temperature variations of nearly 1200F.) The researchers write that three of the planets—E, F, and G—“could harbor water oceans on their surfaces,…