Cecilia Payne Gaposchkin showed stars were primarily made of hydrogen and helium.Photograph: Astronomical Society of the Pacific, courtesy AIP Emilio Segre Visual Archives
Eighty-five years ago, several dozen eminent astronomers posed for a photograph outside the newly constructed McDonald Observatory near Fort Davis in Texas. All were men – with one exception. Half-concealed by a man in front of her, the face of a solitary woman can just be made out in the grainy black and white image.
This is Cecilia Payne-Gaposchkin, whose impact on our understanding of the cosmos was profound. She showed stars were primarily made of hydrogen and helium, contradicting the scientific orthodoxy of the 1920s, which held that they were made of an array of elements. Her claims were suppressed and her work obscured, like her image on the McDonald Observatory photograph.
“You can see what she was up against from that picture taken in 1939,” said Meg Weston-Smith, a family friend of the Gaposhkins. “Astronomy, like so much else, was a man’s world.”
In the end, the ideas of Payne-Gaposchkin – who was born in Britain and married a Russian scientist, Sergei Gaposchkin – prevailed, though not without considerable opposition from male colleagues, as revealed in a new play, The Lightest Element, by Stella Feehily, opening this week at the Hampstead Theatre.
“Essentially she was up against a men’s club,” says Feehilly. “Astronomers, virtually all of them male, all agreed that the stars and the universe must be made of the same elements as we find on Earth. Being a woman and outside the group, she was free to be more radical in her thinking. She was right and they were wrong. The cosmos is 98% hydrogen and helium.”
Nor was Payne-Gaposchkin alone in being initially disparaged for being a female astronomer and only now being recognised for her brilliance. Annie Maunder and Alice Everett, who in the 19th century were among the first women to earn a living in astronomy, recently had asteroids named after them.
In addition, the biggest camera in the world – to be unveiled in Chile and used to image the entire visible sky every three to four nights beginning next year – has been named the Vera C Rubin Observatory. Rubin, who was American, played a critical role in revealing that our universe appears to be permeated with mysterious, undetectable particles. This is dark matter and it has played a key role in the evolution of the universe.
Like all female students at Cambridge until 1948, Maunder and Everett were not awarded degrees despite passing their examinations with honours; during her education and career, Rubin suffered widespread discrimination. Even after she acquired fame, she was blocked from using the great Palomar Observatory to continue her groundbreaking research because it had no bathrooms for women. Rubin’s “solution” was to tape a piece of paper in the shape of a skirt on top of the men’s symbol on the bathroom door.
“Rubin’s name regularly topped lists of potential Nobel winners, but to the Nobel committee, she was invisible matter,” notes Shohini Ghose, in her book Her Space, Her Time: How Trailblazing women scientists decoded the hidden Universe.
Rubin received some compensation when she was eventually awarded the Gold Medal by the Royal Astronomical Society in 1996. However, the only other woman to receive the award before her was Caroline Herschel – in 1828. As Ghose puts it, the 168-year gap in recognising female astronomers was “a ridiculously long stretch”.
Since the turn of this century, more women have been following careers in astronomy, although the profession still remains predominantly male, says Sue Bowler, journals editor of the Royal Astronomical Society. “‘When you go to meetings about related subjects such as atmospheric physics you find the audience is 50-50 male-female. But at some astronomy meetings, it can be as low as 10% women. I don’t really know why that is.”
Other signs suggest some movement towards recognising female astronomers. In 2020, the American scientist Andrea Ghez became the first female astronomer to win a Nobel prize for physics for her work on the discovery of a supermassive black hole at the centre of our galaxy. Given that only four other women have ever won the physics Nobel, this could scarcely be described as trend-setting.
By contrast, there is a lengthy list of female astronomers who campaigners feel should have won Nobels but were denied them. Examples include Vera Rubin as well as Jocelyn Bell Burnell, who played a key role in identifying the first pulsar stars but who was denied a Nobel, which went instead to her Cambridge colleagues Antony Hewish and Martin Ryle. The decision still causes controversy.
“That was the first Nobel prize ever to be awarded for astronomical observations and Bell Burnell should have got a share, I have no doubt about that,” says Feehily. “Having done my research on this, what surprises me is not that things have changed but how, in so many ways, they have not changed enough.
“In the end, Payne-Gaposchkin prevailed. We now know, thanks to her, that most of the matter in the universe is hydrogen and helium. She was the first person to prove that – though it took a long time before her work was recognised for its remarkable quality. She still had to fight to get her due recognition and it is important to remember the battle she had to endure.”
Ashley Strickland, CNN
Sat 31 August 2024
NASA spacecraft collision may have created a meteor shower that will last for 100 years
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Rocky debris blasted away from the tiny asteroid Dimorphos when NASA’s DART spacecraft intentionally slammed into it in 2022 could create the first human-made meteor shower known as the Dimorphids, new study has found.
The space agency planned the DART, or Double Asteroid Redirection Test, mission to carry out a full-scale assessment of asteroid deflection technology on behalf of planetary defense. NASA wanted to see whether a kinetic impact — such as crashing a spacecraft into an asteroid at 13,645 miles per hour (6.1 kilometers per second) — would be enough to change the motion of a celestial object in space.
Neither Dimorphos or the large parent space rock it orbits, known as Didymos, pose a danger to Earth. Still, the double-asteroid system was a perfect target to test deflection technology because Dimorphos’ size is comparable to asteroids that could threaten our planet.
The last complete image of asteroid moonlet Dimorphos was taken by the DRACO imager on NASA's DART mission at a distance of about 7 miles (12 kilometers) and 2 seconds before impact. - NASA/Johns Hopkins APL
Astronomers have used ground-based telescopes to monitor the impact’s aftermath for nearly two years, and they determined that the DART spacecraft did successfully change the way Dimorphos moves, shifting the moonlet asteroid’s orbital period — or how long it takes to make a single revolution around Didymos — by about 32 to 33 minutes.
But scientists also estimated the intentional collision generated more than 2 million pounds (nearly 1 million kilograms) of rocks and dust — enough to fill about six or seven rail cars. Where exactly in space all of that material will end up has remained an open question.
Now, new research suggests fragments of Dimorphos will arrive in the vicinity of Earth and Mars within one to three decades, with the possibility that some debris could reach the red planet within seven years. Small debris could also reach Earth’s atmosphere within the next 10 years. The Planetary Science Journal has accepted the study for publication.
“This material could produce visible meteors (commonly called shooting stars) as they penetrate the Martian atmosphere,” said lead study author Eloy Peña Asensio, a postdoctoral researcher for the Deep-space Astrodynamics Research and Technology group at Italy’s Polytechnic University of Milan. “Once the first particles reach Mars or Earth, they could continue to arrive intermittently and periodically for at least the next 100 years, which is the duration of our calculations.”
Predicting space debris
The individual pieces are small, ranging from sand grain-type particles to fragments similar in size to smartphones, so none of the debris poses a risk to Earth, Peña Asensio said.
“They would disintegrate in the upper atmosphere through a process known as ablation, caused by friction with the air at hypervelocity,” he said. “There is no possibility of a Dimorphos material reaching Earth’s surface.”
But understanding when the debris could reach Earth is more challenging and depends on estimating the velocity of the fragments.
When the spacecraft crashed into Dimorphos, it wasn’t alone. A small satellite named LICIACube separated from the spacecraft before impact to capture footage of the collision and the debris cloud that formed afterward.
“This crucial data has enabled and continues to enable detailed analysis of the debris produced by the impact,” Peña Asensio said.
The research team used LICIACube data and the supercomputing facilities of the Consortium of University Services of Catalonia to simulate the trajectory of 3 million particles that the impact created. The computer modeling measured different possible pathways and velocities of the particles across the solar system as well as how radiation released by the sun might affect the motion of the particles.
LICIACube shows plumes of debris streaming from the Dimorphos asteroid after NASA's Double Asteroid Redirect Test made impact with it on September 26, 2022. - ASI/NASA/APL
Previous research ahead of the impact had suggested the possibility of Dimorphos’ particles reaching Earth or Mars, Peña Asensio said, but for the new study, the team restricted the simulations to align with post-impact data from LICIACube.
The study’s results confirm that if the debris were ejected from Dimorphos at speeds of 1,118 miles per hour (500 meters per second), some fragments could reach Mars, while other, smaller and faster-moving debris traveling at 3,579 miles per hour (1,600 meters per second) has the potential to reach Earth.
The team said uncertainties remain regarding the nature of the debris but concluded the fastest-moving particles could reach Earth in less than 10 years.
The study authors consider the possibility of the Dimorphids meteor shower reaching Earth unlikely, but they can’t rule it out, Peña Asensio said. And if it did occur, it would be a small, faint meteor shower.
“The resulting meteor shower would be easily identifiable on Earth, as it would not coincide with any known meteor showers,” he said by email. “These meteors would be slow-moving, with peak activity expected in May, and primarily visible from the southern hemisphere, seemingly originating from near the Indus constellation.”
And while the researchers didn’t explore this possibility in their paper, their investigation suggested Dimorphos’ debris could reach other, nearby asteroids.
A visit to the aftermath
Ejected debris was expected from the impact, but the possibility of material reaching Earth or Mars could only be calculated after the collision, said study coauthor Michael Küppers, planetary scientist at the European Space Astronomy Centre.
“Personally, initially I was surprised to see that, although the impact happened close to Earth (at about an 11-million-kilometer distance), it is easier for the impact ejecta (debris) to reach Mars than to reach Earth,” Küppers said by email. “I believe the reason is that Didymos crosses the orbit of Mars, but stays just outside the orbit of Earth.”
Particles can be ejected from near-Earth asteroids, such as Phaethon, which is responsible for the Geminid meteor shower that peaks in mid-December each year. Studying what was released by the DART impact could help predict when such material could reach Earth or Mars, said Patrick Michel, astrophysicist and director of research at the National Centre for Scientific Research in France. Michel was not involved in the study.
Boulders can be seen on Dimorphos' surface just before impact. - NASA/Johns Hopkins APL
“This study tries to quantify this possibility and confirms that it may happen, even if it relies on modeling that has its own uncertainties,” Michel said.
Future observations could help researchers refine mass measurements of the debris and determine how quickly it is moving to calculate the expected meteor activity, Peña Asensio said.
Those observations will be conducted by the Hera mission. The European Space Agency mission is expected to launch in October to observe the aftermath of the DART impact, arriving at the asteroid system near the end of 2026. Together with a pair of CubeSats, the spacecraft will study the composition and mass of Dimorphos and its transformation by the impact. Hera will also determine how much momentum was transferred from the spacecraft to the asteroid.
“Is there an impact crater, or was the impact so large that Dimorphos was globally reshaped?” said Küppers, who is also a project scientist for the Hera mission. “From ground-based data, we have some evidence for the latter. Hera will tell us for sure. Also, we will see if the impact left Dimorphos (tumbling).”
Overall, the mission will enable astronomers to understand the dynamical evolution of debris “produced by an impact in such a complex system of double asteroids,” Michel said.
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