After starting the mirror alignment with Webb’s first detection of starlight in the Near-Infrared Camera (NIRCam), the telescope team is hard at work on the next steps for commissioning the telescope. To make more progress, the team needs to use another instrument, the Fine Guidance Sensor, to lock onto a guide star and keep the telescope pointed to high <span class="glossaryLink" aria-describedby="tt" data-cmtooltip="
” data-gt-translate-attributes=”["attribute":"data-cmtooltip", "format":"html"]”>accuracy. We have asked René Doyon and Nathalie Ouellette of the Université de Montréal to explain how Webb uses its Canadian instrument in this process.
“After being powered on January 28, 2022, and undergoing successful aliveness and functional tests, Webb’s Fine Guidance Sensor (FGS) has now successfully performed its very first guiding operation! Together with the Near-Infrared Imager and Slitless Spectrograph (NIRISS), the FGS is one of Canada’s contributions to the mission.
“To ensure Webb stays locked on its celestial targets, the FGS measures the exact position of a guide star in its field of view 16 times per second and sends adjustments to the telescope’s fine steering mirror about three times per second. In addition to its speed, the FGS also needs to be incredibly precise. The degree of precision with which it can detect changes in the pointing to a celestial object is the equivalent of a person in New York City being able to see the eye motion of someone blinking at the Canadian border 500 kilometers (311 miles) away!
“Webb’s 18 primary mirror segments are not yet aligned, so each star appears as 18 duplicate images. On February 13, FGS successfully locked onto and tracked one of these star images for the first time. The FGS team was thrilled to see this ‘closed loop guiding’ working! From now on, most of the alignment process of the telescope mirrors will take place with FGS guiding, while NIRCam images provide the diagnostic information for mirror adjustments.”
– René Doyon, principal investigator for FGS/NIRISS, Université de Montréal; and Nathalie Ouellette, Webb outreach scientist, Université de Montréal
- Jonathan Gardner, Webb deputy senior project scientist, <span class="glossaryLink" aria-describedby="tt" data-cmtooltip="
NASAEstablished in 1958, the National Aeronautics and Space Administration (NASA) is an independent agency of the United States Federal Government that succeeded the National Advisory Committee for Aeronautics (NACA). It is responsible for the civilian space program, as well as aeronautics and aerospace research. It's vision is "To discover and expand knowledge for the benefit of humanity."
” data-gt-translate-attributes=”["attribute":"data-cmtooltip", "format":"html"]”>NASA’s Goddard Space Flight Center
- And Alexandra Lockwood, project scientist for Webb science communications, Space Telescope Science Institute
Peek-a-Boo Moon: Astronaut on Space Station Captures Spectacular Photos of the Lunar Eclipse – SciTechDaily
On the evening of May 15, 2022, Earth passed between the Sun and the Moon blocking sunlight and casting a shadow on the lunar surface. ESA astronaut Samantha Cristoforetti witnessed this lunar eclipse from the International Space Station and captured it in a series of photographs.
During a lunar eclipse, Earth’s atmosphere scatters sunlight. The blue light from the Sun scatters away, and longer-wavelength red, orange, and yellow light pass through, turning our Moon red.
In these images, the Moon appears to play hide and seek with one of the International Space Station’s solar panels:
Samantha is living and working aboard the Space Station for her second mission, ‘Minerva’. Learn more about Samantha and the Minerva mission.
African scientists and technology could drive future black hole discoveries – The Conversation Africa
Astronomers have revealed the first image of the black hole at the centre of our galaxy, the Milky Way. The image was produced by the Event Horizon Telescope (EHT) Collaboration, an international team made up of over 300 scientists on five continents – including Africa.
Black holes were predicted by Albert Einstein’s General Theory of Relativity over a century ago. They are regions of space so dense that nothing, including light, can escape. Their boundary is known as the event horizon, which marks the point of no return. That’s just one of the reasons these objects are hidden from our eyes. The other is that they are exceedingly small, when placed in their cosmic context. If our Milky Way galaxy were the size of a soccer field, its black hole event horizon would be a million times smaller than a pin prick at centrefield.
How, then, can one photograph them? Our team did so by capturing light from the hot swirling gas in the immediate vicinity of the black hole. This light, with a wavelength of 1 millimetre, is recorded by a global network of antennas that form a single, Earth-sized virtual telescope.
The light looks rather like a ring, a characteristic signature that is the direct consequence of two key processes. First, the black hole is so dense that it bends the path of light near it. Second, it captures light that strays too close to the event horizon. The combined effect produces a so-called black hole shadow – a brightened ring surrounding a distinct deficit of light centred on the black hole. In the case of our Milky Way black hole, this ring has the apparent size of a doughnut on the moon, requiring an extraordinary engineering effort to bring it into focus.
The unveiling of an image of our black hole, Sagittarius A*, is not just a massive moment for science. It could also be an important catalyst for diversifying African astrophysics research using existing strengths. We were the only two of more than 300 EHT team members based on the African continent. The continent doesn’t host any EHT telescopes – we were brought on board because of expertise we’ve developed in preparation for the world’s largest radio telescope, the Square Kilometre Array (SKA), to be co-hosted by South Africa and Australia.
Why the image is important
This is not the first time a black hole image has captured people’s attention. We were also members of the team that captured the first ever image of a black hole in 2019 (this one is at the centre of a different galaxy, Messier 87, which is 55 million light years away). It has been estimated that more than 4.5 billion people saw that image. Sagittarius A* has also dominated headlines and captured people’s imaginations.
But there’s more to this result than just an incredible image. A plethora of rich scientific results has been described in ten publications by the team. Here are three of our primary highlights.
First, the image is a remarkable validation of Einstein’s General Theory of Relativity. The EHT has now imaged two black holes with masses that differ by a factor of over 1000. Despite the dramatic difference in mass, the measured size and shape are consistent with theoretical predictions.
Second, we have now imaged black holes with very different environments. A wealth of prior research over the past two or three decades shows strong empirical evidence that galaxies and their black holes co-evolve over cosmic time, despite their completely disparate sizes. By zooming into the event horizon of black holes in giant galaxies like M87, as well as more typical galaxies like our own Milky Way, we learn more about how this seemingly implausible relationship between the black hole and its host galaxy plays out.
Third, the image provides us with new insights on the central black hole in our own galactic home. It is the nearest such beast to Earth, so it provides a unique laboratory to understand this interplay – not unlike scrutinising a tree in your own garden to better understand the forests on the distant horizon.
Southern Africa’s geographic advantage
We are proud to be part of the team that produced the first black hole images. In future, we believe South Africa, and the African continent more broadly (including a joint Dutch-Namibian initiative), could play a critical role in making the first black hole movies.
As has been the case with the country’s key role in paleoanthropology, there are contributions to global astronomy that can only be made from South African soil. Sagittarius A* lies in the southern sky, passing directly above South Africa. That is a major reason why this image of the Milky Way’s centre, taken by the MeerKAT (a precursor to the SKA) is the best there is.
South Africa also has well-established infrastructure at its astronomical sites, which are protected by legislation. And it has world-class engineers at the forefront of their craft. This makes for low-cost, high-performance telescopes delivered on time and to budget.
New technology is also on our side: a cutting-edge simultaneous multi-frequency receiver design, pioneered by our Korean colleagues, means that EHT sites no longer need to be the most pristine, high-altitude locations on Earth.
All the elements are in place for a dramatic increase in the number of young Africans who participate in this new era of black hole imaging and precision tests of gravity. In the coming years, we hope to be writing about findings that couldn’t have been made without technology on South African soil, as well as African scientists leading high-impact, high-visibility EHT science in synergy with our multi-wavelength astronomy and high-energy astrophysics programmes.
150,000-Year-Old Human Tooth Is Rare Evidence of the Extinct Denisovans – Gizmodo
Paleontologists in Laos have uncovered an ancient molar that likely belonged to a young Denisovan girl. The discovery is a big deal, as the Laotian cave in which the molar was found is now one of only three spots known to host these enigmatic humans.
In addition to Siberia and the Tibetan Plateau, we can now add Laos to the achingly short list of places that have yielded fossils of an elusive human species known as the Denisovans. A team of paleontologists found the suspected Denisovan molar at the Tam Ngu Hao 2 cave in the Annamite Mountains of Laos. The molar dates to the middle Pleistocene, and it’s the first Denisovan fossil ever to be found in southeast Asia. A paper detailing this discovery is published today in Nature Communications.
Laura Shackelford, an anthropologist from the University of Illinois at Urbana-Champaign and a co-author of the new study, was excited to learn that Denisovans, like their Neanderthal cousins, inhabited a variety of environments, some of them extreme.
“Although we only have a few fossils representing the Denisovans, this new fossil from Laos demonstrates that much like modern humans, Denisovans were widespread and they were highly adaptable,” Shackelford explained in an email. “They lived in the cold arctic temperatures of Siberia, in the cold, [oxygen poor] environment of the Tibetan Plateau, and now we know they were also living in the tropics of southeast Asia.”
What’s more, the new discovery “further attests” that southeast Asia was “a hotspot of diversity for the genus Homo” during the middle to late Pleistocene, as the scientists write in their study. So in addition to Denisovans, this part of the world was once home to H. erectus, Neanderthals, H. floresiensis, H. luzonensis, and H. sapiens.
That a Denisovan fossil was found in Laos is not a huge surprise. Traces of Denisovan DNA have been detected within the genomes of modern southeast Asian and Oceanian populations. The Ayta Magbukun—a Philippine ethnic group—have retained approximately 5% of their Denisovan ancestry, the highest of any human group in the world. Denisovans branched off from Neanderthals at some point between 200,000 and 390,000 years ago. They eventually went extinct, but not before interbreeding with modern humans. The Laotian molar is just the 10th Denisovan fossil to be found and the first outside of Siberia and Tibet.
The Annamite Mountains contain an abundance of limestone caves. Each year, Shackelford and her colleagues dispatch geologists to the area in hopes of finding spots worthy of further paleontological investigation.
“In 2018, our geologists spent the morning surveying and returned to the site before lunch with their pockets full of sediment samples that they had collected from a potential new site, what we now know as Tam Ngu Hao 2 or Cobra Cave,” Shackelford told me. “In these first samples, among fragments of fossil animal teeth, we found the tooth.”
By dating the sediment in which the molar was found, the team aged the fossil to between 164,000 and 131,000 years old. A protein analysis of the tooth’s enamel identified the fossil as belonging to a member of the Homo genus, but this test couldn’t pin down the exact species.
“We do know that this is the tooth of a girl who died when she was between about 4 to 8 years old,” said Shackelford. “Since this tooth comes from a child, we are currently doing additional analyses of tooth growth and development.”
Clément Zanolli, an expert on the evolution of human teeth and a co-author of the new study, said the identification of the Denisovan molar arose from multiple lines of morphological evidence. The Laotian molar, he told me, bears a resemblance to teeth found on the partial Denisovan mandible from Tibet, including large tooth dimensions and various distinguishing features that separate it from other Homo species known to inhabit southeast Asia, including Neanderthals and modern humans.
“Among the human groups previously cited, the molar from Laos is closest to Neanderthals, and we know from paleogenetics that Denisovans were a sister group of Neanderthals, meaning that they were closely related and shared morphological features,” Zanolli, who works at the University of Bordeaux, explained in an email. “For these reasons, the most parsimonious hypothesis is that the tooth that we found in Laos belongs to a Denisovan individual.”
It’s not impossible that the molar belonged to a Neanderthal, but if that’s the case, that “would make it the south-eastern-most Neanderthal fossil ever discovered,” according to the paper.
“We are confident it is Denisovan,” Fabrice Demeter, a paleoanthropologist at the University of Copenhagen and a co-author of the study, told me in an email. But to “further confirm our results if needed, genetic analyses would be useful,” he said. Unfortunately, however, “DNA tends to fragment more quickly and intensely in tropical environments,” and it’s for this reason that “no ancient DNA from any Pleistocene human has been sequenced so far,” he added.
The new fossil is important because it affirms something already hinted at by the genetic data—that Denisovans once inhabited a wide area of southeast Asia. What’s more, it “confirms that Denisovans were present in this region and could have met with Late Pleistocene modern humans,” according to Zanolli. And lastly, it shows that Denisovans could live in both cold, high-altitude environments and the tropical forests of southeast Asia.
The Denisovans appear to have been an adaptable group. But that just makes their sudden disappearance some 50,000 years ago all the more mysterious.
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