Black holes and the Milky Way’s darkest secret
Illustration: ©Johan Jarnestad/The Royal Swedish Academy of Sciences
Three Laureates share this year’s Nobel Prize in Physics for their discoveries about one of the most exotic phenomena in the universe, the black hole. Roger Penrose showed that the general theory of relativity leads to the formation of black holes. Reinhard Genzel and Andrea Ghez discovered that an invisible and extremely heavy object governs the orbits of stars at the center of our galaxy. A supermassive black hole is the only currently known explanation.
Roger Penrose used ingenious mathematical methods in his proof that black holes are a direct consequence of Albert Einstein’s general theory of relativity. Einstein did not himself believe that black holes really exist, these super-heavyweight monsters that capture everything that enters them. Nothing can escape, not even light.
In January 1965, ten years after Einstein’s death, Roger Penrose proved that black holes really can form and described them in detail; at their heart, black holes hide a singularity in which all the known laws of nature cease. His ground-breaking article is still regarded as the most important contribution to the general theory of relativity since Einstein.
Reinhard Genzel and Andrea Ghez each lead a group of astronomers that, since the early 1990s, has focused on a region called Sagittarius A* at the center of our galaxy. The orbits of the brightest stars closest to the middle of the Milky Way have been mapped with increasing precision. The measurements of these two groups agree, with both finding an extremely heavy, invisible object that pulls on the jumble of stars, causing them to rush around at dizzying speeds. Around four million solar masses are packed together in a region no larger than our solar system.
Using the world’s largest telescopes, Genzel and Ghez developed methods to see through the huge clouds of interstellar gas and dust to the center of the Milky Way. Stretching the limits of technology, they refined new techniques to compensate for distortions caused by the Earth’s atmosphere, building unique instruments and committing themselves to long-term research. Their pioneering work has given us the most convincing evidence yet of a supermassive black hole at the center of the Milky Way.
“The discoveries of this year’s Laureates have broken new ground in the study of compact and supermassive objects. But these exotic objects still pose many questions that beg for answers and motivate future research. Not only questions about their inner structure, but also questions about how to test our theory of gravity under the extreme conditions in the immediate vicinity of a black hole”, says David Haviland, chair of the Nobel Committee for Physics.
This year’s Nobel Prize in Physics winners:
Roger Penrose, born 1931 in Colchester, UK. Ph.D. 1957 from University of Cambridge, UK. Professor at University of Oxford, UK.
Reinhard Genzel, born 1952 in Bad Homburg vor der Höhe, Germany. Ph.D. 1978 from University of Bonn, Germany. Director at Max Planck Institute for Extraterrestrial Physics, Garching, Germany and Professor at University of California, Berkeley, USA.
Andrea Ghez, born 1965 in City of New York, USA. Ph.D. 1992 from California Institute of Technology, Pasadena, USA. Professor at University of California, Los Angeles, USA.
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Rare 'blue moon' to appear on Halloween this year – The Tri-City News
The year 2020 has brought many surprises and this year’s Halloween is no different.
A rare “blue full moon” will be appearing on Halloween night this year.
While the moon will not look blue, the term “blue moon” is given when two full moons appear in a single month.
A full moon on Halloween occurs roughly once every 19 years – a pattern known as the Metonic Cycle.
The next illuminated Halloween full moon, says astronomers, after 2020 will be in the 2039, 2058, 2077 and 2096.
NASA’s OSIRIS-REx grabs rocks from asteroid in historic mission – Al Jazeera English
A NASA spacecraft touched down on the rugged surface of the Bennu asteroid on Tuesday, grabbing a sample of rocks dating back to the birth of the solar system to bring home.
It was a first for the United States – only Japan has previously secured asteroid samples.
The so-called “Touch-And-Go” manoeuvre was managed by Lockheed Martin Space in Denver, Colorado, where at 6.12pm (22:12 GMT) on Tuesday an announcer said: “Touchdown declared. Sampling is in progress,” and scientists erupted in celebration.
Seconds later, the Lockheed mission operator Estelle Church confirmed the spacecraft had eased away from the space rock after making contact, announcing: “Sample collection is complete and the back-away burn has executed.”
The historic mission was 12 years in the making and rested on a critical 16-second period where the minivan-sized OSIRIS-REx spacecraft extended its 11-foot (3.35-metre) robotic arm towards a flat patch of gravel near Bennu’s north pole and plucked the sample of rocks – NASA’s first handful of pristine asteroid rocks.
The probe will send back images of the sample collection on Wednesday and throughout the week so scientists can examine how much material was retrieved and determine whether the probe will need to make another collection attempt.
Scientists want at least 2 ounces (60 grams) and, ideally, closer to 4 pounds (2 kilogrammes) of Bennu’s black, crumbly, carbon-rich material – thought to contain the building blocks of the solar system. The asteroid is located more than 200 million miles (321.9 million kms) from Earth.
NASA’s science mission chief, Thomas Zurbuchen, likened Bennu to the Rosetta Stone: “Something that’s out there and tells the history of our entire Earth, of the solar system, during the last billions of years.”
If a successful collection is confirmed, the spacecraft will begin its journey back towards Earth, arriving in 2023.
“Everything went just exactly perfect,” Dante Lauretta, OSIRIS-REx principal investigator from the University of Arizona, Tucson, said on a NASA live feed from Lockheed’s mission support building. “We have overcome the amazing challenges that this asteroid has thrown at us, and the spacecraft appears to have operated flawlessly.”
The robotic arm’s collection device, shaped like an oversized shower head, is designed to release pressurised gas to kick up debris.
The spacecraft launched in 2016 from Kennedy Space Center for the journey to Bennu. It has been in orbit around the asteroid for nearly two years preparing for the Touch and Go manoeuvre.
Bennu, which is more than 4.5 billion years old, was selected as a target because scientists believe it is a small fragment of what was once a much larger space rock that broke off during a collision between two asteroids early on in the history of the solar system.
“Asteroids are like time capsules floating in space that can provide a fossil record of the birth of our solar system,” Lori Glaze, NASA’s director of Planetary Science, told Al Jazeera. “They can provide valuable information about how planets, like our own, came to be.”
Thanks to data collected from orbit, the NASA team has determined two key discoveries: first, that between 5 and 10 percent of Bennu’s mass is water, and second, that its surface is littered with carbon-rich molecules. Atomic-level analysis of samples from Bennu could help scientists better understand what role asteroids played in bringing water to the Earth and seeding it with the prebiotic material that provided the building blocks for life.
Studying that material could also help scientists discover whether life exists elsewhere in the solar system, as well.
“If this kind of chemistry is happening in the early solar system, it probably happened in other solar systems as well,” Lauretta, OSIRIS-Rex’s principal investigator, told Al Jazeera in an interview ahead of Tuesday’s breakthrough. “It helps us assess the likelihood of the origin of life occurring throughout the galaxy and, ultimately, throughout the universe.”
Japan expects samples from its second asteroid mission – in the milligramMEs at most – to land in the Australian desert in December.
New Research Provides Comprehensive Reconstruction of End-Permian Mass Extinction | Paleontology – Sci-News.com
The end-Permian mass extinction, also known as the Permian-Triassic extinction event and the Great Dying, is the largest mass extinction event in Earth’s history that peaked about 252.3 million years ago. The catastrophe killed off nearly 96% of all marine species and 70% of terrestrial vertebrate species on the planet over the course of thousands of years. Massive eruptions in a volcanic system called the Siberian Traps are thought to have played an important role, but the causational trigger and its feedbacks are yet to be fully understood. Now, a research team led by Dr. Hana Jurikova from the GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel and the Helmholtz Zentrum Potsdam has assembled a consistent biogeochemical reconstruction of the mechanisms that resulted in the end-Permian extinction.
Dr. Jurikova and her colleagues studied isotopes of the element boron in the calcareous shells of fossil brachiopods and determined the rate of ocean acidification over the Permian-Triassic boundary.
“These are clam-like organisms that have existed on Earth for more than 500 million years,” Dr. Jurikova said.
“We were able to use well-preserved brachiopod fossils from the Southern Alps for our analyses.”
“These shells were deposited at the bottom of the shallow shelf seas of the Tethys Ocean 252 million years ago and recorded the environmental conditions shortly before and at the beginning of extinction.”
Because the ocean pH and atmospheric carbon dioxide are closely coupled, the researchers were able to reconstruct changes in atmospheric carbon dioxide at the onset of the extinction from boron and carbon isotopes.
They then used an innovative geochemical model to study the impact of the carbon dioxide injection on the environment.
“With this technique, we can not only reconstruct the evolution of the atmospheric carbon dioxide concentrations, but also clearly trace it back to volcanic activity,” said co-author Dr. Marcus Gutjahr, a researcher at the GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel.
“The dissolution of methane hydrates, which had been suggested as a potential further cause, is highly unlikely based on our data.”
“Without these new techniques it would be difficult to reconstruct environmental processes more than 250 million years ago in the same level of detail as we have done now,” said co-author Professor Anton Eisenhauer, also from the GEOMAR Helmholtz-Zentrum für Ozeanforschung Kiel.
The team’s findings showed that volcanic eruptions in Siberian Traps released immense amounts of carbon dioxide into the atmosphere.
This release lasted several millennia and led to a strong greenhouse effect on the late Permian world, causing extreme warming and acidification of the ocean.
Dramatic changes in chemical weathering on land altered productivity and nutrient cycling in the ocean, and ultimately led to vast de-oxygenation of the ocean.
The resulting multiple environmental stressors combined to wipe out a wide variety of animal and plant groups.
“We are dealing with a cascading catastrophe in which the rise of carbon dioxide in the atmosphere set off a chain of events that successively extinguished almost all life in the seas,” Dr. Jurikova said.
“Ancient volcanic eruptions of this kind are not directly comparable to anthropogenic carbon emissions, and in fact all modern fossil fuel reserves are far too insufficient to release as much carbon dioxide over hundreds of years, let alone thousands of years as was released 252 million years ago.”
“But it is astonishing that humanity’s carbon dioxide emission rate is currently 14 times higher than the annual emission rate at the time that marked the greatest biological catastrophe in Earth’s history.”
The study was published in the journal Nature Geoscience.
H. Jurikova et al. Permian-Triassic mass extinction pulses driven by major marine carbon cycle perturbations. Nat. Geosci, published online October 19, 2020; doi: 10.1038/s41561-020-00646-4
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