Star orbiting massive black hole lends support to Einstein’s theory
Robie de Guzman • July 26, 2019 • 1130
Observations of light coming from a star zipping in orbit around the humongous black hole at the center of our galaxy have provided fresh evidence backing Albert Einstein’s 1915 theory of general relativity, astronomers said on Thursday (July 25).
Researchers studied a star called S0-2, boasting a mass roughly 10 times larger than the sun, as it travels in an elliptical orbit lasting 16 years around the supermassive black hole called Sagittarius A* residing at the center of the Milky Way 26,000 light years from Earth.
They found that the behavior of the star’s light as it escaped the extreme gravitational pull exerted by the black hole, with 4 million times the sun’s mass, conformed to Einstein’s theory’s predictions. The famed theoretical physicist proposed the theory, considered one of the pillars of science, to explain the laws of gravity and their relation to other natural forces.
While Einstein’s theory held up in the observations of this star, astronomer Andrea Ghez of the University of California, Los Angeles said it may not be able to fully account for what happens in the most exotic possible gravitational environments like those of black holes. These extraordinarily dense celestial entities exert gravitational fields so strong that no matter or light can escape.
The study detected a co-mingling of space and time near the black hole as predicted by Einstein’s theory. Isaac Newton’s 17th century law of universal gravitation could not account for these observations, Ghez said.
At some point a more comprehensive theory of gravity may be required, she said.
The study, relying heavily on data from the Keck Observatory in Hawaii, focused on an effect called gravitational redshift.
Einstein’s theory foresees the wavelength of electromagnetic radiation including light lengthening as it escapes the pull of gravity exerted by a massive celestial body like a black hole.
Photons – particles of light – expend energy to escape but always travel at the speed of light, meaning the energy loss occurs through a change of electromagnetic frequency rather than a slowing of velocity.
This causes a shift to the red end of the electromagnetic spectrum, a gravitational redshift. (REUTERS)
Taiwan braced for Typhoon Bailu on Friday (August 23), prompting cancellations of domestic flights amid warnings of floods and high seas on the island.
Typhoon Bailu, categorised at the weakest typhoon level by Taiwan’s weather bureau, was expected to approach the island’s southeastern coast early on Saturday (August 24), weather officials said.
Bailu was carrying maximum winds of 126 km per hour (78 mph) as it approached Taiwan, the weather bureau said, adding that the storm could gain in strength and become the first typhoon to make landfall on the island in more than two years.
Thousands of people were moved to safety, most of them tourists on islands off the east coast, while dozens of domestic flights and ferry services were cancelled.
After passing over Taiwan, the typhoon is expected to cross the Taiwan Strait and hit the Chinese province of Fujian, forecasters said. (Reuters)
Scientists in Florida have artificially induced reproductive spawning of an endangered Atlantic coral species for the first time in an aquarium setting, a breakthrough they say holds great promise in efforts to restore depleted reefs in the wild.
The achievement, announced this week at the Florida Aquarium in Apollo Beach near Tampa, borrowed from lab techniques developed at the London-based Horniman Museum and Gardens and used previously to induce spawning of 18 species of Pacific coral, officials said.
Scientists plan to use their newly acquired expertise to breed new coral colonies that can one day repopulate the beleaguered Florida reef system, one of the largest in the world and one decimated by climate change, pollution and disease in recent decades.
The newly cultivated corals should make for even stronger populations than existing colonies because each individual will be bred with characteristics that may be better able to withstand damage, Keri O’Neil, senior coral scientist at the Florida Aquarium told Reuters.
Inducing corals to release their eggs and sperm in aquarium tanks involves controlling their artificial settings to mimic their natural ocean habitat over the course of a yearlong reproduction cycle.
That means carefully regulating water temperature changes from summer to winter, and using special lighting to imitate sunrise, sunset and even lunar cycles that serve as biological cues for the coral in preparing to spawn.
Collaboration between the Florida and London facilities on the project began in 2017 as the situation facing Florida’s reefs grew more dire because of the spread of a new coral affliction dubbed Stony Coral Tissue Loss Disease.
Atlantic pillar coral, which grows in colonies resembling finger- or column-like structures, has been particularly susceptible to the disease and is already classified as virtually extinct in the wild because remaining male and female colonies are too scattered to reproduce.
Corals are a type of marine invertebrate animal, typically living in colonies of tiny sac-like polyps that feed by filtering seawater through a set of tentacles surrounding a central mouth opening.
Corals are sensitive to major changes in water temperature, and the Florida Reef Tract, like other major reefs around the world, has been under pressure from climate change for years as the sea grows steadily warmer. (Reuters)
The Brazilian government lacks the resources to fight a record number of wildfires burning in the Amazon rainforest, President Jair Bolsonaro said on Thursday (August 22), weeks after telling donors he did not need their money.
Fires in the Amazon have surged 83% so far this year compared with the same period a year earlier, government figures show, destroying vast swathes of a forest considered a vital bulwark against climate change.
On Wednesday, Bolsonaro said, without supporting evidence, that non-governmental organisations were behind the fires.
Questioned again on Thursday about those comments, he said he could not prove that NGOs, for whom he has cut funding, were lighting the fires but that they were “the most likely suspects.”
The firebrand right-wing president has repeatedly said he believes Brazil should open the Amazon up to business interests, to allow mining and logging companies to exploit its natural resources.
Brazil is facing growing international criticism over its handling of the Amazon, 60% of which lies in the country.
Earlier this month, Norway and Germany suspended funding for projects to curb deforestation in Brazil after becoming alarmed by changes to the way projects were selected under Bolsonaro.
French President Emmanuel Macron said on his twitter account the fires in the Amazon forest are an international emergency and should be discussed by the G7 summit that will begin on Saturday (August 24) in Biarritz, France.
Although fires are a regular and natural occurrence during the regular dry season at this time of year, environmentalists blamed the sharp rise on farmers setting the forest alight to clear land for pasture.
Federal prosecutors in Brazil said they are investigating a spike in deforestation and wildfires raging in the Amazon state of Para to determine whether there has been reduced monitoring and enforcement of environmental protections there. (Reuters)
(Production: Pablo Garcia, Leonardo Benassatto, Paul Vieira)
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