astrophysics (6)

Twin Paradox...

Retired astronaut Mark Kelly (left) cracks a slight smile while posing with his identical twin brother, astronaut Scott Kelly (right). As part of NASA's Twins Study, Scott took a long trip to space, while Mark remained on Earth. Researchers then monitored how their bodies reacted to their differing environments. NASA


Topics: Astronaut, Astrophysics, Genetics, NASA, Spaceflight

Brothers compete. So in 2016, when astronaut Scott Kelly returned to Earth after spending a year in space, it must have really annoyed his identical twin brother — retired astronaut Mark Kelly — that Scott was two inches taller than when he left. However, Scott's temporary increase in height was not the only thing that changed during his trip.

As part of NASA's Twins Study, while Scott was in space, Mark went about his daily life on Earth. Over the course of the year-long mission, researchers tracked changes in both brothers' biological markers to pinpoint any variances. Because the twins share the same genetic code, researchers reasoned that any observed differences could tentatively — though not definitively — be linked to Scott's time aboard the International Space Station (ISS). This allowed them to take advantage of a unique opportunity and explore how an extended stay in space may impact the human body.

Based on their results, which were published this week in the journal Science, spaceflight can definitely trigger changes in the human body. But the vast majority of these changes disappear within just a few short months of returning to Earth.

Most notably, the researchers found that living in a microgravity environment can: damage DNA; impact the way thousands of individual genes are expressed; increase the length of telomeres (the shielding caps that protect the ends of our chromosomes); thicken artery walls; modify the microbiome; and increase inflammation — just to name a few.

"This is the dawn of human genomics in space," said Andrew Feinberg, a distinguished professor at Johns Hopkins University and one of the lead investigators for the Twins Study, in a press release. "We developed the methods for doing these types of human genomic studies, and we should be doing more research to draw conclusions about what happens to humans in space."


NASA's Twins Study: Spaceflight changes the human body, but only temporarily
Jake Parks, Astronomy

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Our Shrinking Moon...

New surface features of the Moon have been discovered in a region called Mare Frigoris, outlined here in teal. NASA
Image: New Republic


Topics: Astrophysics, Geophysics, Moon, NASA, Planetary Science

The Moon is shrinking as its interior cools, getting more than about 150 feet (50 meters) skinnier over the last several hundred million years. Just as a grape wrinkles as it shrinks down to a raisin, the Moon gets wrinkles as it shrinks. Unlike the flexible skin on a grape, the Moon’s surface crust is brittle, so it breaks as the Moon shrinks, forming “thrust faults” where one section of crust is pushed up over a neighboring part.

“Our analysis gives the first evidence that these faults are still active and likely producing moonquakes today as the Moon continues to gradually cool and shrink,” said Thomas Watters, senior scientist in the Center for Earth and Planetary Studies at the Smithsonian’s National Air and Space Museum in Washington. “Some of these quakes can be fairly strong, around five on the Richter scale.”

Watters is lead author of a study that analyzed data from four seismometers placed on the Moon by the Apollo astronauts using an algorithm, or mathematical program, developed to pinpoint quake locations detected by a sparse seismic network. The algorithm gave a better estimate of moonquake locations. Seismometers are instruments that measure the shaking produced by quakes, recording the arrival time and strength of various quake waves to get a location estimate, called an epicenter. The study was published May 13 in Nature Geoscience.

Shrinking Moon May Be Generating Moonquakes, NASA

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An artist's impression of the planetesimal orbiting on a 2-hour period within the gaseous disc around SDSS J1228+1040 (by Mark Garlick).


Topics: Astronomy, Astrophysics, Exoplanets, Spectrograph, White Dwarfs

When the hydrogen fuel that keeps a star like our sun burning brightly is exhausted, the star expands into a red giant before collapsing into a hot, dense white dwarf. Although the stellar swelling engulfs nearby planets, theoretical models suggest that some planets and planetary cores up to hundreds of kilometers in diameter can survive the star’s death and fall into closer orbit. But identifying solid bodies around a dim stellar core is difficult. Now Christopher Manser (University of Warwick) and colleagues have used a new spectroscopic method to identify a planetesimal orbiting a white dwarf 400 light-years from our solar system.

Astronomers have discovered most exoplanets—including an asteroid-like body orbiting a white dwarf—via the transit method, identifying periodic dimming as an object passes in front of its host star. But the method requires a lucky geometry of the planetary system’s orbital plane relative to Earth. Manser and his team instead turned to short-cadence optical spectroscopy using data from the 10.4 m Gran Telescopio Canarias in Spain. They focused on one of just a few white dwarfs that, based on metal emission lines in the stellar and disk spectra, are suspected to be surrounded by disks of gas and dust. Minute-by-minute observations over several nights in 2017 and 2018 let the researchers deconstruct the light emanating from the disk and determine how much variation had occurred over a year.


A glimpse of a planetary system’s final stages, Rachel Berkowitz, Physics Today

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Event Horizon...

Scientists have obtained the first-ever image of a black hole — at center of the galaxy M87. Credit: Event Horizon Telescope collaboration et al.


Topics: Astrophysics, Black Holes, Cosmology, Einstein

(Yesterday) At six simultaneous press conferences around the globe, astronomers on Wednesday announced they had accomplished the seemingly impossible: taking a picture of a black hole, a cosmic monster so voracious that light itself cannot escape its clutches.

This historic feat, performed by the Event Horizon Telescope (EHT)—a planet-spanning network of radio observatories—required more than a decade of effort. The project’s name refers to a black hole’s most defining characteristic, an “event horizon” set by the object’s mass and spin beyond which no infalling material, including light, can ever return.

“We have taken the first picture of a black hole,” the EHT project’s director, Sheperd Doeleman, said in a news release. “This is an extraordinary scientific feat accomplished by a team of more than 200 researchers.”

The image unveils the shadowy face of a 6.5-billion-solar-mass supermassive black hole at the core of Messier 87 (M87), a large galaxy some 55 million light-years from Earth in the Virgo galaxy cluster. Such objects are a reflection of Einstein’s theory of general relativity, which predicts that only so much material can be squeezed into any given volume before the overwhelming force of its accumulated gravity causes a collapse—a warp in the fabric of spacetime that swallows itself. Left behind is an almost featureless nothingness that, for lack of better terms, scientists simply call a black hole.

"Gargantua," special effects from the movie, Interstellar, 2014 (Kip Thorne et al guessed right):
Image Source: HDQ Walls dot com


At Last, a Black Hole’s Image Revealed, Lee Billings, Scientific American

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Lumpy Neutron Stars...

An artist’s rendition of a neutron star. Credit: Kevin Gill Flickr (CC by 2.0)


Topics: Astronomy, Astrophysics, Einstein, Gravitational Waves, Neutron Stars

Gravitational waves—the ghostly ripples in spacetime first predicted by Einstein and finally detected a century later by advanced observatories—have sparked a revolution in astrophysics, revealing the otherwise-hidden details of merging black holes and neutron stars. Now, scientists have used these waves to open another new window on the universe, providing new constraints on neutron stars' exact shapes. The result will aid researchers in their ongoing quest to understand the inner workings of these exotic objects.

So far, 11 gravitational-wave events have been detected by the LIGO (Laser Interferometer Gravitational-Wave Observatory) interferometers in Washington and Louisiana and the Virgo gravitational-wave observatory in Italy. Of these events, 10 came from mergers of binary black holes, and one from the merger of two neutron stars. In all cases, the form of the waves matched the predictions of Einstein's theory of general relativity.

For the binary black hole events, the passing waves lasted less than a second; for the merging neutron stars, the emissions occurred for about 100 seconds. But such rapid pulses aren't the only types of gravitational waves that could be streaming through the universe. In particular, solitary neutron stars might be emitting detectable gravitational waves as they spin—signals that could reveal important new details of the stars' topography and internal composition.


Gravitational Observatories Hunt for Lumpy Neutron Stars
David Appell, Scientific American

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Sagittarius A...

Getty Images

Topics: Astronomy, Astrophysics, Black Holes, Cosmology, Einstein

They've captured our imaginations for decades, but we've never actually photographed a black hole before – until now.

Next Wednesday, at several press briefings around the world, scientists will apparently unveil humanity's first-ever photo of a black hole, the European Space Agency said in a statement. Specifically, the photo will be of "Sagittarius A," the supermassive black hole that's at the center of our Milky Way galaxy.

But aren't black holes, well, black, and thus invisible, so none of our telescopes can "see" them? Yes – therefore the image we're likely to see will be of the "event horizon," the edge of the black hole where light can't escape. [1]


Next week, a collection of countries around the world are going to make a big announcement, and no one is sure exactly what it’s going to be. However, there are some possibilities, and the most exciting one is that they are about to reveal the first-ever photograph of the event horizon of a black hole.

Taking a photo of a black hole is not an easy task. Not only are black holes famous for not letting any light escape, even the nearest known black holes are very far away. The specific black hole astronomers wanted to photograph, Sagittarius A*, lies at the center of our galaxy 25,000 light-years away.

The international Event Horizon Telescope project announced its plan to photograph Sagittarius A* back in 2017, and they enlisted some of the world’s biggest telescopes to help out. The researchers used half a dozen radio telescopes, including the ALMA telescope in Chile and the James Clerk Maxwell telescope in Hawaii, to stare at Sagittarius A* over the past two years.

And while a picture of the black hole itself is impossible, the EHT astronomers were really aiming at the next best thing: the event horizon, the border of the black hole beyond which not even light can escape. At the event horizon, gravity is so strong that light will orbit the black hole like planets orbit stars, and our telescopes should be able to pick that up. [2]

1. 'Something no human has seen before': The first-ever photograph of a black hole will likely be unveiled next week, Doyle Rice, USA Today
2. We Might Be About to See the First Ever Photo of a Black Hole, Avery Thomson, Popular Mechanics

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