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astronomy (5)

Yggdrasil...

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The rings of Saturn take center stage in this portrait by the Hubble Space Telescope taken on June 20, 2019. Credit: NASA, ESA, A. Simon (GSFC), M.H. Wong (University of California, Berkeley) and the OPAL Team

 

Topics: Astronomy, Planetary Science, Space Exploration


There was a strong temptation to use the Norse legend of Bifrost - the rainbow bridge made popular in Thor, but rings of trees tell their age, so...

Yggdrasil is the tree of life, and it is an eternal green Ash tree; the branches stretch out over all of the nine worlds in Norse mythology, and extend up and above the heavens. Norse mythology: Yggdrasil.

Against earlier studies estimating an age of just 100 million years, new research suggests the planet’s rings could be as old as the solar system itself.

The great Saturn ring debate is far from settled, a new study suggests.

For years, scientists have argued about the age of Saturn’s famous rings: Are they ancient, dating to the birth of the planet itself? Or did the ring system form more recently, in just the past hundred million years or so?

This latter hypothesis has been gaining steam in the last few years, with multiple papers reporting that the rings could be even younger than the dinosaurs. Such studies cite the rings’ composition—more than 95% pure water ice—and total mass, which NASA’s Cassini mission pegged at about 15.4 million billion metric tons shortly after the probe’s epic “grand finale” at Saturn in 2017. (For perspective, 15.4 million billion metric tons is about 40% the mass of the Saturn moon Mimas, which is 250 miles, or 400 kilometers, wide.)

 

Saturn’s Rings May Be Ancient After All, Mike Wall, Space.com and Scientific American

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Aleph Null or Not...

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No, it's not real. Credit: Getty Images

 

Topics: Astronomy, Drake Equation, Existentialism, SETI


For many people, "UFO" is synonymous with aliens, but it's worth reminding ourselves that it literally stands for "unidentified flying object." An unidentified object could be just about anything, because … well, it's unidentified. One of our mottoes in science is that "extraordinary claims require extraordinary evidence." This doesn't mean that crazy-sounding things are never true; it means that we should practice due diligence when thinking about overturning well-understood or well-tested ideas. This motto also suggests we keep an eye on Occam's razor—the idea that the simplest explanation is the most likely to be true.

As enthusiastic as I had been regarding alien visitations (there was a cottage industry in the 1970s that still thrives in Internet circles), one has to ask the question: what would aliens want with Earth? Between here and there whatever their governments are in need of, they can either engineer it or find other options way before engaging warp speed.

Colonization: If history serves as guide, the First Nation/Native Americans encountered colonists that barely survived their first winter. They were repaid like the natives who met Columbus with slaughter.

Africans did trade captured rival tribesmen and women in the budding international slave trade that "made America great." They conferred with Europeans typically with superior weaponry for trade of valuables to compensate their treachery.

Any aliens that can travel parsecs from their home world to Earth doesn't have anything benevolent in mind once arriving, E.T. or Star Trek not withstanding.

Ignoring us: When is the last time you had a conversation with a moth? On the evolutionary scale, you have way more sophistication than something flitting from tree to flower. Aliens if existing and surviving millions of years older than us probably if anything might have the same relationship to us as we have to Lepidoptera.

The sobering possibility: climate change, conventional conflicts, mass shootings pollution and nuclear conflagration - humans are far smarter than the lowly moth, but moths nor butterflies are destroying their own habitat.

We may not see aliens because they may have caused their own extinction before they built starships.

 

No E.T. Life Yet? That might be a warning, Kelsey Johnson, Scientific American

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Remnants...

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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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]

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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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