Article  Acceleration of Interstellar visitor explained (but criticized) + Asteroid risk worse

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Strange Acceleration of Mysterious Interstellar Visitor Finally Explained

INTRO: An interstellar object that is currently on its long journey back out of our Solar System has a completely natural explanation, in spite of its odd quirks. The peculiar acceleration of 'Oumuamua, new research confirms, can be fully attributed to the release of molecular hydrogen gas.

This, according to astrochemist Jennifer Bergner of the University of California, Berkeley and astrophysicist Darryl Seligman of Cornell University, is further evidence that the cigar-shaped chunk of rock started off as a planet seed before being booted off to wander the galaxy untethered to a star.

It's an elegant solution, one that, the researchers write, "can explain many of 'Oumuamua's peculiar properties without fine-tuning" – or resorting to extraordinary claims about the object's nature... (MORE - missing details)

RELATED: `Oumuamua Was Not a Hydrogen-Water Iceberg ..... Experts suggest alien 'Mothership' sending UFOs to Earth

Risk of Giant Asteroids Hitting Earth Could Be Worse Than We Realized

EXCERPTS: NASA's Goddard Space Flight Center chief scientist, James Garvin, thinks we might have been misreading traces of some of the more serious asteroid strikes that have occurred within the past million years. If he's right, the odds of being hit by something nasty could be higher than current estimates predict.

[...] Garvin and his team used a new catalog of high-resolution satellite images to take a closer look at the weathered remains of some of the largest impact craters formed within the last million years, in an effort to better gauge their true size.

Based on their analysis, a number of these craters feature faint rings beyond what have typically been considered their outer rims, effectively making them larger than previously presumed.

For example, a roughly 12 to 14 kilometer-wide depression in Kazakhstan called Zhaminshin is thought to have been created by a meteorite with a diameter of 200 to 400 meters that hit Earth around 90,000 years ago – the most recent impact to have potentially caused a 'nuclear winter' style event.

However, based on the new analysis, this already large event could have been even more catastrophic, leaving a crater that's actually closer to 30 kilometers across.

The rim diameters of three other large craters have also been recalculated, all doubling or tripling in size. The implications are profound, suggesting kilometer-sized objects are coming down from above every few ten-thousand years... (MORE - missing details)
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`Oumuamua Was Not a Hydrogen-Water Iceberg

EXCERPTS: In a new paper that I submitted this morning for publication in collaboration with Thiem Hoang, we show that the paper published today in Nature by Jennifer Bergner and Darryl Seligman miscalculated the surface temperature of `Oumuamua. Bergner and Seligman suggested that the peculiar acceleration of `Oumuamua can be explained if it was made of water ice which was partly dissociated into hydrogen by cosmic-rays in interstellar space.

However, their surface temperature calculation near the Sun ignored the crucial cooling effect of evaporating hydrogen. By adding the cooling from hydrogen evaporation, our new paper shows that the surface temperature of the iceberg is reduced by an order of magnitude.

The correct calculation of the surface temperature is straightforward...

[...] By now, the Nature paper was celebrated by science journalists worldwide. When I informed one of them about the temperature miscalculation earlier today, he told me that his journal will not post a correction to its original report in order “not to confuse the readers.” This response is appropriate for political matters, when the truth is not easily discerned and multiple opinions are equally valid. However, the benefit of science is that a calculation can be shown to be right or wrong, and the oath of science reporters should be to adhere to a full disclosure of the scientific truth... (MORE - missing details)

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