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‘Oumuamua was an iceberg of molecular hydrogen, scientists claim

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June 9 (UPI) — Ever since scientists spotted ‘Oumuamua, the solar system’s first documented interstellar visitor, there has been some debate over whether the object was a comet or an asteroid.

Now, astronomers argue ‘Oumuamua was a neither a comet nor an asteroid, but a new type of object.

“We hypothesize in the paper that ‘Oumuamua was a hydrogen iceberg,” Darryl Seligman, postdoctoral research fellow at the University of Chicago, told UPI in an email.

Seligman and his research partner, Gregory Laughlin of Yale University, published their hypothesis on Tuesday in the Astrophysical Journal Letters.

By the time astronomers first saw ‘Oumuamua, it was already headed on its way back toward interstellar space, but scientists were able to make out its shape, clock its spin rate and calculate its mass.

While initial analysis of the object’s trajectory suggested it moved like a comet, ‘Oumuamua didn’t look like one. It didn’t have a tail and it was dark.

To better understand the object’s composition, Seligman and Laughlin took a closer look at ‘Oumuamua’s movement through our solar system. Observations revealed a slight acceleration on the object’s path away from the sun, a surprise.

Fighting against the sun’s gravitational pull should have caused a slight slowdown, not an acceleration. Seligman and Laughlin determined that the acceleration was most likely caused by outgassing.

“What happens is that a comet has ice, or volatiles, on the surface,” Seligman said. “When the comet gets close enough to the sun, the photons from the sun can provide enough energy to sublimate the ice.”

Once the sun’s heat severs the bonds between molecules in the ice, the solar energy begins to quickly excite the now gaseous molecules.

“Now, this gas produces an outflow, in which the molecules explode off of the surface of the sun away from the comet, generally in the direction of the sun,” Seligman said. “By the conservation of momentum, this outflow will also back react on the comet, and push it away from the sun. We see this type of behavior in solar system comets all of the time.”

The outgassing of ‘Oumuamua was different than most comets, however. The interstellar visitor was without a tail, or coma, and the object’s acceleration was too great to be explained by water ice.

When Seligman and Laughlin looked for better candidates, they settled on molecular hydrogen. Their calculations showed the outgassing of modest amounts of molecular hydrogen ice would produce sharp acceleration without yielding a visible coma.

The discovery has implications for tracking down ‘Oumuamua’s cosmic origins.

“Molecular hydrogen ice is a weird thing to think about, simply because H2 will sublimate at approximately 6 degrees Kelvin, which is only a few degrees above the cosmic microwave background at 2.7 Kelvin,” Seligman said.

“So there are not many places in the universe that are thought to be able to get cold enough to freeze out hydrogen,” Seligman said. “Certainly, you won’t be finding frozen hydrogen most places in a protoplanetary disk where comets and asteroids form.”

The best place to find molecular hydrogen ice is someplace really cold, like inside a failed stellar core in a giant molecular cloud, some of the coldest, densest places in the universe.

Seligman and Laughlin hypothesize that what’s called a prestellar core, a dense orb of star-making material, failed to generate fusion. Without fusion, the core remained especially cold and accumulated chunks of hydrogen ice that were eventually ejected into interstellar space.

Such an origin story not only explains ‘Oumuamua’s acceleration through our solar system, but also its unusual baguette-like shape.

The weathering of a hydrogen iceberg would naturally produce an especially oblong object. When it passed through our solar system, ‘Oumuamua was six times longer than it was wide. Seligman likened the process to using a bar of soap.

“You start with a bar of soap which is somewhat elongated, maybe 2:1, and as you continuously use it, you take off roughly equal amounts of soap everywhere,” Seligman said. “So you always take a larger percentage of soap from the small axis as the long axis.”

“This continuous removal of material evenly off of the surface naturally produces a smaller but more elongated object,” he said. “That is what we envisioned happened to Oumuamua, but instead of soap, it was hydrogen coming off the surface, both due to the solar photons and the galactic cosmic rays that were hitting it after it was ejected from the Giant Molecular Cloud.”

The hypothesis proferred by Seligman and Laughlin, however, can’t be directly proven. To better understand ‘Oumuamua, scientists need to start by detecting and studying a lot more instrestellar objects — specifically, hydrogen icebergs — the researchers said. And they need to find them before they make their closest apporach to the sun.

But, according to Seligman, the ultimate goal is to acquire material samples.

“I think advocating for an interception mission to an interstellar object is an important next step,” he said.



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NASA’s OSIRIS-REx touches down on asteroid Bennu to nab sample

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Oct. 20 (UPI) — NASA’s OSIRIS-REx touched down on asteroid Bennu on Tuesday evening in a mission to scoop a sample of rocks and dirt.

The spacecraft — the Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer — made soft contact with the asteroid at 6:12 p.m. EDT.

The historic “touch and go” event featured animation displaying OSIRIS-REx’s sample collection activities in real time. It takes time for real images of the touchdown to travel back to the Earth, so they won’t be released to the public until Wednesday.

The craft executed a series of maneuvers over the course of several hours before making soft contact with the surface of the asteroid to collect regolith, or rocks and dirt.

“It will be four and a half hours of anxiousness,” Beth Buck, OSIRIS-REx mission operations manager at Lockheed Martin Space, said in a news conference ahead of the event.

Buck made a comparison to the descent of a spacecraft on Mars, when there is typically “seven minutes of terror.”

The goal is to learn more about the solar system’s history and help “planetary defense” engineers with missions to protect earth from rogue asteroids. Bennu is believed to be a window into the solar system’s past since it’s a pristine, carbon-rich body carrying building blocks of both planets and life.

At around 1:50 p.m. EDT, the spacecraft left orbit around the asteroid before executing a series of burns to position itself over a sampling area nicknamed Nightingale.

Once in position, the craft began its approach to the asteroid at 5:50 p.m. EDT. It then spent about 15 seconds attempting to collect the regolith sample before backing away again.

The area, which is 52 feet in diameter, will make for a more demanding landing than expected, Kenneth Getzandanner, OSIRIS-REx flight dynamics manager at the NASA Goddard Space Flight Center in Maryland, said in the news conference.

The original mission called for a landing “zone” about 150% larger than Nightingale, at 82 feet, but that changed because Bennu was more rocky than expected.

The goal was to collect at least 1.7 ounces of fine-grained material, but the spacecraft can carry up to 4.4 pounds, Heather Enos, OSIRIS-REx deputy principal investigator at the University of Arizona said.

“I would love for that capsule to be completely full,” Enos said.

Though early images from the asteroid should hint at whether the mission succeeded, it will take engineers roughly 10 days to compare and analyze the mass before and after the maneuver to actually know how much dirt is inside the OSIRIS-REx.

If it failed, the spacecraft has enough fuel to attempt two more touch downs to collect material.

The spacecraft is expected to return to Earth, with the regolith sample from Bennu, in 2023.



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SpaceX scrubs Starlink launch until Thursday, if weather cooperates

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Oct. 21 (UPI) — Just three days after sending 60 more Starlink satellites into orbit, SpaceX is aiming to launch another batch of broadband satellites into space from Florida.

If the weather cooperates, Thursday’s launch will be SpaceX’s 15th Starlink mission.

Liftoff had been scheduled for 12:29 p.m. EDT Wednesday aboard a Falcon 9 rocket at Launch Complex 40 at Cape Canaveral Air Force Station, but controllers scrubbed the launch due to weather and rescheduled for 12:14 p.m. on Thursday.

With a launch Sunday, SpaceX increased the size of their Starlink constellation to nearly 800 satellites. The 15th mission will see another 60-odd satellites join the network.

“The goal of Starlink is to create a network that will help provide Internet services to those who are not yet connected, and to provide reliable and affordable Internet across the globe,” according to the Kennedy Space Center.

Weather for Wednesday’s planned launch had looked so-so and the Space Force’s 45th Weather Squadron predicted a 60 percent chance of favorable conditions.

“A mid-level inverted trough and associated easterly wave currently across the Bahamas will meander into the state over the next few days, bringing enhanced moisture, cloud cover, and instability with a higher coverage of showers and storms,” Space Force forecasters wrote.

They said Thursday’s forecast looks quite similar to Wednesday’s.

Earlier this month, SpaceX founder and CEO Elon Musk tweeted that Starlink’s constellation was big enough to begin beta-testing the Internet service system in both the United States and southern Canada.

SpaceX has already offered Starlink Internet services to emergency responders in wildfire-stricken areas of Washington State.

Washington’s Hoh tribe is also using the Internet service to provide their members online education and telehealth services.



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Chernobyl-level radiation harms bumblebee reproduction

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Oct. 21 (UPI) — Bees are more sensitive to radiation than scientists thought. Scientists found the reproduction rates of bumblebees declined significantly when exposed to Chernobyl-level radiation.

The research, published Wednesday in the journal Proceedings of the Royal Society B: Biological Sciences, suggests radiation in Ukraine’s Chernobyl Exclusion Zone could impair pollination services, triggering wider ecological consequences than previously estimated.

Humans are not allowed to live in the Chernobyl Exclusion Zone, the disaster area more directly impacted by the 1986 nuclear accident, the worst in history. However, the destroyed nuclear reactors are surrounded by forests that are populated by robust populations of birds, bears, bison, lynx, moose, wolves and more.

Efforts to gauge the effects of radiation contamination on insects have yielded mixed results in the past. While some studies have suggested insects are relatively radiation-resistant, others have demonstrated significant impairment.

When researchers exposed bumblebees in the lab to radiation dose of 100 µGyh-1, an amount approximating exposure inside the Chernobyl Exclusion Zone, reproduction rates among the bees dropped between 30 and 45 percent.

Researchers found a direct correlation between the size of the radiation dose and reproduction rate declines. Lower levels of radiation had a smaller effect, while larger doses yielded greater declines.

Scientists were surprised to find they were able to detect reproductive rate declines at very small levels of radiation exposure.

“Our research provides much needed understanding as to the effects of radiation in highly contaminated areas and this is the first research to underpin the international recommendation for the effects of radiation on bees,” lead study author Katherine Raines, environmental scientist at the University of Stirling in Scotland, said in a news release.



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