Monday, November 13, 2023

Astronomers request retitling of galaxies named after ‘violent colonialist’ explorer Magellan

Genevieve Holl-Allen
Sun, November 12, 2023 

The dwarf galaxies are in the Milky Way and can be visible to the naked eye from the Southern Hemisphere - VW Pics/Universal Images Group Editorial

A group of astronomers has called for galaxies named after the 16th-century Portuguese explorer Ferdinand Magellan to be renamed because of his “violent colonialist legacy”.

The Large and Small Magellanic Clouds are dwarf galaxies in the Milky Way that can be visible to the naked eye from the Southern Hemisphere.

They are claimed to have been discovered by Magellan and his crew during their first circumnavigation of the world between 1519 and 1522.

However, a group of astronomers in the United States has asked the International Astronomical Union, the body in charge of naming astronomical objects, for the Magellanic Clouds to be renamed.

Mia de los Reyes, an assistant professor of astronomy at Amherst College, Massachusetts, wrote in the American Physical Society journal that “the beauty of these starry objects is clouded by their names”.

Prof De los Reyes described Magellan as “a coloniser, a slaver and a murderer” and added: “Now I and a coalition of astronomers are calling for the scientific community to rename these galaxies, as well as other astronomical objects, institutions, and facilities that bear his name.”

She criticised Magellan as “no astronomer” and said that he was not the first to document the galaxies, but that indigenous peoples had “names and legends for these systems that predate Magellan by thousands of years”.



Magellan was described by one astronomer as 'a coloniser, a slaver and a murderer' - Universal History Archive/Universal Images Group Editorial

Prof de los Reyes also called for the twin Magellan Telescopes to be renamed.

They currently reside in Chile, which she described as “a country with a history of violent Spanish conquest”.

“Indeed, Magellan’s ‘discovery’ of the Strait of Magellan allowed Spanish conquistadors to explore Chile’s coast and led to genocidal campaigns against the native Mapuche people,” she said.


“I and many other astronomers believe that astronomical objects and facilities should not be named after Magellan, or after anyone else with a violent colonialist legacy.”

Bob Blackman, the Conservative MP for Harrow East, described the calls to rename the galaxies as “absolute nonsense”.

He said: “We can all look back on various different people’s involvement in the slave trade, but the reality is that if you’re going to start renaming everything that involved everyone from the slave trade you won’t have many left.”

In 2020, Nasa said that it was “examining” its use of unofficial terminology for the use of some cosmic objects “as part of its commitment to diversity, equity, and inclusion”.

At the time, the American space body said that it would no longer refer to planetary nebula NGC 2392 as the “Eskimo Nebula” nor to a pair of spiral galaxies in the Virgo Galaxy Cluster as “Siamese Twins Galaxy”.

Thomas Zurbuchen, the associate administrator of Nasa’s Science Mission Directorate, said at the time: “Our goal is that all names are aligned with our values of diversity and inclusion, and we’ll proactively work with the scientific community to help ensure that.

“Science is for everyone, and every facet of our work needs to reflect that value.”

Tiny galaxies that had their stars stolen could be a 'missing link' in cosmic evolution

Robert Lea
Sun, November 12, 2023 

A diagram showing the transformation from a normal dwarf galaxy to an ultra-compact dwarf galaxy.

Astronomers have spotted the eroding remains of 100 dwarf galaxies that have been violently stripped of their outer layer of stars by larger galaxies. These disrupted galaxies represent the "missing link" in the evolution of a puzzling type of galaxy called ultra-compact dwarf galaxies (UCDs).

The discovery shows that UCDs — which are among the densest collections of stars in the universe — are the fossilized remains of normal dwarf galaxies that have been destroyed in violent gravitational encounters with other galaxies.

Astronomers first discovered UCDs more than two decades ago. The ultra-dense galaxies posed a mystery for astronomers because they are smaller and more compact than ordinary dwarf galaxies but larger than the star clusters they most closely resemble. Scientists theorized that UCDs were the remains of destroyed dwarf galaxies, but they lacked an intermediate galaxy to help confirm the transition.

So astronomers at the Gemini North telescope atop Mauna Kea in Hawai'i began searching for these cosmic missing links around the Virgo Cluster — a group of around 2,000 galaxies located around 65 million light-years from Earth. The telescope spotted dozens of dwarf galaxies that seem to be undergoing this transformation.

"Our results provide the most complete picture of the origin of this mysterious class of galaxy that was discovered nearly 25 years ago," Eric Peng, a NOIRLab astronomer at the Kavli Institute for Astronomy and Astrophysics at Peking University, said in a statement. "Here we show that 106 small galaxies in the Virgo cluster have sizes between normal dwarf galaxies and UCDs, revealing a continuum that fills the 'size gap' between star clusters and galaxies."

Related: Astronomers just caught the tiniest cannibal galaxy in the universe

Peng is a co-author of a paper detailing the discovery of these missing link galaxies published Wednesday, Nov. 8, in the journal Nature.

The recently identified galaxies seem to be in the early stages of UCD formation. All are located close to massive galaxies. This suggests that the gravitational influence of the nearby massive galaxies has stripped these smaller cosmic objects of their stars and gas.

The astronomers also saw objects within the Virgo Cluster with stretched and diffuse envelopes of gas and stars, as if they are currently being dragged away. Other objects seem to show different phases of this UCDtransition.


An image of NGC 3628 

"Once we analyzed the Gemini observations and eliminated all the background contamination, we could see that these transition galaxies existed almost exclusively near the largest galaxies," lead author Laixiang Wang, a scientist at Peking University, said in the statement. "We immediately knew that environmental transformation had to be important."

When arranged into a time sequence, the team got a picture of what appears to be the story of these star-robbed galaxies. "It's exciting that we can finally see this transformation in action," Peng concluded."It tells us that many of these UCDs are visible fossil remnants of ancient dwarf galaxies in galaxy clusters, and our results suggest that there are likely many more low-mass remnants to be found."



Martian rocks keep hitting Earth, but something doesn’t add up

Joshua Hawkins
Sun, November 12, 2023 


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For thousands of years, Martian rocks have bombarded Earth, sent flying through space after being ejected from their homeworld by violent impacts or volcanic processes. But as we collect these tiny samples, scientists have started to learn something interesting: the age of these Martian rocks doesn’t line up with what we know about Mars’ age as a whole. They’re a lot younger.

Mars is really old. Scientists believe the planet finished forming around 4.56 billion years ago, roughly 90 million years before our own planet. Further, evidence suggests that most of the Martian surface is old. So, why are chunks of Martian rock showing such a young age?


mars

The answer, they say, most likely lies in the constant bombardment of the Martian surface by meteorites and asteroids. With roughly 200 bombardments that create 4-meter craters each year, the Martian surface is constantly spewing more rock into space, some of which finds its way to Earth. The reason the Martian rock’s age doesn’t seem to add up is because the younger rock is replacing the older rock as it gets ejected from the planet.

This means that the younger rock from under the surface, which is still being replenished by volcanic activity, is eventually exposed to the surface and thus becomes the ejecta that meteorites send flying into space. This, a group of scientists explain in a paper published in Earth and Planetary Science Letters, could help us understand why the Martian rocks found on Earth appear so young.

Understanding how Mars is changing – both inside and out – is important as NASA and others prepare for the first manned missions to Mars. Further, scientists are constantly looking for new ways to understand how the planets within our solar system formed, and how that can teach us more about the universe’s evolution as a whole.

The sun is blinding us to thousands of potentially lethal asteroids. Can scientists spot them before it's too late?

Brandon Specktor
Sun, November 12, 202

Illustration of an asteroid coming through the atmosphere towards a city.


On the morning of Feb. 15, 2013, a meteor the size of a semitrailer shot out from the direction of the rising sun and exploded in a fireball over the city of Chelyabinsk, Russia. Briefly glowing brighter than the sun itself, the meteor exploded with 30 times more energy than the bomb that destroyed Hiroshima, exploding some 14 miles (22 kilometers) above the ground. The blast shattered windows on more than 7,000 buildings, temporarily blinded pedestrians, inflicted instantaneous ultraviolet burns and otherwise injured more than 1,600 people. Fortunately, no known deaths resulted.

The Chelyabinsk meteor is thought to be the biggest natural space object to enter Earth's atmosphere in more than 100 years. Yet no observatory on Earth saw it coming. Arriving from the direction of the sun, the rock remained hidden in our biggest blind spot, until it was too late.

Events like these are, fortunately, uncommon. Rocks the size of the Chelyabinsk meteor — roughly 66 feet (20 meters) wide — breach Earth's atmosphere once every 50 to 100 years, according to an estimate from the European Space Agency (ESA). Larger asteroids strike even less frequently. To date, astronomers have mapped the orbits of more than 33,000 near-Earth asteroids and found that none pose a risk of hitting our planet for at least the next century.


But you can't calculate the risk of an asteroid you can't see — and there are untold thousands of them, including some large enough to destroy cities and potentially trigger mass-extinction events, moving on unknowable trajectories around our star, experts told Live Science. It's a harsh reality that has astronomers both concerned about the possible consequences and motivated to find as many of our solar system's hidden asteroids as possible. Once we know about them, deadly asteroids can either be monitored and deflected if needed, or if all else fails, populations can be warned to relocate to avoid mass casualties.

"The most problematic object is the one you don't know about," Amy Mainzer, a professor of planetary science at the University of Arizona and principal investigator for two NASA asteroid-hunting missions, told Live Science. "If we can know what's out there, then we can have a much better estimate of the true risk."


Killers from the sun


The animation depicts a mapping of the positions of known near-Earth objects (NEOs) at points in time over the past 20 years, and finishes with a map of all known asteroids as of January 2018.

At any moment, the sun hides countless asteroids from view. This includes a constantly rotating cast of Apollo asteroids — near-Earth objects that spend most of their time far beyond the orbit of Earth but occasionally cross our planet's path to swoop closer to the sun — as well as the mysterious class of asteroids called the Atens, which orbit almost entirely interior to Earth, ever on the planet's dayside.

"Aten asteroids are the most dangerous, because they cross Earth's orbit just barely at their most distant point," Scott Sheppard, a staff scientist at the Carnegie Institution for Science, told Live Science. "You would never see one coming, to some degree, because they're never in the darkness of the night sky."

As with all asteroids, the majority of these hidden space rocks are likely small enough to burn up completely in Earth's atmosphere upon contact. But it's estimated that there are also many undiscovered asteroids measuring more than 460 feet (140 m) in diameter — large enough to survive the plunge through the atmosphere and cause catastrophic local damage upon impact, Mainzer said. Asteroids with this destructive potential are sometimes dubbed "city killers."

"We think we've found roughly 40% of those asteroids in the 140-meter neighborhood," Mainzer said. According to NASA estimates, that leaves about 14,000 left to be found.


Asteroid size infographic.

There may also be far, far bigger objects awaiting us in the sun's glare. Though exceptionally rare, a handful of "planet killer" asteroids — which measure more than 3,280 feet (1 km) in diameter and are capable of kicking up enough dust to trigger a global extinction event — may lurk in the sun's glare, Sheppard said.

In 2022, Sheppard and his colleagues discovered one such planet killer obscured by the sun, which they described in a paper in The Astronomical Journal. The researchers were hunting for asteroids near Venus, borrowing time from several large telescopes to scan the horizon for five to 10 minutes each night at twilight, when they discovered 2022 AP7 — a mile-wide (1.5 km) behemoth with a quirky five-year orbit that makes the giant space rock almost permanently invisible to telescopes.

"When it's in the night sky, it's at its furthest point from the sun, and it's very faint," Sheppard said. "The only time it's somewhat bright is when it's interior to Earth, near the sun."

Currently, 2022 AP7 crosses Earth's orbit only when our planet and the asteroid are on opposite sides of the sun, making it harmless. However, that gap will slowly narrow over thousands of years, bringing the two objects closer and closer to a potentially catastrophic collision. And it's likely not the only one.

"Through our survey to this date, we find that there's definitely several more kilometer-size Aten asteroids out there to be found," Sheppard added.



A blinding puzzle


Three near-Earth asteroids (NEAs) hiding in the glare of the Sun.

Surveying asteroids near the sun poses a unique challenge for astronomers. Most space-based telescopes gaze toward the planet's nightside, to avoid both solar glare and radiation damage. Ground-based telescopes, meanwhile, face even greater restrictions.

"Not only is the glare of the sun a problem, but the timing is a big problem as well," Sheppard said. "The sun has to set to a certain position below the horizon before they even let you open the telescope, and the sky has to be just dark enough where you can take images and not saturate."

Once the sun reaches this fleeting position, ground-based telescopes have less than 30 minutes to survey the area near the edge of the sun before it dips below the horizon and disappears from view entirely, Sheppard added.

During this brief window, ground-based telescopes have the added challenge of peering straight through Earth's atmosphere, which appears thickest near the horizon and causes light from distant objects to flicker and diffuse. Gases in the atmosphere also absorb many wavelengths of infrared light — the thermal radiation that astronomers use to detect some of the faintest, coolest objects in the universe.

It's hardly an ideal scenario for spotting small, dark, fast-moving chunks of rubble.

"That's why you need to go to space," Luca Conversi, manager of ESA's Near-Earth Object (NEO) Coordination Centre, told Live Science.

Salvation in space


Diagram showing Salvation from space in orbit with the Earth, moon and sun. An asteroid belt is shown.

Orbiting hundreds of miles over Earth and far beyond, space telescopes are free from the distorting effects of the planet's atmosphere. This unlocks a powerful tool in their arsenals: infrared imaging, or the ability to detect heat coming off of space objects, rather than just the reflected sunlight that makes objects detectable by visible-light telescopes.

"Only a small portion of an asteroid's surface is illuminated by the sun, even in space," Conversi said. "So instead of looking at sunlight reflected from the surface, [infrared telescopes] look at the thermal emission of the asteroid itself, so we're able to find it."

This means that even asteroids that are visually dark, like the recently visited asteroid Bennu, shine "like glowing coals" when seen in infrared, Mainzer said.

Currently, there's only one infrared space telescope that's actively looking for near-Earth asteroids — the Near-Earth Object Wide-field Infrared Survey Explorer, or NEOWISE. Launched in 2009 as simply WISE, the telescope was designed to detect objects far from Earth. But in 2013, after the Chelyabinsk incident, WISE was roused from a two-year hibernation as NEOWISE, with new software and a new mission to detect potentially troublesome near-Earth asteroids.

But NEOWISE was never able to look toward the sun — and its mission is expected to end for good by July 2024, Mainzer said. That will leave new asteroid detection solely in the hands of ground-based surveys until the next generation of space-based telescopes can launch later this decade.

"Go look up."


NEO Surveyor in an infrared starfield filled with asteroids.

Two planned spacecraft should help to significantly demystify the dangers of the solar blind zone: NASA's NEO Surveyor, currently planned to launch in 2027, and ESA's NEOMIR, which is still in its early planning phase and will launch no sooner than 2030, Conversi said.

Both spacecraft will be equipped with infrared detectors and tall solar shades that will allow them to look for asteroids very near to the sun's glare, and both will orbit at the first Lagrange point (L1) between Earth and the sun, where the gravitational pull of the two objects is balanced. NEO Surveyor will complete a full scan of the sky every two weeks, splitting its focus evenly between the dawn and dusk sides of the sun, said Mainzer, the principal investigator for both NEOWISE and NEO Surveyor. The telescope is expected to primarily uncover near-Earth objects ranging from 50 to 100 m (164 to 328 feet) wide.

NEOMIR, meanwhile, would complement NEO Surveyor by scanning a ring-shaped area around the sun every six hours or so, Conversi said. Between the two spacecraft, even asteroids as small as the Chelyabinsk meteor should be spotted somewhere in their orbits long before impact, the researchers said.

"According to our predictions, NEOMIR would have seen the Chelyabinsk meteor about one week before impact," Conversi said. "More than enough time to alert the population and take some measures."

In the case of a small, Chelyabinsk-size meteor that explodes before reaching the ground, those measures could include alerting people in the impact zone to shelter and stay away from windows. Larger objects would hopefully be detected long before their date of impact, allowing people to evacuate the area if necessary. "Planet killers" require years of planning to safely deflect, but are also the easiest to spot far in advance.

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'Planet killer' asteroids pose no threat to Earth for at least 1,000 years — but smaller rocks could still be a problem

How many 'city killer' asteroids narrowly miss Earth each year?

— NASA finally reveals 1st sample from potentially-hazardous asteroid Bennu — and it may contain the seeds of life

But with both NEO Surveyor and NEOMIR years away from seeing the light of day, astronomers will continue to rely on the best ground-based methods available to parse the mysteries of the sun. Even with these spacecraft operational, a small percentage of near-sun asteroids will likely remain undetectable, Conversi said. Fortunately, the risks of a deadly impact remain low, and will hopefully only lower as astronomers gather more and better information.

"Go look up," Mainz

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