- Antarctic sea ice ‘behaving strangely’ as Arctic reaches ‘below-average’ winter peak Carbon Brief
- Antarctic sea ice near historic lows: Arctic ice continues decline Phys.org
- How scientists believe the loss of Arctic sea ice will impact US weather patterns Fox Weather
- Letters to the Editor: Climate change and an ice-free Arctic are our Frankenstein’s monster Yahoo! Voices
- Study warns growing threat could drastically alter Arctic in decade to come: ‘This would transform the Arctic into a completely different environment’ The Cool Down
Tag Archives: Strangely
The Speed of Sound on Mars Is Strangely Different, Scientists Reveal
Scientists have confirmed the speed of sound on Mars, using equipment on the Perseverance rover to study the red planet’s atmosphere, which is very different to Earth’s.
What they discovered could have some strange consequences for communication between future Martians.
The findings suggest that trying to talk in Mars’ atmosphere might produce a weird effect, since higher-pitched sound seems to travel faster than bass notes. Not that we’d try, since Mars’ atmosphere is unbreathable, but it’s certainly fun to think about!
From a science perspective, the findings, announced at the 53rd Lunar and Planetary Science Conference by planetary scientist Baptiste Chide of the Los Alamos National Laboratory, reveal high temperature fluctuations at the surface of Mars that warrant further investigation.
The speed of sound is not a universal constant. It can change, depending on the density and temperature of the medium through which it travels; the denser the medium, the faster it goes.
That’s why sound travels about 343 meters (1,125 feet) per second in our atmosphere at 20 degrees Celsius, but also at 1,480 meters per second in water, and at 5,100 meters per second in steel.
Mars’ atmosphere is a lot more tenuous than Earth’s, around 0.020 kg/m3, compared to about 1.2 kg/m3 for Earth. That alone means that sound would propagate differently on the red planet.
But the layer of the atmosphere just above the surface, known as the Planetary Boundary Layer, has added complications: During the day, the warming of the surface generates convective updrafts that create strong turbulence.
Conventional instruments for testing surface thermal gradients are highly accurate, but can suffer from various interference effects. Fortunately, Perseverance has something unique: microphones that can allow us to hear the sounds of Mars, and a laser that can trigger a perfectly timed noise.
The SuperCam microphone was included to record acoustic pressure fluctuations from the rover’s laser-induced breakdown spectroscopy instrument as it ablates rock and soil samples at the Martian surface.
NASA’s Perseverance rover on Mars. (NASA/JPL-Caltech/MSSS)
This came with an excellent benefit, as it turns out. Chide and his team measured the time between the laser firing and the sound reaching the SuperCam microphone at 2.1 meters altitude, to measure the speed of sound at the surface.
“The speed of sound retrieved by this technique is computed over the entire acoustic propagation path, which goes from the ground to the height of the microphone,” the researchers write in their conference paper.
“Therefore, at any given wavelength it is convoluted by the variations of temperature and wind speed and direction along this path.”
The results back up predictions made using what we know of the Martian atmosphere, confirming that sounds propagate through the atmosphere near the surface at roughly 240 meters per second.
However, the quirk of Mars’ shifting soundscape is something completely out of the blue, with conditions on Mars leading to a quirk not seen anywhere else.
“Due to the unique properties of the carbon dioxide molecules at low pressure, Mars is the only terrestrial-planet atmosphere in the Solar System experiencing a change in speed of sound right in the middle of the audible bandwidth (20 Hertz to 20,000 Hertz),” the researchers write.
At frequencies above 240 Hertz, the collision-activated vibrational modes of carbon dioxide molecules do not have enough time to relax, or return to their original state. The result of this is that sound travels more than 10 meters per second faster at higher frequencies than it does at low ones.
This could lead to what the researchers call a “unique listening experience” on Mars, with higher-pitched sounds arriving sooner to the listener than lower ones.
Given that any human astronauts traveling to Mars anytime soon will need to be wearing pressurized spacesuits with comms equipment, or living in pressurized habitat modules, this is unlikely to pose an immediate problem – but it could be a fun concept for science-fiction writers to tinker with.
Because the speed of sound changes due to temperature fluctuations, the team was also able to use the microphone to measure large and rapid temperature changes on the Martian surface that other sensors had not been able to detect. This data can help fill in some of the blanks on Mars’ rapidly changing planetary boundary layer.
The team plans to continue using SuperCam microphone data to observe how things like daily and seasonal variations might affect the speed of sound on Mars. They also plan to compare acoustic temperature readings to readings from other instruments to try to figure out the large fluctuations.
You can read the conference paper on the conference website.
Mysterious repeating fast radio burst from space looks strangely familiar, scientists realize
Scientists got a strange sense of déjà vu when they took a close look at a mysterious series of bright flashes in a galaxy just 12 million light-years away.
The flashes, known as a repeating fast radio burst (FRB), appear surprisingly similar to flashes found in the Crab Nebula. The Crab Nebula is a famous remnant from an old stellar explosion, or supernova, that humans observed in 1054 AD, which was recorded by several distinct cultures. The colorful remnants have displayed bright and brilliant flashes that look a lot like the newly found FRBs, which occurred in the galaxy M81, researchers said.
“Some of the signals we measured are short and extremely powerful, in just the same way as some signals from the Crab pulsar,” Kenzie Nimmo, a Ph.D. student in astronomy at the Netherlands Institute for Radio Astronomy and the University of Amsterdam in the Netherlands, said in a statement.
Related: ‘Weird signal’ hails from the Milky Way. What’s causing it?
The explosion in what’s now the Crab Nebula was recorded on July 4, 1054, by Chinese astronomers, who saw a new or “guest” star above the southern horn of Taurus. The “guest” shone brightly in the sky for 23 days and was 6 times more luminous than Venus, the astronomers recorded. It was still visible for almost two years after the explosion, and was recorded by Arab and Japanese astronomers as well.
The remnant was best visible with a telescope, and that meant the remaining nebula was only spotted for the first time in 1731 by British astronomer John Bevis. French astronomer Charles Messier independently observed it 27 years later and added it to his now-famous catalog of Messier objects, designating the nebula as Messier 1 or M1.
And it wasn’t until the 1960s when astronomers noticed a fluctuating radio source that coincided with the location of the Crab Nebula and eventually determined that the signal came from a pulsar, a kind of neutron star (itself a super-dense stellar corpse left by a supernova) with a strong magnetic field.
But despite the known cause of the Crab Nebula’s bursts and their similarity to those seen in M81, astronomers aren’t sure yet what’s happening in galaxy M81. These FRBs were first spotted in January 2020, coming from the direction of the constellation Ursa Major, the Great Bear.
To date, FRBs have mostly been found in galaxies studded with young stars, but the M81 sightings are an exception, since a network of a dozen radio dishes pinpointed the source of the signal quite clearly to an old group of stars known as a globular cluster.
One candidate for explaining FRBs is that these bright flashes come from magnetars — the strongest magnets in the universe and another type of supernova remnant. And this explanation makes sense where young stars are common, but it’s trickier when it comes to M81, the researchers said.
“We expect magnetars to be shiny and new, and definitely not surrounded by old stars,” Jason Hessels, University of Amsterdam and ASTRON, said in the statement. “If what we’re looking at here really is a magnetar, then it can’t have been formed from a young star exploding. There has to be another way.”
One possible explanation might be that a white dwarf (the cooling core of a large burnt-out star) pulled gas off an unlucky neighboring star. Over time, the researchers suspect, the extra mass may have caused the white dwarf to collapse into a magnetar.
All told, although the scientists aren’t positive what caused the signal or why it’s so similar to the one emanating from the Crab Nebula, they suspect the answer is something unusual — whether an unusual magnetar, an unusual pulsar or another celestial phenomenon.
The research was published in two papers Wednesday (Feb. 23): one in Nature Astronomy led by Nimmo, and the other in Nature led by Franz Kirsten, who is with the Chalmers University of Technology and the Netherlands Institute for Radio Astronomy.
Follow Elizabeth Howell on Twitter @howellspace. Follow us on Twitter @Spacedotcom or Facebook.
Strangely Massive Black Hole Discovered in Milky Way Satellite Galaxy
Astronomers at The University of Texas at Austin’s McDonald Observatory have discovered an unusually massive 
McDonald Observatory astronomers have found that Leo I (inset), a tiny satellite galaxy of the Milky Way (main image), has a black hole nearly as massive as the Milky Way’s. Leo I is 30 times smaller than the Milky Way. The result could signal changes in astronomers’ understanding of galaxy evolution. Credit: ESA/Gaia/DPAC; SDSS (inset)
Led by recent UT Austin doctoral graduate María José Bustamante, the team includes UT astronomers Eva Noyola, Karl Gebhardt and Greg Zeimann, as well as colleagues from Germany’s Max Planck Institute for Extraterrestrial Physics (MPE).
For their observations, they used a unique instrument called VIRUS-W on McDonald Observatory’s 2.7-meter Harlan J. Smith Telescope.
When the team fed their improved data and sophisticated models into a supercomputer at UT Austin’s Texas Advanced Computing Center, they got a startling result.
“The models are screaming that you need a black hole at the center; you don’t really need a lot of dark matter,” Gebhardt said. “You have a very small galaxy that is falling into the Milky Way, and its black hole is about as massive as the Milky Way’s. The mass ratio is absolutely huge. The Milky Way is dominant; the Leo I black hole is almost comparable.” The result is unprecedented.
The researchers said the result was different from the past studies of Leo I due to a combination of better data and the supercomputer simulations. The central, dense region of the galaxy was mostly unexplored in previous studies, which concentrated on the velocities of individual stars. The current study showed that for those few velocities that were taken in the past, there was a bias toward low velocities. This, in turn, decreased the inferred amount of matter enclosed within their orbits.
The 2.7-meter (107-inch) Harlan J. Smith Telescope at The University of Texas at Austin McDonald Observatory. Credit: Marty Harris/McDonald Observatory
The new data is concentrated in the central region and is unaffected by this bias. The amount of inferred matter enclosed within the stars’ orbits skyrocketed.
The finding could shake up astronomers’ understanding of galaxy evolution, as “there is no explanation for this kind of black hole in dwarf spheroidal galaxies,” Bustamante said.
The result is all the more important as astronomers have used galaxies such as Leo I, called “dwarf spheroidal galaxies,” for 20 years to understand how dark matter is distributed within galaxies, Gebhardt added. This new type of black hole merger also gives gravitational wave observatories a new signal to search for.
“If the mass of Leo I’s black hole is high, that may explain how black holes grow in massive galaxies,” Gebhardt said. That’s because over time, as small galaxies like Leo I fall into larger galaxies, the smaller galaxy’s black hole merges with that of the larger galaxy, increasing its mass.
Built by a team at MPE in Germany, VIRUS-W is the only instrument in the world now that can do this type of dark matter profile study. Noyola pointed out that many southern hemisphere dwarf galaxies are good targets for it, but no southern hemisphere telescope is equipped for it. However, the Giant Magellan Telescope (
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Distant ‘Baby’ Black Holes Are Behaving Strangely, And Scientists Are Perplexed
Radio images of the sky have revealed hundreds of ‘baby’ and supermassive black holes in distant galaxies, with the galaxies’ light bouncing around in unexpected ways.
Galaxies are vast cosmic bodies, tens of thousands of light years in size, made up of gas, dust, and stars (like our Sun).
Given their size, you’d expect the amount of light emitted from galaxies would change slowly and steadily, over timescales far beyond a person’s lifetime.
But our research, published in the Monthly Notices of the Royal Astronomical Society, found a surprising population of galaxies whose light changes much more quickly, in just a matter of years.
What is a radio galaxy?
Astronomers think there’s a supermassive black hole at the centre of most galaxies. Some of these are ‘active’, which means they emit a lot of radiation.
Their powerful gravitational fields pull in matter from their surroundings and rip it apart into an orbiting donut of hot plasma called an ‘accretion disk’.
This disk orbits the black hole at nearly the speed of light. Magnetic fields accelerate high-energy particles from the disk in long, thin streams or ‘jets’ along the rotational axes of the black hole. As they get further from the black hole, these jets blossom into large mushroom-shaped clouds or ‘lobes’.
This entire structure is what makes up a radio galaxy, so called because it gives off a lot of radio-frequency radiation. It can be hundreds, thousands or even millions of light years across and therefore can take aeons to show any dramatic changes.
Astronomers have long questioned why some radio galaxies host enormous lobes, while others remain small and confined. Two theories exist. One is that the jets are held back by dense material around the black hole, often referred to as frustrated lobes.
However, the details around this phenomenon remain unknown. It’s still unclear whether the lobes are only temporarily confined by a small, extremely dense surrounding environment – or if they’re slowly pushing through a larger but less dense environment.
The second theory to explain smaller lobes is the jets are young and have not yet extended to great distances.
Hercules A’s supermassive black hole emitting high energy particle jets into radio lobes. (NASA/ESA/NRAO)
Old ones are red, babies are blue
Both young and old radio galaxies can be identified by a clever use of modern radio astronomy: looking at their ‘radio colour’.
We looked at data from the GaLactic and Extragalactic All Sky MWA (GLEAM) survey, which sees the sky at 20 different radio frequencies, giving astronomers an unparalleled ‘radio colour’ view of the sky.
From the data, baby radio galaxies appear blue, which means they’re brighter at higher radio frequencies. Meanwhile the old and dying radio galaxies appear red and are brighter in the lower radio frequencies.
We identified 554 baby radio galaxies. When we looked at identical data taken a year later, we were surprised to see 123 of these were bouncing around in their brightness, appearing to flicker. This left us with a puzzle.
Something more than one light year in size can’t vary so much in brightness over less than one year without breaking the laws of physics. So, either our galaxies were far smaller than expected, or something else was happening.
Luckily, we had the data we needed to find out.
Past research on the variability of radio galaxies has used either a small number of galaxies, archival data collected from many different telescopes, or was conducted using only a single frequency.
For our research, we surveyed more than 21,000 galaxies over one year across multiple radio frequencies. This makes it the first ‘spectral variability’ survey, enabling us to see how galaxies change brightness at different frequencies.
Some of our bouncing baby radio galaxies changed so much over the year we doubt they are babies at all. There’s a chance these compact radio galaxies are actually angsty teens rapidly growing into adults much faster than we expected.
While most of our variable galaxies increased or decreased in brightness by roughly the same amount across all radio colours, some didn’t. Also, 51 galaxies changed in both brightness and colour, which may be a clue as to what causes the variability.
Three possibilities for what is happening
1) Twinkling galaxies
As light from stars travels through Earth’s atmosphere, it is distorted. This creates the twinkling effect of stars we see in the night sky, called ‘scintillation’. The light from the radio galaxies in this survey passed through our Milky Way galaxy to reach our telescopes on Earth.
Thus, the gas and dust within our galaxy could have distorted it the same way, resulting in a twinkling effect.
2) Looking down the barrel
In our three-dimensional Universe, sometimes black holes shoot high energy particles directly towards us on Earth. These radio galaxies are called ‘blazars’.
Instead of seeing long thin jets and large mushroom-shaped lobes, we see blazars as a very tiny bright dot. They can show extreme variability in short timescales, since any little ejection of matter from the supermassive black hole itself is directed straight towards us.
3) Black hole burps
When the central supermassive black hole ‘burps’ some extra particles they form a clump slowly travelling along the jets. As the clump propagates outwards, we can detect it first in the ‘radio blue’ and then later in the ‘radio red’.
So we may be detecting giant black hole burps slowly travelling through space.
Where to now?
This is the first time we’ve had the technological ability to conduct a large-scale variability survey over multiple radio colours. The results suggest our understanding of the radio sky is lacking and perhaps radio galaxies are more dynamic than we expected.
As the next generation of telescopes come online, in particular the Square Kilometre Array (SKA), astronomers will build up a dynamic picture of the sky over many years.
In the meantime, it’s worth watching these weirdly behaving radio galaxies and keeping a particularly close eye on the bouncing babies, too. 
Kathryn Ross, PhD Student, Curtin University and Natasha Hurley-Walker, Radio Astronomer, Curtin University.
This article is republished from The Conversation under a Creative Commons license. Read the original article.