RADIO signals racing through space with the precision of an atomic clock have been traced back to their source and confirmed Albert Einstein’s famous general theory of relativity.
Radio signals from space have long fascinated astronomers scouting the cosmos for signs of alien life. In 2007, scientists were excited by the discovery of so-called Fast Radio Bursts (FRBs) reaching Earth from an unknown source in the universe. Forty years before that, astronomers encountered radio emissions reaching Earth from distant pulsars – fast-spinning neutron stars smaller than the Sun. Researchers from the Max Planck Institute for Radio Astronomy in Bonn, Germany, have now mapped out one of these radio signals and confirmed in the process Albert Einstein’s general theory of relativity.
The discovery was made after 14 years of observations of the dead star PSR J1906+0746.
The pulsar sits around 25,000 light-years or 146,965,630,000,000,000 miles from Earth.
As the pulsar spins around, jets of bright radio waves shoot out from the star’s magnetic poles and fly out into space.
If the pulsar’s poles face the Earth’s general direction, the radio waves can wash over our planet like the light of a lighthouse.
Radio signals from space: Astronomers have charted radio beams from a distant pulsar star (Image: GETTY)
Radio signals from space: One of the pulsar’s radio beams disappeared from sight in 2016 (Image: Gregory Desvignes & Michael Kramer, MPIfR)
But unlike the guiding beam from a lighthouse, pulsar jets are incredibly fast and incredibly accurate.
Pulsed signals that arrive on Earth with the accuracy of an atomic clock
Max Planck Institute for Radio Astronomy
In this case, the pulsar PSR J1906+0746 has a spin of just 144 milliseconds.
The Max Planck Institute said in a statement: “Due to their stable rotation, a lighthouse effect produces pulsed signals that arrive on Earth with the accuracy of an atomic clock.
“The large mass, the compactness of the source, and the clock-like properties allow astronomers to use them as laboratories to test Einstein’s general theory of relativity.”
Pulsars can contain up to 40 percent more mass than our Sun but the material is densely packed into a sphere just 12 miles (20km) across.
The spinning stars also boast the most powerful magnetic fields in the universe.
These magnetic fields emit the jets of radio waves from the north and south poles in opposing directions.
Gregory Desvignes of the Max Planck Institute said: “PSR J1906+0746 is a unique laboratory in which we can simultaneously constrain the radio pulsar emission physics and test Einstein’s general theory of relativity.”
Dr Desvignes, who led the study, observed the pulsar between 2005 and 2018 to chart its radio emissions.
Radio signals from space: Pulsars are fast spinning neutron stars that emit periodic radio signals (Image: GETTY)
Radio signals from space: Einstein’s theories predicted gravity warps spacetime (Image: GETTY)
During this time, the astronomers found the radio beams from the pulsar’s north pole disappeared from sight in 2016.
The disappearance was caused by the presence of a second neutron star nearby, which is distorting the spacetime surrounding the binary stars.
The distortion of spacetime through gravity is a key principle proposed by Einstein more than 100 years ago.
Professor Andrew Lyne of The University of Manchester, who observed the pulsar, said: “The extreme gravitational environment of the two neutron stars causes spacetime to be distorted.
“This in turn causes the pulsar to precess, changing the angle we view the radio emission and thus allowing us to map out the emission.”
The researchers estimate the precession will also take a toll on the remaining southern radio beam.
By the year 2028, the radio signals will no longer be visible from Earth.
The pulsar study was published this month on September 6 in the journal Science.
Astronomers have detected a rare pattern in the X-ray bursts coming from a neutron-star system no more than 16,300 light-years away.
That star system, MAXI J1621−501, first turned up on Oct. 9, 2017, in data from the Swift/XRT Deep Galactic Plane Survey as an odd point in space flashing unpredictably with X-rays. That was a sign, researchers wrote in a new paper, of a binary system containing both a normal star and either a neutron star or black hole. Both neutron stars and black holes can create unpredictable X-ray patterns as they absorb matter from their companion stars, but in very different ways.
In black holes, as Live Science has previously reported, the X-rays come from matter accelerating to extreme speeds and generating enormous friction as it falls toward the gravity well. In neutron stars — superdense corpses of giant stars that exploded but haven’t collapsed into singularities — the X-rays come from thermonuclear explosions on their outer crusts. Something is causing atoms to fuse on the outermost parts of these strange stars, releasing enormous energies usually found only deep inside stars (as well as in the cores of powerful hydrogen bombs). Some of that energy escapes as X-ray light.
As matter from a normal star smashes into a supertiny, superheavy neutron star, these thermonuclear explosions create mushroom clouds bright enough to see with X-ray telescopes. The authors of this new paper, released online Aug. 13 in the preprint journal arXiv, show that the X-ray outbursts from MAXI J1621−501 are coming from thermonuclear explosions on the surface of the duo’s neutron star — and that the light from those thermonuclear explosions is following a pattern that repeats roughly every 78 days.
The source of that pattern isn’t entirely clear. Scientists have only found about 30 other lights in space that flicker this way, the researchers wrote. They refer to patterns like this one as “superorbital periods.” That’s because the pattern follows a cycle that lasts much longer than the binary stars’ orbit around one another, which in the case of MAXI J1621−501 takes just 3 to 20 hours.
The best explanation for this 78-day period, the authors wrote, comes from a paper published in the journal Monthly Notices of the Royal Astronomical Society in 1999. Neutron stars in binary systems like this one, the authors wrote, are surrounded by whirling clouds of material that gets sucked off the regular star and toward the neutron star, creating a spinning, gassy skirt called an accretion disk.
A simple model of those cloud disks suggests they are always aligned in one direction — they would look just like the rings circling Saturn if you were to follow the planet around in space, staring edge-on at the rings. In that model, you’d never see any change in the X-ray light, because you’d always be staring at the same spot on the accretion disk between you and the neutron star. The only change to the light would come from changes in the thermonuclear explosions themselves.
But reality is more complicated. What’s likely happening, the authors wrote, is that the whirling disk around the neutron star in this binary system is wobbling from the perspective of Earth, like a top about to tip over. Sometimes the wobble puts more disk between the neutron star and Earth, sometimes less. We can’t see the disk itself. But if that wobble is happening and it causes the disk to cross between us and the star every 78 days, it would create the pattern astronomers have observed.
Astronomers watched MAXI J1621−501 for 15 months after the 2017 discovery, the researchers wrote, and saw the pattern repeat six times. It didn’t repeat perfectly, and there were other, smaller dips in the X-ray light. But the wobbling disk remains far and away the best possible explanation for this weird X-ray pattern in space.
India’s Chandrayaan-2 orbiter circling the moon has spotted the country’s lost Vikram lander on the lunar surface, but there is still no signal from the lander, according to Indian media reports.
K Sivan, chief of the Indian Space Research Organisation, said today (Sept. 8) that the Vikram lander was located by Chandrayaan-2 and efforts to restore contact the probe will continue for at least 14 days, according to a Times of Indiareport.
The Vikram lander went silent Friday (Sept. 6) while attempting a first-ever landing near the moon’s south pole. ISRO lost contact with Vikram when the lander was just 1.2 miles (2 kilometers) above the lunar surface, raising fears that it may have crashed on the moon. The Vikram lander is India’s first moon lander, and is carrying the country’s first lunar rover, called Pragyan.
ISRO officials have not yet released the Chandrayaan-2 image of Vikram on the lunar surface or described the potential condition of the lander. But they have said that despite the lander’s presumed failed moon landing, the craft has already demonstrated key technologies for future missions.
“The Vikram Lander followed the planned descent trajectory from its orbit of 35 km (22 miles) to just below 2 km above the surface,” ISRO officials wrote in an update Saturday (Sept. 7). “All the systems and sensors of the Lander functioned excellently until this point and proved many new technologies such as variable thrust propulsion technology used in the Lander.”
“The Orbiter camera is the highest resolution camera (0.3m) in any lunar mission so far and shall provide high resolution images which will be immensely useful to the global scientific community,” ISRO officials said in the Sept. 7 statement. “The precise launch and mission management has ensured a long life of almost 7 years instead of the planned one year.”
The Indian Space Research Organisation’s Chandrayaan-2 moon orbiter is shown studying the lunar surface from above in this still image from a video animation.(Image credit: India Space Research Organisation)
The Chandrayaan-2 orbiter is equipped with eight different science instruments to study the moon from above. Those instruments include: a high resolution camera, a lunar terrain mapping camera; a solar X-ray monitor; an imaging infrared spectrometer; a dual frequency synthetic aperture radar for studying moon water ice and lunar mapping; a sensor to study the moon’s thin exosphere; and a dual frequency radio science experiment to study the moon’s ionosphere.
The Chandrayaan-2 Orbiter aims to pick up where its predecessor left off.
“This was a unique mission which aimed at studying not just one area of the Moon but all the areas combining the exosphere, the surface as well as the sub-surface of the moon in a single mission,” ISRO officials said in the update. “The Orbiter has already been placed in its intended orbit around the Moon and shall enrich our understanding of the moon’s evolution and mapping of the minerals and water molecules in the Polar Regions, using its eight state-of-the-art scientific instruments.”
NASA has spotted something mysterious in deep space that it can’t quite explain — bright flashes of green and blue spots that appeared and disappeared in a cosmic second.
The NuSTAR X-ray observatory was looking at the Fireworks galaxy (NGC 6946) and saw multiple blobs of blue and green light that appeared and disappeared within weeks, according to a new study published in the Astrophysical Journal. NASA’s Chandra X-ray Observatory also witnessed the appearance and disappearance of the green blob, known as an ultraluminous X-ray source (ULX), confirming the sighting.
“Ten days is a really short amount of time for such a bright object to appear,” said Hannah Earnshaw, a postdoctoral researcher at Caltech, in a statement. “Usually with NuSTAR, we observe more gradual changes over time, and we don’t often observe a source multiple times in quick succession. In this instance, we were fortunate to catch a source changing extremely quickly, which is very exciting.”
This visible-light image of the Fireworks galaxy (NGC 6946) comes from the Digital Sky Survey, and is overlaid with data from NASA’s NuSTAR observatory (in blue and green). Credit: NASA/JPL-Caltech
While researchers are quick to point out that ULXs are a common occurrence in space (this was the fourth one spotted in this galaxy), they also note that ULXs are “typically long-lived.” With this ULX, there was “visible light … detected with the X-ray source,” which likely rules out that it was a supernova.
So what is it? The researchers offered several theories for the appearance of the green blob, including the fact it could be a black hole consuming another object.
“If an object gets too close to a black hole, gravity can pull that object apart, bringing the debris into a close orbit around the black hole,” NASA wrote in the post. “Material at the inner edge of this newly formed disk starts moving so fast that it heats up to millions of degrees and radiates X-rays.”
But given the fact that ULX-4 could be a recurring event, another possible explanation is that it is a neutron star. Neutron stars, which are about the same mass as the Sun, are able to draw in material, creating disks of debris that can generate ULX sources.
However, if the neutron star spins too fast, the magnetic fields it creates can actually cause a barrier, which would prevent the material from reaching the star’s surface.
“It would kind of be like trying to jump onto a carousel that’s spinning at thousands of miles per hour,” Earnshaw added.
The barrier effect would prevent the star from being a source of X-rays. However, the barrier might “waver briefly,” which would allow material to fall through and land onto the neutron star’s surface, which could explain the sudden appearance and disappearance of the ULX, researchers suggested.
“This result is a step towards understanding some of the rarer and more extreme cases in which matter accretes onto black holes or neutron stars,” Earnshaw said.
That spot is a highland that rises between two craters dubbed Manzinus C and Simpelius N. On a grid of the moon’s surface, it would fall at 70.9 degrees south latitude and 22.7 degrees east longitude. It’s about 375 miles (600 kilometers) from the south pole.
And it’s the preferred landing site for India’s moon mission, Chandrayaan-2, which is scheduled to touch down on Friday, Sept. 6, between 4 p.m. and 5 p.m. EDT (Sept. 7, between 1:30 a.m. and 2:30 a.m. local time at mission control in India). The Indian Space Research Organisation (ISRO), which oversees the mission, also has a backup site selected, at 67.7 degrees south latitude and 18.4 degrees west longitude.
Either way, if the landing goes smoothly, the site will become the southernmost spot on the moon to be visited by a spacecraft.
All of NASA’s Apollo landing sites, where astronauts explored the surface, are clustered near the equator on the near side, where it’s easiest and safest to land. That has skewed scientists’ understanding of the samples those astronauts brought back — it’s sometimes difficult to tell whether a characteristic appears in all the samples because it is universal in the moon’s surface or simply because it happens to prevail in this region.
Choosing different lunar landing sites is important for science not solely in order to build a more complete picture of the moon’s geology: The south pole is particularly intriguing. That’s where instruments on board this mission’s predecessor, the Chandrayaan-1 orbiter, detected slabs of water ice buried in the always-shadowed craters near the moon’s south pole.
Chandrayaan-2 is designed to build on that detection, with a mission that cost $150 million, according to Science, the new outlet affiliated with the research journal of the same name. The current project added lander and rover vehicles to the second-generation orbiter.
These two vehicles will touch down just after dawn at the landing site, allowing them to work for about 14 days before the harsh lunar night freezes them. ISRO will attempt to revive the duo when the sun rises again, but the robots weren’t designed to survive the night.
The orbiter component of the mission will continue working for about a year, orbiting from pole to pole in order to augment the hoped-for discoveries of the lander and rover.
The two giant blobs remain mysterious, nearly a decade after their discovery.
In 2010, astronomers working with the Fermi Gamma-ray Space Telescope announced the discovery of two giant blobs. These blobs were centered on the core of the Milky Way galaxy, but they extended above and below the plane of our galactic home for over 25,000 light-years. Their origins are still a mystery, but however they got there, they are emitting copious amounts of high-energy radiation.
More recently, the IceCube array in Antarctica has reported 10 super-duper-high-energy neutrinos sourced from the bubbles, leading some astrophysicists to speculate that some crazy subatomic interactions are afoot. The end result: The Fermi Bubbles are even more mysterious than we thought.
Two giant blobs of hot gas
It’s not easy to make big balls of hot gas. For starters, you need energy, and a lot of it. The kind of energy that can spread hot gas to a distance of over 25,000 light-years doesn’t come easily to a typical galaxy. However, the peculiar orientation of the Fermi Bubbles — extending evenly above and below our galactic center — is a strong clue that they might be tied our central supermassive black hole, known as Sagittarius A*.
Perhaps millions of years ago, Sag A* (the more common name for our giant black hole, because who wants to keep typing or saying “Sagittarius” all the time?) ate a giant meal and got a bad case of indigestion, with the infalling material heating up, twisting around in a complicated dance of electric and magnetic forces, and managing to escape the clutches of the event horizon before falling in. That material, energized beyond belief, raced away from the center of the galaxy, riding on jets of particles accelerated to nearly the speed of light. As they fled to safety, these particles spread and thinned out, but maintained their energetic state to the present day.
Or perhaps a star wandered too close to Sag A* and was ripped to shreds, releasing all that potent gravitational energy in a single violent episode, leading to the formation of the bubbles. Or maybe it had nothing to do with Sag A* itself, but the multitude of stars in the core — perhaps dozens or hundreds of those densely packed stars went supernova at around the same time, ejecting these plumes of gas beyond the confines of the galactic more.
Or maybe none of the above.
No matter what, the bubbles are here, they’re big, and we don’t understand them.
Gamma and the neutrino
You can’t see the Fermi Bubbles with your naked eye. Despite their high temperatures, the gas inside them is incredibly thin, rendering them all but invisible. But something within them is capable of making the highest-energy kind of light there is: gamma rays, which is how the Fermi team spotted them.
We think that the gamma rays are produced within the bubbles by cosmic rays, which themselves are high-energy particles (do you get the overall “high energy” theme here?). Those particles, mostly electrons but probably some heavier fellas too, knock about, emitting the distinctive gamma rays.
But gamma rays aren’t the only things that high-energy particles can produce. Sometimes the cosmic rays interact with each other, perform some complicated subatomic dance of matter and energy, and release a neutrino, an almost-massless particle that only interacts with other particles via the weak nuclear force (which means it hardly ever interacts with normal matter at all).
The IceCube Observatory, situated at the geographic south pole, uses a cubic kilometer of pure Antarctic water ice as a neutrino detector: every once in a rare while, a high-energy neutrino passing through the ice interacts with a water molecule, setting up a domino-like chain reaction that leads to a shower of more familiar particles and a telltale flash of light.
Due to the nature of its detectors, IceCube isn’t the greatest when it comes to pinpointing the exact origin location for a neutrino. But to date, it has found 10 of these little ghosts coming from roughly the direction of the two Fermi Bubbles.
A subatomic puzzle
So something could be producing these extremely exotic neutrinos inside the Fermi Bubbles. Or not — it could just be a coincidence, and the neutrinos are really coming from some distant part of the universe behind the Bubbles.
What’s more, somehow the cosmic rays are producing all the gamma rays, though we’re not exactly sure how. Perhaps we might get lucky: maybe there’s a single set of interactions inside the Bubbles that produces both gamma rays and the right kind of neutrinos that can be detected by IceCube. That would be a big step up in explaining the physics of the Bubbles themselves, and give us a huge clue as to their origins.
Recently, a team of researchers pored through the available data, even adding results from the newly operational High Altitude Water Cherenkov detector (a super-awesome ground-based gamma ray telescope), and combined that information with various theoretical models for the Bubbles, searching for just the right combo.
In one possible scenario, protons inside the Bubbles occasionally slam into each other and produce pions, which are exotic particles that quickly decay into gamma rays. In another one, the flood of high-energy electrons in the Bubbles interacts with the ever-present radiation of the cosmic microwave background, boosting some lucky photons into the gamma regime. In a third, shock waves at the outer edges of the Bubbles use magnetic fields to drive local but lethargic particles to high velocities, which then begin emitting cosmic rays.
But try as they might, the authors of this study couldn’t find any of the scenarios (or any combination of these scenarios) to fit all the data. In short, we still don’t know what drives the gamma ray emission from the Bubbles, whether the Bubbles also produce neutrinos, or what made the Bubbles in the first place. But this is exactly how science is done: collecting data, ruling out hypotheses, and forging onward.
When neutron stars collide, they may result in gargantuan kilonova explosions like the one illustrated here. These blasts send ripples through space-time, and shower their galactic neighborhood in gold and platinum. (Credit: NASA Goddard Space Flight Center)
Mergers of this magnitude are so violent they rattle the fabric of space-time, releasing gravitational waves that spread through the cosmos like ripples on a pond. These mergers also fuel cataclysmic explosions that create heavy metals in an instant, showering their galactic neighborhood in hundreds of planets’ worth of gold and platinum, the authors of the new study said in a statement. (Some scientists suspect that all the gold and platinum on Earth formed in explosions like these, thanks to ancient neutron-star mergers close to our galaxy.)
Astronomers at the Laser Interferometer Gravitational-Wave Observatory (LIGO) got concrete proof that such mergers occur when they detected gravitational waves pulsing out of a stellar crash site for the first time in 2017. Unfortunately, those observations began only about 12 hours after the initial collision, leaving an incomplete picture of what kilonovas look like.
For their new study, an international team of scientists compared the partial dataset from the 2017 merger with more complete observations of a suspected kilonova that occurred in 2016 and was observed by multiple space telescopes. By looking at the 2016 explosion in every available wavelength of light (including X-ray, radio and optical), the team found that this mysterious explosion was nearly identical to the well-known 2017 merger.
“It was a nearly perfect match,” lead study author Eleonora Troja, an associate research scientist at the University of Maryland (UMD), said in the statement. “The infrared data for both events have similar luminosities and exactly the same time scale.”
So, confirmed: The 2016 explosion was indeed a massive galactic merger, likely between two neutron stars, just like the 2017 LIGO discovery. What’s more, because astronomers began observing the 2016 explosion moments after it began, the authors of the new study were able to catch a glimpse of the stellar debris left behind the blast, which was not visible in the 2017 LIGO data.
“The remnant could be a highly magnetized, hypermassive neutron star known as a magnetar, which survived the collision and then collapsed into a black hole,” study co-author Geoffrey Ryan, a postdoctoral fellow at UMD, said in the statement. “This is interesting, because theory suggests that a magnetar should slow or even stop the production of heavy metals,” however, large amounts of heavy metals were clearly visible in the 2016 observations.
This is all to say, when it comes to understanding collisions between the most massive objects in the universe — and the mysterious rains of bling that result — scientists still have more questions than answers.
An image of the Large Magellanic Cloud taken with a ground-based telescope. The inset image was captured by the Hubble Space Telescope, and shows a galaxy cluster teeming with variable Cepheids, a class of stars that flicker regularly. Using this pulsation rate, scientists have calculated the universe’s expansion rate, but that number doesn’t match with values derived from other cosmic phenomena, such as the echo of the Big Bang known as the cosmic microwave background radiation.
There’s a puzzling mystery going on in the universe. Measurements of the rate of cosmic expansion using different methods keep turning up disagreeing results. The situation has been called a “crisis.”
The problem centers on what’s known as the Hubble constant. Named for American astronomer Edwin Hubble, this unit describes how fast the universe is expanding at different distances from Earth. Using data from the European Space Agency’s (ESA) Planck satellite, scientists estimate the rate to be 46,200 mph per million light-years (or, using cosmologists’ units, 67.4 kilometers/second per megaparsec). But calculations using pulsating stars called Cepheids suggest it is 50,400 mph per million light-years (73.4 km/s/Mpc).
If the first number is right, it means scientists have been measuring distances to faraway objects in the universe wrong for many decades. But if the second is correct, then researchers might have to accept the existence of exotic, new physics. Astronomers, understandably, are pretty worked up about this discrepancy.
What is a layperson supposed to make of this situation? And just how important is this difference, which to outsiders looks minor? In order to get to the bottom of the clash, Live Science called in Barry Madore, an astronomer at the University of Chicago and a member of one of the teams undertaking measurements of the Hubble constant.
The trouble starts with Edwin Hubble himself. Back in 1929, he noticed that more-distant galaxies were moving away from Earth faster than their closer-in counterparts. He found a linear relationship between the distance an object was from our planet and the speed at which it was receding.
“That means something spooky is going on,” Madore told Live Science. “Why would we be the center of the universe? The answer, which is not intuitive, is that [distant objects are] not moving. There’s more and more space being created between everything.”
Hubble realized that the universe was expanding, and it seemed to be doing so at a constant rate — hence, the Hubble constant. He measured the value to be about 342,000 miles per hour per million light years (501 km/s/Mpc) — almost 10 times larger than what is currently measured. Over the years, researchers have refined that rate.
Things got weirder in the late 1990s, when two teams of astronomers noticed that distant supernovas were dimmer, and therefore farther away, than expected, said Madore. This indicated that not only was the universe expanding, but it was also accelerating in its expansion. Astronomers named the cause of this mysterious phenomenon dark energy.
Having accepted that the universe was doing something strange, cosmologists turned to the next obvious task: measuring the acceleration as accurately as possible. By doing this, they hoped to retrace the history and evolution of the cosmos from start to finish.
Madore likened this task to walking into a racetrack and getting a single glimpse of the horses running around the field. From just that bit of information, could somebody deduce where all the horses started and which one of them would win?
That kind of question may sound impossible to answer, but that hasn’t stopped scientists from trying. For the last 10 years, the Planck satellite has been measuring the cosmic microwave background, a distant echo of the Big Bang, which provides a snapshot of the infant universe 13 billion years ago. Using the observatory’s data, cosmologists could ascertain a number for the Hubble constant with an extraordinarily small degree of uncertainty.
“It’s beautiful,” Madore said. But, “it contradicts what people have been doing for the last 30 years,” said Madore.
Over those three decades, astronomers have also been using telescopes to look at distant Cepheids and calculate the Hubble constant. These stars flicker at a constant rate depending on their brightness, so researchers can tell exactly how bright a Cepheid should be based on its pulsations. By looking at how dim the stars actually are, astronomers can calculate a distance to them. But estimates of the Hubble constant using Cepheids don’t match the one from Planck.
The discrepancy might look fairly small, but each data point is quite precise and there is no overlap between their uncertainties. The differing sides have pointed fingers at one another, saying that their opponents have included errors throwing off their results, said Madore.
But, he added, each result also depends on large numbers of assumptions. Going back to the horse-race analogy, Madore likened it to trying to figure out the winner while having to infer which horse will get tired first, which will gain a sudden burst of energy at the end, which will slip a bit on the wet patch of grass from yesterday’s rain and many other difficult-to-determine variables.
If the Cepheids teams are wrong, that means astronomers have been measuring distances in the universe incorrectly this whole time, Madore said. But if Planck is wrong, then it’s possible that new and exotic physics would have to be introduced into cosmologists’ models of the universe, he added. These models include different dials, such as the number of types of subatomic particles known as neutrinos in existence, and they are used to interpret the satellite’s data of the cosmic microwave background. To reconcile the Planck value for the Hubble constant with existing models, some of the dials would have to be tweaked, Madore said, but most physicists aren’t quite willing to do so yet.
Hoping to provide another data point that could mediate between the two sides, Madore and his colleagues recently looked at the light of red giant stars. These objects reach the same peak brightness at the end of their lives, meaning that, like with the Cepheids, astronomers can look at how dim they appear from Earth to get a good estimate of their distance and, therefore, calculate the Hubble constant.
The results, released in July, provided a number squarely between the two prior measurements: 47,300 mph per million light-years (69.8 km/s/Mpc). And the uncertainty contained enough overlap to potentially agree with Planck’s results.
But researchers aren’t popping their champagne corks yet, said Madore. “We wanted to make a tie breaker,” he said. “But it didn’t say this side or that side is right. It said there was a lot more slop than everybody thought before.”
Other teams have weighed in. A group called H0 Lenses in COSMOGRAIL’s Wellspring (H0LICOW) is looking at distant bright objects in the early universe called quasars whose light has been gravitationally lensed by massive objects in between us and them. By studying these quasars, the group recently came upwith an estimate closer to the astronomers’ side. Information from the Laser Interferometer Gravitational-Wave Observatory (LIGO), which looks at gravitational waves from crashing neutron stars, could provide another independent data point. But such calculations are still in their early stages, said Madore, and have yet to reach full maturity.
For his part, Madore said he thinks the middle number between Planck and the astronomers’ value will eventually prevail, though he wouldn’t wager too much on that possibility at the moment. But until some conclusion is found, he would like to see researchers’ attitudes toned down a bit.
“A lot of froth has been put on top of this by people who insist they’re right,” he said. “It’s sufficiently important that it needs to be resolved, but it’s going to take time.”
An unprecedented view of the surface of an asteroid located around 300 million kilometers away.
The Japanese Hayabusa2 mission continues to surprise us. This time with an unprecedented view of the surface features that are located on asteroid Ryugu and they happen to closely resemble meteorites that occasionally impact the Earth.
On October 3, 2018, the Hayabusa2 spacecraft launched a landing module to the surface of the Ryugu asteroid from an altitude of around 41 meters. The MASCOT module struck a rock and bounced 17 meters along the surface of the asteroid before staying face down inside a depression on the asteroid.
The landing module was able to spin around and take some incredible images of Ryugu’s geological features, both in the 6-minute descent and during the 17 hours, it was on the surface before its batteries ran out, leaving the modules stranded on the asteroid as the massive rock makes its way around the sun.
Scientists have published these images today, and say that the photographs could have very interesting implications in our understanding of asteroids, comets and the cosmic bodies of our solar system.
Analysis of the images taken by MASCOT has revealed that the surface of Asteroid Ryugu closely resembles meteorites found on Earth known as carbonaceous chondrites.
“What we have from these images is really knowing how the rocks and material are distributed on the surface of this asteroid, what the weathering history of this stuff is, and the geologic context,” explained Ralf Jaumann, lead author of the study in an interview with Gizmodo.
“It’s the first information on this kind of material in its original environment.”Advertisement
R. Jaumann published a study titled, “Images from the surface of asteroid Ryugu show rocks similar to carbonaceous chondrite meteorites,” in the journal Science, detailing the surface features and the implications of the findings.
The images taken by MASCOT revealed different types of rocks on Ryugu’s surface, including dark rocks, crumbled as cauliflowers, and brighter and smoother rocks, all between a few centimeters to tens of meters wide.
But there seemed to be no visible dust; This suggests that there must be some process that removes dust that causes it to be lost in space or absorbed more deeply into the asteroid. Seen up close, these rocks seem to contain bright parts, inlays of some different material, according to the article published in Science.
Those inlays are exciting: they look bluish and reddish, Jaumann said, and they seem to be similar in size to the inlays found in the carbonaceous chondrites found on Earth. That is important.
“Carbonaceous material is the primordial material of the solar system, from which all planets and moons originate,” Jaumann said to Space.com.
“Thus, if we want to understand the planetary formation, including the formation of Earth, we need to understand its building parts.”
It’s an extra-sunny Sunday for NASA’s Parker Solar Probe, which is making its third close pass around the sun today (Sept. 1).
The spacecraft is designed to help scientists better understand the sun and, in particular, its outer atmosphere, called the corona. That atmosphere is millions of degrees, whether Fahrenheit or Celsius — much hotter than the visible surface of the star — and scientists can’t quite figure out where all that heat comes from.
So NASA built the Parker Solar Probe, which will make 24 daring dives into the corona by the end of its mission, in 2025. The spacecraft launched last August and has already completed two solar flybys. The third close encounter will come today around 1:50 p.m. EDT (1750 GMT).
For this third flyby, scientists were able to turn the probe’s instruments on earlier in the course of the maneuver. That’s thanks to unexpectedly high levels of data return from the spacecraft. Operators on the ground received data from the probe’s first two passes more quickly than expected and were able to gather additional observations during the second pass.
This time around, the instruments will be working for 35 days straight — three times as long as they did on the first two orbits. The longer observing window means that the probe will be taking measurements from about twice as far away from the visible surface of the sun. Scientists hope that extra data will help them crack enduring mysteries about the sun and how it affects the solar system.Click here for more Space.com videos…‘Touching’ the Sun with NASA’s Parker Solar ProbeVolume 0%
Each loop around the sun brings the spacecraft a bit deeper into the star’s atmosphere, giving the probe a more daring chance at science on every orbit. After today’s perihelion, as these close encounters are called, things will get even sunnier for the spacecraft.
The Parker Solar Probe’s next loop will include a maneuver around Venus that uses the hellish planet’s gravity to nudge the spacecraft closer into the sun, setting up the next perihelion for Jan. 29, 2020.
You’ve probably heard of Schrödinger’s cat, the unfortunate feline in a box that is simultaneously alive and dead until the box is opened to reveal its actual state. Well, now wrap your mind around Schrödinger’s time, a situation in which one event can simultaneously be the cause and effect of another event.
Such a scenario may be inevitable in any theory of quantum gravity, a still-murky area of physics that seeks to combine Albert Einstein’s theory of general relativity with the workings of quantum mechanics. In a new paper, scientists create a mashup of the two by imagining starships near an enormous planet whose mass slows time. They conclude that the starships could find themselves in a state where causation is reversed: One event could end up causing another event that happened before it.
“One can devise this kind of scenario where temporal order or cause and effect are in superposition of being reversed or not reversed,” said study co-author Igor Pikovski, a physicist at the Center for Quantum Science and Engineering at Stevens Institute of Technology in New Jersey. “This is something we expect should take place once we have a full theory of quantum gravity.”
The famous Schrödinger’s cat thought experiment asks a viewer to imagine a box holding a cat and a radioactive particle, which, once decayed, will kill the unfortunate feline. By the principle of quantum superposition, the cat’s survival or death is equally likely until measured — so until the box is opened, the cat is simultaneously alive and dead. In quantum mechanics, superposition means that a particle can exist in multiple states at the same time, just like Schrödinger’s cat.
The new thought experiment, published Aug. 21 in the journal Nature Communications, combines the principle of quantum superposition with Einstein’s theory of general relativity. General relativity says that the mass of a giant object can slow down time. This is well established as true and measurable, Pikovski said; an astronaut orbiting Earth will experience time just a smidge faster than his or her twin back on the planet. (This is also why falling into a black hole would be a very gradual experience.)
Thus, if a futuristic spacecraft were near a massive planet, its crew would experience time as a little bit slower than would people in a fellow spacecraft stationed farther away. Now, throw in a little quantum mechanics, and you can imagine a situation in which that planet is superpositioned simultaneously near to and far away from the two spacecraft.
Time gets weird
In this superpositioned scenario of two ships experiencing time on different timelines, cause and effect could get wonky. For example, say the ships are asked to conduct a training mission in which they fire at each other and dodge each other’s fire, knowing full well the time the missiles will launch and intercept their positions. If there’s no massive planet nearby messing with time’s flow, this is a simple exercise. On the other hand, if that massive planet were present and the ship’s captain didn’t take the slowing of time into account, the crew might dodge too late and be destroyed.
With the planet in superposition, simultaneously near and far, it would be impossible to know whether the ships would dodge too late and destroy each other or whether they would move aside and survive. What’s more, cause and effect could be reversed, Pikovski said. Imagine two events, A and B, that are causally related.
“A and B can influence each other, but in one case A is before B, while in the other case B is before A” in a superposition state, Pikovski said. That means that both A and B are simultaneously the cause and effect of each other. Fortunately for the likely-confused crews of these imaginary spacecraft, Pikovski said, they would have a mathematical way to analyze each other’s transmissions to confirm that they were in a superpositioned state.
Obviously, in real life, planets don’t move around the galaxy willy-nilly. But the thought experiment could have practical implications for quantum computing, even without working out an entire theory of quantum gravity, Pikovski said. By using superpositions in computations, a quantum-computing system could simultaneously evaluate a process as a cause and as an effect.
“Quantum computers may be able to use this for more efficient computation,” he said.