Astronomy

Following a technical error in November 2023, NASA's deep-space explorer has resumed full science operations.

Strangely, the Star Trek: Discovery ship's far-future fate was revealed in 2018 'Short Trek' episode 'Calypso'.

The James Webb Space Telescope (JWST) has just increased the number of known distant supernovae by tenfold. This rapid expansion of astronomers’ catalog of supernovae is extremely valuable, not least because it improves the reliability of measurements for the expansion of the universe.

“Webb is a supernova discovery machine,” said Christa DeCoursey of the Steward Observatory and the University of Arizona at a press conference earlier this week. “The sheer number of detections plus the great distances to these supernovae are the two most exciting outcomes from our survey.”

JWST’s advantage over previous surveys is its specialty in infrared wavelengths. As the universe expands, the light coming from distant objects gets stretched, “redshifting” the light to longer wavelengths. Most of the light from the early universe, therefore, reaches us in infrared.

That has allowed the telescope to discover a host of new supernovae in distant galaxies, some of which are the furthest ever seen. Supernovas are transient objects – they’re exploding stars that change and fade over time – so catching them happening at such great distances is exciting.

Previously, the most distant supernova fell about the redshift 2 mark (3.3 billion years into the Universe’s life). The new record holder just discovered by JWST has a redshift of 3.6, meaning it exploded just 1.8 billion years after the Big Bang.

Closeups of three out of the 80 transients discovered by JWST, where a change of brightness was observed between 2022 and 2023. NASA, ESA, CSA, STScI, Christa DeCoursey (University of Arizona), JADES Collaboration

Of the 80 new objects discovered, several were type 1a supernovae. These are of particular interest to scientists, because they are known to explode with a standard brightness, making it possible to take accurate distance measurements for the objects.

At least, that’s true for nearby supernovae. This new survey will allow researchers to see if that pattern remains true in the distant universe too, or if they behaved differently under the conditions of the early universe. At that time, there were fewer heavy elements in the cores of stars. Finding out if this changes their behavior is essential to measuring the expansion of spacetime itself, and could help resolve the crisis in cosmology, in which measurements using type 1a supernovae don’t align with those using the Cosmic Microwave Background.

“This is really our first sample of what the high-redshift universe looks like for transient science,” said Justin Pierel, a NASA Einstein Fellow at the Space Telescope Science Institute. “We are trying to identify whether distant supernovae are fundamentally different from or very much like what we see in the nearby universe.”

Pierel carried out a preliminary examination of one of the new supernovae, found at redshift 2.9. It seems to show no difference from the expected brightness, which is good news for astronomers’ confidence in their distance measurements to date. Further analysis of other supernovae in the data will be forthcoming.

Other outcomes of this research include a better understanding of star formation and the mechanisms behind supernova explosions in the early universe.

“We’re essentially opening a new window on the transient universe,” said STScI Fellow Matthew Siebert. “Historically, whenever we’ve done that, we’ve found extremely exciting things — things that we didn’t expect.”

Learn more:

“NASA’s Webb Opens New Window on Supernova Science.” JWST.

The post Webb is an Amazing Supernova Hunter appeared first on Universe Today.

The theory of relativity predicts black holes should be able to form from light alone, but incorporating quantum effects makes it impossible

The theory of relativity predicts black holes should be able to form from light alone, but incorporating quantum effects makes it impossible

NASA’s venerable Voyager 1 spacecraft has resumed normal science operations with all four functioning instruments for the first time in more than six months

Astronomers using the CHIME telescope are looking at strange, one-off cosmic explosions with a new angle. This could bring us closer to solving the lingering mystery of fast radio bursts.

New findings show the black hole at the heart of our Milky Way galaxy had a late growth spurt.

Soil sourced directly from the lunar surface could help astronauts establish and sustain a permanent presence on the moon.

The supermassive black hole at the heart of our Milky Way Galaxy is a quiet monster. However, Sagittarius A* (or Sgr A* for short) is not totally dormant. Occasionally it gobbles down a blob of molecular gas or even a star and then suffers a bit of indigestion. That emits x-ray flares to surrounding space.

Sgr A* is the closest supermassive black hole to Earth, at a distance of 26,000 light-years. Studying the nearby environment is tough due to the black hole’s intense gravitational pull. It distorts the view of nearby objects, making them difficult to observe. However, there are ways to do it by looking at the effect of its flares on nearby molecular clouds. Astronomers recently found the centuries-old echoes of previously unknown flares that occurred long before there were telescopes to observe them. Those echoes indicate that Sgr A* eats fairly often.

Two researchers from Michigan State University—Grace Sanger-Johnson and Jack Uteg—studied the flares and their light-echoes in detail. What they found shows activity at Sgr A* in the very distant past when Sgr A* ingested material. X-ray emissions from that activity traveled for hundreds of years from Sgr A* to bounce off of and brighten a nearby molecular cloud. That created a light echo that traveled another roughly 26,000 years before reaching Earth. So, when Uteg and Sanger studied these flares and light echoes, they were literally looking into the past.

Astronomers do know about outbursts from Sgr A* from other observations. Here’s a view from NASA’s Imaging X-ray Polarimetry Explorer and Chandra X-ray Observatory. The combination of IXPE and Chandra data helped researchers determine that the X-ray light identified in the molecular clouds originated from Sagittarius A* during an outburst approximately 200 years ago. Credits: IXPE: NASA/MSFC/F. Marin et al; Chandra: NASA/CXC/SAO; Image Processing: L.Frattare, J.Major & K.Arcand Searching for Sgr A* X-ray Flares with NuSTAR

Sanger-Johnson analyzed ten years’ worth of data looking for X-ray flares generated by Sgr A*’s eating habits. During the search, she found evidence for nine more such outbursts.

The flares are typically quite dramatic. Because they’re so bright, they provide astronomers a chance to study the immediate environment around the black hole. The data Sanger-Johnson studied came from the NuSTAR mission. It zeroes in on high-energy X-ray and gamma-ray emissions. These typically come from active regions in the hearts of galaxies, supernova explosions, and other active events.

The data Sanger-Johnson collected and analyzed is now a database of flares from Sgr A. “We hope that by building up this bank of data on Sgr A flares, we and other astronomers can analyze the properties of these X-ray flares and infer the physical conditions inside the extreme environment of the supermassive black hole,” Sanger-Johnson said.

Tracking the Echoes of Flares

While Sanger-Johnson was working with the NuSTAR data, undergraduate researcher Jack Uteg studied the activity around the black hole. He analyzed 20 years of data about a giant molecular cloud called “the Bridge”. The data came from observations made by NuSTAR and the European Space Agency’s XMM-Newton observatory. The Bridge lies close to Sgr A* and normally wouldn’t give off its own light.

So, astronomers took notice when it brightened up in X-rays, according to Uteg, who is constructing a timeline of Sgr A‘s past outbursts. “The brightness we see is most likely the delayed reflection of past X-ray outbursts from Sgr A,” he said. “We first observed an increase in luminosity around 2008. Then, for the next 12 years, X-ray signals from the Bridge continued to increase until it hit peak brightness in 2020.”

Uteg’s work helped astronomers determine that Sgr A* was about five orders of magnitude brighter in X-rays than it is now. That brightening indicates our central supermassive black hole had probably cannibalized a nearby gas cloud. And, the brightness revealed other properties, according to Uteg. “One of the main reasons we care about this cloud getting brighter is that it lets us constrain how bright the Sgr A* outburst was in the past,” he said.

What Those Light-echoes from Sgr A* Reveal

Thanks to Sanger-Brown and Uteg’s work, astronomers have another way around the difficulties of observing around black holes. “Both flares and fireworks light up the darkness and help us observe things we wouldn’t normally be able to,” she said. “That’s why astronomers need to know when and where these flares occur, so they can study the black hole’s environment using that light.”

Astronomers know that the black hole does gobble up nearby material on a variable basis, but these findings help them constrain how often it happens and how the resulting flares affect the nearby neighborhood. Many questions remain about how often these flares occur and have happened in the past, according to MSU assistant professor Shuo Zhang, who acted as team lead for these two studies.

“This is the first time that we have constructed a 24-year-long variability for a molecular cloud surrounding our supermassive black hole that has reached its peak X-ray luminosity,” Zhang said. “It allows us to tell the past activity of Sgr A* from about 200 years ago. Our research team at MSU will continue this ‘astroarchaeology game’ to further unravel the mysteries of the Milky Way’s center.”

These results of the MSU team’s work were presented at the summer 2024 meeting of the American Astronomical Society.

For More Information

‘Flares’ and ‘Echoes’ from the Milky Way’s Monster Black Hole

About NuStar

About XMM-Newton

The post Echoes of Flares from the Milky Way’s Supermassive Black Hole appeared first on Universe Today.

Two types of fusion reactor called tokamaks and stellarators both have drawbacks – but a new design combining parts from both could offer the best of both worlds

Two types of fusion reactor called tokamaks and stellarators both have drawbacks – but a new design combining parts from both could offer the best of both worlds

This NASA/ESA Hubble Space Telescope image features the globular cluster NGC 2005. It’s not an unusual globular cluster in and of itself, but it is a peculiarity when compared to its surroundings. NGC 2005 is located about 750 light-years from the heart of the Large Magellanic Cloud (LMC), which is the Milky Way’s largest satellite galaxy some 162,000 light-years from Earth.

Rock art is a truly global phenomenon, with discoveries of cave paintings and etchings on every continent that ancient humans inhabited – but how many times was it invented over human history?

Rock art is a truly global phenomenon, with discoveries of cave paintings and etchings on every continent that ancient humans inhabited – but how many times was it invented over human history?

In 2029, the Landolt satellite launched into Earth's orbit will serve to calibrate telescopes on Earth.

Soviet-era cosmonaut Vyacheslav Zudov, whose failed Soyuz 23 docking with Russia's Salyut 5 space station ended with the first and only emergency splashdown on board a Soyuz spacecraft, has died.

The return of Boeings 1st crewed Starliner mission has been delayed to June 22.

Will future humans use warp drives to explore the cosmos? We’re in no position to eliminate the possibility. But if our distant descendants ever do, it won’t involve dilithium crystals, and Scottish accents will have evaporated into history by then.

Warp drives have their roots in one of the most popular science fiction franchises ever, but they do have a scientific basis. A new paper examines the science behind them and asks if a warp drive containment failure would emit detectable gravitational waves.

The paper is titled “What no one has seen before: gravitational waveforms from warp drive collapse.” The authors are Katy Clough, Tim Dietrich, and Sebastian Khan, physicists from institutions in the UK and Germany.

There’s room for warp drives in General Relativity, and Mexican physicist Miguel Alcubierre described how they could theoretically work in 1994. He’s well-known in space and physics circles for his Alcubierre Drive.

Everyone knows that no object can travel faster than the speed of light. But warp drives may offer a workaround. By warping spacetime itself, a spacecraft with a warp drive wouldn’t be breaking the faster-than-light (FTL) rule.

“Despite originating in science fiction, warp drives have a concrete description in general relativity, with Alcubierre first proposing a spacetime metric that supported faster-than-light travel,” the authors write.

There are clear scientific barriers to actually making a warp drive. But it’s possible to simulate how one would work and how they may be detectable via gravitational waves in the event of a failure. Warp drives distort spacetime itself, just like binary mergers of compact objects like black holes and neutron stars. It’s theoretically possible that they emit a gravitational wave signal in the same vein as mergers. “To search for such signals and to correctly identify them in the measured data, it is important to understand their phenomenology and properties,” the authors explain.

It begins with understanding how warp drives might work, and for that, we have to delve deeply into physics.

“The principle idea behind a warp drive is that instead of exceeding the speed of light directly in a local reference frame, which would violate Lorentz invariance, a “warp bubble” could traverse distances faster than the speed of light (as measured by some distant observer) by contracting spacetime in front of it and expanding spacetime behind it,” the paper states.

The first barrier is that warp drives require a Null Energy Condition (NEC). Physics states that a region of space cannot have a negative energy density. There are theoretical workarounds for that, but for now, none of them are practical.

“Other issues with the warp drive metric include the potential for closed time-like curves and, from a more practical perspective, the difficulties for those in the ship in controlling and deactivating the bubble,” the authors explain. This is because there would be no way for the crew to send signals to the front of the ship. It’s difficult for events inside the bubble to influence events outside the warp bubble, as this paper explains.

“From the perspective of simulating the warp drive dynamically, the key challenge is stability,” the authors explain. Equations show that the Alcubierre Drive can initiate a warp bubble using the Einstein Equation, but no known equations can sustain it. “There is (to our knowledge) no known equation of state that would maintain the warp drive metric in a stable configuration over time. Therefore, whilst one can require that initially, the warp bubble is constant, it will quickly evolve away from that state, and, in most cases, the warp fluid and spacetime deformations will disperse or collapse into a central point.”

Though instability is a prime obstacle to warp drives, it’s also what could make them detectable. If an Alcubierre Drive achieves a constant velocity, it’s not detectable. It generates no gravitational waves and has no ADM mass. ADM stands for Arnowitt–Deser—Misner, named for three physicists. I’ll leave it to curious readers to read more about ADM mass.

But the warp drive is only undetectable if it’s constant and stable. Once it breaks down, accelerates or decelerates, it could be detectable. In their work, the authors allow the warp drive bubble to collapse. “Physically, this could be related to a breakdown in the containment field that the post-warp civilization (presumably) uses to support the warp bubble against collapse,” they write.

In their formulations, the nature of the ship itself isn’t important. Only the warp bubble and the warp fluid inside are significant.

The researchers simulated the breakdown of the warp bubble. They found that the collapse generated gravitational waves with characteristics different from those generated by mergers. “The signal comes as a burst, initially having no gravitational wave content, followed by an oscillatory period with a characteristic frequency of order 1/[R],” they write. “Overall, the signal is very distinct from the typical compact binary coalescences observed by gravitational wave detectors and more similar to events like the collapse of an unstable neutron star or the head-on collision of two black holes.”

The authors point out that though the warp drive creates a GW signal, it’s outside the frequency range of our current ground-based detectors. “Proposals for higher frequency detectors have been made, so in the future, one may be able to put bounds on the existence of such signals,” they write.

The ship itself could also send some type of multimessenger signal, but it’s difficult to know how the ship’s matter would interact with regular matter. “Since we do not know the type of matter used to construct the warp ship, we do not know whether it would interact (apart from gravitationally) with normal matter as it propagates through the Universe,” the researchers explain.

This is a fun thought experiment. It’s possible that some type of workaround to FTL travel will exist one day in the distant future. If it does, it may be related to a better understanding of dark matter and dark energy. If any ETIs exist, they may be in a position to exploit fundamental knowledge of the Universe that we don’t yet possess.

If they’ve figured out how to construct and use a warp drive, even with all of its seeming impossibilities, their activities might create gravitational waves that our future observatories could detect, even in other galaxies. But for now, it’s all theoretical.

“We caution that the waveforms obtained are likely to be highly specific to the model employed, which has several known theoretical problems, as discussed in the Introduction,” the authors write in their conclusion. “Further work would be required to understand how generic the signatures are and properly characterize their detectability.”

Without a doubt, some curious physicists will continue to work on this.

The post Warp Drives Could Generate Gravitational Waves appeared first on Universe Today.

China has revealed details about a miniature rover tucked away on the country's pioneering Chang'e 6 lunar far side sample-return mission.