Thursday, July 27, 2023

Have We Seen the First Glimpse of Supermassive Dark Stars?

A recent study published in the Proceedings of the National Academy of Sciences (PNAS) examines what are known as dark stars, which are estimated to be much larger than our Sun, are hypothesized to have existed in the early universe, and are allegedly powered by the demolition of dark matter particles. This study was conducted using spectroscopic analysis from NASA’s James Webb Space Telescope (JWST), and more specifically, the JWST Advanced Deep Extragalactic Survey (JADES), and holds the potential to help astronomers better understand dark stars and the purpose of dark matter, the latter of which continues to be an enigma for the scientific community, as well as how it could have contributed to the early universe.

“Discovering a new type of star is pretty interesting all by itself but discovering it’s dark matter that’s powering this—that would be huge,” said Dr. Katherine Freese, who is a professor in the Department of Physics at The University of Texas at Austin (UT Austin), and a co-author on the study.

The dark star candidates designated JADES-GS-z13-0, JADES-GS-z12-0, and JADES-GS-z11-0 are estimated to have existed between approximately 320 million to 400 million years after the Big Bang. They were initially identified as potential galaxies, and the sizes of these candidates are estimated to be approximately 1 million times more massive than our Sun and 1 billion times brighter, as well.

There are ongoing hypotheses regarding the first generations of star types that inhabited the universe right after the Big Bang, neither of which have ever been observed: hydrogen burning Population III stars and dark stars. However, like all scientific discoveries, follow-up observations by JWST are required to confirm these findings. If these candidates are confirmed to be dark stars, they could challenge present cosmological models of the universe based on recent JWST observations that early galaxies are larger than they should be.

“It’s more likely that something within the standard model needs tuning, because proposing something entirely new, as we did, is always less probable,” said Dr. Freese. “But if some of these objects that look like early galaxies are actually dark stars, the simulations of galaxy formation agree better with observations.”

Like most scientific studies, this one began more than 15 years ago with a conversation between Dr. Freese and a colleague, Dr. Douglas Spolyar, who was a PhD student at the University of California, Santa Cruz at the time, about the potential correlation between dark matter and the first stars of the universe. The two eager scientists contacted Dr. Paolo Gondolo, who was an astrophysicist at the University of Utah, and culminated in a 2008 study published in Physical Review Letters, with several more studies about the potential for dark stars being published since then.

“We predicted back in 2012 that supermassive dark stars could be observed with JWST,” said Dr. Cosmin Ilie, who is an assistant professor of physics and astronomy at Colgate University, and lead author of the paper. “As shown in our recently published PNAS article, we already found three supermassive dark star candidates when analyzing the JWST data for the four high redshift JADES objects spectroscopically confirmed by Curtis-Lake et al, and I am confident we will soon identify many more.”

What new discoveries will scientists make about dark stars in the coming years and decades? Only time will tell, and this is why we science!

As always, keep doing science & keep looking up!

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NASA and DARPA Award Contract for a Nuclear Engine to Lockheed Martin

NASA plans to send astronauts to Mars in the coming decade. This presents many challenges, not the least of which is the distance involved and the resulting health risks. To this end, they are investigating and investing in many technologies, ranging from life support and radiation protection to nuclear power and propulsion elements. A particularly promising technology is Nuclear-Thermal Propulsion (NTP), which has the potential to reduce transit times to Mars significantly. Instead of the usual one-way transit period of six to nine months, a working NTP system could reduce the travel time to between 100 and 45 days!

In January of this year, NASA and the Defense Advanced Research Projects Agency (DARPA) announced that they were launching an interagency agreement to develop a nuclear-thermal propulsion (NTP) system – known as the Demonstration Rocket for Agile Cislunar Operations (DRACO). Just yesterday, DARPA announced that it had finalized an agreement with Lockheed Martin to design and build a prototype NTR system – the Experimental NTR Vehicle (X-NTRV) – that will be sent to space for testing by 2027.

The announcement was followed by a live media teleconference held by NASA and DARPA at 01:00 PM EDT (10:00 AM PDT) on Wednesday, July 26th. The teleconference was live-streamed on NASA’s website and featured an expert panel discussing the latest developments in the DRAGO program and fielding questions from various media outlets. The panel consisted of four members, including:

  • Dr. Anthony Calomino, space nuclear technologies portfolio manager, NASA
  • Dr. Tabitha Dodson, DRACO program manager, DARPA
  • Kirk Shireman, vice president, Lockheed Martin Lunar Exploration Campaigns
  • Joe Miller, president, BWXT Advanced Technologies

Nuclear Propulsion

Nuclear propulsion concepts generally fall into two categories: nuclear electric and nuclear thermal propulsion (NEP/NTP). NEP concepts consist of a nuclear reactor generating power for a Hall-Effect thruster, which uses electromagnetic fields to ionize and accelerate inert gas (like xenon) to generate thrust. Conversely, NTP involves a nuclear reactor heating liquid hydrogen or deuterium, then channeling the rapidly-expanding gas through nozzles to generate thrust. While no NEP concepts have been realized to date, experiments involving NTP go back to the Space Age.

In NASA’s case, these efforts resulted in the creation of the Nuclear Engine for Rocket Vehicle Application (NERVA), which was successfully tested between 1961 and 1969. With the closing of the Apollo Era, efforts to further develop the technology and integrate it into a spacecraft were shelved. This reflected the changing budget environment and new priorities, which included the Space Shuttle program and the development of space stations. In 2017, with crewed missions to Mars on the horizon, NASA reignited its NTP program.

In addition to improved efficiency, nuclear thermal propulsion systems have a virtually unlimited energy density, significantly reducing the propellant needed. This eliminates the need for orbital refueling or fabricating propellant on Mars for the return journey. Since the majority of a chemical rocket’s mass consists of its propellant and large propellant tanks, it also means that future spacecraft will be less massive and cumbersome. Moreover, NTP engines also enable abort scenarios on journeys to Mars that are impossible using chemical propulsion systems.

The DRACO project represents the fruition of these efforts, focusing on more efficiently and quickly transporting payloads and crews through cislunar space and, eventually, to Mars. As Dr. Tabitha Dodson, the DRACO program manager for DARPA, indicated in an agency press release:

“The DRACO program aims to give the nation leap-ahead propulsion capability. An NTR achieves high thrust similar to in-space chemical propulsion but is two-to-three-times more efficient. With a successful demonstration, we could significantly advance humanity’s means for going faster and farther in space and pave the way for the future deployment for all fission-based nuclear space technologies.”

Kirk Shireman, vice president of Lunar Exploration Campaigns at Lockheed Martin Space, said in a separate Lockheed Martin press release:

“These more powerful and efficient nuclear thermal propulsion systems can provide faster transit times between destinations. Reducing transit time is vital for human missions to Mars to limit a crew’s exposure to radiation. This is a prime technology that can be used to transport humans and materials to the Moon. A safe, reusable nuclear tug spacecraft would revolutionize cislunar operations. With more speed, agility and maneuverability, nuclear thermal propulsion also has many national security applications for cislunar space.”

Old Idea, New Fuel

The DRACO program leverages advances achieved through the NERVA program but relies on a new fuel known as High-Assay Low-Enriched Uranium (HALEU). Compared to conventional uranium fuel, which relies on 5% enrichment with Uranium-235 – the main fissile isotope that produces energy during fission reactions – HALEU fuel is enriched between 5% and 20%. This allows for smaller reactors, more power per unit of volume, and the optimization of reactors for longer core life, increased efficiency, and better fuel utilization.

The use of HALEU fuel was made possible through the National Security Presidential Memorandum 20 (NSPM-20) issued in August 2019, which updated U.S. policy regarding nuclear power and propulsion in space. The U.S. Department of Energy (DoE) will provide the HALEU metal, which will be converted into fuel by BWX Technologies (BWXT), a leading supplier of nuclear components and fuel to the U.S. government and one of Lockheed Martin’s partners for the DRACO program. This Virginia-based company will also manufacture the nuclear reactor that will power the X-NTRV.

“The award of this contract further demonstrates BWXT’s ability to design, manufacture and deploy nuclear reactors and fuel on a scale that is unmatched elsewhere in the world today,” Joe Miller, president of BWXT Advanced Technologies LLC, said in a company press release. “This partnership with Lockheed Martin working for DARPA adds another important dimension to BWXT’s already-impressive line-up of nuclear reactor designs for commercial and defense applications.”

DARPA also indicated it would engineer the system so the reactor remains “cold” (switched off) until it reaches its designated orbit. As Dr. Dobson explained during the teleconference:

“The Draco program upfront sets very clear rules and guidelines which hopefully can help to take a variety of programmatic and technical questions off the table. For instance, we are never turning the reactor on, on the ground. Therefore, transportation and watch site operations are all greatly simplified because a reactor that has never been turned on is cold and benign. You can put your hand right inside the core and touch the fuel like you would any other heavy metal.”

The Test

The development of the DRACO thruster will be conducted primarily at BWXT’s Mt. Athos Road complex near Lynchburg, Virginia. Once the reactor is complete and integrated into the X-NTRV, the U.S. Space Force will launch the vehicle to High Earth Orbit (HEO). As Dr. Dobson indicated, this will likely involve a commercial launch vehicle from NASA’s Kennedy Space Center in Cape Canaveral, Florida, depending on how far into space they decide to send it.

“We’re looking at launching out of the Cape, and it will require a heavy lift vehicle,” she said. “Although that would be nice to have if, for some reason, we needed to [launch] it to a much higher orbit. But at this point, we’re looking at just an NSSL [National Security Space Launch] with a standard fairing – not a heavy lift. So Falcon 9 or Vulcan Centaur.”

According to Dr. Calamino, the vehicle will carry an estimated 100 kg (220 lbs) of HALEU fuel in its core and about 2000 kg (4400 lbs) of hydrogen propellant. The panel also addressed some key concerns regarding the safety of the upcoming test and the issue of radiation hazards. In particular, there was the question of what might happen if there is a mishap during launch or an accident in orbit, resulting in debris falling to Earth. As Dr. Calamino explained, the NTP reactor will be much safer than a fission system that relies on uranium-235 or plutonium:

“Fission systems are not radioisotope systems; they’re very very much different. Radioisotope systems are radioactive from the time that they are prepared to go into an electric generator all the way up to when they’re incorporated into the payload and sitting on the launch pad. Plutonium is just basically a radioactive material. Uranium-239, without it having been fissioned and actually being surrounded by fission products, is basically a metal.

“It is safe to work around. It is safe to be around. It doesn’t need the protection measures that need to be a place for plutonium. If you have a mishap during launch or on the launchpad itself, there is the debris that would potentially be generated by that, isn’t any worse than the debris that would be produced by the turbo machinery that might also be dispersed in such an accident or placed anywhere else. It is not a radioactive material at that point in time.”

Another safety measure NASA and BWXT are considering is inserting “poison wires” and systems in the reactor to prevent it from going critical. This refers to neutron-absorbing materials often used in reactors to lower the high reactivity of their fuel load if the reactions become unstable. The combination of these elements, said Dr. Calamino and Miller, will prevent the contamination of Earth’s atmosphere and any biosphere the vehicle encounters should something go wrong during the test.

Artist’s concept of a Lockheed Martin design for a DRACO nuclear-powered demonstration spacecraft. Credit: Lockheed Martin.

When NASA inaugurated its “Journey to Mars” program in 2010, it envisioned a Deep Space Transport (DST) that would ferry crews between the proposed Lunar Gateway and a similar station orbiting Mars using a 500-kilowatt (kWe) Solar Electric Propulsion (SEP) system. Unfortunately, there have since been delays with the development of the Space Launch System (SLS) and other mission elements and complications imposed by parallel programs (the Artemis Program). Because of this, there are legitimate fears that NASA will not be ready to conduct crewed missions to Mars by 2033, as originally hoped.

The realization of a nuclear thermal propulsion system is seen as one of two possible solutions to these problems – the other being an “orbit-only” mission architecture. In addition to enabling rapid transits to Mars and back, it would also allow for greater flexibility. Instead of launching every 26 months when Earth and Mars are closest to each other (a “Mars Opposition“), it could be possible to send missions during a “Mars Conjunction.” The reduced transit would also reduce the amount of radiation crews would be exposed to and the time spent in microgravity (the two greatest health hazards of a crewed Mars mission).

Beyond Mars, nuclear-thermal, nuclear-electric, and systems that combine both (bimodal propulsion) will enable missions to the Main Asteroid Belt, Venus, and other deep-space destinations, effectively expanding the reach of human-rated exploration. It will also enable shorter transits for robotic explorers destined for the outer Solar System, drastically increasing the rate of scientific returns. There has been some doubt that the technology will be ready in time. But if the X-NTRV test is successful and completed on schedule, NASA may have an NTP system ready for the 2033 launch window.

Further Reading: DARPA, Lockheed Martin

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Senseless Vandalism Damages Canadian Observatory

The Royal Astronomical Society of Canada’s observatory in Hamilton, Ontario was vandalized earlier this month, with at least $100,000 in damage to equipment and facilities.

Security video shows two people using a truck to repeatedly ram into two buildings – the observatory and a meeting center — knocking down exterior walls on both buildings and damaging telescopes and other equipment inside. Nothing was stolen, but damaged for no apparent reason.

“It appears to be a failed robbery turned utter vandalism,” said the group’s president Andy Blanchard. “It looked like they wanted to destroy everything.”

Blanchard told Universe Today that another member of the group discovered the damage on July 4, 2023 when he went out to the center to do some maintenance. He first saw that a heavy-duty entrance gate had been ripped out of the ground, but that was only the start.

“It was shocking and upsetting and it took us about 3-4 hours to manage to get into the clubhouse building to access to security video,” Blanchard said “On that video we saw they backed their truck into the observatory wall three times to knock it down, and they spent 5 minutes in the building, doing further damage to our equipment, such as throwing eyepieces to the floor. Then they used their truck to knock down the walls on our meeting and warming center, but the wall collapsed in a way that they couldn’t enter the building.”

Damage to the Hamilton Observatory’s meeting center after vandalism on July 3, 2023. Image courtesy Victor Abraham/ Hamilton Centre.

The police say the two perpetrators are known and are being sought in connection with this and several other break-ins and acts of vandalism in the area in southern Ontario.

The Hamilton Centre of the RASC is one of 28 non-profit centers across Canada, powered by over 140 astronomy enthusiast members. The Hamilton group was originally founded 1901, and is one of the longest standing amateur astronomy organizations in Canada.

When the wall on the observatory was knocked down, it crushed a CGE Pro mount from Celestron, hurling the mounted telescope, worth at least $11,000 USD, across the room. In total, the astronomical equipment damaged is valued at more than $40,000 USD.

Blanchard said that’s a substantial amount for a group of volunteers that are doing a public service by sharing the wonders of the night sky with their community.  

The Hamilton Observatory and meeting center before the damage. Image courtesy Victor Abraham/ Hamilton Centre.

“It was basically several decades worth of collection and work,” Blanchard said. “The biggest problem is that when the wall came down, the lime dust from the concrete walls settled on all the astronomical surfaces, and lime is very caustic to the expensive coatings on the eyepieces and optics. All have to be sent away for repair.”

The group has started a GoFundMe page, and club member Jeff Parsons said their story seems to have struck a cord, “evidenced by the growing outpouring of support and generosity from not just the local community but the broad astronomy community.”

Blanchard said they’ve been overjoyed with the support they’ve received, with both cash donations, as well as of offers for help with reconstruction of their buildings.

“It’s a wonderful feeling to get such support from around the world,” Blanchard said. “Many times, you don’t realize you are part of a community until that community comes together for support. We are very proud of our community and all the people who are stepping up and saying they want to help.”

But the group has also received offers of substantial donations, such as an observatory and other astronomical equipment. Additionally, a recognized member of the Canadian astronomy community offered to donate a 36″ telescope, valued at about $85,000.

“This is such a rare, extraordinary opportunity, and we are overwhelmed,” Blanchard said. “To look through this telescope, you need to climb a 12-foot ladder. Plus, with the size of this telescope, you can see colors in space, where typically when you look through a regular telescope, everything is in shades of grey. I’m sure we will have line-ups around the block to look through this telescope.”

They are using the GoFundMe to purchase a sea-can shipping container to hold all the equipment that survived the break in while their buildings are repaired or rebuilt. The group is still awaiting word on how much their insurance will cover.

The Hamilton group regularly holds public viewing events and they didn’t let the vandalism stop them from holding their usual weekly observing events.

“We decided we weren’t going to let this tragedy stop us and we’ve had more people than ever come out to look through our members’ telescopes,” Blanchard said. “The community has come together in ways we never would have dreamed possible.”

For more information, see the group’s GoFundMe page and the group’s website.

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Wednesday, July 26, 2023

A Gamma Ray Burst Lasted So Long it Triggered a Satellite Twice

Gamma Ray Bursts (GRBs) are the most powerful astrophysical phenomena in the universe. For a span of seconds to a few minutes, they can be the most powerful high-energy event in the sky, shining across billions of light years. But recently astronomers detected a GRB that lasted more than a thousand seconds, with two blasts of gamma rays that triggered the Fermi Gamma Ray Burst Monitor. It’s such a strange cosmic event that astronomers aren’t sure what caused it, but they do have a possible idea.

Gamma Ray Bursts are difficult to study because they are so short-lived. They were first detected by the Vela satellites, which were designed to detect nuclear tests during the cold war. It was only years after their detection that they were declassified.

While their flash of gamma-ray energy is short-lived, GRBs also emit an afterglow that can be seen in radio and other wavelengths. So we have some ideas about their source. Most of them occur billions of light-years from Earth and are likely caused by the death of extremely massive stars. The burst of gamma rays is emitted when the star collapses to form a black hole. Some GRBs may also be caused when neutron stars collide to create a black hole. It’s the extreme gravitational collapse that powers GRBs, but this also means their highest energy bursts are short-lived. So how could one possibly last for more than 15 minutes?

Based on observations of the afterglow, the progenitor star isn’t likely to have been something strange or exotic. The afterglow pattern is consistent with other minutes-long GRBs. So it’s only the length and double-burst nature of the GRB that’s unusual. And that may be the key to understanding it. One possibility is that the GRB was gravitationally lensed by a massive object.

Gravitational lensing occurs when light from a distant object is gravitationally warped by a galaxy or other object between us and the distant object. This would focus the GRB light, making it appear bright for a longer period of time. Gravitational lensing can also create multiple images of an object. For example, light from a supernova can be lensed along different paths around a galaxy, letting us see the flash of light several times over the course of decades. A smaller lensing effect could explain why we saw two gamma-ray flashes. They could be the same GRB light lensed along different paths.

We’d need to observe similar strange GRBs to fully understand the cause, but this does show that the diversity of GRBs is broader than we thought. These powerful events still have lots to tell us about the cosmos.

Reference: de Wet, S., et al. “The ultra-long GRB 220627A at z= 3.08.” arXiv preprint arXiv:2307.10339 (2023).

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Witnesses Play Up the Alien Angle at Congressional UFO Hearing

Three former insiders who have played a role in dealing with UFOs — or as they’ve now come to be known, unidentified anomalous phenomena — say the U.S. military knows more than what it’s been telling lawmakers about encounters with potentially alien technology.

During a House subcommittee hearing held today, one of the witnesses said he was told that non-human remains have been recovered from UAP incidents.

“As I’ve stated publicly already … biologics came with some of these recoveries,” David Grusch, a former intelligence officer who took on whistleblower status due to his claims, said in response to a question from Rep. Nancy Mace, R-S.C.

“Were they, I guess, human or non-human biologics?” Mace asked.

“Non-human,” Grusch replied. “And that was the assessment of people with direct knowledge on the program I talked to, that are currently still on the program.”

Much of what Grusch had to say, including his controversial claims about non-human technology and recoveries, was said earlier in a News Nation interview. That interview was frequently referenced during today’s hearing before the House Oversight subcommittee on national security, the border and foreign affairs — so much so that the interview was entered into the hearing record. But this time, Grusch made his statements under oath.

The claims seem to run counter to statements made during a Senate committee hearing in April by Sean Kirkpatrick, director of the Pentagon’s All-domain Anomaly Resolution Office, or AARO. “AARO has found no credible evidence thus far of extraterrestrial activity, off-world technology, or objects that defy the known laws of physics,” Kirkpatrick said in April.

In a statement emailed to Fox News Digital and other media outlets, the Department of Defense said it “takes public interest in UAP seriously.”

“The department is fully committed to openness and accountability to the American people, which it must balance with its obligation to protect sensitive information, sources and methods. DoD is also committed to timely and thorough reporting to Congress,” the statement read.

“AARO has established a safe and secure process for individuals to come forward with information to aid AARO in its congressionally mandated historical review. AARO welcomes the opportunity to speak with any former or current government employee or contractor who believes they have information relevant to the historical review.”

Tech and the Tic Tac

The two other witnesses at the hearing — former Navy pilot Ryan Graves and retired Navy Cmdr. David Fravor — didn’t go as far as Grusch did in discussing the possibility of alien involvement. But they said the flight characteristics they saw during UAP encounters seemed to reflect technologies far beyond the capabilities of the U.S. military or its rivals.

Fravor, who was involved in the “Tic Tac” encounter that occurred off the California coast in 2004, said what he experienced was “well beyond the materials science and the capabilities that we had at the time, that we have currently, or that we’re going to have in the next 10 to 20 years.”

During that encounter, pilots tracked what the Navy said was a 46-foot-wide object that looked smooth and rounded like a Tic Tac breath mint. “For some people that can’t know what a Tic Tac is, it’s a giant flying propane tank,” Fravor said.

The object appeared to move evasively, jam the jets’ radar and zoom off at a high speed. “It’s been said it’s probably the most credible UFO sighting in history, based on all the sensors that were tracking it,” Fravor told the subcommittee.

Graves, who encountered UAPs during his time as a Navy pilot and now heads an advocacy group called Americans for Safe Airspace, said other eyewitnesses have described “a dark gray or black cube in a clear sphere.”

“UAP are in our airspace, but they’re grossly underreported,” he said. “Parts of our government are aware of more about UAP than they let on. The excessive classification practices keep crucial information hidden.”

Decades of secrecy

Grusch, who coordinated work on the UAP issue in intelligence roles for the Air Force, the National Reconnaissance Office and the National Geospatial-Intelligence Agency, said his research suggested that the U.S. government was aware of extraterrestrial connections to UFOs as far back as the 1930s.

In response to a question from Rep. Tim Burchett, R-Tenn., Grusch said he had personal knowledge about injuries that were sustained by people trying to reverse-engineer UAP technologies.

“How were they injured?” Burchett asked. “Was it something like a radioactive-type situation, or something we didn’t understand? I’ve heard people talk about Havana syndrome type incidents. What was your recollection of that?”

“I can’t get into specifics,” Grusch replied, “but you could imagine assessing an unknown unknown. There’s a lot of potentialities you can’t fully prepare for.”

He said the most sensitive work on UAPs has been kept secret, even from members of Congress, through compartmentalization in special access programs.

“How does a program like that get funded?” Rep. Jared Moskowitz, D-Fla., asked Grusch.

“I will give you generalities,” Grusch said. “I can get very specific in a closed session, but [it’s] a misappropriation of funds.”

Grusch repeatedly declined to name names in open session, but he said he’d be willing to share what he knows in a secure classified setting. Some subcommittee members said they ran into difficulties when they tried to make such arrangements with intelligence officials.

All three witnesses said UAPs had the potential to pose an existential threat to U.S. national security.

“In the event that your encounters had become hostile, would you have had the capability to defend yourself, your crew, your aircraft?” Rep. Andy Ogles, R-Tenn., asked Graves and Fravor.

“Absolutely not,” Graves said. “No,” Fravor added.

Lawmakers plan action

All three witnesses also said there had to be a better centralized system for receiving and processing UAP reports — not only from military pilots, but also from commercial pilots and the general public. “It’s a travesty that we don’t have a system to correlate this and actually investigate,” Fravor said.

Rep. Robert Garcia, D-Calif., said “one of the clear outcomes of this hearing already is that there has to be a safe and transparent reporting process for pilots.” Subcommittee Chairman Glenn Grothman, R-Wis., agreed, saying that he assumed “some legislation will come out of this.”

“I think we’re going to want to look into what we can do to make more of this information public,” Grothman said.

Skepticism came to the surface only once during the hearing. “The concept that an alien species is technologically advanced enough to travel billions of light-years gets here and somehow is incompetent enough to not survive Earth or crashes is something that I find a little bit farfetched,” Rep. Eric Burlison, R-Mo., told Grusch. “And with that being said, you have said that there’s interdimensional potential. Could you expound on that?”

In reply, Grusch said that no matter how advanced a civilization becomes, a “small percentage” of sorties are going to end in mission failure. And on the interdimensional question, Grusch referred to the holographic principle — which is a way-out hypothesis on the frontiers of string theory.

“You can be projected from higher dimensional space to lower dimensional,” Grusch explained.

“But you have not seen any documentation that that’s what’s occurring,” Burlison asked.

“Only a theoretical framework discussion,” Grusch answered.

Outside the hearing chamber, the skepticism was sharper. “The KGB is having a banner day in Congress today,” investigative journalist Dave Troy said in a tweet. “This is such a disgraceful abuse of this institution.”

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One Year of JWST. Ultimate Recap

It’s already been one year of operations for James Webb. We accumulated all the major scientific results, all the amazing images and spectra, all the important discoveries and controversies. Enjoy the ultimate recap of JWST’s first year.

It was full of events. There hardly is any other mission that generated so many news stories in such a short period of time. So, here’s a structured look-back at all the major things that came out from JWST.

If you weren’t following all of them in real-time, this is a great way to catch up with the most powerful space telescope in human history.

If you are a regular viewer of Space Bites and a Newsletter subscriber, it’s still great to have a retrospective of all the things that came from Webb. So, I’m sure you’ll also enjoy it.

James Webb is already set for Cycle 2. Let’s hope there will be many more recaps like this one in the future.

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Tuesday, July 25, 2023

Astronomers Have a New Trick to Work out the Age of Stars

Twinkle, twinkle little star, I wonder just how old you are.

It isn’t an easy question to answer. Stars are notoriously difficult to age. We know the age of the Sun because we happen to live on one of its orbiting rocks, and we know very well how old the rock is. Without that information, things become a bit more fuzzy. But that could change thanks to a new study.

We do know a few broad rules about determining the age of a star. For example, generally the higher the metallicity of a star the younger it is. And main sequence stars like the Sun tend to get hotter as they age, so if two stars have the same mass and composition, the hotter of the two is likely the older. But by themselves, these general rules aren’t enough to get a precise age determination. For that, we typically look at clusters of stars.

Star clusters such as open clusters and globular clusters generally form within a single molecular cloud, and they do so around the same time. When you look at the stars in a cluster you know they are all around the same age. Astronomers can use this fact to get a good age for star clusters. Individually there will be variations in things like metallicity and temperature, but statistically, the average age determination is a good measure of the cluster’s age.

But one thing that has been noticed is that among star clusters, older clusters have stars that rotate more slowly than stars in young clusters. This suggests that a star’s rotation rate slows down as it ages. This would be a great way to determine stellar age because many stars have starspots, which we can use to measure rotation pretty easily. There are just two problems. The first is that within a cluster stars can be gravitationally bound, and this interaction might be driving the slowdown. If so, then individual stars wouldn’t experience the same rotational decay. The second is that the metallicity of a star affects its density and temperature, so metallicity could have a significant effect on the slowdown rate.

Star cluster age (lines) vs binary star age (circles/diamonds). Credit: Gruner, et al

Still, the technique would be so useful that a team wanted to explore it further. They looked at 300 wide binary stars. These are binary stars with orbital distances large enough that their rotations are independent of each other. And since binary systems form all at once, the team could be confident that binary pairs were the same age.

The team then applied the cluster method of using temperature and rotation rate to determine the age of each star in a pair. They found that the ages of binary pairs matched using this method. And with 300 samples to work with, they are confident the method works. The team also found the approach worked regardless of the metallicity of the stars. So while metallicity might have a small effect on stellar age, the rotation approach works all the same.

From this work, astronomers can feel confident in using rotation as an age measure regardless of whether a star is single, binary, or part of a cluster. This is great news. Telescope satellites such as Gaia and the upcoming PLATO mission have the search for exoplanets as part of their mission. The same method used to find the dip in stellar brightness as an exoplanet transits can also be used to measure the rotational rate of a star through starspots. In time could know the age of billions of stars as well as their motion and whether they have planets.

Reference: Gruner, D., S. A. Barnes, and K. A. Janes. “Wide binaries demonstrate the consistency of rotational evolution between open cluster and field stars.” Astronomy & Astrophysics 675 (2023): A180.

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