Stellar Encounters: A Second Collision of Galaxy Giants

[00:00:00] This is Space Time series 28 episode 71, broadcast on the 13th of June 2025. Coming up on Space Time, two massive galaxy clusters on course for a collision, NASA forced to switch to backup systems on its Saki spacecraft, and the discovery of a new type of atomic nucleus. All that and more coming up on Space Time. Welcome to Space Time with Stuart Gary.

[00:00:44] Astronomers have captured a rare cosmic event in which two massive galaxy clusters, which have already collided with each other once, are now poised to head back into each other for another go. Galaxy clusters are some of the largest known structures in the universe. Held together by gravity, they're monster-sized collections of hundreds, sometimes thousands of individual galaxies, as well as massive amounts of super-heated gas and of course lots of invisible dark matter.

[00:01:10] The cluster involved in this collision, categorised as PSZ2 G181.06 plus 48.47, is about 2.8 billion light-years away. Previous radio observations by LOFAR, the Low Frequency Array and Antenna Network in the Netherlands, spotted parenthesis-shaped structures on the outskirts of the system.

[00:01:30] Now, new observations using NASA's Earth-orbiting Chandra and ESA's XMM-Newton X-ray space telescopes, combined with LOFAR data and an optical image from the PanSTARRS telescope, to capture far more detailed images of these spectacular colliding galaxy clusters. The new observations reported in the Astrophysical Journal show massive structures, probably shock fronts, similar to those created by jets that have broken the sound barrier, are likely caused by the disruption of gas from the initial collision about a billion years ago.

[00:01:59] Now, since that collision, they've continued travelling outwards and are currently separated by about 11 million light-years. That's the largest separation for these kinds of structures that astronomers have ever seen. And the new data is providing evidence that these two clusters are poised for another collision. Having a first pass at ramming each other, the two clusters have now slowed down, and they've begun heading back for a second crash.

[00:02:23] Astronomers made a detailed study of the X-ray observations from this collision site, and they've found three shock fronts. These align with the axis of the collision, and the authors think they're early signs of what's likely to be a second oncoming crash. Astronomers are still trying to determine just how much mass each of the colliding clusters contains. Regardless, the total mass of the system is less than others where galaxy clusters have collided, and that makes this an unusual case for a low-mass system involved in a rare event of colliding galaxy clusters.

[00:02:53] Something worth looking at. This is Space Time. Still to come, NASA switches to backup systems on its Psyche spacecraft, and the discovery of a new type of atomic nucleus. All that and more still to come, on Space Time.

[00:03:24] Engineers with NASA's Psyche mission have been forced to switch to a backup fuel system aboard the spacecraft, following a decrease in fuel pressure detected in the probe's main propulsion system. The spacecraft's thrusters shut down at the beginning of April, after pressure fell in a line feeding Xeon propellant to the system. Powered by two large solar arrays, Psyche's thrusters ionize and expel Xeon gas to gently propel the spacecraft, which gradually picks up speed during its journey.

[00:03:50] The team paused the four electric thrusters in early April, in order to investigate the unexpected drop in pressure. They've now identified a mechanical issue with one of the valves, which opens and closes to manage the flow of propellant. Mission managers say a component inside one of the valves has failed, and it's now obstructing the flow of Xeon to the thrusters. After investigating a range of options, NASA's decided to swap to the backup fuel system lines.

[00:04:14] Now that the swap to the backup fuel system has been completed, engineers will command the spacecraft's thrusters to resume firing. The spacecraft was designed with a redundant backup propellant line that's identical to the primary system. As a precaution, engineers plan to keep the backup lines valve in the open position in order to ensure the propellant flow and avoid any potential further mechanical issues in the future. Right now, the orbiter remains on course to reach its target, the asteroid Psyche, as planned in August 2029.

[00:04:44] The spacecraft was launched from NASA's Kennedy Space Center in Florida in October 2023, and it's already flown well over a billion kilometers. In May next year, Psyche will fly past Mars, using the planet's gravity as a slingshot to help speed the probe towards the metal-rich asteroid it was meant to explore. Located in the main asteroid built between Mars and Jupiter, 16 Psyche is a large M-type asteroid discovered way back in 1852. It's fascinated astronomers ever since.

[00:05:14] It's the largest and most massive of the M-type asteroids, and one of the dozen most massive known space rocks with a diameter of some 220 kilometers. It was originally thought to be the exposed iron core of a protoplanet, the remnants of a violent collision with another object that stripped off the mantle and crust. But recent observations are casting doubt on that hypothesis. When the Psyche spacecraft reaches the asteroid in 2029, it'll provide a fresh light into the asteroid's origins.

[00:05:45] The spacecraft will orbit Psyche for 20 months, studying its topography, its surface features, its gravity, magnetism and its composition. This report from NASA TV. When I was a little kid, I thought I wanted to be an astronomer. I took a geology class and there was just something about having a rock in your hand, something you could hold and feel. I thought, you know, we have rocks from outer space, maybe I'll study those. I study meteorites. I love meteorites. It's like an addiction for me.

[00:06:13] Because I love exploring the solar system through understanding these rocks and the places they come from. Life on Earth exists on two heat engines. One is the sun, but the other is the heat engine below our feet. That drives the movement of the plates. It drove the differentiation of the planet. We've known for two centuries that our core was made of metal, but we haven't been able to explore. We can't drill a hole that deep. We can't explore with any kind of submersible in the oceans.

[00:06:43] What we've been looking for for years is a metallic asteroid, something that's very dense. Psyche is an asteroid 200 kilometers across, thought to be metal rich. Psyche is our way to explore our own planet. We have meteorites fall off the Earth. Some of them are little tiny pieces. Some of them are the size of cars. But compared to Psyche, they're just tiny little specks of dust.

[00:07:06] When I first started as a graduate student, we had never visited an asteroid. Not any of them. Asteroids were points of light in the sky. And now they're real geologic places. They're places we can visit. More than the awe, more than the wonder, we have this responsibility to do this right.

[00:07:30] Because that will determine whether we get the data that graduate students 10 years, 20 years, 30 years from now will learn things about this asteroid that we can't even imagine today. It's the journey of a lifetime and I didn't want to miss it.

[00:08:02] That's NASA Psyche mission co-investigator Dr. Tim McCoy, who's the curator in charge of the United States National Meteorite Collection at the Smithsonian National Museum of Natural History. This is Space Time. Still to come, the discovery of a new type of atomic nucleus. And later in the science report, the latest climate report shows unprecedented ocean warming right across the entire South Pacific. All that and more still to come on Space Time.

[00:08:36] This episode of Space Time is brought to you by NordVPN, Space Time's official VPN service. Let's face it, these days your online privacy is more important than ever. Whether you're streaming science documentaries, reading the latest research, or exploring deep space images, you don't want your data to be tracked or your location exposed. With NordVPN, one click is all it takes to secure your internet connection.

[00:09:00] It encrypts your data, hides your IP address, and keeps your activity safe from prying eyes. Whether you're at home, work, or connected to a public Wi-Fi. And here's where it gets really good. As a Space Time listener, we have an exclusive offer for you. 74% off a NordVPN plan, plus 4 extra months for free. That's right, a huge 74% discount, plus 4 bonus months, just for being a Space Time listener. All you need to do is head over to NordVPN.com slash Stuart Gary.

[00:09:29] That's NordVPN.com slash Stuart Gary. Not only does NordVPN protect your data, but it gives you access to content from right around the world. If you want to watch a science series that's only available in another country, no problem. Just switch your virtual location and unlock it instantly. And of course the whole thing is risk-free, with a 30-day money-back guarantee. So you've got nothing to lose and your online freedom to gain.

[00:09:54] So, protect your digital life, support Space Time, and grab our exclusive offer now at NordVPN.com slash Stuart Gary. That's NordVPN.com slash Stuart Gary. And now, it's back to our show. For the first time in more than 30 years, the heaviest nucleus decaying through proton emission has been measured.

[00:10:22] The last similar breakthrough was achieved way back in 1996. The radioactive decay of atomic nuclei has been one of the keystones of nuclear physics ever since the beginning of nuclear research. Now, the heaviest nucleus ever to have decayed through proton emission has been measured in the Accelerator Laboratory at the University of Javakia in Finland. One of the study's authors, Henneke Cohen, says,

[00:10:45] Proton emission is a rare form of radioactive decay in which the nucleus emits a proton rather than a neutron in order to take a step towards stability. The new nucleus is so far the lightest known isotope of astatine-188, consisting of 85 protons and 103 neutrons. Exotic nuclei of this kind are extremely challenging to study due to their short lifespans. They also have low production cross-sections, so very precise techniques are needed.

[00:11:12] The study's co-author, Kaley Oranen, says the nucleus was produced in a fusion evaporation reaction by irradiating a natural silver target with a strontium-84 ion beam. The authors were then able to study the heavy nuclei. In addition to the experimental results themselves, the study expanded on a theoretical model to interpret the measured data. The model has allowed the authors to describe the shape of the nuclei as being strongly prolate, in other words, shaped like a watermelon.

[00:11:40] Kokoen says the properties of the nucleus suggest the trend change in the binding energy of the valence proton, possibly caused by an interaction unprecedented in heavy nuclei. This is Space Time.

[00:12:08] And time now to take another brief look at some of the other stories making use in science this week with the Science Report. The latest World Meteorological Organization's Southwest Pacific State of the Climate report has found that unprecedented ocean warming engulfed the region last year, resulting in record-breaking temperatures on both land and sea. The report covers a vast area of the planet, including Australia, New Zealand, the Pacific and parts of Southeast Asia.

[00:12:34] It found that marine heat waves stretched for nearly 40 million square kilometres. That's an area five times the size of Australia and more than 10% of the global ocean surface area. Extreme rainfall and flooding caused deadly and destructive impacts across the region, with major events in Australia, New Zealand, Fiji, Malaysia, Indonesia and the Philippines, while other parts of the region remained unusually dry.

[00:13:01] A new study has shown the impact groups of people moving through Papua New Guinea communities have had on the genetic makeup of the indigenous population. The findings, reported in the journal Nature Ecology and Evolution, are based on ancient DNA of 42 people from PNG dating back some 2,500 years. The authors found that the DNA from the oldest individuals was more Papuan-related, whereas the DNA from people who lived around 2,100 years ago had elements of East Asian DNA.

[00:13:30] The authors say this suggests that there was a centuries-long delay in people in local communities reproducing with those who arrived from Southeast Asia. A new study has confirmed that having a mix of tea, berries, apples, oranges and grapes every day could lower your risk of chronic disease and early death. The findings, reported in the journal Nature Food, looked at data from over 124,000 people in the UK Biobank, finding that people who had a diet high in flavonoid-rich foods

[00:13:59] had a 6-20% lower risk of cardiovascular disease, type 2 diabetes, cancer, respiratory disease and neurodegenerative diseases. The study found that having a wide variety of flavonoid compounds was important, suggesting that including several different servings of flavonoid-rich foods in your diet might have a major impact on your overall health. Continuing with this week's theme of exploitation online,

[00:14:25] it turns out it's not just con-artists pushing pseudo-scientific cues that are a problem. There are heaps of exploitative online scammers, from psychics and practitioners of the black arts to those who prey on the broken-hearted and lonely. Tim Mendham from Australian Skeptic says those looking for love are especially vulnerable to the catfisher. Catfishing is when someone pretends to be someone else and they say, oh I'm in love with you. This is our problem with online social media.

[00:14:51] Anybody can make claims out there and reach a lot of other people on apparently an intimate level. Especially online, people trust that someone is who they say they are online and they can fall for their most amazing schemes. Now obviously it was all the email schemes about Nigerian princes and lots of money or someone I'm dying and I want to leave my money to a good Christian person, I'm sure you're that person. Just send me your bank account details and I'll put it in. Oh I need a few thousand just to get me going, etc. Actually I've never got an email from a Nigerian prince, I'm a bit disappointed.

[00:15:21] I often keep all the scam emails that I get and some of the better examples, the more inventive ones or the silly ones with really bad spelling. I receive things from Africa but not necessarily Nigeria and I get a lot from people who say, I'm the widow of someone who was a minister in a government and who collected a lot of money and I want to get it out of the country or I want to do good works and I'm spreading out a million dollars here, a million dollars there. Would you take a million dollars to do good works in your area? I know you're a good person. That's all the ones I get in the emails apart from all the very, very strange things.

[00:15:51] And I don't go onto Lonely Hearts websites or those that have apps so I'm not a victim to those sort of things. But it'd be easy to understand why some people are. Now it's become sort of online through emails, through web chat, through a whole range of different, whatever format and platform you've got. And it goes through the Lonely Hearts club, the dating apps, all these sorts of things. For people who are vulnerable about looking for them who are lonely, you know, sad condition. And there's someone who will take advantage of that, guaranteed.

[00:16:18] We had a presentation recently in Sydney all about this from someone who had been through it, pointing out that it's very prevalent amongst older women who might be lonelier, the widowed or whatever, they might be looking for a romance. And there's people who would take advantage of it. Someone who looks romantic, who looks a bit glamorous, et cetera, some exotic sort of nature. And there are serial offenders who will go and say the same sort of message to I love you, I love you. I want to get together, but I'm having a bit of trouble here. I'm in prison. I need some money, et cetera. Can you send me some money so I can come and see you? And there are people like this.

[00:16:48] And according to this presentation we had, the same person could be dealing with a hundred different people at the one time. They just sort of email them and text them or whatever, not even using their own photo, sometimes not even their own gender. They're crooks, scam artists. And there's a lot of them out there. And the trouble is because the victim is vulnerable, because of their own particular emotional needs, it makes them easy targets. And then, of course, when they're easy targets and they get scammed and sometimes scammed for tens and hundreds of thousands of dollars, they find it embarrassing to come forward and say, I was made a fool.

[00:17:17] That's Tim Mendham from Australian Skeptics. And that's the show for now. Space Time is available every Monday, Wednesday and Friday through Apple Podcasts,

[00:17:42] iTunes, Stitcher, Google Podcasts, Pocket Casts, Spotify, Acast, Amazon Music, Bytes.com, SoundCloud, YouTube, your favorite podcast download provider and from Space Time with Stuart Gary dot com. Space Time's also broadcast through the National Science Foundation on Science Zone Radio and on both iHeart Radio and TuneIn Radio. And you can help to support our show by visiting the Space Time store for a range of promotional merchandising goodies.

[00:18:11] Or by becoming a Space Time patron, which gives you access to triple episode commercial free versions of the show, as well as lots of bonus audio content which doesn't go to air, access to our exclusive Facebook group and other rewards. Just go to SpaceTimeWithStewartGary.com for full details. You've been listening to Space Time with Stuart Gary. This has been another quality podcast production from Bytes.com.