Episode Highlights:
🚀 ARTEMIS 2 DELAYED - NASA's historic moon mission pushed to March after hydrogen leak during wet dress rehearsal. Four astronauts await their journey around the Moon as teams address familiar technical challenges.
🛰️ SPACEX UNVEILS STARGAZE - Revolutionary space traffic management system uses 30,000 star trackers to detect 30 million orbital transits daily. Free conjunction data offered to all satellite operators starting this spring.
⚠️ FALCON 9 GROUNDED - SpaceX temporarily halts launches after upper stage deorbit issue. Critical Crew-12 astronaut mission scheduled for February 11th hangs in the balance.
🌌 JWST'S RARE DISCOVERY - Five-way galaxy merger spotted in early universe challenges cosmic evolution models. System formed just 800 million years after Big Bang shows unexpected complexity.
🌠 LOCAL VOID MYSTERY SOLVED - 50-year puzzle resolved as scientists map flat sheet of matter beyond Local Group. Milky Way fleeing massive cosmic void at 600,000 mph.
⭐ RUNAWAY STARS MAPPED - Largest study reveals dual mechanisms ejecting massive stars from the galaxy. 214 O-type stellar speedsters analyzed, some exceeding 700 km/s.
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This episode includes AI-generated content.
00:00:00 --> 00:00:03 Anna: Welcome to Astronomy Daily, your source for
00:00:03 --> 00:00:06 the latest space and astronomy news. I'm
00:00:06 --> 00:00:06 Anna.
00:00:06 --> 00:00:08 Avery: And I'm Avery. We're here to bring you
00:00:08 --> 00:00:10 today's cosmic headlines on this Wednesday,
00:00:11 --> 00:00:13 February 4, 2026.
00:00:13 --> 00:00:15 Anna: We've got a packed show today with some
00:00:15 --> 00:00:18 significant developments. NASA's Artemis
00:00:18 --> 00:00:20 2 mission has hit another speed bump with
00:00:20 --> 00:00:23 their moon rocket, experiencing some familiar
00:00:23 --> 00:00:24 issues during testing.
00:00:25 --> 00:00:27 Avery: SpaceX is making headlines on two fronts
00:00:27 --> 00:00:29 today. Launching an innovative new space
00:00:29 --> 00:00:32 safety system while also deal with a
00:00:32 --> 00:00:34 temporary grounding of their Falcon 9 rocket.
00:00:35 --> 00:00:37 Anna: The James Webb Space Telescope has spotted
00:00:37 --> 00:00:39 something extraordinary in the early
00:00:39 --> 00:00:42 universe. A rare five way galaxy
00:00:42 --> 00:00:44 merger that's challenging our understanding
00:00:44 --> 00:00:45 of cosmic evolution.
00:00:46 --> 00:00:48 Avery: Scientists have finally cracked a 50 year
00:00:48 --> 00:00:51 mystery about why nearby galaxies seem to be
00:00:51 --> 00:00:54 fleeing from us. And it involves a massive
00:00:54 --> 00:00:55 cosmic void.
00:00:55 --> 00:00:57 Anna: And we'll wrap up with fascinating new
00:00:57 --> 00:01:00 research on runaway stars. Massive
00:01:00 --> 00:01:02 stellar objects racing through the Milky Way
00:01:02 --> 00:01:04 at incre speeds.
00:01:04 --> 00:01:05 Avery: Let's dive in.
00:01:05 --> 00:01:08 Anna: Our top story today comes from NASA's Kennedy
00:01:08 --> 00:01:11 Space center in Florida, where Artemis 2
00:01:11 --> 00:01:13 mission has been delayed by at least a month
00:01:13 --> 00:01:16 following issues during a critical wet dress
00:01:16 --> 00:01:17 rehearsal test.
00:01:17 --> 00:01:19 Avery: This is the mission that will send four
00:01:19 --> 00:01:21 astronauts on a flyby of the moon, the first
00:01:21 --> 00:01:24 crewed lunar mission in over 50 years.
00:01:24 --> 00:01:26 The crew includes NASA astronauts Reid
00:01:26 --> 00:01:29 Wiseman, Victor Glover, Christina Koch
00:01:29 --> 00:01:32 and Canadian Space Agency astronaut Jeremy
00:01:32 --> 00:01:32 Hansen.
00:01:33 --> 00:01:35 Anna: So what happened during this test? NASA
00:01:35 --> 00:01:38 concluded a 49 hour practice countdown on
00:01:38 --> 00:01:41 Tuesday after loading 700
00:01:41 --> 00:01:44 gallons of liquid hydrogen and liquid oxygen
00:01:44 --> 00:01:46 into the massive Space Launch System rocket.
00:01:47 --> 00:01:49 Avery: And early in the tanking process, as we
00:01:49 --> 00:01:52 reported yesterday, they detected a hydrogen
00:01:52 --> 00:01:54 leak from the interface that routes cryogenic
00:01:54 --> 00:01:56 propellant into the rocket's core stage.
00:01:57 --> 00:01:57 Sound familiar?
00:01:58 --> 00:02:00 Anna: Unfortunately, yes. These hydrogen leaks
00:02:00 --> 00:02:03 are reminiscent of the issues that plagued
00:02:03 --> 00:02:06 the Artemis I launch attempts back in 2022.
00:02:06 --> 00:02:08 However, there's some good news. They did
00:02:08 --> 00:02:10 resolve the issue during this test and
00:02:10 --> 00:02:13 actually achieved full tanking on the first
00:02:13 --> 00:02:15 try, which NASA considers a tremendous
00:02:15 --> 00:02:16 success.
00:02:16 --> 00:02:19 Avery: That's actually quite significant progress.
00:02:19 --> 00:02:21 The resolution involved stopping the hydrogen
00:02:21 --> 00:02:24 flow, allowing the interface to warm up so
00:02:24 --> 00:02:26 the seals could reseat and then adjusting the
00:02:26 --> 00:02:29 flow of propellant. It worked, but it raised
00:02:29 --> 00:02:31 concerns about launch day operations.
00:02:31 --> 00:02:34 Anna: NASA Administrator Jared Isaacman announced
00:02:34 --> 00:02:37 they're moving off the February launch window
00:02:37 --> 00:02:39 and targeting March for the earliest possible
00:02:39 --> 00:02:42 launch. The first opportunity next month is
00:02:42 --> 00:02:44 Friday, March 6th at
00:02:44 --> 00:02:47 8:29pm Eastern Time, with the window
00:02:47 --> 00:02:48 extending through March 11th.
00:02:49 --> 00:02:51 Avery: There were other issues too, weren't there? I
00:02:51 --> 00:02:53 read about problems with a valve and some
00:02:53 --> 00:02:55 communication dropouts.
00:02:55 --> 00:02:57 Anna: Right, a, uh, valve associated with the Orion
00:02:57 --> 00:03:00 crew Module hatch pressurization had to be re
00:03:00 --> 00:03:03 torqued and closeout operations took longer
00:03:03 --> 00:03:05 than planned. Cold weather affected several
00:03:06 --> 00:03:08 cameras and other equipment. And perhaps most
00:03:08 --> 00:03:11 concerning, there were dropouts in audio
00:03:11 --> 00:03:12 communication channels that have been
00:03:12 --> 00:03:14 recurring over the past few weeks.
00:03:15 --> 00:03:16 Avery: What's the crew saying about all this?
00:03:17 --> 00:03:20 Anna: Commander Reid Wiseman posted on social media
00:03:20 --> 00:03:23 expressing immense pride in seeing the rocket
00:03:23 --> 00:03:25 reach 100% fuel loading. Especially
00:03:25 --> 00:03:27 knowing how challenging the scenario was for
00:03:27 --> 00:03:30 the launch team. He said they're jumping back
00:03:30 --> 00:03:32 into training tomorrow to start preparations
00:03:32 --> 00:03:32 for March.
00:03:33 --> 00:03:35 Avery: And uh, NASA's planning another wet dress
00:03:35 --> 00:03:37 rehearsal before the actual launch, correct?
00:03:37 --> 00:03:39 Anna: That's right. Launch Director Charlie
00:03:39 --> 00:03:42 Blackwell Thompson confirmed they'll conduct
00:03:42 --> 00:03:44 another wet dress before proceeding with the
00:03:44 --> 00:03:47 actual launch. The team needs to fully review
00:03:47 --> 00:03:49 all the data from this test, mitigate each
00:03:49 --> 00:03:52 issue and return to testing before setting an
00:03:52 --> 00:03:53 official target launch date.
00:03:54 --> 00:03:57 Avery: It's a delay, but safety has to come first,
00:03:57 --> 00:03:59 especially with a crewed mission to the moon.
00:03:59 --> 00:04:02 Anna: From the Moon to low Earth orbit.
00:04:02 --> 00:04:04 SpaceX has just unveiled a
00:04:04 --> 00:04:07 revolutionary new space safety system called
00:04:07 --> 00:04:09 stargaze that could fundamentally change
00:04:10 --> 00:04:12 how we manage the increasingly crowded space
00:04:12 --> 00:04:13 around our planet.
00:04:14 --> 00:04:16 Avery: This is fascinating technology, Anna. Uh,
00:04:16 --> 00:04:19 stargaze is a space situational awareness
00:04:19 --> 00:04:21 system that uses data From M nearly 30
00:04:21 --> 00:04:24 star trackers across the Starlink satellite
00:04:24 --> 00:04:27 constellation to continuously monitor objects
00:04:27 --> 00:04:28 in low Earth orbit.
00:04:28 --> 00:04:31 Anna: 30 star trackers, that's an
00:04:31 --> 00:04:33 incredible network. And they're detecting
00:04:33 --> 00:04:36 approximately 30 million transits
00:04:36 --> 00:04:38 daily across the fleet. That's uh, a several
00:04:39 --> 00:04:41 order of magnitude increase in detection
00:04:41 --> 00:04:43 capability compared to conventional ground
00:04:43 --> 00:04:44 based systems.
00:04:45 --> 00:04:47 Avery: The need for this kind of system has never
00:04:47 --> 00:04:49 been more urgent. Practices like leaving
00:04:49 --> 00:04:51 rocket bodies in LEO operators,
00:04:51 --> 00:04:53 maneuvering satellites without sharing
00:04:53 --> 00:04:56 trajectory predictions and anti satellite
00:04:56 --> 00:04:58 tests have all heightened collision risks.
00:04:58 --> 00:05:00 Conventional methods typically observe
00:05:00 --> 00:05:02 objects only a limited number of times per
00:05:02 --> 00:05:04 day, causing large uncertainties in orbital
00:05:04 --> 00:05:05 predictions.
00:05:05 --> 00:05:08 Anna: What makes Stargaze particularly powerful is
00:05:08 --> 00:05:10 that it provides conjunction screening
00:05:10 --> 00:05:13 results within minutes compared to the
00:05:13 --> 00:05:15 current industry standard of several hours.
00:05:16 --> 00:05:18 That speed can be the difference between a
00:05:18 --> 00:05:21 successful collision avoidance maneuver and
00:05:21 --> 00:05:22 a catastrophic impact.
00:05:23 --> 00:05:25 Avery: Basics actually shared a real world example
00:05:25 --> 00:05:27 that demonstrates just how critical the
00:05:27 --> 00:05:30 system is. In late 2025, a
00:05:30 --> 00:05:32 Starlink satellite encountered a uh,
00:05:32 --> 00:05:34 conjunction with a third party satellite that
00:05:34 --> 00:05:37 was performing maneuvers, but whose operator
00:05:37 --> 00:05:38 wasn't sharing ephemeris data.
00:05:38 --> 00:05:41 Anna: Ephemeris data, that's the trajectory
00:05:41 --> 00:05:42 prediction information, right?
00:05:43 --> 00:05:45 Avery: Exactly. So initially the close approach was
00:05:45 --> 00:05:48 anticipated to be about 9 meters away,
00:05:48 --> 00:05:50 considered a safe missed distance with zero
00:05:50 --> 00:05:53 probability of collision. But then just five
00:05:53 --> 00:05:56 hours before the conjunction, the third party
00:05:56 --> 00:05:58 satellite performed a maneuver that Collapsed
00:05:58 --> 00:06:01 the anticipated missed distance to just 60
00:06:01 --> 00:06:02 meters.
00:06:02 --> 00:06:05 Anna: 60 meters. That's terrifyingly close
00:06:05 --> 00:06:06 in space terms.
00:06:07 --> 00:06:09 Avery: Stargaze quickly detected this maneuver and
00:06:09 --> 00:06:11 published an updated trajectory to the
00:06:11 --> 00:06:13 screening platform, generating new
00:06:13 --> 00:06:15 conjunction data messages that were
00:06:15 --> 00:06:17 immediately distributed. The Starlink
00:06:17 --> 00:06:19 satellite was able to react within an hour of
00:06:19 --> 00:06:22 detecting the maneuver, planning an avoidance
00:06:22 --> 00:06:25 maneuver to reduce coll back down to zero.
00:06:25 --> 00:06:28 Anna: And here's the really important part. SpaceX
00:06:28 --> 00:06:30 is making this data available to all
00:06:30 --> 00:06:33 satellite operators free of charge. Starting
00:06:33 --> 00:06:36 this spring, satellite operators who submit
00:06:36 --> 00:06:38 their own trajectory predictions to the
00:06:38 --> 00:06:40 platform will receive conjunction data
00:06:40 --> 00:06:42 messages against stargaze data.
00:06:42 --> 00:06:44 Avery: It's been in closed beta with over a dozen
00:06:44 --> 00:06:46 participating satellite operators, and the
00:06:46 --> 00:06:49 response has been positive. SpaceX is drawing
00:06:49 --> 00:06:52 a parallel to commercial aviation. There are
00:06:52 --> 00:06:54 hundreds of thousands of sites daily, but
00:06:54 --> 00:06:57 they avoid collision broadcaster location and
00:06:57 --> 00:06:59 flight plans to other aircraft.
00:06:59 --> 00:07:02 Anna: SpaceX is calling on all spacecraft operators
00:07:02 --> 00:07:04 to follow this same minimal standard of
00:07:04 --> 00:07:07 sharing predicted trajectories, Starlink
00:07:07 --> 00:07:09 updates and shares their ephemeris publicly
00:07:09 --> 00:07:11 every hour as an example.
00:07:11 --> 00:07:13 Avery: This is the kind of collaborative approach we
00:07:13 --> 00:07:16 need. As space becomes more congested, it's
00:07:16 --> 00:07:18 not just about protecting SpaceX's massive
00:07:18 --> 00:07:20 constellation. It's about creating a safer
00:07:20 --> 00:07:22 orbital environment for everyone.
00:07:22 --> 00:07:25 Anna: Speaking of SpaceX, the company has
00:07:25 --> 00:07:27 temporarily grounded its Falcon 9 rocket
00:07:27 --> 00:07:30 following an issue with the upper stage on a
00:07:30 --> 00:07:32 recent Starlink launch. And the timing
00:07:32 --> 00:07:33 couldn't be more critical.
00:07:33 --> 00:07:36 Avery: This happened on Monday, February 2nd. A UH
00:07:36 --> 00:07:38 Falcon 9 successfully delivered 25
00:07:38 --> 00:07:41 Starlink satellites to low Earth orbit as
00:07:41 --> 00:07:44 planned. But after deploying the payloads,
00:07:44 --> 00:07:46 the rocket's upper stage failed to perform
00:07:46 --> 00:07:47 its deorbit burn.
00:07:47 --> 00:07:50 Anna: That deorbit burn is designed to bring the
00:07:50 --> 00:07:52 spent upper stage down for controlled
00:07:52 --> 00:07:55 destruction in Earth's atmospher. Without it,
00:07:55 --> 00:07:57 we have another piece of debris in orbit,
00:07:58 --> 00:08:00 exactly the kind of problem that stargaze is
00:08:00 --> 00:08:02 designed to help monitor.
00:08:02 --> 00:08:05 Avery: The good news is the upper stage did manage
00:08:05 --> 00:08:07 to passivate itself by venting propellant,
00:08:07 --> 00:08:09 which lowered its perigee to about
00:08:09 --> 00:08:11 110km, according to
00:08:11 --> 00:08:14 satellite tracker Jonathan McDowell. It will
00:08:14 --> 00:08:16 re enter quickly, but SpaceX.
00:08:16 --> 00:08:19 Anna: Has grounded the Falcon 9 fleet while teams
00:08:19 --> 00:08:21 review data to determine root cause and
00:08:21 --> 00:08:23 corrective actions. And here's where the
00:08:23 --> 00:08:26 timing gets tricky. The Crew 12 astronaut
00:08:26 --> 00:08:28 mission to the International Space Station is
00:08:28 --> 00:08:31 currently scheduled to launch on February 11,
00:08:31 --> 00:08:32 just eight days from now.
00:08:33 --> 00:08:35 Avery: Crew 12 is particularly important because it
00:08:35 --> 00:08:38 will restore the ISS to its normal complement
00:08:38 --> 00:08:41 of seven crew members. The station has been
00:08:41 --> 00:08:43 operating with a skeleton crew of just three
00:08:43 --> 00:08:46 astronauts since January 15, when the four
00:08:46 --> 00:08:49 crew 11 astronauts departed in the first
00:08:49 --> 00:08:51 ever medical evacuation from the ISS.
00:08:52 --> 00:08:54 Anna: NASA Associate Administrator Amit uh
00:08:54 --> 00:08:56 Kshatriya confirmed that NASA teams from the
00:08:56 --> 00:08:58 commercial crew program are embedded in the
00:08:58 --> 00:09:01 investigation alongside SpaceX and the FAA.
00:09:01 --> 00:09:04 He said they're pressing towards the Crew 12
00:09:04 --> 00:09:06 window, but the launch will be contingent on
00:09:06 --> 00:09:07 the return to flight rationale.
00:09:08 --> 00:09:10 Avery: It's worth noting that the Falcon 9 has an
00:09:10 --> 00:09:13 incredible safety record. Last year alone, it
00:09:13 --> 00:09:16 launched a record breaking 165
00:09:16 --> 00:09:18 times, with all missions successful. Just
00:09:18 --> 00:09:20 a single mission experienced a significant
00:09:21 --> 00:09:24 anomaly, a Starlink launch where a booster
00:09:24 --> 00:09:25 toppled after landing at Sea.
00:09:26 --> 00:09:28 Anna: That March 3rd incident was traced to a fuel
00:09:28 --> 00:09:30 leak in one of the booster's nine Merlin
00:09:30 --> 00:09:33 engines, which led to a fire that weakened a
00:09:33 --> 00:09:36 landing leg. SpaceX halted launches for a
00:09:36 --> 00:09:37 week at that time as well.
00:09:37 --> 00:09:39 Avery: The question now is whether they can resolve
00:09:39 --> 00:09:41 this upper stage issue quickly enough to meet
00:09:41 --> 00:09:44 the February 11th crew 12 launch date.
00:09:44 --> 00:09:46 If not, those three astronauts on the ISS
00:09:46 --> 00:09:48 will have to wait a bit longer for
00:09:48 --> 00:09:51 reinforcements from orbital mechanics to.
00:09:51 --> 00:09:54 Anna: The deepest reaches of space. The James Webb
00:09:54 --> 00:09:55 Space Telescope has spotted something
00:09:55 --> 00:09:58 extraordinary. A five way galaxy merger
00:09:58 --> 00:10:00 in the early universe that's challenging our
00:10:00 --> 00:10:02 understanding of cosmic evolution.
00:10:03 --> 00:10:05 Avery: This is remarkable. Anna, uh, the system
00:10:05 --> 00:10:08 consists of five compact, actively star
00:10:08 --> 00:10:10 forming galaxies that were emerging when the
00:10:10 --> 00:10:13 universe was only about 800 million years
00:10:13 --> 00:10:16 old. That's just 6% of the universe's
00:10:16 --> 00:10:16 current age.
00:10:17 --> 00:10:19 Anna: And the level of complexity is what's really
00:10:19 --> 00:10:22 stunning astronomers. These five galaxies are
00:10:22 --> 00:10:24 packed into a remarkably small region of
00:10:24 --> 00:10:26 space. They're separated by only tens of
00:10:26 --> 00:10:28 thousands of light years. To put that in
00:10:28 --> 00:10:31 perspective, that's far closer together than
00:10:31 --> 00:10:32 most neighboring galaxies in the modern
00:10:32 --> 00:10:33 universe.
00:10:33 --> 00:10:36 Avery: Dr. Wada H. Yu from Texas A and M University,
00:10:36 --> 00:10:39 the study's lead author, explained that what
00:10:39 --> 00:10:41 makes this remarkable is that a merger
00:10:41 --> 00:10:43 involving such a large number of galaxies was
00:10:43 --> 00:10:46 not expected so early in the universe's
00:10:46 --> 00:10:48 history. At that time, galaxy mergers were
00:10:48 --> 00:10:50 thought to be simpler, usually involving only
00:10:50 --> 00:10:52 two to three galaxies.
00:10:52 --> 00:10:54 Anna: But it's not just the number of galaxies
00:10:54 --> 00:10:57 that's impressive. These five galaxies are
00:10:57 --> 00:10:59 producing stars at a combined rate of roughly
00:10:59 --> 00:11:02 250 solar masses per year.
00:11:02 --> 00:11:04 That's far exceeding typical star formation
00:11:04 --> 00:11:05 rates for that era.
00:11:05 --> 00:11:08 Avery: And this rapid stellar production has already
00:11:08 --> 00:11:10 enriched the system with heavier elements
00:11:10 --> 00:11:13 like oxygen, materials forged in stellar
00:11:13 --> 00:11:15 interiors and dispersed through galactic
00:11:15 --> 00:11:17 interactions. The presence of these elements
00:11:17 --> 00:11:20 indicates that multiple generations of stars
00:11:20 --> 00:11:21 had already lived and died.
00:11:22 --> 00:11:24 Anna: The really fascinating part is that gas
00:11:24 --> 00:11:26 containing oxygen and hydrogen extends
00:11:26 --> 00:11:29 beyond the galaxies themselves. This suggests
00:11:29 --> 00:11:31 that gravitational interactions are pushing
00:11:31 --> 00:11:34 enriched material into intergalactic space,
00:11:35 --> 00:11:37 showing how early mergers may have shaped not
00:11:37 --> 00:11:39 just galaxies, but the larger cosmic
00:11:39 --> 00:11:40 environment.
00:11:40 --> 00:11:42 Avery: This discovery really disrupts the standard
00:11:42 --> 00:11:45 model of galaxy assembly. That model proposes
00:11:45 --> 00:11:47 a, uh, gradual buildup where small galaxies
00:11:47 --> 00:11:50 merge over long periods to form larger
00:11:50 --> 00:11:52 systems. But this five way merger
00:11:52 --> 00:11:55 demonstrates that complex multi galaxy
00:11:55 --> 00:11:57 interactions were already underway less than
00:11:57 --> 00:11:59 a billion years after the Big Bang.
00:11:59 --> 00:12:02 Anna: Professor Casey Popovich, a UH co author on
00:12:02 --> 00:12:05 the study, emphasized the implications
00:12:05 --> 00:12:08 by showing that a complex merger driven
00:12:08 --> 00:12:11 system exists so early. It tells us
00:12:11 --> 00:12:14 our theories of how galaxies assemble and
00:12:14 --> 00:12:17 how quickly they do so need to be updated to
00:12:17 --> 00:12:17 match reality.
00:12:18 --> 00:12:20 Avery: This adds to the growing body of evidence
00:12:20 --> 00:12:23 from JWST that the early universe
00:12:23 --> 00:12:26 was capable of producing massive mature
00:12:26 --> 00:12:28 looking galaxies at astonishing speed.
00:12:28 --> 00:12:31 Matter in the early universe appears to have
00:12:31 --> 00:12:33 clustered more rapidly and efficiently than
00:12:33 --> 00:12:34 our simulation suggested.
00:12:35 --> 00:12:37 Anna: The study was published in Nature Astronomy,
00:12:38 --> 00:12:41 and it's another example of how JWST
00:12:41 --> 00:12:43 is fundamentally changing our understanding
00:12:43 --> 00:12:44 of the cosmos.
00:12:45 --> 00:12:47 Avery: Sticking with cosmic mysteries, Scientists
00:12:47 --> 00:12:50 have finally solved a 50 year old puzzle
00:12:50 --> 00:12:52 about why nearby galaxies appear to be
00:12:52 --> 00:12:54 fleeing from our own Milky Way. And the
00:12:54 --> 00:12:57 answer involves a massive cosmic void right
00:12:57 --> 00:12:58 in our neighborhood.
00:12:59 --> 00:13:00 Anna: This is one of those mysteries that's been
00:13:00 --> 00:13:03 nagging at astronomers for decades. Avery
00:13:04 --> 00:13:06 most large galaxies near the Milky Way, with
00:13:06 --> 00:13:09 the exception of Andromeda, appear to be
00:13:09 --> 00:13:12 moving away from us and seem largely
00:13:12 --> 00:13:15 unaffected by the gravitational pull of our
00:13:15 --> 00:13:16 Local Group of galaxies.
00:13:17 --> 00:13:19 Avery: The Local Group being the Milky Way,
00:13:19 --> 00:13:22 Andromeda and dozens of smaller galaxies.
00:13:22 --> 00:13:23 So what's the solution?
00:13:24 --> 00:13:27 Anna: Led by Ewood Wempe at the Captain Institute
00:13:27 --> 00:13:30 in Gronigan, an international research team
00:13:30 --> 00:13:32 used advanced computer simulations and
00:13:32 --> 00:13:35 discovered that matter just beyond the Local
00:13:35 --> 00:13:37 Group forms a broad flat
00:13:37 --> 00:13:40 structure stretching tens of millions of
00:13:40 --> 00:13:42 light years across. And here's the
00:13:43 --> 00:13:46 vast empty regions lie above and
00:13:46 --> 00:13:47 below this structure.
00:13:47 --> 00:13:50 Avery: So we're basically living on a cosmic pancake
00:13:50 --> 00:13:51 surrounded by voids.
00:13:52 --> 00:13:55 Anna: That's actually a pretty good analogy. This
00:13:55 --> 00:13:58 flat distribution of matter is the only way
00:13:58 --> 00:14:01 to accurately account for both the combined
00:14:01 --> 00:14:03 mass of the Milky Way and Andromeda and
00:14:04 --> 00:14:06 unexpected motions of nearby galaxies.
00:14:07 --> 00:14:10 Avery: But how does this flat structure explain why
00:14:10 --> 00:14:11 galaxies are moving away from us?
00:14:12 --> 00:14:14 Anna: It comes down to the Local Void, a
00:14:14 --> 00:14:17 vast empty region discovered back in
00:14:17 --> 00:14:20 1987 by Brent Tully and Rick
00:14:20 --> 00:14:22 Fisher. The Local void extends
00:14:22 --> 00:14:25 approximately 60 megaparsecs, or
00:14:25 --> 00:14:28 about 200 million light years. Beginning
00:14:28 --> 00:14:29 at the edge of the Local.
00:14:29 --> 00:14:32 Avery: Group, The Local Void is growing because
00:14:32 --> 00:14:34 there's very little matter inside it to exert
00:14:34 --> 00:14:37 gravitational pull. Our Milky Way sits in
00:14:37 --> 00:14:40 what's called the Local Sheet, a flat array
00:14:40 --> 00:14:42 of galaxies that, um, bounds the void. And
00:14:42 --> 00:14:44 this Local Sheet is Rushing away from the
00:14:44 --> 00:14:47 void's center at 260 kilometers
00:14:47 --> 00:14:48 per second.
00:14:48 --> 00:14:51 Anna: How fast is that affecting the Milky Way?
00:14:51 --> 00:14:54 Avery: The Milky Way's velocity away from the local
00:14:54 --> 00:14:56 void is 970
00:14:56 --> 00:14:59 kilometers per hour. That's 600
00:14:59 --> 00:15:02 miles per hour. It's astonishingly fast.
00:15:03 --> 00:15:05 Anna: So the new simulations show that this hidden
00:15:05 --> 00:15:08 geometry, the flat plane of dark matter
00:15:08 --> 00:15:11 beyond the Local Group, with voids above and
00:15:11 --> 00:15:14 below, is what's driving these galactic
00:15:14 --> 00:15:14 motions.
00:15:15 --> 00:15:17 Avery: Exactly. When researchers included this
00:15:17 --> 00:15:20 configuration in their simulations, they
00:15:20 --> 00:15:22 closely matched the observed positions and
00:15:22 --> 00:15:25 speeds of nearby galaxies. It provides a
00:15:25 --> 00:15:27 coherent explanation for motions that have
00:15:27 --> 00:15:29 puzzled astronomers for half a century.
00:15:30 --> 00:15:32 Anna: This is connected to research about the
00:15:32 --> 00:15:34 Hubble tension, too, isn't it? The
00:15:34 --> 00:15:36 discrepancy in measurements of the universe's
00:15:36 --> 00:15:37 expansion rate?
00:15:38 --> 00:15:40 Avery: That's right. Some researchers have proposed
00:15:40 --> 00:15:43 that if we're inside a large local void, it
00:15:43 --> 00:15:45 could affect how we measure cosmic expansion,
00:15:45 --> 00:15:47 making the local universe appear to be
00:15:47 --> 00:15:50 expanding faster than it actually is. Though
00:15:50 --> 00:15:53 that particular idea remains controversial
00:15:53 --> 00:15:54 and needs more evidence.
00:15:54 --> 00:15:57 Anna: What's remarkable is that we're learning Our
00:15:57 --> 00:15:59 immediate cosmic neighborhood is far more
00:15:59 --> 00:16:02 structured and dynamic than we previously
00:16:02 --> 00:16:04 understood. We're not just floating in a
00:16:04 --> 00:16:07 uniform sea of galaxies. We're on a sheet
00:16:07 --> 00:16:10 of matter bordering a massive void.
00:16:10 --> 00:16:13 Avery: And that void is shaping our galaxy's journey
00:16:13 --> 00:16:15 through space in fundamental ways.
00:16:15 --> 00:16:18 Anna: For our final story today, we're turning to
00:16:18 --> 00:16:20 some of the fastest objects in our galaxy,
00:16:21 --> 00:16:23 Runaway stars that are racing through the
00:16:23 --> 00:16:25 Milky Way at incredible speeds.
00:16:25 --> 00:16:28 Avery: Researchers from institutes across Spain have
00:16:28 --> 00:16:30 just completed the most extensive
00:16:30 --> 00:16:32 observational study to date of these stellar
00:16:32 --> 00:16:35 speedsters, analyzing 214 O
00:16:35 --> 00:16:38 type stars, the brightest and most massive
00:16:38 --> 00:16:39 class of stars in our galaxy.
00:16:40 --> 00:16:42 Anna: These aren't just fast moving stars, Avery.
00:16:42 --> 00:16:45 We're talking about stars with velocities
00:16:45 --> 00:16:48 that often exceed 700 kilometers per
00:16:48 --> 00:16:51 second. That's fast enough to escape the
00:16:51 --> 00:16:52 Milky Way's gravity entirely.
00:16:53 --> 00:16:56 Avery: The term runaway stars was first used back
00:16:56 --> 00:16:59 in the early 1960s by Dutch astronomer
00:16:59 --> 00:17:01 Adrian Blau. He observed stars moving at
00:17:01 --> 00:17:04 unusually high speeds and proposed they
00:17:04 --> 00:17:06 originated in binary systems and were
00:17:06 --> 00:17:09 ejected when the companion star collapsed and
00:17:09 --> 00:17:10 exploded in a supernova.
00:17:11 --> 00:17:14 Anna: By 2005, astronomers discovered even
00:17:14 --> 00:17:16 faster runaway stars, Leading to the
00:17:16 --> 00:17:19 designation hypervelocity stars. These
00:17:19 --> 00:17:21 objects are fascinating because of the
00:17:21 --> 00:17:23 influence they have on galactic evolution.
00:17:24 --> 00:17:26 Avery: By escaping their systems of origin, these
00:17:26 --> 00:17:28 stars irradiate gas and dust in the
00:17:28 --> 00:17:31 interstellar medium, eventually seeding it
00:17:31 --> 00:17:33 with heavy elements after they go supernova.
00:17:34 --> 00:17:36 This affects how future stars and planets
00:17:36 --> 00:17:36 will form.
00:17:37 --> 00:17:40 Anna: So what did this new study reveal? The team
00:17:40 --> 00:17:42 used data from ESA's Gaia
00:17:42 --> 00:17:45 observatory and the IACOB
00:17:45 --> 00:17:47 Spectroscopic Database to analyze these
00:17:47 --> 00:17:49 214o type stars.
00:17:50 --> 00:17:52 Avery: They found that most runaway stars rotate
00:17:52 --> 00:17:55 slowly, while those that rotate faster are
00:17:55 --> 00:17:57 more likely to be linked to supernova
00:17:57 --> 00:17:59 explosions in binary systems. And here's an
00:17:59 --> 00:18:02 interesting finding. The highest velocity
00:18:02 --> 00:18:04 stars tend to be single, suggesting they were
00:18:04 --> 00:18:06 ejected from young clusters through
00:18:06 --> 00:18:07 gravitational interactions.
00:18:08 --> 00:18:10 Anna: So there are actually two different
00:18:10 --> 00:18:12 mechanisms creating runaway stars.
00:18:12 --> 00:18:15 Avery: Exactly. Some are explosively ejected by
00:18:15 --> 00:18:18 supernovae in binary systems, while others
00:18:18 --> 00:18:20 are gravitationally ejected from close
00:18:20 --> 00:18:23 encounters with star clusters. The study
00:18:23 --> 00:18:25 helps clarify the relative contributions of
00:18:25 --> 00:18:27 these two mechanisms. Lead author
00:18:27 --> 00:18:30 Marcro Castrillo, now at the European
00:18:30 --> 00:18:33 Southern Observatory, called this the most
00:18:33 --> 00:18:35 comprehensive observational study of its kind
00:18:35 --> 00:18:38 in the Milky Way. By combining information on
00:18:38 --> 00:18:40 rotation and binarity, they're providing
00:18:40 --> 00:18:42 unprecedented constraints on how these
00:18:42 --> 00:18:43 runaway stars are formed.
00:18:44 --> 00:18:46 Anna: The team also identified 12 runaway
00:18:46 --> 00:18:49 binary systems, including three X ray
00:18:49 --> 00:18:52 binary sources that contain neutron stars or
00:18:52 --> 00:18:54 black holes, and three additional systems
00:18:54 --> 00:18:56 that are likely candidates for hosting black
00:18:56 --> 00:18:57 holes.
00:18:57 --> 00:18:59 Avery: Perhaps the strongest evidence for multiple
00:18:59 --> 00:19:02 ejection mechanisms was Virtually
00:19:02 --> 00:19:05 no stars in the study exhibited both high
00:19:05 --> 00:19:08 velocities and rapid rotation. If all
00:19:08 --> 00:19:10 runaway stars came from the same process,
00:19:10 --> 00:19:12 you'd expect to see some with both
00:19:12 --> 00:19:13 characteristics.
00:19:13 --> 00:19:16 Anna: Future Gaia data releases and ongoing
00:19:16 --> 00:19:18 spectroscopic studies will help astronomers
00:19:18 --> 00:19:20 trace these stars back to their birthplaces
00:19:20 --> 00:19:23 within the Milky Way, which will confirm
00:19:23 --> 00:19:25 which mechanism was responsible in each case.
00:19:26 --> 00:19:28 Avery: And there might be another fascinating angle
00:19:28 --> 00:19:30 to this research. Understanding these systems
00:19:30 --> 00:19:32 could shed light on another role they may
00:19:32 --> 00:19:35 play in galactic evolution, potentially
00:19:35 --> 00:19:37 distributing the basic ingredients of life
00:19:37 --> 00:19:38 throughout the Milky Way as they.
00:19:38 --> 00:19:41 Anna: Travel cosmic messengers carrying the seeds
00:19:41 --> 00:19:44 of life across the galaxy. That's a beautiful
00:19:44 --> 00:19:45 thought to end on.
00:19:45 --> 00:19:47 Avery: And that wraps up today's episode of
00:19:47 --> 00:19:48 astronomy daily.
00:19:48 --> 00:19:51 Anna: From NASA's moon mission delays to SpaceX's
00:19:51 --> 00:19:54 new safety innovations, from ancient galaxy
00:19:54 --> 00:19:56 mergers to mysteries in our cosmic
00:19:56 --> 00:19:58 neighborhood, it's been quite a journey
00:19:58 --> 00:19:59 through the cosmos today.
00:19:59 --> 00:20:02 Avery: Thanks for joining us. For more space news,
00:20:02 --> 00:20:05 visit our website at astronomydaily IO
00:20:05 --> 00:20:07 where you can explore our full archive and
00:20:07 --> 00:20:08 stay updated on the latest cosmic
00:20:08 --> 00:20:09 discoveries.
00:20:09 --> 00:20:11 Anna: You can also find us on social media
00:20:11 --> 00:20:14 astrodaily POD across all major
00:20:14 --> 00:20:16 platforms. Until next time, keep looking up.