Space · Friday, 25 September 2026
An observatory counted cosmic rays far across the galaxy by the gamma-ray glow of five gas clouds
The LHAASO team caught gamma rays from five nearby giant gas clouds and showed the glow matches cosmic rays striking the gas, turning each cloud into a measuring station. SpaceX finished Starship's fuelling rehearsal before Monday's first orbit try, and a Russian cargo ship reached the space station a week late.
5
giant gas clouds near us whose gamma-ray glow was added together
the signal came from 4.5 years of the observatory's records
1 to 100 TeV
the energies where the clouds' glow matched cosmic rays hitting gas
the match is what lets a cloud stand in for a detector
0.9 PeV
or higher: where the data put the knee in the cosmic-ray count
that is 900 TeV, and a lower knee is not ruled out yet
The lead story — what happened
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Scientists working with LHAASO, an observatory that catches the showers of particles set off when something from space hits the air, published a result on 24 September.
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It appeared in the journal Nature Astronomy, about a year after the team first sent it in.
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They picked up very high-energy gamma rays, the most energetic kind of light, coming from five giant clouds of gas close to us in the Milky Way.
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The team combined the signal from all five clouds, using 4.5 years of the observatory's records.
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Cosmic rays are fast particles flying through the galaxy. When they crash into the gas in a cloud, the crash gives off gamma rays.
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The amount of gamma light matched what cosmic rays hitting the gas should make, across energies from 1 to 100 TeV, a unit for the energy of one particle.
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That makes each cloud a measuring station. Its glow shows how many cosmic rays are passing through that part of the galaxy, and how their energies are spread.
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The team also looked for the knee, a bend in the count of cosmic rays where the most energetic ones start to get rarer faster.
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They found no clear knee. Their data fit a knee at about 0.9 PeV or higher, which is 900 TeV, but a lower one cannot be ruled out yet.
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The result agrees with recent measurements of cosmic rays made by instruments on the ground.
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The authors say the clouds can now be used to map where cosmic rays are across the Milky Way, and so help work out where the particles come from.
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Who is involved
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The LHAASO Collaboration
the scientists behind the Large High Altitude Air Shower Observatory; they wrote the paper and built its software
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Nature Astronomy
a science journal; it accepted the paper on 13 August and published it on 24 September
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How it unfolded
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26 Aug 2025 The team sends the paper to Nature Astronomy
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13 Aug 2026 The journal accepts it
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24 Sep 2026 The paper is published
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Where this points
The next step the authors name is using more clouds to map cosmic rays across the Milky Way, and the open test is whether more data pin the knee at 0.9 PeV or show it lower.
What is pushing on the whole day
The bar and the word are our reading of how hard each one is pushing today. The arrow is where it is heading. The evidence is in the stories below.
SpaceX filled Starship with fuel and ran through launch day without lighting the engines on 24 September.
The rest of the day
3 more stories on this beat.
Each with its own sources. None of these is a link to the story above.
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02
Starship passes its fuelling rehearsal
SpaceX said on 24 September that it had finished a wet dress rehearsal for Flight 14 of Starship, its giant reusable rocket.
[2] In that test the team fills the rocket with fuel and goes through launch day without lighting the engines.[2] The booster and ship were stacked on the pad at Starbase in Texas overnight on 23 September.[3] The launch window opens at 8:15 a.m. US Eastern time on 28 September, pending approval from the US Federal Aviation Administration.[3] Earlier flights lasted about an hour, and this one is planned to last about ten.[3] Earlier Starship flightsabout 1 hourFlight 14, going to orbitabout 10 hoursHow long the ship is meant to stay up this time, against the flights before it. Why it matters — All 13 earlier Starship flights stopped short of orbit on purpose, and this is the first try to reach it.
[3] If it works, the ship will release 26 of SpaceX's new, larger Starlink internet satellites and circle Earth six times before splashing down in the Pacific off Chile.[2] [4] -
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Starlink passes 11,100 satellites
A Falcon 9 rocket launched 27 more Starlink internet satellites from Vandenberg in California on the evening of 19 September.
[5] Its first stage landed on a ship in the Pacific about eight and a half minutes later, on that booster's 17th flight.[5] Starlink now has more than 11,100 working satellites, according to the satellite tracker Jonathan McDowell.[5] At this year's rate, SpaceX would fly Falcon 9 149 times in 2026, down from 165 in 2025.[5] Why it matters — The bigger V3 satellites that Starship is carrying are meant to replace this whole network in time.
[3] None of them can be put into service until Starship reaches orbit.[3] -
04
A Russian cargo ship docks a week late
Russia's Progress M-25 cargo ship, which NASA calls Progress 96, docked with the International Space Station at 9:44 a.m. US Eastern time on 19 September.
[6] It flew in on its own automatic system, while two cosmonauts stood by with remote controls they did not need.[6] Its launch from Baikonur in Kazakhstan was held back a week by a problem in the third stage of its Soyuz-2-1b rocket.[6] It was the first time that version of the rocket carried a Progress.[6] Why it matters — It brought 2.8 tons of food, fuel and supplies for the seven people on the station and will stay about five months.
[6] [7] Then it will be filled with rubbish and burned up in the air, like every station freighter except SpaceX's Dragon.[7]
How a far-off cloud of gas can measure cosmic rays for us
Nobody can put a detector inside a distant cloud, but the cloud glows when cosmic rays hit it, and that light reaches Earth.
The twist
Nobody can send a detector to a cloud of gas far across the galaxy. The cloud already does the catching when cosmic rays hit it, and a telescope on Earth only has to read its light.
The picture
How it works
- Cosmic rays fly through the whole galaxy
- A detector on Earth only catches the ones passing here
- Far away, they crash into the gas of giant clouds
- Each crash gives off gamma rays that do reach Earth
- How brightly a cloud glows shows how many cosmic rays are there
- Clouds in different places, read together, make a map
Where you've seen this
Tree rings
a tree grows a wider or narrower ring each year, so scientists read past weather in places nobody was measuring it
Ice cores
bubbles trapped in old ice hold samples of the air from when the snow fell
Testing a town's waste water
one sample from the drains shows how much of a virus is spreading, without testing each person
The catch
A cloud's glow depends on how much gas it holds as well as on how many cosmic rays hit it. A wrong guess about the gas gives a wrong count of the rays.
And the whole of it
Cosmic rays reach Earth's air every day, and a detector here only ever counts the ones that arrive here. The five clouds let us look at parts of the galaxy no instrument from Earth will ever visit.
What is really going on
The LHAASO team showed that five nearby gas clouds glow in gamma rays about as much as cosmic rays hitting them should, so the clouds can be used to count cosmic rays far from Earth.
Who gains
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Scientists who study cosmic rays
— Gas clouds become measuring stations in places no detector can reach, once their glow is shown to match the rays hitting them.
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SpaceX
— A working orbital flight would start putting up the V3 satellites meant to replace its Starlink network of more than 11,100 craft.
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The seven people on the space station
— The Progress ship brought 2.8 tons of food, fuel and supplies after its week's delay.
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Who pays
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Roscosmos
— Each Progress is filled with rubbish and burned up after one trip, so a new ship has to be built for every delivery.
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SpaceX
— None of its V3 Starlink satellites can go into service until Starship reaches orbit, which no Starship has done, so the replacement network waits on one rocket.
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What nobody knows yet
Open questions from across today’s stories — ours included.
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Where the knee in the cosmic-ray count really sits.
The clouds' data fit a knee at about 0.9 PeV or higher, but the team says a lower one cannot be ruled out yet.
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02
What the full LHAASO paper shows beyond its summary.
The article is behind a paywall. We read only its published summary, so every claim here comes from that summary.
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03
Whether five clouds are enough to speak for the whole galaxy.
The team added the five together to get one signal, and says mapping the Milky Way is the next use, not something done yet.
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04
Whether Starship reaches orbit on 28 September.
No Starship has tried it before, and the flight still needed approval from the US Federal Aviation Administration when the rocket was stacked.
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05
When SpaceX will try to catch the ship itself with the launch tower.
It has caught the booster on three flights but has not yet tried with the ship, which will splash down in the sea on this flight.
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06
What went wrong with the Soyuz rocket's third stage.
Roscosmos, Russia's space agency, rolled the rocket back to its hangar and did not say what the problem was.
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Scientists using the LHAASO observatory picked up gamma rays from five giant gas clouds in the Milky Way, and the light matched what cosmic rays striking the gas should make.
Also true today
- A Russian cargo ship docked with the space station on its own after a week's delay, bringing 2.8 tons of food, fuel and supplies to the seven people aboard.
- SpaceX finished the full fuelling rehearsal for Starship's first try at orbit, which is set for 28 September.
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