Astronomers found 84 objects of a new kind in old Chandra pictures. They were hiding in the light X-ray telescopes see worst.

The stories

3 stories on this beat today.

Every story told the same way: what happened, who is involved, why it matters, how it works, the truth and the good news.

1. 01

   Astronomers found 84 objects of a new kind in old Chandra pictures. They were hiding in the light X-ray telescopes see worst.

   84

   objects of a new kind, found in six galaxies

   all of them in pictures Chandra had already taken and made public [1]

   1999

   the year Chandra was launched; it is still working

   Ars Technica reports that old operating missions are the main target for NASA's science cuts [5]

   1.44

   times the Sun's mass, the point at which a white dwarf explodes as a Type Ia supernova

   nobody has yet caught one of these stars before it explodes [2]

   What happened

   • Astronomers found 84 objects of a kind never catalogued, in six galaxies, using pictures already sitting in the public archive of Chandra, NASA's X-ray telescope. [1]
   • Chandra was launched in 1999 and is still working. [5]
   • The objects give off very weak X-rays and a great deal of ultraviolet light, so the team calls them hypersoft X-ray sources. [1]
   • They were found by keeping the dots that appear in Chandra's lowest-energy pictures and vanish in its higher-energy ones. [1]
   • The team thinks each one is a dead star, a black hole, neutron star or white dwarf, pulling gas off a companion star. [1]
   • Pairs like that usually glow in high-energy X-rays because the stolen gas gets very hot. [2]
   • These do not, and the team does not yet know what kind of pair they are. [1]
   • Nobody saw them before because low-energy X-rays are hard for telescopes to catch, and the hydrogen and helium gas between stars soaks up ultraviolet light. [1]
   • None has been found in the Milky Way yet.
   • The team's explanation is that from Earth we look through our own galaxy's gas. [2]
   • Two of the six galaxies are spirals, Andromeda and the Pinwheel; four are ellipticals.
   • The objects sit both where stars are forming and among old stars. [1]
   • They may explain what strips electrons from the gas between stars, a job hot massive stars are not numerous enough to do on their own. [2]
   • They may also be the long-sought stars that go on to explode as Type Ia supernovae, the explosions astronomers use to measure how fast the universe is expanding. [1][2]
   • The paper was published in Nature Astronomy on Wednesday, 9 September. [1][2]

   Who is involved

   • Mustafa Muhibullah an astronomer at the University of Alabama; he led the study that found the 84 objects
   • Chandra NASA's X-ray telescope, in orbit since 1999; its archive of old pictures held the objects
   • Jimmy Irwin an astronomer at the University of Alabama and co-author; he wants to catch a Type Ia supernova before it explodes
   • Rosanne Di Stefano an astronomer at the Center for Astrophysics, Harvard & Smithsonian, and co-author; she says the search removed a blind spot

   How it unfolded

   1. 1999 Chandra, NASA's X-ray telescope, is launched [5]
   2. Since then Chandra photographs Andromeda, the Pinwheel and four elliptical galaxies; the pictures go into a public archive [1]
   3. Wed 9 Sep the team publishes 84 hypersoft X-ray sources in Nature Astronomy [2]
   4. Next find one nearby, or catch one before it explodes [2]

   Why it matters

   Watch whether anyone finds one of these objects inside the Milky Way, where our galaxy's own gas has hidden them so far.

   A nearby one could be studied in detail, not as a dot in another galaxy.

   The truth

   • What is really going on Chandra's public archive held these 84 objects for years.X-ray telescopes are built to catch high-energy light, and these objects give off almost none of it, so they sat in the pictures as faint dots nobody had sorted out.Mustafa Muhibullah's team at the University of Alabama found them by keeping only the dots that show up in Chandra's lowest-energy pictures and vanish in the higher-energy ones. [1]
   • Why it works on people The words 'mysterious' and 'unlike any they have seen before' make a signal nobody has explained feel like something that has just arrived in the sky, when the objects were in the pictures all along and what is new is the sorting. [1][2]
   • Who gains Mustafa Muhibullah's team at the University of Alabama — A new class of object, named by them, out of pictures already in a public archive; no new telescope time was needed. [1]
   • Who gains Chandra, NASA's X-ray telescope, launched in 1999 — A 27-year-old telescope has just produced a new class of object from its archive. Ars Technica reports that operating missions well past their design lives are the main target for NASA's science cuts. [5][2]
   • Who pays Astronomers who measure the universe's expansion with Type Ia supernovae — They still do not know which stars produce their measuring stick. Jimmy Irwin said they study the explosions only after they have happened. [2]
   • Nobody knows yet

     What the 84 objects actually are.

     The team says they most likely involve a black hole, neutron star or white dwarf pulling gas off a companion star, but has not identified a single one. [1]

   • Nobody knows yet

     Whether any exist in the Milky Way.

     None has been found in our own galaxy. The team's explanation is that we look through the Milky Way's own gas, which soaks up ultraviolet light, so a nearby one would be hidden by the same effect that hid all 84. [2]

   • Nobody knows yet

     Whether these objects are what strips electrons from the gas between stars.

     Hot massive stars are not numerous enough to explain all of it, and the team offers the new objects as a possible answer, not a measured one. [2]

   • Nobody knows yet

     Whether any of them will explode as a Type Ia supernova.

     Astronomers have searched for the stars that become these explosions for years without finding one. The team says these objects could be candidates and no more. [1][2]

   Good news

   • Eighty-four objects of a kind nobody had catalogued were found this week in pictures that had been sitting in Chandra's public archive, open to anyone.

1. 02

   Webb sees an asteroid's rings change

   What happened

   • Chariklo is a body 250 km across, orbiting between Uranus and Neptune. [3]
   • In 2013 it became the first small body found to have rings. [3]
   • A team led by Pablo Santos-Sanz of Spain's Institute of Astrophysics of Andalucia used the James Webb Space Telescope to watch a star pass behind the rings, and published the result in Science Advances. [3]
   • It was the first such occultation ever predicted and observed from Webb. [3]
   • Compared with earlier ground-based records, the inner ring now blocks far more starlight and the outer ring has thinned until it is hard to detect. [3]

   Why it matters

   Rings were thought to belong to giant planets, and nobody expected a 250 km body's rings to change in a decade.

   The team says the next step is another occultation, and amateur astronomers along its ground track may be part of it. [3]

   How it works

   What a telescope cannot see looks like empty sky

   An instrument catches only some kinds of light. Anything that shines mostly in the other kinds shows up as nothing, until someone looks in a new band.

   The twist

   Nothing was hiding these 84 objects except the choice of which light to look in. They appeared the moment the team compared Chandra's low-energy pictures with its high-energy ones.

   Step by step

   1. 1 A telescope is built to catch one range of light
   2. 2 Whatever shines mostly outside that range leaves a faint mark, or none
   3. 3 The catalogue fills up with what the telescope sees well
   4. 4 In that catalogue, empty sky and an unseen object look the same
   5. 5 A new band, or a comparison between bands, turns the blanks into objects

   The same force, elsewhere today

   Where this chain is also running, in today's other stories.

   • Webb sees an asteroid's rings change

     The earlier readings were made from the ground in visible light and the new one from Webb in infrared. The first thing the team must rule out is that the band changed, not the rings.

   • NASA's Moon Base chief sets out three phases

     Apollo never landed at the south pole, so its shadows, dust and micrometeorites are blanks in the record. Phase one exists to fill them in before anyone builds there.

   Where you've seen this

   Medical scans

   an X-ray shows bone and misses a soft-tissue tumour, so the tumour is absent from the picture until an MRI is done

   Fishing surveys

   a net with a set mesh counts only fish bigger than the mesh, so the small ones are missing from the count, not from the sea

   Crime maps

   a police map shows what was reported, so a crime nobody reports is missing from the map, not from the town

   The catch

   A new band shows what the old one missed and leaves out other things in turn. Webb's infrared cannot see what Chandra's X-rays can, so no single instrument ever gives the full list.

   And the whole of it

   Everyone reads the world through some instrument: a telescope, a survey, a news feed, their own two eyes. Each one leaves blanks that look like empty space. The people in these stories know where a few of their blanks are. Most of us, the reader included, never find out what ours have left out.

   The truth

   • Who gains Amateur astronomers who record occultations — Santos-Sanz said the decade of ground-based records, some from back gardens, is what let the team recognise that Webb's reading was unusual. [3]
   • Who gains Webb's schedulers — The first predicted occultation observed from Webb worked despite a last-minute course correction, and the method was reused on Quaoar. [3]
   • Who pays Scientists waiting on Chariklo's rings — The next reading needs another star to pass behind the rings as seen from Webb, and the team cannot schedule that. [3]
   • Nobody knows yet

     Whether Chariklo's rings really changed.

     The Webb team measured a clear difference from earlier ground-based records. But the rings could be lumpy, so a different slice was measured, or they could look different in infrared than in visible light. Pablo Santos-Sanz says going from the measurement to a cause is much harder. [3]

   • Nobody knows yet

     What is moving material between Chariklo's two rings.

     Mass passing from the outer ring to the inner one, or an unseen moon shepherding the inner ring, are the two ideas. Only a future occultation can test either, and those happen when the geometry allows, not when astronomers choose. [3]

   Good news

   • Webb's first predicted stellar occultation worked, and the same set-up has since been used to study the rings of Quaoar, a dwarf planet in the Kuiper belt.
   • The change in Chariklo's rings could only be recognised because amateur astronomers had been recording occultations of it for the past decade.

1. 03

   NASA's Moon Base chief sets out three phases

   What happened

   • NASA published an interview with Carlos Garcia-Galan, who runs its Moon Base programme, recorded on 14 August. [4]
   • NASA announced the plan for an outpost near the Moon's south pole in March 2026. [7]
   • Phase one is for learning: several companies landing reliably, and measuring the pole's shadows, dust, radiation and micrometeorites, before permanent hardware starts in 2028 or 2029. [4]
   • He hopes for one robotic landing this year and several next year. [4]
   • The Artemis IV crew in 2028 would be the first to meet Moon Base hardware, driving vehicles sent ahead of them. [4]

   Why it matters

   Habitats must sit at least a mile from where a lander touches down, because its engines blast the ground, so every crew's stay begins with a drive.

   Humans have spent about 80 hours in total working on the Moon's surface, and this plan would multiply that. [4]

   How it works

   Apollo never landed at the south pole, so its shadows, dust and micrometeorites are blanks in the record. Phase one exists to fill them in before anyone builds there.

   The idea, in story 02: What a telescope cannot see looks like empty sky →

   The truth

   • Who gains Astrobotic, Intuitive Machines, Firefly and Blue Origin — Phase one of the Moon Base is described as more than twenty landings bought from several vendors, and NASA's events list names their landers under the Moon Base and CLPS labels. [4][6]
   • Who pays The first Moon Base crews — Garcia-Galan says habitats must sit at least a mile from the landing site because landing engines blast the ground, so every crew begins with a drive across the pole in a vehicle sent ahead. [4]
   • Who pays Anyone hoping for a Moon Base on a fixed date — NASA's programme manager puts the start of permanent hardware in 2028 or 2029, after a learning phase whose landings have not begun. [4]
   • Nobody knows yet

     When the Moon Base's first robotic landing flies.

     Carlos Garcia-Galan said in August that he hoped for one landing this year and several next year. NASA's own events list names the landers under Moon Base and CLPS labels. [4][6]

   • Nobody knows yet

     How long the shadows at the lunar south pole actually last.

     Garcia-Galan said it may be several days but not fourteen. Phase one is meant to measure it, because Apollo landed elsewhere. [4]