Faint in X-rays, bright near ultraviolet: mysterious objects appear in space
Chandra X-ray Observatory
NASA’s space telescope for studying X-rays.
hypersoft X-ray sources
Sources that emit unusually low-energy X-rays.
Type Ia supernovae
A kind of stellar explosion used to measure cosmic expansion.
What happened
NASA’s Chandra X-ray Observatory, a space telescope, has revealed a possible new class of cosmic objects. Researchers searched public Chandra observations of six nearby galaxies. They found 84 sources with the same unusual pattern. The galaxies included Andromeda and M101, along with four elliptical galaxies.
The sources appear in images showing the lowest-energy X-rays. They almost disappear in images showing higher-energy X-rays. Scientists call them hypersoft X-ray sources. The name describes their unusually soft, or low-energy, X-rays.
Because low-energy X-rays sit next to extreme ultraviolet light, the pattern suggests strong extreme ultraviolet emission. The ultraviolet light is not easy to observe directly. Instead, researchers infer it from the X-ray behavior.
Why they were difficult to find
Extreme ultraviolet light is easily absorbed by hydrogen and helium between the stars. Low-energy X-rays are also difficult for X-ray telescopes to detect. These effects created a hidden gap in earlier searches. The sources may have been present in old data, but their unusual signature was easy to miss.
The team found these sources in both star-forming regions and areas filled with older stars. That distribution suggests the objects may not belong to only one kind of young stellar environment.
What might be producing them
The leading ideas involve binary systems. A black hole, neutron star, or white dwarf may be pulling material from a companion star. The captured material heats up and produces X-rays. Known binary systems can do this, but scientists have not seen this exact combination of very soft X-rays and strong ultraviolet radiation.
Some of the less luminous sources in Andromeda are linked with novae. A nova happens when a white dwarf collects material from a companion and undergoes a powerful surface explosion. More luminous sources might involve white dwarfs that keep burning material for longer periods.
Why the discovery matters
One long-standing question concerns Type Ia supernovae. These explosions help astronomers measure the expansion of the universe. Scientists still do not fully understand which white dwarf systems become Type Ia supernovae. Hypersoft sources might reveal a previously overlooked stage before some of those explosions.
The objects may also help explain how gas between stars becomes ionized. Ionization means that energetic light removes electrons from atoms. Massive, hot stars provide some of this energy, but they do not explain every galaxy. Extreme ultraviolet light from hypersoft sources could supply part of the missing energy. That could affect how gas heats, cools, and forms new stars.
What is known and what is not
The survey found 84 sources across six galaxies. Their unusual X-ray pattern is clear enough to define a possible new population. The study was published in Nature Astronomy.
However, the objects have not received a final physical identity. They may include several kinds of binary systems. Scientists still need to determine how many are white dwarfs, neutron stars, or black holes. They also need to learn whether the sources are common across the universe.
What comes next
Researchers will compare these objects with optical, infrared, and other observations. They can also monitor changes in brightness. Those changes may show how material moves inside each system. Searches through more galaxy archives could reveal many more examples.
This discovery does not solve the mystery yet. It shows that an overlooked group of energetic objects may connect two major questions about stars and galaxies.
Source: NASA Science
A strange space object is weak in X-rays but bright near ultraviolet light
📰 Full story: Faint in X-rays, bright near ultraviolet: mysterious objects appear in space
Scientists found 84 unusual sources in six galaxies. Their light may help explain two space mysteries.
hypersoft X-ray sources
Space sources with unusually low-energy X-rays.
extreme ultraviolet
Very energetic light near ultraviolet and X-rays.
Type Ia supernovae
Explosions that help scientists measure the universe’s expansion.
💡 The gist
- Chandra found 84 strange sources in six galaxies.
- They are weak in X-rays but strong near ultraviolet light.
- They may explain exploding stars and gas between stars.
NASA’s Chandra X-ray Observatory is a space telescope that studies X-rays. Researchers searched public images from six nearby galaxies. They found 84 unusual sources.
The sources appeared in low-energy X-ray pictures. They nearly vanished in higher-energy pictures. Scientists call them hypersoft X-ray sources. This name describes their unusually low-energy X-rays.
The pattern also suggests strong extreme ultraviolet light. Extreme ultraviolet is energetic light near ultraviolet and X-rays. Space gas can absorb this light before it reaches Earth. That helped hide the sources from earlier searches.
What could make them? One possibility is a pair of stars. One object may be a black hole, neutron star, or white dwarf. It may pull matter from its companion. The falling matter becomes hot and gives off X-rays.
Some sources in Andromeda are linked with novae. A nova is a powerful explosion on a white dwarf’s surface. More powerful sources may involve white dwarfs that keep burning matter.
This could connect the sources with Type Ia supernovae. These explosions help scientists measure the universe’s expansion. Scientists still do not know which systems create them. Hypersoft sources might show an earlier stage.
The sources may explain another puzzle. Gas between stars needs energetic light to lose electrons. Hot stars provide some light, but not always enough. Extreme ultraviolet light may fill part of that gap. It could affect how gas cools and makes new stars.
The discovery does not prove one final explanation. Scientists need more observations. They will study other kinds of light and watch brightness changes. They will also search more galaxies.
Source: NASA Science
Strange little lights appeared in space
📰 Full story: Faint in X-rays, bright near ultraviolet: mysterious objects appear in space
They look weak in X-rays, but bright in another invisible light.
Chandra
NASA’s space telescope for seeing X-rays.
ultraviolet light
Light that human eyes cannot see.
black hole
A space object that pulls things very strongly.
NASA’s Chandra is a space telescope. It looks for X-rays from space.
It found strange glowing spots. The spots look faint in X-rays. They seem bright in nearby ultraviolet light.
Ultraviolet light is invisible to our eyes. Space gas can hide some of that light. That made the spots hard to find.
Scientists do not know what the spots are. Maybe a heavy star takes matter from its partner. Maybe a black hole pulls the matter very strongly.
The spots may help explain star explosions. They may also explain light between stars.
Scientists need more telescope pictures. The mystery is still open.
Source: NASA Science