Paris - Astronomers scanning the Milky Way said on Wednesday they were baffled when they failed to spot something invisible.
To explain: The team were looking for evidence of dark matter, the substance that is believed to comprise 83% of matter in the Universe.
But it cannot be detected by the naked eye or by existing astronomical techniques.
Instead it is detected indirectly, from the gravitational pull that it exerts on other phenomena.
Astronomers at the European Southern Observatory (ESO) said they had expected to spot evidence for dark matter swirling around the Sun after they mapped the motions of more than 400 stars in the Milky Way.
But they found nothing.
"The amount of mass that we derive matches very well with what we see - stars, dust and gas - in the region around the Sun," team leader Christian Moni Bidin of Chile's University of Concepcion said in a press release.
"But this leaves no room for the extra material - dark matter - that we were expecting. Our calculations show that it should have shown up very clearly in our measurements. But it was just not there!"
"Despite the new results, the Milky Way certainly rotates much faster than the visible matter alone can account for.
"So, if dark matter is not present where we expected it, a new solution for the missing mass problem must be found. Our results contradict the currently accepted models. The mystery of dark matter has just become even more mysterious," he added.
The ESO team used a 2.2m telescope at La Silla Observatory, located in the southern part Chile's bone-dry Atacama desert, to draw up the map.