Nasa spots mysterious ‘green blob’ which may have formed when a black hole swallowed a star
Astronomers spot a very unusual event which took place a long time ago in a galaxy far, far away.
Nasa has glimpsed a ‘green blob’ in the middle of a strange part of space called the Fireworks Galaxy.
The ‘pops of blue and green’ in the image above are actually bright bursts of invisible X-ray light captured by the NuSTAR space observatory.
They are coming from the centre of the galaxy, which has the scientific name NGC 6946, and came into being and then disappeared over 10 days.
The primary objective of NuSTAR is to study supernova, the name for explosions which take place at the end of stars’ lives.
These ‘violent events’ can shine brighter than entire galaxies made up of billions of stars and produce many of the chemical elements found in our universe.
‘Ten days is a really short amount of time for such a bright object to appear,’ said Hannah Earnshaw, a postdoctoral researcher at Caltech.
‘Usually, with NuSTAR, we observe more gradual changes over time, and we don’t often observe a source multiple times in quick succession.
‘In this instance, we were fortunate to catch a source changing extremely quickly, which is very exciting.’
The blob is strange because it didn’t produce the sort of visible light you’d expect from a supernova.
Instead, it’s called a ultraluminous X-ray source and has been named ULX-4 because its the fourth such outburst detected in the Firework Galaxy.
Earnshaw has just published a study which suggests the green glow came from a black hole ‘consuming another object, such as a star’.
When these monsters swallow objects, they often tear them apart and suck the resulting debris into a close orbit around the maw.
This formed a swirling disc that moves so quickly it heats up to millions of degrees celsius – which is way hotter than the 5,500 C surface of the sun – and then radiates X-rays.
Nasa wrote: ‘If an object gets too close to a black hole, gravity can pull that object apart, bringing the debris into a close orbit around the black hole.
‘Material at the inner edge of this newly formed disk starts moving so fast that it heats up to millions of degrees and radiates X-rays. (The surface of the Sun, by comparison, is about 10,000 degrees Fahrenheit, or 5,500 degrees Celsius.)
However, ULX-4 may also be caused by another phenomenon, such as a neutron star – which form after a supernova when a star does not turn into a black hole.
Neutron stars also draw in material and create a similar speeding vortex of material.