The historic signals were picked up by two advanced detectors

Just 0.4 seconds after the historic gravitational wave detection, Nasa's Fermi telescope (pictured) also detected a gamma ray burst

Last week, scientists made the 'the scientific breakthrough of the century' with the detection of gravitational waves.

When the waves were detected, they knew they had been caused by two black holes 30 times the size of the sun colliding.

But a second signal, seen by a telescope in space suggests both black holes could have been formed inside a gigantic star.

The discovery was the first time anyone had detected the warping of space-time caused by a collision of two massive black holes - something first predicted in Einstein's Theory of General Relativity in 1915.

These gravitational waves, created 1.3 billion light-years from Earth, help confirm our universe was created by the Big Bang, and will give an unprecedented glimpse into its beginning.

The historic signals were picked up by two advanced Laser Interferometer Gravitational-wave Observatories (Ligo) in Louisiana and Washington.

Just 0.4 seconds later, Nasa's Fermi telescope also detected a gamma ray burst, a flash of electromagnetic rays associated with high energy collisions.

In order to produce a gamma ray burst, a black hole needs to be fed at an enormous rate of somewhere between the mass of a planet and the mass of the sun every second.

This is only possible to get near the centre of a massive star at the end of its life.

This gamma ray signal was a surprise for physicists, as they would not normally be associated with the merging of two black holes.

But Professor Avi Loeb from Harvard University has suggested a new idea could explain the gamma ray burst.

'In short, my idea is that a massive star can give birth to a pair of black holes instead of just one, like a pregnant woman that holds two babies in her belly,' author Professor Loeb told MailOnline.

Last week, scientists in the Ligo Scientific Collaboration directly observed the ripples of gravitational waves (artist's impression shown) for the first time. Using the world's most sophisticated detector, the project scientists listened for 20 thousandths of a second as the two giant black holes circled around each other

The researchers detected the gravitational waves on September 14, 2015, at 5:51 a.m. EDT, using the twin Ligo interferometers, located in Livingston, Louisiana and Hanford, Washington

'The two signals might be related if the black hole binary detected by Ligo originated from two clumps in a dumbbell configuration that formed when the core of a rapidly rotating massive star collapsed.' he explained.

'Once the black holes merge, additional infall of matter onto the remnant black hole can produce the gamma-ray burst observed by the Fermi satellite.'

HOW COULD A STAR MAKE TWO BLACK HOLES? The theory has been proposed by Professor Avi Loeb from Harvard University. He believes a massive star 'can give birth to a pair of black holes instead of just one, like a pregnant woman that holds two babies.' The star would have had to be a few times larger than our sun. As it began to run out of fuel, its core collapsed and formed a black hole. If it was rotating fast enough the core could have become shaped into a dumbbell, then snap into two, which both collapsed to create two black holes. Advertisement

Professor Loeb has now published a paper explaining how two black holes could have been created inside a star.

'My paper suggests the novel idea that when a massive star is rapidly rotating, the centrifugal force during its collapse will lead to the formation of a bar that breaks into two clumps of matter, like a dumbbell configuration,' he said.

The star would have had to be a few times larger than our sun.

As it began to run out of fuel, its core collapsed and formed a black hole.

If it was rotating fast enough the core could have become shaped into a dumbbell, then snap into two, creating two black holes.

The gamma rays were not confirmed by a second telescope, which means more research is needed.

'There is still some discussion about whether the Fermi signal is a false alarm or not,' Loeb added.

'But even if it is a false alarm, future Ligo events should be monitored for accompanying light since they may signal the birth of black hole twins.'

Despite his reservations, his discovery has piqued the interest of the research community.

Gravitational waves are invisible ripples in the fabric of space and time caused by the movement of dense objects, like black holes. These waves spread out across the universe but have never been seen by scientists before now

How our sun and Earth warp space and time, or spacetime, is represented here with a green grid. As Albert Einstein demonstrated in his theory of general relativity, the gravity of massive bodies warps the fabric of space and time, and those bodies move along paths determined by this geometry

WHAT ARE GRAVITATIONAL WAVES?

Scientists view the the universe as being made up of a 'fabric of space-time'. This corresponds to Einstein's General Theory of Relativity, published in 1916. Objects in the universe bend this fabric, and more massive objects bend it more. Gravitational waves are considered ripples in this fabric. They can be produced, for instance, when black holes orbit each other or by the merging of galaxies. Gravitational waves are also thought to have been produced during the Big Bang. If found, they would not only confirm the Big Bang theory but also offer insights into fundamental physics. For instance, they could shed light on the idea that, at one point, most or all of the forces of nature were combined into a single force. In March 2014, a team operating the Bicep2 telescope, based near the South Pole, believed they had found gravitational waves, but their results were proven to be inaccurate. Advertisement

'It's a very interesting suggestion that the paper has raised,' Professor Sheila Rowan, director of Glasgow University's Institute for Gravitational Research told MailOnline.

'We now are looking forward to taking more data later this year to get more statistics and information on what happens when black holes merge.'

Professor Stephen Hawking said the gravitational wave detection marked a moment in scientific history.

'Gravitational waves provide a completely new way at looking at the universe,' he told the BBC.

'The ability to detect them has the potential to revolutionise astronomy.

'This discovery is the first detection of a black hole binary system and the first observation of black holes merging.'

The gravitational wave found in this study is believed to be the product of a collision between two massive black holes, 1.3 billion light years away - a remarkably extreme event that has not been observed until now.

'The colliding black holes that produced these gravitational waves created a violent storm in the fabric of space and time, a storm in which time speeded up, and slowed down, and speeded up again, a storm in which the shape of space was bent in this way and that way,' Caltech physicist Kip Thorne said.

Based on the physics of this particular event, Ligo scientists estimate that the two black holes in this event were about 29 and 36 times the mass of the sun, and that the event took place 1.3 billion years ago.

The scientists said they first detected a gravitational wave on September 14. In this image, student Muzi Li at the Institute of Gravitational Research at Glasgow University holds a phone that shows a computer simulation of gravity waves

An artist's impression of gravitational waves generated by binary neutron stars released by the team. By studying gravitational waves scientists hope to gain insight into the nature of the very early universe, which has remained mysterious

About three times the mass of the sun was converted into gravitational waves in a fraction of a second - with a peak power output about 50 times that of the whole visible universe.

Ligo observed these gravitational waves.

Ligo uses twin detectors that have been carefully constructed to detect incredibly tiny vibrations from passing gravitational waves.

Once the researchers spotted a gravitational signal, they converted it into audio waves and listened to the sound of two black holes spiraling together, then merging into a larger single black hole.

The team were also able to trace the final milliseconds before the black holes collided.

Part of the experiment: This image shows gravitational waves as researchers saw them in the lab

This computer simulation shows the warping of space and time around two colliding black holes, pictured as spheres at the top of this image. The coloured surface is space represented as a two-dimensional sheet. The funnel-shaped warping is produced by black hole's mas

They determined that the black holes circled each other at close to the speed of light before fusing in a collision.

According to General Relativity, a pair of black holes orbiting around each other lose energy through the emission of gravitational waves, causing them to gradually approach each other over billions of years, and then much more quickly in the final minutes.

During the final fraction of a second, the two black holes collide into each other at nearly one-half the speed of light and form a single more massive black hole, converting a portion of the combined black holes' mass to energy according to Einstein's formula E=mc2.

This energy is emitted as a final strong burst of gravitational radiation.

'Most of that energy is released in just a few tenths of a second,' says Peter Fritschel, Ligo's chief detector scientist and a senior research scientist at MIT's Kavli Institute for Astrophysics and Space Research.

WHAT IS THE THEORY OF RELATIVITY? Gravitational waves were predicted under Albert Einstein's (pictured) General Theory of Relativity in 1916, but have since remained elusive In 1905, Albert Einstein determined that the laws of physics are the same for all non-accelerating observers, and that the speed of light in a vacuum was independent of the motion of all observers - known as the theory of special relativity. This groundbreaking work introduced a new framework for all of physics, and proposed new concepts of space and time. He then spent 10 years trying to include acceleration in the theory, finally publishing his theory of general relativity in 1915. This determined that massive objects cause a distortion in space-time, which is felt as gravity. At its simplest, it can be thought of as a giant rubber sheet with a bowling ball in the centre. As the ball warps the sheet, a planet bends the fabric of space-time, creating the force that we feel as gravity. Any object that comes near to the body falls towards it because of the effect. Einstein predicted that if two massive bodies came together it would create such a huge ripple in space time that it should be detectable on Earth. It was most recently demonstrated in the hit film film Interstellar. In a segment that saw the crew visit a planet which fell within the gravitational grasp of a huge black hole, the event caused time to slow down massively. Crew members on the planet barely aged while those on the ship were decades older on their return. Advertisement