Science is based on facts, but before these are contrasted and leave no room for doubt, there is always prior evidence and there are always rumors, inevitably . These rumors can be things like: the detection of a new particle, the discovery of a new planet, the discovery of a new force of nature, etc. And the LIGO experiment could not be less. Since it was put into operation, it has not disappointed, neither in the achievement of scientific milestones nor in the rumors that have accompanied them.
The current rumor is as follows. It is very likely that the two LIGO observatories (along with the brand new VIRGO, which we will also talk about) have detected the collision of two neutron stars for the first time. Let us briefly recall that LIGO had specialized in the detection of black hole collisions, and that it had come to fulfill this task flawlessly up to three times (September 2015, December 2016 and January 2017).
But let’s go by parts.
How is a neutron star different from a black hole?
In reality, the difference between the two types of stars is not as huge as it may seem at first. A neutron star is also the fruit of the collapse of a previous star when it runs out of fuel and … ‘dies’. They barely reach a few tens of kilometers in diameter and a ‘coffee spoon’ of their content would weigh 100 million tons on our planet.
They are composed of neutrons because, due to gravity, protons and electrons fuse into these particles with a neutral charge that are known to all. Despite such colossal densities, a dreaded black hole does not form, but there is no doubt that ‘little is missing’. In fact, the difference between the two destinations is very subtle. Just 0.2 solar masses (in the original star) is what separates the formation of a beautiful neutron star from its dark cousin: the black hole, the ‘monster of darkness’.
Second element to take into account.
How is the imprint left by the merger of two neutron stars?
To begin with, the gravitational waves generated have significantly less amplitude when compared to those caused by two black holes. However, we have an unexpected advantage: these waves ‘live’ for many seconds, and even hours compared to the ‘scraggly’ and rapid signals caused by the former. The best way to combine both characteristics is to be close (by chance, of course) to the fusion when it occurs. But the best thing is still being able to combine not two, if not three detectors (interferometers): the two LIGO observatories, plus the new VIRGO.
Let us also quickly remember that VIRGO is an almost exact ‘copy’ of the LIGO observatories, but located in Italy. Well, by incorporating this third detector made in Europe , it is now possible to triangulate the position of the fusion event with greater precision. But the advantages do not end there: unlike a merger of black holes, the collision of two neutron stars, in addition to producing gravitational waves, generates “light”, that is: electromagnetic waves detectable by telescopes ‘to use’.
These waves can be of many types: gamma, visible, infrared and even… the optical one! This means that the cosmic phenomenon can be studied from many points of view , and with all the astronomical artillery that humanity has to its credit. With the annexation of black holes this did not happen because, as we all know by now, such celestial bodies do not let anything escape, including the light itself.
Without a doubt it is a very important rumor, which although it has not been confirmed yet, it has not been, far from it, denied. Although the groups that are part of the LIGO-VIRGO collaboration have signed strict confidentiality agreements, the first ‘good news’ is already leaking on social media.
Alberto Corbi is a professor at the Higher School of Engineering and Technology (ESIT) of the International University of La Rioja (UNIR).
Image: NASA
