The first ever molecule formed in the universe — helium hydride, or HeH+ — has been detected in space for the first time, a new study reports.
The elusive molecule was found in the young planetary nebula NGC 7027, where HeH+ is being formed by a white dwarf star.
Around 13 billion years ago this molecular bond would have formed as positively charged particles combined with hydrogen atoms in the early cooling universe.
The discovery was made using a telescope which is carried up into the Earth’s atmosphere, and above its signal-damping effects, by a special aeroplane.
The finding, led by researchers from the Max Planck Institute for Radio Astronomy, brings to the end a search for the molecule which began back in the late 1970s.
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The first ever molecule formed in the universe — helium hydride, or HeH+ — has been detected out in space for the first time, a new study reports
As the early universe cooled below 4,000°K (6740°F/3,727°C) some 13 billion years ago, the light elements produced from the Big Bang began to combine.
It is believed that neutral helium atoms and ionised hydrogen – or protons – reacted to form ions of HeH+.
This would have been the first type of molecular bond to ever form in the universe.
HeH+ would have ultimately gone on to react with neutral hydrogen, paving the way to the formation of molecular hydrogen — and the beginning of the universe as we know it today.
Despite both its significance in the history of the universe, and having been first successfully synthesised in the laboratory in 1925, attempts to detect the molecule out in the universe itself had previously been to no avail.
The hunt began in the late seventies, when chemical models suggested that HeH+ might exist in detectable amounts in nearby interstellar nebulae.
‘The chemistry of the Universe began with HeH+,’ said lead author and astrophysicist Rolf Güsten, of the Max Planck Institute for Radio Astronomy (MPIfR), in Germany.
‘The lack of definitive evidence of its very existence in interstellar space has been a dilemma for astronomy for a long time.’
Around 13 billion years ago, however, helium hydride would have formed as protons first combined with hydrogen atoms in an early, cooling universe (pictured in artist’s impression)
The failure to spot naturally-formed HeH+ out in space had been casting doubt on the understanding that had been developed of the chemical processes that were thought to have formed it in the early individual.
However, past hunts were only unsuccessful because the available spectrometer technology used all had too limited resolving power at the relevant wavelengths in which the molecule would be found.
With new technology, however, the search has finally come to an end.
The discovery was made using a telescope which is carried up into the Earth’s atmosphere — and its signal-damping effects — by a special aeroplane (pictured, with the telescope visible through the open door in the plane’s rear fuselage)
SOFIA (pictured in an artist’s impression showing the interior of the craft) is capable of flying above the majority of the water vapour in the atmosphere, the presence of which blocks some infrared signals from reaching the ground
Dr Güsten and colleagues from the MPIfR joined forces with researchers from Johns Hopkins University in Baltimore, both the Universities of Cologne and Applied Sciences Bonn-Rhein-Sieg in Germany, as well as the Institute of Millimetre Radioastronomy in France.
The international team made use of the high-resolution German Receiver for Astronomy at Terahertz Frequencies (GREAT) spectrometer to detect the infrared signals emitted by helium hydride ions.
The GREAT device is located on-board the Stratospheric Observatory for Infrared Astronomy (SOFIA), a modified Boeing 747 aircraft that carries a reflecting telescope.
The scientific research craft is operated by NASA and the German Aerospace Centre.
SOFIA is capable of flying above the majority of the water vapour in the atmosphere, the presence of which blocks some infrared signals from reaching the ground.
‘With recent advancements in terahertz technologies is has now become possible to perform high-resolution spectroscopy at the required far-infrared wavelength’, Dr Güsten added.
The GREAT device is located on-board the Stratospheric Observatory for Infrared Astronomy (SOFIA), a modified Boeing 747 aircraft that carries a reflecting telescope
Analysing data from three of SOFIA’s flights, the researchers found unequivocal evidence of HeH+ atoms in the direction of the planetary nebula NGC 7027.
Located around 3,000 light years from the Earth, NGC 7027 is a young, dense and small nebula located in the constellation of Cygnus.
NGC 7027’s young age made it a likely candidate in which HeH+ might be found, as it harbours conditions similar to those found in the early universe.
‘The discovery of HeH+ is a dramatic and beautiful demonstration of Nature’s tendency to form molecules’, said paper author and molecular astrophysicist David Neufeld from Johns Hopkins University.
‘Despite the unpromising ingredients that are available, a mixture of hydrogen with the unreactive noble gas helium, and a harsh environment at thousands of degrees Celsius — a fragile molecule forms.’
Located around 3,000 light years from the Earth, NGC 7027 is a young, dense and small nebula located in the constellation of Cygnus. NGC 7027’s young age made it a likely candidate in which HeH+ might be found, as it harbours conditions similar to those in the early universe
Planetary nebulae like NGC 7027 are produced by sun-like stars in the final stage of their lifetimes, where they expel large amounts of material to leave behind a dense hot core — a so-called ‘white dwarf’.
The radiation emitted by such stars — which have temperatures of around 180,000°F (100,000°C) — causes the star’s ejected envelope to ionise.
It is here that HeH+ can form.
The molecule can be detected by suitable telescopes thanks to its characteristic light emissions, which are strongest at a wavelength of 0.149 millimetres.
This wavelength is one that cannot penetrate far enough into the absorbing layers of Earth’s lower atmosphere as to reach ground-based observatories.
This explains in part why HeH+ has so far only been detected using the airborne SOFIA telescope.
The full findings of the study were published in Nature.
WHAT IS THE BIG BANG THEORY?
The Big Bang Theory is a cosmological model, a theory used to describe the beginning and the evolution of our universe.
It says that the universe was in a very hot and dense state before it started to expand 13,7 billion years ago.
This theory is based on fundamental observations.
In 1920, Hubble observed that the distance between galaxies was increasing everywhere in the universe.
The Big Bang Theory is a cosmological model, a theory used to describe the beginning and the evolution of our universe, based on observations – including the cosmic background radiation (pictured), which is a like a fossil of radiation emitted during the beginning of the universe, when it was hot and dense
This means that galaxies had to be closer to each other in the past.
In 1964, Wilson and Penzias discovered the cosmic background radiation, which is a like a fossil of radiation emitted during the beginning of the universe, when it was hot and dense.
The cosmic background radiation is observable everywhere in the universe.
The composition of the universe – that is, the the number of atoms of different elements – is consistent with the Big Bang Theory.
So far, this theory is the only one that can explain why we observe an abundance of primordial elements in the universe.