Elusive molecule, first in the universe, detected in space

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Less than 100,000 years after the Big Bang, the very first molecule appeared, an improbable marriage of helium and hydrogen — Less than 100,000 years after the Big Bang, the very first molecule appeared, an unlikely marriage of helium and hydrogen known as helium hydride ion, or HeH +.

At first, more than 13 billion years ago, the Universe was an undifferentiated soup of three single elements to an atom.

Stars would not form until 100 million years ago.

But in the 100,000 years that followed the Big Bang, the very first molecule appeared, an unlikely marriage of helium and hydrogen known as helium hydride ion or HeH.⁺.

"It was the beginning of chemistry," said David Neufeld, a professor at Johns Hopkins University and co-author of a study published Wednesday, explaining how, after a decades-long search, scientists have finally detected the molecule elusive in space.

"The formation of HeH⁺ This is the first step on the path of increasing complexity in the Universe, "a change as important as that of single-cell life to multicellular life on Earth," he told AFP. .

Theoretical models have long convinced astrophysicists that HeH⁺ came first, followed – in a specific order – by a parade of other increasingly complex and heavy molecules.

He h⁺ had also been studied in the laboratory since 1925.

But detected HeH⁺ in its natural habitat had remained beyond their reach.

"The lack of definitive evidence of its very existence in interstellar space has long been a dilemma for astronomy," said lead author Rolf Gusten, a scientist at the Institute of Radio Astronomy Max Planck in Bonn.

The researchers knew where to look.

Already in the 1970s, models suggested that HeH⁺ should exist in significant amounts in the glowing gases ejected by the stars of the Sun dying, which created conditions similar to those of the beginning of the Universe.

HeH + spectrum observed with GREAT aboard SOFIA towards the planetary nebula NGC 7027. In the underlying image of the Hubble / NICMOS camera, the clear transition zone between the ionized HII (white-yellow) region and the the cold envelope (red color) is clearly visible. It is in this ionization front that HeH + is formed (marked by an artistic concept of the molecular structure). The sky area covered by the GREAT instrument with a size of 14.3 seconds includes most of the emission of the nebula. The spectral line width of the HeH + profile is determined by the movement of the expanding envelope. Credits: Composition: NIESYTO design; Image NGC 7027: William B. Latter (SIRTF / Caltech Science Center) and NASA / ESA; Spectrum: Rolf Güsten / MPIfR (Nature, April 18, 2019)

A fragile molecule

The problem was that the electromagnetic waves emitted by the molecule were in a range – the far infrared – canceled by the earth's atmosphere and therefore undetectable from the ground.

NASA and the German Aerospace Center have joined forces to create an airborne observatory consisting of three main components: a gigantic 2.7-meter telescope, an infrared spectrometer and a Boeing 747, whose fuselage was shaped like a helicopter. a window Door them.

From a cruising altitude of nearly 14,000 meters, the stratospheric observatory for infrared astronomy, or SOFIA, has avoided 85% of the atmospheric "noise" of ground-based telescopes.

Data from a series of three flights in May 2016 contained molecular evidence long sought by scientists, intertwined in the NGC 7027 planetary nebula about 3,000 light-years away.

"The discovery of HeH⁺ is a spectacular and beautiful demonstration of Nature's tendency to form molecules, "said Neufeld.

In this case, he did so despite unsuitable circumstances.

Even though the temperatures in the young universe fell rapidly after the Big Bang, they still stood around 4,000 degrees Celsius, a hostile environment for molecular bonds.

In addition, helium – a "noble" gas – has a very low propensity to form molecules, "explained Neufeld.

His union with ionized hydrogen was fragile and did not persist very long. It was replaced by progressively more robust and complex molecular bonds.

Heavier elements such as carbon, oxygen and nitrogen – and the many molecules they generated – were formed later still by the nuclear reactions that feed the stars.

Cosmic dust forms in supernova explosions

More information:
Rolf Güsten et al. Astrophysical detection of Helium hydride ion HeH⁺, Nature (2019). DOI: 10.1038 / s41586-019-1090-x

Quote:
Elusive molecule, first in the universe, detected in space (April 17, 2019)
recovered on April 17, 2019
from https://phys.org/news/2019-04-elusive-molecule-universe-space.html

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