Ancient Star Burst Found in the Centre of our Galaxy

Robert Lea
Dec 16, 2019 · 4 min read

A violent burst of star formation led to hundreds of thousands of supernova explosions at the centre of the Milky Way new observations reveal.

Researchers have used the HAWK-1 instrument, part of the ESO’s Very Large Telescope (VLT) array, based in the Atacama Desert, Chile, to study the Milky Way’s central region in unprecedented detail. The study has resulted in the discovery of the remnants of an ancient burst of intense star formation. This period represented by this ‘cosmic fossil’ led to another dramatic event in our galaxy’s history — a burst of supernova explosions. Hundreds of thousands of them.

Taken with the HAWK-I instrument on ESO’s Very Large Telescope in the Chilean Atacama Desert, the image combines observations in three different wavelength bands. By observing in this range of wavelengths, HAWK-I can peer through the dust, allowing it to see certain stars in the central region of our galaxy that would otherwise be hidden. (ESO/Nogueras-Lara et al)

“Our unprecedented survey of a large part of the Galactic centre has given us detailed insights into the formation process of stars in this region of the Milky Way,” says Rainer Schödel from the Institute of Astrophysics of Andalusia in Granada, Spain, who led the observations.

Clarifying what this means for our understanding of the history of our home galaxy, Schödel’s colleague Francisco Nogueras-Lara, who led two new studies of the Milky Way central region while at the same institute in Granada, adds: “Contrary to what had been accepted up to now, we found that the formation of stars has not been continuous.”

The team’s findings are due to be published in the journal Nature.

Video credit: ESO

From their observations, the team was able to conclude that around 80% of the stars found in the Milky Way’s central bulge formed in its very early history — between 8–13.5 billion years ago. This initial period of rapid star formation was followed by 6 billion years in which few stars were born.

This period of inactivity was brought to an end by another era of intense star formation around a billion years ago. In this later period of star birth, lasting less than 100 million years, the mass of the stars formed in the central region equals about that of around ten million Suns.

This beautiful image of the Milky Way’s central region, taken with the HAWK-I instrument on ESO’s Very Large Telescope, shows interesting features of this part of our galaxy. This image highlights the Nuclear Star Cluster (NSC) right in the centre and the Arches Cluster, the densest cluster of stars in the Milky Way. Other features include the Quintuplet cluster, which contains five prominent stars, and a region of ionised hydrogen gas (HII).(ESO/Nogueras-Lara et al)

“The conditions in the studied region during this burst of activity must have resembled those in ‘starburst’ galaxies, which form stars at rates of more than 100 solar masses per year,” says Nogueras-Lara, now based at the Max Planck Institute for Astronomy in Heidelberg, Germany. “This burst of activity, which must have resulted in the explosion of more than a hundred thousand supernovae, was probably one of the most energetic events in the whole history of the Milky Way.”


Live Fast, Die Young

The stars created in starbursts of the type likely seen during the periods described above are short-lived. This means that such stars have short life-spans — quickly dying in violent supernova explosions. Hence how a period of intense creation can give rise of an era of cataclysmic destruction.

Currently, the Milky Way is fairly inactive, forming stars at a much more sedate rate of around 1- 2 solar masses per year.

This chart shows the location of the Milky Way central region in the night sky. It lies in the direction of the constellation of Sagittarius (The Archer), and is marked with a red circle in the image. This map shows most of the stars visible to the unaided eye under good conditions.

The research above was only possible as a result of observations of the Galactic central region performed by ESO’s HAWK-I instrument on the VLT. This infrared-sensitive camera is able to see through the dust that usually obscures our view of the Milky Way’s central region.

The image, published in the journal Astronomy & Astrophysics by Nogueras-Lara and a team of astronomers from Spain, the US, Japan and Germany, shows the galaxy’s densest region of stars, gas and dust, which also hosts a supermassive black hole. The angular resolution of 0.2 arcseconds means the level of detail picked up by HAWK-I is roughly equivalent to seeing a football in Zurich from Munich, where ESO’s headquarters are located.

This image is just the first release from the GALACTICNUCLEUS survey, a programme that uses the large field of view and high angular resolution of HAWK-I on ESO’s VLT to create highly detailed images of the central region of our galaxy. The survey has studied over three million stars, covering an area corresponding to more than 60 000 square light-years at the distance of the Galactic centre.


Original research:

https://www.eso.org/public/archives/releases/sciencepapers/eso1920/eso1920a.pdf
https://www.eso.org/public/archives/releases/sciencepapers/eso1920/eso1920b.pdf

Rob is freelance science journalist from the UK, specialising in physics, astronomy, cosmology, quantum mechanics and obscure comic books.

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The Cosmic Companion

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Robert Lea

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Freelance science journalist. BSc Physics. Space. Astronomy. Astrophysics. Quantum Physics. SciComm. ABSW member. WCSJ Fellow 2019. IOP Fellow.

The Cosmic Companion

Exploring the wonders of the Cosmos, one mystery at a time

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