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supermassive black hole

Sagittarius A* – the black hole at the centre

At the centre sits a black hole with the mass of 4 million Suns. In 2022 an image of it was published for the first time. Seen from Switzerland it lies in the constellation Sagittarius, hidden behind dense clouds of dust.

▶ View in the 3D model

Key figures

Mass

4.3 million Suns

Distance

26,000 light-years

Size (event horizon)

about 25 million km – smaller than Mercury's orbit

First image

2022, Event Horizon Telescope

Interesting facts

• Nothing can escape from a black hole, not even light. So the picture does not show the hole itself, but the glowing gas around it.
• For the picture, radio telescopes all over the world were linked together – into one telescope as big as the Earth.
• The star S2 orbits the black hole in just 16 years, racing past at 25 million km/h. This made it possible to weigh the black hole – Reinhard Genzel and Andrea Ghez received the Nobel Prize for it in 2020.

Why can't we see it?

Between us and the centre lie dense clouds of dust. In visible light there is nothing to be seen there – only infrared, X-ray and radio telescopes can look through.

How to find Towards the centre of the Milky Way in the sky

In July and August around midnight, low in the south above the constellation Sagittarius. There the band of the Milky Way is at its widest and brightest – but only far away from city lights, for example in the mountains. Seen from Switzerland, it never climbs higher than about 14 degrees.

Visible with: the naked eye. More under Watching the sky.

Where is it?

Sagittarius A* – the black hole at the centre belongs to the “The Milky Way” level of the Cosmic Zoom (field of view about 130,000 light-years). Our galaxy: a spiral of 100 to 400 billion stars. The Sun lies in the Orion Arm, 26,000 light-years from the centre. All the neighbouring stars from the previous level are inside the tiny dot at “Sun”.

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