Places · Impact site
Vredefort Dome
The largest verified impact structure on Earth — originally perhaps 300 km across, two billion years old, and worn down to a ring of hills.
- Where
- Free State, South Africa
- Coordinates
- 27.00°S 27.50°E
- Age
- 2023 million years ago
- On the map
- Show me
- More
- whc.unesco.org
The sky from here
Measured at these coordinates the sky is zone 3: rural transition, which is Bortle 3–4 and a naked-eye limit of about magnitude 6.2–7.0. The Milky Way is clearly there but loses its detail near the horizon. Light domes are obvious in several directions.
Of the 110 Messier objects, 38 are an unaided-eye target from a sky this dark, 106 are comfortable in 10×50s and 106 in a 130mm reflector. You would have to get roughly 74 km south-east before the sky reaches Bortle 2.
Every night of the year reaches full astronomical darkness at this latitude; the Sun always gets its eighteen degrees below the horizon, which places much further from the equator cannot say.
At its highest the galactic centre stands 88° up, which is the difference between a Milky Way with depth in it and a smear along the horizon. Of the 110 Messier objects, none are circumpolar and 2 never rise.
Lagoon Nebula, Southern Pinwheel and Trifid Nebula pass close to the zenith from this latitude — an object at the zenith is being seen through the least air it will ever be seen through, and the difference against the same object low in the south is not subtle.
Against that, Bode's Galaxy and Cigar Galaxy never clear the horizon here at all. No amount of aperture or patience changes that; the only remedy is to travel.
Read at 27.00°S 27.50°E. Darkness is estimated rather than measured; everything else follows from the latitude and holds along the whole parallel. How accurate this is.
Nearby
Questions
What part of the sky never rises at Vredefort Dome?
Everything north of declination +63°. From 27.0°S that is a cap 27° in radius centred on the north celestial pole, which is 5.4% of the whole celestial sphere. It is out of reach permanently rather than seasonally: no time of year and no instrument brings it above the horizon. The matching 5.4% around the south celestial pole is the same geometry inverted, and never sets.
How many hours of true darkness does Vredefort Dome get?
10 hours 48 minutes on the best night, around 21 June, falling to 7 hours 6 minutes around 21 December. Astronomical darkness is the Sun more than eighteen degrees below the horizon, which is a stricter thing than the Sun being down. Every night of the year gets there eventually, which is the quiet advantage of not being any further from the equator than this.
When is the Milky Way best from Vredefort Dome?
Around 17 June, when the galactic centre crosses the meridian at local midnight — and because this is a southern site, that is also midwinter, with the longest and darkest nights of the year underneath it. The brightest part of the Milky Way reaches its highest point on the best nights available, rather than during a summer that will not go dark. That coincidence is most of the reason the world's large optical observatories are in the southern hemisphere.
How far is Vredefort Dome from the other sites on this map?
Its closest neighbour on this map is MeerKAT, 723 km away to the south-west. The nearest other impact site is Hoba meteorite, 1,280 km to the north-west. Measured as the great circle between coordinates, which is the shortest path across the surface and rarely the one you could travel.