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Chelyabinsk airburst
A 20 m rock exploded at 30 km altitude with the energy of 500 kilotons. The shockwave broke windows across six cities and injured 1,500 people, almost all by flying glass.
The sky from here
Measured at these coordinates the sky is zone 8: inner city, which is Bortle 8–9 and a naked-eye limit of about magnitude 4.0–4.5. A few dozen stars, the Moon and the planets. The sky has a colour, and it is not black.
Of the 110 Messier objects, 5 are an unaided-eye target from a sky this dark, 27 are comfortable in 10×50s and 30 in a 130mm reflector. You would have to get roughly 52 km north-east before the sky reaches Bortle 2.
For 89 nights of the year — 8 May to 4 August — the sky here never reaches astronomical darkness, because the Sun stays within eighteen degrees of the horizon all night. Distance from the nearest town makes no difference to that.
The galactic centre tops out at 6° from this latitude — low enough that the busiest part of the Milky Way is always behind the most atmosphere, which is what separates this sky from a southern one. Of the 110 Messier objects, 24 never set from here and every one of them rises at some point in the year.
Little Dumbbell, Whirlpool Galaxy and Sunflower Galaxy 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.
Owl Nebula, Spindle Galaxy and Pinwheel Galaxy never set from this latitude, so they are available on any clear night of the year rather than for one season of it.
Read at 55.15°N 61.41°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 Chelyabinsk airburst?
Everything south of declination −35°. From 55.1°N that is a cap 55° in radius centred on the south celestial pole, which is 21% of the whole celestial sphere. Nothing about the calendar or the aperture changes that — the cap is below the horizon at every hour of every night. Its mirror image, the same 21% around the north celestial pole, is circumpolar here and never goes down.
How many hours of true darkness does Chelyabinsk airburst get?
Between nothing at all and 12 hours 15 minutes, depending entirely on the date. The longest night falls around 21 December; around 8 May there is no astronomical darkness at any hour, however far you get from the nearest town. Astronomical darkness is the Sun more than eighteen degrees below the horizon, which is a stricter thing than the Sun being down.
When is the Milky Way best from Chelyabinsk airburst?
Late August, as a practical matter — not June, when it is highest. The galactic centre crosses the meridian at local midnight around 17 June everywhere on Earth, and from 55.1°N that date falls inside the stretch of summer when the sky never finishes getting dark. The core is therefore at its best in precisely the weeks it cannot be seen. By late August it is still up in the evening and the nights have come back, and that overlap is the whole northern season for it.
How far is Chelyabinsk airburst from the other sites on this map?
Its closest neighbour on this map is Soyuz recovery area, 926 km away to the south-east. The nearest other impact site is Tunguska event, 2,430 km to the north-east. Distances are great-circle, so they are what a signal covers rather than what a road does.