Stand on a quiet residential street in Aurora on a clear winter night and look up: the sky itself is the attraction here. The name of this city is also the name of the natural light display caused by charged particles from the Sun colliding with atoms in Earth's upper atmosphere, and that coincidence is the thread running through this guide.
Aurora suits travellers who are curious about the science and folklore of the northern lights and who are content to build a visit around a handful of local churches rather than a long list of conventional sights. It is not a destination with a dense roster of attractions, and this guide does not pretend otherwise.
1. Watch for the aurora itself
The aurora is a natural light display in Earth's upper atmosphere, caused by charged particles from the Sun colliding with atoms in the atmosphere. These collisions excite oxygen and nitrogen, which then emit light of different colours such as green, red, and purple. Auroras display dynamic patterns of radiant light that appear as curtains, rays, spirals or dynamic flickers covering the entire sky.
Green is the most common colour, because a fairly high concentration of atomic oxygen and higher eye sensitivity in green make green auroras the most common. Red appears at the highest altitudes, where the low concentration of atoms and lower sensitivity of the eye at that wavelength make it visible only under more intense solar activity. The forms range from a mild glow near the horizon, through patches and arcs, to rays and coronas that cover much of the sky. Some discrete auroras are at times bright enough to read a newspaper at night. A mild glow near the horizon can be told apart from moonlit clouds because stars can be seen undiminished through the glow.
2. Colorado Christian Fellowship
One of the churches named among the places in Aurora. A visit here is a straightforward way to spend part of a morning or a Sunday in the company of local residents rather than in transit between sights.
Pair it with one of the other churches on this list if you are planning a morning of it, and check locally before you go, as this guide does not carry service times.
3. Faith Temple Church of God in Christ
A second church among the named places in the city. Its inclusion on this list is a reminder that in Aurora the built landmarks are congregations rather than monuments.
If you are working through the churches in one day, group the ones closest to each other and leave the rest for another visit rather than rushing.
4. Living Hope Baptist Church
Another of the named places in Aurora. Worth the time as part of an unhurried look at how the city's community life is organised around its churches.
Combine it with the other churches you have chosen for the same outing, and confirm details locally before travelling.
5. Peace Mennonite Community Church
A Mennonite congregation and one of the named places in Aurora. The variety of denominations represented among these churches is itself the interesting thing about a visit.
Set aside the same block of time you would give any of the others, and treat the churches as a set rather than singling one out.
6. Saint Mark's Lutheran Church
A Lutheran church among the named places in Aurora. Like the others here, it is a place to visit for its role in the community rather than for a catalogue of sights inside.
If you are visiting several churches, note that this guide does not carry opening hours or service times for any of them, so check ahead.
7. Saint Stephen's Episcopal Church
An Episcopal church and the last of the named places in Aurora. It rounds out a list that is short but genuine.
Make it the final stop of a church-focused morning and leave the evening free for the sky, which is the reason many travellers come.
8. Learn to read the aurora's forms
Before you go out to look, it helps to know what you are looking at. According to Clark (2007), there are five main forms that can be seen from the ground, from least to most visible: a mild glow near the horizon; patches or surfaces that look like clouds; arcs that curve across the sky; rays, which are light and dark stripes across arcs reaching upwards by various amounts; and coronas, which cover much of the sky and diverge from one point on it.
Brekke (1994) also described some auroras as "curtains", a similarity often enhanced by folds within the arcs. Arcs can fragment or break up into separate, at times rapidly changing, often rayed features that may fill the whole sky. Knowing the sequence gives you something to watch for as a display develops rather than a single static image.
9. Understand why the colours differ
The colours are not random. At its highest altitudes, excited atomic oxygen emits red light; the low concentration of atoms and lower sensitivity of eyes at this wavelength make this colour visible only under more intense solar activity, which is why the top parts of the "curtains" appear faint. Scarlet, crimson, and carmine are the most often seen hues of red.
At lower altitudes, the more frequent collisions suppress the red mode and the green emission dominates. Red and green can also mix together to produce pink or yellow hues.
10. Time your visit to the solar cycle
Auroras are occasionally seen in latitudes below the auroral zone when a geomagnetic storm temporarily enlarges the auroral oval. Large geomagnetic storms are most common during the peak of the 11-year sunspot cycle or during the three years after the peak.
This is the single most useful planning fact in this guide: if seeing an aurora matters to you, aim your trip at the peak of the sunspot cycle or the three years that follow it, and accept that a display is never guaranteed.
11. Know what causes a display
Auroras are the result of disturbances in the Earth's magnetosphere caused by enhanced speeds of solar wind from coronal holes and coronal mass ejections. These disturbances alter the trajectories of charged particles in the magnetospheric plasma, and these particles, mainly electrons and protons, precipitate into the upper atmosphere.
Understanding this makes a night of watching more rewarding: what you are seeing is the result of ionization and excitation of atmospheric constituents emitting light of varying colour and complexity, shaped by Earth's magnetic field.
12. Learn the names
In northern latitudes the effect is known as the aurora borealis or the northern lights; the southern counterpart is the aurora australis or the southern lights. The term aurora borealis appeared in a 1649 description by Pierre Gassendi of an auroral display visible all over France in 1621, and it entered the English language in 1828.
The word aurora is derived from the name of the Roman goddess of the dawn, Aurora, who travelled from east to west announcing the coming of the Sun. The words borealis and australis are derived from the names of the ancient gods of the north wind (Boreas) and the south wind (Auster or australis) in Greco-Roman mythology. Modern style guides recommend that the names of meteorological phenomena, such as aurora borealis, be uncapitalized.
If you only have one day
Morning. Start with the churches named in this guide, choosing two or three rather than attempting all of them: Colorado Christian Fellowship, Faith Temple Church of God in Christ, and Living Hope Baptist Church make a reasonable first group. Check locally for times before you set out, as this guide does not carry them.
Afternoon. Continue with Peace Mennonite Community Church, Saint Mark's Lutheran Church and Saint Stephen's Episcopal Church, or use the afternoon to read up on the aurora's forms and colours so that you know what you are looking for after dark.
Evening. Go out to watch for the aurora itself. Look for the mild glow near the horizon first, then arcs, rays and coronas as the display develops. Remember that green is the most common colour and that a faint red upper edge is a sign of more intense solar activity.
What actually causes an aurora?
Auroras are the result of disturbances in the Earth's magnetosphere caused by enhanced speeds of solar wind from coronal holes and coronal mass ejections. These disturbances alter the trajectories of charged particles, mainly electrons and protons, which precipitate into the upper atmosphere, where ionization and excitation of atmospheric constituents emit light of varying colour and complexity.
When is the best time in the solar cycle to plan a trip?
Large geomagnetic storms are most common during the peak of the 11-year sunspot cycle or during the three years after the peak. Those storms are what enlarge the auroral oval and bring the aurora to lower latitudes.
Which colours will I see, and why?
Green is the most common, because a fairly high concentration of atomic oxygen and higher eye sensitivity in green make green auroras the most common. Red appears at the highest altitudes and is visible only under more intense solar activity. Red and green can also mix together to produce pink or yellow hues.
How can I tell an aurora from a cloud?
A mild glow near the horizon can be close to the limit of visibility, but it can be distinguished from moonlit clouds because stars can be seen undiminished through the glow.
Decide on your season, pick your churches, and give the sky a proper evening; the planning starts with a single clear night.