Corona Borealis
What is Corona Borealis?
Constellations· Late spring–summer (N) · a small semicircle between Arcturus and Vega. Ariadne's crown — small, but seven stars in a neat semicircle make it instantly recognisable. Alphecca is the jewel, and inside the crown sits R Coronae Borealis, a star that unpredictably fades by soot forming in its atmosphere.
📍 Visible from where you are right now — computed in your browser
bearing · altitude · rise time · best time tonight
Where Corona Borealis is in your sky right now: https://nowsky.org/solar/sky?sel=con:Corona Borealis — location and time set automatically, no login.
Stars of the figure
| Star | Magnitude |
|---|---|
| Alphecca | 2.2 |
The 1 brightest of the 6 stars used in the figure (5 lines). Lower magnitude means brighter.
Deep-sky objects near this constellation
Constellation basics
| Season | late spring to summer, May–August |
|---|---|
| Brightest star | Alphecca (2.2) |
| How to find | the small C east of Arcturus and west of the Keystone |
| Area rank | 73rd of 88 |
Figures are representative approximations. Source: compiled from NASA and IAU public data.
Frequently asked
- When can I see Corona Borealis?
- late spring to summer, May–August.
- How do I find Corona Borealis?
- the small C east of Arcturus and west of the Keystone.
- What is the brightest star in Corona Borealis?
- Alphecca, magnitude 2.2.
- Where is Corona Borealis in the sky right now?
- Open the sky view for your location and time and it shows the position in the sky right now.
A star that erupts every 80 years — the recurrent nova in the crown
Corona Borealis holds a star that normally sits at 10th magnitude, visible only in telescopes, and about every 80 years brightens to 2nd: T Coronae Borealis, the Blaze Star. Eruptions were recorded in 1866 and 1946, and both were preceded, a few years before, by a slight brightening followed by a sudden dip. The same signs reappeared in 2015 and 2023, leading to predictions that the next outburst was near.
It is a recurrent nova, in which material flowing from a red giant piles onto a white dwarf until it ignites on the surface. The predicted eruption was announced for 2024 but did not come that year, and astronomers are still watching. When it does erupt it will shine like Polaris for a few days, as if a new jewel had been set in the crown, but the timing is a forecast, not a fixed date.
The constellation in depth
Corona Borealis is the crown Ariadne, princess of Crete, received when she married Dionysus after Theseus abandoned her; the god flung the wedding crown into the sky as a constellation. The Celts knew it as Caer Arianrhod, the castle of Arianrhod, and Native American stories saw the stars as dancers in a circle. Its counterpart, Corona Australis, lies in the far southern sky below Sagittarius.
Alphecca is an eclipsing binary 75 light-years away that dims slightly every 17.4 days. Inside the crown, R Coronae Borealis normally shines at sixth magnitude in binoculars, then vanishes for months to fourteenth magnitude when carbon soot condenses in its atmosphere. T Coronae Borealis is a recurrent nova erupting roughly every 80 years, with its next outburst eagerly awaited since 2024.
On summer evenings look midway between Arcturus in the west and Vega overhead for a small C or U of stars. From a city you will see Alphecca and two or three companions; a dark sky reveals the whole semicircle. Set the Sky view to a June night and the crown sits just west of the Keystone of Hercules.
Related
Figures are representative approximations. Simulated positions use J2000 mean elements.