Arcturus, the bright orange star of Boötes

Arcturus is the brightest star north of the celestial equator, a warm orange star in Boötes, the herdsman. It is easy to find, it is moving faster across the sky than almost any other bright star, and it once turned on the lights of a World's Fair.

Where is it from where I am?

How to spot it: Follow the curve of the Big Dipper's handle: 'arc to Arcturus'. Source (opens in a new tab)

What you are looking at

Arcturus is fourth in ESA's list (opens in a new tab) of the brightest stars, 37 light-years away. Of all the stars in the Bright Star Catalogue north of the celestial equator, none is brighter, by this site's check of the catalogue.

How to find it

NASA's version (opens in a new tab) of the old rhyme: find the Big Dipper, follow the curve of its handle away from the bowl, about the width of an outstretched hand, and you reach Arcturus. Keep going in the same direction and the next bright star is Spica.

A star in a hurry

All stars move, but most so slowly that the constellations look the same for centuries. Arcturus is an exception: by this site's calculation from its catalogued proper motion, it shifts 2.3 seconds of arc a year, enough to cross the width of the full Moon in about 800 years.

The star that opened a World's Fair

On 27 May 1933, at 9:15 p.m., the lights of Chicago's Century of Progress exposition were switched on with light from Arcturus (opens in a new tab), collected by telescopes at four observatories including Yerkes. The star was chosen because its light was believed to have set out about 40 years earlier, around the time of Chicago's 1893 fair. Today's figure, 37 light-years (opens in a new tab), puts the departure nearer 1896.

In another tradition

In Vedic astrology Arcturus is the star of Swati, the fifteenth lunar mansion.

Where on Earth, and when

It rises from anywhere north of about 71°S.

North of about 71°N, it never sets.

It climbs at least 20° high, the finder's threshold for a suggestion, from latitudes between 51°S and 89°N.

It is highest in the evening sky, at about 9 p.m. local time, in mid-June, from either hemisphere, wherever it rises. With daylight saving time, that is nearer 10 p.m. on the clock.

Worked out by this site from the Bright Star Catalogue, for a flat, clear horizon. Hills, buildings, haze and city light all cut into this; the air also lifts objects near the horizon by about half a degree. For your own place and night, use the sky finder.