Star Constellation Facts: Boötes

Star Constellation Facts: Boötes

Boötes, representing a “herdsman”, or “ploughman”, is a distinctly “kite” shaped constellation that can be seen in the night sky by observers located between latitudes +90 and -50 degrees. It  is the 13th biggest constellationin the night sky, taking up an area of 907 square degrees of the northern celestial hemisphere, and also contains the third most luminous star in the entire sky, the red supergiant star Arcturus. Boötes is also home to five stars with confirmed planets, but contains no Messier objects. It is visible

Ursa Major Family of Constellations

Along with the constellations Camelopardalis, Canes Venatici, Coma Berenices, Corona Borealis, Draco, Leo Minor, Lynx, Ursa Major, and Ursa Minor, Boötes belongs to the Ursa Major family of constellations.


There are several myths associated with the constellation Boötes. One story has it that Boötes represents Icarius, a grape grower who once invited the god Dionysus to inspect his vineyards. Dionysus was duly impressed by what he saw, and as a reward, taught Icarius the secret of wine-making. Icarius turned out to be a star pupil, and produced such good wines that he decided to invite all his friends to come and sample the fruits of his vines. His friends, however, had no idea what they were drinking, and the next day they ended up suffering from the world’s first hangovers. Icarius’ friends then accused him of trying to poison them, so they killed him in revenge. Dionysus was said to be saddened by the killing of his friend, and placed him in the sky as a sign of his affection- where he can be seen to this day as the constellation Boötes.

Star Constellation Facts: Boötes

Notable Stars

– Arcturus (Alpha Boötis), an orange giant (K1.5 IIIpe) located about 37 light years away, is at least 110 times more luminous than the Sun, and is the night sky’s 3rd most luminous star with an apparent magnitude of -0.04. Furthermore, the star’s location on the celestial equator makes it easy to spot from both hemispheres, and from the northern hemisphere, it is easily found by following the arc of the Big Dipper’s handle. Arcturus is believed to a member of the 52-strong Arcturus Stream, a small group of stars that is moving perpendicularly through the plane of the Milky Way. It is also a member of the Local Fluff, or more precisely, the Local Interstellar Cloud, a 30-light-year-diameter interstellar cloud through which the entire solar system is currently moving.

– Nekkar (Beta Boötis) is a yellow giant (G8 IIIa) star located about 220 light years away from Earth. What makes it remarkable is the fact that it is a variable star of the flare type, meaning it can brighten dramatically in the space of a few minutes. It is at around 250 million years old, at least 21 times bigger than the Sun, and anything between 170 and 195 times as luminous, depending on its state of variability at any given time.

– Seginus (Gamma Boötis) is located about 85 light years away, and is classified as a Delta Scuti variable star with a A7III classification. Delta Scuti variable stars show only marginal variations in brightness, and in the case of Seginus, its magnitude variations between 3.02 and 3.07 are the result of both rotational and non-rotational pulsations that occur on its surface with a period of only 6.79 hours.

Notable Deep Sky Objects

Boötes Void; This hole in the Universe has been described as the “spookiest place ever”, and with good reason. Consider this; our cosmic backyard is populated by more than 30 galaxies, collectively known as the Local Group, spanning an area of only a few million light years. The Boötes Void however, spans an area of 250 million light years – and it contains only 60 known galaxies in a volume of space that represents 0.27% of the diameter of the known Universe.

Boötes VoidThis is the largest void known, and its volume of about 230,000 cubic mega-parsecs should have contained around 10,000 galaxies. To put this volume into some kind of perspective is almost impossible, so let’s replace the average density of galaxies with a simple graph that represents galactic density as valleys and peaks. On such a graph, galaxies would show as the peaks of narrow, steeply tapering “towers”. For instance, typical galaxies such as the Milky Way would be represented as a peak with about the same footprint and height as the Empire State Building, while even a modestly-sized void would represent a three-foot-deep hole that is three times as big as Manhattan. On this scale, the Boötes Void would swallow most of the U.S. Eastern Seaboard.

Another way of describing this hole in the Universe would be to say, as American astronomer Gregory Scott Alderling once did “….if the Milky Way had been in the centre of the Boötes Void, we wouldn’t have known there were other galaxies until the 1960s.”

Scientists have no explanation for how such a hole could have formed, apart from positing that this Void is the result of several smaller voids coalescing; however, cosmological models suggest that the Universe is not old enough for natural processes to have emptied out such a large volume. Regardless of how the Void came to be, the galaxies in it are on average more luminous than galaxies outside of it, but what is really strange is that the galaxies in the hole are arranged in the shape of a tube, a phenomenon that occurs nowhere else, and which has so far resisted a rational explanation.

Boötes I (Boötes Dwarf Galaxy); a diminutive galaxy that was discovered in 2006, is only about 720 light years in diameter, and located about 197,000 light years away. With an apparent magnitude of 13.1, it is one of the faintest galaxies known, and its distorted shape is believed to be the result of the Milky Way pulling it apart.

Meteor Showers

Three meteor showers are associated with Boötes- the January Boötids, the June Boötids, and the Quadrantids.

January Boötids; this meteor shower is not known for spectacular displays, does not occur every year, and even when it does the highest hourly rate recorded was only 25 meteors per hour in 1957. The shower can peak at any time between January 9th, and January 18th.

June Boötids; another weak shower, the June Boötids peaks between June 26th, and July 2nd every year. Although most displays are weak with fewer than five meteors per hour, there have been more productive outbursts, most notably the shower of 1998, when a maximum of 100 meteors per hour was observed. The shower is associated with Comet Pons-Winnecke, a short period comet that orbits the Sun every 6.37 years.

The Quadrantids; somewhat more productive, the Quadrantids shower peaks during the first week of January, and it is associated with a suspected extinct comet, comet 2003 EH1, that is believed to have lost all of ice, hence the absence of a notable tail. The Quadrantids have been known to deliver as many as 120 meteors per hour, and it is best observed from the northern hemisphere, although it has been observed from north of latitude 51 degrees South.