Boötes

Boötes constellation lies in the northern hemisphere. It is one of the largest constellations in the sky. The constellation’s name comes from the Greek word ‘Βοώτης,’ ‘Boōtēs,’ which means ox driver, plowman, or herdsman. Boötes is the 13th largest constellation in the night sky, occupying an area of 907 square degrees. It is located in the third quadrant of the northern hemisphere (NQ3) and can be seen at latitudes between +90° and -50°. The neighboring constellations are Canes Venatici, Coma Berenices, Corona Borealis, Draco, Hercules, Serpens Caput, Virgo, and Ursa Major.

[http://www.constellation-guide.com/constellation-list/bootes-constellation/]

Boötes on Chart VII of the Uranographia of Johann Bode (1801). He carries a club or staff in his right hand and a sickle in his left, with which he also grasps the leash of his hunting dogs, represented by neighbouring Canes Venatici. Ptolemy in the Almagest mentioned the club (shown in some representations as a spear) but said nothing about the sickle, which seems to have been a later addition. Here Boötes is standing on Mons Maenalus, an obsolete sub-constellation. Above his head is another obsolete constellation, Quadrans Muralis.

According to a story that goes back to Eratosthenes, the constellation represents Arcas, son of the god Zeus and his paramour Callisto, daughter of King Lycaon of Arcadia. One day Zeus came to dine with Callisto’s father King Lycaon, an unusual thing for a god to do. To test whether his guest really was the great Zeus, Lycaon cut up Arcas and served him as part of a mixed grill (some say that this deed was done not by Lycaon but by his sons). Zeus easily recognized the flesh of his own son. In a burning rage, he tipped over the table, scattering the feast, killed the sons of Lycaon with a thunderbolt, and turned Lycaon into a wolf. Then Zeus collected the parts of Arcas, made them whole again and gave his reconstituted son to Maia the Pleiad to bring up.

Meanwhile, Callisto had been turned into a bear, some say by Zeus’s wife Hera out of jealousy, or by Zeus himself to disguise his paramour from Hera’s revenge, or even by Artemis to punish Callisto for losing her virginity. Whatever the case, when Arcas had grown into a strapping teenager he came across this bear while hunting in the woods. Callisto recognized her son, but though she tried to greet him warmly she could only growl. Not surprisingly, Arcas failed to interpret this expression of motherly love and began to chase the bear. With Arcas in hot pursuit, Callisto fled into the temple of Zeus, a forbidden place where trespassers were punished by death. Zeus snatched up Arcas and his mother and placed them in the sky as the constellations of the bear-keeper and the bear.

[http://www.ianridpath.com/startales/bootes.htm]

Bootes may be either hunting the bear (Big Deeper) or driving it away from his flocks.

[http://www.norumbega.net/tna/getnaked/getnaked4.html]

Colloquially, the pattern of stars of Boötes has been likened to a kite or ice cream cone. However, depictions of the constellation have varied historically. Aratus described him circling the North Pole, herding the two bears. The name Boötes was first used by Homer in his Odyssey as a celestial reference point for navigation, described as ‘late-setting’ or ‘slow to set,’ translated as the ‘Plowman.’ A myth associated with Boötes tells that he invented the plow and was memorialized for his ingenuity as a constellation. Later ancient Greek depictions, described by Ptolemy, have him holding the reins of his hunting dogs (Canes Venatici) in his left hand, with a spear, club, or staff in his right hand. After Hevelius introduced Mons Maenalus in 1681, Boötes was often depicted standing on the Peloponnese mountain. By 1801, when Johann Bode published his Uranographia, Boötes had acquired a sickle, which was also held in his left hand.

In ancient Babylon the stars of Boötes were known as SHU.PA. They were apparently depicted as the god Enlil, who was the leader of the Babylonian pantheon and special patron of farmers.

The stars of Boötes were incorporated into many different Chinese constellations. Arcturus was part of the most prominent of these, variously designated as the celestial king's throne (Tian Wang) or the Blue Dragon’s horn (Daijiao); the name Daijiao, meaning ‘great horn,’ is more common. Arcturus was given such importance in Chinese celestial mythology because of its status marking the beginning of the lunar calendar, as well as its status as the brightest star in the northern night sky.

Bootes - June 1, 10:00 PM - Latitude 60° North, Longitude 95° West

[http://www.peoplesguidetothecosmos.com/constellations/bootes.htm]

Constellations of Boötes and Corona Borealis

[http://www.davidmalin.com/fujii/source/Boo.html]

[http://www.space.com/3909-spring-triangle.html]

The Spring Triangle with Arcturus, Spica, and Regulus. The line between Spica and Regulus nearly represents the ecliptic, the path of the sun and planets. Arcturus and Spica are found along an arcing path off the handle of the big dipper, while Regulus can also be found from the big dipper by pointing from down from the third and fourth dipper stars.

[https://en.wikipedia.org/wiki/Spring_Triangle]

Great Diamond

[https://en.wikipedia.org/wiki/Great_Diamond]

Optical image of Arcturus (DSS2 / MAST / STScI / NASA)

Comparison between Arcturus, red supergiant Antares, and the Sun. The black circle is the size of the orbit of Mars.

Arcturus (Alpha Boötis) is the brightest star in the northern celestial hemisphere. With a visual magnitude of −0.05, it is the fourth brightest star in the night sky, after −1.46 magnitude Sirius, −0.86 magnitude Canopus, and −0.27 magnitude Alpha Centauri. It is a relatively close star at only 36.7 light-years from Earth, and, together with Vega and Sirius, one of the most luminous stars in the Sun’s neighborhood.

Arcturus has been significant to observers since antiquity. In ancient Mesopotamia, it was linked to the god Enlil, and also known as Shudun, ‘yoke,’ or SHU-PA of unknown derivation in the Three Stars Each Babylonian star catalogues and later MUL.APIN around 1100 BC. The name of the star derives from Ancient Greek ‘Ἀρκτοῦρος’ (Arktouros) and means ‘Guardian of the Bear,’ ultimately from ‘ἄρκτος’ (arktos), ‘bear’ and ‘οὖρος’ (ouros), ‘watcher, guardian.’ It has been known by this name since at least the time of Hesiod. This is a reference to its being the brightest star in the constellation Boötes.

Arcturus is a type K0 III orange giant star, with an absolute magnitude of −0.30. It has likely exhausted its hydrogen from its core and is now in its active hydrogen shell burning phase. It will continue to expand before entering horizontal branch stage of its life cycle. Models suggest its mass is slightly larger than that of the Sun. Arcturus has been estimated to be around 6 billion to 8.5 billion years old, and is ascending the red giant branch until it accumulates a large enough degenerate helium core to ignite the helium flash.

Arcturus is visible from both Earth’s hemispheres as it is located 19° north of the celestial equator. The star culminates at midnight on 27 April, and at 9PM on June 10 being visible during the late northern spring or the southern autumn. From the northern hemisphere, an easy way to find Arcturus is to follow the arc of the handle of the Big Dipper. By continuing in this path, one can find Spica, ‘Arc to Arcturus, then spike to Spica.’ Together with Spica and Denebola (or Regulus, depending on the source), Arcturus is part of the Spring Triangle asterism, and by extension, also of the Great Diamond after factoring in Cor Caroli (Canes Venatici).

[https://en.wikipedia.org/wiki/Arcturus]

Illustration of the two components of Epsilon Boötis

Epsilon Boötis is a double star in the northern constellation of Boötes. It has the traditional name Izar and was named Pulcherrima (most beautiful) by Otto Struve. The name Izar is derived from the Arabic ‘izār,’ ‘veil,’ and Pulcherrima is Latin for ‘loveliest.’ Other historical names are Mirak, and Mizar.

The star system can be viewed with the unaided eye at night, but resolving the pair with a small telescope is challenging. The brighter component (A) has an apparent visual magnitude of 2.37, making it readily visible to the naked eye at night. The fainter component (B) is at magnitude 5.12, which by itself would also be visible to the naked eye. The system is at a distance of about 203 light-years (62 parsecs) from the Earth. This means the pair has a projected separation of 185 Astronomical Units and they orbit each other with a period of at least 1,000 years.

The brighter member has a stellar classification of K0 II-III, which means it is a fairly late-stage star well into its stellar evolution, having already exhausted its supply of hydrogen fuel at the core. With more than four times the mass of the Sun, it has expanded to about 33 times the Sun’s radius and is emitting 501 times the luminosity of the Sun. This energy is being radiated from its outer envelope at an effective temperature of 4,550 K, giving it the orange hue of a K-type star.

The companion star has a classification of A2 V, so it is a main sequence star that is generating energy through the thermonuclear fusion of hydrogen at its core. This star is rotating rapidly, with a projected rotational velocity of 123 km s−1. By the time the smaller main sequence star reaches the current point of the primary in its evolution, the larger star will have lost much of its mass in a planetary nebula and will have evolved into a white dwarf. The pair will have essentially changed roles: the brighter star becoming the dim dwarf, while the lesser companion will shine as a giant star.

[https://en.wikipedia.org/wiki/Epsilon_Bo%C3%B6tis]

Eta Boötis has the traditional names Muphrid and Saak. The name Muphrid is from the Arabic ‘mufrid ar-rāmiħ,’ ‘the (single) one of the lancer.’

This star is a subgiant that has begun the process of evolving from a main sequence star into a red giant. It has about 1.7 times the mass of the Sun and 2.7 times the Sun’s radius. The estimated age of this star is about 2.7 billion years. Based on its spectra, Eta Boötis has a significant excess of elements heavier than helium. In fact the ratio of iron to hydrogen is considered close to the upper limit for dwarf stars in the galactic disk. The star is a suspected spectroscopic binary with a reported period of 494 days, but the companion was not confirmed. This does not rule out a low mass stellar companion of spectral class M7.

Eta Boötis appears close to the prominent star Arcturus (Alpha Bootis) in Earth’s sky, and Arcturus is in fact its closest stellar neighbor, as both stars are nearly identical in distance from the Sun. The two stars are about 3.24 light years apart, and each would appear bright in the other’s sky. Arcturus would appear as roughly magnitude -5.2 (about 120 times brighter than it appears from Earth, or close to twice the brightness of Venus) in the night sky of a hypothetical planet orbiting Eta Boötis, while Eta Boötis would appear at about magnitude −2.4 (absolute magnitude −2.41 at 0.99 parsec) in the sky of a hypothetical planet orbiting Arcturus, or over twice the brightness of Sirius in our night sky.

Since 1943, the spectrum of this star has served as one of the stable anchor points by which other stars are classified.

[https://en.wikipedia.org/wiki/Eta_Bo%C3%B6tis]

Gamma Boötis has the traditional name Seginus (also Segin, Ceginus) or Haris. The name Seginus resulted from Latinization of an Arabic form of the Greek name of the constellation of Boötes (Theguius). The name Haris comes from the Arabic name of the constellation of Boötes, ‘Al Haris Al Sama,’ which means ‘the guard.’

Gamma Boötis is approximately 85 light years away from Earth. It belongs to the spectral class A7III. It is a Delta Scuti type variable star with a period of 1.13 hours. Its brightness varies from magnitude +3.02 to +3.07.

[https://en.wikipedia.org/wiki/Gamma_Bo%C3%B6tis]

Delta Boötis is a double star in the constellation Boötes, located at a distance of approximately 121.8 light-years (37.3 parsecs) from the Earth. This star is sometimes called Princeps, meaning prince or prime in Latin. The apparent visual magnitude of this star is 3.5, making it visible to the naked eye even during a Full Moon.

This system consists of a pair of stars located in physical proximity to each other and sharing a similar motion through space, suggesting that they may form a binary star system. Based upon their angular separation and their distance, they have a projected separation of 3,800 Astronomical Units (AU). However, their separation along the line of sight from the Earth remains uncertain, so all that can really be said is that they are separated by at least 3,800 AU. If they are gravitationally bound to each other, it requires a minimum of 120,000 years to complete an orbit.

The brighter member of the pair has a stellar classification of G8 III, indicating that it has exhausted the supply of hydrogen at its core and evolved into a giant star. It now has a radius more than ten times the radius of the Sun. Compared to the Sun, this star appears deficient in elements other than hydrogen and helium- the star’s metallicity. The outer envelope of this star has an effective temperature of 4,847 K, which is what gives it the characteristic yellow hue of a G-type star.

The secondary component has a stellar classification of G0 V, which suggests it is a main sequence star that may be similar in physical properties to the Sun. The apparent visual magnitude of this star is 7.81, making it much less luminous than the primary component.

[https://en.wikipedia.org/wiki/Delta_Bo%C3%B6tis]

Beta Boötis has the traditional name Nakkar or Nekkar. This is a mis-transliteration of the Arabic ‘baqqār,’ ‘cattle driver.’ It marks the head of Boötis the herdsman. It has an apparent visual magnitude of 3.5, making it one of the brighter members of the constellation. This star is approximately 225 light-years (69 parsecs) from Earth.

Nakkar has more than three times the mass of the Sun and greater than 21 times the Sun’s radius. At the estimated age of 240- 251 million years, it has evolved into a giant star with a stellar classification of G8 IIIa. The star is radiating around 170- 194 times as much luminosity as the Sun from its outer envelope at an effective temperature of 4,932 K. This heat gives it the yellow-hued glow of a G-type star. It has an estimated rotation period of about 200 days and the pole is inclined 28° ± 6° to the line of sight from the Earth.

In 1993, the ROSAT satellite was used to observe an X-ray flare on Beta Boötis. This was the first such observation for a low-activity star of this type. The flare may be explained by an as yet unobserved M-type dwarf companion star.

[https://en.wikipedia.org/wiki/Beta_Bo%C3%B6tis]

Mu Boötis, known as Alkalurops, is a triple star popular with amateur astronomers. It has an overall magnitude of 4.3 and is 121 light-years away. Its name (Greek ‘καλαύροψ’ (kalaurops) ‘shepherd’s staff’) is from the Arabic phrase for ‘club’ or ‘staff.’ The primary appears to be of magnitude 4.3 and is blue-white. The secondary appears to be of magnitude 6.5, but is actually a close double star itself with a primary of magnitude 7.0 and a secondary of magnitude 7.6. The secondary and tertiary stars have an orbital period of 260 years. The primary has an absolute magnitude of 2.6 and is of spectral class F0. The secondary and tertiary stars are separated by 2 arcseconds; the primary and secondary are separated by 109.1 arcseconds at an angle of 171 degrees.

Celestial photograph depicting many of Boötes’ double and multiple stars. Arcturus is the bright white star in the lower right. The semicircle of stars near the bottom left is the neighboring constellation Corona Borealis.

Besides Pulcherrima and Alkalurops, there are several other binary stars in Boötes. For example, Xi Boötis is a quadruple star popular with amateur astronomers. The primary is a yellow star of magnitude 4.7 and the secondary is an orange star of magnitude 6.8. The system is 22 light-years away and has an orbital period of 150 years. The primary and secondary have a separation of 6.7 arcseconds at an angle of 319 degrees. The tertiary is a magnitude 12.6 star (though it may be observed to be brighter) and the quaternary is a magnitude 13.6 star.

A digital rendering of Tau Boötis b

Extrasolar planets have been discovered encircling ten stars in Boötes as of 2012. Tau Boötis is orbited by a large planet, discovered in 1999. The host star itself is a magnitude 4.5 star, 15.6 parsecs from Earth. It has a mass of 1.3 solar masses and a radius of 1.331 solar radii; a companion, GJ527B, orbits at a distance of 240 AU. Tau Boötis b, the sole planet discovered in the system, orbits at a distance of 0.046 AU every 3.31 days. Discovered through radial velocity measurements, it has a mass of 5.95 Jupiter masses. This makes it a hot Jupiter. The host star and planet are tidally locked, meaning that the planet’s orbit and the star’s particularly high rotation are synchronized. Carbon monoxide is present in the planet’s atmosphere.

WASP-14 b is one of the most massive and dense exoplanets known, with a mass of 7.341 Jupiter masses and a radius of 1.281 Jupiter radii. Discovered via the transit method, it orbits 0.036 AU from its host star with a period of 2.24 days. WASP-14 b has a density of 4.6 grams per cubic centimeter, making it one of the densest exoplanets known. Its host star, WASP-14, is an F5V-type star of magnitude 9.75, 160 parsecs from Earth. It has a radius of 1.306 solar radii and a mass of 1.211 solar masses. It also has a very high proportion of lithium.

NGC 5466 by Hubble Space Telescope
[https://en.wikipedia.org/wiki/NGC_5466]

Boötes is in a part of the celestial sphere facing away from the plane of our home Milky Way galaxy, and so does not have open clusters or nebulae. Instead, it has one bright globular cluster and many faint galaxies. The globular cluster NGC 5466 has an overall magnitude of 9.1 and a diameter of 11 arcminutes. It is a very loose globular cluster with fairly few stars and may appear as a rich, concentrated open cluster in a telescope. Its fairly large diameter means that it has a low surface brightness, so it requires a large amateur telescope to view. Only approximately 12 stars are resolved by an amateur instrument.

The Boötes void: The stars you see in the circle are actually in front of the void!

The Boötes Void (or the Great Void) was discovered in 1981 and located in the vicinity of the constellation of the same name. At 250 to 330 million light years across, the Boötes Void is one of the largest voids out there that we’ve discovered. So far 60 galaxies have been discovered in the Boötes Void and all of those are found in a tube shape running through the void. For a fun thought experiment consider the distance between us and our closest galactic neighbor, Andromeda. At about 2.5 million light years, this would only cover about 1% of the Boötes Void. If we are to use a rough estimate of about 1 galaxy every 10 million light years (4 times farther than Andromeda) there should be approximately 2,000 galaxies in the Boötes Void. It’s thought that this void might have been created by the merging of smaller voids. Expressing the vastness that is the Boötes Void, astronomer Greg Aldering said, “If the Milky Way had been in the center of the Boötes void, we wouldn’t have known there were other galaxies until the 1960s.”

[http://asd.gsfc.nasa.gov/blueshift/index.php/2013/07/30/jasons-blog-next-stop-voids/]

The Boötes void is roughly 700 million light years from Earth. Beyond it and within the bounds of the constellation, lie two superclusters at around 830 million and 1 billion light years distant.

Also, the Hercules- Corona Borealis Great Wall, the largest known structure in the Universe, covers a significant part of Boötes.

A Quadrantid captured by an all-sky camera during a 4-second exposure

Boötes is home to the Quadrantid meteor shower, the most prolific annual meteor shower. It was discovered in January 1835 and named in 1864 by Alexander Hershell. The radiant is located in northern Boötes near Kappa Boötis, in its namesake former constellation of Quadrans Muralis. Quadrantid meteors are dim, but have a peak visible hourly rate of approximately 100 per hour on January 3- 4. The zenithal hourly rate of the Quadrantids is approximately 130 meteors per hour at their peak; it is also a very narrow shower. The Quadrantids are notoriously difficult to observe because of a low radiant and often inclement weather. The parent body of the meteor shower has been disputed for decades; however, Peter Jenniskens has proposed 2003 EH1, a minor planet, as the parent. 2003 EH1 may be linked to C/1490 Y1, a comet previously thought to be a potential parent body for the Quadrantids. 2003 EH1 is a short-period comet of the Jupiter family; 500 years ago, it experienced a catastrophic breakup event. It is now dormant. The Quadrantids had notable displays in 1982, 1985, and 2004. Meteors from this shower often appear to have a blue hue and travel at a moderate speed of 41.5- 43 kilometers per second.

[https://en.wikipedia.org/wiki/Bo%C3%B6tes]

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