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Sagitta and Vulpecula

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Michael L Allen [email protected]

Palouse Divide Lodge Party 2019

Michael L Allen Sagitta and Vulpecula PDLSP ’19 1 / 29 Outline

1 Sagitta and Vulpecula in the sky 2 Mythology 3 4 Star clusters 5 Planetary nebulae

Michael L Allen Sagitta and Vulpecula PDLSP ’19 2 / 29 Sagitta (the Arrow)

Michael L Allen Sagitta and Vulpecula PDLSP ’19 3 / 29 Sagitta: mythology

Sagitta is an ancient , appearing in the Phenomena of (4th century BCE), and in the foundational works of Eratosthenes (3rd century BCE) and Hipparchos (2nd century BCE). Sagitta is one of the 48 of Claudius (2nd century CE) from which the modern western constellations are derived. Sagitta has no named stars. Its brightest star, gamma, shines with 3rd .

Michael L Allen Sagitta and Vulpecula PDLSP ’19 4 / 29 Sagitta: mythology

The most common story deals with Prometheus and the theme of punishment. Prometheus, a Titan in , stole fire and gave it to humans, thus empowering them technologically. punished this theft by chain- ing Prometheus to a cliff, where (the Eagle) would eat away his liver. When dis- covered Prometheus in chains, he killed Aquila with an arrow.

https://commons.wikimedia.org/wiki/File:Herakles Prometheus Louvre MNE1309.jpg

Michael L Allen Sagitta and Vulpecula PDLSP ’19 5 / 29 Sagitta: mythology

Eratosthenes ascribed Sagitta to the arrows of . The cy- clopes were a race of giants who helped Zeus overthrow the Ti- tans. Zeus slew Asclepius (Ophi- uchus) as punishment for resur- recting the dead. In retaliation, Apollo slew the . Apollo was sentenced to a of servi- tude, which he chose to serve with King Admetus. Admetus greatly benefitted from this. The story was dramatized by Euripides (5th century BCE). https://upload.wikimedia.org/wikipedia/commons/4/47/Polyphemus.png

Michael L Allen Sagitta and Vulpecula PDLSP ’19 6 / 29 Sagitta: mythology

Another story has Sagitta as the arrows used by Hercules to slay the Stymphalian birds. The birds were a destructive flock inhabiting Lake Stymphalia, near Corinth. In Hercules’ 6th labor, he used a rat- tle to scare the birds into the air, where he slew them one by one. The birds found a new nesting ground on an island in the Black Sea, where they were found by the Argonauts.

https://en.wikipedia.org/wiki/Stymphalian birds

Michael L Allen Sagitta and Vulpecula PDLSP ’19 7 / 29 Sagitta: mythology

Throughout later Arabic and Latin times, the constellation was known variously as the canna (the reed from which arrows were made), the weapon, the javelin, the dart, the pole, the five stars, the spear, and the nail of the cru- cifixion of Christ.

https://en.wikipedia.org/wiki/Arundo donax

Michael L Allen Sagitta and Vulpecula PDLSP ’19 8 / 29 Vulpecula (the Fox)

Michael L Allen Sagitta and Vulpecula PDLSP ’19 9 / 29 Flamsteed Atlas (1690)

Michael L Allen Sagitta and Vulpecula PDLSP ’19 10 / 29 Vulpecula: mythology

Vulpecula has no origin in mythology. It first appeared in the star atlas of (1687). He called it Vulpecula & Anser, the Fox and Goose. On some star atlases the Fox and Goose were separated into two, but eventually the Goose was dropped entirely from the sky. Vulpecula’s brightest star, alpha, shines with 4th magnitude. Its proper name is Anser. Note in Flamsteed’s atlas the defunct constellation , the multi-headed hound of Hades, who prevents the dead from leaving. Hercules captures Cerberus in one of his labors.

Michael L Allen Sagitta and Vulpecula PDLSP ’19 11 / 29 Double stars

Name Mag Separation Anser (alpha Vul) 4.4 and 5.8 428 arcsec Albireo (beta Cyg) 3.1 and 5.1 35 arcsec zeta Sge 5.6 (AB) and 9.0 (C) 8 arcsec 13 Sge 4.5 and 7.3 1 arcsec

Interestingly, zeta Sge components A and B were first split by Alvan Clark in 1891; the pair are 0.1 arcsec apart; both are 6th magnitude; they are described as greenish, white, and blue (A, B, and C).

Anser is a high velocity star, v of about 200 km/sec.

Michael L Allen Sagitta and Vulpecula PDLSP ’19 12 / 29 The Coathanger

First described by Al Sufi in Isfahan (964) Also called Brocchi’s Cluster, after Dalmero Brocchi (1920s) who proposed it as a photometric standard for the AAVSO Also called Collinder 399 after Per Collinder (1931) The Hipparchos satellite determined it was not a real cluster Brightest member is 4 Vul at 5th magnitude Use the stars in the straight line to find the NGC 6802

Michael L Allen Sagitta and Vulpecula PDLSP ’19 13 / 29 NGC 6802

Open cluster, apparent diameter 5 arcmin, distance 6,000 ly, age 1 billion , about 1,500 stars total, fairly densely-packed center, integrated magnitude about 9

Ozeren et al 2014, New , v32, p36

Michael L Allen Sagitta and Vulpecula PDLSP ’19 14 / 29 The Coathanger asterism

Michael L Allen Sagitta and Vulpecula PDLSP ’19 15 / 29 M71

Globular cluster, also called the Angelfish cluster and the Arrowhead cluster, NGC 6838 Discovered in 1745 by Jean-Philippe Loys de Ch´eseaux Distance about 13,000 ly, apparent diameter 7 arcmin, age 10 , integrated magnitude about 8 (visual) Peculiar globular: small, loosely-packed globular, containing only a few 10,000 stars, relatively young GC, relatively metal-rich GC, no RR Lyrae variable stars

Michael L Allen Sagitta and Vulpecula PDLSP ’19 16 / 29 M71

Michael L Allen Sagitta and Vulpecula PDLSP ’19 17 / 29 Poodle cluster

Open cluster, also called NGC 6830, Collinder 406, Melotte 204 Distance about 6,000 ly, age about 125 million years, angular diameter about 9 arcmin, about 150 members, brightest member about 10th magnitude

Kharchenko et al, 2013, Astronomy and astrophysics, v558, p53

Michael L Allen Sagitta and Vulpecula PDLSP ’19 18 / 29 Poodle cluster

Michael L Allen Sagitta and Vulpecula PDLSP ’19 19 / 29 NGC 6823

Also known as Collinder 405, and Sharpless 2-86 Open cluster with emission A part of the active star-forming region called Vulpecula OB1 Distance about 6,000 ly, apparent diameter about 40 arcmin, The central cluster of stars is only a couple of ly across, with an age of only about 2 million years; remarkable for its pillars of dense gas, and Bok globules Integrated magnitude of about 7, about 100 stars, brightest one shines with 9th magnitude

Michael L Allen Sagitta and Vulpecula PDLSP ’19 20 / 29 NGC 6823

Michael L Allen Sagitta and Vulpecula PDLSP ’19 21 / 29

Planetary nebula Also known as Messier 27, Apple Core nebula, Diabolo nebula First PN to be discovered, discovered by 1764 Integrated magnitude of about 7, diameter 8 arcmin, distance 1,200 ly, physical extent about 1 ly, estimated age about 10,000 years Classic bipolar shape; about 4/5 of all PNs are non-spherical; cause of non-sphericity is unknown, but it is thought that central stars with companions may have non-spherical shaped PNs

Michael L Allen Sagitta and Vulpecula PDLSP ’19 22 / 29 Dumbbell nebula

Michael L Allen Sagitta and Vulpecula PDLSP ’19 23 / 29 The Black Widow

Is a , the burned out core of a massive star that exploded as a between 1 and 2 solar , size of a few km Spins once every 1.6 milliseconds Is eclipsed every 9 hours, for about 20 minutes, by a companion Is thought that the companion is being destroyed by its close proximity to the neutron star: strong tides, overfill, and evaporation of the brown dwarf in the pulsar’s wind of light and particles

Michael L Allen Sagitta and Vulpecula PDLSP ’19 24 / 29

Shocked hydrogen gas (green) and X-rays (red) of the pulsar moving rapidly through the

http://chandra.harvard.edu/photo/2003/b1957/b1957 comp.jpg

Michael L Allen Sagitta and Vulpecula PDLSP ’19 25 / 29 Black Widow pulsar

Artist’s impression of the pulsar moving through space

http://chandra.harvard.edu/photo/2003/b1957/b1957 ill1.jpg

Michael L Allen Sagitta and Vulpecula PDLSP ’19 26 / 29 Black Widow pulsar

Artist’s impression of the evaporation of its brown dwarf companion

http://chandra.harvard.edu/photo/2003/b1957/b1957 ill2.jpg

Michael L Allen Sagitta and Vulpecula PDLSP ’19 27 / 29 Final words

And now, with the hope that my work, even with its imperfections, may serve to foster a more intelligent interest in the nomenclature and “archaeology of practical astronomy”, I submit it to all lovers of the stars.

Richard Hinckley Allen (1899)

Michael L Allen Sagitta and Vulpecula PDLSP ’19 28 / 29 List of sources

Aladin (aladin.u-strasbg.fr/aladin.gml)

ADS - (https://ui.adsabs.harvard.edu/)

Richard Hinckley Allen, Star lore - their names and meanings (1899; reprinted by Dover 1963)

Constellation Guide (constellation-guide.com)

Deep Sky Forum (deepskyforum.com)

Ian Ridpath’s Star Tales (ianridpath.com)

Linda Hall Library (http://lhldigital.lindahall.org/cdm/ref/collection/astro atlas/id/37)

Simbad database (simbad.harvard.edu)

Stellarium desktop planetarium software (stellarium.org)

Wikimedia Commons (commons.wikimedia.org)

Michael L Allen Sagitta and Vulpecula PDLSP ’19 29 / 29

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