Star clusters (and other neat stuff) in Ophiuchus

Michael L Allen [email protected]

Palouse Divide Lodge Star Party 2016

Michael L Allen Ophiuchus PDLSP ’16 1 / 19 Quick facts

11th-largest constellation at 950 sq deg (2% of the sky) 5 stars brighter than 3 mag 62 Flamsteed stars (down to about 7 mag) hosts the radiant point of four meteor showers variously called Ophiuchids (May-June) location of Kepler’s Supernova (1604) is the “13th member” of the zodiac (Nov 29 – Dec 17)

Michael L Allen Ophiuchus PDLSP ’16 2 / 19 Mythological associations

Ophuichus, “to handle the serpent”, associated with Aesculapius, a son of Apollo and a god of medicine learned his healing from Chiron, the centaur he passed his knowledge to his descendents, eventually reaching Hippocrates (b. 460 BCE) Aesculapius’s claim: snake venom could either kill or cure he brought back from the dead Glaucus, son of Minos King of Crete, who had died from a snake bite Pluto felt that Aesculapius had overstepped his bounds and complained to Jupiter Jupiter sent an eagle, Aquila, to strike down Aesculapius Jupiter perserved Aesculapius in the sky from where he could be recalled if his healing skills should be needed

Michael L Allen Ophiuchus PDLSP ’16 3 / 19 Hevelius’s atlas (Danzig, 1687)

Michael L Allen Ophiuchus PDLSP ’16 4 / 19 Binocular and easy telescope clusters

All three of these clusters can be found using β Oph and γ Oph as guide stars.

From very easy to moderately easy, these are

Melotte 186, IC 4665, and Collinder 350.

Michael L Allen Ophiuchus PDLSP ’16 5 / 19 Binocular and easy telescope clusters

Melotte 186

originally thought a loosely-bound cluster, is now classified as an asterism of unassociated stars (Hipparchos satellite data) east of γ Ophiuchi (look for 4th mag quartet 66, 67, 68, & 70 Oph) about 4◦ diameter is a discarded constellation (!), “Taurus Poniatovii” or Poniatowski’s Bull, invented in 1777 by Martin Poczobut in honor of King Stanislaw August Poniatowski of Poland and Lithuania few dozen stars brighter than 7th or 8th mag binary star: 67 Ophiuchi, 4.0/8.1 mag, 54 arcsec binary star: 70 Ophiuchi, 4.2/6.2 mag, 6 arcsec

Michael L Allen Ophiuchus PDLSP ’16 6 / 19 Binocular and easy telescope clusters

Melotte 186

contains Barnard’s star: about 3/4◦ NW of 66 Ophiuchi 2nd closest star system to the Sun (after α Cen) 9.6 mag, red & cool lower main sequence star (MK class M3.5 V) proper motion = 10 arcsec/year (about 1 Jupiter diameter every 4 years), it is the fastest proper motion star in the sky; first measured by E.E. Barnard in 1916 contains a bona fide open cluster: NGC 6633 extreme eastern edge, 5◦ SSE of 71 & 72 Oph 27 arcmin diameter about a dozen 8th mag stars about 1200 ly distant

Michael L Allen Ophiuchus PDLSP ’16 7 / 19 Binocular and easy telescope clusters

IC 4665

open star cluster, the “Summer Beehive” distance about 1100 ly about 1◦ diameter roughly solar composition [Fe/H] = -0.03 500-1500 member stars, about a dozen brighter than 9th mag binary star: Struve Σ 2216, 8.0/10.1 mag, 27 arcsec

Michael L Allen Ophiuchus PDLSP ’16 8 / 19 Binocular and easy telescope clusters

Collinder 350

open star cluster locate 1–2◦ south of γ Ophiuchus about 0.5◦ diameter about 900 ly distant faint: members stars are 9th mag or fainter binaries: not associated with the cluster South-Herschel 251 (HIP 86391/86379), 6.3/7.7 mag, 112 arcsec South 694, 6.7/7.3 mag, 79 arcsec 61 Ophiuchi, 6.1/6.5 mag, 21 arcsec

Michael L Allen Ophiuchus PDLSP ’16 9 / 19 Binocular and easy telescope clusters

Figure: Ophiuchus and Poniatowski’s Bull, from Urania’s Mirror, London, Figure: Mel 186 (center), IC 4665 1825. Credit: Wikimedia Commons. (upper right), Cr 350 (lower right). Credit: Wikimedia Commons.

Michael L Allen Ophiuchus PDLSP ’16 10 / 19 Four globular clusters

These four globular clusters are found near the center of Ophuichus, within the large triangle formed by the stars λ Oph, η Oph, and β Oph (Marfik, Sabik, and Cebalrai, respectively):

M10, M12, M14, and NGC 6366.

Michael L Allen Ophiuchus PDLSP ’16 11 / 19 Four globular clusters

General comparison Name mv Size Remarks M10 6 mag 20 arcmin rich cluster, concentrated center; near 30 Oph M12 7 mag 16 arcmin loose cluster, brightest members are 12th mag M14 8 mag 11 arcmin need 8–10in aperture to resolve NGC 6366 9 mag 6 arcmin hard to see in the glare of 5th mag HD 157950 (some maps identify this star as 47 Oph; this ID is in dispute)

Michael L Allen Ophiuchus PDLSP ’16 12 / 19 Four globular clusters

Figure: M10 and M12. FOV is 20 arcmin. Credit: POSS/DSS.

Michael L Allen Ophiuchus PDLSP ’16 13 / 19 Four globular clusters

Figure: M14 and NGC6366. FOV is 20 arcmin. Credit: POSS/DSS.

Michael L Allen Ophiuchus PDLSP ’16 14 / 19 Deep sky Ophiuchus

A list of difficult objects, require a dark sky, serious aperture, and possibly filters, and chosen to be best viewable over a wide field.

ρ Ophiuchi complex: star cloud with (apparent) triple star and nebula, 60×25 arcmin elongated N–S, about 360 ly distant - ρ Oph itself is a double star, 5.1/5.7 mag, 2.9 arcsec dark nebulae; Ophiuchus is rich in them; perhaps best known is Barnard 72 called Barnard’s dark S-nebula, or “The Snake” deeply opaque 1.5◦ NNE of θ Oph, 30 arcmin in extent

Michael L Allen Ophiuchus PDLSP ’16 15 / 19 Deep sky Ophiuchus

Figure: Star formation in the rho Ophiuchus region. Antares is at lower-center. Credit: Wikimedia Commons; ESO/DSS2.

Michael L Allen Ophiuchus PDLSP ’16 16 / 19 Deep sky Ophiuchus

Figure: Barnard 72, the Snake Nebula. Credit: Wikimedia Commons; John Belushi.

Michael L Allen Ophiuchus PDLSP ’16 17 / 19 Print resources

Articles in The observer’s handbook 2016, David F. Chapman (ed), RASC.

Alan Dyer, “The Messier catalogue” Alan Dyer, “The finest NGC objects” Paul Grey, “Dark nebulae” Alan Dyer and Alister Ling, “Deep-sky challenge objects” Chris Beckett, “Wide-field wonders”

Hewitt-White, Ken. “Bearing down on the serpent bearer.” SkyNews, July/August 2016.

Hewitt-White, Ken. “Ophiuchus.” SkyNews, July/August 2016.

Hewitt-White, Ken. “Messiers across the midriff.” SkyNews, July/August 2015.

Michael L Allen Ophiuchus PDLSP ’16 18 / 19 Online resources

Johnson, Andrew L. “The magnitude 7 star atlas project.” Accessed 2016-06-07. http://www.astro.cz/mirror/atlas/

Kronberg, Christine. “Ophiuchus.” Version 1999-09-08. http://maps.seds.org/Stars en/Fig/ophiuchus.html

Ridpath, Ian. “Star Tales.” Accessed 2016-06-05. http://www.ianridpath.com/startales/contents.htm

Stellarium Software. http://www.stellarium.org/

Torres, J.R. “JR’s website on deep-sky astronomy.” Accessed 2016-06-07. http://www.uv.es/jrtorres/

Wikimedia Commons. https://commons.wikimedia.org/wiki/Main Page

Michael L Allen Ophiuchus PDLSP ’16 19 / 19