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Similar to Blue Stragglers and Star Clusters
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Blue Stragglers and Star Clusters
- 1. Star Cluster Evolution and Blue Stragglers
- 2. Herschel 400 Catalogue (deep blue)
- 3. Star Clusters • Star clusters have been seen by humans since we’ve have looked up at night • Some clusters are older, and strongly bound by gravity (Globular Clusters) – about 150 in our Galaxy • Some are younger and seem to be more spread out (Open Clusters) • Some are between these two types (Intermediate Clusters) • Clusters usually range to 30 l. y. across
- 4. Globular Cluster M22 in 1665 by Abraham Ihl © Hunter Wilson
- 5. GC Omega Centauri in 1677 by Edmund Halley © ESO http://www.eso.org/public/outreach/press-rel/pr-2008/phot-44-08.html
- 6. OC - The Pleiades (M45) Mississauga 2010, 10x zoom lens, Canon Rebel, 10 exposures integrated with RegiStax, post © 2006 Filip Lolić processing Photoshop
- 7. OC - M67 by Johann Gottfried Koehler in 1779 © 2MASS/UMass/IPAC-Caltech/NASA/NSF Mississauga 2009, 25x 4-inch reflector, 50 http://ipac.caltech.edu/2mass exposures integrated with RegiStax, post processing Photoshop
- 8. OC – Hyades © 2006, Todd Vance
- 9. Star Cluster Studies • At the beginning of the 20th century astronomers began to record colour and luminosity of the stars • These colour-luminosity diagrams also known as Hertzprung-Russel diagrams supported the theories of star evolution • But these diagrams were only “snapshots” in time (no one has actually observed evolution of clusters in real time)
- 10. Col-Mag – Pleiades and Hyades © 2010, Andrew James
- 11. Older Open Clusters © 2006, Josef K
- 12. Color-Luminosity / HR Basics © 2001 Carolyn Brinkworth and Claire Thomas
- 13. Color-Luminosity Over Time © 2003-2011 Robert W. O'Connell
- 14. Star Cluster Theories • Stars in a cluster are born at the same general time (therefore be of the same age) • Stars will all generally be of the same composition • Stars will be located within the same 30 l. y. sphere, cube, etc. • Stars will travel through the Galaxy within the same group until extinction
- 16. Blue Straggler Discovery • 1953, Allan Sandage (Palomar Observatory) • Found stars that were much younger than the theory predicted • They were sitting where the young, hot blue stars “used” to be on the HR diagram • They should have evolved out of this position billions of years earlier!!!
- 17. 47 Tucanae (Blue Highlights) © 2000 May 20, The Astrophysical Journal, 535:298-303
- 18. M3 (Blue Highlights) ©1998 The McGraw-Hill Companies
- 19. ω Centauri (Blue Highlights) © 2009, The American Astronomical Society
- 20. Blue Straggler Analogy • Star clusters were like cocktail parties • Everyone there was part of the same club • Then all of a sudden he found clusters where the room was full of 80-year-olds talking about their Oldsmobiles and 5 or 6 20-year- olds talking about tuition
- 21. Blue Straggler Properties • Still burning hydrogen • Hotter than the main sequence turn-off point for the cluster • Radially as large or larger than the ZAMS • Still travelling with the cluster as a group
- 22. Blue Straggler Explanations • Original stellar evolution theory is wrong • Original cluster beginnings are wrong • They are just visiting stars that got tangled up in the cluster • They have sucked up materials that were left around for a very long time • Star collisions • They are a merged binary pair
- 23. Blue Straggler Ideas • Evolution theory is likely right • Cluster beginnings is much more right than wrong • Some stragglers are right in the centers of clusters (hard to say they’re captured) • Sucked up materials would probably not be hydrogen • Collisions are theoretically possible • This leaves merged binary pairs
- 25. Blue Straggler Argument • Collisions are less probable because the gas cloud and stars are moving together in space • Capture will happen when stars graze each other at low angles of approach • But in these clusters there seems to be a slight to a large expanding nature – so stars are moving apart • More probable in Globular Clusters (will be rotating fast like a figure skater bringing their arms in)
- 26. Blue Straggler Tests • If blue stragglers are from merging of close binary stars: – we should be able to see this variability in observations in these clusters and – See a high population of un-merged binaries in younger clusters, and – A maturing number in older clusters – Infrared observations of star-brown dwarf binaries containing lots of hydrogen
- 27. Blue Straggler Searchers • Aaron M. Gelle • Robert D. Mathieu • Currently waiting for data from Hubble to find white dwarf binary partners circling these blue stragglers in very near orbits • Results will be this year (2012)
Editor's Notes
- Messier is an elliptical globular cluster in the constellation Sagittarius, near the Galactic bulge region. It is one of the brightest globulars that is visible in the night sky. M22 was one of the first globulars to be discovered in 1665 by Abraham Ihleand it was included in Charles Messier's catalog of comet-like objects on June 5, 1764. It was one of the first globular clusters to be carefully studied first by Harlow Shapley in 1930. He discovered roughly 70,000 stars and found it had a dense core.
- Omega Centauri is a globular cluster in the constellation of Centaurus, discovered by Edmond Halley in 1677 who listed it as a nebula. Omega Centauri had been listed in Ptolemy's catalog 2000 years ago as a star. Lacaille included it in his catalog as number I.5. It was first recognized as a globular cluster by the English astronomer John William Herschel in the 1830s.Orbiting the Milky Way, it is both the brightest and the largest known globular cluster associated with our galaxy (1.6 Em). Of all the globular clusters in the Local Group of galaxies, only Mayall II in the Andromeda Galaxy is brighter and more massive. ω Centauri is so different from other galactic globular clusters that it is thought to be of different origin.
- ThePleiadesis an open star cluster containing middle-aged hot B-type stars located in the constellation of Taurus. It is among the nearest star clusters to Earth and is the cluster most obvious to the naked eye in the night sky. The cluster is dominated by hot blue and extremely luminous stars that have formed within the last 100 million years. Dust that forms a faint reflection nebulosity around the brightest stars was thought at first to be left over from the formation of the cluster (hence the alternate name Maia Nebula after the star Maia), but is now known to be an unrelated dust cloud in the interstellar medium that the stars are currently passing through. Astronomers estimate that the cluster will survive for about another 250 million years, after which it will disperse due to gravitational interactions with its galactic neighborhood.
- M67 is not the oldest known open cluster, but there are few Galactic clusters known to be older, and none of those are as close as M67. M67 is an important laboratory for studying stellar evolution, since the cluster is well populated, obscured by negligible amounts of space dust, and all its stars are at the same distance and age, except for approximately 30 anomalous blue stragglers, whose origins are not fully understood.
- The Hyades is the nearest open cluster to the Solar System and one of the best-studied of all star clusters. The Hipparcos satellite, the Hubble Space Telescope, and infrared color-magnitude diagram fitting have been used to establish a distance to the cluster's center of ~153 ly (47 pc).[1][2][3][4] The distance established via the three independent analyses agree, thereby making the Hyades an important rung on the cosmic distance ladder. The cluster consists of a roughly spherical group of hundreds of stars sharing the same age, place of origin, chemical content, and motion through space.[1][5] From the perspective of observers on Earth, the Hyades Cluster appears in the constellation Taurus, where its brightest stars form a "V" shape along with the still brighter red giant Aldebaran. However, Aldebaran is completely unrelated to the Hyades, as it is located much closer to Earth (hence its apparent brightness) and merely happens to lie along the same line of sight.
- 7 Tucanae (NGC 104) or just 47 Tuc is a globular cluster located in the constellation Tucana. It is about 16,700 light years away from Earth, and 120 light years across. It can be seen with the naked eye, with a visual magnitude of 4.0. Its number comes not from the Flamsteed catalogue, but the more obscure 1801 "AllgemeineBeschreibung und Nachweisung der GestirnenebstVerzeichniss" compiled by Johann Elert Bode. 47 Tucanae is included in Sir Patrick Moore's Caldwell catalogue as C106.
- Messier 3 (also known as M3 or NGC 5272) is a globular cluster of stars in the northern constellation of Canes Venatici. It was discovered by Charles Messier on May 3, 1764, and resolved into stars by William Herschel around 1784. Since then, it has become one of the best-studied globular clusters. Identification of the cluster's unusually large variable star population was begun in 1913 by American astronomer Solon Irving Bailey and new variable members continue to be identified up through 2004.
- Omega Centauri (ω Cen) or NGC 5139 is a globular cluster in the constellation of Centaurus, discovered by Edmond Halley in 1677 who listed it as a nebula. Omega Centauri had been listed in Ptolemy's catalog 2000 years ago as a star. Lacaille included it in his catalog as number I.5. It was first recognized as a globular cluster by the English astronomer John William Herschel in the 1830s. ("Omega Centauri" is a Bayer designation, even though the object is a cluster.)