Messier 19

From Wikipedia, the free encyclopedia

 

Jump to: navigation, search

Messier 19
Messier 19 by Hubble Space Telescope; 2.5′ view Credit: NASA/STScI/WikiSky
Observation data (J2000 epoch)
Class	VIII[1]
Constellation	Ophiuchus
Right ascension	17h 02m 37.69s[2]
Declination	-26° 16′ 04.6″[2]
Distance	28.7 kly (8.8 kpc)[3]
Apparent magnitude (V)	+7.47[2]
Apparent dimensions (V)	17′.0
Physical characteristics
Mass	1.10×106[3] M☉
Radius	70 ly
Metallicity	–1.53[4] dex
Estimated age	11.90 Gyr[4]
Other designations	NGC 6273, GCl 52[2]
See also: Globular cluster, List of globular clusters

Messier 19 or M19 (also designated NGC 6273) is a globular cluster in the constellation Ophiuchus. It was discovered by Charles Messier on June 5, 1764^[5] and added to his catalogue of comet-like objects that same year. It was resolved into individual stars by William Herschel in 1784. His son, John Herschel, described it as "a superb cluster resolvable into countless stars".^[6] The cluster is located 4.5° WSW of Theta Ophiuchi and is just visible as a fuzzy point of light using 50 mm (2.0 in) binoculars. Using a telescope with a 25.4 cm (10.0 in) aperture, the cluster shows an oval appearance with a 3′ × 4′ core and a 5′ × 7′ halo.^[5]

M19 is one of the most oblate of the known globular clusters.^[6] This flattening may not accurately reflect the physical shape of the cluster because the emitted light is being strongly absorbed along the eastern edge. This is the result of extinction caused by intervening gas and dust. When viewed in the infrared, the cluster shows almost no flattening.^[7] It lies at a distance of about 28.7 kly (8.8 kpc) from the Solar System,^[3] and is quite near to the Galactic Center at only about 6.5 kly (2.0 kpc) away.^[8]

This cluster contains an estimated 1,100,000 times the mass of the Sun^[3] and it is around 11.9 billion years old.^[4] The stellar population includes four Cepheids and RV Tauri variables, plus at least one RR Lyrae variable for which a period is known.^[9] Observations made during the ROSAT mission failed to reveal any low-intensity X-ray sources.^[10]

• 

  Messier 19 with amateur telescope

• 

  Messier 19 from 2MASS; wide view

[edit] References

1. ^ Shapley, Harlow; Sawyer, Helen B. (August 1927), "A Classification of Globular Clusters", Harvard College Observatory Bulletin (849): 11–14, Bibcode 1927BHarO.849...11S.
2. ^ ^{a b c d} "SIMBAD Astronomical Object Database", Results for NGC 6273, http://simbad.u-strasbg.fr/Simbad, retrieved 2006-11-16.
3. ^ ^{a b c d} Boyles, J. et al. (November 2011), "Young Radio Pulsars in Galactic Globular Clusters", The Astrophysical Journal 742 (1): 51, arXiv:1108.4402, Bibcode 2011ApJ...742...51B, doi:10.1088/0004-637X/742/1/51.
4. ^ ^{a b c} Forbes, Duncan A.; Bridges, Terry (May 2010), "Accreted versus in situ Milky Way globular clusters", Monthly Notices of the Royal Astronomical Society 404 (3): 1203–1214, arXiv:1001.4289, Bibcode 2010MNRAS.404.1203F, doi:10.1111/j.1365-2966.2010.16373.x.
5. ^ ^{a b} Thompson, Barbara Fritchman (2007), Illustrated Guide to Astronomical Wonders, Diy Science, O'Reilly Media, Inc., p. 331, ISBN 0596526857, http://books.google.com/books?id=ymt9nj_uPhwC&pg=PA331.
6. ^ ^{a b} Burnham, Robert (1978), Burnham's Celestial Handbook: An Observer's Guide to the Universe Beyond the Solar System, Dover Books on Astronomy, 2 (2nd ed.), Courier Dover Publications, p. 1263, ISBN 0486235688, http://books.google.com/books?id=wB9uZ9lH5bgC&pg=PA1263.
7. ^ van den Bergh, Sidney (May 2008), "The Flattening of Globular Clusters", The Astronomical Journal 135 (5): 1731–1737, arXiv:0802.4061, Bibcode 2008AJ....135.1731V, doi:10.1088/0004-6256/135/5/1731.
8. ^ Bica, E. et al. (April 2006), "Globular cluster system and Milky Way properties revisited", Astronomy and Astrophysics 450 (1): 105–115, arXiv:astro-ph/0511788, Bibcode 2006A&A...450..105B, doi:10.1051/0004-6361:20054351.
9. ^ Clement, Christine M. et al. (November 2001), "Variable Stars in Galactic Globular Clusters", The Astronomical Journal 122 (5): 2587–2599, arXiv:astro-ph/0108024, Bibcode 2001AJ....122.2587C, doi:10.1086/323719.
10. ^ Verbunt, F. (March 2001), "A census with ROSAT of low-luminosity X-ray sources in globular clusters", Astronomy and Astrophysics 368: 137–159, arXiv:astro-ph/0012261, Bibcode 2001A&A...368..137V, doi:10.1051/0004-6361:20000469.

Constellation Chart

The Serpent Holder

The group of stars has been known by the name Ophiuchus for two thousand years or more. What is not known, though, is why the name 'Serpent Holder' was assigned to them. Some suggest that the constellation represents Asclepius or Aesculapius, the healer of Greek myth whose cult was closely associated with serpents. This identification is by no means certain.

The Thirteenth Sign of the Zodiac:

When the zodiac was first delineated by the ancients, it consisted of twelve 'houses', each associated with one of twelve constellations that lay along the Ecliptic: Aries, Taurus, Gemini, Cancer, and so on. Since that time, gravitational effects on the orbit of the Earth, known as 'precession', have caused the line of the Ecliptic to change slightly. Specifically, it now passes through thirteen constellations, with Ophiuchus being the new addition. Where the Sun once passed directly from Scorpius into Sagittarius, it now spends nineteen days each year, from 30 November to 18 December, in the new 'house' of the Serpent Holder.

Stars In Ophiuchus

Barnard's Planetary System

The Star

A very cool and dim, main sequence red dwarf (M3.8 Ve), Barnard's Star may have less than 17 percent of Sol's mass (RECONS estimate), 15 percent of its diameter (Ochsenbein and Halbwachs, 1982, page 529), around 4/10,000th of its luminosity, and between 10 and 32 percent of its abundance of elements heavier than hydrogen -- "metallicity" (John E. Gizis, 1997, page 820). According to calculations by Dr. Sten Odenwald, substituting Barnard's Star for Sol would give the Earth such a dim and very red Sun that it would only be 100 times brighter than the Full Moon, and so the planet would freeze solid at the surface.

Unlike Sol, Barnard's appears to be an old disk star that formed before the galaxy became much enriched with heavy elements (Monet et al, 1992, page 655). While the star may already be around 10 billion years old, it may last another another 40 billion years or more before cooling into a black dwarf. A small star spot that was shrinking in size may have been observed on Barnard's recently with the Hubble Space Telescope (Benedict et al, 1998). Barnard's is a New Suspected Variable star designated NSV 9910. Some other useful star catalogue numbers include: Gl 699, Hip 87937, BD+04 3561a, LHS 57, LTT 15309, LFT 1385, G 140-24, Vys/McC 799, and Munich 15040.

Globular Cluster In Ophiuchus

M9

M9 is a compact globular cluster floating in the Milky Way about 3.5 degrees southeast of zeta Oph around underfoot of Serpent holder. Although the globular cluster has not so high stellar density, it has a diameter of at most 6 arc minutes. Small scopes cannot show you individual member stars although you will be able to appreciate a bright light spot like a nebula. This image shows you dark region without stars just southwest side of the cluster, it's a part of huge dark nebulosities distributed around the Milky Way.

M10 (NGC6254)

M10 (NGC6254) is a small globular cluster found out at body of Ophiuchus. It looks like tiny explosions of star with dense core; large telescopes are needed to resolve the individual stars. The cluster has real size of about 85 light years, and about 16 thousand light years away.

M12

M12 is a medium-sized globular cluster found in the pentagon of a constellation of Ophiuchus. The cluster is positioned at 3.5 degrees northwest of another globular of M10, and C. Messier discovered M12 just next day when he found M10. M12 is a globular that member stars are gathering very sparse, and you will be able to understand the fact if you compare that with M10. You can appreciate several star-chains are extending outward from the center with about 5 inches telescopes. Although the Ophiuchus pentagon contains three Messier's Globular clusters, it can be said that you can enjoy the M12 most easily in those.

M14

M14 is a small sized globular cluster, easternmost in three globulars with Messier's number (M10, M12 and M14) in a pentagon of Ophiuchus. M14 is lying at the west coast of the Milky Way in summer; so uncountable fine stars surround the cluster. The cluster has a fairly stellar density, you might need a telescope over 4" to resolve the individual stars. The cluster has a real size of about 55 light years and a distance of 23 thousand light years.

M19

This image shows you a small globular cluster of M19 lying around boundary between Ophiuchus and Scorpius. Although M19 belongs to a constellation of Ophiuchus, you can find out the cluster by tracing about 7.5 degrees east from Antares, alpha Scorpii. The cluster has very low density of member stars; only compact binocular can show you a nebula like image with a bit coarse impression, and you can recognize individual stars on outskirts only with small telescopes. Almost all of globular clusters have round shapes, some of those look like ellipse. This M19 has very long and narrow oval shape, you can see the cluster stretched in north south direction clearly.

// -->

M62

M62 is a tine globular cluster positioned almost on the boundary line between Scorpius and Ophiuchus. Another globular cluster of M19, lying about 4 degrees north of M62, has almost same declination with that of Antares, so you can find M62 by tracing from Antares via M19 easily. The globular cluster has a visual magnitude of 6.6 and a diameter of about 4.3 arc minutes, almost same as those of M19. But M19 has fairly smashed oval while this M62 has circular appearance. Furthermore by adding another bright globular of M4 lying just west of Antares, you will become aware of that globular clusters have unexpectedly variety of impressions.

M107

A tiny globular cluster of M107 is positioned at 2.6 degrees SSW of zeta Oph. The cluster has an apparent diameter of a bit larger than 2 arc minutes and a visual brightness of about 9, you can able to see it like a nebula only with binoculars. M107 has a concentration class of the tenth in twelve levels, fairly sparse globular. But the cluster is very small, so it's difficult to resolve member stars even if you see it through telescopes. There are various globular clusters around the field of Scorpius to Ophiuchus. M107 has a fairly poor appearance in those.

Nebula's In Ophiuchus

NGC 6369

NASA's Hubble Space Telescope has caught a glimpse of a colorful cosmic ghost, the glowing remains of a dying star called NGC 6369. The glowing apparition is known to amateur astronomers as the "Little Ghost Nebula," because it appears as a small, ghostly cloud surrounding the faint, dying central star

NGC6572

This image shows you a compact but easy-to-seeing planetary nebula of NGC6572, which is positioned in eastern region of Ophiuchus. You can find it around 11 degrees SE of alpha Oph, Ras Alhague. The nebula has an apparent size of about 15 arc seconds, you can distinguish NGC6572 from other stars and detect the nebula having bluishcolor only with compact telescopes, but no striking structures detected. NGC6572 is a remnant of star 2500 light years away.

IC4665

IC4665 is a very sparse open cluster scattered at about a degree north of beta Oph. The cluster has a apparent diameter of about 40 arc minutes, you can enjoy that with a portable binocular. This IC4665 has only 13 member stars. Outward looks of the cluster would be almost same as the Milky Way flowing just next on east. But the cluster has a sufficient big size; we can take it only with small photo lenses easily

LDN 1773

This Milky Way field image shows you very complicated dark nebulae around between Sagittarius and Scorpius. Especially it's noticeable a striking dark flow from the Milky Way to north of Antares, alpha Sco. You can find rho Ophiuchi at the western end of the flow and dimmed bluish light is being emitted. This diffused nebula has a number of IC4603-4, just a tiny part of the vast dark nebula stream. And there are many other red and orange diffused nebulae around Antares, one of most colorful, beautiful, and photogenic star fields in heavens. You can detect a huge lump of dark nebula stretched in east-west direction on the left-hand side of picture. The dark nebula has a span of about 7 degrees and real length is estimated about 100 light years. You can appreciate the nebula as a big hole in the Milky Way only with binoculars under conditioned sky. This patch in the Milky Way has a catalogue number of "LDN 1773" and a nickname of "Pipe Nebula" from its shape.

Diffused Nebula

A gigantic and round diffused nebula is spread around zeta Oph, which marks a foot of Serpent Holder. Of course the nebula is invisible for our naked eyes. We can see the nebula only on long exposed films under good conditioned sky with medium-ranged telephoto lenses like the Angelfish nebula in Orion. Many sky atlases have forgotten to record the shape of this nebula, it can be said that the nebula is not well known. And the nebula was discovered after astrophotography has been developed, has no major catalogue numbers. Though it's getting harder and harder to capture it under recent terrible light pollution year after year, this picture shows you some complicated structures of lanes of dark nebulae and various shading.

Galaxy In Ophiuchus

NGC6384

 

http://www.wingmakers.co.nz/universe/constellations/Ophiuchus.html