NGC 2419, Intergalactic Wanderer

NGC 2419
NGC 2419: Intergalactic Wanderer in Lynx; 500 mm Cassegrain 5800 mm f/11.4; SBIG STL11K; 60+20+20+20 min LRGB; Bernese Highlands; © 2005 Radek Chromik

History

The globular cluster NGC 2419 was discovered by Wilhelm Herschel on December 31, 1788 and cataloged as I 218 (class I = bright nebulae). He described it as follows: «considerably bright, round, very gradually much brighter in the middle, about 3' diameter» [465]

Physical Properties

At a distance of 83 kpc (about 270'000 light-years), NGC 2419 is one of the most distant globular clusters, more distant than the Large Magellanic Cloud. Until recently it was thought not to belong to the halo of the Milky Way, which is why it was nicknamed the «Intergalactic Wanderer». [145, 196]

NGC 2419
NGC 2419: Image taken with the Hubble Space Telescope [301]

Measurements by the Hubble Space Telescope and the Gaia Space Telescope showed that NGC 2419 orbits the center of the Milky Way in a nearly polar orbit of about 53 kpc to 98 kpc (173'000 to 320'000 light years) and takes about four billion years to do so. This and the common sense of rotation around the Milky Way make it very likely that this globular cluster once belonged to the Sagittarius dwarf elliptical galaxy (Sgr dSph, Sag DEG). [302]

Usually, stars within globular clusters show very similar properties, such as age and metal content (any element heavier than helium in astronomy), since the stars formed at the same time. It was also assumed that this similarity would hold true for the helium content of each star within the globular cluster. Studies of NGC 2419 using the Hubble Space Telescope showed that this assumption is not always true. This globular cluster features two distinct populations of red giants, one of which is unusually rich in helium. Other elements such as B. nitrogen also show strong differences in the individual stars. This population of helium-rich stars was found primarily at the center of the globular cluster, and they also appear to rotate differently from the other population. This raises questions as to whether both stellar populations formed together or are of different origins. [301]

«Revised New General Catalogue and Index Catalogue» Dr. Wolfgang Steinicke, 2021 [277]
DesignationNGC 2419
TypeGCL (II)
Right Ascension07h 38m 08.5s
Declination+38° 52' 57"
Diameter4.60 arcmin
Visual magnitude10.3 mag
Dreyer DescriptionpB, pL, lE 90°, vgbM, * 7·8 267°, 4' dist
IdentificationGCL 12, Intergalactic wanderer

Finder Chart

NGC 2419 is located in a star-poor region in the constellation Lynx, about 7° north of bright star Castor (α Geminorum). The best viewing time is November to April.

Chart NGC 2419
Chart created using SkySafari 6 Pro and STScI Digitized Sky Survey. [149, 160]

Visual Observation

320 mm Aperture: Two stars of about the same brightness serve as pointers, along which the «Intergalactic Wanderer» follows. The globular cluster NGC 2419 can be seen as a globular nebula, but not resolved into individual stars. The center appears a little punctiform brightened. — 12.5" f/4.5 Ninja-Dobsonian, Glaubenberg, 25. 3. 2022, Eduard von Bergen

400 mm Aperture: At low magnification (21 mm Tele Vue Ethos, 85x) the globular cluster appears as a round nebula in the extension of two bright mag 7 stars. One of them is a binary. A very beautiful sight. With the two other, slightly fainter stars at the other end, it looks a bit like an arrow flying toward the globular cluster. When the air is still, one believes one can see small stars in the globular cluster. In the 16 mm Nagler eyepiece (112x) these turn out to be fine neighboring stars and stand out more clearly. The cluster itself remains nebulous with a slightly brighter center. The view is most beautiful in the 9 mm Nagler eyepiece (200x). The contrast from the globular cluster to the sky background appears best here and the specialty with the two bright stars offers a nice overall picture. Even at higher magnifications (up to 450x), the globular cluster cannot be resolved into individual stars. It is too dark for that. — Taurus T400 f/4.5 Dobsonian, Glaubenberg, SQM-L 20.9, 25. March 2022, 21:00 CET, Bernd Nies

References

145SIMBAD astronomical database; simbad.u-strasbg.fr/simbad
149SkySafari 6 Pro, Simulation Curriculum; skysafariastronomy.com
160The STScI Digitized Sky Survey; archive.stsci.edu/cgi-bin/dss_form
196Celestial Atlas by Curtney Seligman; cseligman.com/text/atlas.htm (2020-12-28)
277«Historische Deep-Sky Kataloge» von Dr. Wolfgang Steinicke; klima-luft.de/steinicke (2021-02-17)
301The two mysterious populations of NGC 2419; esahubble.org/images/potw1908a (2021-04-06)
302«The power of teaming up HST and Gaia: the first proper motion measurement of the distant cluster NGC 2419» D. Massari, L. Posti, A. Helmi, G. Fiorentino1 and E. Tolstoy; A&A Volume 598, February 2017; DOI:10.1051/0004-6361/201630174
465«Catalogue of 500 new nebulae, nebulous stars, planetary nebula:, and clusters of stars; with remarks on the construction of the heavens» William Herschel, Philosophical Transactions of the Royal Society of London, 1 January 1802; DOI:10.1098/rstl.1802.0021