Starship Asterisk*

[quote="starsurfer"]I'm a big fan of star clusters due to their simple elegance, it's nice to see NGC 2419 represented here as it is one of the most distant in the Milky Way. The most distant globular cluster in the Milky Way is AM-1 in the constellation of Horologium with a distance of 390,000 light years. In fact, last year, the discovery of a new remote globular cluster in the constellation of Crater was announced and interestingly has been discovered on three separate occasions, see [url=http://www.cielocean.fr/uploads/images/FichiersPDF/1403.6593v1.pdf]here[/url], [url=http://www.cielocean.fr/uploads/images/FichiersPDF/1403.3406v3.pdf]here[/url] and [url=http://www.cielocean.fr/index.php?page=LDu-11]first by the French amateur astronomer Pascal Le Dû[/url]. However there is the possibility that it might be a dwarf satellite of the Milky Way rather than a globular cluster.[/quote]
It feels weird to quote myself but the [url=http://www.chart32.de/index.php/component/k2/item/120]CHART32 team have released an image of AM-1[/url].

The funny thing about that Tweet is that a lot of people responded with comments about NASA but that was an ESA release. They both do their own releases and sometimes for especially big ones they do them simultaneously but this image release was done by ESA. Of course, NASA still gets first mention and the bigger logo on the telescope for developing the larger part of the telescope (all but the solar panels), but our European partners often get overlooked in the mentions completely.

The White House actually is paying attention to the sky and sending updates. I received this today. I suppose it could be an APOD someday but here's a preview of another Intergalactic Wanderer; this one in a substantially different neighborhood and potentially less "wanderful" ?

Hubble Peers into the Most Crowded Place in the Milky Way

[attachment=0]Dense Cluster.jpg[/attachment]

Associated text - This NASA/ESA Hubble Space Telescope image presents the Arches Cluster, the densest known star cluster in the Milky Way. It is located about 25,000 light-years from Earth in the constellation of Sagittarius (The Archer), close to the heart of our galaxy, the Milky Way. It is, like its neighbor the Quintuplet Cluster, a fairly young astronomical object at between two and four million years old. The Arches cluster is so dense that in a region with a radius equal to the distance between the sun and its nearest star there would be over 100,000 stars! At least 150 stars within the cluster are among the brightest ever discovered in the Milky Way.
These stars are so bright and massive that they will burn their fuel within a short time (on a cosmological scale that means just a few million years). Then they will die in spectacular supernova explosions. Due to the short lifetime of the stars in the cluster the gas between the stars contains an unusually high amount of heavier elements, which were produced by earlier generations of stars.
________________________________________
P.S. -- The President liked this photo so much, he tweeted about it!
Dr. John P. Holdren
Director, Office of Science and Technology Policy
The White House

The explanation to the APOD starts "Three objects stand out in this thoughtful telescopic image...". I would say there are four but the spiky star to the bottom left does not seem worthy of mention, poor thing :cry:.

[quote="henrystar"]Ain't we lucky that neither of those BRIGHT local stars is directly in front of the nice globular. Hey, I wonder, is there ANY nice nebula that is messed up by a foreground star? (If not, is that evidence of God's kindness to us astronomers?)[/quote]

This GC is quite a small object in terms of its angular diameter. That's one of the reasons I like this image so much -- it is quite narrow but also quite deep. Most of the well known nebulae exist within the Milky Way and appear much larger, so any unrelated stars in the foreground are less likely to interfere significantly.

[quote="henrystar"]Ain't we lucky that neither of those BRIGHT local stars is directly in front of the nice globular. Hey, I wonder, is there ANY nice nebula that is messed up by a foreground star? (If not, is that evidence of God's kindness to us astronomers?)[/quote]

I don't know of any bright star right in front of a nebula, but what about bright stars right next to faint galaxies? There is [url=http://members.aon.at/zwach/Astronomie/Astronomie_images/Leo/Dwarf%20Elliptical%20Galaxy%20Leo%20I%20(UGC%205470,%20DDO%2074)_IC%20591_1024-klein.jpg]eleventh magnitude UGC 5470 right next to first magnitude star Regulus[/url]. Ouch! Tenth magnitude NGC 404 isn't doing so well in the glare of second magnitude Mirach, either. It is [url=http://www.docdb.net/img/dso/ngc/4/ngc_404_mirach_and_ngc_404_dss2.jpg]the Ghost of Mirach[/url]!

Ann

Ain't we lucky that neither of those BRIGHT local stars is directly in front of the nice globular. Hey, I wonder, is there ANY nice nebula that is messed up by a foreground star? (If not, is that evidence of God's kindness to us astronomers?)

Looks like a halo of red giants around the cluster?

[quote="BobStein-VisiBone"]From the [url=http://csep10.phys.utk.edu/astr162/lect/milkyway/components.html]last link[/url] in the article, to a page at the University of Tennessee at Knoxville:

[quote]Dating of globular clusters by their turnoff points indicates that they may be as old as 15 billion years and are the oldest components of the galaxy. This implies that the galaxy itself is at least 15 billion years old.[/quote]

:shock:

Metalicity and poverty notwithstanding, with the age of the universe at [url=http://map.gsfc.nasa.gov/universe/uni_age.html]13.77 billion[/url] years, surely they can't be [i]that[/i] old?[/quote]

Right you are. Globular clusrters are [i]not[/i] older than the universe! They are typically about 12 billion years old.

Ann

I'm a big fan of star clusters due to their simple elegance, it's nice to see NGC 2419 represented here as it is one of the most distant in the Milky Way. The most distant globular cluster in the Milky Way is AM-1 in the constellation of Horologium with a distance of 390,000 light years. In fact, last year, the discovery of a new remote globular cluster in the constellation of Crater was announced and interestingly has been discovered on three separate occasions, see [url=http://www.cielocean.fr/uploads/images/FichiersPDF/1403.6593v1.pdf]here[/url], [url=http://www.cielocean.fr/uploads/images/FichiersPDF/1403.3406v3.pdf]here[/url] and [url=http://www.cielocean.fr/index.php?page=LDu-11]first by the French amateur astronomer Pascal Le Dû[/url]. However there is the possibility that it might be a dwarf satellite of the Milky Way rather than a globular cluster.

From the [url=http://csep10.phys.utk.edu/astr162/lect/milkyway/components.html]last link[/url] in the article, to a page at the University of Tennessee at Knoxville:

[quote]Dating of globular clusters by their turnoff points indicates that they may be as old as 15 billion years and are the oldest components of the galaxy. This implies that the galaxy itself is at least 15 billion years old.[/quote]

:shock:

Metalicity and poverty notwithstanding, with the age of the universe at [url=http://map.gsfc.nasa.gov/universe/uni_age.html]13.77 billion[/url] years, surely they can't be [i]that[/i] old?

Globular clusters are fascinating and mysterious. What formed them? What was the universe like when they were born?

In any case, globular clusters come in basically two kinds, very low-metal ones with numerous so called RR Lyrae variables (which are exellent, if slightly faint, standard candles for distance estimates), and higher metal-ones with very few, if any, RR Lyrae variables. The globulars that are rich in RR Lyrae variables also have a rich population of blue horizontal stars, whereas the higher-metal, RR-Lyrae-poor globulars have few or no blue horzontal stars.

[float=left][img2]http://community.dur.ac.uk/ian.smail/gcCm/gcCm_hr_plot.gif[/img2][c][size=85]Source: http://community.dur.ac.uk/ian.smail/gcCm/gcCm_intro.html[/size][/c][/float] This picture shows the horizontal branch (HB) of globular clusters very well. The blue horizontal branch is the blue part of the horizontal branch. The RR Lyrae stars are located in the "gap" of the horizontal branch. Most of the bright globulars of the Milky Way are very metal-poor and have blue horizontal branches and RR Lyrae stars. One example is Omega Centauri, which contains [i]at least[/i] [url=http://arxiv.org/abs/astro-ph/0602055]74 RR Lyrae stars[/url]. Compare that with more metal-rich globular cluster 47 Tuc, which may have only [url=http://articles.adsabs.harvard.edu/cgi-bin/nph-iarticle_query?bibcode=1980AJ.....85...36K&db_key=AST&page_ind=0&data_type=GIF&type=SCREEN_VIEW&classic=YES]one RR Lyrae star[/url] altogether! [url=http://www.astro.queensu.ca/~courteau/Phys216/images/202pics/47tuc.gif]47 Tuc has a very short horizontal branch[/url] and lacks the blue part of it completely.

What sort of beast is NGC 2419, then?

[quote]
ABSTRACT
We present a new, deep (V ~ 26) study of the Galactic globular cluster NGC 2419 based on B, V, I time-series CCD photometry over about 10 years and extending beyond the cluster published tidal radius. We have identified 101 variable stars, of which 60 are new discoveries, doubling the known RR Lyrae stars and including 12 SX Phoenicis stars. The average period of the RR Lyrae stars (Pab = 0.662 days and Pc = 0.366 days, for fundamental-mode—RRab—and first-overtone pulsators, respectively) and the position in the period-amplitude diagram both confirm that NGC 2419 is an Oosterhoff II cluster. The average apparent magnitude of the RR Lyrae stars is V = 20.31 ± 0.01 (σ = 0.06, 67 stars) and leads to the distance modulus μ0 = 19.60 ± 0.05. The color-magnitude diagram, reaching about 2.6 mag below the cluster turnoff, does not show clear evidence of multiple stellar populations. Cluster stars are found until r ~ 10.5', and possibly as far as r ~ 15', suggesting that the literature tidal radius might be underestimated. No extratidal structures are clearly detected in the data. [size=110][b][color=#0040FF]NGC 2419 has many blue stragglers and a well-populated horizontal branch extending from the RR Lyrae stars down to an extremely blue tail ending with the "blue hook[/color][/b][/size]," for the first time recognized in this cluster. The red giant branch is narrow, ruling out significant metallicity spreads. [size=110][b][color=#FF0000]Our results seem to disfavor the interpretation of NGC 2419 as either having an extragalactic origin or being the relict of a dwarf galaxy tidally disrupted by the Milky Way[/color].[/b][/size]

On the Remote Galactic Globular Cluster NGC 2419 - ResearchGate. Available from: http://www.researchgate.net/publication/230914048_On_the_Remote_Galactic_Globular_Cluster_NGC_2419 [accessed Jun 4, 2015].[/quote]

The colors, larger font size and use of bold text are my additions. But according to this article, NGC 2419 has probably been born in the Milky Way, or at least it appears to be more associated with the Milky Way than with any other galaxy.

Ann

[quote="Boomer12k"]
How can globulars have stars as nearly as old as the Universe...and STILL be Metal Poor????
:---[===] *[/quote]
Live in a poor part of town, that's all!

Did not know there was a Globular so far out... Thought they were all in the halo. Learning all the time....

If left over from some merger, but got "left out", I find that hard to agree with. It holds its shape well, it seems...but then the closer ones do too... maybe it is just inherent. I wonder if ALL globulars at one time were..."Free Wandering"...and just gravitated together....but "into each other"... Or...if somehow THIS one was SPED UP, and lost contact, and is now "Adrift"... :cry: Me sad...might be lost, adrift on ocean of space...sniff.... poor globular.

How can globulars have stars as nearly as old as the Universe...and STILL be Metal Poor????

:---[===] *

I figured its distance would isolate it and make it just a bit easier to study some aspects of the cluster. There are others along the Milky Way's disk with so many stars in front and behind that it makes it hard to tell what's part of the glob and what's not. This cluster has been used frequently by the STScI to obtain photometric zero points for Hubble's various instruments... despite obtaining some nice images in the process, there haven't been any image releases for the object. It's a thankless job.

I really like this APOD. Very interesting. Thanks.

[url=http://apod.nasa.gov/apod/ap150604.html][img]http://apod.nasa.gov/apod/calendar/S_150604.jpg[/img] [size=150]NGC 2419 - Intergalactic Wanderer[/size][/url]

[b] Explanation: [/b] Three objects stand out in [url=http://bf-astro.com/ngc2419/ngc2419.htm]this thoughtful telescopic image[/url], a view toward the mostly stealthy constellation [url=http://en.wikipedia.org/wiki/Lynx_%28constellation%29]Lynx[/url]. The two brightest (the spiky ones) are nearby stars. The third is the remote globular star cluster [url=http://messier.seds.org/xtra/ngc/n2419.html]NGC 2419[/url], at distance of nearly 300,000 light-years. [url=http://arxiv.org/abs/0712.0729]NGC 2419[/url] is sometimes called "the Intergalactic Wanderer", an appropriate title considering that the distance to the Milky Way's satellite galaxy, the [url=http://apod.nasa.gov/apod/ap130528.html]Large Magellanic Cloud[/url], is only about 160,000 light-years. Roughly similar to other large globular star clusters like [url=http://apod.nasa.gov/apod/ap140529.html]Omega Centauri[/url], NGC 2419 is itself intrinsically bright, but appears faint because it is so far away. [url=http://arxiv.org/abs/1310.4499]NGC 2419[/url] may really have an extragalactic origin as, for example, the remains of a small galaxy [url=http://apod.nasa.gov/apod/ap080619.html]captured and disrupted[/url] by the Milky Way. But its extreme distance makes it difficult to [url=http://arxiv.org/abs/astro-ph/9707048]study[/url] and compare its properties with other globular clusters that roam the halo of [url=http://csep10.phys.utk.edu/astr162/lect/milkyway/components.html]our Milky Way galaxy[/url].

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