deepskytraveler
December 15th, 2015, 06:52 AM
Object of the Week December 13, 2015 – NGC 288
NGC 288, Cl Melotte 3, GCl 2, Bennett 5
Constellation: Sculptor
Type: Globular Cluster, Class X
RA: 00h 52m 45s
Dec: -26° 34’ 57”
Distance: 37,000 ly
Size: 13.0’
Mag: 8.1
This week’s OOTW is the unusual and obscure globular cluster, NGC 288.
19071906
Although it is moderately bright and large, it is located in a constellation relatively unknown to many Northern Hemisphere observers – Sculptor. Often the one and only deep sky attraction in Sculptor for many observers is the oblique spiral galaxy NGC 253, aka the Sculptor Galaxy. NGC 288 is located 1.8° southeast of the Sculptor Galaxy. In a 3° field of view NGC 288 rises from obscurity and shares the spotlight with NGC 253. Stephen O’Meara in Deep-Sky Companions: Hidden Treasures opines that “Few sights in the sky are as rewarding as seeing this dramatic pairing of deep-sky splendors.”
1908
At a declination of -26° NGC 288 may seem to be off limits to observers in the mid and northern latitudes – however it is not. In fact, this cluster was discovered from a rather northerly latitude of 51° by William Herschel in October 1785. Although NGC 288 culminates at the meridian in mid-October, early sunsets in the Winter provide an ample window of opportunity to observe at dusk, at least for a few more weeks. An absolute key to a successful observation is access to an unobstructed southern horizon.
William Herschel’s discovery notes for the cluster he logged as H VI-20 describe it as “Considerably bright, irregularly round, 8’ or 9’ in diameter. A great many of the stars are visible so there can remain no doubt that it is a cluster of very small stars.”
Unfortunately I have yet to log an observation of NGC 288, so instead I must rely on the DSF membership to share their observations and sketches, as they regularly do. Meanwhile I’ll share a few observational characteristics I garnered from The Night Sky Observer’s Guide, Volume 1 by George Kepple and Glen Sanner.
[the cluster] is partially enclosed by a semicircular star chain open on the SW side
the large dense core is embedded in a much less concentrated halo 7’ in diameter and irregular in outline
outlying members spread noticeably further to the south and SW
the loosely-structured Class X globular has a 9’ diameter but a star-poor halo around a dense 3’ diameter core
the globular’s periphery is irregular in profile
1909
Hubble ACS image
What makes NGC 288 such an unusual globular cluster?
the cluster travels in an oddball retrograde orbit
it is a loose halo cluster whose members each contain, on average, anywhere from 1/13 to 1/20 as much iron as the Sun
based on the large number of massive bright blue stars that have left the red giant phase and are being powered by helium fusion (on the so-called Horizontal Branch) – the age of NGC 288 has been calculated to be 13 to 14 billion years old, which places it among the very oldest globular clusters
1910
Now it’s your turn….don’t forget to share your observations and sketches of this incredible globular cluster.
As always,
"Give it a go and let us know!
Good luck and great viewing!"
NGC 288, Cl Melotte 3, GCl 2, Bennett 5
Constellation: Sculptor
Type: Globular Cluster, Class X
RA: 00h 52m 45s
Dec: -26° 34’ 57”
Distance: 37,000 ly
Size: 13.0’
Mag: 8.1
This week’s OOTW is the unusual and obscure globular cluster, NGC 288.
19071906
Although it is moderately bright and large, it is located in a constellation relatively unknown to many Northern Hemisphere observers – Sculptor. Often the one and only deep sky attraction in Sculptor for many observers is the oblique spiral galaxy NGC 253, aka the Sculptor Galaxy. NGC 288 is located 1.8° southeast of the Sculptor Galaxy. In a 3° field of view NGC 288 rises from obscurity and shares the spotlight with NGC 253. Stephen O’Meara in Deep-Sky Companions: Hidden Treasures opines that “Few sights in the sky are as rewarding as seeing this dramatic pairing of deep-sky splendors.”
1908
At a declination of -26° NGC 288 may seem to be off limits to observers in the mid and northern latitudes – however it is not. In fact, this cluster was discovered from a rather northerly latitude of 51° by William Herschel in October 1785. Although NGC 288 culminates at the meridian in mid-October, early sunsets in the Winter provide an ample window of opportunity to observe at dusk, at least for a few more weeks. An absolute key to a successful observation is access to an unobstructed southern horizon.
William Herschel’s discovery notes for the cluster he logged as H VI-20 describe it as “Considerably bright, irregularly round, 8’ or 9’ in diameter. A great many of the stars are visible so there can remain no doubt that it is a cluster of very small stars.”
Unfortunately I have yet to log an observation of NGC 288, so instead I must rely on the DSF membership to share their observations and sketches, as they regularly do. Meanwhile I’ll share a few observational characteristics I garnered from The Night Sky Observer’s Guide, Volume 1 by George Kepple and Glen Sanner.
[the cluster] is partially enclosed by a semicircular star chain open on the SW side
the large dense core is embedded in a much less concentrated halo 7’ in diameter and irregular in outline
outlying members spread noticeably further to the south and SW
the loosely-structured Class X globular has a 9’ diameter but a star-poor halo around a dense 3’ diameter core
the globular’s periphery is irregular in profile
1909
Hubble ACS image
What makes NGC 288 such an unusual globular cluster?
the cluster travels in an oddball retrograde orbit
it is a loose halo cluster whose members each contain, on average, anywhere from 1/13 to 1/20 as much iron as the Sun
based on the large number of massive bright blue stars that have left the red giant phase and are being powered by helium fusion (on the so-called Horizontal Branch) – the age of NGC 288 has been calculated to be 13 to 14 billion years old, which places it among the very oldest globular clusters
1910
Now it’s your turn….don’t forget to share your observations and sketches of this incredible globular cluster.
As always,
"Give it a go and let us know!
Good luck and great viewing!"