Euclid’s view of globular cluster NGC 6397

Ensci_euclid20231107d_1024

ensci_euclid20231107d October 31st, 2023

Credit: ESA/Euclid/Euclid Consortium/NASA

This sparkly image shows Euclid’s view on a globular cluster called NGC 6397. Globular clusters are collections of hundreds of thousands of stars held together by gravity.

Located about 7800 light-years from Earth, NGC 6397 is the second-closest globular cluster to us. Together with other globular clusters it orbits in the disk of the Milky Way, where the majority of stars are located.

Globular clusters are some of the oldest objects in the Universe. That’s why they contain a lot of clues about the history and evolution of their host galaxies, like this one for the Milky Way.

The challenge is that it is typically difficult to observe an entire globular cluster in just one sitting. Their centers contain lots of stars, so many that the brightest ‘drown out’ the fainter ones. Their outer regions extend a long way out and contain mostly low-mass, faint stars. It is the faint stars that can tell us about previous interactions with the Milky Way.

Technical details: The data in this image were taken in just about one hour of observation. This color image was obtained by combining VIS data and NISP photometry in Y and H bands; its size is 8800 x 8800 pixels. VIS and NISP enable observing astronomical sources in four different wavelength ranges. Aesthetics choices led to the selection of three out of these four bands to be cast onto the traditional Red-Green-Blue color channels used to represent images on our digital screens (RGB).

The blue, green, red channels capture the Universe seen by Euclid around the wavelength 0.7, 1.1, and 1.7 micron respectively. This gives Euclid a distinctive color palette: hot stars have a white-blue hue, excited hydrogen gas appears in the blue channel, and regions rich in dust and molecular gas have a clear red hue. Distant redshifted background galaxies appear very red.

In the image, the stars have six prominent spikes due to how light interacts with the optical system of the telescope in the process of diffraction. Another signature of Euclid special optics is the presence of a few, very faint and small round regions of a fuzzy blue color. These are normal artifacts of complex optical systems, so-called ‘optical ghost’; easily identifiable during data analysis, they do not cause any problem for the science goals.

ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi, CC BY-SA 3.0 IGO

Provider: Euclid

Image Source: https://euclid.caltech.edu/image/euclid20231107d-euclid-s-view-of-globular-cluster-ngc-6397

Curator: Euclid-ESA

Image Use Policy: http://www.esa.int/spaceinvideos/Terms_and_Conditions

Image Details

Image Type
Observation
Object Name
NGC 6397
Subject - Milky Way
Star > Grouping > Cluster > Globular

Distance

Universescale1
7,800 light years
Ensci_euclid20231107d_128
 

Position Details

Position (ICRS)
RA = 17h 40m 42.0s
DEC = -53° 40’ 28.8”
Orientation
North is 2.2° CCW
Field of View
41.0 x 41.0 arcminutes
Constellation
Ara

Color Mapping

  Telescope Spectral Band Wavelength
Blue Euclid (VIS) Optical 700.0 nm
Green Euclid (NISP) Infrared 1.1 µm
Red Euclid (NISP) Infrared 1.7 µm
Spectrum_base
Blue
Green
Red
Ensci_euclid20231107d_1280
×
ID
euclid20231107d
Subject Category
B.3.6.4.2.  
Subject Name
NGC 6397
Credits
ESA/Euclid/Euclid Consortium/NASA
Release Date
2023-10-31
Lightyears
7,800
Redshift
7,800
Reference Url
https://euclid.caltech.edu/image/euclid20231107d-euclid-s-view-of-globular-cluster-ngc-6397
Type
Observation
Image Quality
Good
Distance Notes
Facility
Euclid, Euclid, Euclid
Instrument
VIS, NISP, NISP
Color Assignment
Blue, Green, Red
Band
Optical, Infrared, Infrared
Bandpass
Central Wavelength
700, 1100, 1700
Start Time
Integration Time
Dataset ID
Notes
Coordinate Frame
ICRS
Equinox
Reference Value
265.17506851131242, -53.674659866005889
Reference Dimension
3000, 3000
Reference Pixel
1500, 1500
Scale
-0.00022785, 0.00022785
Rotation
2.18
Coordinate System Projection:
TAN
Quality
Full
FITS Header
Notes
Creator (Curator)
Euclid-ESA
URL
https://www.esa.int/Science_Exploration/Space_Science/Euclid
Name
Email
Telephone
Address
City
State/Province
Publisher
Euclid NASA Science Center at IPAC (ENSCI)
Publisher ID
ensci
Resource ID
Metadata Date
2023-11-21T19:51:31Z
Metadata Version
1.2
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Detailed color mapping information coming soon...

×
Universescalefull
7,800 light years

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