Full Infrared View of the M81 Galaxy

Spitzer_ssc2019-15b_1024

spitzer_ssc2019-15b August 27th, 2019

Credit: NASA/JPL-Caltech

The magnificent spiral arms of the nearby galaxy Messier 81 are highlighted in this image from NASA's Spitzer Space Telescope. Located in the northern constellation of Ursa Major (which also includes the Big Dipper), this galaxy is easily visible through binoculars or a small telescope. M81 is located at a distance of 12 million light-years.

M81 was one of the first publicly-released datasets soon after Spitzers launch in August of 2003. On the occasion of Spitzers 16th anniversary this new image revisits this iconic object with extended observations and improved processing.

This Spitzer infrared image is a composite mosaic combining data from the Infrared Array Camera (IRAC) at wavelengths of 3.6/4.5 microns (blue/cyan) and 8 microns (green) with data from the Multiband Imaging Photometer (MIPS) at 24 microns (red).

The 3.6-micron near-infrared data (blue) traces the distribution of stars, although the Spitzer image is virtually unaffected by obscuring dust and reveals a very smooth stellar mass distribution, with the spiral arms relatively subdued.

As one moves to longer wavelengths, the spiral arms become the dominant feature of the galaxy. The 8-micron emission (green) is dominated by infrared light radiated by hot dust that has been heated by nearby luminous stars. Dust in the galaxy is bathed by ultraviolet and visible light from nearby stars. Upon absorbing an ultraviolet or visible-light photon, a dust grain is heated and re-emits the energy at longer infrared wavelengths. The dust particles are composed of silicates (chemically similar to beach sand), carbonaceous grains and polycyclic aromatic hydrocarbons and trace the gas distribution in the galaxy. The well-mixed gas (which is best detected at radio wavelengths) and dust provide a reservoir of raw materials for future star formation.

The 24-micron MIPS data (red) shows emission from warm dust heated by the most luminous young stars. The scattering of compact red spots along the spiral arms show where the dust is warmed to high temperatures near massive stars that are being born in giant H II (ionized hydrogen) regions.

Provider: Spitzer Space Telescope

Image Source: http://www.spitzer.caltech.edu/images/6675-ssc2019-15b-Full-Infrared-View-of-the-M81-Galaxy

Curator: Spitzer Space Telescope, Pasadena, CA, USA

Image Details

Image Type
Observation
Object Name
M81 Messier 81 NGC 3031 Bode's Galaxy UGC 5318
Subject - Local Universe
Galaxy > Type > Spiral

Distance

Universescale2
8,500,000 light years
Spitzer_ssc2019-15b_128
 

Position Details

Position (ICRS)
RA = 9h 55m 33.0s
DEC = 69° 3’ 52.7”
Orientation
North is 30.0° CW
Field of View
24.0 x 24.0 arcminutes
Constellation
Ursa Major

Color Mapping

  Telescope Spectral Band Wavelength
Blue Spitzer (IRAC) Infrared (Near-IR) 3.6 µm
Cyan Spitzer (IRAC) Infrared (Near-IR) 4.5 µm
Green Spitzer (IRAC) Infrared (Mid-IR) 8.0 µm
Red Spitzer (MIPS) Infrared (Mid-IR) 24.0 µm
Spectrum_ir1
Blue
Cyan
Green
Red
Spitzer_ssc2019-15b_1280
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ID
ssc2019-15b
Subject Category
C.5.1.1  
Subject Name
M81, Messier 81, NGC 3031, Bode's Galaxy, UGC 5318
Credits
NASA/JPL-Caltech
Release Date
2019-08-27
Lightyears
8,500,000
Redshift
0.000113
Reference Url
http://www.spitzer.caltech.edu/images/6675-ssc2019-15b-Full-Infrared-View-of-the-M81-Galaxy
Type
Observation
Image Quality
Good
Distance Notes
Facility
Spitzer, Spitzer, Spitzer, Spitzer
Instrument
IRAC, IRAC, IRAC, MIPS
Color Assignment
Blue, Cyan, Green, Red
Band
Infrared, Infrared, Infrared, Infrared
Bandpass
Near-IR, Near-IR, Mid-IR, Mid-IR
Central Wavelength
3600, 4500, 8000, 24000
Start Time
Integration Time
Dataset ID
Notes
Coordinate Frame
ICRS
Equinox
J2000
Reference Value
148.8873235, 69.0646392
Reference Dimension
3840.0, 3840.0
Reference Pixel
1921.0, 1921.0
Scale
-0.000104156, 0.00010415599
Rotation
-30.02
Coordinate System Projection:
TAN
Quality
Full
FITS Header
Notes
WCS retrieved using CXCs PinpointWCS
Creator (Curator)
Spitzer Space Telescope
URL
http://www.spitzer.caltech.edu
Name
Email
Telephone
Address
1200 E. California Blvd.
City
Pasadena
State/Province
CA
Postal Code
91125
Country
USA
Rights
Publisher
Spitzer Science Center
Publisher ID
spitzer
Resource ID
ssc2019-15b.tif
Metadata Date
2019-08-27
Metadata Version
1.1
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Detailed color mapping information coming soon...

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Universescalefull
8,500,000 light years

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