Milky Way from Taurus to Perseus

On this page a 25°×35° wide-field view of Milky Way in the constellations Taurus, Auriga and Perseus is presented in different color composites. The region south of the galactic plane is full of Molecular clouds.

All pictures below are downscaled versions. Full resolution images with more than 100 megapixels can be loaded with a Javascript viewer by clicking on the images in the first section. Selected details are shown in a second section Image and instrument data can be found at the end of this page.

There are short descriptions below each image.

Full views

Click on the images to load a full resolution version with up to more than 100 megapixels using a JavaScript viewer. If browser cannot handle this or in case of low bandwidth connections you can try the lower resolution versions. The links can be found below the images.

Some browsers (namely Gecko based ones like Firefox) cannot downscale properly with Javascript, they just downsample. This results in noisy images and randomly appearing and disappearing stars while zooming. If such artifacts appear you can try the direct download version and use the browsers built-in viewer. Download links can be found below the images.

Direct download is also recommended for mobile devices (and devices with touchscreen) because browsers for these devises usually have a integrated viewer which is faster than the Javascript viewer and can handle larger data.

Milky Way from Taurus to Perseus in H-alpha (red), blue continuum (green) and red continuum (blue)
Full resolution (41 MB): Javascript Viewer Direct download
Half resolution (11 MB): Javascript Viewer Direct download
One third resolution (4.4 MB): Javascript Viewer Direct download
 
This visualization is a false color image where H-alpha (including red continuum) is mapped to red, blue continuum is mapped to green and red continuum (without H-alpha) is mapped to blue. Reflection nebulae appear green to blue. Emission nebulae appear red.
 
Stars are partially subtracted. Further image processing steps are dynamic range compression using a nonlinear hi-pass filter and tonal curve correction.

Milky Way from Taurus to Perseus in H-alpha (false color)
Legend for false color image of Milky Way from Taurus to Perseus in H-alpha
 
Full resolution (55 MB): Javascript Viewer Direct download
Half resolution (12 MB): Javascript Viewer Direct download
One third resolution (4.7 MB): Javascript Viewer Direct download
 
This visualization is a false color image which only uses the H-alpha data (including some red continuum). It shows much more details of the emission nebulae than the image above.
 
After partial star subtraction the dynamic range was compressed using a non-linear hi-pass filter. That leads to a compression ratio r which is used to calculate the color as depicted in the legend. (The legend shows the compression c:=1-r). The luminance is determined by the tonal curve corrected result of the dynamic range compression.

Milky Way from Taurus to Perseus  region in RGB
Half resolution (13 MB): Javascript Viewer Direct download
 
This image comes close to a true color view. Red component shows red continuum including some (but reduced) H-alpha, green continuum is mapped to green and blue continuum is mapped to blue.
 
Unlike to the other images the stars are not subtracted. This makes the dark nebulae visible which cover the light from the stars behind.
 
Due to limited resolution in continuum channels the image is only presented at half resolution.

All image processing steps are deterministic, i.e. there is no manual retouching or any kind of non-reproducible adjustment.

Selected details

Here are a few details that also can be seen using the Javascript viewers (if browser works correctly).
Taurus Molecular Cloud and Pleiades
The greenish star cluster at the bottom are the Pleiades (M45). Distance is about 430 ly (Light-years). The dust which scatters the light from the stars lies about 1 to 2 ly in front of the stars, see [1]. Most of the other reflection nebulae (greenish to blue) belongs to the Taurus Molecular Cloud (the picture covers most of it) which extends within a distance of about 420 ly to 645 ly, see [2]. Thus, Pleiades nebula and and Taurus Molecular Cloud may be associated.
California Nebula behind molecular clouds
The reflection nebulae in top left quarter belong to Taurus Molecular Cloud. The reflection nebulae in bottom left quarter belong to Perseus Molecular cloud which extends within a distance of about 956 ly to 1047 ly, see [3]. According to [4] the reflection nebulae in the right third belong to another molecular cloud. The HII region (red) which contains the california nebula (NGC 1499, bright red) obviously lies behind the molecular clouds. Distance is not known exactly, but distance of th ionizing star ξ Persei is about 1350 ly (± 150 ly).
Spaghetti Nebula (SH2-240, Simeis 147, supernova Remnant) in false colors made from H-Alpha
The Spaghetti Nebula (SH2-240, Simeis 147) is a supernova remnant.
IC 504 and IC 410 in false colors made from H-alpha
HII region containing IC 405 (Flaming Star Nebula, Sh2-229, the lower bright area in the bottom left quarter) and IC 410 (SH2-236, the upper bright area in the bottom left quarter).

Image data

Images where captured with a camera array which is described on the instruments page.

Image data are:

Projection type: Stereographic
Center position: RA: 4h40, DEC: 33°
Orientation: North right (exactly)
Scale: 10 arcsec/pixel (in center at maximum resolution)
FOV: 25°×35° (through center)
Exposure times: H-alpha: 7.0d, continuum channels: 4.1d (sum of exposure times of all frames used to calculate the image)

Image processing

All image processing steps are deterministic, i.e. there was no manual retouching or any other kind of non-reproducible adjustment. The software which was used can be downloaded here.

Image processing steps where:

  1. H-alpha only: bias correction, photon counting
  2. Dark current subtraction, flatfield correction, noise estimation
  3. Alignment and brightness calibration using stars from PPMXL catalog
  4. Stacking with masking unlikely values and background correction
  5. Extracting stars
  6. Denoising and deconvolution both components (stars and residual)
  7. RGB-composition (same factor for stars and residual for the true color composite)
  8. Dynamic range compression using non-linear high-pass filter
  9. Tonal curve correction

References

  1. Gibson, S.J.; Nordsieck, K.H. (2003). "The Pleiades Reflection Nebula. II. Simple Model Constraints on Dust Properties and Scattering Geometry". The Astrophysical Journal. 589 (1): 362–377.
  2. P. A. B. Galli 1, L. Loinard 2,3 H. Bouy 1, L. M. Sarro 4, G. N. Ortiz-León 5, S. A. Dzib 5, J. Olivares 1, M. Heyer 6, J. Hernandez 7, C. Román-Zúñiga 7, M. Kounkel 8, and K. Covey, (2019). "Structure and kinematics of the Taurus star-forming region from Gaia-DR2 and VLBI astrometry". Astronomy & Astrophysics 630: A137.
  3. Gisela N. Ortiz-León et al. (2018.) "The Gould's Belt Distances Survey (GOBELINS). V. Distances and Kinematics of the Perseus Molecular Cloud." The Astrophysical Journal, 865 (1): 73
  4. Ungerechts, H. & Thaddeus, P. (1987). "A CO survey of the dark nebulae in Perseus, Taurus, and Auriga". Astrophysical Journal Supplement Series, 63: 645-660.

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