Milky Way from Taurus to Perseus

On this page a 25°×35° wide-field view of the 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.

The 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 the second section. The third section contains a presentation of some discoveries. Image and instrument data can be found at the end of this page.

Full views

Click on the images to load a full resolution version with up to more than 100 megapixels using a JavaScript viewer.

Milky Way from Taurus to Perseus in H-alpha, blue continuum and red continuum
This image is a false color composite where H-alpha (including red continuum) is mapped to red, blue continuum (including [OIII] and H-beta emissions) is mapped to green and red continuum (without H-alpha) is mapped to blue, i.e. HII regions appear reddish and reflection nebulae appear blue to green. Stars are partially subtracted in order to make the faint nebulae visible.

Milky Way from Taurus to Perseus in H-alpha
Legend for false color image of Milky Way from Taurus to Perseus in H-alpha
 
This visualization is a pseudo 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.
 
Color composition: 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). Blue regions least compressed while white regions are most compressed. The luminance is determined by the tonal curve corrected result of the dynamic range compression.

Milky Way from Taurus to Perseus region in RGB
An almost-true color image. Unlike to the other images the stars are not subtracted. This improves the visibility of dark nebulae that absorb the light from the stars behind.
 
Due to limited resolution in continuum channels the image is only presented at half resolution.

Selected details

Here are a few details that also can be seen using the JavaScript viewer.
Taurus Molecular Cloud and Pleiades
The greenish star cluster at the bottom are the Pleiades (M45, greenish here because blue continuum is mapped to green). Distance is about 130pc (430 light-years). The dust which scatters the light from the stars lies about 0.3pc to 0.7pc (1 to 2 light-years) 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 130pc to 200pc (420 to 650 light-years), see [2]. Thus, Pleiades nebula and and Taurus Molecular Cloud may be associated.
California Nebula behind molecular clouds
The reflection nebulae (blue to green) in top left quarter belong to Taurus Molecular Cloud. The dense structure (partly as dark nebula) in bottom left quarter belong to Perseus Molecular cloud which extends within a distance of about 280pc to 320pc (910 ly to 1040 light years, see [3]. Further molecular clouds that are visible in that image where measured in [4].

The molecular clouds partly obscure a large HII region (red) which brightest part is the California nebula (NGC 1499). That region is analyzed in detail in next section.

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).

Discoveries

The views above show many nebulae that cannot be found in catalogs. (The JavaScript Viewer allows to identify objects using catalogs or SIMBAD and to define new objects.) Some (probably not all) of these unexplored nebulae have been collected in the list below. Click on the following links for a presentation. Notes:

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: 4h36', DEC: 32°
Orientation: North right (exactly)
Scale: 10 arcsec/pixel (in center at maximum resolution)
FOV: 35°×25° (RA×DEC, through center)
Exposure times: Sum of exposure times of all frames used to calculate the image.
H-alpha: 7.4 d
Continuum channels: 5.8 d

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. Bias correction, dark current subtraction, flatfield correction
  2. Alignment and brightness calibration using stars from reference image
  3. Stacking with masking unlikely values and background correction
  4. Star subtraction
  5. Denoising and deconvolution both components (stars and residual)
  6. RGB-composition (same factor for stars and residual for the true color composite)
  7. Dynamic range compression using non-linear high-pass filter
  8. 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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