The Ohio State University College of Mathematical & Physical Sciences Department of Astronomy

Images of Gaseous Nebulae

The Orion Nebula (M42)

These pictures give different views of the nebula from the visible portion of the spectrum to the near infrared, all taken with state-of-the-art imaging spectrometer systems designed and built by the Imaging Sciences Laboratory of the OSU Astronomy Department.

(168Kb GIF)

Computer-enhanced 3-color image of the central core of the Orion Nebula composed from narrow-band images in three emission-line bands: Red=[SII]6716+31Å emission, Green=H-beta 4863Å emission, Blue=[OIII]5007Å Emission.

The colors are meant to show approximate spectral relations and ionization structure, and not an attempt to reconstruct true colors. [OIII] emission (twice-ionized Oxygen) fills only the hot central core of the nebula, Hydrogen emission (representing ioinzed Hydrogen) fills the entire main body of the nebula out to the sharp edge of the ionized zone, while [SII] emission arises in the outskirts of the ionized region (where the gas makes a relatively sharp transition from fully to partially ionized).

Most of the UV photons responsible for ionizing the nebula comes from the bright hot star at the bottom of the central "Trapezium" cluster seen near the middle of this image. The faint red stars are seen only in the reddest band as they are in the dusty regions behind the main ionized body of the nebula. Compare this view to the near-Infrared images below that cut through much of the dust in the Orion Molecular Cloud, showing a rich cluster of very young stars still embedded in the molecular gas cloud out of which they have formed.

The images were reconstructed from Fabry-Perot spectral data cubes obtained with the OSU Imaging Fabry-Perot Spectrometer on the 1.8-m Perkins Telescope, Anderson Mesa, Arizona

[Observing: Pogge; Reduction: Pogge & Owen; Composition: Pogge]

(144Kb GIF)

Near-Infrared K-band (2.2 micron) image of the same field as the emission-line image above, showing the greater number of stars visible in the near-IR. Most of these stars are embedded in the molecular cloud behind the ionized region we know as the Orion Nebula. This is one small part of a larger complex of star formation in the OMC1 complex.

False color has been applied to this image to enhance the faint nebula (a combination of H, He, and molecular H emission lines plus dust-scattered starlight). The coarser pixel scale of the OSIRIS camera is obvious.

The image above is part of a K-band mosaic of the OMC1/OMC2 region obtained with the Ohio State Infra-Red Imaging Spectrometer (OSIRIS), on the 1.8-m Perkins Telescope, Anderson Mesa, Arizona

[Observing: DePoy & Ali; Reduction: Ali; Composition: Pogge]

(87Kb GIF)

Side-by-Side Optical (left) and Near-IR (right) views of the central core of the Orion Nebula.

(216Kb GIF)

Narrowband (1% filter) Near-Infrared Molecular Hydrogen Image of the Orion Nebula. This filter isolates the v=1-0 S(1) vibrational-rotational transition emission line of molecular Hydrogen at 2.122um.

This image is composed of a 3x3 mosaic of 9 images, giving a full field-of-view of 12.8 arcminutes

(344Kb GIF)

Continuum-subtracted Molecular Hydrogen image of the Nebula core (4.6x9 arcminutes), derived from a subset of the above image and a similar mosaic of images obtained through another narrowband filter isolating a region of emission-line-free continuum (hence containing only starlight and scattered light).

This images shows the bright "Becklin-Neugebauer/Kleinman-Low" Region in the center, plus the filamentary "fingers" of emission that appear to be jets of material blowing away from this region where massive star(s?) have recently formed.

Images obtained with the Ohio State Infra-Red Imaging Spectrometer (OSIRIS), on the 1.5-meter Telescope, Cerro Tololo Interamerican Observatory, Chile

[IR Observing: DePoy; Reduction: DePoy & Pogge; Composition: Pogge]

(84Kb GIF)

Near-infrared color image of OMC2 IRs2 (Orion Molecular Cloud #2, Infrared Source #2), a star formation complex embedded deep in its molecular cloud and visible only an Infrared wavelengths. This image is a composite of 3 images taken through infrared J, H, and K filters (1.2, 1.6, and 2.2um, respectively).

Images were obtained on March 19, 1997 at the 4-meter Mayall telescope at the Kitt Peak National Observatory with MOSAIC, the MDM/Ohio State Aladdin Infrared Camera. This instrument employs a 512x1024 InSb array as detector, which is one of the largest IR detectors currently in operation.

[Observations: Martini, DePoy (OSU), Gatley, Joyce, & Hughes (NOAO), Reduction & Composition: Merrill & Gatley, NOAO]

The Ring Nebula (M57; NGC 6720)

(21Kb GIF) Also available as a 408Kb 24-bit TIFF

Ionization map of the Ring Nebula, the famous planetary nebula in Lyra (M57), composed of three emission-line images taken through narrowband filters isolating bright emission lines of neutral Oxygen, twice-ionized Oxygen, and twice-ionized Helium (Red=[OI]6300Å, Green=[OIII]5007Å, Blue=HeII 4686Å). These colors are meant to represent the ionization structure of the nebula, from partially ionized gas marking the outer edge of the inner shell (red [OI] emission), the ionized gas in the body of the ring (green [OIII] emission), and the very hot, highly ionized gas in a central bubble between the ring and the central star (blue HeII emission).

(61Kb GIF)

[OI]6300Å Emission-line image (Field of view: 4.2 arcminutes) of the Ring Nebula. This image makes up the red plane of the one above, and shows partially-ionized gas surrounding the outer edge of the main ring.

(204Kb GIF)

High-contrast version of the image above with an intensity "stretch" chosen so as to emphasize the large, faint, filametary halo that surrounds the central bright "Ring". This shows that the star ejected its envelope in stages, beginning with a strong stellar wind during its AGB phase (the faint, nearly circular halo that extends across this image), followed by a heavier mass-loss phase probably related to an unstable thermal pulse in the final red giant (scruffy shell outside the burned-out ring). The ring in the above images was the final stage of mass-loss when the rest of the envelope was shrugged off the stellar core, representing at least half the original mass of the star.

Data obtained with the OSU Imaging Fabry-Perot Spectrometer + TI 800x800 CCD, 1.8-meter Perkins Telescope, Anderson Mesa, AZ.

[Observers: Lame & Pogge; Reduction: Lame; Composition: Pogge]

Eagle Nebula (M16)

Monochromatic H-alpha and [N II] (singly-ionized nitrogen) emission-line image of the central regions of the Eagle Nebula (M16). These images show the gaseous pillars made famous by Jeff Hester's stunningly beautiful HST Images.

Images obtained through a 5nm wide interference filter centered at 656.3nm with the OSU Imaging Fabry-Perot Spectrometer + TI 800x800 CCD, 1.8-meter Perkins Telescope, Anderson Mesa, AZ

[Credit: Pogge]

Trifid Nebula (M20)

Monochromatic H-alpha and [N II] (singly-ionized nitrogen) emission-line image of the center of the Trifid Nebula (M20). Edge-brightened dust structures reminiscent of the bright edges of the M16 pillars are seen above and below to the left of the two star peeking out from a bay of dark obscuring dust crossing the bright portion of the nebula.

Images taken through a 5nm wide interference filter centered at 656.3nm with the OSU Imaging Fabry-Perot Spectrometer + TI 800x800 CCD, 1.8-meter Perkins Telescope, Anderson Mesa, AZ

[Credit: Pogge]

W3 Star Formation Complex

Near-Infrared color image of the heavily reddened star formation complex W3. Composed of JHK-band images coded as Blue, Green, and Red, respectively. Field of view is about 3-arcminutes on a side. The bright central source of W3, which is completely invisible at visual wavelengths due to heavy dust obscuration, is one of the brightest stars in the Galaxy.

Images were obtained with the OSU MOSAIC near-IR imager/spectrometer on 1996 Nov 20 with the NOAO 2.1-m telescope at the Kitt Peak National Observatory.

[Observers: DePoy & Martini (OSU), Gatley & Merrill (NOAO); Reduction & Composition: Merrill & Gatley]

NGC 2024 Star Formation Region

Near-Infrared color image of NGC 2024, an extremely dusty region of young star formation in the constellation of Orion. This image is composed of separate near-infrared images obtained in the J-, H-, and K-band filters (wavelengths of 1.2, 1.6, and 2.2 microns, respectively), and combined as blue, green, and red colors. Many stars appear red because they are deeply embedded in the thick dust cloud that appears to almost bisect the nebula at visual (and even near-IR) wavelengths. Dust strongly scatters and absorbs visible wavelengths, but at increasingly longer IR wavelengths, the obscuring effects of dust steadily decrease, and so IR instruments in a sense allows us to "see through" the dust to the stars embedded within.

Images obtained with the Ohio State Infrared Imager Spectrometer (OSIRIS), with a 256x256 NICMOS-3 IR Array, and 1.8-meter Perkins Telescope, Anderson Mesa, AZ

[Credit: Ali]

The Horsehead Nebula (IC434)

Pseudo-color emission-line image through a 5nm H-alpha interference filter centerd at 656.3nm. The Horsehead is a plume of dust rising in front of a background of glowing ionized gas off in one part of the Orion Molecular Cloud complex. The false colors code brightness as colors, and were chosen to make the bright background nebular reddish-orange, and the dark foreground dust feature black with blue edges (and besides, the monochromatic image rendered in black&white is not nearly as dramatic). A rare instance when false color is useful.

Images obtained with the OSU Imaging Fabry-Perot Spectrometer + TI 800x800 CCD, 1.8-meter Perkins Telescope, Anderson Mesa, AZ

[Credit: Pogge]