NGC 7331

Caldwell 30.jpg
Autor/Urheber: NASA Hubble, Lizenz: CC BY 2.0
The majestic spiral galaxy Caldwell 30, also cataloged as NGC 7331, is often touted as an analog to our own Milky Way, as its size, shape and mass are similar to our galaxy’s. Caldwell 30’s starry disk is inclined to our line of sight, so long telescopic exposures often result in images that evoke a strong sense of depth. In this Hubble close-up, taken in visible and ultraviolet light using the Wide Field Camera 3, the galaxy’s magnificent spiral arms feature dark, obscuring dust lanes, bright bluish clusters of massive young stars and the telltale reddish glow of active star-forming regions. The bright, yellowish central regions harbor populations of older, cooler stars. As in the Milky Way, a supermassive black hole lies at the core of this near-twin galaxy.

Hubble took this image of Caldwell 30 while studying a supernova explosion, which is the fiery death of a massive star. This supernova, called SN 2014C, experienced an unusual and dramatic transformation that involved a significant upsurge in hydrogen content. Hubble’s observations provided a chance to gain insight into the final stages of massive stars.

Caldwell 30 is located about 45 million light-years away at the northern boundary of the constellation Pegasus. The galaxy is only about half a degree away from a group of five galaxies known as Stephan’s Quintet. Caldwell 30 and the quintet may appear to be near each other in the sky, but the quintet is actually about six times farther away from Earth.

Caldwell 30 was discovered in 1784 by famed astronomer William Herschel, who also discovered the planet Uranus as well as many other Caldwell objects. Late autumn skies will provide the best view from the Northern Hemisphere (or spring skies in the Southern Hemisphere). However, with a magnitude of 9.5, Caldwell 30 will require a telescope or large binoculars to see it for yourself. In light-polluted skies, only the central core of the galaxy is visible. Under dark skies, a large telescope will also reveal the galaxy’s sweeping spiral arms.

For more information about Hubble’s observations of Caldwell 30, see:

www.spacetelescope.org/images/potw1805a/

For Hubble's Caldwell catalog site and information on how to find these objects in the night sky, visit:

www.nasa.gov/content/goddard/hubble-s-caldwell-catalog

N7331s.jpg
Autor/Urheber: Credit Line and Copyright Adam Block/Mount Lemmon SkyCenter/University of Arizona, Lizenz: CC BY-SA 3.0 us
NGC 7331

Picture Details:

   Optics            24-inch RC Optical Systems Telescope
   Camera            SBIG STL11000 CCD Camera
   Filters           Custom Scientific
   Dates             September 10th-13th 2009
   Location          Mount Lemmon SkyCenter
   Exposure          LRGB = 180:100:90:100 minutes
   Acquisition       ACP Observatory Control Software (DC-3 Dreams),TheSky (Software Bisque), Maxim DL/CCD (Cyanogen)
   Processing        CCDStack (CCDWare), Mira (MiraMetrics), Maxim DL (Cyanogen), Photoshop CS3 (Adobe)
   Guest Astronomers:                   September 2009 Image Processing Workshop Participants

Credit Line and Copyright Adam Block/Mount Lemmon SkyCenter/University of Arizona

NGC 7331 GALEX WIKISKY.png
UV-Image of NGC 7331 made by GALEX

The Milky Way’s Unusual Twin in Pegasus (iotw2451a).jpg
Autor/Urheber: International Gemini Observatory/NOIRLab/NSF/AURA Image Processing: J. Miller (International Gemini Observatory/NSF NOIRLab), M. Rodriguez (International Gemini Observatory/NSF NOIRLab) & M. Zamani (NSF NOIRLab), Lizenz: CC BY 4.0
The magnificent spiral galaxy NGC 7331, located approximately 40 million light-years away in the constellation Pegasus, is the brightest and closest galaxy in the visual galaxy group that bears its name, the NGC 7331 Group. Revealed in the details of this image are populations of hot stars and dark dust lanes winding throughout the spiral arms. Also known as Caldwell 30, this galaxy is often thought of as a twin to the Milky Way owing to its similar size and spiral structure. However, there are a couple of features of its core that set it apart from our home galaxy. For instance, astronomers have found evidence that the Milky Way has a central bar of stars and dust cutting through its center, a feature common to many spiral galaxies. But NGC 7331 lacks this feature. Additionally, NGC 7331’s central bulge rotates in the opposite direction to its galactic disk — unusual behavior compared to other galaxies and different from what we observe in the Milky Way.This image was taken by Gemini North, one half of the International Gemini Observatory, supported in part by the U.S. National Science Foundation and operated by NSF NOIRLab. You can find other views of NGC 7331 captured at Kitt Peak National Observatory, a Program of NSF NOIRLab, in 2014 and 1975 in the NOIRLab Image archive.

Caldwell Catalogue.jpg
Autor/Urheber: Roberto Mura, Lizenz: CC BY-SA 3.0
Caldwell Catalogue objects.

NGC 7331 Ssc2004-12a1.png
Spitzer Composite View of NGC 7331

This composite infrared image from NASA's Spitzer Space Telescope has captured a nearby spiral galaxy that resembles our own Milky Way. The galaxy, known as NGC 7331 and sometimes referred to as our galaxy's twin, is found in the constellation Pegasus at a distance of 50 million light-years. This inclined galaxy was discovered in 1784 by William Herschel, who also discovered infrared light.

The evolution of this galaxy is a story that depends significantly on the amount and distribution of gas and dust, the locations and rates of star formation, and on how the energy from star formation is recycled by the local environment. The new Spitzer images are allowing astronomers to "read" this story by dissecting the galaxy into its separate components.

The image, measuring 12.6 by 8.2 arcminutes, was obtained by Spitzer's infrared array camera. It is a four-color composite of invisible light, showing emissions from wavelengths of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (yellow) and 8.0 microns (red). These wavelengths are roughly 10 times longer than those seen by the human eye.

The infrared light seen in this image originates from two very different sources. At shorter wavelengths (3.6 to 4.5 microns - shown as blue), the light comes mainly from stars, particularly ones that are older and cooler than our Sun. This starlight fades at longer wavelengths (5.8 to 8.0 microns - shown as red), where instead we see the glow from clouds of interstellar dust. This dust consists mainly of a variety of carbon-based organic molecules known collectively as polycyclic aromatic hydrocarbons. Wherever these compounds are found, there will also be dust granules and gas, which provide a reservoir of raw materials for future star formation.

Perhaps the most intriguing feature seen at longer-wavelength is a ring of dust girdling the galaxy center. This ring, with a radius of nearly 20,000 light-years, is invisible at shorter wavelengths, yet has been detected at sub-millimeter and radio wavelengths. It is made up in large part of polycyclic aromatic hydrocarbons. Spitzer measurements suggest that the ring contains enough gas to produce four billion stars like the Sun. Starlight was systematically subtracted from the longer-wavelength picture to enhance dust features.

Three other galaxies are seen below NGC 7331, all about 10 times farther away. From left to right are NGC 7336, NGC 7335 and NGC 7337. The blue dots scattered throughout the image are foreground stars in the Milky Way; the red ones are galaxies that are even more distant.

The Spitzer observations of NGC 7311 are part of a large 500-hour science project, known as the Spitzer Infrared Nearby Galaxy Survey, which will comprehensively study 75 nearby galaxies with infrared imaging and spectroscopy.