Planetary Nebulae
Planetary nebulae result from the final stage of evolution of stars with masses less than about 8 solar masses. This means most stars will end their lives by producing planetary nebulae. As one of these stars burns all its thermonuclear fuel it expands as a red giant with a strong stellar wind. These winds blow off the outer shell of gas and the star collapses into a very hot white dwarf. The radiation from the white dwarf ionizes the expanding gas shell creating an emission nebula called a planetary nebula. The appellation "planetary" was given to such objects by William Hershel in the 1780's, when he first observed them and thought they resembled planets.
CLICK ON A THUMBNAIL TO VIEW THE IMAGE AT HIGHER RESOLUTION
Medusa Nebula - Also designated Abell 21 this emission nebula, about 1500 light-years away in the constellation, Gemini, was discovered by George O. Abell in 1955. Until 1970 it was classified as a supernova remnant, but a Soviet study found it to be a planetary nebula. In addition to the bright hydrogen (H-alpha) emission from the crescent and the faint blue oxygen (OIII) emission intermingled with it, there is quite a lot of very faint emission visible around this nebula.
Telescope: Meade 14" LX200GPS @ f/7 with Starizona SCT corrector Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 12 X 30 minutes = 6 hrs |
The Helix Nebula (NGC 7293) - This bright nebula is only 700 light-years from earth in the constellation, Aquarius. It was formed when a star similar to our sun reached the end of its life, collapsed, and ejected its outer layers into space. The remainder of the star is visible at the center of the nebula and is destined to become a white dwarf. The red glow is hydrogen emission and the blue glow is oxygen emission.
Telescope: Meade 14" LX200GPS @ f/2 with Hyperstar 3 Camera: SBIG ST-8300C Autoguiding: Orion ST-80 with Meade DSI using PHD Exposure: 49 X 5 minutes = 4 hr 5 min. |
Messier 27 - Also called the Dumbell Nebula, this planetary nebula in Vulpecula was the first such nebula to be discovered by Charles Messier in 1764. It is about 1400 light-years away.
Telescope: Meade 8" LX200R @ f/7 with an Astro-Physics 0.67X telecompressor Camera: SBIG ST-8300C Autoguiding: Orion ST-80 with Meade DSI using PHD Exposure: 12 X 15 minutes = 4 hrs |
Messier 57 - This striking planetary nebula in the constellation, Lyra, only 2300 light-years from earth, is easily visible in small telescopes. It was discovered in 1779 by Antione Darquier de Pellepoix. In 1864 English amateur astronomer, William Huggins, took spectra of M57 and other similar nebulae and found that they were glowing gases, not unresolvable stars as had been previously thought. The red outer ring is mostly hydrogen with some ionized nitrogen and the blue inner region is doubly ionized oxygen. The blue central star, from which the gases in the ring were expelled, is magnitude 14.8. The outer diameter of the ring in 230 arcsec and it is expanding at a rate of about 1 arcsec per century.
The barred spiral galaxy, IC 1296, is visible in the upper right corner of the image. This galaxy is 221 million light-years away. In August of 2013, a supernova, designated SN 2013ev, was discovered in IC1296. Telescope: Meade 8" LX200R @ f/7 with an Astro-Physics 0.67X telecompressor Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 12 X 15 minutes = 3 hrs |
The Red Rectangle Nebula (HD 44179) - So called because of how it looks visually, this is a proto-planetary nebula surrounding a binary star in Monoceros about 2300 light-years away. It is small (24 X 40 arc-sec) and puzzling. Neither the shape nor the red color have been fully explained. A discussion of it can be found here - http://www.esa.int/Our_Activities/Space_Science/The_remarkable_Red_Rectangle_A_Stairway_to_Heaven . It is a somewhat difficult object to image, because the central binary star is very bright (mag = 9). I decided to try 5 minute sub-exposures, instead of my normal 30 minutes. It seems to work, though the central star is still dominant.
Telescope: Meade 14" LX200GPS @ f/6.8 Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 24 X 5 minutes = 2 hrs |
Siimeis 22 (Sharpless 2-188) - This is an unusual planetary nebula about 850 light-years away in Cassiopeia. The progenitor star is moving very fast to the southeast causing the expelled outer layers to be compressed and heated in that direction by the interstellar medium. The faint nebulosity on the northwest side reveals the overall structure to be roughly spherical.
Simeis 22 was originally discovered in 1951 and classified as an emission nebula. It was later included by Stewart Sharpless in his catalog. However, in the 1990’s spectroscopic studies showed it to be a planetary nebula. In 2005 Wareing, et al (http://arxiv.org/abs/astro-ph/0506064) used a computer model to propose that the bright, filamentary feature is a shock front caused by the expanding gas shell from the progenitor star interacting with the interstellar medium (ISM). Their model estimated that the progenitor star was moving through the ISM at 125 km/sec. In the attached image I have indicated the position and direction of motion of the progenitor star and have identified several faint background galaxies. There is one background galaxy near the top of the nebula that I have not been able to identify. I guess it is possible that it is not a galaxy, but it sure looks like one. Telescope: Meade 14" LX200GPS @ f/7 with Starizona SCT corrector Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 12 X 30 minutes = 6hrs |
NGC 7354 - About 4200 light-years away in Cepheus, this planetary nebula has two gas shells, an outer spherical one and an inner elliptical one. The knots and jets, more apparent in the Hubble image than in mine, may indicate that there are two stars at the center, but the second one has not been found. NGC 7354 is about 18 arc-sec in diameter.
Telescope: Meade 14" LX200GPS @ f/6.8 Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 8 X 30 minutes = 4 hrs |
NGC 7662 - Also known at the Blue Snowball Nebula, this very small planetary nebula in the constellation, Andromeda, is a favorite of visual observers. Its blue color is revealed in telescopes of 6” aperture and larger. Distance estimates place it between 1750 and 5600 light-years away. The temperature of the dead central star is estimated to be about 75,000 K or about 15 times the temperature of our sun.
Telescope: Meade 8" LX200R @ f/7 with an Astro-Physics 0.67X telecompressor Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 48 X 5 minutes = 4 hrs |
NGC 6537 - This very small (~1 arcmin) planetary nebula in Sagittarius is called The Red Spider. At a declination of -20° it only gets up to 2 air masses here in PA. We have had very little clear weather this new moon, but I got three 15-minute subs one night before the moon came up. It cleared the trees behind the observatory about 1:00 am as it was sinking into the light dome of Harrisburg. I was a bit surprised at what I was able to reveal. Many thanks go to Russ Croman’s Gradient XTerminator.
The unusual shape is thought to be due either to a binary companion of the progenitor star or to magnetic fields guiding the ionized expanding gases. You can read more about it here - https://en.wikipedia.org/wiki/Red_Spider_Nebula . There is a spectacular Hubble image of it here - http://apod.nasa.gov/apod/ap121029.html |
The Saturn Nebula - Also designated as NGC 7009, this small, bright planetary nebula in Aquarius was discovered by William Herschel in 1782 and later named by Lord Rosse because of its visual resemblance to the planet, Saturn. It has a complex internal structure, as well as pointed ansae or handles on each side.
Telescope: Meade 8" LX200R @ f/7 with an Astro-Physics 0.67X telecompressor Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 20 X 2 minutes = 40 min |
NGC 6210 (The Turtle Nebula) - This planetary nebula is about 6500 light-years away in Hercules. It is a rather complex nebula with several expanding shells, some inside the very bright region around the progenitor star (go here for a Hubble image of that region - http://hubblesite.org/newscenter/archive/releases/1998/36/image/d/ ) and others farther out in the somewhat less bright region. Also there are numerous jets shooting out from the central region and punching through the shells forming ansae.
This object is somewhat difficult to image. It is very small, about 20 arcsec diameter for the primary nebulosity, and it has a lot of dynamic range from the very faint ansae to the bright central star (magnitude = 12.8). Even cutting my sub-exposure times down to 5 minutes, I saturated the region around the central star. However, I was able to get the ansae and some of the structure in the surrounding gas shells. Telescope: Meade 8" LX200R @ f/7.2 with Astro-Physics telecompressor Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 18 X 5 minutes = 1.5 hrs |
NGC 6894 - Also called the Diamond Ring Nebula (because in a small telescope the bright star on the periphery looks like a diamond), this planetary nebula in the constellation, Cygnus, is a typical example of the end of life for a star about the size of our sun, The ring of gas has been expelled from the blue central star which has burned all its nuclear fuel and is slowly cooling, However, the dead central star is still hot enough to illuminate the gas.
Telescope: Meade 8" LX200R @ f/7 with an Astro-Physics 0.67X telecompressor Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 18 X 15 minutes = 4 hrs 30 min |
NGC 6905 - This planetary nebula, also known as the Blue Flash Nebula, is about 3000 light-years away in the constellation, Delphinus. It was discovered in 1784 by William Herschel. Its complex inner structure is evidenced by the threadlike elements, and its most striking features are the conical appendages on either side. It has also been observed to be a variable nebula.
Telescope: Meade 8" LX200R @ f/7 with an Astro-Physics 0.67X telecompressor Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 16 X 15 minutes = 4 hrs |
NGC 6781 - This planetary nebula in the constellation, Aquila, is about 3000 light-years away. Although it appears to have a spherical shape, detailed studies of the structure have led to the speculation that it has a bipolar or cylindrical shape with its long axis nearly along our line of sight (see for example http://iopscience.iop.org/0004-637X/648/1/430/fulltext/65163.text.html ).
Telescope: Meade 8" LX200R @ f/7 with an Astro-Physics 0.67X telecompressor Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 16 X 15 minutes = 4 hrs |
NGC 7008 - A planetary nebula in the constellation, Cygnus, it is known as the Fetus Nebula. It was discovered by William Herschel in 1787 and is about 3000 light-years away. Its complex structure has led to speculation that it is the result of two stars ending their lives in rapid succession (for a good discussion of NGC 7008 see http://www.universetoday.com/15314/cosmic-mystery-ngc-7008-by-dietmar-hager/ ) .
Telescope: Meade 8" LX200R @ f/7 with an Astro-Physics 0.67X telecompressor Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 16 X 15 minutes = 4 hrs |
NGC 7048 - About 1900 light-years away in the constellation, Cygnus, this planetary nebula was discovered in 1878 by Jean Marie Edouard Stephan. Its angular size is 1 arcmin. Though mostly spherical in appearance, its complex structure is apparent both on its periphery and in its interior. Its blue central star is magnitude 18.3.
Telescope: Meade 8" LX200R @ f/7 with an Astro-Physics 0.67X telecompressor Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 16 X 15 minutes = 4 hrs |
NGC 7026 - This is a small (0.85 arcmin X 0.48 arcmin), fairly young planetary nebula 6000 light-years away in Cygnus that is called the Cheeseburger Nebula. I presume that is because visually it looks like a cheeseburger. It has a quite complex structure with lobes and loops caused by the outflowing gas from the progenitor star interacting with the gas and dust in the Milky Way.
Telescope: Meade 8" LX200R @ f/7 with an Astro-Physics 0.67X telecompressor Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 36 X 5 minutes = 3 hrs |
NGC 6826 - This object is very small, so you really have to click on the image to enlarge it to see the structure described below.
Also known as the Blinking Planetary because it appears to blink when viewed through a small telescope, this planetary nebula is about 2000 light-years away in the constellation, Cygnus. Its core, shown enlarged at the lower left, consists of the remnant of the star that exploded to create the nebula and a small, bright, oval region of gas. That oval region has some structure, including two bright spots at about 2 o'clock and 8 o'clock with a hint of red at their outer edges. These bright spots are Fast Low Ionization Emission Regions or FLIERs. The FLIERs are poorly understood. Visible in the main image outside the core is a faint, blue, spherical bubble of gas which was blown off the star when it exploded. Telescope: Meade 8" LX200R @ f/7 with an Astro-Physics 0.67X telecompressor Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 12 X 15 minutes = 3 hrs |
NGC 1514 - Also known as the Crystal Ball Nebula, this planetary nebula in Taurus was discovered by William Herschel in 1790. Until then, he thought that nebulosity was made up of faint, unresolvable stars, but this bright star surrounded by what he called "a faintly luminous atmosphere" seemed inconsistent with that view. The central star is now thought to be a double star with a period of rotation of about 10 days. The nebula is about 600 light-year away and has a diameter of about 2 arcmin. In infrared images NGC 1514 has an unusual, double loop shape (see http://www.nasa.gov/mission_pages/WISE/news/wise20101117.html ).
Telescope: Meade 14" LX200GPS @ f/7 with Starizona SCT corrector Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 6 X 30 minutes = 3 hrs |
Messier 76 - This planetary nebula in Perseus isalso know as the Little Dumbbell. The red gas is hydrogen and the blue gas is mostly oxygen.
Telescope: Meade 14" LX200GPS @ f/7 with Starizona SCT corrector Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 10 X 30 minutes = 5 hrs |
Abell 82 - This planetary nebula in Cassiopeia is rarely imaged. If M76 is the Little Dumbbell Nebula, then this is the Micro-Dumbbell Nebula. It is about 90 arc-sec wide. The only information I could find is here - http://www.cloudynights.com/topic/508178-abell-82-rarely-imaged-mini-dumbell-planetary-nebula/ .
Telescope: Meade 14" LX200GPS @ f/7 with Starizona SCT corrector Camera: SBIG ST-8300C Autoguiding: Starlight Xpress OAG with Meade DSI using PHD2 Exposure: 12 X 30 minutes = 6hrs |
Kohoutek 4-8 - This is an image I made in May of 2013 in Chiefland, FL, of a region in Scutum that contains the planetary nebula, IC1295, and the globular cluster, NGC 6712. At the time I did not know that there is another planetary nebula in the region. In the August, 2015, issue of Sky and Telescope Sue French describes her visual detection of a tiny (stellar size) planetary nebula, Kouhoutek 4-8 (also designated PK 25-4.1 and PN G25.3-4.6), near IC 1295. I wondered if it was visible in my image, so I took a close look. The result is shown. My image agrees with Sue French’s observation that Kohoutek 4-8 is rich in OIII (i.e. blue in color).
Telescope: Meade 14" LX200GPS @ f/2 with Hyperstar 3 Camera: SBIG ST-8300C Autoguiding: Orion ST-80 with Meade DSI using PHD Exposure: 24 X 5 minutes = 2 hrs |
MORE - CLICK ON A THUMBNAIL TO VIEW A LARGER IMAGE WITH A DESCRIPTION.