Are the viewable nebulae only in our galaxy?

Are the viewable nebulae only in our galaxy?

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Where are all the nebulae located?

Yes, a simple question that should be obvious but apparently is not to me.

To be more explicit, how far are all these objects? Are they mostly in our galaxy?

I'm not suggesting that the Milky Way galaxy is the only galaxy that has nebulae, but that the ones we have pictures of are only within the Milky Way… if that is indeed the case.

This may also apply to stars themselves. What is the radius in ly of discernibility of (most) stars? Is it beyond the distance to the center of our galaxy (where even in principle individual stars might be discernible but there's too much of a mess to differentiate)?

1) The nebulae are spread out over the universe in many different galaxies. Nebulae called extra-galactic nebulae are nebulae outside of our galaxy. They aren't common, but we can see them.

2) Most of the ones we can see, such as the Helix nebula or the Orion nebula, are in our galaxy, but the ones outside of our galaxy are just more harder to see - there is a same dispersion of nebulae in our galaxy than in other galaxies.

3) Credit to @AtmosphericPrisonEscape (thanks!) - many nebulae outside of our galaxy are too dim for us to see. I assume that since the Tarantula Nebula is so massive and prominent, it is able to be visible from such a far distance.

For instance, NGC 2070, or the Tarantula nebula, located in the LMC. (Link: Here). The LMC is rather close to us, and the nebula is around 160,000 light years away.

I really can't find other major nebulae that are outside of our galaxy, but there are a lot of research papers on them, so they are visible - just not as prominent as the ones in our galaxy.

Some research papers with extra galactic nebulae include: Here, Here, Here, and there are many more online.

I don't understand the 2nd part of your question with the coordinates, but I hope this at least helps!

Firstly you have to specify what you mean by nebulae.
There is a historical term that some of @MystaryPi's links refer to, "extragalactic nebulae". An extragalactic nebula only existed until around the 1930s, as it was then realised, that extragalactic nebulae are not nebulae but galaxies like our milky way.
The classical papers by Hubble and Zwicky that were linked in the other answer were part of establishing this fact. This is why until today, misleadingly, galaxies are sometimes referred to as nebulae.

A planetary nebula (which is an ejected shell of a late-type star) wouldn't be visible in another galaxy neither with the eye nor large telescopes and long-time exposure. They simply posses a much too low surface brightness.

10 Most Spectacular Nebulae in the Universe

While we have all marvelled at the spectacular images of various types of nebulae we have seen on-screen or in magazines, its easy to forget that each image we see represents a brief snapshot of the ongoing cycle of star birth and death across the Universe. After all, diffuse nebulae are not just clouds of gas and dust in space in which stars are born, but another type called planetary nebula are those places created when a star reaches its final evolutionary state, and changes from a red giant to a white dwarf, in the process shedding its outer layers of gas to form a planetary nebula. Although massive stars may instead become neutron stars, over 97% of the stars in our Milky Way will eventually end their lives as a white dwarf, including the Sun.

Which is why we have compiled this list of lesser known, but nevertheless spectacularly beautiful nebulae, that reveals these huge structures in a variety of forms which illustrates the ongoing cycle of star birth and death across the Universe.

Lemon Slice Nebula

– Nebula type: Planetary nebula
– Constellation: Camelopardalis
– Coordinates: RA 12h 33m 06s | Dec. +82° 34’ 00”
– Distance: 4,500 light years
– Diameter: Core: 0.4 light years

– Magnitude: 12.3
-Other designations: IC 3568

Image: HST data

Located just 7.5 degrees away from the Pole Star, this is one of the least complex planetary nebulae known, with an almost perfectly spherical morphology. The progenitor star appears to have been an asymptotic red giant, the remains of which can be seen even with modest amateur equipment. This particular star is, however, still heating up, and its current temperature is an estimated 57,000K, at a luminosity of at least 2,000 times that of the Sun. The structure is still very young, which explains the almost total lack of detail or texture in the core, which is expanding at the rate of about 12 km/s or so. The faint halo that surrounds the core region is a shell of dust, while the core consists mostly of ionized helium. The name “Lemon Slice Nebula” derives from a yellow, false color image that originally made the nebula famous.

Mystic Mountain

Image: NASA, ESA, and M. Livio

– Nebula type: Star-forming Pillars & Herbig-Haro Objects with Jets
– Constellation: Carina
– Coordinates: RA 10h 44m 2.38s | Dec. -59° 30′ 29.55″
– Distance: 7,500 light years
– Diameter: Field of view- 1.39 x 1.28 arc minutes
– Age: First observed by Hubble on Feb. 1-2, 2010.
– Other designations: Carina Nebula, HH 901, HH 902

Looking more like the cover of a science fiction novel, this highly enhanced view of a “mountain” of dust and gas in the larger Carina Nebula is the perfect example of a stellar nursery. This image shows the very tip of a pillar of gas and dust (that measures all of three light years from top to bottom), that is being blown apart by the solar winds of nearby stars. However, the assault by hot, energetic stars from outside is deforming the pillar, causing tumultuous internal currents that trigger star formation within the structure. Evidence of this can be seen in the form of the purple jets of light and matter (lower left of the frame) emerging from the dust and gas surrounding such newborn stars.

Monkey Head Nebula

Image: NASA, ESA, Hubble Heritage Team (STScI/AURA)

– Nebula type: Emission nebula
– Constellation: Orion
– Coordinates: RA 06h 09.7m | Dec. +20°30′
– Distance: 6,400 light years
– Diameter: 40 degrees
– Magnitude: 6.8
– Other designations: NGC 2174

Located near the star Betelgeuse in the Orion constellation, this nebula is a hive of activity, with new stars forming at a relatively fast pace, and many newborns just starting to emerge from their birth cocoons. The nebula covers an area larger than the full Moon, and while it is visible with binoculars, a small telescope is needed to reveal finer details and texture. This nebula is thought by most investigators to have been created through the process of hierarchical collapse, which is another way of saying that the current structure is the result of a much larger, but more diffuse cloud that had collapsed under its own gravity. This model partially explains the presence of several loose clusters of stars that are embedded within the nebula. However, these clusters will eventually cause the remaining gas and dust to disperse into the surrounding area within the next few million years.

Stingray Nebula

Image: NASA, Matt Bobrowsky, Orbital Sciences Corporation

– Nebula type: Planetary nebula
– Constellation: Ara
– Coordinates: RA 17h 16m 21.071s | Dec. -59° 29’ 23.64”
– Distance: 18,000 light years
– Diameter: App. 130 times the diameter of the solar system
– Magnitude: 10.75
– Age: 27 years (First observed by Hubble in 1990)
– Other designations: Hen 3-1357, PN G331

This planetary nebula was only discovered in its present form in 1990, in a position where a pre-planetary nebula was observed in 1971, which makes it the youngest and smallest of all known planetary nebulae. In fact, it was just 25 years ago that it became a visible planetary nebula, a process which usually takes around 100 years, a mere blip compared to millions of years stars exist. The progenitor star was an asymptotic, type B1 supergiant that blew off its outer layers, which are now drifting away from the stellar core. Note that as the nebula drifts away, the stellar remnant heats up, causing the nebula to emit the true, actual colors seen in this image. The color green is emitted by oxygen, blue is emitted by hydrogen, and red is emitted by nitrogen.

Dark Doodad Nebula

– Nebula type: Dark nebula
– Constellation: Musca
– Coordinates: RA 12h 25m 00s | Dec. -71° 42′ 00?
– Distance: 700 light-years
– Diameter: ˜3 degrees
– Other designations: Sandqvist 149, CG 21, BHR 80, TGU H1875, DCld 301.7-07.2, [DB2002b] G301.70-7.16

The dark Doodad is a very good example of just how opaque dust clouds can be. In this example, the streak of gas and dust near the centre of the frame is dense enough to prevent light from the stars behind it penetrating, creating the appearance of a cleft, or split through the star field in the back ground. The Doodad Nebula is visible from the southern hemisphere with large binoculars, close to the large globular cluster NGC 4372.

Coalsack Nebula

Image: MPG/ESO 2.2m telescope

– Nebula type: Dark nebula
– Constellation: Crux
– Coordinates: RA 12h 50m | Dec. -62° 30′
– Distance: 600 light years
– Diameter: 30–35 light years (radius)
– Other designations: C99

The Coalsack in Crux represents a different type of dark nebula, in the sense that it is not absolutely dark, since it has a faint glow that is produced by the light of the stars it is obscuring. This nebula is visible to the naked eye and has been known since 1499, when it was discovered by Vicente Yáñez Pinzón. Strangely, even though the Coalsack is the most prominent dark nebula in the southern Milky Way, it is not listed in the NGC or any other catalogue except for the Caldwell Catalogue, in which it is listed as C99.

– Nebula type: Diffuse nebula
– Constellation: Leo
– Coordinates: RA 10h 48m 19.0s | Dec. +12° 41′ 21?
– Distance: 38 (± 4.6) × 106 light years
– Diameter: ± 650,000 light years
– Age: App. 1 billion years

While all nebulae are big, the Leo Ring is exceptionally so, even though it is not the biggest known. However, this vast collection of dust and gas is the result of a collision between two huge galaxies, NGC 3384 and M96, which occurred about 1 billion years ago in the heart of the Leo Group of Galaxies. The collision was so violent that roughly a galaxy’s worth of gas (mostly hydrogen and helium) was expelled from both galaxies into intergalactic space, where it eventually settled into the ring structure seen to surround both galaxies today. However, the Leo Ring has since split into two discrete sections, and the parts are now drifted about 38 million light years apart.

Barnard’s Loop

– Nebula type: Emission
– Constellation: Orion
– Coordinates: RA 05h 27.5m | Dec. -03° 58′
– Distance: 518 or 1,434 light years, depending on the source consulted
– Diameter: 10 degrees (600 minutes of arc as seen from Earth)
– Magnitude: 5
– Age: About 2 million years
– Other designations: Sh 2-276

Part of the Orion Molecular Cloud Complex that also contains the Horsehead and Orion Nebulae, Bernard’s’ Loop is thought to have been created by a supernova event that occurred roughly 2 million years or so ago. The structure is also big enough to cover most, if not all of the Orion constellation consider the relative size of the Orion Nebula roughly in the centre of the Loop for comparison. The supernova that is credited with creating Barnard’s Loop is believed to have occurred in a multi-star system in an explosion that was powerful enough to propel the stars AE Aurigae, Mu Columbae, and 53 Arietis to velocities that place them in the “runaway star” category. Barnard’s Loop is visible without optical aid under dark skies.

Double Helix Nebula

Image: Spitzer Space Telescope

– Nebula type: Emission
– Constellation: Sagittarius
– Distance: 25,000 light-years
– Location: About 300 light years from the galactic centre

This nebula should not be confused with the similarly named Helix Nebula, which is a planetary nebula located in the constellation Aquarius. The Double Helix is so named for the effect that the strong magnetic fields close to the galactic centre have on gaseous material. In this case, the twisting, or rotating magnetic field lines have twisted the material shown here in false color into something resembling a DNA molecule, hence the name, Double Helix Nebula. Only part of this structure has been imaged, with the section shown here about 80 light years in extent. Most of the stars in this structure are only visible in infrared wavelengths, and efforts to image stars that are visible in optical wavelengths are continuing.

Crescent Nebula


– Nebula type: Emission
– Constellation: Cygnus
– Coordinates: RA 20h 12m 7s | Dec. +38° 21.3′
– Distance: 5,000 light years
– Diameter: 18’ × 12’
– Magnitude: 7.4
– Other designations: NGC 6888, Sharpless 105, Caldwell 27

This nebula has a rather complex origin, in the sense that it is being shaped by both the fast solar wind of the Wolf-Rayet star WR 136 (HD 192163) and by the slower moving solar wind from the same star when it evolved into a less energetic red giant star between about 250,000 and 400,000 years ago. The two conflicting solar winds from the same star created two shockwaves moving in opposite directions, with the slower inward-moving shockwave heating the piled-up material to temperatures where it emits X-rays. Even small telescopes of 80-mm aperture will reveal the nebulosity of the structure, while larger instruments fitted with a UHC or OIII filter will sometimes reveal a feature that resembles the Euro currency symbol hence the nebula’s other name, the “Euro Sign Nebula”.

Evenings with the Ring Nebula

By: Bob King June 3, 2020 0

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Like looking into a crystal ball the beautiful Ring Nebula offers us a vision of the Sun’s future. Slip this ring on your finger and you’ll be partners for life.

Visible light observations from the Hubble Space Telescope and infrared imagery from the Large Binocular Telescope were combined to create this dramatic view of the Ring Nebula. NASA / ESA

Everyone loves this cosmic donut. Like Saturn, the Ring Nebula is a must-see for beginners and seasoned amateurs alike. Whether you're just cutting your deep-sky teeth or attempting to see its central star — one of visual astronomy's Holy Grails — the Ring has it all. I'm an incurable ring fanatic, having observed this ghostly gem more than 150 times.

The Ring, also known as M57, is a planetary nebula, one of an estimated 10,000 or more believed to populate the Milky Way Galaxy (but fewer than 2,000 have been cataloged). They're among the most beautiful and colorful objects in the sky. Many are round with well-defined edges and reminded early astronomers of planets. While they're anything but, they do have a planetary connection. The Ring and its ilk contribute elements like carbon, oxygen, and nitrogen to the interstellar medium, material later incorporated into the next generation of stars and their attendant planets.

A gallery of planetary nebulae showcases their ephemeral beauty. Clockwise from top left are the Cat's Eye Nebula the Ant Nebula the Butterfly Nebula the Hourglass Nebula the Little Ghost Nebula and the Helix Nebula. NASA

A planetary nebula forms from the expanding shell of gas ejected by a red giant star as it evolves into a white dwarf. Powerful winds from the giant's blazingly hot core waft the star's atmosphere into space to create a shell of gas that can assume a variety of forms including spherical, helical, bipolar, and donut-shaped.

As the core compresses through self-gravity it becomes hotter and hotter, exceeding 100,000°C or nearly 20 times the surface temperature of the Sun. Hot enough to emit much of its light in the ultraviolet (UV). One of the reasons planetary nebulae central stars appear so faint is that our eyes don't detect UV. But the energetic UV photons ionize the expelled gases, making them fluoresce in delicate hues of green, red, and blue like multicolored smoke rings blown from some wizard's pipe.

Stars that are similar in size to the Sun (and up to about eight times as massive) eventually evolve into red giants, slough off their outer envelopes, and become planetary nebulae, ultimately leaving behind naked white dwarfs. ESA

The giant's atmosphere continues to expand and fade until all that's left is the former core, now an extremely compact white dwarf star roughly the size of the Earth. Stellar lifetimes are measured in billions of years but a typical planetary lasts only about 20,000 years, the blink of an eye. For a star between one and eight times as massive as the Sun this is the end game of the aging process. To gaze at the Ring through the eyepiece is to see the future of our own Sun 5 billion years hence.

Vega points the way to the Ring, which at magnitude 8.8 is bright enough to show faintly in my 10 × 50 finderscope. With an apparent diameter of 1.3′ and distance of approximately 2,400 light-years its true size is almost 1 light-year across, or a little less than one-quarter of the way from Earth to Alpha (α) Centauri. Even a 3-inch scope will show a small, round ball of silky mist with a darker center. A 6-inch reveals that M57 is shaped more like a football with a 12th magnitude star located 1′ east of the nebula's center.

Through my 15-inch Dob at low magnification the Ring is a dusty tumbleweed frozen in time against a beautiful field of stars. Recently I studied it through an O III filter with a magnification of 142× and saw something I'd never noticed before. Surrounding the bright ring I glimpsed a much larger ring of glowing haze about 4′ to 5′ across. To confirm the observation I "played the field" with averted vision many times and then compared it to the unfiltered view.

This sketch is a composite of two different views of the Ring Nebula in a 15-inch telescope, one through an O III filter at 142× and another at 428× without a filter. The filtered view shows the faint outer ring with an extension to the southeast. The unfiltered view highlights the nebula's hazy center, brighter patches within the main ring, and the faint central star. South is up. To learn more about M57 and how to sketch it, see an article by Howard Banich in the upcoming September issue of Sky & Telescope. Bob King

I've often seen diffuse halos of scattered light around bright stars but never around a nebula. Deep photos show that the bright ring is embedded in the faint, red glowing ionized hydrogen, and this is apparently what I saw. I encourage you to experiment with different nebula filters and share your views in the comments area.

High magnification works wonders on the Ring and is essential for pinning down the ever-elusive central star, a white dwarf with a mass 0.6 times that of the Sun and a surface temperature around 120,000°C. Despite a total luminosity of 200 times solar it shines at magnitude 15.8. You might see references to 14.8 but that's clearly too bright. Even in good seeing at 357× and 428× in my 15-inch (which can reach magnitude 16.2) the dwarf flirts at the edge of visibility. But when it briefly pops into view, hoo boy, what a sight. Like the twinkle of a snowflake in sunlight.

A nest of fainter nebulosity surrounds the familiar bright ring. At lower left is the barred spiral IC 1296. South is up. Adam Block / NOAO / AURA / NSF

The veil of nebulous haze that fills the Ring's interior doesn't help make the dwarf any easier to see but it does add a frosty beauty to the scene. So do the faint stars peppering the edges of the annulus. Along with the 12th-magnitude star to the east I also discerned three

14.5-magnitude stars in a line due north of the Ring and two exceedingly faint (

15.5–16.0) stars to the immediate southwest and northwest.

The eastern and western ends of the ring appeared noticeably fainter than the top and bottom. Careful observation revealed a brighter patch of nebulosity inside the southeastern section of the ring and several bright, crowded knots lining the outer, northeastern periphery. I also took the optional side trip to the retina-busting, 15th-magnitude barred spiral galaxy IC 1296. Located within a telescopic triangle of stars 4′ northwest of the Ring, I eked out a dim patch of haze involved with a 15th-magnitude field star.

From Earth (upper left) we look nearly straight down on the Ring Nebula. The black dot is the central star. You'll find a more detailed explanation of the Ring's morphology in this 2013 paper by C. R. O'Dell et al. C. R. O’Dell, Vanderbilt University NASA and ESA’s Hubble Space Telescope

Three-D studies of M57 show that it's shaped more like a barrel than a Cheerio. From our perspective we're looking down from above through the "hole" of a tilted barrel. Two lobes of ionized gases extend above and below a tire-shaped ovoid of more concentrated material surrounding the white dwarf.

Looking at the Ring Nebula lets us imagine what it might feel like to hover over a celestial object as if passing by in a spaceship. Which we are of course. A pretty blue one.

How Can You Tell If An Image Is A Galaxy Or A Nebula?

M81 is one of the brightest galaxies that can be seen from the Earth. It is high in the northern sky . [+] in the circumpolar constellation Ursa Major, the Great Bear. At an apparent magnitude of 6.8 it is just at the limit of naked-eye visibility. The galaxy's angular size is about the same as that of the Full Moon. The Hubble data was taken with the Advanced Camera for Surveys in 2004 through 2006. This color composite was assembled from images taken in blue, visible, and infrared light. Image Credit: NASA, ESA, and The Hubble Heritage Team (STScI/AURA)

Is a galaxy design really a nebula picture?

When we take a picture of an object out in space, exactly what you’re capturing with the camera depends pretty strongly on the type of camera you’re using, and if you’ve selected a specific wavelength of light that you’d like to capture. And while a nebula - which is just a pile of glowing gas - is usually sitting within a galaxy, the pictures we take of a galaxy and the pictures we can take of nebulae will look fundamentally different, if you know what to look for.

The pattern we associate with a galaxy - spiraling tendrils out from a central bright core - is present in both the stars and in the gas. If we take an image of a galaxy with a camera that is sensitive to the same section of light that our eyeballs are sensitive to (like the Hubble Space Telescope), most of what we capture is stars, and dark lanes of dust. Dust in a galaxy behaves like the dust you get on Earth, and blocks any light there might be behind it, so for a galaxy, we can’t see the starlight from behind it. In an image like the one below, you can also see some nebulae - in this case, glowing hydrogen - as a very particular shade of hot pink. But you can also see that the dark brown dust, the hot pink nebulae, and the background brightness of the stars, all follow the same spiraling pattern.

The large Whirlpool Galaxy (left) is known for its sharply defined spiral arms. Their prominence . [+] could be the result of the Whirlpool's gravitational tug-of-war with its smaller companion galaxy (right). Image Credit: NASA, ESA, S. Beckwith (STScI), and The Hubble Heritage Team (STScI/AURA)

There’s also elliptical galaxies, which look like the very cores of the spirals you might think of first. They tend to be amorphous, roundish fuzzballs of slightly redder stars where the spiral galaxies are a bluish white, ellipticals tend more towards orange-white. In both cases, the individual stars are totally invisible, blurred together in our images of them. The only stars that you can spot in an image of a galaxy are stars that happen to be close to us, and wind up projected onto the same patch of sky.

The elliptical galaxy NGC 4589. A dust lane is visible going vertically through the cloud of stars . [+] that make up this galaxy. Image Credit: NASA, ESA, and R. Foley (University of Illinois)

If you’re looking at an individual nebula - a small (on astrophysical scales), glowing cloud of gas, the patterns you see are very different. There are many more types of nebulae, but they are tied together as a class because they are all clouds of gas, heated to the point of glowing, and that heat is usually provided in the form of a very nearby star.

Planetary nebulae, which form at the end of a star’s lifetime, are heated by the faded star which remains as a white dwarf in their centers. Other nebulae, like the Orion nebula, are the clouds of gas which enveloped a denser region where new stars could form. Those new stars then heat the surrounding gas, both heating and sculpting it with their radiation and solar wind. Any kind of nebula should, therefore, have visible individual stars within it. Many images of nebulae have had to point the camera at the same patch of sky for a rather long time in order to capture the glowing gas in the image, and the stars have saturated the camera, and wind up with spikes protruding out of them. These spikes are entirely an artifact of how the telescope and detector are constructed, but if you see these spikes, you know you're looking at a star.

Resembling an opulent diamond tapestry, this image from NASA's Hubble Space Telescope shows a . [+] glittering star cluster that contains a collection of some of the brightest stars seen in our Milky Way galaxy. Called Trumpler 14, it is located 8,000 light-years away in the Carina Nebula, a huge star-formation region. Image Credit: NASA, ESA, and J. Maíz Apellániz (Institute of Astrophysics of Andalusia, Spain)

Clothing manufacturers are particularly bad about making the distinction between nebulae and galaxies properly - pretty much everything space-like, whether or not it’s even a real image, winds up being labeled as a “galaxy”. But with the above patterns in mind, you should be able to tell if what you’re looking at is more likely to be a nebula or a galaxy. Just look for stars.

How to observe our neighbouring galaxies

Take a tour of the galaxies of our cosmic neighbourhood the Local Group with our practical, deep-sky astronomy guide.

This competition is now closed

Published: October 1, 2020 at 2:00 pm

Have you ever wondered about the closest galaxies to the Milky Way, and whether or not it’s possible to see them from planet Earth? The answer is yes, provided you know how to find them. Our galaxy is just one member of the so-called Local Group, which is our galactic neighbourhood.

This wasn’t always known, however. In 1920, astronomy’s Great Debate saw the subject of galaxies and the scale of the Universe put under the spotlight.

In this guide, we’re going to reveal the top targets in the Local Group of galaxies, and how you can observe them through your telescope.

The Local Group includes two spiral galaxies (the Andromeda Galaxy, M31, and the Triangulum Galaxy, M33 seen above) two satellites of our Milky Way (the Large and Small Magellanic Clouds) the companion galaxies to M31 and several outlying galaxies (NGC 185 and 147), along with dozens of dwarf galaxies too faint for us to view.

From the Northern Hemisphere, several of the major galaxies of our Local Group can be seen in the autumn night sky, so let’s go on an extragalactic tour to see those that are accessible with modest equipment.

More deep-sky observing guides:

Discovering galaxies beyond our own

W e used to think we lived in an ‘island universe’ consisting only of our Milky Way.

Many of the faint smudges once called ‘nebulae’ turned out to be other island universes too, our view of the Universe being fundamentally altered in 1924 when Edwin Hubble proved they were galaxies much like our own.

As time went by, we found these galaxies liked to form groups, and it was quickly observed that we were part of one, which was imaginatively named the ‘Local Group’.

Our astronomy tour of the Local Group of galaxies

The Andromeda Galaxy

We’ll start with perhaps the most famous of them all, the Andromeda Galaxy, M31. To see the Andromeda Galaxy locate the Great Square of Pegasus (see chart below) and its top, left-hand bright star Alpheratz, or Alpha ( α ) Andromedae (which used to be designated Delta ( δ ) Pegasi).

Move a little to the left to find Delta ( δ ) Andromedae and then continue left to the next bright, orange-looking star, which is Mirach, or Beta ( β ) Andromedae.

Next, we take a sharp right turn up to Mu ( μ ) Andromedae and move a little further on to Nu ( ν ) Andromedae. Here, just to one side of Nu is a hazy, naked-eye patch of light – the core of the Andromeda Galaxy.

Take in M31’s patch of light with the naked eye. Often regarded as the furthest you can see with your eyes on a dark, moonless night, it takes an estimated 2.5 million years for the light from the Andromeda Galaxy to reach our eyes, so don’t blink!

Some records suggest it may have been noted as a little cloud by Persian astronomers as early as AD 905, while Charles Messier added it to his famous Messier Catalogue in 1764.

When viewing M31, try using averted vision – the art of looking slightly to its side. This will bring out fainter detail and more of an extended haze either side of the core, which is some of the Andromeda Galaxy’s disc.

Binoculars or a telescope will bring out even more of this hazy disc, and maybe hints of a spiral arm. This nearer arm is more sharply defined due to lanes of dust, which are often well seen in astrophotos.

In binoculars M31’s disc extends 3˚ from one side to the other, and it stretches even further when photographed.

The galaxy is tilted at about 13˚, which puts its central bulge and the tightly wrapped spiral arms nicely on view. It is amazing to think that M31 may contain over a trillion stars, according to data from the Spitzer Space Telescope, making it much larger than our own Milky Way.

Binoculars mounted on a tripod for stability should show there are two companions to the Andromeda Galaxy – M32 and M110 – roughly either side of the central bulge.

M32 lies close to the apparent edge of the bulge, but careful observation may just make out that the faint part of the bulge can extend past it.

M32 is an elliptical galaxy with little in the way of gas and dust left, literally just a mass of stars, glowing at mag. +8.1 with its major axis pointed roughly towards the centre of the Andromeda Galaxy.

It makes a triangle with two ninth magnitude stars and there is a seventh magnitude star nearby too, which helps locate it.

Across from M32, past the Andromeda Galaxy’s central bulge, we find M110.

This is another elliptical galaxy, shining at mag. +8.5, but it’s slightly larger than M32 and appears a little fainter because of its diffuse nature.

Both galaxies are gravitationally tied and effectively in orbit around the Andromeda Galaxy, so you could say we are seeing three galaxies for the price of one when we view it.

NGC 206

M31 has a few more tricks up its sleeve. With a telescope you can bring out further detail, such as its dust lanes and also a star cloud, NGC 206, of which there are similar objects in our own Milky Way, like M24, the Sagittarius Star Cloud.

NGC 206 does require medium to large telescopes to bring out its nature visually, and it can be photographed with wide, rich-field telescopes too.

Globular Clusters

There are also the globular clusters surrounding the Andromeda Galaxy to seek out. Again, large aperture is best: the brightest, G1 (also known as Mayall II), located 2.5˚ southwest of M31’s centre, glows at mag. +13.81 and is best seen in 10-inch or larger telescopes.

The Triangulum Galaxy

Now, let us turn to our next Local Group target, the Triangulum Galaxy M33, located in the Triangulum constellation.

Locate it from Mirach, Beta ( β ) Andromedae. It’s the same distance away from this star as M31, just in the opposite direction (see the star-hopping chart towards the top of the page). You’re looking for a small, hazy patch.

Despite technically being a naked-eye object at mag. +5.5, M33 doesn’t seem to be as easy to spot as you might think, so binoculars will be useful here. It doesn’t have the large, bright central bulge of M31.

This is down to the fact M33 is almost face-on to us and, without a bright central bulge, it is quite diffuse.

Yet from a dark, moonless site it is possible to spot it with the naked eye if you have keen eyesight. If you do, then you have just pushed your viewing distance out to an impressive 2.73 million lightyears.

With a telescope, M33 will show a hazy patch of light that hints at a spiral shape and it contains a wonderful surprise.

NGC 604

There is a large, gaseous nebulae located in M33’s spiral arms, similar to the Milky Way’s Orion Nebula but around 10 times larger. This is NGC 604, which shines at mag. +12.0 and is estimated to be 1,500 lightyears across.

It takes an 8-inch telescope, or larger, to really pick it out clearly against the haze of M33’s spiral disc. If you enjoy challenges, it’s worth exploring M33’s disc carefully to see if you can spot other similar nebulae such as NGC 595, NGC 592 and NGC 588, which are all fainter than NGC 604.

NGC 185 & NGC 147

Now we’re going to seek out the other two Local Group galaxies that are currently on show for Northern Hemisphere viewers: NGC 185 and NGC 147, also known as Caldwell 18 and 17 respectively.

To find them, start at M31 and trace a line from there to Schedar, or Alpha (a) Cassiopeia (see star-hopping chart on p62).

With at least a 6-inch reflector or a 4-inch refractor, look roughly halfway along this line for a glimpse of the brighter of the two Local Group galaxies.

This is the dwarf spheroidal galaxy NGC 185, which is a small hazy patch of light, glowing at mag. +9.2 a degree westward of the mag. +4.5 star Omicron ( ο ) Cassiopeia (see chart, right).

Extend the line between NGC 185 and Omicron Cassiopeia by another degree westwards to find the fainter smudge of light that is NGC 147. This is also a dwarf spheroidal galaxy glowing at mag. +9.7, so fainter and requiring a little more patience to pick out.

Both are satellites of the Andromeda Galaxy and lie slightly closer to us at 2 to 2.5 million lightyears. Interestingly, they appear to be gravitationally connected to each other.

More Local Group observations

These are the Local Group galaxies that are visible in this part of the sky from the Northern Hemisphere. Other members include Leo I, a diffuse elliptical galaxy of mag. +10.4, which lies just above Regulus and Leo II, a very faint diffuse galaxy at mag. +11.0, which lies above Delta ( δ ) Leonis.

Both are in the morning sky and are satellites of our Galaxy, but they are particularly tough to spot due to their spread-out, diffuse nature.

Southern Hemisphere Local Group

In the Southern Hemisphere, Local Group members include the Large and Small Magellanic Clouds, which are naked-eye objects and satellites of our own Milky Way.

The Andromeda Galaxy, M31, also has numerous satellite galaxies that are too faint for most backyard enthusiasts, but it’s possible that imaging technology may allow them to be spotted.

In recent years the members of the Local Group have increased as a result of the detection of many faint dwarf and sub dwarf galaxies. At the time of writing there are an estimated 80 members, most too faint to be seen in a backyard telescope, but it is possible that our own Milky Way Galaxy’s disc may hide others from view.

Equipment you will need to view galaxies in the Local Group

Our Local Group tour can begin with the naked eye which, depending on how dark your sky is, can show M31 and possibly M33.

A humble pair of binoculars – 7x50s to 15x70s – will reveal the galactic disc of M31, show M33 as a hazy glow and bring out M31’s two primary companions.

A wide-field telescope will improve the discs of both galaxies and make the dust lanes of M31 apparent. We used a 100mm spotting scope to track down the galaxies NGC 185 and the fainter smudge of NGC 147.

Larger scopes – 10-inch reflectors and above – will make short work of these two, but won’t reveal more detail.

Turning such scopes on M33 reveals some of its nebulae, like NGC 604. With a 10-inch reflector, M31’s disc begins to reveal similar features, like star cloud NGC 206, with more defined edges to its dust lanes.

The latest high-tech scopes will take you deeper. With live-stacked images in its electronic eyepiece, Unistellar’s eVscope (read our full eVscope review) can show fainter objects and colour in many of them.

Stacking images live via software can also bring more of these Local Group objects into view for public outreach events. Alternatively, the OVNI-M Series Night Vision Eyepiece uses phosphorous to intensify the view through any scope.

Equipment you will need to photograph galaxies in the Local Group

We live in amazing times, where smartphones can take images of the constellations and pick up both the Andromeda and Triangulum Galaxies in the Northern Hemisphere, and the Magellanic Clouds in the Southern Hemisphere.

Moving up to DSLRs, with a wide-field lens and a high ISO capability, you’ll also be able to image them, especially when fitted to a portable tracking mount.

By adding shorter focal-length lenses, the two companions of M31 can also be captured, along with the disc of the Andromeda Galaxy.

Even more detail can be imaged with an equatorial mount as a platform, either by taking long, guided exposures or by stacking lots of short exposures through a telescope.

This will capture the dust lanes of the Andromeda Galaxy, NGC 185 and NGC 147, and some of the nebulous parts of the Triangulum Galaxy such as NGC 604.

Increasing the aperture of your telescope and using a deep-sky CMOS or CCD camera will add even more detail and allow you to image the globular clusters of the Andromeda Galaxy too.

By using either an automated remote imaging setup or the Stellina imaging system (read our full Stellina review) it’s now possible to capture not just the popular members of the Local Group, but also many of the fainter targets.

Paul Money is an astronomy writer and broadcaster, and is reviews editor forBBC Sky at Night Magazine. This guide originally appeared in the October 2020 issue of BBC Sky at Night Magazine.

The Winds of Change:

Through his “ Copernican revolution ,” Kant moved the criterion of truth from assertions about an external reality to the immediacy of knowing yourself. His contribution practically put an end to philosophical speculation as it had been practiced for centuries. It established a firm basis for factual knowledge (in particular, the scientific method), but it also opened the way to agnosticism on ultimate issues. For better or for worse, his legacy has never been entirely transcended.



So why am I talking about Kant? Why is this Philosopher being recognized on the awesomest of awesome science pages? Because of two theories that some of you may or may not know about, but are now known as Kant’s theory.

Despite being a well-known Philosopher, his early works focused more on geology, astronomy, and physics. In his 1755 work, “ The Universal Natural History and Theories of the Heavens ,” Kant talks about astronomy and two noteworthy theories about the Heavens. The first is his “Nebular Hypothesis” on star and planetary formations , where he theorized that thin, dim clouds of dust and gas out in the cosmos would collapse in on themselves under the force of gravity, causing them to spin to form a disk. From this spinning disk, stars and planets would form, and from this type of formation, the rotation of Earth and the other planets would be explained.

Unlike the earlier great German philosophers, such as Gottfried Wilhelm Leibniz, Kant was not a mathematician in any way, shape, or form, so his nebular hypothesis was not given a mathematical equation until a French mathematician by the name of Pierre-Simon Laplace looked over Kant’s theory and figured it out. Ultimately, his theory became the well accepted model of star and planet formation. Today, we can even see this happening in stellar nurseries like the Orion Molecular Cloud. Despite this, some astronomy textbooks give the credit of the Nebular Hypothesis to Laplace only, and not the Kant-Laplace theory.

Solving the mystery of nebulae in astronomy

“From our home on the Earth, we look out into the distances … to imagine the sort of world into which we are born… But with increasing distance our knowledge fades, and fades rapidly, until at the last dim horizon we search among ghostly errors of observations for landmarks that are scarcely more substantial. The search will continue. The urge is older than history. It is not satisfied and it will not be suppressed.” -Edwin Hubble

From ancient times, humanity realized there’s more to the night sky than stars.

Stellar assemblies, like clusters and galaxies, are plentiful, but aren’t real nebulae.

A true nebulae, is a diffuse, cloud-like object, resulting from gas within a galaxy.

Dark nebulae — dusty, dense clouds of material — block incoming background light.

Many will form stars in the future, with their gas not having collapsed enough yet.

Some nebulae appear blue, reflecting the light from bright, newly-formed nearby stars.

These “reflection nebulae” are often dominated by just a single luminous, young star.

Other nebulae appear red, due to ionized electrons falling back down onto ionized hydrogen atoms.

These “emission nebulae” surround star-forming regions, exhibiting spectral lines peaking at 656 nanometers.

Other causes of nebulae are gaseous outflows from massive stars, like Herbig-Haro objects.

Supernovae create their own nebulae from the remnants of their catastrophic explosions.

Finally, Sun-like stars run out of fuel, expelling their outer layers into planetary nebulae.

Previously, outflowing matter from these stars create pre-planetary nebulae.

It’s only when the central star reaches 30,000 K, ionizing the surrounding gas, that a true planetary nebula occurs.

Mostly Mute Monday tells the story of a single astronomical phenomenon or object in visuals, images and video in no more than 200 words.

Hunting Giant Planetary Nebulae

By: Bob King May 4, 2016 2

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Mind your elders the next clear night and pay a visit to some of Spring's biggest and most ancient planetary nebulae.

A Hubble Space Telescope sampler of planetary nebulae.

I love looking at planetary nebulae and have ferreted out more than 200 of these shelly stellar remains in the past 20 years. Their delicate shapes and pastel colors not only delight the eye, but they possess subtle details that test the limits of vision: outer rings, darker centers, and those frequently elusive central stars that play peekaboo from behind pale veils of nebulosity.

Planetaries, so called because their generally round shapes reminded early observers of planets, represent a late stage in the evolution of Sun-like stars from red giant to white dwarf. Powerful stellar winds emanating from the star's core blow away its outer layers, creating an expanding shell of gas and dust.

The remaining core, compressed and heated to more than 46,000°F (26,000°C) becomes a white dwarf. Bathed in copious UV light from the dwarf, the former giant's atmosphere lights up like a neon donut. Some planetaries have binary central stars their interaction with each other and the expanding bubble add further complexity to a nebula's shape and evolution.

The planetary nebula phase is brief, lasting only around 10,000 years before the cast-off cloak become so distended it fades from view. Only the lonely white dwarf and whatever planets it might still possess soldier on. Such will be the fate of the Sun, one of the reasons that observing planetaries gives pause to reflect on the future of our own Solar System.

An O III filter blocks natural and human-made light pollution while allowing emissions of doubly ionized oxygen in planetary nebulae to pass through. The filter darkens the sky background and increases the nebula's contrast and visibility.
Bob King

There are an estimated 10,000 planetary nebulae in our galaxy, of which roughly 1,500 have been cataloged. Many are extremely tiny and look identical to stars. The only way to tell them apart is to "blink" them with a nebula filter such as a Lumicon O III or Orion Ultra-Block. Nebula filters pass the light of ionized oxygen, prominent in planetary nebulae, while suppressing skyglow and manmade light pollution. To "blink" a planetary, slide the filter back and forth between your eye and eyepiece while gazing at the nebula. The filter will cause the object to sharply brighten compared to the neighboring field stars, immediately identifying it as the nebula.

Planetaries come in all sizes from stellar to more than a degree across. We'll focus on the ones I like to call giants, the most familiar of which is the Helix Nebula in Aquarius, with a diameter more than half that of the full Moon.

The smallest of our featured objects spans 5.8′ and the largest 17′. For comparison, the Ring Nebula in Lyra measures 1.4′×1.0′ across. Large apparent size can mean an object is close by, but all ten of our featured nebulae lie from many hundreds to up to 2,000 light-years away. They're huge because they're ancient.

Jumbo size also means their light is spread over a large area, making some of these stellar windbags faint and difficult to see. For our featured nebulae, I recommend a 10-inch (25-centimeter) or larger telescope, dark skies and an O III-style filter. My observations were made from a rural site with a 15-inch (37-cm) reflector. Two were beyond my range, but the others were not what I would call difficult, only faint. Some, like Jones-Emberson 1, in Lynx reveal striking details while others, like Abell 31 in Cancer, look like huge, diffuse comets. I used a magnification of 64× and an O III filter for all observations.

All make for great hunting on spring nights, when you can't help but feel a time warp between these venerable smoke rings and the fresh green world sprouting up around you.

Abell 21, the Medusa Nebula, is one of the brighter of the large planetaries with a magnitude of about 10.
Jschulmann555 / Wikimedia Commons / CC BY-SA 3.0

* Abell 21 in Gemini: A remarkable object! Catch it right at the end of evening twilight in the western sky. Also known as the Medusa Nebula, it was immediately obvious and shaped like a puffy, backwards "C". With averted vision I could discern a brighter patch in either arm of the nebula. No luck seeing the "braided hair" texture that suggest Medusa's mane of snakes. Easy to find near Beta (β) Canis Minor. Diameter = 12′×9′.

Abell 31 in Cancer is one of the largest planetaries in the sky with nearly the same diameter as the brighter, more familiar Helix Nebula. The nebula's southern border shows a classic, streamlined "bow shock" where the moving nebula presses into the interstellar medium as it travels through space.
Don Goldman

* Abell 31 in Cancer: When many of us think of the constellation Cancer, the Beehive or M67 clusters come to mind. Who knew this big balloon of a planetary resided there? I see a nearly featureless, large glow almost centered on an 11th-magnitude star and elongated slightly east-west. The brightest part of the planetary lies very close west of the star. Large and diffuse but surprisingly easy to see using an O III filter. Mottled texture suspected with averted vision. Diameter = 17′×16′.

Jones-Emberson 1 in Lynx , a.k.a. The Headphones Nebula, is about 4 light-years across and 1,600 light-years away.
Adam Block / Mount Lemmon Sky Center / University of Arizona

* Jones-Emberson 1 in Lynx: What a contrast to Abell 36! You'll see lots of structure here. The gaping dark hole is obvious, but further observation will bring to view a pair of bright lobes or knots symmetrically placed on either side of the ring. Their neat resemblance to headphones or earbuds has earned it the nickname of The Headphones Nebula. One of the brightest of the dim objects in our spring sampler. Named for astronomers Jones and Emberson who discovered the nebula in 1939. Diameter = 7′×6′.

* Ellis-Grayson-Bond (EGB) 6 in Leo: Despite a thorough search I never turned up anything but suspected nebulosity in all the wrong places. Deep-sky observer and author Reiner Vogel sees an extremely faint patch of light. Photos reveal a faint smoke ring with a dark center. A large and very ancient nebula. Diameter = 13′×11′.

* Abell 35 in Hydra: Low declination, but this is an easy-to-see patchy glow with an amazingly bright +9.6 magnitude central star. Two other slightly fainter stars are involved. Although I can't distinguish the bar south of center, other observers have spotted it. I also couldn't make out the bow shock arc of nebulosity that wraps around the central star like a scarf flying in the wind. Diameter = 16′×11′.

Abell 36 displays an 11.5-magnitude central star with a temperature of 130,000°F (73,000°C). UV light from the star ionizes the nebula, causing it to glow.
Josef Pöpsel, Beate Behle, Stefan Binnewies at (c)

* Abell 36 in Virgo: To my eye a featureless, circular haze with a bright 11.5 magnitude central star. Faint but not difficult. I had hoped to see some of the whirls pictured in photos but perhaps the object's –20°declination added enough extinction to scrub them from view. Observers in the southern U.S. and points south should do much better. Diameter = 8′.

Although the bright, internal nebula is only 16″ long, it's embedded into a much larger envelope of matter ejected by the planetary's former red giant star. The brightest chunk of this conflagration, located to the lower left of the bright field star at middle right, is designated IC 4677.
Nordic Optical Telescope and Romano Corradi / Wikimedia Commons / CC BY-SA 3.0

* NGC 6543 in Draco: An astonishing, multi-faceted planetary also known as the Cat's Eye. Most of us stop by for the bright 9.8-magnitude interior nebula that looks like a miniature blue egg. A beauty in its own right. Next time, slap on the O III and you'll see an entirely different aspect. The egg lies at the center of a large, slightly textured disk of previously cast-off material 5.8′ across! A patch of nebulosity within the halo bright enough to get its own designation, IC 4677, lies about 2′ due west of the egg.

* Jacoby 1 in Boötes: Too tough for me in part because of several bright field stars that mess with dark-eye adaption. I suggest a 20-inch or larger for this one. If you do seek this fainty, the brightest portion of the ring lies immediately east-southeast of the 7.5-magnitude star set inside the southern half of this delicate ring-shaped nebula. Diameter = 11′.

Despite the glare of its 8.8-magnitude central star, LoTr 5 is not difficult to see.
Josef Pöpsel, Beate Behle, Stefan Binnewies at (c)

* Longmore-Tritton (LoTr) 5 in Coma Berenices: Very easy object appearing as a round, glowing patch offset from the bright 8.8-magnitude star at its center. The star is a binary — we see the G5 giant but tucked in close there's an invisible hot dwarf responsible for ionizing the nebula. Diameter = 9′.

* Ellis-Grayson-Bong (EGB) 1 in Cassiopeia: Vague and very faint, but I see a round patch about 5′ in diameter. Deep photos reveal a faint smoke ring with a dark center. Diameter = 5′.

I made rough sketches of a half dozen of the nebulae during recent nights with a 15-inch reflector using 64× and an O III filter.
Bob King

I normally would include a basic table and finder charts for each of our 10 planetaries, but German amateur astronomer Reiner Vogel has already done so in his excellent Large Planetaries Observing Guide, which is available as a free .pdf book. Check it out!

Eagle Nebula Details:

  • Messier: 16
  • NGC: 6611 (embedded star cluster)
  • IC: 4073
  • Object Type: Emission Nebula with Open Cluster
  • Constellation: Serpens
  • Distance: 7000 light-years
  • Apparent Magnitude: +6.2
  • Apparent Size: 65 x 50 Arc Minutes

The Eagle Nebula isn’t the only emission nebula with an embedded star cluster within it, not even close. Some other famous H II regions include the Orion Nebula , the Lagoon Nebula , and the Omega Nebula .

Other famous emission nebulae with embedded star clusters:

The Cat’s Eye Nebula

Unlike galaxies and star clusters and even emission nebulae, the class of objects known as planetary nebulae exist on a scale of space and time that’s comprehensible, relevant, and compelling to most humans.

Comprehensible because these tenuous exhalations of dying stars are roughly the size of a solar system, which means light can pass from one end of the nebula to the other in just a few hours, and even our current spacecraft could cross some of these nebulae in a matter of years.

Relevant because our own Sun will expire after creating its own planetary nebula in a few billion years when our star’s inner core boils off its outer layers in an intermittent nuclear frenzy.

And compelling because as you observe these objects with your telescope, you may be witnessing the death of other solar systems which once harbored intelligent civilizations that long ago passed into oblivion, or perhaps learned to travel elsewhere in the galaxy before it was too late. Amateur astronomy is, after all, a pastime of the imagination .

Most stars will eventually become planetary nebulae, if just for a few tens of thousands of years out of their billion-year life spans. About 3,000 planetary nebulae exist in our galaxy, and perhaps a hundred are visible to determined backyard stargazers with a small telescope. The “showpiece” planetaries like the Ring, the Blue Snowball, and the Dumbbell Nebulae are favorite targets of even beginning stargazers. Not much further down the list of accessible planetaries is the famous Cat’s Eye Nebula (NGC 6543). It’s one of the newest such nebulae, just a thousand years old, and one of the easiest to see because of its high surface brightness.

The Cat’s Eye is the only planetary nebula among the winding stars of the constellation Draco which lies between the Big and Little Dippers. The 8th-magnitude nebula is located about halfway between the stars delta (δ) and zeta (ζ) Draconis. For northern stargazers, the nebula (and Draco) are visible before midnight from May through November, more or less. These stars are not visible from the deep-southern hemisphere.

The location of the Cat’s Eye Nebula (NGC 6543) in the constellation Draco.

Unlike larger planetaries like the Helix Nebula, the Cat’s Eye is tiny, some 16″ across, and has a relatively high surface brightness which makes it easier to see in light-polluted skies. With a 4-inch or larger telescope at 30x to 40x, you’ll just be able to discern the nebula from the surrounding stars. It may look slightly fuzzy, with perhaps a greenish or turquoise color. The trick is distinguishing it from a star. That’s where more magnification will help, at least 100x and preferably more, to give it some size. If you thread a nebula (or light pollution) filter into your eyepiece, it will also help increase the contrast of the nebula compared to the stars and the background sky.

The central star of NGC 6543, the old star that’s casting off the nebula itself, is fairly bright and most telescopes reveal it easily with modest magnification. At 150x or more, the nebula shows some texture, including somewhat darker inner region and a brighter ring around the outside. The shape is slightly oval, and the color is quite pleasing compared to the whitish stars in the background. Like most small planetary nebulae, the Cat’s Eye responds well to high magnification if the sky is steady. In larger telescopes at 200x or more, you may see a glimmer of the intricate shape that lends the nebula its name.

A sketch of the Cat’s Eye Nebula (NGC 6543) made with a 120mm refractor at 222x. Credit: Diego Gonzalez.

In the 18th and 19th centuries, many astronomers thought planetary nebulae were patches of unresolved stars, which was not an unreasonable hypothesis. After all, as telescopes improved, once-unresolved star clusters were revealed to be tightly-packed groups of individual stars. Others thought nebulae were made of a shining “celestial fluid”. The debate was solved in 1864 by William Huggins, a self-taught British amateur astronomer and wealthy silk merchant who sold his business at age 30 to concentrate on astronomy full time. Huggins was the first to attach a laboratory spectroscope to a telescope to try to figure out the composition of celestial objects. When he turned a spectroscope to the Cat’s Eye, he found its spectrum was completely different from any star. He attributed the strange spectrum to an undiscovered element he called “nebulium”. Decades later, spectroscopists determined “nebulium” was really a form of ionized oxygen that exists only in the rarified vacuum of space. This type of oxygen ion is called OIII (“oh-three”). Huggins subsequent studies of stars and nebulae determined that celestial objects were made of many of the same atoms as the Earth. “A common chemistry exists through the galaxy”, he wrote.

While the Cat’s Eye is modest in a backyard telescope, it is dazzling in long-exposure photographs. A splendid image from the Hubble Telescope made this nebula famous nearly two decades ago. Here’s an updated image from Hubble. The twists and turns in the nebula are a matter of current study, but they are likely the result of the complex interplay of a companion star with the dying star, intermittent energy production in the dying star, and stellar magnetic fields coupled with stellar rotation.

The size and expansion rate of the Cat’s Eye suggest the nebula is just 1,000 years old. The central star will continue to expand for another 10,000 years, give or take, just a tiny fraction of its total lifespan, until the central star runs out of atmosphere. The ejected gas and sooty dust from the outer and inner parts of the star will quickly cool and drift freely in interstellar space for millions of years. Some of this material may one day coalesce in dense clouds that will collapse and form new star systems. A planetary nebula is but one instance of the complex ecology of the Milky Way as old stars recycle themselves into new stars and planetary systems.

(Editor’s Note: The Cat’s Eye Nebula is one of more than 400 celestial objects you can see for yourself with the help of What to See in a Small Telescope, a series of online courses exclusively available to subscribers of