Nebulae

A youtube posting has gotten my attention. I have seen some of these fascinating Nebulae pictures before but continue to be amazed.



A nebula (Latin for "cloud";[2] pl. nebulae, nebulæ, or nebulas) is an interstellar cloud of dust, hydrogen, helium and other ionized gases. Originally, nebula was a name for any diffuse astronomical object, including galaxies beyond the Milky Way. The Andromeda Galaxy, for instance, was referred to as the Andromeda Nebula (and spiral galaxies in general as "spiral nebulae") before the true nature of galaxies was confirmed in the early 20th century by Vesto Slipher, Edwin Hubble and others.

Most nebulae are of vast size, even hundreds of light years in diameter.[3] Although denser than the space surrounding them, most nebulae are far less dense than any vacuum created in an Earthen environment - a nebular cloud the size of the Earth would have a total mass of only a few kilograms. Nebulae are often star-forming regions, such as in the "Pillars of Creation" in the Eagle Nebula. In these regions the formations of gas, dust, and other materials "clump" together to form larger masses, which attract further matter, and eventually will become massive enough to form stars. The remaining materials are then believed to form planets and other planetary system objects. ( Copied from Wiki )

en.wikipedia.org...

a reply to: skywatcher44

Thank you for the visual.

Hubble space telescope is the most important device ever made.

Yep, nebulae are beautiful, fascinating, and awe-inspiring. Winter is my favourite time for stargazing because you can see the Orion Nebula, which looks good even in binoculars. I tried taking a photo of it myself:



But of course the best views of nebulae come from proper astrophotographers. Here are some of my favourite:

www.rc-astro.com...
www.nightsky.at...

By the way, in the video the nebulae are presented mostly in false-colour. I prefer images of nebulae in natural colour, such as this image of the famous Pillars of Creation:



Most nebulae are primarily red in colour, due to the glow of ionised Hydrogen.

Before it was known that galaxies are collections of stars they were called nebulae. The definition has become more refined.

Some nebulae are literally bubbles blown into interstellar medium by stellar winds from massive stars. Such as NGC 7635 or "the Bubble Nebula":



Another great example is NGC 2359 "Thor's Helmet", created by a massive star about to go supernova:



Source for both images: www.adamblockphotos.com...

Images like that show a dynamic, evolving space. I'd love to see a timelapse of these nebulae spanning a million years.

a reply to: wildespace
Something I've wondered about:
If we were fortunate enough to be at a close (but far) enough distance from such a structure, would it be visible in that sort of glory?

Andromeda (M31) is big. It covers a reasonably good piece of sky. But it's pretty dim so at best it looks like a...nebula...a cloud, with the naked eye.

If we were close enough to NGC 7635, would it look anything like the images to our eye?

originally posted by: Phage
a reply to: wildespace
Something I've wondered about:
If we were fortunate enough to be at a close (but far) enough distance from such a structure, would it be visible in that sort of glory?

Andromeda (M31) is big. It covers a reasonably good piece of sky. But it's pretty dim so at best it looks like a...nebula...a cloud, with the naked eye.

If we were close enough to NGC 7635, would it look anything like the images to our eye?

I'm afraid it wouldn't, especially not when it comes to colours and fine structure. These nebulae are very faint and diffuse, and our low-light vision is B&W.

The Wikipedia article gives some impression of what you can see in a fairly large amateur telescope:

With an 8 or 10-inch (250 mm) telescope, the nebula is visible as an extremely faint and large shell around the star. The nearby 7th magnitude star on the west hinders observation, but one can view the nebula using averted vision. Using a 16 to 18-inch (460 mm) scope, one can see that the faint nebula is irregular, being elongated in the north south direction.

I think this approximately represents what we would see with the naked eye if we were close enough to that nebula.

The Andromeda galaxy represents a good example of our naked-eye limits: it's very large and relatively bright, and yet the best you can see under very dark skies and full dark-adapted vision is a dim and fuzzy oval of light, which is only the galactic core. If the Andromeda were much closer, we probably would start seeing its galactic disc as very faint light, similarly to how we see the Milky Way.

The only way to see these nebulae as they really are, is to look though a very large telescope like they have at professional observatories. With enough aperture, you will see the colours and finer detail. I remember reading one amateur reporting looking through such a telescope and seeing the golden colouration of the Homunculus nebula, and the true colours of the Ring nebula.

Another great way to look at nebulae would be through a large binocular telescope, not only because of the large aperture but also because using both eyes will give a clearer, smoother, and more detailed image:


www.brucesayre.net...

Here's a report of viewing the Lagoon nebula though a OIII filter using a 22-inch binocular telescope:

"Never have I viewed such bright and overwhelming detail in this object. My brain interpreted the stars as being in the foreground, bright billows and wisps of nebulosity being in the middle-ground and the fainter parts of the nebula as being in the background."

"The wide-angle eyepieces, plus the illusion of depth made me feel like I was inside the nebula. As I looked, the whole thing had an almost windswept feel as if I was standing on a hill with fog billowing and blowing around me. But the image was still, so that gave it a peaceful, calm and serene tone, rather than stormy and violent."

"The color was that unearthly fluorescent blue-green typical of all the bright emission nebulae, but instead of being present only in the brightest central area, it was suffused throughout the whole nebula, with varying intensity, giving rise to a sense of varying density and thickness."

"It was an incredible view that I will never forget."

One of my day-dreaming dreams is to look through a VLT-sized binocular telescope.

One thing worth noting regarding the stunning nebulae images posted by NASA and other organisations, is that many of them are false-colour images created from shots taken though narrowband filters (most commonly SII, Ha, and OIII, which correspond to emissions from ionised Sulphur, ionised Hydrogen, and ionised Oxygen respectively).

Such images are fairly easy to recognise by how they have mostly yellow-orange and blue-green colours, for example this Hubble closeup image of the Lagoon Nebula:


Source: www.spacetelescope.org...

These false-colour images, besides having scientific value, also help accentuate various structures in the nebulae, which in true colours looks mostly uniformly red or pink due to the prevalence of ionised Hydrogen.

You can compare the true-colour and false-colour images of the same nebulae at this excellent astrophotography site: www.rc-astro.com...

More info on how the Hubble colour images are created: hubblesite.org...

Phil Plait just published an article and video about nebulae, as part of his "Crash Course Astronomy": www.slate.com...


www.youtube.com...

Astronomers study a lot of gorgeous things, but nebulae might be the most breathtakingly beautiful of them all. Nebulae are clouds of gas and dust in space. They can glow on their own or reflect light from nearby stars. When they glow it’s usually predominantly red from hydrogen and green from oxygen, and when they reflect and scatter light it’s from massive hot stars, so they look blue. Stars are born in some nebulae, and create new ones as they die. Some nebulae are small and dense, others can be dozens or hundreds of light years across.

Enjoy.

New article of interest on phys.org. ( Pyramidal ? )

The star HD 44179 is surrounded by an extraordinary structure known as the Red Rectangle. It acquired its moniker because of its shape and its apparent color when seen in early images from Earth. This strikingly detailed Hubble image reveals how, when seen from space, the nebula, rather than being rectangular, is shaped like an X with additional complex structures of spaced lines of glowing gas, a little like the rungs of a ladder. Read more at: phys.org...

The star at the center is similar to the sun, but at the end of its lifetime, pumping out gas and other material to make the nebula, and giving it the distinctive shape. It also appears that the star is a close binary that is surrounded by a dense area of dust—both of which may help to explain the very curious shape. Read more at: phys.org...

Zoomable pic with the link..


Will add this link to a David Butler Youtube.. How Far Away Is It - 07 - Planetary Nebula (1080p) ( 18 m to enjoy )

www.youtube.com... ( Cannot load onto post )

Add an additional you tube presentation by David Butler explaining the three different kinds of Nebula.
Diffuse, emission and reflection..

Diffuse nebulae appear as light or dark clouds (called bright and dark nebulae), are irregular in shape, and range up to 100 light-years in diameter. Some bright nebulae, composed primarily of hydrogen gas ionized by nearby hot blue-white stars, radiate their own light; they are called emission nebulae and are characterized by narrow spectral emission lines. Other bright nebulae, existing near cooler stars and not receiving the radiation necessary to make them self-luminous, reflect the starlight and are called reflection nebulae. Over 300 bright nebulae have been cataloged; prime examples are the Orion Nebula , visible to the unaided eye, the Eta Carinae Nebula, and the smaller North America Nebula. Dark nebulae are detected as empty patches in a field of stars or as dark clouds obscuring part of a bright nebula in the background, as in the case of the Horsehead Nebula. Smaller bodies of dark nebulous matter having unusually high densities have been observed in some bright nebulous regions. Many astronomers believe that these bodies, called globules, are in the process of condensation and are the initial stages in the birth of stars.

encyclopedia2.thefreedictionary.com...

Another Phys.org presentation today.

" A Space Spider Watches Over Young Stars "

A nebula known as "the Spider" glows fluorescent green in an infrared image from NASA's Spitzer Space Telescope and the Two Micron All Sky Survey (2MASS). The Spider, officially named IC 417, lies near a much smaller object called NGC 1931, not pictured in the image. Together, the two are called "The Spider and the Fly" nebulae. Nebulae are clouds of interstellar gas and dust where stars can form. Read more at: phys.org...

apod.nasa.gov... " The Spider and The Fly "

Bubble Nebula.. 26 Years since Hubble Launch..

This new NASA/ESA Hubble Space Telescope image, released to celebrate Hubble's 26th year in orbit, captures in stunning clarity what looks like a gigantic cosmic soap bubble. The object, known as the Bubble Nebula, is in fact a cloud of gas and dust illuminated by the brilliant star within it. The vivid new portrait of this dramatic scene wins the Bubble Nebula a place in the exclusive Hubble hall of fame, following an impressive lineage of Hubble anniversary images. Twenty six years ago, on 24 April 1990, the NASA/ESA Hubble Space Telescope was launched into orbit aboard the space shuttle Discovery as the first space telescope of its kind. Every year, to commemorate this momentous day in space history, Hubble spends a modest portion of its observing time capturing a spectacular view of a specially chosen astronomical object.

www.dailygalaxy.com...

Published today.. Star Birth Areas --Nebulae

ESA's Herschel space observatory mission released today a series of unprecedented maps of star-forming hubs in the plane of our Milky Way galaxy. This is accompanied by a set of cataloges of hundreds of thousands of compact sources that span all phases leading to the birth of stars in our Galaxy. These maps and cataloges will be very valuable resources for astronomers, to exploit scientifically and for planning follow-up studies of particularly interesting regions in the Galactic Plane. Above is Herschel's view of the center of our Galaxy, the Milky Way, about 25 000 light-years away. Clouds of gas and dust appear distributed along a giant, twisted ring, over 600 light-years wide, which encompasses the supermassive black hole sitting at the Galaxy's core. Shaped as a disc, our Galaxy has a diameter of about 100 000 light-years and the Solar System is embedded in it, about half way between centre and periphery. The images provide an unprecedented view of the Galactic Plane, ranging from diffuse interstellar material to denser filamentary structures of gas and dust that fragment into clumps where star formation sets in. They include pre-stellar clumps, protostars in various evolutionary stages and compact cores on the verge of turning into stars, as well as fully-fledged stars and the bubbles carved by their highly energetic radiation.

www.dailygalaxy.com...

New interesting article today on Physics org,

Wind Nebula around a Magnetar..

Astronomers have discovered a vast cloud of high-energy particles called a wind nebula around a rare ultra-magnetic neutron star, or magnetar, for the first time. The find offers a unique window into the properties, environment and outburst history of magnetars, which are the strongest magnets in the universe. A neutron star is the crushed core of a massive star that ran out of fuel, collapsed under its own weight, and exploded as a supernova. Each one compresses the equivalent mass of half a million Earths into a ball just 12 miles (20 kilometers) across, or about the length of New York's Manhattan Island. Neutron stars are most commonly found as pulsars, which produce radio, visible light, X-rays and gamma rays at various locations in their surrounding magnetic fields. When a pulsar spins these regions in our direction, astronomers detect pulses of emission, hence the name. Typical pulsar magnetic fields can be 100 billion to 10 trillion times stronger than Earth's. Magnetar fields reach strengths a thousand times stronger still, and scientists don't know the details of how they are created. Of about 2,600 neutron stars known, to date only 29 are classified as magnetars. Read more at: phys.org...