{"id":54953,"date":"2024-02-12T14:18:23","date_gmt":"2024-02-12T14:18:23","guid":{"rendered":"http:\/\/a02212d7-19d8-42e3-a1d4-bc5c3a4d46ad"},"modified":"2024-02-12T14:32:37","modified_gmt":"2024-02-12T14:32:37","slug":"what-is-a-nebula-beginners-guide-to-cosmic-clouds-and-how-to-see-them","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/what-is-a-nebula-beginners-guide-to-cosmic-clouds-and-how-to-see-them\/","title":{"rendered":"What is a nebula? Beginner’s guide to cosmic clouds and how to see them"},"content":{"rendered":"

Majestic and mysterious, nebulae are some of the most beautiful deep-sky objects to be found in the night\u2019s sky. But what are these space clouds? And how are they created? <\/p>

By Ezzy Pearson\n <\/p>

Published: Monday, 12 February 2024 at 14:18 PM<\/p>

\n\n

A nebula is a cloud of dust and gas in space that’s illuminated and glows like a shining cosmic cloud.<\/p>

Nebulae are clouds of gas and dust and there are many scattered throughout the Milky Way, mainly in the galactic disc, and it\u2019s here that stars are born.<\/p>

The word ‘nebula’ is Latin for \u2018little mists\u2019, because astronomers once considered all deep-sky objects to be nebulae, galaxies included, because they were faint fuzzy patches in the otherwise black night.<\/p>

Astro images reveal that many nebulae have vivid colours \u2013 typically red\u00a0in emission nebulae from ionised hydrogen atoms and hues of blue stars in reflection nebulae.<\/p>

But the view through binoculars or a telescope will be quite different. Visually, nebulae appear in shades of grey.<\/p>

The Tarantula Nebula, captured by the Hubble Space Telescope, 3 February 2023<\/figcaption><\/figure>

These days, not only can we differentiate between nebulae and galaxies, but we know that several types of nebula exist.<\/p>

A nebula can measure lightyears across in size but they are very diffuse: a nebula the size of Earth would still only weigh a few kilograms.<\/p>

As they are clouds, blown about by the interstellar winds of our Galaxy as well as their own turbulence, nebulae often have weird and wonderful shapes.<\/p>

There are famously many nebulae that look like animals<\/a>, although of course this is as much to do with pareidolia (seeing familiar shapes in random objects) as anything else.<\/p>

\"The
The Pelican Nebula. Credit: Anthony McAvoy, Camborne, Cornwall<\/figcaption><\/figure>

Nebulae can vary hugely depending on how they were created, but many of the clouds are strongly related to the lifecycles of stars.<\/p>

Some are created when a star dies; others allow them to be born.<\/p>

One nebula, of a type known as a planetary nebula<\/a>, is called the Boomerang Nebula and is the coldest place in the Universe<\/a>.<\/p>

Different types of nebula<\/strong><\/h2>

There are many different kinds of nebula. Here we’ll look at some of the most famous types.<\/p>

Emission nebula<\/strong><\/h3>
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An image of the Orion Nebula, 1,500 lightyears away, with over 3,000 stars of differing sizes nestling within the vast cavern of rolling dust and gas. Credit: NASA, ESA, M. Robberto ( Space Telescope Science Institute\/ESA) and the Hubble Space Telescope Orion Treasury Project Team<\/figcaption><\/figure>

The most famous nebula of them all, M42, the Orion Nebula<\/a>, is as an emission nebula.<\/p>

Emission nebulae have a glow of their own, a result of stars within or nearby ionising the gas cloud.<\/p>

Reflection nebula<\/strong><\/h3>
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The blue glow of the Pleiades star cluster is one of the most famous examples of a reflection nebula. Credit: Steve Allen, Calne, Wiltshire<\/figcaption><\/figure>

On the other hand reflection nebulae, like the one around the Pleiades<\/a> star cluster in Taurus, are visible because of nearby stars nearby lighting up the gas and dust, just as the Sun lights up a cloud in an otherwise blue sky.<\/p>

Dark nebula<\/strong><\/h3>
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The Horsehead Nebula, captured by the European Space Agency’s Euclid mission. Released 7 November 2023. Credit: ESA\/Euclid\/Euclid Consortium\/NASA, image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi; CC BY-SA 3.0 IGO<\/figcaption><\/figure>

Dark nebulae, such as the Horsehead Nebula, don\u2019t glow at all, as they are so dense they absorb light.<\/p>

They are only visible because they are in front of a bright nebula or field of stars.<\/p>

We effectively see a silhouette of the cloud, but no detail in it.\u00a0<\/p>

Planetary nebula<\/strong><\/h3>
\"M57,
M57, the Ring NebulaJames Webb Space Telescope, 21 August 2023Credit: ESA\/Webb, NASA, CSA, M. Barlow, N. Cox, R. Wesson<\/figcaption><\/figure>

You might think that planetary nebulae, such as the Ring Nebula in Lyra,\u00a0have\u00a0something to do with planets, but\u00a0you\u2019d be wrong.<\/p>

They get their name\u00a0because, through a telescope, many\u00a0have the appearance of a faint, small, fuzzy disc and can look a lot like a\u00a0planet.<\/p>

These nebulae are formed during the death of a star of similar mass\u00a0to the Sun.<\/p>

As it grows unstable, the\u00a0star puffs off its gaseous atmosphere to form clouds around it.<\/p>

Stars larger than the Sun end their days explosively in\u00a0a supernova, leaving a spectacular remnant in their wake.<\/p>

Nebulae and star formation<\/strong><\/h2>
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The Eagle Nebula, based on images obtained with the Wide-Field Imager camera on the MPG\/ESO 2.2-metre telescope at the La Silla Observatory. This is a star-forming region, so-called because it contains all the cosmic dust and gas necessary for new stars to be born.<\/figcaption><\/figure>

Not all nebulae form stars, but all stars (that we know of) started life in clouds of dust known as star-forming regions.<\/p>

The interstellar medium is the name given to the gas and dust that fills the spaces between stars.<\/p>

Over hundreds of millions of years this medium begins to clump together to form a cloud, a nebula.<\/p>

If the gas in the clouds becomes dense enough, it starts to collapse under its own weight, increasing the density even further.<\/p>

In the resulting turbulence, knots of gas form, their gravity<\/a> attracting even more gas so they ever larger until they become dense enough to form a star.<\/p>

\"Buried
Buried in the Eagle Nebula is a region of intense star formation. Hubble took an image of the region back in 1995, and their column shaped form earned the region the name “The Pillars of Creation”. – NASA, ESA and the Hubble Heritage Team (STScI\/AURA)<\/figcaption><\/figure>

Nebulae in reality vs pictures<\/strong><\/h3>

The popular idea of what a nebula looks like is often based on the spectacular images taken by the Hubble Space Telescope<\/a>, the James Webb Space Telescope<\/a> and other world class observatories.<\/p>

This can sometimes lead to disappointment when new astronomers see a faint and colourless nebula through their telescope for the first time.<\/p>

Nebulae aren\u2019t very bright so look dim to the human eye, but when astrophotographers take an image, they can leave the camera for several minutes to soak up as much light as possible, and use filters to enhance the colour.<\/p>

While visually observing nebulae might not be as visually arresting as a picture, nothing\u2019s quite the same as knowing you\u2019re seeing it for yourself.<\/p>

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Don’t expect a view like this through your refractor! This image of the Helix Nebula is captured in mutliple wavelengths by the Chandra X-ray Observatory, Hubble Space Telescope, Spitzer Space Telescope and Galaxy Evolution Explorer. Credit: X-ray: NASA\/CXC; Optical: NASA\/STScI.<\/figcaption><\/figure>

Nebula colours explained<\/strong><\/h3>

While most nebulae\u2019s natural colour is faint at best, they do have some colour based on the gases within them.<\/p>

When you heat a gas, it often emits a spectral line \u2013 light with a very precise colour that is specific to the kind of gas being heated.<\/p>

There are many elements that glow within a nebulae, and each of these elements might have several spectral lines. However, some of these are very faint, or aren’t at wavelengths visible to the human eye.<\/p>

While professional telescopes can be configured to pick these up, most amateur astronomers use a handful of filters.<\/p>

\"Rosette
Rosette Nebula bicolor by Mariusz Szymaszek, Crawley, Sussex, UK. Equipment: Skywatcher Evostar 80ED DS-Pro with flattener, NEQ6-Pro, QHY168C, Baader 7nm H-alpha, Baader O-III CCD, ZWO ASI120MC, Finderscope.<\/figcaption><\/figure><\/div><\/div>

Astrophotographers use a technique called narrowband imaging, where they use filters to pick out only these spectral lines. They can even use this technique to pick out colours that aren\u2019t visible to the human eye.<\/p>

Professional astronomers use these images to trace where certain types of gas are within a nebula.<\/p>

Meanwhile, image processors assigning each spectral band a colour \u2013 either red, green or blue, depending on which is closest to the spectral line \u2013 then blend the frames together to create full colour images.<\/p>

\"
An image of the Swan nebula taken by the Hubble Space Telescope. The top four images are taken through specific filters, which are then combined to create the bottom photographs. Using different filters creates a very different view of the nebula. – Dean Salman & the ESA\/ESO\/NASA Photoshop FITS Liberator<\/figcaption><\/figure>

How a nebulae gets its name<\/h3>

Like many astronomical objects, most nebulae have multiple names.There are several catalogues that list nebulae along with other deep-sky objects.<\/p>

The most commonly used are the Messier Catalogue<\/a>, the NGC (New General Catalogue of Nebulae and Clusters of Stars) and the IC (Index Catalogue). Most nebulae appear in at least one of these, if not all three.<\/p>

Many nebulae also have a popular name, which usually refers to where they are found (The Orion Nebula) or what they look like (The Witch’s Head Nebula).<\/p>

\"\"
The clouds of the Witch’s Head Nebula have an uncanny resemblance to a woman’s cackling face. – NASA\/JPL-Caltech<\/figcaption><\/figure>

7 nebulae to see for yourself<\/strong><\/h2>

Our pick of some of the best, most famous nebulae visible in the night sky. Use the RA and dec. coordinates to track them down with your telescope.<\/p>

The Orion Nebula, M42<\/strong><\/h3>
\"The
Credit: David Wills, Castillejar, Spain<\/figcaption><\/figure>