{"id":53881,"date":"2024-01-16T10:23:48","date_gmt":"2024-01-16T10:23:48","guid":{"rendered":"http:\/\/c77f27f1-415c-4692-b29e-0b12aedff751"},"modified":"2024-01-16T11:35:02","modified_gmt":"2024-01-16T11:35:02","slug":"star-colours-explained-for-beginners","status":"publish","type":"rss_feed","link":"https:\/\/c01.purpledshub.com\/bbcskyatnight\/rss_feed\/star-colours-explained-for-beginners\/","title":{"rendered":"Star colours explained for beginners"},"content":{"rendered":"

Why are stars different colours, and which colours can we see in the night sky? <\/p>

By Anton Vamplew\n <\/p>

Published: Tuesday, 16 January 2024 at 10:23 AM<\/p>

\n\n

While the sizes of stars in the night sky are not apparent to the naked eye, we can see subtle colours in brighter stars<\/p>

Not all stars are the same size or colour, but why is this?<\/p>

In this beginner’s guide we’ll go through the science of star colours and reveal why some stars are red and some stars are blue<\/a>, and why stars are different colours at all.<\/p>

Star colours and temperature<\/strong><\/h2>
Globular cluster M15 is filled with stars of different colours. Blue stars are hot and golden stars are cooler. Credit: ESA, Hubble, NASA<\/figcaption><\/figure>

Star colours are an indication of how hot a star’s visible \u2018surface\u2019 is.<\/p>

As a star\u2019s temperature increases, as a result of there being more gas in the star \u2013 and hence more fuel to burn \u2013 it becomes hotter.<\/p>

Its colour changes from orange, through yellow, to white.<\/p>

Hottest stars are blue, with temperatures up to 40,000\u00baC. Coolest stars are red with surface temperatures of about 3,000\u00baC.<\/p>

\"A
A guide to the different types of stars, their temperature, structure and colours.<\/figcaption><\/figure>

You might have seen diagrams showing how different stars compare if they are put next to each other.<\/p>

This way you can compare the large, bluish star Vega<\/a> with the seemingly tiny red star of Proxima Centauri<\/a>.<\/p>

The artist’s illustration at the top of this page shows how stars<\/a> glow different colours according to their temperature.<\/p>

\"The
The colourful stars of the Antares Region captured by Rafael Compassi.<\/figcaption><\/figure>

If you look up on a clear night, you\u2019ll see there are bright stars that sparkle with a tint of their true colours.<\/p>

Some stars also appear to flicker between different colours as a result of the distorting effects of Earth’s atmosphere, which is also the reason why stars twinkle<\/a>.<\/p>

There are the red stars of Betelgeuse<\/a> in Orion, Aldebaran<\/a> in Taurus and Antares<\/a> in Scorpius. There\u2019s the golden-looking Arcturus in Bo\u00f6tes<\/a>, the yellowish Capella in Auriga<\/a> and the blue-whites of Rigel<\/a> in Orion and Spica in Virgo.<\/p>

But this is only a hint of the true nature of the heavens. If only our eyes could see them, the entire night sky would be filled with the most amazing colours.<\/p>

So what\u2019s up with our eyes? Nothing, of course \u2013 they\u2019re just not able to pick up colours in faint light. We evolved as a daytime species, and our eyes evolved to work with the powerful light from the Sun.<\/p>

\"The
The orange-red colour of the cooler star Betelgeuse above centre contrasts the hot blue stars that make up the rest of Orion. Credit: Rolf L\u00f6hr \/ CCDGuide.com<\/figcaption><\/figure>

Why some stars appear white<\/strong><\/h2>

Inside each eyeball we have cells that enable us to see, called rods and cones. The more numerous rods pick up light intensity, while the cones add in the colour.<\/p>

As the light intensity falls, the cones begin to switch off and go to sleep. A good example of this can be witnessed in the evening after the Sun has set.<\/p>

If you are outside, you may have noticed that the general scene begins to lose its colour as dusk sets in.<\/p>

This is simply due to your cones not having enough light to function, so they turn off.<\/p>

If we translate this to the sky, it\u2019s easy to work out that it is only the brighter stars that are able to set off any of the cones \u2013 thus enabling us to see some colour.<\/p>

The other stars are too faint for this and so with the naked eye we only see them as white.<\/p>

\"This
This mosaic of stars Rigel, Betelgeuse and Sirius was created by capturing images 60 seconds apart to compare the differences in colour caused by Earth\u2019s atmosphere splitting the starlight. Credit: Amanda Cross<\/figcaption><\/figure>

Observing star colours<\/strong><\/h2>

There are a few things to take into account if you’re interested in seeing a variety of star colours.<\/p>

Time of year<\/strong><\/h3>
\"The
The blue stars of the Pleiades are high in the night sky throughout the winter months. Credit: Tommy Nawratil \/ CCDGuide.com<\/figcaption><\/figure>

For naked-eye stargazing in particular, one of the main factors affecting your chances of seeing any coloured stars is choosing the right time of year.<\/p>

The winter skies in particular are graced with the most bright stars that show a colour tint. However, there is the odd star or two visible at any time in any month.<\/p>

Light pollution<\/strong><\/h3>
\"The
The glare of light pollution will seriously impede your view of the night sky. Credit: Steve Marsh<\/figcaption><\/figure>

It cannot be underestimated how detrimental streetlights or general town sky-glow is.<\/p>

We all know that artificial lighting can wash out the number of stars, and it does nothing for the colours of the stars that remain visible either. Therefore, the darker your observing location, the better.<\/p>

Telescopes & binoculars<\/strong><\/h3>
\"Even
Even a modest pair of binoculars should allow you to pick out different colours in the stars. Credit: lucentius \/ Getty Images<\/figcaption><\/figure>

By using one of these, you can more or less overcome all the previous hindrances and obstacles to good colour-spotting.<\/p>

A telescope will show the fainter stars and by magnifying their light, it\u2019ll bring out their colours too. You can also try de-focusing, thereby increasing the size of a star\u2019s light from a point source to a coloured disc.<\/p>

Dark adaption<\/strong><\/h3>
\"Dunkery
Dunkery Beacon in Exmoor National Park is one of many places in the UK where beautiful vistas of the night sky can be seen. Credit: Keith Trueman<\/figcaption><\/figure>

Make sure your eyes are dark-adapted. Staying in a dark place for an hour will enable your rods and cones to get as much out of the feeble starlight as possible.<\/p>

Even better: get yourself to a local dark-sky location. You should also remember to use a red-light torch when finding your way in the dark, the red light won\u2019t affect your dark adaptation as much as other colours.<\/p>

This article originally appeared in the July 2011 issue of BBC Sky at Night Magazine.<\/strong><\/em><\/p> <\/body><\/html>\n

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