What do stars look like up close?

What does a star really look like, and how do astronomers know?

By Alastair Gunn

Published: Tuesday, 07 February 2023 at 12:00 am

The best example of how a star looks up close is our own Sun. From space, where the Earth’s atmosphere doesn’t affect the view, the Sun appears as an extremely bright, slightly yellow, disk.

This can be seen in many images taken in Earth orbit, or from the Moon, for example. This is just how other normal stars would look up close.

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Coronal mass ejections captured by NASA’s Solar Dynamic Observatory in June 2013. Credit: NASA/SDO

Stars emit light over a whole range of wavelengths (or colours).

The wavelength where the amount of light peaks, which depends on the star’s temperature, determines its apparent colour.

So, stars cooler than the Sun will appear redder, while those hotter will appear white or even blue.

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A red giant lies in the centre of open cluster M103, surrounded by a number of young, hot blue stars. Credit: Michael Deger / ccdguide.com

Features on the Sun’s surface or in its atmosphere (e.g. sunspots, prominences etc.) are completely swamped by the Sun’s brightness, so the unaided eye doesn’t see these.

But the dimmer the star, the more detail you would be able to discern because the contrast between these features and the overall brightness of the star is smaller.

So, for dim, red stars you may be able to see ‘starspots’ on its surface, or prominences in its atmosphere (just like those visible during total solar eclipses).

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Artist’s impression of a red dwarf star (left) being blasted with radiation from a spinning white dwarf star (right). Credit: M. Garlick/University of Warwick/ESO

We can never really be sure what a particular object looks like up close, without actually going there.

However, modern ‘space artists’ often work closely with astronomers to create realistic images of what the human eye would see.

So, most ‘artist impressions’ accompanying scientific press releases will give you a pretty good idea of how an object looks.