Is every star we see in the Milky Way?

When we look at the night sky, is it possible to see stars that lie beyond our own Galaxy?

Woman sitting looking up at the night sky.
Published: February 15, 2022 at 12:01 pm
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When you look up at the night sky from a dark location, you can expect to see a dazzling display of stars stretching from horizon to horizon.

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But you may have wondered whether all the stars that are visible from Earth are part of our galactic home, or whether we're actually observing stars in another, nearby galaxy.

The answer is that all of the stars you can see in the night sky belong to our own Milky Way Galaxy.

Read more:

Milky Way panorama Sérgio Conceição, Barrancos, Portugal, 23 May 2020. Equipment: Canon EOS R mirrorless camera
The band of the Milky Way, photographed by Sérgio Conceição, Barrancos, Portugal, 23 May 2020. Equipment: Canon EOS R mirrorless camera

The vast majority of the individual stars that can be seen all lie within a ‘bubble’ of space around the Sun about 10,000 lightyears across.

The billions of stars that lie outside this region are too distant to be seen individually and their starlight appears to coalesce into the misty band known as the Milky Way.

It appears as a band, rather than all over the sky, because the Galaxy is relatively flat.

So when you see the Milky Way from a dark sky site you’re looking along the plane of the Galaxy.

Observing stars beyond our Galaxy

An illustration showing what our Galaxy probably looks like when seen from afar. Our Solar System lies near the Orion Spur. Credit: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)
An illustration showing what our Galaxy probably looks like when seen from afar. Our Solar System lies near the Orion Spur. Credit: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)

It is possible to see stars outside of the Milky Way Galaxy, but not as individual points.

If you take a look within the wedge-shaped constellation of Andromeda you’ll see the elongated misty patch known as M31, or the Andromeda Galaxy.

For help locating it, read our guide on how to see the Andromeda Galaxy.

This is a separate island city of stars, just like our own Milky Way Galaxy, about 2.5 million lightyears distant.

The starlight from the billions of individual stars that populate M31 merge to form an elongated smudge.

The Andromeda Galaxy is the most distant object that can be seen with the naked eye under normal night sky conditions.

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This article originally appeared in the February 2010 issue of BBC Sky at Night Magazine.

Authors

Pete Lawrence, astronomer and BBC The Sky at Night presenter.
Pete LawrenceAstronomer and presenter

Pete Lawrence is an experienced astronomer and astrophotographer, and a presenter on BBC's The Sky at Night.

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