Hubble checks out our Galaxy’s twin

Imagine you could step out of our Milky Way a few million light-years and take a look back. This is the sort of view you might see. That is because this dazzling new image from the Hubble Space Telescope is of a galaxy that is thought to resemble our own.

Barred spiral NGC 1073 may resemble our own Milky Way
Barred spiral NGC 1073 may resemble our own Milky Way. Credit: NASA/ESA

Known as NGC 1073, and lying 55 million light-years away in the constellation of Cetus, it is a spiral galaxy, like so many classic “star cities”, but has a distinctive bar across its middle. This bar apparently denotes a galaxy that has moved on from being a bright young thing and headed into middle age. Its time of intense star formation has ended and older, red stars begin to dominate rather than younger, blue ones.

Studies show that more than two thirds of spiral galaxies in the Universe today are of the barred type whereas only a fifth showed the feature in the younger, early Universe. The star-filled bars are thought to form as gravitational density waves channel gas towards the centre of the galaxy, making new stars and possibly also feeding a supermassive black hole lying there.

The new image, taken with the NASA/ESA space telescope, shows remarkable detail in its spiral arms. Look closely and you will also see many far more distant galaxies showing up in the background. In the top left of the image can be seen a rough ring-like structure of recent star formation that hides a bright source of X-rays labelled IXO 5. Astronomers say this marks the position where a black hole and a star are orbiting each other.

Intriguingly, three bright star-like points circling the galaxy are not stars at all, but brilliant quasars sitting billions of light-years further away. Their tremendous energy comes from matter heating up and falling into supermassive black holes at their hearts.

If you visit the official Hubble site, you can see a labelled image pointing out the quasars and that X-ray source, plus a wide-angle view of NGC 1073 that will give you a sense of how lost it is in the vastness of space.

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By Paul Sutherland

Paul Sutherland has been a professional journalist for nearly 40 years. He writes regularly for science magazines including BBC Sky at Night magazine, BBC Focus, Astronomy Now and Popular Astronomy, plus he has authored three books on astronomy and contributed to others.

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