This cloud-shrouded galaxy is a million light years closer to us than we thought

Illustration for article titled This cloud-shrouded galaxy is a million light years closer to us than we thought

This messy spiral galaxy, known only as NGC 247, is birthing stars at the ragged edges of its arms. It's part of a volume of space dominated by a bright cluster of galaxies called the Sculptor Group. Scientists have recently revised their estimates of how far away it is - turns out it's most likely a million light years closer than we believed.

According to the European Space Agency:

To measure the distance from the Earth to a nearby galaxy, astronomers have to rely on a type of variable star called a Cepheid to act as a distance marker. Cepheids are very luminous stars, whose brightness varies at regular intervals. The time taken for the star to brighten and fade can be plugged into a simple mathematical relation that gives its intrinsic brightness. When compared with the measured brightness this gives the distance. However, this method isn't foolproof, as astronomers think this period-luminosity relationship depends on the composition of the Cepheid.

Another problem arises from the fact that some of the light from a Cepheid may be absorbed by dust en route to Earth, making it appear fainter, and therefore further away than it really is. This is a particular problem for NGC 247 with its highly inclined orientation, as the line of sight to the Cepheids passes through the galaxy's dusty disc.


This image was used in a study done via the Araucaria Project on how we can measure true celestial distances. You can read that study here, and find out why we now believe that NGC 247 is only 11 million light years away, instead of 12.

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If they are so close, why don't they ever come to visit? :( ;)