A single member of a galaxy pair takes centre stage in this NASA/ESA Hubble Space Telescope Picture of the Week. This beautiful spiral galaxy is NGC 3507, which is situated about 46 million light-years away in the constellation Leo. NGC 3507 is classified as a barred spiral because the galaxy’s sweeping spiral arms emerge from the ends of a central bar of stars rather than the central point of the galaxy.
Though pictured solo here, NGC 3507 actually travels the Universe with a galactic partner named NGC 3501 that is located outside the frame. NGC 3501 was featured in a previous Picture of the Week. While NGC 3507 is a quintessential galactic pinwheel, its partner resembles a streak of quicksilver across the sky. Despite looking completely different, both are spiral galaxies, simply seen from different angles.
For galaxies that are just a few tens of millions of light-years away, like NGC 3507 and NGC 3501, features like spiral arms, dusty gas clouds, and brilliant star clusters are on full display. More distant galaxies appear less detailed. See if you can spot any faraway galaxies in this image: they tend to be orange or yellow and can be anywhere from circular and starlike to narrow and elongated, with hints of spiral arms. Astronomers use instruments called spectrometers to split the light from these distant galaxies to study the nature of these objects in the early Universe.
In addition to these far-flung companions, NGC 3507 is joined by a far nearer object, marked by four spikes of light: a star within the Milky Way, a mere 436 light-years away from Earth.
[Image Description: A spiral galaxy seen face-on. Its centre is crossed by a broad bar of light. A glowing spiral arm extends from each end of this bar, both making almost a full turn through the galaxy’s disc before fading out. The arms contain sparkling blue stars, pink spots of star formation, and dark threads of dust that follow both spiral arms into and across the central bar. A foreground star sits atop the galaxy.]