Asteroid photobombs Hubble snapshot of Galaxy UGC 12158 (compass image)

This is an annotated NASA/ESA Hubble Space Telescope image of the barred spiral galaxy UGC 12158, with compass arrows, a scale bar, and colour key for reference. It looks like someone took a white marking pen to it. In reality it is a combination of time exposures of a foreground asteroid moving through Hubble’s field of view, photobombing the observation of the galaxy. Several exposures of the galaxy were taken, which is evidenced by the dashed pattern.

The asteroid appears as a curved trail as a result of parallax: Hubble is not stationary, but orbiting Earth, and this gives the illusion that the faint asteroid is swimming along a curved trajectory. The uncharted asteroid is inside the asteroid belt in our Solar System, and hence is 10 trillion times closer to Hubble than the background galaxy.

Rather than being a nuisance, this type of data is useful to astronomers for doing a census of the asteroid population in our Solar System.

[Image description: Annotated image of barred spiral galaxy UGC 12158 against the black background of space, with compass arrows, a scale bar, and colour key for reference. The galaxy has a pinwheel shape made up of bright blue stars wound around a yellow-white hub of central stars. The galaxy is tilted face-on to our view from Earth. A slightly S-shaped white line across the top is the Hubble image of an asteroid streaking across Hubble’s view. Indicated filters are expressed as: “F475W” in blue, “F606W” in green, and “F814W” in red. At the bottom left corner is a scale bar labelled “60,000 light-years” over “30 arcseconds.” At the bottom right corner, the “E” compass arrow points towards the 2 o’clock position. The “N” compass arrow points towards the 5 o’clock position.]