NGC1052-DF2

Hubble Captures a Ghostly Galaxy

This Hubble Space Telescope snapshot reveals an unusual "see-through" galaxy. The giant cosmic cotton ball is so diffuse and its ancient stars so spread out that distant galaxies in the background can be seen through it.

Called an ultra-diffuse galaxy, this galactic oddball is almost as wide as the Milky Way, but it contains only 1/200th the number of stars as our galaxy. The ghostly galaxy doesn't appear to have a noticeable central region, spiral arms, or a disk.

Researchers calculated a more accurate distance to the galaxy, named NGC 1052-DF2, or DF2, by using Hubble to observe about 5,400 aging red giant stars. Red giant stars all reach the same peak brightness, so they are reliable yardsticks to measure distances to galaxies.

The research team estimates that DF2 is 72 million light-years from Earth. They say the distance measurement solidifies their claim that DF2 lacks dark matter, the invisible glue that makes up the bulk of the universe's contents. The galaxy contains at most 1/400th the amount of dark matter that the astronomers had expected.

The observations were taken between December 2020 and March 2021 with Hubble's Advanced Camera for Surveys.

About the colours

These images are a composite of separate exposures acquired by the ACS/WFC instrument on the Hubble Space Telescope. Several filters were used to sample narrow wavelength ranges. The color results from assigning different hues (colors) to each monochromatic (grayscale) image associated with an individual filter. In this case, the assigned colors are: Blue: F606W Green: F606W + F814W Red: F814W

About the data

The HST observations include those from program 15851 (P. van Dokkum)