Hubble Views ‘Ghostly’ Galaxy Lacking Dark Matter
This large, fuzzy-looking galaxy is so diffuse that astronomers call it a “see-through” galaxy because they can clearly see distant galaxies behind it.
The ghostly object, catalogued as NGC 1052-DF2, doesn’t have a noticeable central region, or even spiral arms and a disk, typical features of a spiral galaxy. But it doesn’t look like an elliptical galaxy, either. Even its globular clusters are oddballs: they are twice as large as typical stellar groupings seen in other galaxies.
All of these oddities pale in comparison to the weirdest aspect of this galaxy: NGC 1052-DF2 is missing most, if not all, of its dark matter. An invisible substance that makes up the bulk of our universe, dark matter is the underlying scaffolding upon which galaxies are built. It’s the glue that holds the visible matter in galaxies — stars and gas — together.
The galaxy contains at most 1/400th the amount of dark matter that astronomers had expected. But how it formed is a complete mystery.
The galactic oddball is as large as our Milky Way, but it had escaped attention because it contains only 1/200th the number of stars as our galaxy. Given the object’s large size and faint appearance, astronomers classify NGC 1052-DF2 as an ultra-diffuse galaxy.
Based on the colors of its globular clusters, NGC 1052-DF2 is about 10 billion years old. It resides about 65 million light-years away.
The image was taken Nov. 16, 2016, by Hubble’s Advanced Camera for Surveys.
Credits
NASA, ESA, and P. van Dokkum (Yale University)| About The Object | |
|---|---|
| Object Name | NGC 1052-DF2 |
| Object Description | Ultra Diffuse Galaxy |
| R.A. Position | 02:41:46.728 |
| Dec. Position | -08:24:09.871 |
| Constellation | Cetus |
| Distance | The galaxy is 62 million light-years away from Earth. |
| Dimensions | Image is 2.5 arcmin across (about 45,000 light-years) |
| About The Data | |
| Data Description | The HST observations include those from program (P. van Dokkum) |
| Instrument | ACS/WFC |
| Exposure Dates | 16 Nov 2016 |
| Filters | F606W, F814W |
| About The Image | |
| Color Info | 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 Red: F814W |
| Compass Image |  |
| About The Object | |
|---|---|
| Object Name | A name or catalog number that astronomers use to identify an astronomical object. |
| Object Description | The type of astronomical object. |
| R.A. Position | Right ascension – analogous to longitude – is one component of an object's position. |
| Dec. Position | Declination – analogous to latitude – is one component of an object's position. |
| Constellation | One of 88 recognized regions of the celestial sphere in which the object appears. |
| Distance | The physical distance from Earth to the astronomical object. Distances within our solar system are usually measured in Astronomical Units (AU). Distances between stars are usually measured in light-years. Interstellar distances can also be measured in parsecs. |
| Dimensions | The physical size of the object or the apparent angle it subtends on the sky. |
| About The Data | |
| Data Description |
|
| Instrument | The science instrument used to produce the data. |
| Exposure Dates | The date(s) that the telescope made its observations and the total exposure time. |
| Filters | The camera filters that were used in the science observations. |
| About The Image | |
| Image Credit | The primary individuals and institutions responsible for the content. |
| Publication Date | The date and time the release content became public. |
| Color Info | A brief description of the methods used to convert telescope data into the color image being presented. |
| Orientation | The rotation of the image on the sky with respect to the north pole of the celestial sphere. |
