The European Space Agency's Faint Object Camera on board NASA's Hubble Space Telescope has provided astronomers with the most detailed image ever taken of the gravitational lens G2237 + 0305 – sometimes referred to as the "Einstein Cross." The photograph shows four images of a very distant quasar which has been multiple-imaged by a relatively nearby galaxy acting as a gravitational lens. The angular separation between the upper and lower images is 1.6 arcseconds.
The quasar seen here is at a distance of approximately 8 billion light-years, whereas the galaxy at a distance of 400 million light years is 20 times closer. The light from the quasar is bent in its path by the gravitational field of the galaxy. This bending has produced the four bright outer images seen in the photograph. The bright central region of the galaxy is seen as the diffuse central object.
Gravitational lensing occurs when the light from a distant source passes through or close to a massive foreground object. Depending on the detailed alignment of the foreground and background objects with the line of sight to Earth, several images of the background object may be seen. In fact, astronomers expect that a faint fifth image of the quasar should be present near the center of the galaxy in G2237 + 0305. Careful image processing will be needed to determine if the fifth image is actually seen in this FOC exposure.
Gravitational lenses, such as G2237 + 0305, are useful probes of many types of phenomena that occur in the cosmos. For example, it is possible to "weigh" the foreground galaxy by measuring the relative positions and the brightnesses of the different images of the quasar. This should be possible to do more accurately given the resolution of images obtained with the Faint Object Camera. Also, gravitational lenses in general offer the possibility of determining the elusive "Hubble Constant" – a fundamental measure of the size and age of the universe – by measuring the time delays in changes of the brightness of the lensed images.
Detailed analysis of this fascinating Faint Object Camera image and others to be observed later with the Hubble Space Telescope will provide a wealth of information on the details of lensing galaxies, as well as on the process of gravitational lensing itself.
Credits
NASA, ESA, and STScI| About The Object | |
|---|---|
| Object Name | G2237 + 0305, Einstein Cross |
| R.A. Position | 22h 40m 30.29s |
| Dec. Position | 03° 21' 30.99" |
| 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. |
