These three pictures illustrate how a nearby irregular galaxy brimming with star birth would appear at successively greater distances from Earth.
The picture at lower left shows the galaxy, I Zw 18, as it actually appears in a snapshot taken by the Hubble telescope's Wide Field and Planetary Camera 2. The galaxy resides 30 million light-years away in the constellation Ursa Major. The observation was made in November 1994 and March 1995. The bright dots scattered throughout the image represent clusters of stars.
The pictures in the middle and at upper right simulate how the galaxy would appear if it resided at faraway distances - 300 million light-years and one billion light-years, respectively. The two pictures were created by modifying the original Hubble photo of I Zw 18. The colors in all three pictures were selected to enhance important details in the galaxy.
The pictures illustrate that less of the galaxy is seen at successively greater distances from Earth because the fainter stars are no longer visible. At 300 million light-years away, the brightest stars are represented as the white blob near the galaxy's center. At 3 billion light-years away, the brightest region is a small white dot. This simulation demonstrates that astronomers may be missing most of the starlight from the farthest galaxies because it's too faint to see, even with the most powerful telescopes. The star birth they are detecting is just the "tip of the iceberg."
Credits
Archival Image: D. Hunter (Lowell Observ.) and A. Aloisi (JHU);Simulated Images: A. Fruchter and Z. Levay (STScI)
| About The Object | |
|---|---|
| Object Name | I Zw 18 |
| 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. |
