One of the deepest images of the sky taken to date with NASA's Hubble Space Telescope reveals a population of faint blue galaxies which turn out to be the most common class of objects in the universe. Their distances are estimated to range from three to eight billion light-years, meaning that they were abundant when the universe was a fraction of its present age, but are rare or harder to find today because they have faded or self-destructed. This picture, in combination with a series of images from the Hubble Space Telescope Medium Deep Survey that covers a larger area of sky, is allowing astronomers to solve the longstanding "faint blue galaxy mystery" by showing the true nature of these dim and remote objects. Deciphering the formation and evolution of these blue dwarf galaxies may provide new clues to understanding the process of galaxy evolution, including the formation of our Milky Way Galaxy. Hubble's high resolution shows that most of these faint galaxies do not resemble elliptical and well-defined spiral galaxies that are common in the present universe. Instead, they have a wide variety of shapes suggesting that galaxy collisions and other interactions were more common in the past. The galaxies are blue because they are undergoing episodes of intense star-formation which produce a lot of young, hot, and blue stars. This picture is a true-color image made from separate exposures taken in blue, green, and far-red light with the Wide Field and Planetary Camera 2. It required a total of 48 orbits around the Earth (amounting to roughly one day of exposure time) to make the observation and detect objects about four billion times fainter than the unaided eye can see (30th magnitude). The image resolution is about 0.06 arc seconds. The image covers a relatively small area of sky - only one tenth the diameter of the full moon - in the constellation Hercules.
Credits
Credit: Rogier Windhorst and Simon Driver (Arizona State University), Bill Keel (University of Alabama), and NASA| About The Object | |
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| Object Name | HDF-N |
| 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 |
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| 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. |
