The saying "X" marks the spot holds true in this NASA Hubble Space Telescope (HST) image where Hubble-X marks the location of a dramatic burst of star formation, very much like the Orion Nebula in our Milky Way galaxy, but on a vastly greater scale.
Hubble-X is a glowing gas cloud, one of the most active star-forming regions within galaxy NGC 6822. The name Hubble-X does not refer to the shape of the gas cloud, but rather is derived from a catalog of objects in this particular galaxy. The "X" is actually a Roman numeral designation. The galaxy lies in the constellation Sagittarius at a distance of only 1,630,000 light-years and is one of the Milky Way's closest neighbors. The intense star formation in Hubble-X occurred only about 4 million years ago, a small fraction of the approximate 10 billion year age of the universe.
Giant gas clouds in NGC 6822 have held a special attraction for astronomers since their discovery by the visual observer E. E. Barnard in 1881. Edwin P. Hubble, after whom the HST is named, used the then-new 100-inch telescope at Mount Wilson Observatory in 1925 to make the first detailed photographic investigation of NGC 6822. The Hubble image reveals details too fine to be resolved from telescopes on the ground.
Stars form in groups from enormous clouds of gas and dust called giant molecular clouds. Once star formation begins in a molecular cloud, its rate accelerates until the process is stopped when one or more very massive hot stars are formed. At that point the clouds change from near darkness into the brightly glowing objects such as seen in Hubble-X. It is the intense ultraviolet radiation from the massive stars that causes the residual gas to glow. Radiation and gas outflows, called stellar winds, then cause the gas to disperse, bringing further star formation to an abrupt end.
The Hubble-X image was taken with Hubble's Wide Field Planetary Camera 2 (WFPC2) in September 1997, by astronomers C. Robert O'Dell of Vanderbilt University, Paul W. Hodge of the University of Washington, and R. C. Kennicutt, Jr. of Steward Observatory at the University of Arizona.
The image shows a nearly circular bright cloud at the core of Hubble-X. The cloud's diameter is about 110 light-years, and contains many thousands of newly formed stars in a central cluster. The brightest of these young stars are easily visible in the Hubble image, where they appear as numerous bright white dots.
Hubble-X is many times brighter and larger than the Orion Nebula, the brightest nearby star formation region in our own Milky Way galaxy. In fact, the tiny cloud just below Hubble-X, barely resolved even by HST, has about the same size and brightness as the Orion Nebula.
Credits
NASA and The Hubble Heritage Team (STScI/AURA);Acknowledgment: C. R. O'Dell (Vanderbilt University)
| About The Object | |
|---|---|
| Object Name | Hubble-X , NGC 6822 |
| Object Description | Gas Cloud in Galaxy NGC 6822 |
| R.A. Position | 19h 45m 5.4s |
| Dec. Position | -14° 43' 14.19" |
| Constellation | Sagittarius |
| Distance | About 500 kpc (1.63 million light-years) |
| Dimensions | Cloud Diameter: 110 light-years |
| About The Data | |
| Data Description | Principal Astronomers: C.R.O'Dell (Vanderbilt University), P.W. Hodge (University of Washington), R.C. Kennicutt (University of Arizona) |
| Instrument | HST>WFPC2 |
| Exposure Dates | September 7, 1997, Exposure Time: 2.6 hours |
| Filters | F487N (Hb), F502N ([OIII]), and F656N (Ha) |
| About The Image | |
| Color Info | Blue: F487N (Hb) Green: F502N ([OIII]) Red: F656N (Ha) |
| 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. |
