Hubble Heritage Archive

Hubble Heritage Archive - 2003

Hubble Heritage Archive: 1998 | 1999 | 2000 | 2001 | 2002 | 2003 | 2004 | 2005 | 2006

Gemini | Apollo | Hubble Space Telescope

February's Hubble Heritage image is of M27, more popularly known as the Dumbell Nebula and also designated NGC 6853. 1240 light-years from us, the Dumbell Nebula lies in the constellation Valpecula; this image covers approximately 2.1 arcminutes across (0.8 light-years). The image was originally taken on November 19, 2001 in a 2.4 hour exposure.

A planetary nebula, M27 actually represents the first such nebula discovered; it was first spied by Charles Messier in 1764.

The many knots that can be seen in the image are many times the size of Pluto's orbit and they contain as much as three times Earth's mass. These were formed by the interaction between hot and cool parts of the nebula, with the hot area moving outwards as the nebula continues to expand.

NGC 1705 - Irregular Dwarf Galaxy March's Hubble Heritage image is of NGC 1705, an irregular dwarf galaxy. 16.6 million light-years from us, NGC 1705 lies in the constellation Pictor; this image covers approximately 33 arcseconds across (2,600 light-years). The image was originally taken in March 1999 and November 2000 for a total exposure time of 18 hours.

At such a far distance, the individual stars in this galaxy can only be resolved by the Hubble Space Telescope. These stars represent an ideal situation to study star formation history, for there are young, hot, blue stars near the center, while older, cooler, red stars are more evenly spread. A recent burst of star formation between 26-31 million years ago triggered the formation of the blue stars as well as the central giant star cluster.

This galaxy is called an irregular dwarf because it is small and lacks any regular structure. Many galactic astronomers believe that such dwarfs were some of the first galaxies to form in the early universe, and they are the building blocks from which larger galaxies such as the Milky Way were later formed.

April's Hubble Heritage image is of CRL 2688, AKA the Egg Nebula, a planetary nebula. 3,000 light-years from us, the Egg Nebula lies in the constellation Cygnus; this image covers approximately 86 arcseconds across (1.2 light-years). The image was originally taken on September 27, 2002 and October 15/16, 2002 for a total exposure time of 1.5 hours.

The Egg Nebula offers astronomers a look at the usually invisible dust shells that surround aging stars. The layers extend approximately 0.1 light-years from the star (6300 times Earth's orbital distance from the sun).

The layers have an onion-like structure that forms concentric rings around the star. A thicker dust belt that runs almost vertically through the center of the image blocks light from the central star. Twin beams of light radiate from the hidden star and illuminate the normally dark dust.

The Hubble Space Telescope's Advanced Camera for Surveys has filters that allow light that vibrates only at certain angles to enter. This is a composite image of three different polarizations, one colored red, another green, and the final blue. The artificial colors in the image are used to determine how the light reflects off the smoke-size particles and then journeys to Earth.

Studying the polarized light from the Egg Nebula allows scientists to learn a lot about the physical properties of the material responsible for the scattering, as well as the location of the central, hidden, star. The dust is largely carbon, manufactured by fusion in the core of the star and then ejected into space as the star sheds material. Such dust is essential for building dusty disks around future generations of young stars, and possibly the formation of planets around those stars.

NGC 1275 - Active Galaxy May's Hubble Heritage image is of NGC 1275, AKA Perseus A, an active galaxy. 235 million light-years from us, NGC 1275lies in the constellation Perseus; this image covers approximately 0.8 arcminutes across (57,000 light-years). The image was originally taken November 16, 1995, and November 6 and 15, 2001, for a total exposure time of 4 hours.

The picture shows a large, dusty spiral galaxy that is rotating on edge - like a pinwheel - as it slides through the larger, brighter galaxy NGC 1275. The image montage show traces of spiral structure accompanied by vivid dust lanes and bright blue regions that mark areas of active star formation.

Detailed observations of NGC 1275 indicate that the dusty material belongs to a spiral system seen nearly edge-on in the foreground. The second galaxy, lying behind the first, is a giant elliptical with very faint spiral structure in its nucleus. The two galaxies are believed to be colliding at speeds greater than 9.6 million kph (6 million miles per hour). The two galaxies are in a large cluster known as the Perseus Cluster.

NGC 1275 is a powerful x-ray and radio source. The galactic collision causes the gas and dust already existing in the central bright galaxy to swirl into the center of the object. The x-ray and radio emission indicates the probably existence of a black hole in the bright galaxy's center.

As the dark, dusty material falls inward, NGC 1275 shows intricate filamentary structures at a much larger scale that is outside the range of this image. This is a typical feature of bright cluster galaxies. Additional observations show strong interactions between at least two galaxies, and possibly a few smaller ones, and includes the formation of new stars and large star clusters. Although the clusters are similar in shape to the Milky Way's they are much younger than the Milky Way's ancient (11.3+ billion years) ones.

June's Hubble Heritage image is of NGC 2736, AKA the Pencil Nebula, a supernova remnant that is part of the larger Vela Nebula. 825 light-years from us, the Pencil Nebula lies in the constellation Vela; this image covers approximately 3.3 arcminutes across (0.78 light-years). The image was originally taken October 21, 2002, for a total exposure time of 3 hours.

The Pencil Nebula was discovered in the 1840's by Sir John Herschel, and its linear appearance gave rise to its popular name. It's shape suggests that the still-expanding shock wave (from right to left in the image) that spawned the Vela Nebula has run into a dense concentration of gas, the interaction causing the glow. This view is of the edge of a rippling sheet of gas.

The impact of the shock wave with the dense interstellar medium causes the gas to heat to millions of Kelvins. As the gas then cools, it emits radiation in the optical wavelengths which is what the Hubble Space Telescope has recorded. In this image, the color of the gas indicates the relative temperature (blue is hotter, red is cooler).

The original supernova left a pulsar in the core of the Vela nebula. Based upon the current rate at which the pulsar's spin is slowing, astronomers estimate that the supernova may have occurred about 11,000 years ago. No historical records of this event exist, but if the age is accurate, the explosion would have been 250 times brighter than Venus and would have been easily visible to southern observers in broad daylight. This would also mean that the explosion pushed material from the star at about 35 million km per hour (22 million mph). The expanding gas is slowing down; the Pencil Nebula is currently moving at about 640,000 kmph (400,000 mph).

LMC N 49 - DEM L 190 - Supernova Remnant July's Hubble Heritage image is of LMC N 49, AKA DEM L 190, a supernova remnant. 160,000 light-years from us, the LMC N 49 lies in the constellation Dorado; this image covers approximately 1.9 arcminutes across (0.91 light-years). The image was originally taken November 14, 1998, April 27, 1999, and July 14, 2000, for a total exposure time of 3.1 hours.

The wisps that form this celestial object resembling many colors of cotton candy are the remains of a supernova that erupted thousands of years ago in the small, neighboring galaxy the Large Magellanic Cloud (LMC). The debris will eventually be recycled into other stars.

Besides the filaments and streamers that make up this nebula, there exists a very powerful pulsar within the nebula that may be the remnant from the initial explosion. The pulsar frequency is 1/8 Hz, pulsing once every eight seconds. This pulsar is also classified as a "magnetar" due to its very strong magnetic field - 10¹⁵ times stronger than Earth's.

This pulsar is also responsible for a historic gamma-ray burst that occurred on March 5, 1979, and was detected by several satellites. Since then, N 49 has had several subsequent gamma-ray emissions, and is now recognized as a "soft gamma-ray repeater," releasing lower-energy gamma-rays than most gamma-ray bursters.

Today, N 49 is the target of investigations led by Hubble astronomers You-Hua Chu from the University of Illinois at Urbana-Champaign and Rosa Williams from the University of Massachusetts. Members of this science team are interested in understanding whether small cloudlets in the interstellar medium of the LMC may have a marked effect on the physical structure and evolution of this supernova remnant.

This image of N 49 is a color representation of data taken in July 2000, with Hubble's Wide Field Planetary Camera 2. Color filters were used to sample light emitted by sulfur ([S II]), oxygen ([O III]), and hydrogen (H-α). The color image has been superimposed on a black and white image of stars in the same field also taken with the HST.

August's Hubble Heritage image is of NGC 6397, a globular cluster. 8200 light-years from us, NGC 6397 lies in the constellation Ara; this image covers approximately 2 arcminutes across (3.8 light-years). The image was originally taken March 6-7, 1996, April 3-4, 1999, and November 4, 2001, for a total exposure time of 7 hours.

In this, one of the nearest globular clusters, the stellar density is about a million times larger than our local volume of space; the stars are a few light-weeks apart, whereas the closest star to the sun is over four light-years away. Estimated to be over 12 billion years, old, thousands of stellar collisions have occurred in the cluster's lifetime.

The purpose of the images that were composited to make this vista was to study what is left behind from the star collisions - the "blue stragglers." Blue stragglers are so-called because of their bright blue color, which is normally characteristic of very young stars. However, due to the enormous age of the cluster, the cluster should have stopped making stars long ago, so there should not be any blue stars. Hence the term "straggler."

These can be theoretically formed in one of two ways. First, two stars collide. Their combined mass and the convection caused by the collision results in a larger star that glows hot enough to be blue. The second way is that if there is a near-miss, some material may be transferred from one of the stars to the other, and the result will be the same as in the previous model. If the two stars do not collide but end up forming a binary system, a cataclysmic variable star could result. The program was specifically looking for the cataclysmic variable stars.

To search for these, 55 images were taken over a period of about 20 hours. Most were taken in ultraviolet (UV) and blue filters, but some were in green and infrared (IR). Comparing the brightness of all the stars in the images, the astronomers were able to identify several cataclysmic variable stars in the cluster. A few of them are visible in the Hubble Heritage image as faint blue or violet stars.

An unexpected result is from three faint blue stars near the center of the cluster (turquoise in the image). These don't vary in brightness, and they are not cataclysmic variables. They may be very low-mass white dwarfs, formed in the cores of giant stars whose evolution was interrupted before a full-fledged white dwarf was formed. Such an interruption could occur as the result of a collision or interaction. When the giant star interacts with another star, it can lose its outer layers, exposing its hot, blue core. The end result will be a white dwarf of a smaller mass than would have otherwise evolved.

A large number of normal white dwarfs were also identified and studied. These stars appear throughout the cluster since they form through normal stellar evolution processes and don't involve any stellar interactions, which occur predominantly near the cluster center. Nearly 100 such burned-out stars were identified in these images, the brightest of which can be seen here as faint blue stars.

NGC 3370 - Spiral Galaxy September's Hubble Heritage image is of NGC 3370, a spiral galaxy. 8200 light-years from us, NGC 3370 lies in the constellation Leo; this image covers approximately 3.4 arcminutes across (98,000,000 light-years). The image was originally taken in April and May of 2003, for a total exposure time of 25 hours.

Nearly ten years ago, this galaxy hosted a bright exploding star. In November of 1994, the supernova's light reached Earth, briefly outshining the billions of other stars in this galaxy.

Supernovae are common, occurring once every few seconds somewhere in the universe, but this one was special. Named SN 1994ae, it was one of the nearest and best observed since the advent of modern, digital detectors. It also is a type Ia supernova, meaning that astronomers have a standard model for how they occur, and thus how bright they really are, so the distances to them can be accurately determined.

The more type Ia supernovae that are observed, the more the extragalactic distance scale can be refined. The importance of nearby supernovae is to correctly calibrate the scale with a closer measurement stick - cepheid variable stars. Cepheid variables are used to determine distances to more nearby objects than supernovae because cepheids are far dimmer than the stellar explosions. However, if one can observe both cepheids and a type Ia supernova in the same galaxy, then the two scales can be tested and calibrated.

That is where the Hubble Space Telescope comes into play. Its new Advanced Camera for Surveys has the ability to resolve individual cepheids within NGC 3370. Observed twelve times over a month, many of these stars have been found in the galaxy - the most distant cepheids yet observed.

October's Hubble Heritage image is of M104, AKA the Sombrero Galaxy, AKA NGC 4594, a spiral galaxy. 28 million light-years from us, M104 lies in the constellation Virgo; this image covers approximately 10 arcminutes across (82,000 light-years). The image was originally taken in May and June of 2003, for a total exposure time of 10.2 hours.

One of the most famous and photogenic galaxies in the universe, the Sombrero is characterized by a giant blue-white core encircled by a large swath of gas. The galaxy is actually a spiral, like our own Milky Way, but it is tilted approximately 6° south of its equatorial plane. Within the bright core is a smaller disk, tilted relative to the larger disk. X-ray emissions suggest that there is material there feeding a black hole weighing approximately 1 billion times our sun.

The galaxy is just beyond naked-eye visibility, and it is easily seen through small telescopes. It is at the southern edge of the Virgo cluster and is one of the most massive objects in the group, weighing in at about 800 billion suns. The galaxy is only half as large as ours at about 50,000 light-years across.

Plainly visible even in this shrunk view of the galaxy are many of the globular clusters that belong to the Sombrero. Its globular cluster family is estimated at nearly 2000, compared with the approximate 150 known to belong to the Milky Way.

In the 19^th century, some astronomers speculated that M104 was simply an edge-on disk of luminous gas surrounding a young star, which is prototypical of the genesis of our solar system. But in 1912, astronomer V. M. Slipher discovered that the hat-like object appeared to be rushing away from us at 700 miles per second. This enormous velocity offered some of the earliest clues that the Sombrero was really another galaxy, and that the universe was expanding in all directions.

The Hubble Heritage Team took these observations with the HST's Advanced Camera for Surveys. Images were taken in three filters (red, green, and blue) to yield a natural color image. The team took six pictures of the galaxy and then stitched them together to create the final composite image. One of the largest Hubble mosaics ever assembled, this magnificent galaxy is nearly one-fifth the diameter of the full moon.

Carina Nebula - NGC 3372 November's Hubble Heritage image of the Carina Nebula, AKA NGC 3372. 8,000 light-years from us, the Carina Nebula lies in the constellation Carina; this image covers approximately 1.2 arcminutes across (2.9 light-years). The image was originally taken On July 4/5, 2003, for a total exposure time of 1.6 hours.

The full expanse of the Carina Nebula is over 200 light-years - nearly 67 times the small portion shown in this month's release. The nebula - in the Southern hemisphere - is so large that it is visible with the naked eye.

The nebula is full of stars that emit high-speed winds. These energetic winds act to sculpt the the nebula into the billows, curls, and dark lanes that are seen in this image. This particular vista shows a region in the nebula between two large clusters of some of the most massive and hottest known stars, including the variable star known as Eta Carinae.

The filaments shown throughout the image are caused by turbulence in the gas, which in turn was caused by several stars shedding their outer layers. The cold interstellar gas mixed with the hot gas, leaving a veil of denser, opaque material in the foreground. The chemical elements in the surroundings create a potential reservoir for star formation. Areas in the brightest parts of the image at the top show elephant-trunk shaped dust clouds that may form into young solar systems in the future.

This image was taken as part of a parallel observing program. The HST has many instruments that can be used to look at slightly different portions of the sky at once. For this image, the Space Telescope Imaging Spectrograph was used to study Eta Carinae itself, while the Wide Field Planetary Camera 2 was used to image the nebula. The parallel observing program increases efficiency and allows astronomer to view objects that otherwise would not have been accepted by a selection committee.

December's Hubble Heritage image of a star-forming region in the spiral galaxy M33, NGC 604. 2.7 million light-years from us, NGC 604 lies in the constellation Triangulum; this image covers approximately 2 arcminutes across (1500 light-years). The image was originally taken in July 1994, January 1995, and December 2001, for a total exposure time of 4 hours.

NGC 604 is one of the largest known regions of star birth in a nearby galaxy. It is similar to those in the Milky Way, such as the Orion Nebula, but it is much larger and contains many more recently formed stars.

Over 200 bright blue stars reside in this 1300 light-year across cloud - 100 times the size of the Orion Nebula which contains 4 bright blue stars. The stars in NGC 604 formed approximately 3 million years ago. Most of the hottest and brightest of the stars are in a loose cluster within a cavity near the center of the nebula. Stellar winds and supernova explosions helped to form the cavity.

The most massive stars in the region are over 120 times the sun's mass and posseses surface temperatures as high as 40,000 K (72,000 °F). Ultraviolet radiation from the stars makes the surrounding gas fluoresce.

NGC 604 resides in a spiral arm of M33, which is a member of the Local Group that includes the Milky Way and Andromeda Galaxies.