Deep Space


Celestial Coordinates

Stellar Distance

Light from Distant Stars

Weird Stuff in Space



Planetary systems

Planetary Nebula

Globular Clusters

Novas and Supernovas


Black Holes

Deepest Space

Stellar Evolution



Celestial Coordinates

Motions of the earth around the sun

Circle around the campfire

Right Ascension and Declination

Like latitude and longitude on earth

The division of space: Constellations

Early astronomers organized the sky into definable regions

Came up with a "shape" in each to tell them apart

Many were gods and mythical creatures

Didn't cover ALL of space

Recent workers have filled in the gaps (retaining the classical designations)

88 in total


Stellar Distance

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Light from Distant Stars

We get information from several electromagnetic sources

Visible light is only one of them

(Redshift: Photo Gallery: Stars: Electromagnetic Spectrum)

Different wavelengths indicate different energies

In general, the shorter the wavelength the greater the energy of the photon

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Weird stuff in space

Click here for an index to Hubble Space Telescope images arranged by subject

Click here for an index to The Best of Hubble Space Telescope



Snapshots in time

This sequence of NASA Hubble Space Telescope (HST) images of remote galaxies offers tantalizing initial clues to the evolution of galaxies in the universe.

[far left column] These are traditional spiral and elliptical-shaped galaxies that make up the two basic classes of island star cities that inhabit the universe we see in our current epoch (14 billion years after the birth of the universe in the Big Bang). Elliptical galaxies contain older stars, while spirals have vigorous ongoing star formation in their dusty, pancake-shaped disks. Our Milky Way galaxy is a typical spiral, or disk-shaped galaxy, on the periphery of the great Virgo cluster. Both galaxies in this column are a few tens of millions of light-years away, and therefore represent our current stage of the universe's evolution.

[center left column] These galaxies existed in a rich cluster when the universe was approximately two-thirds its present age. Elliptical galaxies (top) appear fully evolved because they resemble today's descendants. By contrast, some spirals have a frothier appearance, with loosely shaped arms of young star formation. The spiral population appears more disrupted due to a variety of possible dynamical effects that result from dwelling in a dense cluster.

[center right column] Distinctive spiral structure appears more vague and disrupted in galaxies that existed when the universe was nearly one-third its present age. These objects do not have the symmetry of current day spirals and contain irregular lumps of starburst activity. However, even this far back toward the beginning of time, the elliptical galaxy (top) is still clearly recognizable. However, the distinction between ellipticals and spirals grows less certain with increasing distance.

[far right column] These extremely remote, primeval objects existed with the universe was nearly one-tenth its current age. The distinction between spiral and elliptical galaxies may well disappear at this early epoch. However, the object in the top frame has the light profile of a mature elliptical galaxy. This implies that ellipticals formed remarkably early in the universe while spiral galaxies took much longer to form.

Magellanic Clouds (Redshift: Photo Gallery: Magellanic Clouds)

Two small, irregular galaxies

Companions to the Milky Way

Large Magellanic Cloud (169,000 light years away)

Small Magellanic Cloud (210,000 light years away)

Spiral galaxies (Redshift: Photo Gallery: Spiral Galaxies)

Color Image of the Spiral Galaxy M100

The galaxy M100 is one of the brightest members of the Virgo Cluster of galaxies. The galaxy is in the spring constellation Coma Berenices and can be seen through a moderate-sized amateur telescope. M100 is spiral shaped, like our Milky Way, and tilted nearly face-on as seen from earth. The galaxy has two prominent arms of bright stars and several fainter arms. Though the galaxy is estimated to be tens of millions of light-years away, Hubble reveals the sort of detail only seen previously (with ground based telescopes) in neighboring galaxies that are ten times closer.

This comparison image of the core of the galaxy M100 shows the dramatic improvement in Hubble Space Telescope's view of the universe. The new image was taken with the second generation Wide Field and Planetary Camera (WFPC-2) which was installed during the STS-61 Hubble Servicing Mission. The picture beautifully demonstrates that the corrective optics incorporated within the WFPC-2 compensate fully for optical aberration in Hubble's primary mirror.

Barred Spiral galaxies (Redshift: Photo Gallery: Barred Spiral Galaxies)

Barred Spiral Galaxy NGC 1365

Elliptical galaxies (Redshift: Photo Gallery: Elliptical Galaxies)

Seem to be older galaxies (most stars older than 10 billion years)

Most light from Red Giants

Seyfert (Redshift: Photo Gallery: Seyfert Galaxies)

Bright nucleus with relatively indistinct arms

Galactic Clusters (Redshift: Photo Gallery: Clusters of Galaxies)

Interacting and otherwise peculiar types (Redshift: Photo Gallery: Peculiar Galaxies)

See also (Redshift: Photo Gallery: Galaxies)

Hubble Reveals Stellar Fireworks Accompanying Galaxy Collision

This Hubble Space Telescope image provides a detailed look at a brilliant "fireworks show" at the center of a collision between two galaxies. Hubble has uncovered over 1,000 bright, young star clusters bursting to life as a result of the head-on wreck.

Left: A ground-based telescopic view of the Antennae galaxies (known formally as NGC 4038/4039) - so named because a pair of long tails of luminous matter, formed by the gravitational tidal forces of their encounter, resembles an insect's antennae. The galaxies are located 63 million light-years away in the southern constellation Corvus.

Right: The respective cores of the twin galaxies are the orange blobs, left and right of image center, crisscrossed by filaments of dark dust. A wide band of chaotic dust, called the overlap region, stretches between the cores of the two galaxies. The sweeping spiral-like patterns, traced by bright blue star clusters, shows the result of a firestorm of star birth activity which was triggered by the collision.

This natural-color image is a composite of four separately filtered images taken with the Wide Field Planetary Camera 2 (WFPC2), on January 20, 1996. Resolution is 15 light-years per pixel (picture element).

Irregular and peculiar galaxies

This is a NASA Hubble Space Telescope image of a variety of galaxies with irregular and peculiar shapes. These galaxies are so far away that they are seen when the universe was a fraction of its current age. The bright blue regions indicate a rapid episode of star formation. Hubble reveals that these objects once far outnumbered large galaxies like our Milky Way, but have faded or self-destructed by today.

The survey is one of the key projects for Hubble. Over the past three years the deep survey has uncovered a bizarre variety of shapes and structures in distant galaxies, which previously appeared as fuzzy blobs from ground-based telescopes.


(Redshift: Photo Gallery: Gaseous Nebulae)

Pillars of Creation (Star-Birth Clouds in M16)

These structures are columns of cool molecular hydrogen gas (two atoms of hydrogen in each molecule) and dust that are incubators for new stars. The stars are embedded inside finger-like protrusions extending from the top of the nebula. Each "fingertip" is somewhat larger than our own solar system.

The pillars are slowly eroding away by the ultraviolet light from nearby hot stars, a process called "photoevaporation". As they do, small globules of especially dense gas buried within the clouds are uncovered. These globules have been dubbed "EGGs" -- an acronym for "Evaporating Gaseous Globules". The shadows of the EGGs protect gas behind them, resulting in the finger-like structures at the tops of the clouds.

Forming inside at least some of the EGGs are embryonic stars -- stars that abruptly stop growing when the EGGs are uncovered and they are separated from the larger reservoir of gas from which they were drawing mass. Eventually the stars emerge, as the EGGs themselves succumb to photoevaporation.

The stellar EGGS are found, appropriately enough, in the "Eagle Nebula" (also called M16 - the 16th object in Charles Messier's 18th century catalog of "fuzzy" permanent objects in the sky), a nearby star-forming region 7,000 light-years away in the constellation Serpens.

The Orion Nebula M42

Hubble Space Telescope observing time was devoted to making this panorama because the nebula is a vast laboratory for studying the processes which gave birth to our own Sun and solar system 4.5 billion years ago. Many of the nebula's details can't be captured in a single picture - any more than one snapshot of the Grand Canyon yields clues to its formation and history. Like the Grand Canyon, the Orion nebula has a dramatic surface topography -- of glowing gasses instead of rock -- with peaks, valleys and walls. They are illuminated and heated by a torrent of energetic ultraviolet light from its four hottest and most massive stars, called the Trapezium, which lie near the center of the image.

In addition to the Trapezium, this stellar cavern contains 700 hundred other young stars at various stages of formation. High-speed jets of hot gas spewed by some of the infant stars send supersonic shock waves tearing into the nebula at 100,000 miles per hour. These shock waves appear as thin curved loops, sometimes with bright knots on their end (the brightest examples are near the bright star at the lower left).

The mosaic reveals at least 153 glowing protoplanetary disks (first discovered with the Hubble in 1992, and dubbed "proplyds") that are believed to be embryonic solar systems that will eventually form planets. (Our solar system has long been considered the relic of just such a disk that formed around the newborn Sun). The abundance of such objects in the Orion nebula strengthens the argument that planet formation is a common occurrence in the universe. The proplyds that are closest to the Trapezium stars (image center) are shedding some of their gas and dust. The pressure of starlight from the hottest stars forms "tails" which act like wind vanes pointing away from the Trapezium. These tails result from the light from the star pushing the dust and gas away from the outside layers of the proplyds. In addition to the luminescent proplyds, seven disks are silhouetted against the bright background of the nebula. These dark objects allow Hubble astronomers to estimate the masses of the disks as at least 0.1 to 730 times the mass of our Earth.

Located 1,500 light-years away, along our spiral arm of the Milky Way, the Orion nebula is located in the middle of the sword region of the constellation Orion the Hunter, which dominates the early winter evening sky, at northern latitudes. The stars have formed from collapsing clouds of interstellar gas within the last million years. The most massive clouds have formed the brightest stars near the center and these are so hot that they illuminate the gas left behind after the period of star formation was complete. The more numerous faint stars are still in the process of collapsing under their own gravity, but have become hot enough in their centers to be self luminous bodies.

The Cat's Eye Nebula NGC 6543

Planetary systems

(Redshift: Photo Gallery: Planetary Nebulae)

Hard to see protoplanetary systems from earth

Planetary Nebula

The term "Planetary Nebula" is confusing

The process has nothing to do with planet formation, which is predicted to happen early in a star's life.

Actually relates to dying stars, which create these cocoons when they lose outer layers of gas.

Planetary Nebula NGC 7027

This NASA Hubble Space Telescope image of planetary nebula NGC 7027 shows remarkable new details of the process by which a star like the Sun dies.

New features include: faint, blue, concentric shells surrounding the nebula; an extensive network of red dust clouds throughout the bright inner region; and the hot central white dwarf, visible as a white dot at the center.

The nebula is a record of the star's final death throes. Initially the ejection of the star's outer layers, when it was at its red giant stage of evolution, occurred at a low rate and was spherical. The Hubble photo reveals that the initial ejections occurred episodically to produce the concentric shells. This culminated in a vigorous ejection of all of the remaining outer layers, which produced the bright inner regions. At this later stage the ejection was non-spherical, and dense clouds of dust condensed from the ejected material.

The photograph was taken as part of a survey of planetary nebulae, which are clouds of gas and dust ejected from a star with a mass similar to that of the Sun as it reaches the end of its life. NGC 7027 is located about 3,000 light-years from Earth in the direction of the summer constellation Cygnus.

When a star like the Sun nears the end of its life, it expands to more than 50 times its original diameter, becoming a red giant star. Then its outer layers are ejected into space, exposing the small, extremely hot core of the star, which cools off to become a white dwarf. Although stars like the Sun can live for up to 10 billion years before becoming a red giant and ejecting a nebula, the actual ejection process takes only a few thousand years.


This NASA Hubble Space Telescope image shows one of the most complex planetary nebulae ever seen, NGC 6543, nicknamed the "Cat's Eye Nebula." Hubble reveals surprisingly intricate structures including concentric gas shells, jets of high-speed gas and unusual shock-induced knots of gas. Estimated to be 1,000 years old, the nebula is a visual "fossil record" of the dynamics and late evolution of a dying star.

A preliminary interpretation suggests that the star might be a double-star system. The dynamical effects of two stars orbiting one another most easily explains the intricate structures, which are much more complicated than features seen in most planetary nebulae. (The two stars are too close together to be individually resolved by Hubble, and instead, appear as a single point of light at the center of the nebula.)

According to this model, a fast "stellar wind" of gas blown off the central star created the elongated shell of dense, glowing gas. This structure is embedded inside two larger lobes of gas blown off the star at an earlier phase. These lobes are "pinched" by a ring of denser gas, presumably ejected along the orbital plane of the binary companion.

The suspected companion star also might be responsible for a pair of high- speed jets of gas that lie at right angles to this equatorial ring. If the companion were pulling in material from a neighboring star, jets escaping along the companion's rotation axis could be produced.

These jets would explain several puzzling features along the periphery of the gas lobes. Like a stream of water hitting a sand pile, the jets compress gas ahead of them, creating the "curlicue" features and bright arcs near the outer edge of the lobes. The twin jets are now pointing in different directions than these features. This suggests the jets are wobbling, or precessing, and turning on and off episodically.

This color picture, taken with the Wide Field Planetary Camera-2, is a composite of three images taken at different wavelengths. (red, hydrogen-alpha; blue, neutral oxygen, 6300 angstroms; green, ionized nitrogen, 6584 angstroms). The image was taken on September 18, 1994. NGC 6543 is 3,000 light-years away in the northern constellation Draco.

The term planetary nebula is a misnomer; dying stars create these cocoons when they lose outer layers of gas. The process has nothing to do with planet formation, which is predicted to happen early in a star's life.

Globular Clusters

(Redshift: Photo Gallery: Globular Clusters)

Densely packed clusters of stars

Hundreds of thousands to millions of stars

Not much stuff heavier than helium

Must be VERY old (10 to 15 billion years)

Novas and Supernovas

(Redshift: Photo Gallery: Supernovae)

Centaurus A galaxy (1986): 13 million light years away

(Redshift: Photo Gallery: Supernovae: <last frame>)

Supernova Blast Begins Taking Shape

This Hubble Space Telescope picture shows Supernova 1987A and its neighborhood. The series of four panels shows the evolution of the SN 1987A debris from February 1994 to February 1996. Material from the stellar interior was ejected into space during the supernova explosion in February 1987. The explosion debris is expanding at nearly 6 million miles per hour.


(Redshift: Photo Gallery: Quasars)

Name given to "quasi-stellar objects"

Emit radio waves

Very large redshift

Some of the most distant objects (some more than 10 billion light years)

Black Holes

Massive Black Holes Dwell In Most Galaxies, According To Hubble Census

The three galaxies above are believed to contain central, supermassive black holes. The galaxy NGC 4486B (lower-left) shows a double nucleus (lower-right). The images of NGC 3377 and NGC 4486B are 2.7 arcseconds on a side, and for NGC 3379 the size is 5.4 arcseconds; the lower-right is a blow-up of the central 0.5 arcseconds of NGC 4486B.

Deepest Space

Hubble Deep Field

Several hundred never before seen galaxies are visible in this "deepest-ever" view of the universe. Besides the classical spiral and elliptical shaped galaxies, there is a bewildering variety of other galaxy shapes and colors that are important clues to understanding the evolution of the universe. Some of the galaxies may have formed less that one billion years after the Big Bang.

The HDF image covers a speck of sky 1/30th the diameter of the full Moon (about 25% of the entire HDF is shown here). This is so narrow, just a few foreground stars in our Milky Way galaxy are visible and are vastly outnumbered by the menagerie of far more distant galaxies, some nearly as faint as 30th magnitude, or nearly four billion times fainter than the limits of human vision. The field is considered representative of the typical distribution of galaxies in space because the universe, statistically, looks the same in all directions.


Stellar Evolution

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