Page 1 Page 2 Page 3

On the Origin of Gold

Where did the gold in your jewelry originate? No one is completely sure. The relative average abundance in our Solar System appears higher than can be made in the early universe, in stars, and even in typical supernova explosions.

Some astronomers have recently suggested that neutron-rich heavy elements such as gold might be most easily made in rare neutron-rich explosions such as the collision of neutron stars. Pictured above is an artist’s illustration depicting two neutron stars spiraling in toward each other, just before they collide.

Since neutron star collisions are also suggested as the origin of short duration gamma-ray bursts, it is possible that you already own a souvenir from one of the most powerful explosions in the universe.

Inside the Coma Cluster of Galaxies

Almost every object in the above photograph is a galaxy. The Coma Cluster of Galaxies pictured above is one of the densest clusters known – it contains thousands of galaxies.

Each of these galaxies houses billions of stars – just as our own Milky Way Galaxy does. Although nearby when compared to most other clusters, light from the Coma Cluster still takes hundreds of millions of years to reach us.

In fact, the Coma Cluster is so big it takes light millions of years just to go from one side to the other! The above mosaic of images of a small portion of Coma was taken in unprecedented detail by the Hubble Space Telescope to investigate how galaxies in rich clusters form and evolve. Most galaxies in Coma and other clusters are ellipticals, although some imaged here are clearly spirals.

The spiral galaxy on the upper left of the above image can also be found as one of the bluer galaxies on the upper left of this wider field image. In the background thousands of unrelated galaxies are visible far across the universe.

Eta Carinae and the Homunculus Nebula

How did the star Eta Carinae create this unusual nebula? No one knows for sure. About 165 years ago, the southern star Eta Carinae mysteriously became the second brightest star in the night sky. In 20 years, after ejecting more mass than our Sun, Eta Car unexpectedly faded.

This outburst appears to have created the Homunculus Nebula, pictured above in a composite image from the Hubble Space Telescope taken last decade. Visible in the above image center is purple-tinted light reflected from the violent star Eta Carinae itself. Surrounding this star are expanding lobes of gas laced with filaments of dark dust.

Jets bisect the lobes emanating from the central star. Surrounding these lobes are red-tinted debris captured only by its glow in a narrow band of red light. This debris is expanding most quickly of all, and includes streaming whiskers and bow shocks caused by collisions with previously existing material.

Eta Car still undergoes unexpected outbursts, and its high mass and volatility make it a candidate to explode in a spectacular supernova sometime in the next few million years.

Pickering’s Triangle from Kitt Peak

Wisps like this are all that remain visible of a Milky Way star. About 7,500 years ago that star exploded in a supernova leaving the Veil Nebula, also known as the Cygnus Loop. At the time, the expanding cloud was likely as bright as a crescent Moon, remaining visible for weeks to people living at the dawn of recorded history.

Today, the resulting supernova remnant has faded and is now visible only through a small telescope directed toward the constellation of Cygnus.

The remaining Veil Nebula is physically huge, however, and even though it lies about 1,400 light-years distant, it covers over five times the size of the full Moon. In images of the complete Veil Nebula, studious readers should be able to identify the Pickering’s Triangle component pictured above, a component named for a famous astronomer and the wisp’s approximate shape.

The above image is a mosaic from the 4-meter Mayall telescope at the Kitt Peak National Observatory located in Arizona, USA.

SN 1006 Supernova Remnant

A new star, likely the brightest supernova in recorded human history, lit up planet Earth’s sky in the year 1006 AD. The expanding debris cloud from the stellar explosion, found in the southerly constellation of Lupus, still puts on a cosmic light show across the electromagnetic spectrum.

In fact, this composite view includes X-ray data in blue from the Chandra Observatory, optical data in yellowish hues, and radio image data in red. Now known as the SN 1006 supernova remnant, the debris cloud appears to be about 60 light-years across and is understood to represent the remains of a white dwarf star.

Part of a binary star system, the compact white dwarf gradually captured material from its companion star. The buildup in mass finally triggered a thermonuclear explosion that destroyed the dwarf star. Because the distance to the supernova remnant is about 7,000 light-years, that explosion actually happened 7,000 years before the light reached Earth in 1006.

Shockwaves in the remnant accelerate particles to extreme energies and are thought to be a source of the mysterious cosmic rays.
Gas and Dust of the Lagoon Nebula

This beautiful cosmic cloud is a popular stop on telescopic tours of the constellation Sagittarius. Eighteenth century cosmic tourist Charles Messier cataloged the bright nebula as M8, while modern day astronomers recognize the Lagoon Nebula as an active stellar nursery about 5,000 light-years distant, in the direction of the center of our Milky Way Galaxy.

Striking details can be traced through this remarkable picture, processed to remove stars and hence better reveal the Lagoon’s range of filaments of glowing hydrogen gas, dark dust clouds, and the bright, turbulent hourglass region near the image center. This color composite view was recorded under dark skies near Sydney, Australia.
IC 4406: A Seemingly Square Nebula

How can a round star make a square nebula? This conundrum comes to light when studying planetary nebulae like IC 4406.

Evidence indicates that IC 4406 is likely a hollow cylinder, with its square appearance the result of our vantage point in viewing the cylinder from the side. Were IC 4406 viewed from the top, it would likely look similar to the Ring Nebula. Hot gas flows out the ends of the cylinder, while filaments of dark dust and molecular gas lace the bounding walls.

The star primarily responsible for this interstellar sculpture can be found in the planetary nebula’s center. In a few million years, the only thing left visible in IC 4406 will be a fading white dwarf star.
Open Cluster NGC 290: A Stellar Jewel Box

Jewels don’t shine this bright — only stars do. Like gems in a jewel box, though, the stars of open cluster NGC 290 glitter in a beautiful display of brightness and color. The photogenic cluster, pictured above, was captured recently by the orbiting Hubble Space Telescope.

Open clusters of stars are younger, contain few stars, and contain a much higher fraction of blue stars than do globular clusters of stars. NGC 290 lies about 200,000 light-years distant in a neighboring galaxy called the Small Cloud of Magellan (SMC).

The open cluster contains hundreds of stars and spans about 65 light years across. NGC 290 and other open clusters are good laboratories for studying how stars of different masses evolve, since all the open cluster’s stars were born at about the same time.
X-Rays from the Cat’s Eye Nebula

Haunting patterns within planetary nebula NGC 6543 readily suggest its popular moniker — the Cat’s Eye nebula. Stunning false-color optical images from the Hubble Space Telescope detailed the swirls of this glowing nebula, known to be the gaseous shroud expelled from a dying sun-like star about 3,000 light-years from Earth.

This composite picture combines the latest Hubble optical image of the Cat’s Eye with new x-ray data from the orbiting Chandra Observatory and reveals surprisingly intense x-ray emission indicating the presence of extremely hot gas. X-ray emission is shown as blue-purple hues superimposed on the nebula’s center. The nebula’s central star itself is clearly immersed in the multimillion degree, x-ray emitting gas

Other pockets of x-ray hot gas seem to be bordered by cooler gas emitting strongly at optical wavelengths, a clear indication that expanding hot gas is sculpting the visible Cat’s Eye filaments and structures. Gazing into the Cat’s Eye, astronomers see the fate of our sun, destined to enter its own planetary nebula phase of evolution … in about 5 billion years.

At the Sun’s Edge

A train trip on the Trans-Siberian railway to Novosibirsk resulted in this stunning view along the edge of the Sun recorded during the August 1st total solar eclipse. The picture is a composite of two images taken at special moments in the eclipse sequence, corresponding to the very beginning and the very end of the total eclipse phase.

Those times are known to eclipse chasers as 2nd and 3rd contact. Bright beads around the Moon’s dark silhouette are rays of sunlight shining through lunar valleys at the edge of the lunar disk. But the composite view also captures solar prominences, looping structures of hot plasma suspended in magnetic fields, extending beyond the Sun’s edge.
The Crown of the Sun

During a total solar eclipse, the Sun’s extensive outer atmosphere, or corona, is an inspirational sight. The subtle shades and shimmering features of the corona that engage the eye span a brightness range of over 10,000 to 1, making them notoriously difficult to capture in a single picture.

But this composite of 28 digital images ranging in exposure time from 1/1000 to 2 seconds comes close to revealing the crown of the Sun in all its glory.

The telescopic views were recorded near Kochenevo, Russia during the August 1 total solar eclipse and also show solar prominences extending just beyond the edge of the eclipsed sun. Remarkably, features on the dark near side of the New Moon can also be made out, illuminated by sunlight reflected from a Full Earth.
Black Hole Candidate Cygnus X-1

Is that a black hole? Quite possibly. The Cygnus X-1 binary star system contains one of the best candidates for a black hole.

he system was discovered because it is one of the brightest X-ray sources on the sky, shining so bright it was detected by the earliest rockets carrying cameras capable of seeing the previously unknown X-ray sky. The star’s very name indicates that it is the single brightest X-ray source in the constellation of the Swan Cygnus.

Data indicate that a compact object there contains about nine times the mass of the Sun and changes its brightness continually on several time scales, at least down to milliseconds. Such behavior is expected for a black hole, and difficult to explain with other models. Pictured above is an artistic impression of the Cygnus X-1 system.

On the left is the bright blue supergiant star designated HDE 226868, which is estimated as having about 30 times the mass of our Sun. Cygnus X-1 is depicted on the right, connected to its supergiant companion by a stream of gas, and surrounded by an impressive accretion disk.

The bright star in the Cygnus X-1 system is visible with a small telescope. Strangely, the Cygnus X-1 black hole candidate appears to have formed without a bright supernova explosion.
NGC 6888: The Crescent Nebula

NGC 6888, also known as the Crescent Nebula, is a cosmic bubble about 25 light-years across, blown by winds from its central, bright, massive star. This beautiful telescopic view combines a composite color image with narrow band data that isolates light from hydrogen and oxygen atoms in the wind-blown nebula.

The oxygen atoms produce the blue-green hue that seems to enshroud the detailed folds and filaments. NGC 6888’s central star is classified as a Wolf-Rayet star (WR 136). The star is shedding its outer envelope in a strong stellar wind, ejecting the equivalent of the Sun’s mass every 10,000 years.

The nebula’s complex structures are likely the result of this strong wind interacting with material ejected in an earlier phase. Burning fuel at a prodigious rate and near the end of its stellar life this star should ultimately go out with a bang in a spectacular supernova explosion. Found in the nebula rich constellation Cygnus, NGC 6888 is about 5,000 light-years away.
Perseid over Vancouver

Colorful and bright, the city lights of Vancouver, Canada are reflected in the water in this portrait of the world at night. Recorded on August 12 during the Perseid Meteor Shower, the wide-angle view takes in a large swath along the photographer’s eastern horizon.

The picture is a composite of many consecutive 2 second exposures that, when added together, cover a total time of an hour and 33 minutes. During that time, stars trailed through the night sky above Vancouver, their steady motion along concentric arcs a reflection of planet Earth’s rotation.

The dotted trails of aircraft also cut across the scene. Of course, two of the frames captured the brief, brilliant flash of a Perseid fireball as it tracked across the top of the field of view. The large gap in the single meteor trail corresponds to the time gap between the consecutive frames.
Baily’s Beads near Solar Eclipse Totality

Just before the Sun blacks out, something strange occurs. As the Moon moves to completely cover the Sun in a total solar eclipse, beads of bright sunlight stream around the edge of the Moon. This effect, known as Baily’s beads, is named after Francis Baily who called attention to the phenomenon in 1836.

Although, the number and brightness of Baily’s beads used to be unpredictable, today the Moon is so well mapped that general features regarding Baily’s beads are expected. When a single bead dominates, it is called the diamond ring effect, and is typically seen just before totality.

Pictured above, a series of images recorded Baily’s beads at times surrounding the recent total solar eclipse visible from Novosibirsk, Russia. The complete series can be seen by scrolling right. At the end of totality, as the Sun again emerges from behind the moon, Baily’s beads may again be visible — but now on the other side of the Moon.
NGC 6960: The Witch’s Broom Nebula

Ten thousand years ago, before the dawn of recorded human history, a new light must suddenly have appeared in the night sky and faded after a few weeks. Today we know this light was an exploding star and record the colorful expanding cloud as the Veil Nebula.

Pictured above is the west end of the Veil Nebula known technically as NGC 6960 but less formally as the Witch’s Broom Nebula. The expanding debris cloud gains its colors by sweeping up and exciting existing nearby gas.

The supernova remnant lies about 1400 light-years away towards the constellation of Cygnus. This Witch’s Broom actually spans over three times the angular size of the full Moon. The bright star 52 Cygni is visible with the unaided eye from a dark location but unrelated to the ancient supernova.
The Matter of the Bullet Cluster

The matter in galaxy cluster 1E 0657-56, fondly known as the “bullet cluster”, is shown in this composite image. A mere 3.4 billion light-years away, the bullet cluster’s individual galaxies are seen in the optical image data, but their total mass adds up to far less than the mass of the cluster’s two clouds of hot x-ray emitting gas shown in red.

Representing even more mass than the optical galaxies and x-ray gas combined, the blue hues show the distribution of dark matter in the cluster.

Otherwise invisible to telescopic views, the dark matter was mapped by observations of gravitational lensing of background galaxies. In a text book example of a shock front, the bullet-shaped cloud of gas at the right was distorted during the titanic collision between two galaxy clusters that created the larger bullet cluster itself. But the dark matter present has not interacted with the cluster gas except by gravity.

The clear separation of dark matter and gas clouds is considered direct evidence that dark matter exists.
47 Tuc: A Great Globular Cluster of Stars

Stars come in bunches. Of the over 200 globular star clusters that orbit the center of our Milky Way Galaxy, 47 Tucanae is the second brightest globular cluster (behind Omega Centauri). Light takes about 13,000 years to reach us from 47 Tuc which can be seen on the sky near the Small Magellanic Cloud in the southern constellation of Tucana.

Also known as NGC 104, the dense cluster is made up of several million stars in a volume only about 120 light-years across. The cluster’s red giant stars are particularly easy to see in this picture. The globular cluster is also home to exotic x-ray binary star systems.
NGC 1316: After Galaxies Collide

Astronomers turn detectives when trying to figure out the cause of startling sights like NGC 1316. Their investigation indicates that NGC 1316 is an enormous elliptical galaxy that started, about 100 million years ago, to devour a smaller spiral galaxy neighbor, NGC 1317, just above it.

Supporting evidence includes the dark dust lanes characteristic of a spiral galaxy, and faint swirls of stars and gas visible in this wide and deep image. What remains unexplained are the unusually small globular star clusters, seen as faint dots on the image. Most elliptical galaxies have more and brighter globular clusters than NGC 1316.

Yet the observed globulars are too old to have been created by the recent spiral collision. One hypothesis is that these globulars survive from an even earlier galaxy that was subsumed into NGC 1316.

Spokes in the Helix Nebula

Page 1 Page 2 Page 3