At first glance, the Helix Nebula (aka NGC 7293), looks simple and round. But this well-studied example of a planetary nebula, produced near the end of the life of a sun-like star, is now understood to have a surprisingly complex geometry. Its extended loops and comet-shaped features have been explored in Hubble Space Telescope images.

Still, a 16-inch diameter telescope and camera with broad and narrow band filters was used to create this sharp view of the Helix. The color composite also reveals the nebula’s intriguing details, including light-year long, bluegreen radial stripes or spokes that give it the appearance of a cosmic bicycle wheel.

The spoke features seem to indicate that the Helix Nebula is itself an old and evolved planetary nebula. The Helix is a mere seven hundred light years from Earth, in the constellation Aquarius.
A Flock of Stars

Only a few stars can be found within ten light-years of our lonely Sun, situated near an outer spiral arm of the Milky Way galaxy. But if the Sun were found within one of our galaxy’s star clusters, thousands of stars might occupy a similar space.

What would the night sky look like in such a densely packed stellar neighborhood? When Roger Hopkins took this picture at the Montezuma National Wildlife Refuge in the Finger Lakes region of western New York, USA, he was struck by this same notion.

Appropriately, he had photographed a flock of starlings against the backdrop of a serene sunset. He then manipulated the image so that the black bird silhouettes were changed to white. The final picture dramatically suggests the tantalizing spectacle of approaching night in crowded skies above a cluster star world.

M110: Satellite of the Andromeda Galaxy

Our Milky Way Galaxy is not alone. It is part of a gathering of about 25 galaxies known as the Local Group. Members include the Great Andromeda Galaxy (M31), M32, M33, the Large Magellanic Cloud, the Small Magellanic Cloud, Dwingeloo 1, several small irregular galaxies, and many dwarf elliptical and dwarf spheroidal galaxies.

Pictured on the lower right is one of the dwarf ellipticals: NGC 205. Like M32, NGC 205 is a companion to the large M31, and can sometimes be seen to the south of M31′s center in photographs. The image shows NGC 205 to be unusual for an elliptical galaxy in that it contains at least two dust clouds (at 9 and 2 o’clock – they are visible but hard to spot) and signs of recent star formation.

This galaxy is sometimes known as M110, although it was actually not part of Messier’s original catalog.
SN 1006: A Supernova Ribbon from Hubble

What created this unusual space ribbon? Most assuredly, one of the most violent explosions ever witnessed by ancient humans.

ack in the year 1006 AD, light reached Earth from a stellar explosion in the constellation of the Wolf (Lupus), creating a “guest star” in the sky that appeared brighter than Venus and lasted for over two years. The supernova, now cataloged at SN 1006, occurred about 7,000 light years away and has left a large remnant that continues to expand and fade today.

Pictured above is a small part of that expanding supernova remnant dominated by a thin and outwardly moving shock front that heats and ionizes surrounding ambient gas.

SN 1006 now has a diameter of nearly 60 light years. Within the past year, an even more powerful explosion occurred far across the universe that was visible to modern humans, without any optical aid, for a few seconds.

W5: Pillars of Star Creation

How do stars form? A study of star forming region W5 by the sun-orbiting Spitzer Space Telescope provides clear clues by recording that massive stars near the center of empty cavities are older than stars near the edges. A likely reason for this is that the older stars in the center are actually triggering the formation of the younger edge stars.

The triggered star formation occurs when hot outflowing gas compresses cooler gas into knots dense enough to gravitationally contract into stars. Spectacular pillars, left slowly evaporating from the hot outflowing gas, provide further visual clues.

In the above scientifically-colored infrared image, red indicates heated dust, while white and green indicate particularly dense gas clouds. W5 is also known as IC 1848, and together with IC 1805 form a complex region of star formation popularly dubbed the Heart and Soul Nebulas.

The above image highlights a part of W5 spanning about 2,000 light years that is rich in star forming pillars. W5 lies about 6,500 light years away toward the constellation of Cassiopeia.
MACSJ0025: Two Giant Galaxy Clusters Collide

What happens when two of the largest objects in the universe collide? No one was quite sure, but the answer is giving clues to the nature of mysterious dark matter.

In the case of MACSJ0025.4-1222, two huge clusters of galaxies have been found slowly colliding over hundreds of millions of years, and the result has been imaged by both the Hubble Space Telescope in visible light and the Chandra Space Telescope in X-ray light.

Once the above visible image was recorded, the location and gravitational lens distortions of more distant galaxies by the newly combined galaxy cluster allowed astronomers to computationally determine what happened to the clusters’ dark matter.

The result indicates that this huge collision has caused the dark matter in the clusters to become partly separated from the normal matter, confirming earlier speculation. In the above combined image, dark matter is shown as the diffuse purple hue, while a smoothed depiction of the X-ray hot normal matter is shown in pink.

MACSJ0025 contains hundreds of galaxies, spans about three million light years, and lies nearly six billion light years away (redshift 0.59) toward the constellation of Monster Whale (Cetus).
The Case of the Very Dusty Binary Star

For astronomers, close binary star system BD+20 307 originally stood out because it is extremely dusty. A substantial amount of warm dust surrounding it causes the system to appear exceptionally bright at infrared wavelengths. Of course, dust associated with planet formation is often detected around young stars, stars only a few million years old.

But the BD+20 307 system has now been found to be at least a few billion years old, an age comparable to the age of our own Solar System. The large amount of warm dust is likely the debris from a relatively recent collision of planet-sized objects on the scale of, say, Earth and Venus, in the BD+20 307 system.

Reminiscent of the classic scifi novel When Worlds Collide, the dramatic illustration offers a depiction of the catastrophic event. Ironically, this indirect evidence of a destructive planetary collision could also be the first indication that planetary systems can form around close binary stars. BD+20 307 is about 300 light-years distant toward the headstrong constellation Aries.
A True Image from False Kiva

Is there any place in the world you could see a sight like this? Yes! This digital mosaic shows the night sky as seen from False Kiva in Canyonlands National Park, eastern Utah, USA. Diving into the Earth far in the distance is part of the central band of our Milky Way Galaxy.

Much closer, the planet Jupiter is visible as the bright point just to band’s left. Closer still are the park’s picturesque buttes and mesas lit by a crescent moon.

In the foreground is the cave housing a stone circle of unknown origin named False Kiva. The cave itself was briefly lit by flashlight during the exposure. Astrophotographer Wally Pacholka reports that getting to the cave was no easy trek. Also, mountain lions were a concern while waiting alone in the dark to record the mosaic.
Young Suns of NGC 7129

Young suns still lie within dusty NGC 7129, some 3,000 light-years away toward the royal constellation Cepheus. While these stars are at a relatively tender age, only about a million years old, it is likely that our own Sun formed in a similar stellar nursery some five billion years ago.

Most noticeable in the striking image are the lovely bluish dust clouds that reflect the youthful starlight, but the smaller, deep red crescent shapes are also markers of energetic, young stellar objects. Known as Herbig-Haro objects, their shape and color is characteristic of glowing hydrogen gas shocked by jets streaming away from newborn stars.

Ultimately the natal gas and dust in the region will be dispersed, the stars drifting apart as the loose cluster orbits the center of the Galaxy. At the estimated distance of NGC 7129, this telescopic view spans about 40 light-years.
Irregular Galaxy NGC 55

Irregular galaxy NGC 55 is thought to be similar to the Large Magellanic Cloud (LMC). But while the LMC is about 180,000 light-years away and is a well known satellite of our own Milky Way Galaxy, NGC 55 is more like 6 million light-years distant and is a member of the Sculptor Galaxy Group. Classified as an irregular galaxy, in deep exposures the LMC itself resembles a barred disk galaxy.

However, spanning about 50,000 light-years, NGC 55 is seen nearly edge-on, presenting a flattened, narrow profile in contrast with our face-on view of the LMC. Just as large star forming regions create emission nebulae in the LMC, NGC 55 is also seen to be producing new stars.

This gorgeous galaxy portrait highlights a bright core, telltale pinkish emission regions, and young blue star clusters in NGC 55.
A Dark Pulsar in CTA 1

Where’s the pulsar? Previously, the nebula CTA 1 showed an expanding supernova remnant, a jet, and a point source expected to be a pulsar — a rotating neutron star producing pulses at radio energies. But no radio pulses were detected.

Now NASA’s recently deployed Fermi Space Telescope has solved the mystery with some of its initial observations indicating that the point source is pulsing at gamma-ray energies. The strange source is the first of a class that might be dubbed “dark pulsars”, rotating neutron stars that appear to pulse only in high-energy radiations.

Such pulsars might not be detectable in radio or visible light if they emit those radiations into a narrow beam not seen from Earth.

If true, our Galaxy might have more pulsars left for Fermi to discover. Studying the gamma-ray properties of pulsars gives valuable clues to physics of the emission regions on neutron stars. In this graphic, the pulsar’s position is indicated in the wider CTA 1 supernova remnant. An artist’s illustration of the pulsar beaming at gamma-ray energies is shown in the inset.
Great Orion Nebulae

The Great Nebula in Orion, also known as M42, is one of the most famous nebulae in the sky. The star forming region’s glowing gas clouds and hot young stars are on the right in this sharp and colorful two frame mosaic that includes the smaller nebula M43 near center and dusty, bluish reflection nebulae NGC 1977 and friends on the left.

Located at the edge of an otherwise invisible giant molecular cloud complex, these eye-catching nebulae represent only a small fraction of this galactic neighborhood’s wealth of interstellar material.

Within the well-studied stellar nursery, astronomers have also identified what appear to be numerous infant solar systems. The gorgeous skyscape spans nearly two degrees or about 45 light-years at the Orion Nebula’s estimated distance of 1,500 light-years.

Haunting the Cepheus Flare

Spooky shapes seem to haunt this starry expanse, drifting through the night in the royal constellation Cepheus.

Of course, the shapes are cosmic dust clouds faintly visible in dimly reflected starlight. Far from your own neighborhood on planet Earth, they lurk at the edge of the Cepheus Flare molecular cloud complex some 1,200 light-years away. Over 2 light-years across and brighter than the other ghostly apparitions, the nebula known as Sh2-136 near the center of the field is even seen in infrared light.

Also cataloged as Bok globule CB230, the core of that cloud is collapsing and is likely a binary star system in the early stages of formation.
A Spectre in the Eastern Veil

Menacing flying forms and garish colors are a mark of the Halloween season. They also stand out in this cosmic close-up of the eastern Veil Nebula.

The Veil Nebula itself is a large supernova remnant, the expanding debris cloud from the death explosion of a massive star. While the Veil is roughly circular in shape covering nearly 3 degrees on the sky in the constellation Cygnus, this portion of the eastern Veil spans only 1/2 degree, about the apparent size of the Moon. That translates to 12 light-years at the Veil’s estimated distance of 1,400 light-years from planet Earth.

In this composite of image data recorded through narrow band filters, emission from hydrogen atoms in the remnant is shown in red with strong emission from oxygen atoms in greenish hues. In the western part of the Veil lies another seasonal apparition, the Witch’s Broom.
On the Trail of 2008 TC3

On October 7, the early dawn over northern Sudan revealed this twisted, high altitude trail. Captured in a video frame, the long-lasting persistent train is from the impact of a small asteroid cataloged as 2008 TC3.

That event was remarkable because it was the first time an asteroid was detected in space before crashing into planet Earth’s atmosphere. In fact, after astronomers discovered 2008 TC3, the time and location of its impact were predicted based on follow-up observations.

Later, the impact predictions were confirmed by sensors, including a Meteosat-8 image of a bright flash in the atmosphere. Astronomers are now hoping for more reports of local ground-based observations of what must have been a brilliant meteor streaking through Sudan’s night sky. Additional reports could improve the chances of recovering meteorites.

Image/Information Credit : APOD : Astronomy Picure Of Day (NASA)

- Prashant Vikram

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