Astronomy Picture of the Day

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 September 15

SN 1006: A Supernova Ribbon from Hubble
Credit: NASA, ESA, Hubble Heritage (STScI/AURA); Acknowledgement: W. Blair et al. (JHU) Explanation: What created this unusual space ribbon? Most assuredly, one of the most violent explosions ever witnessed by ancient humans. Back 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 aide, for a few seconds.

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Tomorrow's picture: dark clusters collide

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 September 16

W5: Pillars of Star Creation
Credit: Lori Allen, Xavier Koenig (Harvard-Smithsonian CfA) et al., JPL-Caltech, NASA Explanation: 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.

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Tomorrow's picture: dark clusters collide

 

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Astronomy Picture of the Day


Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 September 17
MACSJ0025: Two Giant Galaxy Clusters Collide
Credit: NASA, ESA, CXC, M. Bradac (UCSB) & S. Allen (Stanford)
Explanation: 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).
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Tomorrow's picture: open space

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 September 18

Exploring the Ring
Credit & Copyright: Astro-Cooperation - Stefan Heutz/Wolfgang Ries Explanation: A familiar sight for northern hemisphere astronomers, the Ring Nebula (M57) is some 2,000 light-years away in the musical constellation Lyra. The central ring is about one light-year across, but this remarkably deep exposure - a collaborative effort combining data from two different telescopes - explores the looping filaments of glowing gas extending much farther from the nebula's central star. Of course, in this well-studied example of a planetary nebula, the glowing material does not come from planets. Instead, the gaseous shroud represents outer layers expelled from a dying, sun-like star. This composite image includes over 16 hours of narrow-band data intended to record the red emission from hydrogen atoms, but the pronounced blue/green color is due to emission from oxygen atoms at higher temperatures within the ring. The much more distant spiral galaxy IC 1296 is also visible at the upper right.


Tomorrow's picture: possible planet

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 September 19

Companion of a Young, Sun-like Star
Credit Gemini Observatory, D. Lafreniere, R. Jayawardhana, M. van Kerkwijk (Univ. Toronto) Explanation: Located just 500 light-years away toward the constellation Scorpius, this star is only slightly less massive and a little cooler than the Sun. But it is much younger, a few million years old compared to the middle-aged Sun's 5 billion years. This sharp infrared image shows the young star has a likely companion positioned above and left - a hot planet with about 8 times the mass of Jupiter, orbiting a whopping 330 times the Earth-Sun distance from its parent star. The young planetary companion is still hot and relatively bright in infrared light due to the heat generated during its formation by gravitational contraction. In fact, such newborn planets are easier to detect before they age and cool, becoming much fainter. Though over 300 extrasolar planets have been found using other techniques, this picture likely represents the first direct image of a planet belonging to a star similar to the Sun.


Tomorrow's picture: darkened sky

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 September 20

A Darkened Sky
Credit & Copyright: Miloslav Druckmuller (Brno University of Technology), Peter Aniol, Vojtech Rusin Explanation: For a moment on August 1st, the daytime sky grew dark along the path of a total solar eclipse. While watching the geocentric celestial event from Mongolia, photographer Miloslav Druckmuller recorded multiple images with two separate cameras as the Moon blocked the bright solar disk and darkened the sky. This final composition consists of 55 frames ranging in exposure time from 1/125 to 8 seconds. It spans nearly 12 degrees, with the relative position of the Moon and Sun corresponding to mid-eclipse. On the left is bright planet Mercury, but many stars are also visible, including the Praesepae star cluster (also known as M44 or the Beehive cluster) in Cancer, above and to the right of the silhouetted Moon. Remarkably, the nearly perfect conditions and wide range in individual exposures allow the composite picture to register the lunar surface and follow the delicate solar corona out to a distance of nearly 20 times the radius of the Sun. In fact, the composite presents a range in brightness beyond what the eye could see during the eclipse.


Tomorrow's picture: egging the equinox

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 September 22

Equinox: The Sun from Solstice to Solstice
Credit & Copyright: Tunç Tezel (TWAN) Explanation: Today is an equinox, a date when day and night are equal. Tomorrow, and every day until the next equinox, the night will be longer than the day in Earth's northern hemisphere, and the day will be longer than the night in Earth's southern hemisphere. An equinox occurs midway between the two solstices, when the days and nights are the least equal. The picture is a composite of hourly images taken of the Sun above Bursa, Turkey on key days from solstice to equinox to solstice. The bottom Sun band was taken during the winter solstice in 2007 December, when the Sun could not rise very high in the sky nor stay above the horizon very long. This lack of Sun caused winter. The top Sun band was taken during the summer solstice in 2008 June, when the Sun rose highest in the sky and stayed above the horizon for more than 12 hours. This abundance of Sun caused summer. The middle band was taken during the Vernal Equinox in 2008 March, but it is the same sun band that Earthlings will see today, the day of the Autumnal Equinox.


Tomorrow's picture: almost pluto

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 September 23

Haumea of the Outer Solar System
Illustration Credit: NASA Explanation: One of the strangest objects in the outer Solar System was classified as a dwarf planet last week and given the name Haumea. This designation makes Haumea the fifth designated dwarf planet after Pluto, Ceres, Eris, and Makemake. Haumea's smooth but oblong shape make it extremely unusual. Along one direction, Haumea is significantly longer than Pluto, while in another direction Haumea has an extent very similar to Pluto, while in the third direction is much smaller. Haumea's orbit sometimes brings it closer to the Sun than Pluto, but usually Haumea is further away. Illustrated above, an artist visualizes Haumea as a nearly featureless ellipsoid. Quite possibly, however, Haumea has interesting craters and surface features that currently remain unknown. Originally discovered in 2003 and given the temporary designation of 2003 EL61, Haumea was recently renamed by the IAU for a Hawaiian goddess. Haumea has two small moons discovered in 2005, recently renamed Hi'iaka and Namaka for daughters of the goddess.


Tomorrow's picture: open space

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 September 24

Active Region 1002 on an Unusually Quiet Sun
Credit: SOHO Consortium, EIT, ESA, NASA Explanation: Why has the Sun been so quiet recently? No one is sure. Our Sun has shown few active regions -- that house even fewer associated sunspots -- for over a year now, and such a period of relative calm is quite unusual. What is well known is that our Sun is in a transitional period between solar cycles called a Solar Minimum, where solar activity has historically been reduced. The stark lack of surface tumult is unusual even during a Solar Minimum, however, and activity this low has not been seen for many decades. A few days ago, however, a bona-fide active region -- complete with sunspots --appeared and continues to rotate across the Sun's face. Visible above, this region, dubbed Active Region 1002 (AR 1002), was imaged in ultraviolet light yesterday by the SOHO spacecraft, which co-orbits the Sun near the Earth. Besides the tranquility on the Sun's surface, recent data from the Ulysses spacecraft, across the Solar System, indicate that the intensity of the solar wind blowing out from the Sun is at a fifty year low. Predictions hold, however, that our Sun will show more and more active regions containing more and more sunspots and flares until Solar Maximum occurs in about four years.

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 September 25

The Case of the Very Dusty Binary Star
Illustration Credit & Copyright: Lynette Cook Explanation: 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.


Tomorrow's picture: Moon rays

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 September 27

M83: The Thousand-Ruby Galaxy
Color Composite: Davide De Martin (Skyfactory)
Credit: European Southern Observatory Science Archive Explanation: Big, bright, and beautiful, spiral galaxy M83 lies a mere twelve million light-years away, near the southeastern tip of the very long constellation Hydra. Prominent spiral arms traced by dark dust lanes and blue star clusters lend this galaxy its popular name of the Southern Pinwheel. But reddish star forming regions that dot the sweeping arms highlighted in this sparkling color composite also suggest another nickname, The Thousand-Ruby Galaxy. About 40,000 light-years across, M83 is a member of a group of galaxies that includes active galaxy Centaurus A. The core of M83 itself is bright at x-ray energies, showing a high concentration of neutron stars and black holes left from an intense burst of star formation. The sharp image, based on archival data from the European Southern Observatory's Wide Field Imager camera, also features spiky foreground Milky Way stars and distant background galaxies.


Tomorrow's picture: new stars

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 September 28

Young Stars of NGC 346
Credit: Antonella Nota (ESA/STScI) et al., ESA, NASA NASA Explanation: The massive stars of NGC 346 are short lived, but very energetic. The star cluster is embedded in the largest star forming region in the Small Magellanic Cloud, some 210,000 light-years distant. Their winds and radiation sweep out an interstellar cavern in the gas and dust cloud about 200 light-years across, triggering star formation and sculpting the region's dense inner edge. Cataloged as N66, the star forming region also appears to contain a large population of infant stars. A mere 3 to 5 million years old and not yet burning hydrogen in their cores,the infant stars are strewn about the embedded star cluster. In the above false-color Hubble Space Telescope image, visible and near-infrared light are seen as blue and green, while light from atomic hydrogen emission is red.


Tomorrow's picture: cave galaxy

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 September 29

A True Image from False Kiva
Credit & Copyright: Wally Pacholka (Astropics.com/TWAN) Explanation: Is there any place in the world you could see a real sight like this? Yes. Pictured above is single exposure image spectacular near, far, and in between. Diving into the Earth far in the distance is part of the central band of our Milky Way Galaxy, taken with a long duration exposure. Much closer, the planet Jupiter is visible as the bright point just to band's left. Closer still are picturesque buttes and mesas of the Canyonlands National Park in Utah, USA, lit by a crescent moon. In the foreground is a cave housing a stone circle of unknown origin named False Kiva. The cave was briefly lit by flashlight during the long exposure. Astrophotographer Wally Pacholka reports that getting to the cave to take this image was no easy trek. Also, mountain lions were a concern while waiting alone in the dark for just the right exposure.


Tomorrow's picture: open space

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 September 30

Planets Ahoy!
Credit & Copyright: Mike Salway (IceInSpace) Explanation: Can you spot the Solar System's four rocky planets? In the above image taken on September 20, all of them were visible in a single glance, but some of them may be different than you think. Pictured above, the brightest and highest object in the sky is the planet Venus. The object lowest in the sky is the planet Mars, while the object furthest to the left is the planet Mercury. The last remaining point of light is . . . the bright star Spica, which leaves the question -- where is the fourth rocky planet? That would be Earth, specifically part of Australia, visible across the entire bottom of the image.


Tomorrow's picture: NASA anniversary

 

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WASHINGTON, Sept. 29 (UPI) -- The U.S. space agency says its Phoenix Mars Lander has detected snow falling from Martian clouds, vaporizing before reaching the planet's surface.

And the National Aeronautics and Space Administration says that, plus soil test experiments, have proven evidence of past interaction between minerals and liquid water -- both processes that occur on Earth.

"A laser instrument designed to gather knowledge of how the atmosphere and surface interact on Mars detected snow from clouds about 2.5 miles above the spacecraft's landing site," NASA said, adding data shows the snow vaporizing before reaching the ground.

"Nothing like this view has ever been seen on Mars," said Jim Whiteway, of Canada's York University, the lead scientist for the Canadian-supplied Meteorological Station on Phoenix. "We'll be looking for signs that the snow may even reach the ground."

Since landing May 25, Phoenix has also confirmed a hard subsurface layer at its far-northern site contains water-ice. NASA said determining whether that ice ever thaws will help answer whether the environment there has been favorable for life, a key aim of the mission.

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 October 1

The First Rocket Launch from Cape Canaveral
Credit: GRIN, NASA Explanation: A new chapter in space flight began on 1950 July with the launch of the first rocket from Cape Canaveral, Florida: the Bumper 2. Shown above, the Bumper 2 was an ambitious two-stage rocket program that topped a V-2 missile base with a WAC Corporal rocket. The upper stage was able to reach then-record altitudes of almost 400 kilometers, higher than even modern Space Shuttles fly today. Launched under the direction of the General Electric Company, the Bumper 2 was used primarily for testing rocket systems and for research on the upper atmosphere. Bumper 2 rockets carried small payloads that allowed them to measure attributes including air temperature and cosmic ray impacts. Seven years later, the Soviet Union launched Sputnik I and Sputnik II, the first satellites into Earth orbit. In response in 1958, 50 years ago today, the US created NASA.


Tomorrow's picture: astronomical angst

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 October 2

NGC 253 Close-Up
Credit: NASA, ESA, J. Dalcanton, B. Williams (Univ. Washington)
Ground-based data: T. Rector (Univ. Alaska, Anchorage), T. Abbott, NOAO/AURA/NSF Explanation: This dusty island universe is one of the brightest spiral galaxies in the sky. Seen nearly edge-on, NGC 253 lies a mere 13 million light-years away and is the largest member of the Sculptor Group of galaxies, neighbor to our own local galaxy group. The remarkably sharp, close-up view is based on data from the Hubble's Advanced Camera for Surveys (ACS). Beginning on the left near the galaxy's core, the panorama follows filaments of dust, interstellar gas, and even individual stars toward the galaxy's edge at the far right, a magnificent vista spanning nearly 50,000 light-years. The image data are part of ANGST, the ACS Nearby Galaxy Survey Treasury, a program to explore our cosmic backyard.


Tomorrow's picture: pixels in space

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 October 3

Young Suns of NGC 7129
Credit & Copyright: Bob and Janice Fera (Fera Photography) Explanation: 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.


Tomorrow's picture: pixels in space

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 October 4

A Solar Prominence Unfurls
Credit: STEREO Project, NASA Explanation: On September 29, this magnificent eruptive solar prominence lifted away from the Sun's surface, unfurling into space over the course of several hours. Suspended in twisted magnetic fields, the hot plasma structure is many times the size of planet Earth and was captured in this view by the Sun-watching STEREO (Ahead) spacecraft. The image was recorded in extreme ultraviolet light emitted by ionized Helium, an element originally identified in the solar spectrum. Seen against the brilliant solar surface in visible light, such prominences appear as dark filaments because they are relatively cool. But they are bright themselves when viewed against the blackness of space, arcing above the Sun's edge. A video of the eruption (a 2.6MB .mov file) is available here.


Tomorrow's picture: Sunday's Childe

 

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Astronomy Picture of the Day

Discover the cosmos! Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.
2008 October 5

Earth at Night
Credit: C. Mayhew & R. Simmon (NASA/GSFC), NOAA/NGDC, DMSP Digital Archive Explanation: This is what the Earth looks like at night. Can you find your favorite country or city? Surprisingly, city lights make this task quite possible. Human-made lights highlight particularly developed or populated areas of the Earth's surface, including the seaboards of Europe, the eastern United States, and Japan. Many large cities are located near rivers or oceans so that they can exchange goods cheaply by boat. Particularly dark areas include the central parts of South America, Africa, Asia, and Australia. The above image is actually a composite of hundreds of pictures made by the orbiting DMSP satellites.


Tomorrow's picture: layered mars