Astronomy Picture of the Day for April 15 – A Possibly Titanic Mirage

Astronomy Picture of the Day

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2012 April 15
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Fata Morgana: A Possibly Titanic Mirage
Image Credit & Copyright: Mila Zinkova

 

 Explanation: Did this mirage help sink the Titanic? The optical phenomenon called Fata Morgana can make strange shapes or a false wall of water appear above a watery horizon. When conditions are right, light reflecting off of cold water will be bent by an unusual layer of warm air above to arrive at the observer from several different angles. A conceptually comparable mirage can make a setting Sun appear strangely distorted or a distant pavement appear wet. One hundred years ago today, such a Fata Morgana mirage might have obscured real icebergs from the clear view of crew onboard the Titanic. Additional evidence for this distortion hypothesis arises from the nearby vessel SS Californian which reported sightings consistent with Fata Morgana mirages. The above Fata Morgana mirage was taken off the US Pacific coast in 2008.

Astronomy Picture of the Day for April 12 – A Beautiful Trifid

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A Beautiful Trifid
Image Credit & Copyright: R Jay Gabany Explanation: The beautiful Trifid Nebula is a cosmic study in colorful contrasts. Also known as M20, it lies about 5,000 light-years away toward the nebula rich constellation Sagittarius. A star forming region in the plane of our galaxy, the Trifid illustrates three different types of astronomical nebulae; red emission nebulae dominated by light emitted by hydrogen atoms, blue reflection nebulae produced by dust reflecting starlight, and dark nebulae where dense dust clouds appear in silhouette. The bright red emission region, roughly separated into three parts by obscuring, dark dust lanes, lends the Trifid its popular name. In this well met scene, the red emission is also juxtaposed with the telltale blue haze of reflection nebulae. Pillars and jets sculpted by newborn stars, below and left of the emission nebula’s center, appear in Hubble Space Telescope close-up images of the region. The Trifid Nebula is about 40 light-years across.

Astronomy Picture of the Day for April 9th

Astronomy Picture of the Day

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2012 April 9
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Blue Straggler Stars in Globular Cluster M53
Image Credit: ESA/Hubble, NASA 

Explanation: If our Sun were part of M53, the night sky would glow like a jewel box of bright stars. M53, also known as NGC 5024, is one of about 250 globular clusters that survive in our Galaxy. Most of the stars in M53 are older and redder than our Sun, but some enigmatic stars appear to be bluer and younger. These young stars might contradict the hypothesis that all the stars in M53 formed at nearly the same time. These unusual stars are known as blue stragglers and are unusually common in M53. After much debate, blue stragglers are now thought to be stars rejuvenated by fresh matter falling in from a binary star companion. By analyzing pictures of globular clusters like the above image taken by the Hubble Space Telescope, astronomers use the abundance of stars like blue stragglers to help determine the age of the globular cluster and hence a limit on the age of the universe. M53, visible with a binoculars towards the constellation of Bernice’s Hair (Coma Berenices), contains over 250,000 stars and is one of the furthest globulars from the center of our Galaxy.

Astronomy Picture of the Day for March 28th

Astronomy Picture of the Day

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2012 March 28
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Earthshine and Venus Over Sierra de Guadarrama
Image Credit: Daniel Fernández (DANIKXT)  

 

Explanation: What just above that ridge? The Moon. Specifically, the Earth’s Moon was caught just above the horizon in a young crescent phase. The familiar Moon might look a bit odd as the exposure shows significant Earthshine — the illumination of the part of the Moon hidden from direct sunlight by the sun-reflecting Earth. Also captured in the image is the bright planet Venus on the right. Venus and Jupiter passed only three degrees from each other last week during a photogenic planetary conjunction. The above image was taken two days ago near Madrid, Spain. The foreground horizon silhouette includes some of the Seven Peaks of the Sierra de Guadarrama mountain range. Just a few minutes after this picture was taken, the Moon set.

Astronomy Picture of the Day for March 21

Astronomy Picture of the Day

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2012 March 21
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Aurora Over Iceland
Image Credit & Copyright: Daniel Lopez (El Cielo de Canarias)  

 

Explanation: If you see a sky like this — photograph it. Three nights ago in Iceland, an adventurous photographer (pictured) chanced across a sky full of aurora and did just that. Afterwards, by stitching together five smaller photographs, the entire aurora-lit sky was recreated in this 180-degree panorama taken from Vatnajökull glacier. Auroras are sparked by energetic particles from the Sun impacting the magnetic environment around the Earth. Resultant energetic particles such as electrons and protons rain down near the Earth’s poles and impact the air. The impacted air molecules obtain excited electrons, and when electrons in oxygen molecules fall back to their ground state, they emit green light. Auroras are known to have many shapes and colors.

Astronomy Picture of the Day for Mar. 7 – The Witch Head Nebula

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IC 2118: The Witch Head Nebula
Image Credit & Copyright: Gimmi Ratto & Davide Bardini (Collecting Photons) 

Explanation: Double, double toil and trouble; Fire burn, and cauldron bubble — maybe Macbeth should have consulted the Witch Head Nebula. This suggestively shaped reflection nebula is associated with the bright star Rigel in the constellation Orion. More formally known as IC 2118, the Witch Head Nebula glows primarily by light reflected from bright star Rigel, located just below the lower edge of the above image. Fine dust in the nebula reflects the light. The blue color is caused not only by Rigel’s blue color but because the dust grains reflect blue light more efficiently than red. The same physical process causes Earth’s daytime sky to appear blue, although the scatterers in Earth’s atmosphere are molecules of nitrogen and oxygen. The nebula lies about 1000 light-years away.

Astronomy Picture of the Day for Feb. 23 – A Zodiacal Skyscape

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2012 February 23
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A Zodiacal Skyscape
Image Credit & Copyright: Jack Fusco 

Explanation: Venus and Jupiter are this month’s two brightest planets. Shortly after sunset on February 20, they dominate the sky above the western horizon and this snowy landscape. In clear and transparent skies over Cherry Springs State Park, Pennsylvania, USA, they are also seen immersed in Zodiacal light. The extended, diffuse, triangular glow is sunlight scattered by dust along the plane of the ecliptic. Brighter near the horizon, the Zodiacal glow angles upward, first to Venus and then to Jupiter hugging the ecliptic as they orbit the Sun. Fading even further, the glow stretches toward the lovely Pleides star cluster near the top of the frame. Following their appearance in this Zodiacal skyscape, the coming days will see Venus and Jupiter sharing the early evening sky with a young crescent Moon. The two bright planets are even headed for a close pairing or conjunction, separated by about 3 degrees on March 13.

Astronomy Picture of the Day for February 11

Astronomy Picture of the Day

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2012 January 17
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IC 2118: The Witch Head Nebula
Image Credit & Copyright: Gimmi Ratto & Davide Bardini (Collecting Photons) 

 

Explanation: Double, double toil and trouble; Fire burn, and cauldron bubble — maybe Macbeth should have consulted the Witch Head Nebula. This suggestively shaped reflection nebula is associated with the bright star Rigel in the constellation Orion. More formally known as IC 2118, the Witch Head Nebula glows primarily by light reflected from bright star Rigel, located just below the lower edge of the above image. Fine dust in the nebula reflects the light. The blue color is caused not only by Rigel’s blue color but because the dust grains reflect blue light more efficiently than red. The same physical process causes Earth’s daytime sky to appear blue, although the scatterers in Earth’s atmosphere are molecules of nitrogen and oxygen. The nebula lies about 1000 light-years away.

Astronomy Picture of the Day for Thursday, Feb. 9th

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Nobels for a Strange Universe
Image Credit: High-Z Supernova Search Team, HST, NASA

 

Explanation: Thirteen years ago results were first presented indicating that most of the energy in our universe is not in stars or galaxies but is tied to space itself. In the language of cosmologists, a large cosmological constant is directly implied by new distant supernova observations. Suggestions of a cosmological constant (lambda) were not new — they have existed since the advent of modern relativistic cosmology. Such claims were not usually popular with astronomers, though, because lambda is so unlike known universe components, because lambda’s value appeared limited by other observations, and because less-strange cosmologies without lambda had previously done well in explaining the data. What is noteworthy here is the seemingly direct and reliable method of the observations and the good reputations of the scientists conducting the investigations. Over the past thirteen years, independent teams of astronomers have continued to accumulate data that appears to confirm the existence of dark energy and the unsettling result of a presently accelerating universe. This year, the team leaders were awarded the Nobel Prize in Physics for their work. The above picture of a supernova that occurred in 1994 on the outskirts of a spiral galaxy was taken by one of these collaborations.

Astronomy Picture of the Day for February 8

Astronomy Picture of the Day

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2012 February 8
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Enceladus Backlit by Saturn
Image Credit: Cassini Imaging Team, SSI, JPL, ESA, NASA; Color Composite: Gordan Ugarkovic 

Explanation: This moon is shining by the light of its planet. Specifically, a large portion of Enceladus pictured above is illuminated primarily by sunlight first reflected from the planet Saturn. The result is that the normally snow-white moon appears in the gold color of Saturn’s cloud tops. As most of the illumination comes from the image left, a labyrinth of ridges throws notable shadows just to the right of the image center, while the kilometer-deep canyon Labtayt Sulci is visible just below. The bright thin crescent on the far right is the only part of Enceladus directly lit by the Sun. The above image was taken last year by the robotic Cassini spacecraft during a close pass by by the enigmatic moon. Inspection of the lower part of this digitally sharpened image reveals plumes of ice crystals thought to originate in a below-surface sea.

Astronomy Picture of the Day for Feb. 6th

Astronomy Picture of the Day

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2012 February 6
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Dust of the Orion Nebula
Image Credit & Copyright: Nicolás Villegas 

Explanation: What surrounds a hotbed of star formation? In the case of the Orion Nebula — dust. The entire Orion field, located about 1600 light years away, is inundated with intricate and picturesque filaments of dust. Opaque to visible light, dust is created in the outer atmosphere of massive cool stars and expelled by a strong outer wind of particles. The Trapezium and other forming star clusters are embedded in the nebula. The intricate filaments of dust surrounding M42 and M43 appear brown in the above image, while central glowing gas is highlighted in red. Over the next few million years much of Orion’s dust will be slowly destroyed by the very stars now being formed, or dispersed into the Galaxy.

Astronomy Picture of the Day for Feb. 4th

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2012 February 4
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Comet Garradd and M92
Image Credit & Copyright: Rolando Ligustri (CARA Project, CAST) 

Explanation: Sweeping slowly through the constellation Hercules, Comet Garradd (C2009/P1) passed with about 0.5 degrees of globular star cluster M92 on February 3. Captured here in its latest Messier moment, the steady performer remains just below naked-eye visibility with a central coma comparable in brightness to the dense, well-known star cluster. The rich telescopic view from New Mexico’s, early morning skies, also features Garradd’s broad fan shaped dust tail and a much narrower ion tail that extends up and beyond the right edge of the frame. Pushed out by the pressure of sunlight, the dust tail tends to trail the comet along its orbit while the ion tail, blown by the solar wind, streams away from the comet in the direction opposite the Sun. Of course, M92 is over 25,000 light-years away. Comet Garradd is 12.5 light-minutes from planet Earth, arcing above the ecliptic plane.

Astronomy Picture of the Day for Jan. 29th

Astronomy Picture of the Day

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2012 January 29
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Molecular Cloud Barnard 68
Image Credit: FORS Team, 8.2-meter VLT Antu, ESO 

 

Explanation: Where did all the stars go? What used to be considered a hole in the sky is now known to astronomers as a dark molecular cloud. Here, a high concentration of dust and molecular gas absorb practically all the visible light emitted from background stars. The eerily dark surroundings help make the interiors of molecular clouds some of the coldest and most isolated places in the universe. One of the most notable of these dark absorption nebulae is a cloud toward the constellation Ophiuchus known as Barnard 68, pictured above. That no stars are visible in the center indicates that Barnard 68 is relatively nearby, with measurements placing it about 500 light-years away and half a light-year across. It is not known exactly how molecular clouds like Barnard 68 form, but it is known that these clouds are themselves likely places for new stars to form. In fact, Barnard 68 itself has been found likely to collapse and form a new star system. It is possible to look right through the cloud in infrared light.

Astronomy Picture of the Day for Jan. 28th

Astronomy Picture of the Day

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2012 January 28
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Planet Aurora Borealis
Image Credit & Copyright: Göran Strand 

Explanation: Illuminated by an eerie greenish light, this remarkable little planet is covered with ice and snow and ringed by tall pine trees. Of course, this little planet is actually planet Earth, and the surrounding stars are above the horizon near Östersund, Sweden. The pale greenish illumination is from a curtain of shimmering Aurora Borealis also known as the Northern Lights. The display was triggered when a giant solar coronal mass ejection (CME) rocked planet Earth’s magnetosphere on January 24th and produced a strong geomagnetic storm. Northern hemisphere skygazers will also recognize the familiar orientation of stars at the left, including the Pleiades and Hyades star clusters and the stars of Orion. Increasing solar activity has caused recent auroral displays to be wide spread, including Aurora Australis, the Southern Lights, at high southern latitudes.

Astronomy Picture of the Day for Jan. 23

Astronomy Picture of the Day

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2012 January 23
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Deep Orion Over the Canary Islands
Image Credit & Copyright: Juan Carlos Casado (TWAN) 

Explanation: Which attracts your eye more — the sky or the ground? On the ground are rocky peaks in Teide National Park on Tenerife Island of the Spanish Canary Islands off the northwestern coast of Africa. The volcanic landscape features old island summits and is sometimes used as a testbed for instruments on future Martian rovers. The lights of a nearby hotel shine on the far left. Storm clouds are visible on the horizon, artificially strutted from multiple exposures. Dividing the sky, across the middle of the above deep image, is the vertical band of the Milky Way Galaxy. The red circle on the right is Barnard’s Loop, near the center of which are the famous belt stars of the constellation Orion. Soon after the above image was taken, during an evening earlier this year, storm clouds rolled across, and indoor locations began to attract eyes the most.