Wednesday, March 11, 2015

If You Could See in Radio These Are the Crazy Shapes You’d See in the Sky

If You Could See in Radio These Are the Crazy Shapes You’d See in the Sky:



"Color" radio image of galactic cluster Abell 2256. Credit: Owen et al., NRAO/AUI/NSF.


“Color” radio image of galactic cluster Abell 2256. Credit: Owen et al., NRAO/AUI/NSF.
Even though it’s said that the average human eye can discern from seven to ten million different values and hues of colors, in reality our eyes are sensitive to only a very small section of the entire electromagnetic spectrum, corresponding to wavelengths in the range of 400 to 700 nanometers. Above and below those ranges lie enormously diverse segments of the EM spectrum, from minuscule yet powerful gamma rays to incredibly long, low-frequency radio waves.

Astronomers observe the Universe in all wavelengths because many objects and phenomena can only be detected in EM ranges other than visible light (which itself can easily be blocked by clouds of dense gas and dust.) But if we could see in radio waves the same way we do in visible light waves – that is with longer wavelengths being perceived as “red” and shorter wavelengths seen as “violet,” with all the blues, greens, and yellows in between – our world would look quite different… especially the night sky, which would be filled with fantastic shapes like those seen above!



View of the VLA in New Mexico. Image courtesy of NRAO/AUI.


View of the VLA in New Mexico. Image courtesy of NRAO/AUI.
Created from observations made at the Very Large Array in New Mexico, the image above shows a cluster of over 500 colliding galaxies located 800 million light-years away called Abell 2256. An intriguing target of study across the entire electromagnetic spectrum, here Abell 2256 (A2256 for short) has had its radio emissions mapped to the corresponding colors our eyes can see.

Within an area about the same width as the full Moon a space battle between magical cosmic creatures seems to be taking place! (In reality A2256 spans about 4 million light-years.)

See a visible-light image of A2256 by amateur astronomer Rick Johnson here.

The VLA radio observations will help researchers determine what’s happening within A2256, where multiple groups of galaxy clusters are interacting.

“The image reveals details of the interactions between the two merging clusters and suggests that previously unexpected physical processes are at work in such encounters,” said Frazer Owen of the National Radio Astronomy Observatory (NRAO).



Radio image of the night sky. (Credit: Max Planck Institute for Radio Astronomy, generated by Glyn Haslam.)


Radio image of the night sky. (Credit: Max Planck Institute for Radio Astronomy, generated by Glyn Haslam.)
Learn more about NRAO and radio astronomy here, and you can get an idea of what our view of the Milky Way would look like in radio wavelengths on the Square Kilometer Array’s website.

Source: NRAO



About 

A graphic designer in Rhode Island, Jason writes about space exploration on his blog Lights In The Dark, Discovery News, and, of course, here on Universe Today. Ad astra!

Share this:

A Complete Guide to the March 20th Total Solar Eclipse

A Complete Guide to the March 20th Total Solar Eclipse:



Credit


Totality! The 2012 total solar eclipse as seen from Australia. Credit and copyright: www.hughca.com.
The first of two eclipse seasons for the year is upon us this month, and kicks off with the only total solar eclipse for 2015 on Friday, March 20th.

And what a bizarre eclipse it is. Not only does this eclipse begin just 15 hours prior to the March equinox marking the beginning of astronomical spring in the northern hemisphere, but the shadow of totality also beats path through the high Arctic and ends over the North Pole.



Credit:


An animation of the March 20th eclipse. Credit: NASA/GSFC/AT Sinclair.
Already, umbraphiles — those who chase eclipses — are converging on the two small tracts of terra firma where the umbra of the Moon makes landfall: the Faroe and Svalbard islands. All of Europe, the northern swath of the African continent, north-central Asia and the Middle East will see a partial solar eclipse, and the eclipse will be deeper percentage-wise the farther north you are .

2015 features four eclipses in all: two total lunars and two solars, with one total solar and one partial solar eclipse. Four is the minimum number of solar eclipses that can occur in a calendar year, and although North America misses out on the solar eclipse action this time ’round, most of the continent gets a front row seat to the two final total lunar eclipses of the ongoing tetrad on April 4th and September 28th.

How rare is a total solar eclipse on the vernal equinox? Well, the last total solar eclipse on the March equinox occurred back in 1662 on March 20th. There was also a hybrid eclipse — an eclipse which was annular along a portion of the track, and total along another — on March 20th, 1681. But you won’t have to wait that long for the next, as another eclipse falls on the northward equinox on March 20th, 2034.



Credit


The path of the March 20th eclipse across Europe, including start times for the partial phases, and the path of totality, click to enlarge. For more maps showing the percentage of occlusion, elevation, and more, click here. Credit: Michael Zeiler/GreatAmercianEclipse.com.
Note that in the 21st century, the March equinox falls on March 20th, and will start occasionally falling on March 19th in 2044. We’re also in that wacky time of year where North America has shifted back to ye ‘ole Daylight Saving (or Summer) Time, while Europe makes the change after the eclipse on March 29th. It really can wreak havoc with those cross-time zone plans, we know…

The March 20th eclipse also occurs only a day after lunar perigee, which falls on March 19th at 19:39 UT. This is also one of the closer lunar perigees for 2015 at 357,583 kilometres distant, though the maximum duration of totality for this eclipse is only 2 minutes and 47 seconds just northeast of the Faroe Islands.



Credit:


Views from selected locales in Europe and Africa. Credit: Stellarium.
This eclipse is number 61 of 71 in solar saros series 120, which runs from 933 to 2754 AD. It’s also the second to last total in the series, with the final total solar eclipse for the saros cycle occurring one saros later on March 30th, 2033.

And speaking of obscure eclipse terminology, check out this neat compendium we came across in research. What’s an Exeligmos? How many Heptons are in a Gregoriana?

The 462 kilometre wide path of the eclipse touches down south of Greenland at 9:13 UT at sunrise, before racing across the North Atlantic towards the pole and departing the Earth at 10:21 UT. The sedate partial phases for the eclipse worldwide start at 7:40 UT, and run out to 11:51 UT.

What would it look like to sit at the North Pole and watch a total solar eclipse on the first day of Spring? It would be a remarkable sight, as the disk of the Sun skims just above the horizon for the first time since the September 2014 equinox. Does this eclipse occur at sunrise or sunset as seen from the pole? It would be a rare spectacle indeed!



Credit


An equinoctal eclipse as simulated from the North Pole. Credit: Stellarium.
Alas, this unique view from the pole will more than likely go undocumented. A similar eclipse was caught in 2003 from the Antarctic, and a few intrepid eclipse chasers, including author David Levy did manage to make the journey down under to witness totality from the polar continent.



Credit


Practicing eclipse safety in Africa. Credit: Michael Zeiler/GreatAmericanEclipse.com
Safety is paramount when observing the Sun and a solar eclipse. Eye protection is mandatory during all partial phases across Europe, northern Asia, North Africa and the Middle East. A proper solar filter mask constructed of Baader safety film is easy to construct, and should fit snugly over the front aperture of a telescope. No. 14 welder’s goggles are also dense enough to look at the Sun, as are safety glasses specifically designed for eclipse viewing. Observing the Sun via projection or by using a pinhole projector is safe and easy to do.



Credit


A solar filtered scope ready to go in Tucson, Arizona. Credit: photo by author.
Weather is always the big variable in the days leading up to any eclipse. Unfortunately, March in the North Atlantic typically hosts stormy skies, and the low elevation of the eclipse in the sky may hamper observations as well. From the Faroe Islands, the Sun sits 18 degrees above the horizon during totality, while from the Svalbard Islands it’s even lower at 12 degrees in elevation. Much of Svalbard is also mountainous, making for sunless pockets of terrain that will be masked in shadow on eclipse day. Mean cloud amounts for both locales run in the 70% range, and the Eclipser website hosts a great in-depth climatology discussion for this and every eclipse.



Credit


The view of totality and the planets as seen from the Faroe Islands. Credit: Starry Night.
But don’t despair: you only need a clear view of the Sun to witness an eclipse!

Solar activity is also another big variable. Witnesses to the October 23rd, 2014 partial solar eclipse over the U.S. southwest will recall that we had a massive and very photogenic sunspot turned Earthward at the time. The Sun has been remarkably calm as of late, though active sunspot region 2297 is developing nicely. It will have rotated to the solar limb come eclipse day, and we should have a good grasp on what solar activity during the eclipse will look like come early next week.

And speaking of which: could an auroral display be in the cards for those brief few minutes of totality? It’s not out of the question, assuming the Sun cooperates.  Of course, the pearly white corona of the Sun still gives off a considerable amount of light during totality, equal to about half the brightness of a Full Moon. Still, witnessing two of nature’s grandest spectacles — a total solar eclipse and the aurora borealis — simultaneously would be an unforgettable sight, and to our knowledge, has never been documented!

We also put together some simulations of the eclipse as seen from Earth and space:



Note that an area of southern Spain may witness a transit of the International Space Station during the partial phase of the eclipse. This projection is tentative, as the orbit of the ISS evolves over time. Be sure to check CALSky for accurate predictions in the days leading up to the eclipse.



Credit


The ISS transits the Sun during the eclipse around 9:05 UT as seen from southern Spain. Credit: Starry Night.
Can’t make it to the eclipse? Live in the wrong hemisphere? There are already a few planned webcasts for the March 20th eclipse:

-Astronomia Practica plans to post photos in near real time of the eclipse from northern Scotland.

-Slooh has plans to broadcast the eclipse from the Faroe Islands.

-And here’s another webcast from the Faroe Islands and the path of totality courtesy of Kringvarp Føroya:



-Here’s another broadcast planned of the partial stages of the eclipse as seen from the UK.

-And our friends over at the Virtual Telescope Project also plans on webcasting the solar eclipse:



… and speaking of which, there’s also an exciting new Kickstarter project entitled Chasing Shadows which is headed to the Arctic to follow veteran eclipse chaser Geoff Sims (@beyond_beneath of Twitter):

And stay tuned, as North America and the Pacific region will witness another total lunar eclipse on April 4th 2014. And we’ve only got one more total solar eclipse across Southeast Asia in 2016 before the total solar eclipse of August 21st 2017 spanning the U.S.

Let the first eclipse season of 2015 begin!

Next… how will the solar eclipse affect the European solar grid? Expect an article on just that soon!



About 

David Dickinson is an Earth science teacher, freelance science writer, retired USAF veteran & backyard astronomer. He currently writes and ponders the universe from Tampa Bay, Florida.

Share this:

Monday, March 9, 2015

Persistent Saturnian Auroras

Persistent Saturnian Auroras: APOD: 2014 June 22 - Persistent Saturnian Auroras





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.


2014 June 22




See Explanation.  Clicking on the picture will download
 the highest resolution version available.
Persistent Saturnian Auroras
Image Credit:
J. Clarke
(Boston U.) &
Z. Levay
(STScI),
ESA,
NASA
Explanation:
Are Saturn's auroras like Earth's?

To help answer this question, the
Hubble Space Telescope and the
Cassini spacecraft monitored Saturn's South Pole
simultaneously as
Cassini closed in
on the gas giant in January 2004.

Hubble snapped images in
ultraviolet light, while Cassini recorded
radio emissions and monitored the
solar wind.

Like on Earth, Saturn's auroras
make total or partial rings around
magnetic poles.

Unlike on Earth, however,
Saturn's auroras persist for days, as opposed to only minutes on
Earth.

Although surely created by
charged particles entering the atmosphere,
Saturn's auroras also appear to be
more closely modulated by the
solar wind than either Earth's or
Jupiter's auroras.

The above sequence shows three Hubble images of
Saturn
each taken two days apart.




Tomorrow's picture: lasing space



Four Lasers over Mauna Kea

Four Lasers over Mauna Kea: APOD: 2014 June 23 - Four Lasers over Mauna Kea


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.

2014 June 23


See Explanation. Clicking on the picture will download the highest resolution version available.
Four Lasers over Mauna Kea

Image Credit & Copyright: Jason Chu (IfA Manoa)
Explanation: Are lasers from giant telescopes being used to attack the Galactic center? No. Lasers shot from telescopes are now commonly used to help increase the accuracy of astronomical observations. In some sky locations, Earth atmosphere-induced fluctuations in starlight can indicate how the air mass over a telescope is changing, but many times no bright star exists in the direction where atmospheric information is needed. In these cases, astronomers create an artificial star where they need it -- with a laser. Subsequent observations of the artificial laser guide star can reveal information so detailed about the blurring effects of the Earth's atmosphere that much of this blurring can be removed by rapidly flexing the mirror. Such adaptive optic techniques allow high-resolution ground-based observations of real stars, planets, and nebulae. Pictured above, four telescopes on Mauna Kea, Hawaii, USA are being used simultaneously to study the center of our Galaxy and so all use a laser to create an artificial star nearby.

The Iris Nebula in a Field of Dust

The Iris Nebula in a Field of Dust: APOD: 2014 June 24 - The Iris Nebula in a Field of Dust


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.

2014 June 24


See Explanation. Clicking on the picture will download the highest resolution version available.
The Iris Nebula in a Field of Dust

Image Credit & Copyright: Mikel Martínez
Explanation: What flowers in this field of dark star dust? The Iris Nebula. The striking blue color of the Iris Nebula is created by light from the bright star SAO 19158 reflecting off of a dense patch of normally dark dust. Not only is the star itself mostly blue, but blue light from the star is preferentially reflected by the dust -- the same affect that makes Earth's sky blue. The brown tint of the pervasive dust comes partly from photoluminescence -- dust converting ultraviolet radiation to red light. Cataloged as NGC 7023, the Iris Nebula is studied frequently because of the unusual prevalence there of Polycyclic Aromatic Hydrocarbons (PAHs), complex molecules that are also released on Earth during the incomplete combustion of wood fires. The bright blue portion of the Iris Nebula spans about six light years. The Iris Nebula, pictured above, lies about 1300 light years distant and can be found with a small telescope toward the constellation of Cepheus.

The Hercules Cluster of Galaxies

The Hercules Cluster of Galaxies: APOD: 2014 June 25 - The Hercules Cluster of Galaxies


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.

2014 June 25


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: These are galaxies of the Hercules Cluster, an archipelago of island universes a mere 500 million light-years away. Also known as Abell 2151, this cluster is loaded with gas and dust rich, star-forming spiral galaxies but has relatively few elliptical galaxies, which lack gas and dust and the associated newborn stars. The colors in this remarkably deep composite image clearly show the star forming galaxies with a blue tint and galaxies with older stellar populations with a yellowish cast. The sharp picture spans about 3/4 degree across the cluster center, corresponding to over 6 million light-years at the cluster's estimated distance. Diffraction spikes around brighter foreground stars in our own Milky Way galaxy are produced by the imaging telescope's mirror support vanes. In the cosmic vista many galaxies seem to be colliding or merging while others seem distorted - clear evidence that cluster galaxies commonly interact. In fact, the Hercules Cluster itself may be seen as the result of ongoing mergers of smaller galaxy clusters and is thought to be similar to young galaxy clusters in the much more distant, early Universe.

Conjunction by the Sea

Conjunction by the Sea: APOD: 2014 June 26 - Conjunction by the Sea


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.

2014 June 26
See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: Early morning risers were treated to a beautiful conjunction of Venus and waning Crescent Moon on June 24, captured in this seaside photo near Belmar, New Jersey, USA, planet Earth. The serene celestial pairing is seen above the Atlantic Ocean horizon as the eastern sky grows brighter with dawn's early light. Wispy, scattered clouds appear in silhouette. But the exposure also reveals the night side of the lunar orb in the arms of the sunlit crescent. That shadowed part of the Moon, with hints of the smooth, dark lunar seas or maria, is illuminated by Earthshine, sunlight reflected from planet Earth itself.

Orion Arising

Orion Arising: APOD: 2014 June 28 - Orion Arising


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.

2014 June 28


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: Orion's belt runs just along the horizon, seen through Earth's atmosphere and rising in this starry snapshot from low Earth orbit on board the International Space Station. The belt stars, Alnitak, Alnilam, and Mintaka run right to left and Orion's sword, home to the great Orion Nebula, hangs above his belt, an orientation unfamiliar to denizens of the planet's northern hemisphere. That puts bright star Rigel, at the foot of Orion, still higher above Orion's belt. Of course the brightest celestial beacon in the frame is Sirius, alpha star of the constellation Canis Major. The station's Destiny Laboratory module is in the foreground at the top right.

Galaxy Cove Vista Revisited

Galaxy Cove Vista Revisited: APOD: 2014 June 29 - Galaxy Cove Vista Revisited


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.

2014 June 29


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: To see a vista like this takes patience, hiking, and a camera. Patience was needed in searching out just the right place and waiting for just the right time. A short hike was needed to reach this rugged perch above a secluded cove in Julia Pfeiffer Burns State Park in California, USA. And a camera was needed for the long exposure required to bring out the faint light from stars and nebulae in the background Milky Way galaxy. Moonlight illuminated the hidden beach and inlet behind nearby trees in the above composite image taken last month. Usually obscured McWay Falls is visible just below the image center, while the Pacific Ocean is in view to its right. The above image is a high-resolution sequel to a similar image that appeared last year.

Peculiar Elliptical Galaxy Centaurus A

Peculiar Elliptical Galaxy Centaurus A: APOD: 2014 June 30 - Peculiar Elliptical Galaxy Centaurus A


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.

2014 June 30


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: What's happened to the center of this galaxy? Unusual and dramatic dust lanes run across the center of elliptical galaxy Centaurus A. These dust lanes are so thick they almost completely obscure the galaxy's center in visible light. This is particularly unusual as Cen A's red stars and round shape are characteristic of a giant elliptical galaxy, a galaxy type usually low in dark dust. Cen A, also known as NGC 5128, is also unusual compared to an average elliptical galaxy because it contains a higher proportion of young blue stars and is a very strong source of radio emission. Evidence indicates that Cen A is likely the result of the collision of two normal galaxies. During the collision, many young stars were formed, but details of the creation of Cen A's unusual dust belts are still being researched. Cen A lies only 13 million light years away, making it the closest active galaxy. Cen A, pictured above, spans 60,000 light years and can be seen with binoculars toward the constellation of Centaurus.

Wolf Rayet Star 124: Stellar Wind Machine

Wolf Rayet Star 124: Stellar Wind Machine: APOD: 2014 July 1 - Wolf Rayet Star 124: Stellar Wind Machine


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.

2014 July 1


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: Some stars explode in slow motion. Rare, massive Wolf-Rayet stars are so tumultuous and hot that they slowly disintegrating right before our telescopes. Glowing gas globs each typically over 30 times more massive than the Earth are being expelled by violent stellar winds. Wolf-Rayet star WR 124, visible near the above image center spanning six light years across, is thus creating the surrounding nebula known as M1-67. Details of why this star has been slowly blowing itself apart over the past 20,000 years remains a topic of research. WR 124 lies 15,000 light-years away towards the constellation of Sagitta. The fate of any given Wolf-Rayet star likely depends on how massive it is, but many are thought to end their lives with spectacular explosions such as supernovas or gamma-ray bursts.

Stars at the Galactic Center

Stars at the Galactic Center: APOD: 2015 March 8 - Stars at the Galactic Center


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.

2015 March 8


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: The center of our Milky Way Galaxy is hidden from the prying eyes of optical telescopes by clouds of obscuring dust and gas. But in this stunning vista, the Spitzer Space Telescope's infrared cameras, penetrate much of the dust revealing the stars of the crowded galactic center region. A mosaic of many smaller snapshots, the detailed, false-color image shows older, cool stars in bluish hues. Reddish glowing dust clouds are associated with young, hot stars in stellar nurseries. The very center of the Milky Way was only recently found capable of forming newborn stars. The galactic center lies some 26,000 light-years away, toward the constellation Sagittarius. At that distance, this picture spans about 900 light-years.

Sunday, March 8, 2015

Wolf Rayet Star 124: Stellar Wind Machine

Wolf Rayet Star 124: Stellar Wind Machine: APOD: 2014 July 1 - Wolf Rayet Star 124: Stellar Wind Machine


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.

2014 July 1


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: Some stars explode in slow motion. Rare, massive Wolf-Rayet stars are so tumultuous and hot that they slowly disintegrating right before our telescopes. Glowing gas globs each typically over 30 times more massive than the Earth are being expelled by violent stellar winds. Wolf-Rayet star WR 124, visible near the above image center spanning six light years across, is thus creating the surrounding nebula known as M1-67. Details of why this star has been slowly blowing itself apart over the past 20,000 years remains a topic of research. WR 124 lies 15,000 light-years away towards the constellation of Sagitta. The fate of any given Wolf-Rayet star likely depends on how massive it is, but many are thought to end their lives with spectacular explosions such as supernovas or gamma-ray bursts.

NGC 4651: The Umbrella Galaxy

NGC 4651: The Umbrella Galaxy: APOD: 2014 July 2 - NGC 4651: The Umbrella Galaxy


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.

2014 July 2


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: Spiral galaxy NGC 4651 is a mere 62 million light-years distant, toward the well-groomed northern constellation Coma Berenices. About the size of our Milky Way, this island universe is seen to have a faint umbrella-shaped structure that seems to extend (left) some 100 thousand light-years beyond the bright galactic disk. The giant cosmic umbrella is now known to be composed of tidal star streams - extensive trails of stars gravitationally stripped from a smaller satellite galaxy. The small galaxy was eventually torn apart in repeated encounters as it swept back and forth on eccentric orbits through NGC 4651. In fact, the picture insert zooms in on the smaller galaxy's remnant core, identified in an extensive exploration of the system, using data from the large Subaru and Keck telescopes on Mauna Kea. Work begun by a remarkable collaboration of amateur and professional astronomers to image faint structures around bright galaxies suggests that even in nearby galaxies, tidal star streams are common markers of such galactic mergers. The result is explained by models of galaxy formation that also apply to our own Milky Way.

Along the Cygnus Wall

Along the Cygnus Wall: APOD: 2014 July 3 - Along the Cygnus Wall


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.

2014 July 3


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: The prominent ridge of emission featured in this vivid skyscape is known as the Cygnus Wall. Part of a larger emission nebula with a distinctive shape popularly called The North America Nebula, the ridge spans about 10 light-years along an outline that suggests the western coast of Mexico. Constructed from narrowband image data, the cosmic close-up maps emission from sulfur, hydrogen, and oxygen atoms to red, green, and blue colors. The result highlights the bright ionization front with fine details of dark, dusty forms in silhouette. Sculpted by energetic radiation from the region's young, hot, massive stars, the dark shapes inhabiting the view are clouds of cool gas and dust with stars likely forming within. The North America Nebula itself, NGC 7000, is about 1,500 light-years away. To find it, look northeast of bright star Deneb in the high flying constellation Cygnus.

M106 Across the Spectrum

M106 Across the Spectrum: APOD: 2014 July 5 - M106 Across the Spectrum


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.

2014 July 5


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: The spiral arms of bright, active galaxy M106 sprawl through this remarkable multiwavelength portrait, composed of image data from radio to X-rays, across the electromagnetic spectrum. Also known as NGC 4258, M106 can be found toward the northern constellation Canes Venatici. The well-measured distance to M106 is 23.5 million light-years, making this cosmic scene about 60,000 light-years across. Typical in grand spiral galaxies, dark dust lanes, youthful star clusters, and star forming regions trace spiral arms that converge on a bright nucleus. But this composite highlights two anomalous arms in radio (purple) and X-ray (blue) that seem to arise in the central region of M106, evidence of energetic jets of material blasting into the galaxy's disk. The jets are likely powered by matter falling into a massive central black hole.

Manhattanhenge: A New York City Sunset

Manhattanhenge: A New York City Sunset: APOD: 2014 July 6 - Manhattanhenge: A New York City Sunset


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.

2014 July 6


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: This coming Saturday, if it is clear, well placed New Yorkers can go outside at sunset and watch their city act like a modern version of Stonehenge. Manhattan's streets will flood dramatically with sunlight just as the Sun sets precisely at each street's western end. Usually, the tall buildings that line the gridded streets of New York City's tallest borough will hide the setting Sun. This effect makes Manhattan a type of modern Stonehenge, although only aligned to about 30 degrees east of north. Were Manhattan's road grid perfectly aligned to east and west, today's effect would occur on the Vernal and Autumnal Equinox, March 21 and September 21, the only two days that the Sun rises and sets due east and west. Pictured above in this horizontally stretched image, the Sun sets down 34th Street as viewed from Park Avenue. If Saturday's sunset is hidden by clouds do not despair -- the same thing happens twice each year: in late May and mid July. On none of these occasions, however, should you ever look directly at the Sun.

J1502 1115: A Triple Black Hole Galaxy

J1502 1115: A Triple Black Hole Galaxy: APOD: 2014 July 7 - J1502+1115: A Triple Black Hole Galaxy


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.

2014 July 7


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: Most galaxies contain one supermassive black hole -- why does this galaxy have three? The likely reason is that galaxy J1502+1115 is the product of the recent coalescence of three smaller galaxies. The two closest black holes are shown above resolved in radio waves by large coordinated array of antennas spread out over Europe, Asia, and Africa. These two supermassive black holes imaged are separated by about 500 light years and each has a likely mass about 100 million times the mass of our Sun. Currently, J1502+1115, at a redshift of 0.39, is one of only a few triple black hole system known and is being studied to learn more about galaxy and supermassive black hole interaction rates during the middle ages of our universe. Gravitational radiation emitted by such massive black hole systems may be detectable by future observatories.

Gliese 832c: The Closest Potentially Habitable Exoplanet

Gliese 832c: The Closest Potentially Habitable Exoplanet: APOD: 2014 July 9 - Gliese 832c: The Closest Potentially Habitable Exoplanet


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.

2014 July 9


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: This planet is only 16 light years away -- could it harbor life? Recently discovered exoplanet Gliese 832c has been found in a close orbit around a star that is less bright than our Sun. An interesting coincidence, however, is that Gliese 832c receives just about the same average flux from its parent star as does the Earth. Since the planet was discovered only by a slight wobble in its parent star's motion, the above illustration is just an artistic guess of the planet's appearance -- much remains unknown about Gliese 832c's true mass, size, and atmosphere. If Gliese 832c has an atmosphere like Earth, it may be a super-Earth undergoing strong seasons but capable of supporting life. Alternatively, if Gliese 832c has a thick atmosphere like Venus, it may be a super-Venus and so unlikely to support life as we know it. The close 16-light year distance makes the Gliese 832 planetary system currently the nearest to Earth that could potentially support life. The proximity of the Gliese 832 system therefore lends itself to more detailed future examination and, in the most spectacularly optimistic scenario, actual communication -- were intelligent life found there.

Noctilucent Clouds over London

Noctilucent Clouds over London: APOD: 2014 July 10 - Noctilucent Clouds over London


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.

2014 July 10


See Explanation. Clicking on the picture will download the highest resolution version available.
Explanation: This scene from the early morning hours of July 3 looks out across the River Thames from the Westminster Bridge. Part of a luminous timelapse video (vimeo), the frame captures a sight familiar in London, the nighttime glow of the London Eye. But a not-so-familiar sight is shining in the still dark sky above, widespread noctilucent clouds. From the edge of space, about 80 kilometers above Earth's surface, the icy clouds can still reflect sunlight even though the Sun itself is below the horizon as seen from the ground. Usually spotted at high latitudes in summer months the diaphanous apparitions are also known as polar mesospheric clouds. The seasonal clouds are understood to form as water vapor driven into the cold upper atmosphere condenses on the fine dust particles supplied by disintegrating meteors or volcanic ash. NASA's AIM mission provides daily projections of the noctilucent clouds as seen from space.