/sci/ - Science & Math

>>6580747
daylight bump

>Dedicated sky enthusiasts will likely note -- and are encouraged to provide -- polite corrections.
/sci/, today's APOD was made for nit-pickers like you. Have at it.

How to Identify that Light in the Sky

What is that light in the sky? Perhaps one of humanity's more common questions, an answer may result from a few quick observations. For example -- is it moving or blinking? If so, and if you live near a city, the answer is typically an airplane, since planes are so numerous and so few stars and satellites are bright enough to be seen over the din of artificial city lights. If not, and if you live far from a city, that bright light is likely a planet such as Venus or Mars -- the former of which is constrained to appear near the horizon just before dawn or after dusk. Sometimes the low apparent motion of a distant airplane near the horizon makes it hard to tell from a bright planet, but even this can usually be discerned by the plane's motion over a few minutes. Still unsure? The above chart gives a sometimes-humorous but mostly-accurate assessment. Dedicated sky enthusiasts will likely note -- and are encouraged to provide -- polite corrections.

Tomorrow's picture: x-ray whirlpool
apod.nasa.gov/apod/

A Green Flash from the Sun

Many think it is just a myth. Others think it is true but its cause isn't known. Adventurers pride themselves on having seen it. It's a green flash from the Sun. The truth is the green flash does exist and its cause is well understood. Just as the setting Sun disappears completely from view, a last glimmer appears startlingly green. The effect is typically visible only from locations with a low, distant horizon, and lasts just a few seconds. A green flash is also visible for a rising Sun, but takes better timing to spot. A dramatic green flash, as well as an even more rare red flash, was caught in the above photograph recently observed during a sunset visible from the Observatorio del Roque de Los Muchachos in the Canary Islands, Spain. The Sun itself does not turn partly green or red -- the effect is caused by layers of the Earth's atmosphere acting like a prism.

apod.nasa.gov/apod/

late night bump

Halo of the Cat's Eye

The Cat's Eye Nebula (NGC 6543) is one of the best known planetary nebulae in the sky. Its haunting symmetries are seen in the very central region of this stunning false-color picture, processed to reveal the enormous but extremely faint halo of gaseous material, over three light-years across, which surrounds the brighter, familiar planetary nebula. Made with data from the Nordic Optical Telescope in the Canary Islands, the composite picture shows extended emission from the nebula. Planetary nebulae have long been appreciated as a final phase in the life of a sun-like star. Only much more recently however, have some planetaries been found to have halos like this one, likely formed of material shrugged off during earlier active episodes in the star's evolution. While the planetary nebula phase is thought to last for around 10,000 years, astronomers estimate the age of the outer filamentary portions of this halo to be 50,000 to 90,000 years.

Tomorrow's picture: dragon tail
apod.nasa.gov/apod/

Planetary Nebula Abell 36

The gorgeous, gaseous shroud of a dying sunlike star, planetary nebula Abell 36 lies a mere 800 light-years away in the constellation of Virgo. At that distance it spans over 1.5 light-years in this sharp telescopic view. Shrugging off its outer layers, the nebula's central star is contracting and becoming hotter, evolving towards a final white dwarf phase. In fact, in Abell 36, the central star is estimated to have a surface temperature of over 73,000 K, compared to the Sun's present 6,000 K temperature. As a result, the intensely hot star is much brighter in ultraviolet light, compared to its visual appearance here. The invisible ultraviolet light ionizes hydrogen and oxygen atoms in the nebula and ultimately powers the beautiful visible light glow.

Tomorrow's picture: under southern skies
apod.nasa.gov/apod/

Millions of Stars in Omega Centauri

Globular star cluster Omega Centauri, also known as NGC 5139, is some 15,000 light-years away. The cluster is packed with about 10 million stars much older than the Sun within a volume about 150 light-years in diameter, the largest and brightest of 200 or so known globular clusters that roam the halo of our Milky Way galaxy. Though most star clusters consist of stars with the same age and composition, the enigmatic Omega Cen exhibits the presence of different stellar populations with a spread of ages and chemical abundances. In fact, Omega Cen may be the remnant core of a small galaxy merging with the Milky Way. This astronomically sharp color image of the classic globular cluster was recorded in March under Chilean skies from Hacienda Los Andes.

Tomorrow's picture: pixels in space

>>6559272
It's in the constellation Monoceros, so it's a unicorn cock.

The Cone Nebula from Hubble

Stars are forming in the gigantic dust pillar called the Cone Nebula. Cones, pillars, and majestic flowing shapes abound in stellar nurseries where natal clouds of gas and dust are buffeted by energetic winds from newborn stars. The Cone Nebula, a well-known example, lies within the bright galactic star-forming region NGC 2264. The Cone was captured in unprecedented detail in this close-up composite of several observations from the Earth-orbiting Hubble Space Telescope. While the Cone Nebula, about 2,500 light-years away in Monoceros, is around 7 light-years long, the region pictured here surrounding the cone's blunted head is a mere 2.5 light-years across. In our neck of the galaxy that distance is just over half way from the Sun to its nearest stellar neighbor, the Alpha Centauri star system. The massive star NGC 2264 IRS, seen by Hubble's infrared camera in 1997, is the likely source of the wind sculpting the Cone Nebula and lies off the top of the image. The Cone Nebula's reddish veil is produced by glowing hydrogen gas.

Tomorrow's picture: open space
apod.nasa.gov/apod/

Star Factory Messier 17

What's happening at the center of this nebula? Sculpted by stellar winds and radiation, the star factory known as Messier 17 lies some 5,500 light-years away in the nebula-rich constellation Sagittarius. At that distance, this degree wide field of view spans almost 100 light-years. The sharp, composite, color image utilizing data from space and ground based telescopes, follows faint details of the region's gas and dust clouds against a backdrop of central Milky Way stars. Stellar winds and energetic light from hot, massive stars formed from M17's stock of cosmic gas and dust have slowly carved away at the remaining interstellar material producing the cavernous appearance and undulating shapes. M17 is also known as the Omega Nebula or the Swan Nebula.

Tomorrow's picture: hubble cone
apod.nasa.gov/apod/

Camelopardalids and ISS

From a camp on the northern shores of the Great Lake Erie, three short bright meteor streaks were captured in this composited night skyscape. Recorded over the early morning hours of May 24, the meteors are illusive Camelopardalids. Their trails point back to the meteor shower's radiant near Polaris, in the large but faint constellation Camelopardalis the camel leopard, or in modern terms the Giraffe. While a few meteors did appear, the shower was not an active one as the Earth crossed through the predicted debris trail of periodic comet 209P/LINEAR. Of course, the long bright streak in the image did appear as predicted. Early on May 24, the International Space Station made a bright passage through northern skies.

Tomorrow's picture: southern sky time-lapse
apod.nasa.gov/apod/

>>6552111
Please read the complete explanation, not just the single line I quoted there. The phenomenon is rare and only happens when events are just right. I can assure you that this is a natural phenomenon and though rare, is actually not that uncommon at medium latitudes.
>the alternative explanation that it is spacecraft beyond our knowledge is just an uncomfortable consideration, but it's the better one to make.
I'm not accustomed to this kind of absurd reasoning on /sci/. I don't even know how to respond to this except to say that they are in fact natural and I very much doubt your claim of having a masters in atmospheric sciences.

>>6552072
the explanation is written right beside the picture. Please read the text in the OP.
>The reason here is that ice crystals in distant cirrus clouds are acting like little floating prisms

Bumping again. The shower is going on now, I've seen three already in just 30 minutes, even in a light polluted city.

Bump for Meteor's sake

Tonight be on the look out for a BRAND NEW METEOR SHOWER!!

It's not quite clear how the Camelopardalids (CAM-ee-low-par-DAL-ids) will perform exactly, but according to the Royal Astronomical Society of Canada, "It is highly likely this will be the strongest meteor display of 2014 visible from North America."

Tonight the Earth passes through a debris field for the first time left by Comet 209P/LINEAR nearly 200 years ago!

The best time to view the shower is between 2 and 6am ET, so stay up late or get up early to get a glimpse of a first time event!

Or, you can watch a live stream of the meteor shower and get more information here:
http://www.space.com/25987-meteor-shower-meteor-storm-webcasts-tonight.html

and APOD has a gallery where you can upload your own pictures of the shower and view pictures from other skywatchers here:
http://asterisk.apod.com/viewtopic.php?f=29&t=33444

A Circumhorizontal Arc Over Ohio

Why would clouds appear to be different colors? The reason here is that ice crystals in distant cirrus clouds are acting like little floating prisms. Sometimes known as a fire rainbow for its flame-like appearance, a circumhorizon arc lies parallel to the horizon. For a circumhorizontal arc to be visible, the Sun must be at least 58 degrees high in a sky where cirrus clouds are present. Furthermore, the numerous, flat, hexagonal ice-crystals that compose the cirrus cloud must be aligned horizontally to properly refract sunlight in a collectively similar manner. Therefore, circumhorizontal arcs are quite unusual to see. This circumhorizon display was photographed through a polarized lens above Dublin, Ohio in 2009.

Tomorrow's picture: camel stripes?

Rosetta's Target Comet
>animooted

The Rosetta spacecraft captured this remarkable series of 9 frames between March 27 and May 4, as it closed from 5 million to 2 million kilometers of its target comet. Cruising along a 6.5 year orbit toward closest approach to the Sun next year, periodic comet 67P/Churyumov-Gerasimenko is seen moving past a distant background of stars in Sagittarius and gobular star cluster M104. The comet's developing coma is actually visible by the end of the sequence, extending for some 1300 km into space. Rosetta is scheduled for an early August rendezvous with the comet's nucleus. Now clearly active, the nucleus is about 4 kilometers in diameter, releasing the dusty coma as its dirty ices begin to sublimate in the sunlight. The Rosetta lander's contact with the surface of the nucleus is anticipated in November.

Tomorrow's picture: light-weekend
apd.nasa.gov/apod/

In the Center of Spiral Galaxy M61

M61 is a barred spiral galaxy located in the nearby Virgo Cluster of Galaxies. Visible in M61 are a host of features common to spiral galaxies: bright spiral arms, a central bar, dust lanes, and bright knots of stars. M61, also known as NGC 4303, in similar to our own Milky Way Galaxy. M61 was discovered by telescope in 1779 twice on the same day, but one observer initially mistook the galaxy for a comet. Light from M61 takes about 55 million years to reach us. The above image of the central regions of M61 was taken with the Hubble Space Telescope and adapted for release as part of the Hubble's Hidden Treasures image processing competition.

Tomorrow's picture: open space
apod.nasa.gov/apod/

Meteors, Planes, and a Galaxy over Bryce Canyon

Sometimes land and sky are both busy and beautiful. The landscape pictured in the foreground encompasses Bryce Canyon in Utah, USA, famous for its many interesting rock structures eroded over millions of years. The skyscape above, photogenic in its own right, encompasses the arching central disk of our Milky Way Galaxy, streaks that include three passing airplanes and at least four Eta Aquariid meteors, and bright stars that include the Summer Triangle. The above image is a digital panorama created from 12 smaller images earlier this month on the night May 6. If you missed the recent Eta Aquariids meteor shower though, don't fret -- you may get an unexpected reprieve. Sky enthusiasts are waiting to see if a new meteor shower develops in the early morning hours of Saturday, May 24, when the Earth moves through a possibly dense cloud of dust and debris ejected by Comet 209P/LINEAR.

Tomorrow's picture: spiral sprawl
apod.nasa.gov/apod/

Poll: Do you like APOD's leading question? Many APOD explanations start with a question. Do you like this format? Cast your vote here:
http://asterisk.apod.com/viewtopic.php?f=28&t=33417

Jupiter's Great Red Spot from Voyager 1

What will become of Jupiter's Great Red Spot? Recorded as shrinking since the 1930s, the rate of the Great Red Spot's size appears to have accelerated just in the past few years. A hurricane larger than Earth, the Great Red Spot has been raging at least as long as telescopes could see it. Like most astronomical phenomena, the Great Red Spot was neither predicted nor immediately understood after its discovery. Although small eddies that feed into the storm system seem to play a role, a more full understanding of the gigantic storm cloud remains a topic of continued research, and may result in a better understanding of weather here on Earth. The above image is a digital enhancement of an image of Jupiter taken in 1979 by the Voyager 1 spacecraft as it zoomed by the Solar System's largest planet. NASA's Juno spacecraft is currently heading toward Jupiter and will arrive in 2016.

Tomorrow's picture: meteors streaking
apod.nasa.gov/apod/

Opportunity's Mars Analemma

Staring up into the martian sky, the Opportunity rover captured an image at 11:02 AM local mean time nearly every 3rd sol, or martian day, for 1 martian year. Of course, the result is this martian analemma, a curve tracing the Sun's motion through the sky in the course of a year (668 sols) on the Red Planet. Spanning Earth dates from July, 16, 2006 to June 2, 2008 the images are shown composited in this zenith-centered, fisheye projection. North is at the top surrounded by a panoramic sky and landscape made in late 2007 from inside Victoria crater. The tinted martian sky is blacked out around the analemma images to clearly show the Sun's positions. Unlike Earth's figure-8-shaped analemma, Mars' analemma is pear-shaped, because of its similar axial tilt but more elliptical orbit. When Mars is farther from the Sun, the Sun progresses slowly in the martian sky creating the pointy top of the curve. When close to the Sun and moving quickly, the apparent solar motion is stretched into the rounded bottom. For several sols some of the frames are missing due to rover operations and dust storms.

Tomorrow's picture: light-weekend
apod.nasa.gov/apod/