Terry's Astronomy Thread.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
August 7, 2013

-Bright Vega passes closest to overhead around 10 or 11 p.m., depending on how far east or west you are in your time zone. How closely it misses your zenith depends on how far north or south you live. It passes right through the zenith if you're at latitude 39° north (Washington DC, Cincinnati, Kansas City, Lake Tahoe). How closely can you judge this by looking?

-Yesterday, August 6th, the new Moon passed in front of the sun, producing a partial solar eclipse. The only place to see it was from space. NASA's Solar Dynamics Observatory (SDO) photographed the eclipse from geosynchronous orbit approximately 36,000 km above Earth's surface. Beyond the novelty of observing an eclipse from space, these images have practical value to the SDO science team. The sharp edge of the lunar limb helps researchers measure the in-orbit characteristics of the telescope - e.g., how light diffracts around the telescope's optics and filter support grids. Once these are calibrated, it is possible to correct SDO data for instrumental effects and sharpen the images even more than before.

-Launched on August 3rd, Japan's unmanned HTV-4 cargo carrier is now chasing the International Space Station around Earth. The two spaceships will rendevous on Friday, August 9th. Meanwhile, skywatchers are enjoying the chase. The below picture is from Gary of Fort Davis, Texas when he witnessed a bright flare from the HTV-4 reflecting sunlight.

News Posted Today:
August 6, 2013
Get Ready for the 2013 Perseids


Astro Picture of the Day:
August 7, 2013

Source:
What's going on behind that volcano? Quite a bit. First of all, the volcano itself, named Kirkjufell, is quite old and located in western Iceland near the town of Grundarfjörður. In front of the steeply-sloped structure lies a fjord that had just begun to freeze when the above image was taken - in mid-December of 2012. Although quite faint to the unaided eye, the beautiful colors of background aurorae became quite apparent on the 25-second exposure. What makes this image is of particular note, though, is that it also captures streaks from the Geminids meteor shower - meteors that might not have been evident were the aurora much brighter. Far in the distance, on the left, is the band of our Milky Way Galaxy, while stars from our local part of the Milky Way appear spread across the background. This weekend the Perseids meteor shower will peak and may well provide sky enthusiasts with their own memorable visual experiences.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
August 8, 2013

-The Perseid meteor shower is ramping up! It should peak late this Sunday and Monday nights.

-Saturn (magnitude +0.7, in Virgo) glows in the southwest as twilight fades, with Spica 12° to its lower right. As night grows darker look almost as far to Saturn's left for fainter Alpha Librae.

Astro Picture of the Day:
August 8, 2013

Source:
Similar in size and grand design to our own Milky Way, spiral galaxy NGC 3370 lies about 100 million light-years away toward the constellation Leo. Recorded here in exquisite detail by the Hubble Space Telescope's Advanced Camera for Surveys, the big, beautiful face-on spiral does steal the show, but the sharp image also reveals an impressive array of background galaxies in the field, strewn across the more distant Universe. Looking within NGC 3370, the image data has proved sharp enough to study individual pulsating stars known as Cepheids that can be used to accurately determine this galaxy's distance. NGC 3370 was chosen for this study because in 1994 the spiral galaxy was also home to a well studied stellar explosion - a type Ia supernova. Combining the known distance to this standard candle supernova, based on the Cepheid measurements, with observations of supernovae at even greater distances, can reveal the size and expansion rate of the Universe itself.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
August 9, 2013

-Early in twilight, about a half hour after sunset, look very low in the west below Venus for the thin crescent Moon, as shown at right. Binoculars will help.

-NOAA forecastesrs estimate a 65% chance of polar geomagnetic storms on August 10th when one and perhaps two CMEs are expected to hit Earth's magnetic field. The incoming clouds were propelled from the sun by a flurry of erupting magnetic filaments on Aug. 6-7. High-latitude sky watchers should be alert for auroras.

-On August 3rd, Japan launched a robotic spacecraft, the HTV-4, to re-supply the International Space Station (ISS). Last night, Larry Sloss saw the HTV-4 in hot pursuit of the ISS in the twilight skies over Priest Lake, Idaho. Many observers noted "HTV-4 flares" this week. Apparently sunlight is glinting off a flat surface of the spacecraft, briefly raising its luminosity to match that of the much larger ISS. HTV-4 has an interesting payload. Among the 5.4 tons of food, spare parts, and other supplies are Kirobo, a talking robot to join the crew of the ISS, and Firestation, an experiment to study mysterious Terrestrial Gamma-ray Flashes. Docking was scheduled at approximately 4:30 AM EDT on Friday August 9th.

News Posted Today:
August 7, 2013
Under Stress, Asteroids May Be Fragile


Astro Picture of the Day:
August 9, 2013

Source:
Medieval Albrechtsberg castle is nestled in trees near the northern bank of the river Pielach and the town of Melk, Austria. In clearing night skies on August 12, 2012 it stood under constellations of the northern summer, including Aquarius, Aquila, and faint, compact Delphinus (above and right of center) in this west-looking skyview. The scene also captures a bright meteor above the castle walls. Part of the annual perseid meteor shower, its trail points back toward the heroic constellation Perseus high above the horizon in the early morning hours. Entering the atmosphere at about 60 kilometers per second, perseid meteors are swept up dust grains from the tail of comet Swift-Tuttle. Of course, this year's perseid meteors will flash through night skies this weekend.

[igotrhythm]

Re: Terry's Astronomy Thread.



Tangentially relevant. As per the CC 2.5 license, here's the link: http://xkcd.com/1249/

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
August 10, 2013

-The waxing crescent Moon shines well to the left of Venus low in twilight.

-Look far down to Mars's lower left, as dawn brightens, for Mercury (magnitude —1). It's sinking lower every day. Don't confuse Mercury with Procyon, far down to Mars's lower right.

Astro Picture of the Day:
August 10, 2013

Source:
The two bright meteors flashing through this night skyscape from August 7 are part of the ongoing Perseid meteor shower. In the direction indicated by both colorful streaks, the shower's radiant in the eponymous constellation Perseus is at the upper right. North star Polaris, near the center of all the short, arcing star trails is at the upper left. But also named for its pose against the sky, the monastery built on the daunting sandstone cliffs in the foreground is part of Meteora. A World Heritage site, Meteora is a historic complex of lofty monasteries located near Kalabaka in central Greece.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
August 11, 2013

-The annual Perseid meteor shower should be at its most active late tonight and tomorrow night. (The expected peak time, 2 p.m. EDT August 12th, is ideal for the Far East; for North America it splits the difference between the early morning hours of the 12th and 13th.)

-For more information on the Perseids, consult here http://www.skyandtelescope.com/obser...218037521.html

Astro Picture of the Day:
August 11, 2013

Source:
If not perfect, then this spiral galaxy is at least one of the most photogenic. An island universe of about 100 billion stars, 32 million light-years away toward the constellation Pisces, M74 presents a gorgeous face-on view. Classified as an Sc galaxy, the grand design of M74's graceful spiral arms are traced by bright blue star clusters and dark cosmic dust lanes. Constructed from image data recorded in 2003 and 2005, this sharp composite is from the Hubble Space Telescope's Advanced Camera for Surveys. Spanning about 30,000 light-years across the face of M74, it includes exposures recording emission from hydrogen atoms, highlighting the reddish glow of the galaxy's large star-forming regions. Recently, many astronomers are tracking a bright supernova that has been seen in M74.

[Staiain]

Re: Terry's Astronomy Thread.

I'd love to see some meteors oooo

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
August 12, 2013

-The annual Perseid meteor shower should be at its most active late tonight. (The expected peak time, 2 p.m. EDT August 12th, is ideal for the Far East; for North America it splits the difference between the early morning hours of the 12th and 13th.)

-During and after dusk, spot Saturn above the waxing crescent Moon in the southwest. Look lower right of the Moon for Spica. Much higher to their upper right shines Arcturus.

Astro Picture of the Day:
August 12, 2013

Source:
Are asteroids dangerous? Some are, but the likelihood of a dangerous asteroid striking the Earth during any given year is low. Because some past mass extinction events have been linked to asteroid impacts, however, humanity has made it a priority to find and catalog those asteroids that may one day affect life on Earth. Pictured above are the orbits of the over 1,000 known Potentially Hazardous Asteroids (PHAs). These documented tumbling boulders of rock and ice are over 140 meters across and will pass within 7.5 million kilometers of Earth - about 20 times the distance to the Moon. Although none of them will strike the Earth in the next 100 years - not all PHAs have been discovered, and past 100 years, many orbits become hard to predict. Were an asteroid of this size to impact the Earth, it could raise dangerous tsunamis, for example. Of course rocks and ice bits of much smaller size strike the Earth every day, usually pose no danger, and sometimes creating memorable fireball and meteor displays.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
August 13, 2013

-The first-quarter Moon shines in the southwest at nightfall, with Saturn to its right and Antares farther to its left. Quite close to the Moon is Alpha Librae, a wide double star for binoculars. The Moon occults (covers) Alpha Librae for much of South America.

-The Perseid meteor shower is underway. Last night, international observers counted more than 120 meteors per hour from dark sky sites. Sky watchers should remain alert for Perseids during the dark hours between midnight and sunrise as Earth passes through the debris stream of parent comet 109P/Swift-Tuttle. According to NASA's Meteoroid Environment Office, the Perseid meteor -shower produces more fireballs than any other annual shower. Last night, Mike Lewinski of Embudo, New Mexico, photographed "the brightest fireball I've ever seen." It was an impressive Perseid, even though he caught only half of it.

-Want to listen to the meteor shower? Use the spaceweather radio here: http://spaceweatherradio.com/

Astro Picture of the Day:
August 13, 2013

Source:
Where are all of these meteors coming from? In terms of direction on the sky, the pointed answer is the constellation of Perseus. That is why the meteor shower that peaked over the past few days is known as the Perseids - the meteors all appear to come from a radiant toward Perseus. Three dimensionally, however, sand-sized debris expelled from Comet Swift-Tuttle follows a well-defined orbit about our Sun, and the part of the orbit that approaches Earth is superposed in front of the Perseus. Therefore, when Earth crosses this orbit, the radiant point of falling debris appears in Perseus. Pictured above, a composite of 13 early images from this year's Pereids meteor shower shows many bright meteors that streaked through the sky the night of August 11 near Oakland, Ontario, Canada.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
August 14, 2013

-Look for orange Antares lower left of the Moon after dusk, with the other stars of upper Scorpius around it. Near the zenith shines the Summer Star, Vega.

-The Perseid meteor shower, which peaked on August 12-13 with as many as 120 meteors per hour, is slowly subsiding as Earth exits the debris stream of parent comet 109P/Swift-Tuttle. Sky watchers should nevertheless remain alert for meteors tonight between midnight and sunrise. It will take several days for the Perseid rate to drop to zero.

Astro Picture of the Day:
August 14, 2013

Source:
It took three worlds to create this simple image. The first world was the Earth, which was quite prominent. The dividing line running horizontally below the middle separates sea from sky. On this part of the Earth, it was almost nighttime. The second world was the Moon, which was almost invisible. The Moon had its unilluminated half masked by the red sunset glow of Earth's sky. A thin sliver of the new Moon was visible, a crescent that traces the bright curving line. The third world was the Sun, which does not appear directly. All of the light recorded in the image originated from the Sun. The above half-second exposure was taken last week from Anping, Taiwan. A few minutes after this image was taken the Earth had spun just a little bit further - forcing the Moon to follow the Sun into the sea - and the horizon to become dark.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
August 16, 2013

-Antares is lower right of the Moon this evening.

-The US Air Force Space Surveillance System, a.k.a. the "Space Fence," will be shut down on Oct. 1st. This is a result of automatic cuts imposed by the US Congressional budget sequester. The Space Fence is a multi-station radar deployed across the southern USA capable of tracking satellites, space debris, and meteoroids as far as 30,000 km from Earth. This negatively impacts Space Weather Radio as well, which broadcasts echoes from the Space Fence. In October, spaceweather's radio will shift to a new type of meteor radar based on the forward scattering of VHF TV signals.

News Posted Today:
August 14, 2013
Bright Nova in Delphinus


Astro Picture of the Day:
August 15, 2013

Source:
In an astronomical version of the search for the source of the Nile, astronomers now have strong evidence for the origin of the Magellanic Stream. This composite image shows the long ribbon of gas, discovered at radio wavelengths in the 1970s, in pinkish hues against an optical all-sky view across the plane of our Milky Way galaxy. Both Large and Small Magellanic Clouds, dwarf satellite galaxies of the the Milky Way, are seen near the head of the stream at the right. Data from Hubble's Cosmic Origins Spectrograph were used to explore abundances of elements along sitelines to quasars that intersect the stream. The results indicate that most of the stream's material comes from the Small Magellanic Cloud. The Magellanic Stream is likely the result of gravitational tidal interactions between the two dwarf galaxies some 2 billion years ago, the Small Magellanic Cloud losing more material in the encounter because of its lower mass.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
August 16, 2013

-By about 10 p.m. (depending on where you live), W-shaped Cassiopeia is now as high in the northeast as the Big Dipper is in the northwest. Cassiopeia will grow ever more ascendant over the Dipper for the next several months as the seasons turn.

-The nova discovered in Delphinus on Wednesday brightened to magnitude 5.2 in hardly more than 24 hours. Delphinus is conveniently high in the evening sky. The nova is easy to see in binoculars, and it's faintly visible to the naked eye if you have a dark sky.

News Posted Today:
August 15, 2013
New Pulsar Explores Heart of Milky Way



Astro Picture of the Day:
August 16, 2013

Source:
Using a small telescope to scan the skies on August 14, Japanese amateur astronomer Koichi Itagaki discovered a "new" star within the boundaries of the constellation Delphinus. Indicated in this skyview captured on August 15 from Stagecoach, Colorado, it is now appropriately designated Nova Delphini 2013. Sagitta, the Arrow, points the way to the newcomer's location high in the evening sky, not far from bright star Altair and the asterism known to northern hemisphere skygazers as the Summer Triangle. The nova is reported to be easy to spot with binoculars, near the limit of naked-eye visibility under dark skies. In fact, previous deep sky charts do show a much fainter known star (about 17th magnitude) at the position of Nova Delphini, indicating this star's apparent brightness suddenly increased over 25,000 times. How does a star undergo such a cataclysmic change? The spectrum of Nova Delphini indicates it is a classical nova, an interacting binary star system in which one star is a dense, hot white dwarf. Material from a cool, giant companion star falls onto the surface of the white dwarf, building up until it triggers a thermonuclear event. The drastic increase in brightness and an expanding shell of debris is the result - but the stars are not destroyed! Classical novae are believed to recur when the flow of material onto the white dwarf resumes and produces another outburst.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
August 17, 2013

- The waxing gibbous Moon shines in the south after nightfall. Below it is the Sagittarius Teapot, as shown at right.

-Look high to the Moon's upper left for bright Altair. Just above Altair is 3rd-magnitude Tarazed, an orange-red giant star (can you see its tint?) 20 times farther away.

- The nova appears to have peaked a little brighter than magnitude 4.5 on August 16th. It was back down roughly to magnitude 4.8 around 10 p.m. EDT on the 16th (2h August 17th UT).

Astro Picture of the Day:
August 17, 2013

Source: My Camera
The Delphinus Nova last night was visible in binoculars in even the brightest of cities in Canada, including Toronto. This composite image is a 51 picture stack of the Delphinus Nova, taken around 10;47pm EST. I was unable to spot the nova without optical aids, but it was visible through my camera lens. The bright moon had washed out a lot of the fainter objects in this area of the sky, but a satellite decided to nicely frame itself while I was taking pictures. The Nova's magnitude can be found using this link from AAVSO: http://www.aavso.org/lcg/plot?auid=0...=&mean=&vmean=

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
August 18, 2013

-The two brightest stars of summer are Vega, passing overhead soon after dark, and Arcturus shining in the west. Vega is a white-hot type-A star 25 light-years away. Arcturus is an orange-yellow-hot type-K giant 37 light-years distant. Both are much brighter than the Sun. Their color difference is pretty clear to the unaided eye.

-Venus (magnitude –4.0) shines brightly low in the west in evening twilight, far below Arcturus. Look to its left and somewhat higher for much fainter Spica, and further on, Saturn. In a telescope Venus is still small (14 arcseconds) and gibbous (78% sunlit).

Astro Picture of the Day:
August 18, 2013

Source:
Skylab was an orbiting laboratory launched by a Saturn V rocket in May 1973. Skylab, pictured above, was visited three times by NASA astronauts who sometimes stayed as long as two and a half months. Many scientific tests were performed on Skylab, including astronomical observations in ultraviolet and X-ray light. Some of these observations yielded valuable information about Comet Kohoutek, our Sun and about the mysterious X-ray background - radiation that comes from all over the sky. Skylab fell back to earth on 1979 July 11.

[Bluearrowll]

Re: Terry's Astronomy Thread.

What's in the sky tonight?
August 19, 2013

-Look east in early dawn for the next few mornings and spot bright Jupiter. Look lower left of Jupiter for faint Mars. Mars forms the bottom end of a curving line with similarly bright Pollux and Castor (to its upper left). Watch this line straighten out day by day as Mars speeds eastward. It becomes exactly straight on Sunday morning the 25th.

Astro Picture of the Day:
August 19, 2013

Source:
Why would the sky still glow after sunset? Besides stars and the band of our Milky Way galaxy, the sky might glow because it contains either noctilucent clouds or aurora. Rare individually, both are visible in the above time lapse movie taken over Caithness, Scotland, UK taken during a single night earlier this month. First noted in 1885, many noctilucent clouds are known to correlate with atmospheric meteor trails, although details and the origins of others remain a topic of research. These meandering bright filaments of sunlight-reflecting ice crystals are the highest clouds in the Earth's atmosphere. The above video captures not only a variety of noctilucent clouds, but also how their structure varies over minutes. Lower clouds typically appear dark or fast moving. About halfway through the video the clouds are joined by aurora. At times, low clouds, noctilucent clouds, and aurora are all visible simultaneously, each doing their own separate dance, and once - see if you can find it - even with the Big Dipper rotating across the background.