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Friday, April 18 2014 @ 05:51 AM CDT

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The Sun Can Still Remind Us Who’s Boss

NASA Space Placeby Dr. Tony Phillips

In spite of Earth’s protective magnetosphere, solar storms can wreak havoc with Earth satellites and other expensive electronics on the ground.
Click image for larger view.
Grab your cell phone and take a good long look.  It's indispensable, right?  It tells time, surfs the web, keeps track of your appointments and, by the way, also makes phone calls. Modern people can hardly live without one.

One good solar flare could knock it all out.

“In the 21st century, we’re increasingly dependent on technology,” points out Tom Bogdan, director of NOAA's Space Weather Prediction Center in Boulder, Colorado. “This makes solar activity an important part of our daily lives.” Indeed, bad space weather can knock out power systems, telecommunications, financial and emergency services—basically, anything that needs electronics to work. That’s why NOAA is building a new fleet of “space weather stations,” the GOES-R satellites.

“GOES-R will bring our existing fleet of weather satellites into the 21st century,” says Bogdan.  “They're designed to monitor not only Earth weather, but space weather as well.”

NOAA's existing fleet of Geostationary Operational Environmental Satellites (GOES) already includes some space weather capabilities: solar ultraviolet and X-ray telescopes, a magnetometer and energetic particle sensors.  GOES-R will improve upon these instruments and add important new sensors to the mix.

One of Bogdan’s favorites is a particle detector named “MPS-Low,” which specializes in sensing low-energy (30 ev – 30 keV) particles from the sun.

Who cares about low-energy particles? It turns out they can be as troublesome as their high-energy counterparts. Protons and other atomic nuclei accelerated to the highest energies by solar flares can penetrate a satellite’s exterior surface, causing all kinds of problems when they reach internal electronics. Low-energy particles, particularly electrons, can’t penetrate so deeply. Instead, they do their damage on the outside.

As Bogdan explains, “Low-energy particles can build up on the surfaces of spacecraft, creating a mist of charge. As voltages increase, sparks and arcs can zap electronics — or emit radio pulses that can be misinterpreted by onboard computers as a command.”

The Galaxy 15 communications satellite stopped working during a solar wind storm in April 2010, and many researchers believe low-energy particles are to blame. GOES-R will be able to monitor this population of particles and alert operators when it’s time to shut down sensitive systems.

“This is something new GOES-R will do for us,” says Bogdan.

The GOES-R magnetometer is also a step ahead. It will sample our planet’s magnetic field four times faster than its predecessors, sensing vibrations that previous GOES satellites might have missed. Among other things, this will help forecasters anticipate the buildup of geomagnetic storms.

And then there are the pictures. GOES-R will beam back striking images of the sun at X-ray and extreme UV wavelengths. These are parts of the electromagnetic spectrum where solar flares and other eruptions make themselves known with bright flashes of high-energy radiation. GOES-R will pinpoint the flashes and identify their sources, allowing forecasters to quickly assess whether or not Earth is in the “line of fire.”

They might also be able to answer the question, Is my cell phone about to stop working?

The first GOES-R satellite is scheduled for launch in 2015. Check www.goes-r.gov for updates. Space weather comes down to Earth in the clear and fun explanation for young people on SciJinks, http://scijinks.gov/space-weather-and-us.

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
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Astronomy From Your Back Yard - 7/14 to 7/20 2010

By Dave Grosvold

Wednesday evening will be a good time to look for a thin crescent Moon below Venus in the fading western sky. At 9:00 PM CDT, the waxing crescent Moon will be about 7° to the lower left of brilliant Venus. Also on Wednesday evening, look for the International Space Station (ISS) to make a fairly bright overhead pass starting at 9:31 PM CDT. Look for it low in the NW, and then watch it swing up to an altitude of 57° in the SW before fading into the horizon in the SSE.

On Thursday evening, July 15th, the Moon is farther left of Venus. Now they both appear to be close to the same altitude above your horizon. Also on Thursday, Saturn's largest satellite, Titan, is at its eastern elongation from the planet this evening, and should be easy to pick out in a small telescope at high power. By Friday evening, the Moon has moved far to the left of Mars and Saturn.

Iridium 25 makes a bright pass overhead on Saturday evening at 9:41 PM CDT. Look for it to flare to magnitude -6 at an altitude of only 14° above the horizon in the NNW. There are several more Iridium Flares occurring this week, all in the early morning hours. You can find out the times and directions of Iridium Flares and ISS passes at Heavens Above.

Look for the bright stars Vega, Deneb, and Altair, the apices of the Summer Triangle in the eastern sky soon after dusk. This week, the Summer Triangle asterism will slightly higher in the sky than it was at the same hour last week. There are several Messier objects to be found within the Summer Triangle. These are wonderful jewels that can be captured by a pair of binoculars or a small-to-medium (6” - 10”) telescope.

If you want to learn more about these jewels of the night sky, check out this Astronomy From Your Backyard PDF file. If you want to actually see these objects in a telescope, come to the AOAS Star Party this Saturday, July 17th at Lake Fort Smith State Park, weather permitting. We will be holding a presentation in the Visitor Center at 8:00 PM, CDT, and then we'll move to the boat ramp area where we will have club members and their telescopes set up for public viewing. Come on out and enjoy the night sky!
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Astronomy From Your Back Yard - 7/7 to 7/13 2010

By Dave Grosvold

This week, look for Venus shining bright in the western sky at dusk. Venus moves lower in the sky every week as the year marches on. In the evening on Saturday, July 10th, look for Regulus straight below Venus. Regulus is 150 times dimmer than Venus, and is very close to it — only about 1.2°.

On Sunday, July 11th, the New Moon occurs exactly at 2:40 PM. CDT. Mercury and the thin crescent Moon are far to the lower right of Venus in early evening Sunday, and visible only at locations with a clear view to the west. Catching them together will require some searching and the aid of a pair of binoculars. Sunday evening, Mercury and the Moon will be about 10° apart at dusk.

After Sunday, the waxing crescent Moon moves along a diagonal line south of the one described by Mercury, Venus, Mars, and Saturn. The planets lie on, or very close to the ecliptic, which is the plane of the Solar System. Watch each evening, and you will see the Moon higher and farther south than the night before, while the Crescent grows fatter until it reaches First Quarter at the end of next week.

With the darker skies due to the New Moon, this week is also a great time to look for objects in the deep sky. Deep sky objects are objects in the night sky other than individual stars and the planets of our own Solar System. The deep sky is rich with star clusters, various type of nebulae, galaxies, and supernovae remnants. In mid-summer, Scorpius is high in the south after dusk, and the Scorpion's Tail is only visible for a short window of time during this part of the year.

Scorpius is one of the most recognizable constellations in the sky, since it so closely resembles its namesake. The Scorpion's Tail is an area rich in deep sky objects, and is a great place to spend some time browsing with a telescope or binoculars. Look for Messier objects M7, the Ptolemy Cluster, and M6, the Butterfly Cluster, in the area above and to the east of the tip of the Scorpions Tail. A bit higher, in the body of the Scorpion, lies M4, a brilliant globular cluster, and one of the jewels of the night sky.

There are also many objects from the NGC, or New General Catalogue visible in the Scorpion's Tail as well. Open clusters NGC 6383, NGC 6425, NGC 6416, NGC 6242, NGC 6281, NGC 6231, NGC 6322, and NGC 6250 are in the Tail, as well as globular clusters NGC 6441, NGC 6338, and NGC 6541. Click this link for a finder chart.

This time of year, the Summer Triangle is prominent in the eastern sky about an hour after dusk. This asterism is made up of three bright stars from separate constellations: Vega, in the constellation Lyra is at the top of the triangle. Deneb, in Cyngus, is farther down on to the left (astronomers say it is North of Vega.) And finally, Altair, in the constellation Aquila, is even farther down from Vega to the right (or South for astronomers.)
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Astronomy From Your Back Yard - 6/30 to 7/6 2010

By Dave Grosvold

You can spot 1 Ceres any night this week as it moves through the constellation Ophiuchus (pronounced Oh-FEE-eh-kuss) with binoculars or a small scope. Ceres, the largest astronomical body in the asteroid belt, was discovered on Jan 1, 1801 by Giuseppe_Piazzi. After having been designated as a planet in 1801, Ceres enjoyed that elevated status for only a short time, until a number of other small objects were discovered in the space between Jupiter and Mars. In 1802, William Herschel coined the term asteroid ("star-like") to refer to these small bodies — bodies that were too much like stars to be planets, but wandered in the same way.

Ceres was reclassified as a dwarf planet after the status of Pluto was debated and demoted in 2006. Ceres is now the smallest dwarf planet in the Solar System, rather than the largest asteroid, but remains designated formally as 1 Ceres since it was the first such body to be discovered. 1 Ceres is currently still as bright as magnitude 7.3, and can be located by using the finder chart. The best way to distinguish Ceres from the background stars is to observe it on several different nights. The obvious movement from night to night compared to the background will give it away.

Some very bright Iridium Flares may be visible this week! On Wednesday evening, June 30th, Iridium 26 will flare to a magnitude of -3.0 in the WSW at 11:36 PM CDT. Look for it at an altitude of 19° above the horizon. Any time we refer to magnitude in this article, we are actually referring to apparent magnitude, which is how the brightness of an object appears to observers on Earth, as opposed to its intrinsic brightness, or absolute magnitude.

In the early morning hours of Thursday, July 1st, you may be able to catch Iridium 12 flaring to a very bright magnitude -7.0 at 4:16 AM CDT, 27° above the horizon in the ESE. Iridium 23 also flares to a brilliant -7.0 magnitude on Thursday evening at 11:30 PM CDT. Look for it at an altitude of 19° in the WSW. A magnitude of -7.0 is several orders of magnitude brighter than Venus at its brightest! Venus only reaches -4.67 when it is in it s crescent phase and closest to Earth. So these flares will be very bright.

Another pair of bright Iridium Flares appropriately occur on Independence Day, Sunday, July 4th. At 4:04 AM CDT in the ESE, look for Iridium 91 at 23° above the horizon, flaring to a -4.0 magnitude. Again at 11:21 PM in the WSW, Iridium 22 hits magnitude -6.0 at altitude 18°.

Finally, look for Iridium 56 and Iridium 41 in the early morning on Tuesday, July 6th flaring to -5.0 and -7.0 in the SE at 28° and the E at 12° respectively. Iridium 56 will flare at 3:54 AM CDT and Iridium 41 at 5:14 AM, CDT.

The International Space Station (ISS) makes only one pass low in the NNW this week, starting at 11;56 PM CDT on Monday, July 5th. The ISS starts at altitude 10° in the NNW, then barely swings up to a maximum altitude of 11° in the NNW, and quickly fades from view. The ISS will only reach a maximum brightness of magnitude 0.0, or just slightly brighter than Vega in the constellation Lyra at magnitude 0.03.

Venus closes in on Regulus in the constellation Leo day by day, while Mars closes in on Saturn. The diagonal line of Saturn, Mars, Regulus, and Venus is shrinking every day. The three planets will be very close together low in the west at sunset by early August. A telescope shows Saturn's Rings a mere 2° from edge-on right now, but the rings will continue to increase their tilt with respect to Earth over the next 15 years.

The waning gibbous Moon rises around midnight on Friday, July 2nd, and about 45 minutes later, Jupiter rises beneath it. Jupiter is slowly working its way back into the evening sky, and should be a bright Evening Star by mid-autumn, while Venus sinks into the glare of the autumn sunset

As night falls this time of year, look for red Arcturus high in the southwest straight above Spica in the constellation Virgo. The kite shape of the rest of the constellation Boötes extends straight up from Arcturus. By the way, Boötes is pronounced "Bo-OH-teez" or "Bo-OH-tiss," not "BEWT-eez", as some might assume. Pronunciation of constellation names is open to debate, but there are several accepted pronunciations for most constellations. If you're interested, See the Sky & Telescope magazine web site for a Pronunciation Guide.
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Astronomy From Your Back Yard - 6/23 to 6/29 2010

By Dave Grosvold

The waxing gibbous Moon lies in the head of the constellation Scorpius after dusk on Wednesday evening. Reddish-orange Antares is still bright, riding below and to the Moon's lower left. On Thursday evening, Antares and the upper part of Scorpius lie to the right of the nearly full Moon after dusk.

June's Full Moon occurs on Saturday morning at 6:31 AM which will be after daylight begins. The first Full Moon of June is known as the Strawberry Moon, so named by the Algonquin tribe because the relatively short season for harvesting strawberries comes each year during the month of June It is also known as the Flower Moon or Planting Moon.

Observers in most of North America will also be able to witness a partial Lunar Eclipse on Saturday morning when the Moon will be setting in Sagittarius as the Sun rises. For observers in our neck of the woods, the Moon will be entering the penumbra at around 4:30 AM, and then will enter the actual eclipse phase by 5:17 AM. For observers in Arkansas, the Moon will be below the horizon before it reaches the maximum point of the eclipse. The image at left shows the Moon just starting to enter the umbra as it begins to set at 5:20 AM CDT.

Venus is in the constellation Cancer at magnitude -4.0 and is still the bright Evening Star, shining in the west-northwest during and just after twilight this week. While Venus sinks in the west, Mars shines at magnitude +1.3 to Venus' upper left, a match in brightness for Regulus in Leo. The contrast in color between reddish Mars and blue-white Regulus is obvious to observers at darker-sky viewing sites. Regulus is falling farther to Mars' lower right each evening. The star to the upper right of Mars and Regulus is Gamma Leonis, which is only a little dimmer than these two.

Jupiter is now rising around 1:00 AM CDT this week along with the constellation Pisces, and shines high in the southeast before dawn. Nothing else in the sky at that time of night is as bright as Jupiter at magnitude -2.28. Jupiter's Great Red Spot is still free of the missing South Equatorial Belt for telescopic observers.

Saturn glows in the south west during evening, to the upper left of Mars. The diagonal line of Saturn, Mars, Regulus, and Venus, is shrinking; the three planets will bunch up low in the sunset in early August. This week right after dusk, you can catch Saturn, Mars, Regulus, Venus, Praesepe (the Beehive Cluster,) and Pollux in a single diagonal line drawn down the western sky.

Saturn's Rings are tilted 2° from edge-on in a telescope. Note the thin black shadow-line that the rings cast on Saturn's globe. The tilt of the rings will steadily increase over the next 15 years so that we can see more and more of the rings. As they tilt farther, observers with small telescopes will be able to see the Cassini Division, a thin dark band in the rings first observed by Giovanni Cassini in 1875.
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Black Holes No Joke

NASA Space Placeby Dr. Tony Phillips

Laser Interferometer Gravitational-wave Observatory in Livingston, Louisiana. Each of the two arms is 4 kilometers long. LIGO has another such observatory in Hanford, Washington.
Click image for larger view.
Kip Thorne: Why was the black hole hungry?

Stephen Hawking: It had a light breakfast!

Black hole humor—you gotta love it. Unless you’re an astronomer, that is. Black holes are among the most mysterious and influential objects in the cosmos, yet astronomers cannot see into them, frustrating their attempts to make progress in fields ranging from extreme gravity to cosmic evolution.

How do you observe an object that eats light for breakfast?

“Black holes are creatures of gravity,” says physicist Marco Cavaglia of the University of Mississippi. “So we have to use gravitational waves to explore them.”

Enter LIGO—the NSF-funded Laser Interferometer Gravitational-wave Observatory. According to Einstein’s Theory of General Relativity, black holes and other massive objects can emit gravitational waves—ripples in the fabric of space-time that travel through the cosmos. LIGO was founded in the 1990s with stations in Washington state and Louisiana to detect these waves as they pass by Earth.

“The principle is simple,” says Cavaglia, a member of the LIGO team. “Each LIGO detector is an L-shaped ultra-high vacuum system with arms four kilometers long. We use lasers to precisely measure changes in the length of the arms, which stretch or contract when a gravitational wave passes by.”

Just one problem: Gravitational waves are so weak, they change the length of each detector by just 0.001 times the width of a proton! “It is a difficult measurement,” allows Cavaglia.

Seismic activity, thunderstorms, ocean waves, even a truck driving by the observatory can overwhelm the effect of a genuine gravitational wave. Figuring out how to isolate LIGO from so much terrestrial noise has been a major undertaking, but after years of work the LIGO team has done it. Since 2006, LIGO has been ready to detect gravitational waves coming from spinning black holes, supernovas, and colliding neutron stars anywhere within about 30 million light years of Earth.

So far the results are … nil. Researchers working at dozens of collaborating institutions have yet to report a definite detection.

Does this mean Einstein was wrong? Cavaglia doesn’t think so. “Einstein was probably right, as usual,” he says. “We just need more sensitivity. Right now LIGO can only detect events in our little corner of the Universe. To succeed, LIGO needs to expand its range.”

So, later this year LIGO will be shut down so researchers can begin work on Advanced LIGO—a next generation detector 10 times more sensitive than its predecessor. “We’ll be monitoring a volume of space a thousand times greater than before,” says Cavaglia. “This will transform LIGO into a real observational tool.”

When Advanced LIGO is completed in 2014 or so, the inner workings of black holes could finally be revealed. The punchline may yet make astronomers smile.

Find out more about LIGO at http://www.ligo.caltech.edu/. The Space Place has a LIGO explanation for kids (of all ages) at http://spaceplace.nasa.gov/en/kids/ligo, where you can “hear” a star and a black hole colliding!

This article was provided by the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
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Astronomy From Your Back Yard - 6/2 to 6/8 2010

Backyard AstronomyBy Dave Grosvold

From our vantage point right now in the evenings, the Big Dipper asterism is upside down. Look above the three stars of the handle for Canes Venatici, the Hunting Dogs. This week, you can catch several bright galaxies in this area high overhead in binoculars. These Messier galaxies, named for the first astronomer who cataloged them, Charles Messier (pronounced ME-see-ay,) are challenging, but attainable. Grab a chaise lounge chair, a pair of binoculars, lay back, and spend some time scanning this area. It’s easiest to hunt out M63, M94, and M106, but M51, the Whirlpool Galaxy, is the most famous of this group, and the most difficult to spot due to its low surface brightness. Consider yourself more than a beginning observer if you can bag this one. You can view a finder chart for these galaxies by clicking on the chart thumbnail image.

Starting on Thursday evening, Mars is within 3° of Regulus in the constellation Leo. They're almost the same brightness, and make a striking color-contrast pair high in the west after dark. Follow them each evening until they reach conjunction on Sunday, June 6th, when they will be only 0.8° apart.

On Friday evening, June 4th, the Moon reaches Last Quarter at 5:13 PM CDT. The Moon doesn’t rise Friday evening until 1:00 AM or so, which gives observers a few hours of dark sky observing before it comes up and washes the sky in moonglow.

The bright Evening Star shining in the west-northwest during and after twilight is Venus. The twins of Gemini, Pollux and Castor, are above it. Venus is about as high in twilight as it will get this year in this part of the world. Venus is still a small gibbous disk in a telescope. It's so dazzlingly bright that you'll have the best telescopic views of it in the bright blue sky before sunset when the contrast is lower. After sunset, you may want to use a polarizing or neutral density filter to cut the glare. Later in the summer, Venus will be closer to Earth, and easier to view when larger and in its crescent phase.

Also this week, the faint comet C/2009 R1 (McNaught) is nearing its period of best visibility in mid-June at magnitude 7.8. Look for it low in the northeast just before the start of dawn with binoculars or a small telescope.

If you’re up to it, Saturday and Sunday morning just before dawn is a good time to catch the Moon and Jupiter rising together in the eastern sky. Just below the Circlet of Pisces, Jupiter climbs higher each week in the east-southeast during the early dawn hours. Don’t forget to try looking for Jupiter's Great Red Spot while the South Equatorial Belt is nearly invisible. Mercury can also be found very low in the east at dawn. Look for it with binoculars, below Jupiter and to the lower left.

Saturn glows high in the southwest during the evening this week. In a telescope, Saturn's rings are tilted a mere 1.7° from edge-on, their minimum tilt for the next 15 years. Look for the thin black shadow-line cast by the rings across Saturn's bright globe.

The ISS (International Space Station) will make several overhead passes during the early morning hours this week. The brightest of these will occur on Sunday and Tuesday mornings, both near magnitude -3.5. On Sunday morning, look for the ISS to rise in the SW at 5:31 AM, and pass overhead at a maximum altitude of 83° at 5:33 AM in the SE before setting in the NE at 5:36 AM. A bit earlier on Tuesday morning, the ISS will rise at 4:44 AM in the SW, reach a maximum altitude of 82° in the SE at 4:45 AM, and then set in the NE at 4:48 AM. The ISS will also make passes on Saturday and Monday mornings but will only reach a maximum brightness of magnitude -1.3 on these passes.

There will also be several bright Iridium Flares this week in the early morning hours, with several reaching fairly bright magnitudes. But if you’re out and about in the evening on Thursday, June 3rd, try to catch Iridium 18 at an altitude of 63° in the eastern sky at 9:06 PM.

Check the Heavens Above website for times and positions of Iridium Flares, the ISS, and other satellites in the nighttime sky. You can also view a current finder chart for comet C/2009 R1 (McNaught) on the Heavens Above website.
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Astronomy From Your Back Yard - 5/26 to 6/1 2010

By Dave Grosvold

The Sun in hydrogen-alpha light
After an unusually long solar minimum, activity on the Sun is picking up, with sunspots and other magnetic phenomena frequency increasing. Solar activity should continue to increase until the next solar maximum, which is expected in 2013.

Solar images taken in red hydrogen-alpha light reveal much more information than the while-light images you might see through a normal solar filter. Hydrogen-alpha (Hα) light is a specific red wavelength of light produced by the emissions of the hydrogen fusion process in stars. Astronomers use a special filter that allows only light of this wavelength to pass through and be recorded either on film or by digital sensors. You might want to learn more about the Sun at the Solar and Heliopsheric Observatory (SOHO) site.

Caution - Never look directly at the Sun! Always understand and use the proper filters and equipment before attempting to view sunspots or other solar phenomena.

The “Pillars of Creation”
Vega, in the constellation Lyra the Lyre, now shines brightly in the east-northeast after dark. Vega is the first star of the Summer Triangle asterism to appear above the horizon each night starting in the Spring. Deneb, the second of the three apices of the Summer Triangle, can be found about two or three fist-widths to Vega's lower left. Deneb is in the constellation Cygnus, the Swan. Being the third star of the Summer Triangle, in the constellation Aquila, the Eagle, Altair rises late in the evening significantly farther to Vega's lower right. Aquila is the home of the Eagle Nebula (M16), the site of the “Pillars of Creation” image, made famous by the Hubble Space Telescope.

The Full Moon occurs at 6:07 PM CDT,on Thursday, May 27th. Look for ruddy Antares just 1° or 2° to the Moon's lower right, as well as other surrounding stars of the constellation Scorpius. The Moon's glare will be bright; binoculars will give the best view. During the course of the evening, watch the Moon move with respect to these background stars.

Venus is less than 3/4° from the 3rd-magnitude star Mebsuta (Epsilon Geminorum) Thursday and Friday evening. Look carefully, because Venus is 600 times brighter than Mebsuta.

These comparison photos of Jupiter taken by amateur astronomer Anthony Wesley and posted by The Planetary Society show the planet's lost Southern Equatorial Belt on May 9, 2010.
Ceres, the largest asteroid and first to be discovered, is passing close by the Lagoon Nebula (M8), in Sagittarius this week. Ceres is magnitude 7.5, well within binocular range. The Lagoon reaches a good observing altitude in the south-southeast by about 1:00 AM. Ceres will be closest to the Lagoon on the night of June 1st.

Comet C/2009 R1 (McNaught) is nearing its period of best visibility, low in the east-northeast just before the start of dawn. Since it is faint, you'll need to bring a telescope or (perhaps) binoculars to see it. Check out the finder chart at the Heavens Above web site.

Jupiter is below the Circlet of Pisces, an asterism in the Pisces constellation, all this week. Jupiter shines in the east-southeast in the early morning hours of dawn, climbing higher each week. Jupiter has lost its South Equatorial Belt (SEB) in recent weeks, which is a very rare event. A lucky break, because the disappearing belt makes the Great Red Spot much easier to see in small telescopes.
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Ancient Supernova Riddle, Solved

NASA Space Place

Left-over cloud from the Tycho supernova, witnessed by Tycho Brahe and other astronomers over 400 years ago. This image combines infrared light captured by the Spitzer Space Telescope with x-rays captured by the Chandra X-ray Observatory, plus visible light from the Calar Also Observatory in Spain.
Click image for larger view.
Australopithecus squinted at the blue African sky. He had never seen a star in broad daylight before, but he could see one today. Was it dangerous? He stared for a long time, puzzled, but nothing happened, and after a while he strode across the savanna unconcerned.

Millions of years later, we know better. That star was a supernova, one of many that exploded in our corner of the Milky Way around the Pliocene era of pre-humans. Australopithecus left no records; we know the explosions happened because their debris is still around. The Solar System and everything else within about 300 light-years is surrounded by supernova exhaust — a haze of million-degree gas that permeates all of local space.

Supernovas are dangerous things, and when one appears in the daytime sky, it is cause for alarm. How did Earth survive? Modern astronomers believe the blasts were too far away (albeit not by much) to zap our planet with lethal amounts of radiation. Also, the sun’s magnetic field has done a good job holding the hot gas at bay. In other words, we lucked out.

The debris from those old explosions has the compelling power of a train wreck; astronomers have trouble tearing their eyes away. Over the years, they’ve thoroughly surveyed the wreckage and therein found a mystery--clouds of hydrogen and helium apparently too fragile to have survived the blasts. One of them, whimsically called “the Local Fluff,” is on the doorstep of the Solar System.

“The observed temperature and density of the Fluff do not provide enough pressure to resist the crushing action of the hot supernova gas around it,” says astronomer Merav Opher of George Mason University. “It makes us wonder, how can such a cloud exist?”

NASA’s Voyager spacecraft may have found the answer.

NASA's two Voyager probes have been racing out of the solar system for more than 30 years. They are now beyond the orbit of Pluto and on the verge of entering interstellar space. “The Voyagers are not actually inside the Local Fluff,” explains Opher. “But they are getting close and can sense what the cloud is like as they approach it.”

And the answer is….

“Magnetism,” says Opher. “Voyager data show that the Fluff is strongly magnetized with a field strength between 4 and 5 microgauss. This magnetic field can provide the pressure required to resist destruction.”

If fluffy clouds of hydrogen can survive a supernova blast, maybe it’s not so surprising that we did, too. “Indeed, this is helping us understand how supernovas interact with their environment—and how destructive the blasts actually are,” says Opher.

Maybe Australopithecus was on to something after all.

Opher’s original research describing Voyager’s discovery of the magnetic field in the Local Fluff may be found in Nature, 462, 1036-1038 (24 December 2009). The Space Place has a new Amazing Fact page about the Voyagers’ Golden, with sample images and sounds of Earth. After all, just in case one of the Voyager’s ever meets up with ET, we will want to introduce ourselves. Visit http://spaceplace.nasa.gov/en/kids/voyager.
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Astronomy From Your Back Yard - 5/12 to 5/ 18 2010

By Dave Grosvold

If the weather is clear, backyard astronomers will have an opportunity to catch a glimpse of a New Moon just a few hours old this Friday evening, May 14th. Find a place with a clear western horizon with no obstructions, and grab a pair of binoculars.
Look to the west-northwest right after sunset (from about 8:00 PM to 8:30 PM) below Venus and you will see the very thinnest sliver of a waxing crescent Moon. Many intermediate and advanced amateur astronomers have competitions to see who can spot the youngest crescent Moon just after New Moon. This month, New Moon occurred at 8:05 PM CDT on Thursday, May 13th.

Any clear evening this week, look for Saturn and Mars on opposite sides of the constellation Leo in the south-southwestern sky. These two planets dominate the sky most of the spring and summer this year. You should be able to spot Saturn’s moons in a larger pair of binoculars (10 x 70) or small telescope (3 inch or larger.)

If the weather is clear, The International Space Station (ISS) is also visible several times this week. The ISS makes magnitude -2.2 and brighter passes overhead every evening Friday through Monday. The table at the bottom of this article shows the times, altitudes, magnitudes, and directions of these passes. You can check http://www.heavens-above.com for additional passes and times.

You should also able to spot several bright Iridium Flares this week. On Friday, May 14th at 10:30 PM CDT, Iridium 40 passes to the ENE (azimuth 70°) at an altitude of 33°, with a magnitude of -4. Astronomers refer to azimuth (Abbr: Az.) and altitude (Abbr: Alt.) instead of direction and height, but you can easily remember that azimuth is the same as the bearing on a compass, so az. 0° is North, Az. 90° is East, Az. 180° is South, and Az. 270° is West. When astronomers refer to altitude, Alt. 0° is at the horizon and Alt. 90° at the zenith (the zenith is the highest spot in the sky at any point in time, that is, directly overhead.) So that means Alt. 45° is halfway up the sky from the horizon to the zenith.

Saturday morning, May 15th at 4:08 AM CDT, Iridium 60 will pass to the ESE (Az. 111°,) at Alt. 17° above the horizon, but it will be bright, at magnitude -6. That same Saturday evening at 8:49 PM CDT, Iridium 54 passes high overhead in the E (Az. 97°) at Alt. 66°. Iridium 54 will be almost as bright as Iridium 60 at magnitude -5.

Monday morning, May 17th, at 4:05 AM CDT, Iridium 90 passes low in the ESE (Az. 114°) at Alt. 19°, magnitude -4. Then on Tuesday, May 18th, at 3:58 AM CDT, Iridium 59 makes a bright appearance low in the ESE (Az. 116°) at Alt. 16°, at a magnitude of -6. Several other dim Iridium Flares will occur during the week as well. Again, you can check the times and locations at http://www.heavens-above.com.

On the morning of May 16th, look for Jupiter and Uranus to rise together, within 3° of each other on the eastern horizon at 5:00 AM CDT. Uranus is hard to spot, and may only be visible in binoculars or a small telescope, depending on your location. They will continue to rise closer together until they get within 0.5° of each other in early June.

International Space Station Visibility — May 12 - May 18
DateMagStartMaximumEnd
TimeAlt.Az. TimeAlt.Az. TimeAlt.Az.
14 May -2.5 21:42:35 10° NW 21:45:25 41° NE 21:45:52 38° ENE
15 May -2.2 22:07:18 10° WNW 22:09:41 39° WSW 22:09:41 39° WSW
16 May -2.6 20:56:50 10° NW 20:59:40 44° NE 21:02:03 13° ESE
17 May -2.4 21:21:31 10° WNW 21:24:19 40° SW 21:25:58 20° SSE

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