Monday, August 23, 2010

Jupiter Fireball

Jupiter is becoming quite popular planet...for impacts, that is. On August 20 at 18:22 UTC, two amateur astronomers in Japan independently recorded an apparent impact on Jupiter. The first report came from Masayuki Tachikawa of Kumamoto city.

Masayuki Tachikawa of Kumamoto city was first to report the event. Soon after Tachikawa made his report, Tokyo amateur astronomer Aoki Kazuo discovered that he also had recorded the fireball.

The above image was recorded by amateur astronomer Masayuki Tachikawa from Kyushu. The image was recorded using a webcam attached to a six-inch f/7.3 refractor telescope. This version of the image, with the added arrow graphic, was posted by Japan television station KYODO.

The separation between the two observing locations, approximately 800 km, rules out the possibility that the event took place near Earth and reinforces the association of the fireball with Jupiter. The most likely explanation for the event is that a small comet or asteroid hit the gas giant.

The August 20 impact was the third time in only 13 months that amateurs detected impacts on Jupiter. The earlier events occurred on July 19, 2009 and June 3, 2010. The July 19 impact is now thought to be caused by an asteroid about 500 meters (1,600 feet) wide. The resulting impact in the cloud layer was approximately the size of the Pacific Ocean. The June 3 impact was reported by Australian amateur Anthony Wesley, who was at the time watching live video feed from his telescope. Wesley's observation was confirmed by amateur Christ Go, who was taking video from his telescope in the Philippines. Unlike the July 2009 event, the impact from June 3 of this year left no visible scar or debris in the clouds, causing astronomers to be uncertain as to the actual depth of the impact penetration.

In 1994, Comet Shoemaker-Levy 9 broke into more than 20 pieces and pelted Jupiter with a string of impacts. At the time, astronomers estimated that cometary impacts could occur on Jupiter every 50 to 250 years.

Because Jupiter is receiving impacts more frequently, researchers are rethinking their estimates of Jupiter impact rates. In addition, many researchers are calling for a global network to monitor Jupiter around the clock in order to measure the Jupiter impact rate.

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Sunday, August 15, 2010

Perseids Afterglow and U.S. Priorities for the Next Decade

Perseids Afterglow

The peak of the Perseid meteor shower may be past, but there is still plenty to see before this shower completely fades away for another year. If you missed the peak, here are some of the highlights which have been documented on the Web:

U.S. Priorities for the Next Decade

On Friday, August 13, the National Research Council (NRC) held a briefing to review their report identifying the highest-priority research activities for U.S. astronomy and astrophysics in the next decade. This is the sixth decadal survey of the NRC and it states that it will "set the nation firmly on the path to answering profound questions about the cosmos." The report prioritizes proposed activities based on their ability to advance science in key areas, and for the first time also takes into account factors such as risks in technical readiness, schedule, and cost.

The report identifies space- and ground-based research activities in three categories: large, midsize, and small. The large space activities are those exceeding $1 billion. The top priority in this category is an orbital observatory called the Wide-Field Infrared Survey Telescope (WFIRST). It is expected that this space telescope would help settle fundamental questions about the nature of dark energy, determine the likelihood of other Earth-like planets over a wide range of orbital parameters, and survey our Milky Way galaxy and others. The ground-based large-scale initiatives are those that that exceed a budget of $135 million. The first priority of these is the Large Synoptic Survey Telescope (LSST), a wide-field optical survey telescope that would observe more than half the sky every four nights, and address diverse areas of study such as dark energy, supernovae, and time-variable phenomena.

The recommended research activities are encapsulated by three science objectives: deepening understanding of how the first stars, galaxies, and black holes formed, locating the closest habitable Earth-like planets beyond the solar system for detailed study, and using astronomical measurements to unravel the mysteries of gravity and probe fundamental physics.

Along with WFIRST, other priorities in the large-scale space category recommended in the report are an augmentation to NASA’s Explorer program, which supports small- and medium-sized missions that provide high scientific returns; the Laser Interferometer Space Antenna (LISA), which could enable detection of long gravitational waves or "ripples in space-time"; and the International X-Ray Observatory, a large-area X-ray telescope that could transform understanding of hot gas associated with stars, galaxies, and black holes in all evolutionary stages.

Other recommended ground-based research projects include the formation of a Midscale Innovations Program within the NSF, which would fill a funding gap for compelling research activities that cost between $4 million and $135 million. In addition, the report recommends participation in the U.S.-led international Giant Segmented Mirror Telescope, a next generation large optical telescope that is vital for continuing the long record of U.S. leadership in ground-based optical astronomy. The next priority is participation in an international ground-based high-energy gamma-ray telescope array.

For midsize space-based activities, the first priority is the New Worlds Technology Development Program, which lays the scientific groundwork for a future mission to study nearby Earth-like planets. Top priority for ground-based midsize research is the Cerro Chajnantor Atacama Telescope (CCAT), which would provide short wavelength radio surveys of the sky to study dusty material associated with galaxies and stars.

Research priorities were selected through an extensive review that included input from nine expert panels, six study groups, and a broad survey of the astronomy and astrophysics community. With the help of an outside contractor, the committee developed independent appraisals of the technical readiness and schedule and cost risks. In addition, the survey reassessed projects that were recommended in past surveys but not formally started.

The research recommendations represent a cohesive plan with realistic budgetary scenarios, the report says, with ranges based on current projected budgets for NASA, NSF, and the U.S. Department of Energy -- the agencies largely responsible for funding and implementing the research activities. It also identifies smaller, unranked research initiatives to augment core fundamental research. An independent standing committee should regularly advise the agencies on strategy and progress of the projects and produce annual reports.

The report notes that astronomical research continues to offer significant benefits to the nation beyond astronomical discoveries by capturing the public's attention and promoting general science literacy and proficiency. In addition, the research serves as a gateway to science, technology, engineering, and mathematics careers, and a number of important and often unexpected technological breakthroughs. The report makes several recommendations to improve astronomy and astrophysics education and calls for more U.S. participation in international research projects.

Read the full report is available here:
http://www.nap.edu/catalog.php?record_id=12951

See the archived webcast is available here:
http://www.tvworldwide.com/events/nas/100813/

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Monday, August 09, 2010

2010 Perseid Meteor Shower Underway


The Perseid meteor shower is one of the three best annual showers, the other two being the Orionid shower, which peaks around October 21, and the Geminid shower, which peaks around December 13.


This image shows a multicolored, 2009 Perseid meteor passing just to the left of the Milky Way. Image Credit: Mila Zinkova. Permission granted to display the image here.

Perseid meteors may be visible from July 25 through Aug. 21 with the peak on Thursday, August 11/Friday, August 12. This is a reliable shower, giving consistent rates each year. During its maximum (August 12/13) the meteor hourly rate averages 50 to 68, and sometimes higher. The meteors enter the atmosphere at about 59 km/second and are yellow in color. The Perseid shower occurs each year when Earth passes through the debris trail of Periodic Comet Swift-Tuttle, also called Comet 1862 III, discovered on July 16, 1862 by Lewis Swift and then independently discovered three days later by Horace Tuttle. Perseid meteors will appear to originate from a point in the constellation of Perseus (Right Ascension 03hrs 04min, Declination +58°).

Meteoroid, Meteor and Meteorite

The terms meteor, meteorite and meteoroid are confusing to many, and with good reason. They all refer to the same object, but under different circumstances. Let us first examine the origin of these terms. The word meteor comes from the Greek word meteoron, meaning astronomical phenomenon, or something in the heaven above. This meaning can be understood when we consider that meteorology is the science dealing with the atmosphere and its phenomenon. In its most literal sense, anything that we may see in the sky could be called a meteor, whether it be a thunder cloud, a supernova or a UFO. For the purpose of sanity, we shall confine its usage to relatively small bodies which drift through space, fall into Earth's atmosphere, and sometimes reach the ground.

A meteoroid is a relatively small object, smaller than an asteroid or minor planet, drifting through space in orbit around the Sun. Bits smaller than grains of sand are sometimes called micrometeoroids. A meteor is the effect produced as the meteoroid plows into our atmosphere and streaks across the sky. A glowing trail, sometimes called a train, is created to mark the path of the meteoroid as it falls. When a meteoroid, or a fragment of it, reaches the ground, it is called a meteorite. These may be found, dug up, held, and examined. The only way to hold a meteoroid is either to float with it in space or fall with it through the sky!

Many meteoroids are the size of salt or sugar grains and most are no bigger than grains of rice, though some can be the size of giant boulders weighing several tons. As the meteoroids enter Earth's atmosphere, at speeds ranging from 11 to 72 kilometers (7 to 45 miles) per second, their surfaces collide with the atoms and molecules of the atmosphere. These collisions break loose material from their surface and also break up the atoms and molecules of both the meteoric material and the atmosphere into charged particles. The ionized atoms are excited and begin to glow 50 to 75 miles up. These glowing tubes that the meteoroids create as they pass are called trails or trains. Some meteor trails are short, and some are long -- spanning 20 degrees or more across the sky. Most trails are white, blue, or yellow, but some can be red or even green. These ionized trails also show as reflections on radar. Astronomers have used radar since 1945 to record the rate of meteors that fall. Radar observations allow astronomers to track meteor showers that occur during the daytime as well.

Perseid Visibility Growing

The Perseid peak is still days away, but observers around the globe are already seeing hourly rates of 10 or more, with occasional fireballs. The early reports could be indicating that the peak on Thursday night / Friday morning will be quite a show.

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Lasers Take the Twinkle Out of the Night Sky

If you are a hopeless romantic, you probably love to see a nighttime sky filled with twinkling stars. But if you are an astronomer, probably not so much. Now a team of University of Arizona astronomers led by Michael Hart has developed a technique that allows astronomers to stop the twinkling effect over a wide field of view, enabling Earth-based telescopes to obtain images that are as crisp as those made using the Hubble Space Telescope, and much faster. The technique is called laser adaptive optic and the team describes it in the August 5 issue of Nature.

Normally, light from celestial objects is blurred by atmospheric turbulence by the time it reaches the optics of a ground-based telescope. Most of that distortion happens less than a half mile above the ground, where heat rises from the surface and disturbs the air.

The new technique can be thought of as noise-canceling process, only for light waves instead of for sound waves. The heart of the process is formed by a bundle of five green lasers and a pliable mirror.

Hart and his team demonstrated the process from their observatory on Mount Hopkins, south of Tucson, Arizona. The five lasers are used to detect turbulence in the atmosphere. Any light reflected back from each laser, and the amount reflected back, indicates the amount of turbulence in the telescope’s field of view. The turbulence data is then fed into a computer which control’s the telescope’s adaptive mirror.

The back of the mirror is covered with 336 actuators, or small magnetic pins surrounded by coils. When the computer sends electric current through the coils, the actuators move, causing the mirror to warp just enough to cancel out the turbulence which causes the twinkle in the atmosphere. The corrective movements are too tiny for the human eye to see and happen a thousand times each second.

Astronomers and engineers have advanced adaptive optics over the past 15 to 20 years, but the technology was limited in that it could only be applied to a very narrow portion of the telescope’s field of view. According to Hart, this new technology can be applied over the telescope’s entire field of view. There is some trade-off in the new technique, in that it sacrifices some of the very high resolution in order to gain a larger field of view. Hart expects that this trade-off is well worth it because of the many scientific uses that it makes possible.

One use could be to study very old galaxies that formed around 10 billion years ago. These are known to astronomers as high red-shift galaxies and are thought to be billions of light years away.

The new technique would allow astronomers to study the spectral characteristics and chemical composition of these galaxies. Until now, such a study was difficult because the light from these galaxies was so faint.

For more information check out these links:

University of Arizona, Department of Astronomy and Steward Observatory
http://www.as.arizona.edu/

University of Arizona article: Taking the Twinkle Out of the Night Sky
http://uanews.org/node/33078

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Saturday, August 07, 2010

Sol Awakens

On Sunday, August 1st at 8:55 UTC, our star, known as Sol, finally stirred after a year of slumber. The signs are telling astronomers that the sun is awakening to another cycle of solar activity. Experts do not expect the activity to peak, weakly, until mid-2013.

NASA SDO Image of the sun, July 27, 2010, five days prior to the CME. Image Credit: NASA

On that recent Sunday orbiting satellites witnessed a sizable flare erupting from the large sunspot region designated 1092. The strength of the outburst was estimated at C3, relatively modest, but it still triggered an impressive coronal mass ejection (CME) that shot out from the star at more than 600 miles (1,000 km) per second.

The event was caught by NASA's recently-launched Solar Dynamics Observatory (SDO). It watched as the magnetic disturbance caused an enormous filament of superheated gas to pulse across the Sun's disk.

VIDEO: NASA SDO - Filament Eruption and Solar Flare, August 1, 2010

On the night side of Earth, skywatchers at far northern and southern locations enjoyed colorful auroral displays over the night of August 3 to 4.

Since the CME, the big spot in region 1092 has been joined by a second, smaller group, called 1093. If you want to take a look for yourself, remember to view by indirect light, or by using a safe solar filter.

Check Out These Sites:

NASA's Solar Dynamics Observatory (SDO)
http://sdo.gsfc.nasa.gov/

VIDEO: NASA SDO - Filament Eruption and Solar Flare, August 1, 2010
http://www.youtube.com/watch?v=thm6SCv-sj0&feature=player_embedded

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