Posted on by Fraser Cain

Deep Impact Sees a Burst from Tempel 1

Artist illustration of Deep Impact with Comet Tempel 1. Image credit: NASA/JPL. Click to enlarge.
NASA’s Deep Impact spacecraft observed a massive, short-lived outburst of ice or other particles from comet Tempel 1 that temporarily expanded the size and reflectivity of the cloud of dust and gas (coma) that surrounds the comet nucleus.

The outburst was detected as a dramatic brightening of the comet on June 22. It is the second of two such events observed in the past two weeks. A smaller outburst also was seen on June 14 by Deep Impact, the Hubble Space Telescope and by ground based observers.

“This most recent outburst was six times larger than the one observed on June 14, but the ejected material dissipated almost entirely within about a half day,” said University of Maryland College Park astronomer Michael A’Hearn, principal investigator for the Deep Impact mission. A’Hearn noted that data from the spectrometer aboard the spacecraft showed that during the June 22 outburst the amount of water vapor in the coma doubled, while the amount of other gases, including carbon dioxide, increased even more.

A movie of the cometary outburst is available on the Internet at http://www.nasa.gov/deepimpact .

“Outbursts such as this may be a very common phenomenon on many comets, but they are rarely observed in sufficient detail to understand them because it is normally so difficult to obtain enough time on telescopes to discover such phenomena,” A’Hearn said. “We likely would have missed this exciting event, except that we are now getting almost continuous coverage of the comet with the spacecraft’s imaging and spectroscopy instruments.”

Deep Impact co-investigator Jessica Sunshine, with Science Applications International Corporation, Chantilly, Va., agreed that observing such activity twice in two weeks suggests outbursts are fairly common. “We must now consider them as a significant part of the processing that occur on comets as they heat up when approaching the sun,” she said.

Comet Tempel 1 is near perihelion, or the point in its orbit at which it is closest to the Sun.

“This adds to the level of excitement as we come down to the final days before encounter,” said Rick Grammier, Deep Impact project manager at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “But this comet outburst will require no modification to mission plan and in no way affects spacecraft safety.”

Deep Impact consists of a sub-compact-car-sized flyby spacecraft and an impactor spacecraft about the size of a washing machine. The dual spacecraft carries three imaging instruments, two on the flyby spacecraft and one on the impactor. A spectrometer on the flyby spacecraft uses the same telescope as the flyby’s high- resolution imager.

The final prelude to impact will begin early on July 3, 24 hours before the 1:52 a.m. EDT July 4th impact, when the flyby spacecraft releases the impactor into the path of the comet. Like a copper penny pitched up into the air just in front of a speeding tractor-trailer truck, the 820-pound impactor will be run down by the comet, colliding with the nucleus at a closing speed of 23,000 miles per hour. Scientists expect the impact to create a crater several hundred feet in size; ejecting ice, dust and gas from the crater and revealing pristine material beneath. The impact will have no significant affect on the orbit of Tempel 1, which poses no threat to Earth.

Nearby, Deep Impact’s “flyby” spacecraft will use its medium and high resolution imagers and infrared spectrometer to collect and send to Earth pictures and spectra of the event. The Hubble and Spitzer Space Telescopes, the Chandra X-ray Observatory, and large and small telescopes on Earth also will observe the impact and its aftermath.

The University of Maryland, College Park, conducts overall mission science for Deep Impact that is a Discovery class NASA program. NASA’s Jet Propulsion Laboratory handles project management and mission operations. The spacecraft was built for NASA by Ball Aerospace and Technologies Corporation, Boulder, Colo.

Original Source: NASA/JPL News Release

Posted on by Fraser Cain

Is This a Lake on Titan?

An unusual feature on the surface of Titan that could be a hydrocarbon lake. Image credit: NASA/JPL/SSI. Click to enlarge.
This view of Titan?s south polar region reveals an intriguing dark feature that may be the site of a past or present lake of liquid hydrocarbons.

The true nature of this feature, seen here at left of center, is not yet known, but the shore-like smoothness of its perimeter and its presence in an area where frequent convective storm clouds have been observed by Cassini and Earth-based astronomers make it the best candidate thus far for an open body of liquid on Titan.

If this interpretation is correct, then other very dark but smaller features seen in the south polar region, some of which are captured in this image, may also be the sites of liquid hydrocarbon reservoirs.

In addition to the notion that the dark feature is or was a lake filled with liquid hydrocarbons, scientists have speculated about other possibilities. For instance, it is plausible that the ‘lake’ is simply a broad depression filled by dark, solid hydrocarbons falling from the atmosphere onto Titan?s surface. In this case, the smoothed outline might be the result of a process unrelated to rainfall, such as a sinkhole or a volcanic caldera.

A red cross below center in the scene marks the pole. The brightest features seen here are methane clouds. A movie sequence showing the evolution of bright clouds in the region during the same flyby is also available (see PIA06241).

This view is a composite of three narrow angle camera images, taken over several minutes during Cassini’s distant June 6, 2005 flyby. The images were combined to produce a sharper view of Titan?s surface. The images were taken using a combination of spectral filters sensitive to wavelengths of polarized infrared light. The images were acquired from approximately 450,000 kilometers (279,000 miles) from Titan. Resolution in the scene is approximately 3 kilometers (2 miles) per pixel. The view has been contrast enhanced to improve the overall visibility of surface features.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the Cassini-Huygens mission for NASA’s Science Mission Directorate, Washington, D.C. The imaging team is based at the Space Science Institute, Boulder, Colorado.

For more information about the Cassini-Huygens mission, visit http://saturn.jpl.nasa.gov and the Cassini imaging team home page, http://ciclops.org.

Original Source: CICLOPS News Release

Posted on by Fraser Cain

Spotty Janus

Close up view of Saturn’s moon Janus. Image credit: NASA/JPL/SSI. Click to enlarge.
This close-up look at Saturn’s moon Janus reveals spots on the moon’s surface which may be dark material exposed by impacts. If the dark markings within bright terrain are indeed impact features, then Janus’ surface represents a contrast with that of Saturn’s moon Phoebe, where impacts have uncovered bright material beneath a darker overlying layer. Janus is 181 kilometers (113 miles) across.

Janus may be a porous body, composed mostly of water ice.

This image was taken in visible light with the Cassini spacecraft narrow-angle camera on May 20, 2005, at a distance of approximately 357,000 kilometers (222,000 miles) from Janus and at a Sun-Janus-spacecraft, or phase, angle of 6 degrees. Resolution in the original image was 2 kilometers (1 mile) per pixel. The view was magnified by a factor of two and contrast-enhanced to aid visibility of the moon’s surface.

The Cassini-Huygens mission is a cooperative project of NASA, the European Space Agency and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA’s Science Mission Directorate, Washington, D.C. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging team is based at the Space Science Institute, Boulder, Colo.

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov . The Cassini imaging team homepage is at http://ciclops.org .

Original Source: NASA/JPL/SSI

Posted on by Fraser Cain

X-Rays Sparkle in Saturn’s Rings

Blue flashes of X-rays from Chandra on top of an optical image of Saturn. Image credit: NASA. Click to enlarge.
Chandra images reveal that the rings of Saturn sparkle in X-rays (blue dots in this X-ray/optical composite). The likely source for this radiation is the fluorescence caused by solar X-rays striking oxygen atoms in the water molecules that comprise most of the icy rings.

As the image shows, the X-rays in the ring mostly come from the B ring, which is about 25,000 kilometers wide and is about 40,000 kilometers (25,000 miles) above the surface of Saturn (the bright white inner ring in the optical image). There is some evidence for a concentration of X-rays on the morning side (left side, also called the East ansa) of the rings. One possible explanation for this concentration is that the X-rays are associated with optical features called spokes, which are largely confined to the dense B ring and most often seen on the morning side.

Spokes, which appear as radial shadows in the rings, are due to transient clouds of fine ice-dust particles that are lifted off the ring surface, and typically last an hour or so before disappearing. It has been suggested that the spokes are triggered by meteoroid impacts on the rings, which are more likely in the midnight to early morning hours because during that period the relative speed of the rings through a cloud of meteoroids would be greater.

The higher X-ray brightness on the morning side of the rings could be due to the additional solar fluorescence from the transient ice clouds that produce the spokes. This explanation may also account for other Chandra observations of Saturn, which show that the X-ray brightness of the rings varies significantly from one week to the next.

Original Source: Chandra News Release

Posted on by Fraser Cain

Spacecraft Wakes Up for Comet Collision

Artist illustration of SWAS. Image credit: CfA. Click to enlarge.
The Submillimeter Wave Astronomy Satellite (SWAS) has been asleep on orbit for the past 11 months. SWAS operators placed it into hibernation after a highly successful 5.5-year mission highlighted by the discovery of a swarm of comets evaporating around an aging red giant star. Now, they have awakened SWAS again for the first-ever opportunity to study a comet on a collision course with a U.S. space probe.

“We knew there was life left in SWAS,” said SWAS Principal Investigator Gary Melnick (Harvard-Smithsonian Center for Astrophysics). “SWAS’s ability to detect emission from water convinced us that we could contribute to the broader understanding of comets generated by this event. This once-in-a-lifetime event was just too tempting to pass up.”

NASA’s Deep Impact mission will rendezvous with Comet Tempel 1 at the end of June. Twenty-four hours before collision, on July 3rd, the flyby spacecraft will deploy a 39-inch long by 39-inch wide, 802-pound copper-reinforced impactor to strike the comet’s nucleus. As the main Deep Impact spacecraft watches from a safe distance, the impactor will blast material out of the comet, excavating a football stadium-sized crater of pristine ice from the interior. SWAS will measure the abundance of water molecules as the icy comet debris vaporizes.

“Because a comet is composed mostly of ice and rock, water is the most abundant molecule released by a comet. Everything else vaporizing from the comet is measured relative to the amount of water,” said Melnick. “Water is the gold standard for comets, so knowing how much water is being released per second is a very useful piece of information.”

Current SWAS measurements indicate that Comet Tempel 1 is ejecting about 730 pounds of water per second, which is modest by cometary standards. Deep Impact mission designers specifically selected the target for this reason because the probe’s mothership will have a better chance of surviving the flyby. SWAS will watch closely for any changes to the water production rate during and after the impact. Its measurements will help constrain the nature of the comet’s nucleus, including its chemical makeup.

NASA and the SWAS team decided to reawaken the satellite because it offers several unique advantages for observing the impactor-comet collision. SWAS can determine the water production rate directly. It has a large field of view that encompasses both the comet nucleus and the surrounding envelope of vaporized gases known as the coma. And, it is above the atmosphere and unaffected by weather, allowing SWAS to monitor the comet almost continuously.

In early June, the satellite was powered up and its components successfully tested. SWAS will remain active through the end of August, watching Comet Tempel 1 for any long-term changes.

“It’s gratifying that a satellite that has contributed so much during its lifetime has been given one more opportunity,” said Melnick. “Helping to decipher the composition of material thought to be unchanged since the birth of our solar system seems like a great last act.”

Headquartered in Cambridge, Mass., the Harvard-Smithsonian Center for Astrophysics (CfA) is a joint collaboration between the Smithsonian Astrophysical Observatory and the Harvard College Observatory. CfA scientists, organized into six research divisions, study the origin, evolution and ultimate fate of the universe.

Original Source: CfA News Release

Posted on by Fraser Cain

Podcast: Having a BLAST in the Arctic

If you’re an astronomer and you want to escape the Earth’s hazy atmosphere, you need a space telescope… right? Not necessarily, sometimes all you need is a balloon, and some clear arctic skies. An international team of researchers traveled to Sweden and deployed a 33-storey tall balloon carrying the BLAST telescope, designed to study the birth of stars and planets. Gaelen Marsden is a member of the team, and researcher at the University of British Columbia in Vancouver, Canada.
Continue reading “Podcast: Having a BLAST in the Arctic”

Posted on by Fraser Cain

Audio: Having a BLAST in the Arctic

Giant balloon carrying the BLAST instrument into the high atmosphere. Image credit: Joe Martz. Click to enlarge.
Listen to the interview: Having a BLAST in the Arctic (4.5 MB)

Or subscribe to the Podcast: universetoday.com/audio.xml

Fraser Cain: It’s nice to finally have a chance to talk to someone from my home town. How’s the weather there?

Gaelen Marsden: Oh, it’s pretty nice today, nice and sunny.

Fraser: And how does it compare to northern Sweden?

Marsden: Well, it gets dark, which is pretty great.

Fraser: Right, right, 24 hours of sunlight. Can you give me some background on the mission that you just came back from in the North?

Marsden: So, it’s a balloon borne telescope, and carries a 2 metre mirror. BLAST stands for balloon borne large aperture submillimeter telescope. We fly in a balloon to an altitude of 40 kilometres. The 2 metre mirror, which is fairly large for a balloon – it’s nothing compared to ground-based telescopes – but it’s big for a balloon and comparable to current satellite telescopes. We’re measuring in the submillimeter, which is a new frontier. There are a few ground-based telescopes that measure in the submillimeter, but we’re the first ones to do it from near space, not quite space. The advantage to submillimeter is that you’re looking at – in the case of the extragalactic science targets – reprocessed light from very large stars; bright heavy stars as their galaxies first turn on with a flash of star formation. Along with the star formation, you have dust, and the dust absorbs the light from the stars and re-radiates it in the submillimeter. So that’s what we’re looking at.

Fraser: How does a balloon stand as a platform for having an observatory?

Marsden: Right, it’s a quick, cheap, dirty alternative to a satellite. We’re actually piggybacking on the European Space Agency’s called Herschel, which has an experiment on board called SPIRE. We’re using the same detectors and a similar mirror, and they will fly, I believe in 2007; although, it’ll probably be 2008. They’ll do a better job than us. They’re in space, there’s no atmosphere at all, they’ll have much longer observing time, but on the other hand, it costs 100 times as much and takes 10-15 years. Whereas, we put this together in about 5 years. That’s the read advantage; it’s very quick and it’s much cheaper.

Fraser: What other kinds of observations do you think could be done from a balloon-based observatory?

Marsden: Ballooning is nothing new. It’s been going on for probably 30-40 years. One of the most famous ones is the Boomerang telescope, which flew from Antarctica in, I believe, 1998-2000. And that’s CMB, Cosmic Microwave Background studies. There’s been a whole slew of balloon-borne telescopes looking at the Cosmic Microwave Background. And then also it’s very common in atmospheric sciences to use balloons.

Fraser: You launched the balloon a couple of weeks ago from Sweden. Where did it go, and what happened to it?

Marsden: Right, so we launched it Saturday morning. First it goes up, it takes about 3 hours to get to the destination altitude of 38 km, actually we were a little higher than that at first, I think we were closer to just over 39 km. The winds are fairly predictable, these high altitude winds. This is why we do it from Sweden, or from Antarctica. During the summer, the winds go in a circle. Not that we know exactly what it’s going to do, but you know it’s going to go West during the summer. And it did go West. It ended up going quicker than were hoping. The wind models were showing about 20 knots and we were going as fast as 40 knots some of the time. That ended up slowing us down. We were hoping to take 5 days to get across to the Northwest Territories, and it actually ended up being 4 days. And another problem is that we drifted north which caused problems because we wanted to fly all the way across to Alaska, but we ended up being too far north, and we had to cut down to Victoria Island instead, which cut off another 18 hours.

Fraser: So the balloon came around the pole and then drifted over northern Canada. How did you retrieve it?

Marsden: Two members of the team, Mark Devlin and Jeff Klein, both from the University of Pennsylvania, left Sweden after the first day. When the balloon launches, we get line of site telemetry. We get all of the data through a dish. For the first 18 hours or so, we’re getting all of the data. We’re all looking at it carefully, and it’s really important that we get everything set up properly for the rest of the flight to go smoothly. Eventually it passes over the mountains, and we don’t get that high data rate any more, and we get much less – by a factor of like a 1000 or so – data rate. So, for the rest of the flight, we just had a trickle of data coming in. But as soon as the line of sight data was over, Mark and Jeff left Sweden, flew back to Philidelphia, and then quickly left for Northwest Territories, and they were nearby when the balloon came down. It sounds like a fairly difficult task because it was quite remote, and they had to fly in by helicopter. They had to cut the thing up into fairly small pieces to retrieve it all.

Fraser: Now, if I understand correctly, the submillimeter is at the high end of the radio spectrum, and it’s really good for looking at cold objects. So, what exactly were you looking at?

Marsden: From the beginning, the science proposal stated that we had two cases: the extragalactic and also the galactic. Extragalactic was what I was talking about earlier, this high star formation in very young galaxies, and redshifts of up to 3, and possibly 5. That was the extragalactic case. There’s also the galactic case, where we’re looking at planet formation and dust in our own galaxy which is, at this point, not very well known. And it actually turned out that due to the sensitivity of the telescope being lower than we had hoped, we decided that it wasn’t the best use of our time to spend a lot of our time looking at the extragalactic sources. We actually spent most of our time looking at galactic sources because they’re closer, larger, brighter, easier things to see. In the galactic case, I actually myself don’t know a whole lot about the science because I’ve been spending my time studying extragalactic. But we’re looking at cold dust clouds in our own galaxy. Some of them will be forming stars and planets, which at this point is not well known. There are many wavelength observations of all these things, and we’re trying to add the submillimeter portion of it, so that you can look at these sources in the radio, although, I suspect you don’t see them very brightly in radio, but certainly optical. You see these pretty pictures from Hubble of these dusty nebulae, and we’re just adding the submillemeter presence to that curve to see if we can figure out what’s actually going on there.

Fraser: Do you have any more missions planned, or follow up observations?

Marsden: Yeah, definitely. We’re hoping to learn from the things that went wrong here. We had some problems in the flight, certainly we got a lot of science, and we’re very excited about it. There will be a lot of good things coming out of it, but we still want to go after the extragalactic stuff. We’re going to spend the next year or so putting everything back together and then try to get a handle on the things that went wrong with the flight. We’re hoping to turn around for another flight in 18 months from Antarctica.

BLAST Website

Posted on by Fraser Cain

What’s Up This Week – June 27 – July 3, 2005

Visualization of skies on June 27. Nordic Optical Telescope. Image credit: Jacob Clasen. Click to enlarge.
Monday, June 27 – You asked for something cool? You got it. Tonight Venus and Mercury will be so close to each other for American viewers that their apparent separation will depend mainly on your viewing position. Known as an appulse, viewers in the east will catch the pair around 7 arcminutes apart – that’s just a fraction over one-tenth of a degree! In the west, the separation will be nearer 9 arcminutes, and if you observe in Hawaii? 10 arcminutes. Be sure to take the opportunity to see the very closest planetary pairing of the year! Wishing you all clear skies…

Be on the lookout tonight for a handful of meteors originating near the constellation of Corvus. The Corvid meteor shower is not well documented, but you might spot as many as ten per hour.

Tuesday, June 28 – Our splendid sunset dance of the planets continues as tonight Mercury has shuttled less than half a degree to the left of Venus and Saturn has slid to the lower right of our close pairing as they continue to rise. Still in range of most binocular fields, Venus and Saturn have now separated by about three and half degrees.

With the time of Deep Impact growing closer by the hour, I am not going to leave you alone until you locate this comet for yourself! Rapidly approaching perihelion, 9/P Tempel 1 is roughly the same brightness as the “Ring” nebula – so what are you waiting for? About a degree and a half northeast of Spica, you can easily spot star 76 in binoculars or finderscope, and the comet is just to its west. Once you locate it, it will be easy to follow as it continues slowly due south. Don’t wait until the last minute to view this comet, because as all astronomers know – you don’t make a “date” with the sky, it makes one with you!

Wednesday, June 29 – Are you enjoying the intriguing show of the planets? Then get up early to catch Mars and the Moon roughly four degrees apart! Watch the planets again after sunset as speedy Mercury continues to distance itself from Venus. They will appear slightly more than half a degree apart. What we are witnessing is Mercury turning around in its orbit and it’s just luck that it happens to be near Venus from our viewpoint.

Today we celebrate the birthday of George Ellery Hale, who was born in 1868. Hale was the founding father of the Mt. Wilson Observatory. Although he had no education beyond his baccalaureate in physics, he became the leading astronomer of his day. He invented the spectroheliograph, coined the word astrophysics and founded the Astrophysical Journal as well as Yerkes Observatory. At the time, Mt. Wilson dominated the world of astronomy, confirming what galaxies were and verifying the expanding universe cosmology, making Mt. Wilson one of the most productive facilities ever built. When Hale went on to found Palomar Observatory, the 5-meter (200″) telescope was named for him and dedicated on June 3, 1948. It continues to be the largest telescope in the continental United States.

Let’s celebrate Hale’s achievements tonight by viewing a pair of interacting galaxies. 40′ northwest of Beta Canum Venaticorum is NGC 4490 and smaller, fainter companion NGC 4485. This pair, also known as Arp 269, are quite unusual in appearance to the larger scope. NGC 4490 is around magnitude 10 and shows a bright, irregular core region and a rather strange profile. Known as the “Cocoon” galaxy, it appears to almost reach toward its companion 3′ to the north. Progressively larger scopes under ideal conditions will be able to make out some faint mottling in the NGC 4490’s structure.

Thursday, June 30 – And the show goes on. Mercury and Venus are separated by close to one degree tonight, and this is getting to be your last chance to catch Saturn before it quickly blends in with the twilight glow.

With the Moon comfortably out of the way, tonight would be an excellent opportunity to just find a comfortable seat, relax and watch for the June Draconid meteor shower. The radiant for this shower will be near handle of Big Dipper – Ursa Major. The fall rate varies from 10 to 100 per hour, but tonight’s darker skies will offer us a better than usual chance to spot the offspring of comet Pons-Winnecke. On a curious note, today in 1908 was when the great Tunguska impact happened in Siberia. A fragment of a comet, perhaps?

Friday, July 1 – Tonight we honor southern skies by exploring the fantastic, NGC 3372 – the Eta Carinae Nebula. As a giant, diffuse nebula with a visual brightness of magnitude 1, (wow!) it contains the most massive and luminous star in our Milky Way galaxy, Eta Carinae. It’s also home to a small cluster, Collinder 228, which is only one of 8 cataloged open clusters within the area of this huge star-forming region; the others are Bochum (Bo) 10, Trumpler (Tr) 14 (also cataloged as Cr 230), Tr 15 (= Cr 231), Cr 232, Tr 16 (= Cr 233), Cr 234, and Bo 11. Star Eta Carinae is involved in open cluster Trumpler 16. This fantastic nebula contains details which northerners can only dream about, such as the dark “Keyhole” and the “Homunkulus” around the giant star itself. A fantastic region for exploration with both telescopes and binoculars!

Saturday, July 2 – For west, central, and southern Europe, the Moon will occult Delta Aries for you on this universal date. Please check this IOTA webpage for more details on times in your area. For our southern hemisphere friends, tonight will be very busy. Starting with New Zealand, the Moon will occult 4th magnitude 23 Tauri, 3rd magnitude Alcyone, and head towards southeast and central Australia for 27 Tauri all on this same universal date.

Today marks the 20th anniversary of the comet Halley mission – Giotto – launch. Comets are going to be very much in the news over the next few days and if you have not taken the time to look for Deep Impact’s target, Tempel 1, let’s try again tonight. Just marginally due east (about a degree and a half) of bright Spica, our comet should have brightened to magnitude 9 by this time – putting it well within the capabilities of small scopes and large binoculars. Larger telescopes will easily note a bright, almost stellar nucleus and broad fan of tail. Tempel 1 will continue southward, passing almost mid-way between Gamma Virginis and star 68 by tomorrow night. Don’t miss this opportunity!

Sunday, July 3 – Time is up. Today is the scheduled time for the Deep Impact mission to release the impactor. The clock is ticking and if you still haven’t located 9/P Tempel 1, try again tonight! There are no deep sky objects even remotely close to Tempel 1’s brightness in the area between Gamma and star 68 Virginis. Even if you have only modest binoculars, please check out the field. Place blue/white Spica, (the brightest star near Jupiter) just to the right of the field of view and you will see two visible orangish stars equidistant toward the left. It is between (and slightly below) these two stars that Deep Impact will occur and there is a strong possibility that it will flare brightly enough over the next couple of days to reach near unaided visibility. If you live in a light polluted area, it would be quite worth the drive to a darker location the keep track of this event. It’s out there… And it’s only about 400 light seconds away!

Wishing you all clear skies! May all your journeys be at Light Speed… ~Tammy Plotner

Posted on by Fraser Cain

Electric Shield for Astronauts on the Moon

Artist illustration of an electromagnetic shield that could protect astronauts. Image credit: Hubble. Click to enlarge.
Opposite charges attract. Like charges repel. It’s the first lesson of electromagnetism and, someday, it could save the lives of astronauts.

NASA’s Vision for Space Exploration calls for a return to the Moon as preparation for even longer journeys to Mars and beyond. But there’s a potential showstopper: radiation.

Space beyond low-Earth orbit is awash with intense radiation from the Sun and from deep galactic sources such as supernovas. Astronauts en route to the Moon and Mars are going to be exposed to this radiation, increasing their risk of getting cancer and other maladies. Finding a good shield is important.

The most common way to deal with radiation is simply to physically block it, as the thick concrete around a nuclear reactor does. But making spaceships from concrete is not an option. (Interestingly, it might be possible to build a moonbase from a concrete mixture of moondust and water, if water can be found on the Moon, but that’s another story.) NASA scientists are investigating many radiation-blocking materials such as aluminum, advanced plastics and liquid hydrogen. Each has its own advantages and disadvantages.

Those are all physical solutions. There is another possibility, one with no physical substance but plenty of shielding power: a force field.

Most of the dangerous radiation in space consists of electrically charged particles: high-speed electrons and protons from the Sun, and massive, positively charged atomic nuclei from distant supernovas.

Like charges repel. So why not protect astronauts by surrounding them with a powerful electric field that has the same charge as the incoming radiation, thus deflecting the radiation away?

Many experts are skeptical that electric fields can be made to protect astronauts. But Charles Buhler and John Lane, both scientists with ASRC Aerospace Corporation at NASA’s Kennedy Space Center, believe it can be done. They’ve received support from the NASA Institute for Advanced Concepts, whose job is to fund studies of far-out ideas, to investigate the possibility of electric shields for lunar bases.

“Using electric fields to repel radiation was one of the first ideas back in the 1950s, when scientists started to look at the problem of protecting astronauts from radiation,” Buhler says. “They quickly dropped the idea, though, because it seemed like the high voltages needed and the awkward designs that they thought would be necessary (for example, putting the astronauts inside two concentric metal spheres) would make such an electric shield impractical.”

Buhler and Lane’s approach is different. In their concept, a lunar base would have a half dozen or so inflatable, conductive spheres about 5 meters across mounted above the base. The spheres would then be charged up to a very high static-electrical potential: 100 megavolts or more. This voltage is very large but because there would be very little current flowing (the charge would sit statically on the spheres), not much power would be needed to maintain the charge.

The spheres would be made of a thin, strong fabric (such as Vectran, which was used for the landing balloons that cushioned the impact for the Mars Exploration Rovers) and coated with a very thin layer of a conductor such as gold. The fabric spheres could be folded up for transport and then inflated by simply loading them with an electric charge; the like charges of the electrons in the gold layer repel each other and force the sphere to expand outward.

Placing the spheres far overhead would reduce the danger of astronauts touching them. By carefully choosing the arrangement of the spheres, scientists can maximize their effectiveness at repelling radiation while minimizing their impact on astronauts and equipment at the ground. In some designs, in fact, the net electric field at ground level is zero, thus alleviating any potential health risks from these strong electric fields.

Buhler and Lane are still searching for the best arrangement: Part of the challenge is that radiation comes as both positively and negatively charged particles. The spheres must be arranged so that the electric field is, say, negative far above the base (to repel negative particles) and positive closer to the ground (to repel the positive particles). “We’ve already simulated three geometries that might work,” says Buhler.

Portable designs might even be mounted onto “moon buggy” lunar rovers to offer protection for astronauts as they explore the surface, Buhler imagines.

It sounds wonderful, but there are many scientific and engineering problems yet to be solved. For example, skeptics note that an electrostatic shield on the Moon is susceptible to being short circuited by floating moondust, which is itself charged by solar ultraviolet radiation. Solar wind blowing across the shield can cause problems, too. Electrons and protons in the wind could become trapped by the maze of forces that make up the shield, leading to strong and unintended electrical currents right above the heads of the astronauts.

The research is still preliminary, Buhler stresses. Moondust, solar wind and other problems are still being investigated. It may be that a different kind of shield would work better, for instance, a superconducting magnetic field. These wild ideas have yet to sort themselves out.

But, who knows, perhaps one day astronauts on the Moon and Mars will work safely, protected by a simple principle of electromagnetism even a child can understand.

Original Source: Science@NASA

Posted on by Fraser Cain

Hubble Sees a Jet on Comet Tempel 1

Hubble view of a jet on Comet Tempel 1. Image credit: Hubble. Click to enlarge.
In a dress rehearsal for the rendezvous between NASA’s Deep Impact spacecraft and comet 9P/Tempel 1, the Hubble Space Telescope captured dramatic images of a new jet of dust streaming from the icy comet.

The images are a reminder that Tempel 1’s icy nucleus, roughly half the size of Manhattan, is dynamic and volatile. Astronomers hope the eruption of dust seen in these observations is a preview of the fireworks that may come July 4, when a probe from the Deep Impact spacecraft will slam into the comet, possibly blasting off material and giving rise to a similar dust plume.

These observations demonstrate that Hubble’s sharp “eye” can see exquisite details of the comet’s temperamental activities. The Earth-orbiting observatory was 75 million miles away from the comet when these images were taken by the Advanced Camera for Surveys’ High Resolution Camera. The telescope’s views complement close-up images being taken by cameras aboard Deep Impact, which is speeding toward the comet.

The two images, taken seven hours apart on June 14, show Tempel 1 and its new jet. The image at left, taken at 2:17 a.m. (EDT), is a view of the comet before the outburst. The bright dot is light reflecting from the comet’s nucleus, which appears star-like in these images because it is too small even for Hubble to resolve. The nucleus, a potato-shaped object, is 8.7 miles (14 kilometers) wide and 2.5 miles (4 kilometers) long. Hubble’s viewing the nucleus is as difficult as someone trying to spot a potato in Salt Lake City from New York City.

The photo at right, snapped at 9:15 a.m. (EDT), reveals the jet [the bright fan-shaped area]. The jet extends about 1,400 miles (2,200 kilometers), which is roughly half the distance across the U.S. It is pointing in the direction of the Sun. Comets frequently show outbursts in activity, but astronomers still don’t know exactly why they occur. Tempel 1 has been moving closer to the Sun, and perhaps the increasing heat opened up a crack in the comet’s dark, crusty surface. Dust and gas trapped beneath the surface could then spew out of the crack, forming a jet. Or, perhaps a portion of the crust itself was lifted off the nucleus by the pressure of heated gases beneath the surface. This porous crust might then crumble into small dust particles shortly after leaving the nucleus, producing a fan-shaped coma on the sunward side. Whatever the cause, the new feature may not last for long.

Astronomers hope that the July 4 collision will unleash more primordial material trapped inside the comet, which formed billions of years ago. Comets are thought to be “dirty snowballs,” porous agglomerates of ice and rock that dwell in the frigid outer boundaries of our solar system. Periodically, they make their journey into the inner solar system as they loop around the Sun.

The contrast in these images has been enhanced to highlight the brightness of the new jet.

Original Source: Hubble News Release