Universe Today

July 3, 2009December 24, 2015 by Fraser Cain

Mercury and Pluto

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Before Pluto was discovered, there were 8 planets in the Solar System; and Mercury was the smallest. And then in 1930, the discovery of Pluto brought that number up to 9. For most of the 20th century, scientists weren’t sure which was bigger, Pluto or Mercury. But accurate measurements helped scientists conclude that Pluto was the smaller planet. And then in 2006, astronomers voted to remove Pluto as a planet, and so we’ve got back to 8 planets. And once again, Mercury is the smallest planet in the Solar System. But let’s compare the dwarf planet Pluto and Mercury.

In terms of size, scientists now know that Mercury is significantly larger than Pluto. The diameter of Mercury is 4,879.4 km across, while Pluto’s diameter is 2,360 km across. So Mercury is about twice as large Pluto. And just for comparison, Pluto is only 18% the diameter of Earth, while Mercury is 38% the diameter of Earth.

When it comes to density, though, Mercury and Pluto are very different. Mercury is comprised of rock and metal, while Pluto is ice and rock. The density of Mercury is 5.427 g/cm³, while the density of Pluto is about 2 g/cm³. And since Pluto is smaller and less dense than Mercury, it has a much lower force of gravity. While you would feel 38% the force of Earth gravity standing on the surface of Mercury, you would experience only 5.9% of Earth gravity on Pluto. It would be extremely difficult to walk around the surface of Pluto without flying up in the air with every step.

Mercury is the closest planet to the Sun, orbiting at an average distance of only 57.9 million km, while Pluto orbit at an average distance of 5.9 billion km. Mercury completes an orbit in just 88 days, while Pluto takes 248 years to go around the Sun just once.

Mercury has no rings or moons, while Pluto has at least 3 moons (Charon, Nix and Hydra) and might even have faint ice rings; these could be generated by meteorite impacts on the surface of Pluto kicking up material into orbit around it.

There’s one big difference between the two worlds, though. It’s possible to see Mercury with the unaided eye. If you head out before sunrise, or after sunset and look to the horizon, you can see Mercury with your own eyeballs. Pluto, on the other hand, requires a very powerful telescope; and even then it’ll only look like a faint dot.

Another difference is the fact that Mercury has been visited by spacecraft from Earth. This has given us close up images of the surface of the planet. Pluto has never been seen up close. That’s going to change soon, though, when NASA’s New Horizons spacecraft arrives at Pluto in 2015 and takes the first close up images of the dwarf planet.

We have written many stories about Mercury here on Universe Today. Here’s an article about a the discovery that Mercury’s core is liquid. And how Mercury is actually less like the Moon than previously believed.

If you’d like more information on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

Mercurio y Plutón

Source: NASA

July 3, 2009December 24, 2015 by Tammy Plotner

Weekend SkyWatcher’s Forecast: July 3-5, 2009

Greetings, fellow SkyWatchers! Are you ready for a Moon-filled weekend? Then let’s have a look a some great lunar features as we race Mad Max to the “Megadome”! For some lucky viewers in Japan and Hawaii, there will be an occultation of Antares to enjoy. How about some great double stars… Or a chance to see if you can spot a penumbral lunar eclipse? Then follow me out to the backyard. The stars are waiting…

Friday, July 3, 2009 – Tonight let’s venture toward the south shore of Palus Epidemiarum to have a high-power look at crater Capuanus. Named for Italian astronomer Francesco Capuano di Manfredonia, this 60 kilometer-wide crater boasts a still tall southwest wall, but the northeast one was destroyed by lava flow.

At its highest, it reaches around 1,900 meters above the lunar surface, yet drops to no more than 300 meters at the lowest. Look for several strikes along the crater walls as well as more evidence of a strong geological history. To the north is the Hesiodus Rima, a huge fault line that extends 300 kilometers across the surface!

When you’re done, why not have a look at 156-light-year-distant Mu Serpentis (RA 15 49 37 Dec –03 25 48)? Its name is Leiolepis, which means ‘‘smooth scaled.’’ Perhaps a fitting name, because this normal A-type main sequence star is also known as the head of the serpent. Have a look in binoculars, and you’ll note several optical companions. Or use a telescope to locate delicate binary Struve 1985 (RA 15 56 01 Dec –02 11 00) nearby!

Saturday, July 4, 2009 – Look closely at the Moon. For some lucky viewers, it’s about to occult Antares! Check International Occultation and Timing Association (IOTA) for times and locations.

Also be sure to look for the ‘‘Cow Jumping over the Moon,’’ but power up with a telescope to study some very wild looking features—lunar lava domes. North of Aristarchus, west of Promontorium Heraclides, and near the terminator is Rumker—the largest of the lava domes. Only visible when near the terminator, this roughly 77-kilometer-diameter ‘‘soft hill’’ ranges anywhere from 60 to 760 meters tall. Although it is not much more than a bump on the lunar surface, it does contain a few summit craters at its highest points. What we are looking at is really an important part of the geology that shaped the Moon’s surface. In all likelihood, Rumker is a shield volcano. . .in an area of many!

Now continue east toward the prominent crater Marian, set in a bright peninsula extending into Sinus Roris and Mare Imbrium. Just southwest are two more—Mons Gruithuisen Gamma (the ‘‘Megadome’’) and Mons Gruithuisen Delta. Although you might not find these features particularly impressive, consider that we’re looking at something only 20 kilometers wide and only a few meters high!

Tonight we honor American astronomer Henrietta Swan Leavitt, the discoverer of the relationship between period and luminosity in Cepheid variables. This led to understanding the distance to the galaxies! Said Leavitt, ‘‘Since the variables are probably nearly the same distance from Earth, their periods are apparently associated with their actual emission of light, as determined by their mass, density, and surface brightness.’’ Do her memory honor and check out Delta Cephei (RA 22 29 10 Dec þ58 24 54) tonight! Thirty to forty times more massive than our own Sun, Delta varies from magnitude 3.6–4.3 in just slightly over 5 days. And look for its companion star as well.

Sunday, July 5, 2009 – Tonight let’s go deep south and have look at an area that once held something almost half a bright as tonight’s Moon and over four times brighter than Venus. Only one thing could light up the skies like that—a supernova.

According to historical records from Europe, China, Egypt, Arabia, and Japan, 1,003 years ago the very first supernova event was noted. Appearing in the constellation of Lupus, it was at first believed to be a comet by the Egyptians, yet the Arabs saw it as an illuminating ‘‘star.’’ Located less than a finger-width northeast of Beta Lupi (RA 15 02 48 Dec –41 54 42) and half a degree east of Kappa Centaurus, no visible trace is left of a once-grand event that spanned 5 months of observation, beginning in May and lasting until it dropped below the horizon in September 1006. It is believed that most of the star was converted to energy, and very little mass remains. In the area, a 17th magnitude star that shows a tiny gas ring and radio source 1459-41 remains our best candidate for pinpointing this incredible event.

Why you’re at it, try a challenging double star—Upsilon Librae (RA 15 37 01 Dec –28 08 06). This beautiful red star is right at the limit for a small telescope, but quite worthy, as the pair is a widely disparate double. Look for the 11.5-magnitude companion to the south in a very nice field of stars!

If you’d like to try for a challenging observation, then take look on the universal date of July 7th for a partial penumbral eclipse. While this isn’t anything to get intensely excited over, since the Moon will only graze through a small portion of the Earth’s shadow, chances are you might just notice something a little different. While a certain very reputable periodical says “The moon skims through too little of the penumbra to be noticed even by the most intent observer.” – I have also heard them say things like the partial solar eclipse won’t be visible here or there – and proved them wrong. It’s only my opinion, of course, but I believe no one should be discouraged from making an observation if they have the time, the energy, the location or the desire! So here’s what to do…

The partial penumbral eclipse will be seen starting in eastern Australia as the Moon rises just after dusk on July 7th and it will occur as the Moon is setting over western North and South America in the early predawn hours of July 7th. Only the northern third of the lunar surface will be affected, and it will be just a slight change in coloration – a vague gray shadowing. However, this is simply a prediction on the vague part! I have seen times when this happens that the appearance is very noticeable, and times when you truly can’t tell at all. Why not judge for yourself? I look forward to hearing your results!

Good luck and clear skies…

This week’s awesome images are: Capuanus, Marian and the Megadome (credit—Wes Higgins), Mu Serpentis, Delta Cephei, Field of SN 1006 and Upsilon Librae (credit – Palomar Observatory, courtesy of Caltech). We thank you so much!

July 2, 2009December 24, 2015 by Anne Minard

Happy Fourth of July!

Courtesy of the National Astronomical Observatory of Japan

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Astronomers working with the Subaru Telescope have released these new images of a “fireworks display” in a near-infrared image of the Helix Nebula, showing comet-shaped knots within.

Enlarged image, showing an enormous number of knots. The size of each knot is about five times as big as Pluto’s orbit in the Solar System

The Helix Nebula, NGC 7293, is not only one of the most interesting and beautiful planetary nebulae; it is also one of the closest nebulae to Earth, at a distance of only 710 light years away. The new image, taken with an infrared camera on the Subaru Telescope in Hawaii, shows tens of thousands of previously unseen comet-shaped knots inside the nebula. The sheer number of knots–more than have ever been seen before—looks like a massive fireworks display in space.

The Helix Nebula was the first planetary nebula in which knots were seen, and their presence may provide clues to what planetary material may survive at the end of a star’s life. Planetary nebulae are the final stages in the lives of low-mass stars, such as our Sun. As they reach the ends of their lives they throw off large amounts of material into space. Although the nebula looks like a fireworks display, the process of developing a nebula is neither explosive nor instantaneous; it takes place slowly, over a period of about 10,000 to 1,000,000 years. This gradual process creates these nebulae by exposing their inner cores, where nuclear burning once took place and from which bright ultraviolet radiation illuminates the ejected material.

Astronomers from the National Astronomical Observatory of Japan (NAOJ), from London, Manchester and Kent universities in the UK and from the University of Missouri in the US studied the emissions from hydrogen molecules in the infrared and found that knots are found throughout the entire nebula. Although these molecules are often destroyed by ultraviolet radiation in space, they have survived in these knots, shielded by dust and gas that can be seen in optical images. The comet-like shape of these knots results from the steady evaporation of gas from the knots, produced by the strong winds and ultraviolet radiation from the dying star in the center of the nebula.

Unlike previous optical images of the Helix Nebula knots, the infrared image shows thousands of clearly resolved knots, extending out from the central star at greater distances than previously observed. The extent of the cometary tails varies with the distance from the central star, just as Solar System comets have larger tails when they are closer to the Sun and when wind and radiation are stronger. “This research shows how the central star slowly destroys the knots and highlights the places where molecular and atomic material can be found in space,”says lead astronomer Dr. Mikako Matsuura, previously at NAOJ and now from University College London.

These images enable astronomers to estimate that there may be as many as 40,000 knots in the entire nebula, each of which are billions of kilometers/miles across. Their total mass may be as much as 30,000 Earths, or one-tenth the mass of our Sun. The origin of the knots is currently unknown.

This paper will be published in the Astrophysical Journal in August 2009

Final image caption: Previous optical image of the Helix Nebula, demonstrating diffuse gas surrounding a central star. The white box shows the area observed by the Subaru Telescope. Credit: NASA, NOAO, ESA, the Hubble Helix Nebula Team, M. Meixner [STScI], and T.A. Rector [NRAO]

Source: NAO of Japan

July 2, 2009December 24, 2015 by Nancy Atkinson

Perchlorates and Water Make for Potential Habitable Environment on Mars

This mosaic assembled from Phoenix images show the spacecraft's three landing legs. Splotches of Martian material on the landing leg strut at left could be liquid saline-water. Click for larger version on Spaceflightnow. com Credit: Kenneth Kremer, Marco Di Lorenzo, NASA/JPL/UA/Max Planck Institute and Spaceflightnow.com. Used by permission

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Scientists say that the Arctic region studied by Phoenix lander may be a favorable environment for microbes. Just-right chemistry and periods where thin films of liquid water form on the surface could make for a habitable setting. “Not only did we find water ice, as expected, but the soil chemistry and minerals we observed lead us to believe this site had a wetter and warmer climate in the recent past — the last few million years — and could again in the future,” said Phoenix Principal Investigator Peter Smith of the University of Arizona, Tucson.

The Phoenix science team released four papers today after spending months interpreting the data returned by the lander during its 5-month mission.

The most surprising finding was perchlorate in the Martian soil. This Phoenix finding caps a growing emphasis on the planet’s chemistry, said Michael Hecht of from the Jet Propulsion Laboratory, who led a paper about Phoenix’s soluble-chemistry findings.

“The study of Mars is in transition from a follow-the-water stage to a follow-the-chemistry stage,” Hecht said. “With perchlorate, for example, we see links to atmospheric humidity, soil moisture, a possible energy source for microbes, even a possible resource for humans.”

Perchlorate, which strongly attracts water, makes up a few tenths of a percent of the composition in all three soil samples analyzed by Phoenix’s wet chemistry laboratory. It could pull humidity from the Martian air. At higher concentrations, it might combine with water as a brine that stays liquid at Martian surface temperatures. Some microbes on Earth use perchlorate as food. Human explorers might find it useful as rocket fuel or for generating oxygen.

Close up shows splashes of material on lander leg strut. Image: Kenneth Kremer, Marco Di Lorenzo, NASA/JPL/UA/Max Planck Institute. Used by permission.

A paper about Phoenix water studies, led by Smith, cites clues supporting an interpretation that the soil has had films of liquid water in the recent past. The evidence for water and potential nutrients “implies that this region could have previously met the criteria for habitability” during portions of continuing climate cycles, these authors conclude.

Phoenix dug down with its scoop and found ice just under the surface of Mars. “We wanted to know the origin of the ice,” Smith said. “It could have been the remnant of a larger polar ice cap that shrank; could have been a frozen ocean; could have been a snowfall frozen into the ground. The most likely theory is that water vapor from the atmosphere slowly diffused into the surface and froze at the level where the temperature matches the frost point. We expected that was probably the source of the ice, but some of what we found was surprising.”

Evidence that the ice in the area sometimes thaws enough to moisten the soil comes from finding calcium carbonate in soil heated in the lander’s analytic ovens or mixed with acid in the wet chemistry laboratory. Another paper from a team led by University of Arizona’s William Boynton report that the amount of calcium carbonate “is most consistent with formation in the past by the interaction of atmospheric carbon dioxide with liquid films of water on particle surfaces.”

This mosaic of images from the Surface Stereo Imager camera on NASA's Phoenix Mars Lander shows several trenches dug by Phoenix, plus a corner of the spacecraft's deck and the Martian arctic plain stretching to the horizon. Image Credit: NASA/JPL-Caltech/University of Arizona/Texas A&M University

The new reports leave unsettled whether soil samples scooped up by Phoenix contained any carbon-based organic compounds. The perchlorate could have broken down simple organic compounds during heating of soil samples in the ovens, preventing clear detection.

The heating in ovens did not drive off any water vapor at temperatures lower than 295 degrees Celsius (563 degrees Fahrenheit), indicating the soil held no water adhering to soil particles. Climate cycles resulting from changes in the tilt and orbit of Mars on scales of hundreds of thousands of years or more could explain why effects of moist soil are present.

Phoenix launched in August 2007and landed in May, 2008. Phoenix ended communications in November 2008 as the approach of Martian winter depleted energy from the lander’s solar panels.

Sources: JPL, EurekAlert, Spaceflightnow.com

July 2, 2009December 24, 2015 by Nancy Atkinson

First Images from LRO

This image shows a cratered region near the moon's Mare Nubium region. Credit: NASA/Goddard Space Flight Center/Arizona State University

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Woohoo! NASA’s Lunar Reconnaissance Orbiter has taken its first images of the Moon! There are two cameras on board which combine to create the Lunar Reconnaissance Orbiter Camera, or LROC. They were both activated June 30, and their “first light” images were of a region in the lunar highlands south of Mare Nubium (Sea of Clouds).

“Our first images were taken along the moon’s terminator — the dividing line between day and night — making us initially unsure of how they would turn out,” said LROC Principal Investigator Mark Robinson of Arizona State University in Tempe. “Because of the deep shadowing, subtle topography is exaggerated, suggesting a craggy and inhospitable surface. In reality, the area is similar to the region where the Apollo 16 astronauts safely explored in 1972. While these are magnificent in their own right, the main message is that LROC is nearly ready to begin its mission.”

Mare Nubium region, as photographed by the Lunar Reconnaissance Orbiter's LROC instrument. Credit: NASA/Goddard Space Flight Center/Arizona State University

According to Robert Pearlman at collectSPACE, the LROC has some interesting sites lined up to image, including the imaging of Apollo landing sites.

However, the resolution of any images of Apollo sites will not be as good as those made later during the probe’s primary mapping orbit, a time when LRO will be at a lower altitude as it orbits the Moon.

The LROC Science Team has opened up a public request opportunity to suggest LROC Narrow Angle Camera targets using a public targeting tool. So, check it out and submit your requests!

The Apollo 15 and Apollo 16 landing spots are already on a list put together by NASA’s Constellation Program Office, as a “Regions of Interest” for the LROC. But all the Apollo sites are regions of interest for almost any space enthusiast!

Sources: NASA, collectSPACE,

July 2, 2009December 24, 2015 by Anne Minard

By Gamma-Rays Alone: Fermi Raises the Curtain on 16 New Pulsars

This all-sky map shows the positions of 16 new pulsars (yellow) and eight millisecond pulsars (magenta) studied using Fermi's LAT. Credit: NASA/DOE/Fermi LAT Collaboration

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For the first time, NASA’s Fermi Gamma-ray Space Telescope has spotted a new group of pulsars using only their gamma-ray emissions, in the absence of radio signals beamed to Earth. The 16 new objects are reported in this week’s edition of Science Express, in a study based out of the University of California in Santa Cruz.

A pulsar is a rapidly spinning neutron star, the dense core left behind after a supernova explosion. Most of the 1,800 known pulsars were found through their periodic radio emissions.

“These are the first pulsars ever detected by gamma rays alone, and already we’ve found 16,” said co-author Robert Johnson, a UC Santa Cruz physicist. “The existence of a large population of radio-quiet pulsars was suspected prior to this, but until Fermi was launched, only one radio-quiet pulsar was known, and it was first detected in x-rays.”

Of the 16 gamma-ray pulsars, 13 are associated with unidentified gamma-ray sources detected previously by the EGRET instrument on the Compton Gamma-ray Observatory. EGRET detected nearly 300 gamma-ray point sources, but was unable to detect pulsations from those sources, most of which have remained unidentified, said Pablo Saz Parkinson, also a SCIPP postdoctoral researcher and corresponding author of the paper.

“It’s been a longstanding question what could be powering those unidentified sources, and the new Fermi results tell us that a lot of them are pulsars,” Saz Parkinson said. “These findings are also giving us important clues about the mechanism of pulsar emissions.”

A pulsar emits narrow beams of radio waves from the magnetic poles of the neutron star, and the beams sweep around like a lighthouse beacon because the magnetic poles are not aligned with the star’s spin axis. If the radio beam misses the Earth, the pulsar cannot be detected by radio telescopes. Fermi’s ability to detect so many radio-quiet gamma-ray pulsars indicates that the gamma-rays are emitted in a beam that is wider and more fan-like than the radio beam.

The team identified the gamma-ray pulsars in data from Fermi’s Large Area Telescope (LAT). Marcus Ziegler, a postdoctoral researcher at UC Santa Cruz and corresponding author of the paper, said detection of gamma-ray pulsations from a typical source requires weeks or months of data from the LAT.

“From the faintest pulsar we studied, the LAT sees only two gamma-ray photons a day,” Ziegler said.

The very intense magnetic and electric fields of a pulsar accelerate charged particles to nearly the speed of light, and these particles are ultimately responsible for the gamma-ray emissions.

Because the rotation of the star powers the emissions, isolated pulsars slow down as they age and lose energy. But a binary companion star can feed material to a pulsar and spin it up to a rotation rate of 100 to 1,000 times a second. These are called millisecond pulsars, and Fermi scientists detected gamma-ray pulsations from eight millisecond pulsars that were previously discovered at radio wavelengths. Those results are reported in a second study also published in the July 2 edition of Science Express.

“Fermi has truly unprecedented power for discovering and studying gamma-ray pulsars,” said Paul Ray of the Naval Research Laboratory in Washington. “Since the demise of the Compton Gamma Ray Observatory a decade ago, we’ve wondered about the nature of unidentified gamma-ray sources it detected in our galaxy. These studies from Fermi lift the veil on many of them.”

Lead image caption: This all-sky map shows the positions of 16 new pulsars (yellow) and eight millisecond pulsars (magenta) studied using Fermi’s LAT. Credit: NASA/DOE/Fermi LAT Collaboration

Sources: Science and UC Santa Cruz, via Eurekalert.

July 2, 2009December 24, 2015 by Nancy Atkinson

Phoenix Lander Team: It Snows at Night on Mars

Data from the Phoenix lander's LIDAR instrument showing precipitation falling on Mars. Credit: Whiteway, et al.

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It snows on Mars. This occurs, at least in the northern arctic region where the Phoenix lander set up camp in 2008. Science teams from Phoenix were able to observe water-ice clouds in the Martian atmosphere and precipitation that fell to the ground at night and sublimate into water in the morning. James Whiteway and his colleagues say that clouds and precipitation on Mars play a role in the exchange of water between the ground and the atmosphere and when conditions are right, snow falls regularly on Mars.

“Before Phoenix we did not know whether precipitation occurs on Mars,” Whiteway said. “We knew that the polar ice cap advances as far south as the Phoenix site in winter, but we did not know how the water vapor moved from the atmosphere to ice on the ground. Now we know that it does snow, and that this is part of the hydrological cycle on Mars.”

Phoenix landed at the north arctic region on Mars (68.22°N, 234.25°E) on May 25th, 2008. On Mars, this was just before the summer solstice. Phoenix operated for 5 months, and was able to observe conditions as the seasons changed from summer to winter, giving science teams an unprecedented look at the planet’s changing weather patterns, including frost and precipitation.

The science team used the light detection and ranging instrument, known as LIDAR, and observed clouds that are similar to cirrus clouds here on Earth.

The LIDAR instrument emits pulses of laser light upward into the atmosphere, and then detects the backscatter from dust and clouds. The researchers were able to observe that water-ice crystals grow large enough to precipitate through the atmosphere at night and sublimate into water in the morning. The water vapor on the ground is then mixed back up through the air by turbulence and convection – reaching a height of about two and a half miles (four kilometers) – before again forming clouds at night.

Movie of clouds on Mars. Credit: NASA/JPL/UofA

Fall streaks in the cloud structure traced the precipitation of ice crystals toward the ground.

“Frost was predicted, but snowfall was quite a welcome surprise,” said Phoenix principal investigator Peter Smith. “In summer there was a lot of dust in the atmosphere. As we neared fall, the dust cleared, and all of a sudden there were water ice clouds forming at about 4 km (2.5 mi.) above the surface. We could see the clouds scud by, moving through the camera field, and once we saw snow coming out of the bottom of a cloud. It was very exciting to watch the daily weather changes. No one has ever had this experience.”

Using the LIDAR, the team could measurement atmospheric dust in the planetary boundary layer (PBL), the lowest part of the atmosphere which is directly influenced by its contact with a planetary surface.

Whiteway and his team said the PBL on Mars is quite interesting. “The PBL on Mars was well mixed, up to heights of around 4 kilometers, by the summer daytime turbulence and convection,” the team wrote in their paper, which is published today in the Journal Science. “The water-ice clouds were detected at the top of the PBL and near the ground each night in late summer after the air temperature started decreasing. The interpretation is that water vapor mixed upward by daytime turbulence and convection forms ice crystal clouds at night that precipitate back toward the surface.”

The clouds didn’t begin forming until around sol 80 or 90 – the number of days from when Phoenix landed on Mars — when air temperatures were cool enough for water vapor in the atmosphere to condense. In the early morning hours on sol 109, the LIDAR observed clouds and precipitation that extended all the way to the ground.

The science team said the clouds and precipitation keep the water confined within the PBL. Eventually, the ice clouds would have persisted within the PBL throughout the daytime, and water ice would have remained deposited on the ground. As the depth of the PBL decreased in late summer, the atmospheric water vapor would decrease, and the process would eventually stop as winter progressed.

Source: Science

July 2, 2009December 24, 2015 by Anne Minard

Messier 87 Shows Off for Hundreds of Earth-bound Astronomers

Artists's Conception of M87's inner core: Black hole, accretion disk, and inner jets. Credit: Bill Saxton, NRAO/AUI/NSF

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When the giant radio galaxy Messier 87 (M 87) unleashed a torrent of gamma radiation and radio flux, an international collaboration of 390 scientists happened to be watching. They’re reporting the discovery in this week’s issue of Science Express.

Large-scale VLA image of M87: White circle indicates the area within which the gamma-ray telescopes could tell the very energetic gamma rays were being emitted. To narrow down the location further required the VLBA. CREDIT: NRAO/AUI/NSF

The results give first experimental evidence that particles are accelerated to extremely high energies in the immediate vicinity of a supermassive black hole and then emit the observed gamma rays. The gamma rays have energies a trillion times higher than the energy of visible light.

Matthias Beilicke and Henric Krawczynski, both physicists at Washington University in St. Louis, coordinated the project using the Very Energetic Radiation Imaging Telescope Array System (VERITAS) collaboration. The effort involved three arrays of 12-meter (39-foot) to 17-meter (56-foot) telescopes, which detect very high-energy gamma rays, and the Very Long Baseline Array (VLBA) that detects radio waves with high spatial precision.

“We had scheduled gamma-ray observations of M 87 in a close cooperative effort with the three major gamma-ray observatories VERITAS, H.E.S.S. and MAGIC, and we were lucky that an extraordinary gamma-ray flare happened just when the source was observed with the VLBA and its impressive spatial resolving power,” Beilicke said.

“Only combining the high-resolution radio observations with the VHE gamma-ray observations allowed us to locate the site of the gamma-ray production,” added R. Craig Walker, a staff scientist at the National Radio Astronomy Observatory in Socorro, New Mexico.

Peering Deeper Into the Core of M87: At top left, a VLA image of the galaxy shows the radio-emitting jets at a scale of about 200,000 light-years. Subsequent zooms progress closer into the galaxy's core, where the supermassive black hole resides. In the artist's conception (background). the black hole illustrated at the center is about twice the size of our Solar System, a tiny fraction of the size of the galaxy, but holding some six billion times the mass of the Sun. Credit: Bill Saxton, NRAO/AUI/NSF

M 87 is located at a distance of 50 million light years from Earth in the Virgo cluster of galaxies. The black hole in the center of M 87 is six billion times more massive than the Sun.

The size of a non-rotating black hole is given by the Schwarzschild radius. Everything — matter or radiation — that comes within one Schwarzschild radius of the center of the black hole will be swallowed by it. The Schwarzschild radius of the supermassive black hole in M 87 is comparable to the radius of our Solar System.

In the case of some supermassive black holes — as in M 87 — matter orbiting and approaching the black hole powers highly relativistic outflows, called jets. The matter in the jets travels away from the black hole, escaping its deadly gravitational force. The jets are some of the largest objects in the Universe, and they can reach out many thousands of light years from the vicinity of the black hole into the intergalactic medium.

Very high-energy gamma-ray emission from M 87 was first discovered in 1998 with the HEGRA Cherenkov telescopes. “But even today, M 87 is one of only about 25 sources outside our galaxy known to emit [very high energy] gamma rays,” says Beilicke.

The new observations now show that the particle acceleration, and the subsequent emission of gamma rays, can happen in the very “inner jet,” less than about 100 Schwarzschild radii away from the black hole, which is an extremely narrow space as compared with the total extent of the jet or the galaxy.

In addition to VERITAS and the VLBA, the High Energy Stereoscopic System (H.E.S.S.) and the Major Atmospheric Gamma-Ray Imaging Cherenkov (MAGIC) gamma-ray observatories were involved in these observations.

Lead image caption: Artists’s Conception of M87’s inner core: Black hole, accretion disk, and inner jets. Credit: Bill Saxton, NRAO/AUI/NSF

Second image: Large-scale VLA image of M87: White circle indicates the area within which the gamma-ray telescopes could tell the very energetic gamma rays were being emitted. To narrow down the location further required the VLBA. CREDIT: NRAO/AUI/NSF

Collage: At top left, a VLA image of the galaxy shows the radio-emitting jets at a scale of about 200,000 light-years. Subsequent zooms progress closer into the galaxy’s core, where the supermassive black hole resides. In the artist’s conception (background). the black hole illustrated at the center is about twice the size of our Solar System, a tiny fraction of the size of the galaxy, but holding some six billion times the mass of the Sun. Credit: Bill Saxton, NRAO/AUI/NSF

Sources: Science and the National Radio Astronomy Observatory, via Eurekalert.

July 2, 2009December 24, 2015 by Nancy Atkinson

Test-Bed Rover is Now Stuck — Which is a Good Thing!

With a slope of about 10 degrees and a pointy rock under the test rover's belly, this sandbox setup at NASA's Jet Propulsion Laboratory, Pasadena, Calif., is ready for engineers to use the test rover to assess possible moves for getting Mars rover Spirit out of a patch of loose Martian soil. Credit: JPL

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Engineers at the Jet Propulsion Laboratory have intentionally driven their engineering rover into soft soil in a sandbox testbed, to simulate how the Spirit rover is stuck on Mars. And they did a good job of it, too, as the test rover, called SSTB1, is stuck, as well, with its wheels spinning and going nowhere. The science team has confirmed a rock on Mars, underneath Spirit is touching the underside of the rover, so engineers have placed a similar looking rock in the test sandbox, as seen above.

“We want to experiment with different extraction techniques down here on Earth before we actually do them for real on Mars,” said John Callas, project manager for the Mars rovers. “Our expectation is that it will some time to get Spirit out, so we will be able to get a better feel for that here in this facility to see how well the techniques work and how long it will take for them to work.”

The rover team spent several days of preparing a sloped area of soft, fine soil to simulate Spirit’s current sandtrap on Mars. On June 30 they maneuvered the test rover around, driving the wheels to the loose soil where the rover would sink and slide to the side, with a slope of about 10 degrees, as engineers believe Spirit has done on Mars.

You can follow the work being done to free Spirit from her predicament at the Free Spirit website. JPL regularly posts updates and videos showing what the rover teams are doing, and currently you can see a movie of how the test rover was driven in the sandbox to get stuck.

A test rover rolls off a plywood surface into a prepared bed of soft soil. Credit: JPL

There are actually two test vehicles, and the folks at UnmannedSpaceflight.com have a page explaining the differences, as well as other FAQs about the attempts to free Spirit. The one being use for this current test, SSTB1 is a full size replica of the MER vehicles, but it has a few differences such as no solar panels, and a few other minor missing parts. It has the same mass as the ones on Mars, which means it has a higher weight on Earth than the MERs have on Mars.

The other test rover, SSTB Lite, is a stripped down vehicle with same wheel size, actuators and suspension system, but has other major components missing which gives it a weight on Earth that is similar to the weight of MER on Mars. However, when the Opportunity rover was stuck a couple of years in the Purgatory dune, engineers found that SSTB1 behaved more similarly to the MER vehicles, possibly because both the SSTB1 and the soil were subject to the same gravity vector.

Mosaic of the area around Home Plate where Spirit remains stuck was made especially for Spaceflight Now (Used by permission). Credit: Kenneth Kremer, Marco DiLorenzo, NASA/JPL/Cornell/Spaceflight Now. Click for larger image.

So, just where is Spirit on Mars? Take a look at this great image created by Ken Kremer and Marco DeLorenzo of UnmannedSpaceflight.com, showing Spirit’s current location. It shows smooth area in the foreground, that concealed slippery water related sulfate material where rover became stuck. Once free, Spirit will drive to area near the unusually capped hill ahead designated Von Braun to sample water related evidence there. Let’s hope the engineer’s work here on Earth will “Free Spirit” and enable explorations of Von Braun, and beyond.

Caption for mosaic above: Mosaic of the area around Home Plate where Spirit remains stuck was made especially for Spaceflight Now (Used by permission). Credit: Kenneth Kremer, Marco DiLorenzo, NASA/JPL/Cornell/Spaceflight Now. Click the picture for a larger image.

Sources: “Free Spirit” website, Unmanned Spaceflight, Spaceflightnow.com

July 2, 2009December 24, 2015 by Nancy Atkinson

WiFi in Space Coming Soon?

Mike Massimino, AKA Astro_Mike on Twitter, works on his computer during the STS-125 mission. Credit: NASA

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Although current astronauts are Twittering and blogging from space, it’s a cumbersome process as the ISS, shuttle and Soyuz do not have internet access. Instead, they have to downlink their information to mission control, where someone posts it to the web. But if future commercial space travelers or astronauts living on the Moon want to blog, Tweet and share their experiences real-time, will it be possible? Well, a group of engineers are working on applying the same wireless systems that keep our mobile phones, laptops and other devices connected to the web to a new generation of networked space hardware. They say that wireless technologies will likely be important part of future space exploration, not only for human communication but for transfer of data and commands.

The Wireless Working Group (WWG) of the Consultative Committee for Space Data Services (CCSDS) is a group of engineers that coordinates wireless research among global space agencies and promotes interoperability of spacecraft data systems.

Multiple microsensors like this one could be scattered across planetary surfaces to gather more information than a single lander could provide. The microsensors would then configure a wireless network to assemble data for its relay back to Earth. Credit: ESA

They say that wireless sensor nodes placed throughout a spacecraft might function as a networked nervous system, yielding a wealth of currently inaccessible structural or environmental data to mission controllers. Similar nodes scattered across a planetary surface would generate a much higher scientific return than a single lander could, configuring a network to combine their findings for relaying to Earth.

And establishing ‘plug and play’ wireless networking between multiple spacecraft could enable the seamless transfer of data and commands. This would work for formation-flying satellite constellations and orbiter-lander-rover combinations , but proximity networks could be set up by any spacecraft within signal range as easily as a laptop plugs into a WiFi network.

Of course, the technology is still being developed and having Wifi in space isn’t going to happen anytime soon, but engineers say the underlying technologies are already with us, in the protocols delivering wireless connectivity to homes, offices and public places.

“This research is an example of us ‘spinning in’ technology developed elsewhere into the space sector,” said ESA data handling engineer Jean-François Dufour, who is part of the CCSDS. “Commercial wireless protocols such as the IEEE 802.11 family of standards for computer WiFi or sensor networking standards such as IEEE 802.15.4 are already available so we are assessing how they might transfer to the space environment.”

Source: ESA