Posted on by Jason Rhian

Google Lunar X-Prize’s ‘college team’ gaining steam, attention and support

The Google Lunar X-PRIZE team, Omega Envoy, consists primarily of college students and is working to land a rover on the lunar surface. Image Credit: ESI

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ORLANDO – The Google Lunar X-PRIZE (GLXP) recently announced the 29 official teams that will be vying for the $30 million grand prize. One group in particular stands out amongst the list however – Omega Envoy. This team is comprised primarily by college students from the University of Central Florida, working on engineering and other degrees. However, while they may be relatively young, they have drawn the attention of the media, numerous sponsors, NASA and the space industry.

NASA has inked a deal with the tiny band of potential explorers to purchase data from their spacecraft. The space agency awarded the Innovative Lunar Demonstration Data contract to Omega Envoy. This contract is worth up to $10 million. However, while this contract and the growing list of sponsors is impressive, the feat that the team is trying to accomplish is daunting. What they are attempting to do, only nations have done before.

The GLXP requires that to win, the team must safely land a robot on the lunar surface, have it travel 1,500 feet and send back both images and data to Earth. Given the fact that, to date, only the U.S. and Russia have accomplished this before – this is no small task.

Different views of Omega Envoy's proposed lunar rover. Image Credit: ESI

The Google Lunar X-PRIZE is another effort by the X-PRIZE Foundation. The impetus behind this organization is to accelerate space exploration efforts much in the same way that the Orteig Prize accelerated air travel in the 20th Century. That prize was a paltry (by today’s standards) $25,000 for the first person to fly non-stop from New York to Paris (or vice-versa). Its winner, Charles Lindbergh, would go down in history as one of the most famous aviators of all time. It is with this premise in mind that the X-PRIZE Foundation works to inspire today’s explorers and innovators.

The Omega Envoy team under Earthrise Space Inc., has been growing, gaining experience and the attention of major aerospace players - including NASA. Photo Credit: ESI

For the original Ansari X-PRIZE it took an established (if somewhat outside of the mainstream) aerospace company with years of experience to finally accomplish the objectives laid out. Scaled Composites, renowned for their kit aircraft; successfully sent a manned spacecraft into sub-orbital space, returned safely and then sent the same spacecraft, SpaceShipOne; back into space within the required two weeks.

The non-profit organization that oversees all aspects of Omega Envoy, Earthrise Space Inc. (ESI), works to provide services to private companies, government agencies, as well as educational institutions that currently have the resources to explore space and are looking for low cost products that will accomplish their requirements. They feel that this will enhance the accessibility of technology and increase educational interest amongst the workforce that drives the space.

“Aside from the GLXP, ESI intends to continuously schedule lunar deliveries for scientific payloads and robotics,” said Earthrise Space Institute’s Project Director Ruben Nunez. “Other mission objectives for Omega Envoy entail the visual feedback of a scientific payload that will analyze the lunar terrain.”

This illustration displays what Omega Envoy's lunar lander craft might look like. Image Credit: ESI

Through the Google Lunar X-PRIZE and government contracts such as the contract with NASA, it is hoped that this initiative will enable the creation of a new economic system to support lunar exploration as well as Technology Readiness Level (TRL) advancement of innovative, commercial space systems.

“I am fortunate in that I had the opportunity to witness what Omega Envoy is capable of producing when I field tested their prototype rover during the 2009 FMARS (Flashline Mars Arctic Research Station) Expedition,” said Joseph Palaia 4Frontiers’ Vice President. “There is little doubt in my mind that this team is fully capable of accomplishing the objectives laid out in the GLXP.”

One of the Omega Envoy team members, Joseph Palaia; took a prototype of the rover to be field tested during the 2009 FMARS Expedition. Photo Credit: Joseph Palaia
Posted on by VirtualAstro

The Supermoon Illusion

You’ve probably all seen it before, a huge Full Moon sitting on the horizon and you wonder why it looks much bigger than at other times? It isn’t, really; it’s an illusion.

And now, if you have heard about the close approach of the moon, or so called “Supermoon” on March 19th and are concerned about the disasters and mayem it may cause, there is no need to worry. And surely, when this so-called “Supermoon” occurs on March 19th — at its closest approach to Earth in two decades — people will indeed report that the Moon looks much bigger than normal. But it won’t really be much bigger in the sky at all. It’s all an illusion, a trick of the eye.

The moon does have an effect on the Earth with its gravity affecting ocean tides and even land to a lesser extent, but the moon on the 19th won’t interact with our planet any differently than any other time it’s been at its closest (also known as perigee).

If anything we may get slightly stronger tides, but nothing out of the ordinary.

The Moon orbits the Earth in an elliptical orbit, meaning that it is not always the same distance from the Earth. The closest the Moon ever gets to Earth (called perigee) is 364,000km, and the furthest is ever gets (Apogee) is around 406,000km (these figures vary, and in fact this Full Moon on March 19, 2011 will see a slightly closer approach of 357,000km).

So the percentage difference in distance between the average perigee and the average apogee is ~10%. That is, if the Full Moon occurs at perigee it can be up to 10% closer (and therefore larger) than if it occurred at apogee.

This is quite a significant difference, and so it is worth pointing out that the Moon does appear to be different sizes at different times throughout the year.

Moon at Perigee and Apogee Credit NASA

But that’s NOT what causes the Moon to look huge on the horizon. Such a measly 10% difference in size cannot account for the fact that people describe the Moon as “huge” when they see it low on the horizon.

What’s really causing the Moon to look huge on such occasions is the circuitry in your brain. It’s an optical illusion, so well known that it has its own name: the Moon Illusion.

If you measure the angular size of the Full Moon in the sky it varies between 36 arc minutes (0.6 degrees) at perigee, and 30 arc minutes (0.5 degrees) at apogee, but this difference will occur within a number of lunar orbits (months), not over the course of the night as the Moon rises. In fact if you measure the angular size of the Full Moon just after it rises, when it’s near the horizon, and then again hours later once it’s high in the sky, these two numbers are identical: it doesn’t change size at all.

So why does your brain think it has? There’s no clear consensus on this, but the two most reasonable explanations are as follows:

  1. When the Moon is low on the horizon there are lots of objects (hills, houses, trees etc) against which you can compare its size. When it’s high in the sky it’s there in isolation. This might create something akin to the Ebbinghaus Illusion, where identically sized objects appear to be different sizes when placed in different surroundings.

Ebbinghaus Illusion – the two orange circles are exactly the same size

  1. When seen against nearer foreground objects which we know to be far away from us, our brain thinks something like this: “wow, that Moon is even further than those trees, and they’re really far away. And despite how far away it is, it still looks pretty big. That must mean the Moon is huge!”.

These two factors combine to fool our brains into “seeing” a larger Moon when its near the horizon compared with when it’s overhead, even when our eyes – and our instruments – see it as exactly the same size.

Source: “Moon Illusion” on Dark Sky Diary Special thanks to Steve Owens

Posted on by Nancy Atkinson

Soyuz Lands Safely; Next Crew Launch Delayed

Russian Search and Rescue personnel secure their helicopters before picking up the crew of Expedition 26 that landed in Kazakhstan. Credit: NASA

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Three members of the Expedition 26 crew landed safely in their Soyuz spacecraft early Wednesday, but their replacements might not launch until mid-April, a delay of a couple of weeks. Commander Scott Kelly and Russian Flight Engineers Alexander Kaleri and Oleg Skripochka landed with no problems in the cold and snow of Kazakhstan, concluding their five-month stay aboard the International Space Station. But meanwhile, the Russian Soyuz TMA-21 is experiencing a problem with the communications system, and the new crew was scheduled to launch on March 29. But the launch may be delayed until after the April 12th 50th anniversary of Yuri Gagarin’s first space flight.

Roskosmos director Anatoly Perminov said technicians were working on a faulty transistor, and if the launch doesn’t take place by about April 9, they would likely be postponed until after the anniversary celebration of the first human to orbit Earth.

The delay could increase concerns about relying solely on Russia for rides to the ISS.

The new crew half of the Expedition 27 crew consists of NASA astronaut Ron Garan and Russian cosmonauts Andrei Borisenko and Alexander Samokutayev. Remaining on board the ISS are Dmitry Kondratyev, now commander and Flight Engineers Catherine Coleman (NASA) and Paolo Nespoli (ESA).

The Expedition 26 trio undocked from the ISS at 12:27 a.m. EDT from the station’s Poisk module, and landed at 3:54 a.m. (1:54 p.m. local time) at a site northeast of the town of Arkalyk.

Working in frigid temperatures, Russian recovery teams were on hand to help the crew exit the Soyuz and adjust to gravity. Kaleri and Skripochka will return to the Gagarin Cosmonaut Training Center in Star City, outside of Moscow, while Kelly will fly directly home to Houston.

The three returning crewmembers have been in space since Oct. 8, 2010 when they launched aboard the Soyuz TMA-01M spacecraft from the Baikonur Cosmodrome in Kazakhstan, spending 159 days in space.
During their mission, the Expedition 25 and 26 crew members worked on more than 150 microgravity experiments in human research; biology and biotechnology; physical and materials sciences; technology development; and Earth and space sciences.

Posted on by Anne Minard

New Image: VLT Captures Tumult of Starbirth

Credit: ESO

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Newborn stars spew material into the surrounding gas and dust, creating a surreal landscape of glowing arcs, blobs and streaks — and ESO’s Very Large Telescope (VLT) has caught some of them on candid camera. This new image, released today, hails from NGC 6729, a nearby star-forming region in the constellation Corona Australis.

Star formation in the constellation of Corona Australis. Courtesy of ESO

The stellar nursery NGC 6729 (RA 19h 01m 54.1s; dec -36° 57′ 12″)  is part of one of the closest stellar nurseries to Earth and therefore one of the best studied. The new VLT image gives a close-up view of a section of this strange and fascinating region.

The data were selected from the ESO archive by Sergey Stepanenko of the Ukraine, as part of the Hidden Treasures competition. The 2010 competition gave amateur astronomers the chance to search through ESO’s astronomical archives, hoping to find a well-hidden gem that needed polishing by the entrants. Participants vied for prizes, including a free trip to see the VLT in Chile for the overall winner. Stepanenko’s picture of NGC 6729 was ranked third.

Stars form deep within molecular clouds and the earliest stages of their development cannot be seen in visible-light telescopes because they kick out so much dust. Although very young stars at the upper left of the image cannot be seen directly, the havoc they have wreaked on their surroundings dominates the picture. High-speed jets of material that travel away from the baby stars at velocities as high as one million kilometers per hour are slamming into the surrounding gas and creating shock waves. The shocks cause the gas to shine and create the strangely-colored glowing arcs and blobs known as Herbig–Haro objects.

The astronomers George Herbig and Guillermo Haro were not the first to see one of the objects that now bear their names, but they were the first to study the spectra of these strange objects in detail. They realized that they were not just clumps of gas and dust that reflected light, or glowed under the influence of the ultraviolet light from young stars — but were a new class of objects associated with ejected material in star-forming regions.

Credit: ESO

In this view, the Herbig–Haro objects form two lines marking out the probable directions of ejected material. One stretches from the upper left to the lower center, ending in the bright, circular group of glowing blobs and arcs at the lower center. The other starts near the left upper edge of the picture and extends towards the center right. The peculiar sabre-shaped bright feature at the upper left is probably mostly due to starlight being reflected from dust and is not a Herbig–Haro object.

The enhanced-color picture was created from images taken using the VLT’s FORS1 instrument. Images were taken through two different filters that isolate the light coming from glowing hydrogen (shown as orange) and glowing ionized sulphur (shown as blue). The different colors in different parts of this violent star formation region reflect different conditions — for example where ionized sulphur is glowing brightly (blue features) the velocities of the colliding material are relatively low — and help astronomers to unravel what is going on in this dramatic scene.

Source: ESO press release. The paper, from the Astrophysical Journal, is available here.

Posted on by Jon Voisey

Exoplanet May Have Metal-Rich Atmosphere

Artist’s impression of GJ 1214b
Artist’s impression of GJ 1214b

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At first glance, GJ 1214b is just another of the growing number of the super-Earth class of exoplanets. Discovered by the MEarth Project in 2009, it orbits an M dwarf in Ophiuchus in a tight orbit, swinging the planet around every 1.6 days. Late last year, GJ 1214b became the first super-Earth to have a component of its atmosphere detected when astronomers compared its spectra to models finding broad agreement with water vapor present. New work, done by the same team, further refines the atmosphere’s potential characteristics.

Previously, the team suggested that their observations could potentially fit with two hypothetical planet models. In the first, the planet could be covered in hydrogen and helium, but the lack of absorption features in the atmosphere’s spectra suggested that this were not the case unless this layer were hidden by thick clouds. However, from the data available, they could not conclusively rule out this possibility.

Combining their old observations with more recent ones from the MEarth Observatory, the team now reports that they have been able to rule out this scenario with a 4.5 σ confidence (over 99.99%). The result of this is that the remaining model, which contains higher amounts of “metals” (astronomy speak meaning all elements with atomic numbers higher than helium). The team also continues to support their earlier conclusion that the atmosphere is most likely at least 10% water vapor by volume, stating this with a 3 σ (or 99.7%) confidence based on the new observations. While water vapor may sound give the impression of being an inviting place for a tropical jungle, the team predicts the close orbiting planet would be a sweltering 535 degrees Fahrenheit.

While these findings are interesting stories of the atmosphere, the prevalence of such heavy elements may also give information relating to the structure and history of the planet itself. Models of planetary atmosphere suggest that, for planets of the mass and temperature expected for GJ 1214b, there are two primary formation scenarios. In the first, the atmosphere is directly accreted during the planet’s formation. However, this would indicate a hydrogen rich atmosphere and has been ruled out. The second is that the planet formed further out, beyond the “snow line”, as an icy body, but moved in after formation, creating the atmosphere from sublimated ices.

Although outside of the scope of their atmospheric research, the team also used the timing of the transits to search for wobbles in the orbit that could be caused by additional planets in the system. Ultimately, none were discovered.

Posted on by Ken Kremer

NASA Lunar Reconnaissance Orbiter Delivers Treasure Trove of Data

LOLA data give us three complementary views of the near side of the moon: the topography (left) along with new maps of the surface slope values (middle) and the roughness of the topography (right). All three views are centered on the relatively young impact crater Tycho, with the Orientale basin on the left side. The slope magnitude indicates the steepness of terrain, while roughness indicates the presence of large blocks, both of which are important for surface operations. Lunar topography is the primary measurement being provided, while ancillary datasets are steadily being filled in at the kilometer scale. Credit: NASA/LRO/LOLA Science Team

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NASA’s Lunar Reconnaissance Orbiter (LRO) has completed its initial phase of operations during the exploration phase which lasted one year from Sept. 15, 2009 through Sept. 15, 2010 and has now transitioned to the science phase which will last for several more years depending on the funding available from NASA, fuel reserves and spacecraft health. The exploration phase was in support of NASA’s now cancelled Project Constellation

To mark this occasion NASA released a new data set that includes an overlap of the last data from the exploration phase and the initial measurements from the follow on science mapping and observational phase.

This is the fifth dataset released so far. All the data is accessible at the Planetary Data System (PDS) and the LROC website and includes both the raw data and high level processed information including mosaic maps and images.

LRO was launched on June 18, 2009 atop an Atlas V/Centaur rocket as part of a science satellite duo with NASA’s Lunar Reconnaissance Orbiter & Lunar Crater Observation and Sensing Satellite (LCROSS) from Launch Complex 41 at Cape Canaveral Air Force Station in Florida.

After achieving elliptical orbit, LRO underwent a commissioning phase and the orbit was lowered with thruster firings to an approximately circular mapping orbit at about 50 km altitude.

LRO spacecraft (top) protected by gray colored blankets is equipped with 7 science instruments located at upper right side of spacecraft. Payload fairing in background protects the spacecraft during launch and ascent. Credit: Ken Kremer
LRO was equipped with 7 science instruments that delivered more than 192 terabytes of data and with an unprecedented level of detail. Over 41,000 DVDs would be required to hold the new LRO data set.

“The release of such a comprehensive and rich collection of data, maps and images reinforces the tremendous success we have had with LRO in the Exploration Systems Mission Directorate and with lunar science,” said Michael Wargo, chief lunar scientist of the Exploration Systems Mission Directorate at NASA Headquarters in Washington according to a NASA statement.

The new data set includes a global map produced by the onboard Lunar Reconnaissance Orbiter Camera (LROC) that has a resolution of 100 meters. Working as an armchair astronaut, anyone can zoom in to full resolution with any of the mosaics and go an exploration mission in incredible detail because the mosaics are humongous at 34,748 pixels by 34,748 pixels, or approximately 1.1 gigabytes.

Browse the Lunar Reconnaissance Orbiter Camera (LROC) Image Gallery here:

The amount of data received so far from LRO equals the combined total of all other NASA’s planetary missions. This is because the moon is nearby and LRO has a dedicated ground station.

Topographic map from LRO data. Credit: NASA

Data from the other LRO instruments is included in the release including visual and infrared brightness, temperatures maps from Diviner; locations of water-ice deposits from the Lyman-Alpha Mapping Project (LAMP) especially in the permanently shadowed areas and new maps of slope, roughness and illumination conditions from the Lunar Orbiter Laser Altimeter team.

Additional new maps were generated from data compilations from the Lunar Exploration Neutron Detector (LEND), the Cosmic Ray Telescope for the Effects of Radiation and the Miniature Radio Frequency (mini RF) instruments

The combined result of all this LRO data is to give scientists the best ever scientific view of the moon.

“All these global maps and other data are available at a very high resolution — that’s what makes this release exciting,” said Goddard’s John Keller, the LRO deputy project scientist. “With this valuable collection, researchers worldwide are getting the best view of the moon they have ever had.”

Slope image. Credit: NASA
The Atlas V/Centaur carrying NASA's Lunar Reconnaissance Orbiter & Lunar Crater Observation and Sensing Satellite hurtles off Launch Complex 41 at Cape Canaveral Air Force Station in Florida on June18, 2009. Credit: NASA/Tom Farrar, Kevin O'Connell

Source: NASA Press Release

Posted on by Anne Minard

Touching the Tarantula: Hubble Gets in Close

Credit: NASA, ESA

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Hubble has edged in close to the Tarantula Nebula, peering into its bright center of ionized gases, dust and still-forming stars. The Tarantula is already a go-to celestial marvel, because its hydrogen-fueled young stars shine with such intense ultraviolet light that they ionize and redden the surrounding gas — making the nebula visible without a telescope for Earth-bound observers 170,000 light-years away. The new image may make this popular beacon, in our neighboring galaxy the Large Magellanic Cloud, even more famous.

 

Credit: NASA, ESA

The wispy arms of the Tarantula Nebula (RA 05h 38m 38s dec -69° 05.7?) were originally thought to resemble spindly spider legs, giving the nebula its unusual name. The part of the nebula visible in the new image is criss-crossed with tendrils of dust and gas churned up by recent supernovae. These remnants include NGC 2060, visible above and to the left of the center of the image, which contains the brightest known pulsar.

The tarantula’s bite goes beyond NGC 2060. Near the edge of the nebula, outside the frame, below and to the right, lie the remains of supernova SN 1987a, the closest supernova to Earth to be observed since the invention of telescopes in the 17th century. Hubble and other telescopes have been returning to spy on this stellar explosion regularly since it blew up in 1987, and each subsequent visit shows an expanding shockwave lighting up the gas around the star, creating a pearl necklace of glowing pockets of gas around the remains of the star. SN 1987a is visible in wide field images of the nebula, such as that taken by the MPG/ESO 2.2-meter telescope.

A compact and extremely bright star cluster called RMC 136 lies above and to the left of this field of view, providing much of the radiation that powers the multi-coloured glow. Until recently, astronomers debated whether the source of the intense light was a tightly bound cluster of stars, or perhaps an unknown type of super-star thousands of times bigger than the sun. It is only in the last 20 years, with the fine detail revealed by Hubble and the latest generation of ground-based telescopes, that astronomers have been able to conclusively prove that it is, indeed, a star cluster.

But even if the Tarantula Nebula doesn’t contain this hypothetical super-star, it still hosts some extreme phenomena, making it a popular target for telescopes. Within the bright star cluster lies star RMC 136a1, which was recently found to be the heaviest ever discovered: the star’s mass when it was born was around 300 times that of the sun. This heavyweight is challenging astronomers’ theories of star formation, smashing through the upper limit they thought existed on star mass.

Source: ESA press release at the Hubble site. See also previous releases on the Large Magellanic Cloud and RMC 136.

Posted on by Ken Kremer

Japan Quake May Have Shortened Earth Days, Moved Axis

TerraSAR-X Change Analysis of Sendai Area, Japan. Map show coastal area of Sendai effected by 9,0 magnitude Earthquake that triggered ensuing destructive Tsunami. Credit: Deutsches Zentrum fur Luft- und Raumfahrt (DLR) - German Aerospace Center

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The terribly destructive magnitude 9.0 earthquake which struck Japan on March 11, may have had another effect – Shortening the length of each Earth day and shifting its axis. Did you notice any change ?

Well according to NASA, the changes are so small that you won’t notice the difference.

Based on initial calculations conducted by Richard Gross, a research scientist at NASA’s Jet Propulsion Laboratory, the earthquake should have caused Earth to rotate just slightly faster, shortening the length of the day by about 1.8 microseconds (a microsecond is one millionth of a second), according to a statement released by NASA.

A reader posted this link to before and after photos

Gross used complex modeling and estimates of fault slippage to perform a preliminary theoretical calculation of how the earth’s rotation may have been affected.

Calculations by Gross also indicate that the position of Earth’s figure axis could have shifted by about 17 centimeters (6.5 inches), towards 133 degrees east longitude. The figure axis is the axis about which Earth’s mass is balanced.
Earth’s figure axis is therefore different and offset from the north-south axis by about 10 meters.

“This shift in Earth’s figure axis will cause Earth to wobble a bit differently as it rotates, but it will not cause a shift of Earth’s axis in space-only external forces such as the gravitational attraction of the sun, moon and planets can do that,” according to the NASA statement.

The estimates for both the shortening in the Earth’s rotation and shift in the figure axis are preliminary and will very likely change as more data is collected and the calculations are refined.

The March 11 earthquake was the fifth largest since 1900. So far, over 4000 people are confirmed dead and the overall death total may exceed 10,000.

Several heavily damaged nuclear reactors at the Fukushima plant are in danger of meltdown as hero workers inside put their lives on the line to avoid a catastrophic failure and try to prevent the spread of lethal radiation.

This view of Earth comes from NASA's Moderate Resolution Imaging Spectroradiometer aboard the Terra satellite

Previously, Gross had calculated the affects of the magnitude 8.8 Chilean quake in 2010 and found them to be slightly smaller compared to the Japanese quake. He calculated a shortening in the length of day of about 1.26 microseconds and shifting of Earth’s figure axis of about 8 centimeters (3 inches). These affects are dependent on the magnitude of the quake, exactly where it is located as well as how the particulars of how the fault slips.

In fact, Earth’s rotation is changing all the time as a result of continual changes in atmospheric winds and oceanic currents and these effects are about 550 times larger than the Japanese earthquake.

“Over the course of a year, the length of the day increases and decreases by about a millisecond,” says Gross. Indeed, the effects of earthquakes on changing rotation are so tiny that they are smaller than the margin of error in the measurements themselves.

By comparison, measurements of the figure axis are much more reliable and meaningful. Changes to the figure axis can be accurately measured to within about 5 centimeters. This means that the estimated 17 centimeter shift from the Japanese quake may be real after accounting for the effects of the atmospheric winds and ocean currents. Further research is needed as more data are collected and analyzed.

“These changes in Earth’s rotation are perfectly natural and happen all the time. People shouldn’t worry about them,” said Gross.

Source: NASA Press Release:

Posted on by Anne Minard

Bullseye: MESSENGER Gears Up For First-Ever Mercury Orbit

Planned footprint for the first image to be acquired from a spacecraft orbiting Mercury, on March 29, including a portion of Mercury's surface not previously seen by spacecraft. Over the subsequent six hours, MESSENGER will acquire 364 images in total before beginning to downlink the data to Earth. Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington

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When MESSENGER streaked into the early morning sky over Cape Canaveral on Aug. 3, 2004, very little was known about Mercury.

That could soon change. This week, MESSENGER — which stands for MErcury Surface, Space ENvironment, GEochemistry and Ranging — will make history when it becomes the first spacecraft to orbit Mercury.

At 8:45 p.m. EDT on Thursday, MESSENGER will execute a 15-minute maneuver that will place it into orbit around Mercury, kicking off a year-long science campaign to understand the innermost planet. The craft will fly around Mercury 730 times in the first year, and may be extended for another year after that.

No spacecraft had approached Mercury since the Mariner 10 space probe performed three fly-by maneuvers over the course of 1974 and 1975, imaging the planet’s surface. However, Mariner 10 sent back photos of only one side of the planet, leaving the other shrouded in mystery.

The MESSENGER mission — led by NASA, the Applied Physics Laboratory at Johns Hopkins University and the Carnegie Institution — is an effort to study the geologic history, magnetic field, surface composition and other mysteries of the planet. The findings are expected to broaden our understanding of rocky planets, more and more of which are being discovered in other solar systems. One of the most compelling enigmas surrounds Mercury’s magnetic field. At a diameter only slightly larger than that of the moon (about 4,800 kilometers or 2,983 miles), Mercury should have solidified to the core. However, the presence of a magnetic field suggests the planet’s insides are partially molten.

During its journey toward Mercury, MESSENGER passed the planet several times, filling in the imaging gaps left by Mariner 10. Now, the entire planet with the exception of about five percent has been observed. MESSENGER will focus its cameras on getting the best possible images of the remaining portions, mostly in the polar regions.

The in-flight preparations for this historic injection maneuver began on Feb. 8, when several heaters on the spacecraft were configured to condition the bi-propellant used during the maneuver. Starting on March 8, antennas from each of the three Deep Space Network (DSN) ground stations began a round-the-clock vigil, allowing flight control engineers at the Johns Hopkins University Applied Physics Laboratory (APL) in Laurel, Md., to monitor MESSENGER on its final approach to Mercury. Also that day, the spacecraft began executing the last cruise command sequence of the mission.  The command load executed until today. Now, the command sequence containing the orbit-insertion burn has begun.

APL is hosting a live webcast about the orbit insertion maneuver starting at 7:55 p.m. EDT on Thursday, March 17.

For those of you living near Johns Hopkins, APL and The Planetary Society will co-host a public lecture in APL’s Kossiakoff Center, featuring MESSENGER Project Scientist Ralph L. McNutt, Jr. The lecture will begin at 8 p.m. on Thursday. RSVP online.

Check Universe Today late on Thursday for coverage of the orbit insertion, with input from related talks at the Laboratory for Space Physics (LASP) in Boulder, Colorado. Meanwhile, for more information, check out NASA’s MESSENGER mission website.

Sources: NASA’s MESSENGER mission website and a press release from the University of Arizona.

Posted on by Nancy Atkinson

Hubble Rules Out One Alternative to Dark Energy

NGC 5584. Credit: NASA, ESA, A. Riess (STScI/JHU), L. Macri (Texas A&M University), and Hubble Heritage Team (STScI/AURA)

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From a NASA press release:

Astronomers using NASA’s Hubble Space Telescope have ruled out an alternate theory on the nature of dark energy after recalculating the expansion rate of the universe to unprecedented accuracy.

The universe appears to be expanding at an increasing rate. Some believe that is because the universe is filled with a dark energy that works in the opposite way of gravity. One alternative to that hypothesis is that an enormous bubble of relatively empty space eight billion light-years across surrounds our galactic neighborhood. If we lived near the center of this void, observations of galaxies being pushed away from each other at accelerating speeds would be an illusion.

This hypothesis has been invalidated because astronomers have refined their understanding of the universe’s present expansion rate. Adam Riess of the Space Telescope Science Institute (STScI) and Johns Hopkins University in Baltimore, Md., led the research. The Hubble observations were conducted by the SHOES (Supernova H0 for the Equation of State) team that works to refine the accuracy of the Hubble constant to a precision that allows for a better characterization of dark energy’s behavior. The observations helped determine a figure for the universe’s current expansion rate to an uncertainty of just 3.3 percent. The new measurement reduces the error margin by 30 percent over Hubble’s previous best measurement in 2009. Riess’s results appear in the April 1 issue of The Astrophysical Journal.

“We are using the new camera on Hubble like a policeman’s radar gun to catch the universe speeding,” Riess said. “It looks more like it’s dark energy that’s pressing the gas pedal.”

Riess’ team first had to determine accurate distances to galaxies near and far from Earth. The team compared those distances with the speed at which the galaxies are apparently receding because of the expansion of space. They used those two values to calculate the Hubble constant, the number that relates the speed at which a galaxy appears to recede to its distance from the Milky Way. Because astronomers cannot physically measure the distances to galaxies, researchers had to find stars or other objects that serve as reliable cosmic yardsticks. These are objects with an intrinsic brightness, brightness that hasn’t been dimmed by distance, an atmosphere, or stellar dust, that is known. Their distances, therefore, can be inferred by comparing their true brightness with their apparent brightness as seen from Earth.

To calculate longer distances, Riess’ team chose a special class of exploding stars called Type 1a supernovae. These stellar explosions all flare with similar luminosity and are brilliant enough to be seen far across the universe. By comparing the apparent brightness of Type 1a supernovae and pulsating Cepheid stars, the astronomers could measure accurately their intrinsic brightness and therefore calculate distances to Type Ia supernovae in far-flung galaxies.

Using the sharpness of the new Wide Field Camera 3 (WFC3) to study more stars in visible and near-infrared light, scientists eliminated systematic errors introduced by comparing measurements from different telescopes.

“WFC3 is the best camera ever flown on Hubble for making these measurements, improving the precision of prior measurements in a small fraction of the time it previously took,” said Lucas Macri, a collaborator on the SHOES Team from Texas A&M in College Station.

Knowing the precise value of the universe’s expansion rate further restricts the range of dark energy’s strength and helps astronomers tighten up their estimates of other cosmic properties, including the universe’s shape and its roster of neutrinos, or ghostly particles, that filled the early universe.

“Thomas Edison once said ‘every wrong attempt discarded is a step forward,’ and this principle still governs how scientists approach the mysteries of the cosmos,” said Jon Morse, astrophysics division director at NASA Headquarters in Washington. “By falsifying the bubble hypothesis of the accelerating expansion, NASA missions like Hubble bring us closer to the ultimate goal of understanding this remarkable property of our universe.”

Science Paper by: Adam G. Riess et al. (PDF document)