For countless generations, people have looked up at the stars and wondered if life exists somewhere out there, perhaps on planets much like ours. But it has only been in recent decades that we have been able to confirm the existence of extrasolar planets (aka. exoplanets) in other star systems. In fact, between 1988 and April 20th of 2016, astronomers have been able to account for the existence of 2108 planets in 1350 different star systems, including 511 multiple planetary systems.
Most of these discoveries have taken place within just the past three years, thanks to improvements in our detection methods, and the deployment of the Kepler space observatory in 2009. Looking ahead, astronomers hope to improve on these methods even further with the introduction of the Starshade, a giant space structure designed to block the glare of stars, thus making it easier to find planets – and perhaps another Earth!
Ask a person what Dysnomia refers to, and they might venture that it’s a medical condition. In truth, they would be correct. But in addition to being a condition that affects the memory (where people have a hard time remembering words and names), it is also the only known moon of the distant dwarf planet Eris.
In fact, the same team that discovered Eris a decade ago – a discovery that threw our entire notion of what constitutes a planet into question – also discovered a moon circling it shortly thereafter. As the only satellite that circles one of the most distant objects in our Solar System, much of what we know about this ball of ice is still subject to debate.
Discovery and Naming:
In January of 2005, astronomer Mike Brown and his team discovered Eris using the new laser guide star adaptive optics system at the W. M. Keck Observatory in Hawaii. By September, Brown and his team were conducting observations of the four brightest Kuiper Belt Objects – which at that point included Pluto, Makemake, Haumea, and Eris – and found indications of an object orbiting Eris.
Provisionally, this body was designated S/2005 1 (2003 UB³¹³). However, in keeping with the Xena nickname that his team was already using for Eris, Brown and his colleagues nicknamed the moon “Gabrielle” after Xena’s sidekick. Later, Brown selected the official name of Dysnomia for the moon, which seemed appropriate for a number of reasons.
For one, this name is derived from the daughter of the Greek god Eris – a daemon who represented the spirit of lawlessness – which was in keeping with the tradition of naming moons after lesser gods associated with the primary god. It also seemed appropriate since the “lawless” aspect called to mind actress Lucy Lawless, who portrayed Xena on television. However, it was not until the IAU’s resolution on what defined a planet – passed in August of 2006 – that the planet was officially designated as Dysnomia.
Size, Mass and Orbit:
The actual size of Dysnomia is subject to dispute, and estimates are based largely on the planet’s albedo relative to Eris. For example, the IAU and Johnston’s Asteroids with Satellites Database estimate that it is 4.43 magnitudes fainter than Eris and has an approximate diameter of between 350 and 490 km (217 – 304 miles)
However, Brown and his colleagues have stated that their observations indicate it to be 500 times fainter and between 100 and 250 km (62 – 155 miles) in diameter. Using the Herschel Space Observatory in 2012, Spanish astronomer Pablo Santo Sanz and his team determined that, provided Dysnomia has an albedo five times that of Eris, it is likely to be 685±50 km in diameter.
In 2007, Brown and his team also combined Keck and Hubble observations to determine the mass of Eris, and estimate the orbital parameters of the system. From their calculations, they determined that Dysnomia’s orbital period is approximately 15.77 days. These observations also indicated that Dysnomia has a circular orbit around Eris, with a radius of 37350±140 km. In addition to being a satellite of a dwarf planet, Dysnomia is also a Kuiper Belt Object (KBO) like Eris.
Composition and Origin:
Currently, there is no direct evidence to indicate what Dysnomia is made of. However, based on observations made of other Kuiper Belt Objects, it is widely believed that Dysnomia is composed primarily of ice. This is based largely on infrared observations made of Haumea (2003 EL61), the fourth largest object in the Kuiper Belt (after Eris, Pluto and Makemake) which appears to be made entirely of frozen water.
Astronomers now know that three of the four brightest KBOs – Pluto, Eris and Haumea – have one or more satellites. Meanwhile, of the fainter members, only about 10% are known to have satellites. This is believed to imply that collisions between large KBOs have been frequent in the past. Impacts between bodies of the order of 1000 km across would throw off large amounts of material that would coalesce into a moon.
This could mean that Dysnomia was the result of a collision between Eris and a large KBO. After the impact, the icy material and other trace elements that made up the object would have evaporated and been ejected into orbit around Eris, where it then re-accumulated to form Dysnomia. A similar mechanism is believed to have led to the formation of the Moon when Earth was struck by a giant impactor early in the history of the Solar System.
Since its discovery, Eris has lived up to its namesake by stirring things up. However, it has also helped astronomers to learn many things about this distant region of the Solar System. As already mentioned, astronomers have used Dysnomia to estimate the mass of Eris, which in turn helped them to compare it to Pluto.
While astronomers already knew that Eris was bigger than Pluto, but they did not know whether it was more massive. This they did by measuring the distance between Dysnomia and how long it takes to orbit Eris. Using this method, astronomers were able to discover that Eris is 27% more massive than Pluto is.
With this knowledge in hand, the IAU then realized that either Eris needed to be classified as a planet, or that the term “planet” itself needed to be refined. Ergo, one could make that case that it was the discovery of Dysnomia more than Eris that led to Pluto no longer being designated a planet.
Beam us up, Scotty. There’s no signs of intelligent life out there. At least, no obvious signs, according to a recent survey performed by researchers at Penn State University. After reviewing data taken by the NASA Wide-field Infrared Survey Explorer (WISE) space telescope of over 100,000 galaxies, there appears to be little evidence that advanced, spacefaring civilizations exist in any of them.
First deployed in 2009, the WISE mission has been able to identify thousands of asteroids in our solar system and previously undiscovered star clusters in our galaxy. However, Jason T. Wright, an assistant professor of astronomy and astrophysics at the Center for Exoplanets and Habitable Worlds at Penn State University, conceived of and initiated a new field of research – using the infrared data to assist in the search for signs of extra-terrestrial civilizations.
And while their first look did not yield much in the way of results, it is an exciting new area of research and provides some very useful information on one of the greatest questions ever asked: are we alone in the universe?
“The idea behind our research is that, if an entire galaxy had been colonized by an advanced spacefaring civilization, the energy produced by that civilization’s technologies would be detectable in mid-infrared wavelengths,” said Wright, “exactly the radiation that the WISE satellite was designed to detect for other astronomical purposes.”
This logic is in keeping with the theories of Russian astronomer Nikolai Kardashev and theoretical physicist Freeman Dyson. In 1964, Kardashev proposed that a civilization’s level of technological advancement could be measured based on the amount of energy that civilization is able to utilize.
To characterize the level of extra-terrestrial development, Kardashev developed a three category system – Type I, II, and III civilizations – known as the “Kardashev Scale”. A Type I civilization uses all available resources on its home planet, while a Type II is able to harness all the energy of its star. Type III civilizations are those that are advanced enough to harness the energy of their entire galaxy.
Similarly, Dyson proposed in 1960 that advanced alien civilizations beyond Earth could be detected by the telltale evidence of their mid-infrared emissions. Believing that a sufficiently advanced civilization would be able to enclose their parent star, he believed it would be possible to search for extraterrestrials by looking for large objects radiating in the infrared range of the electromagnetic spectrum.
These thoughts were expressed in a short paper submitted to the journal Science, entitled “Search for Artificial Stellar Sources of Infrared Radiation“. In it, Dyson proposed that an advanced species would use artificial structures – now referred to as “Dyson Spheres” (though he used the term “shell” in his paper) – to intercept electromagnetic radiation with wavelengths from visible light downwards and radiating waste heat outwards as infrared radiation.
“Whether an advanced spacefaring civilization uses the large amounts of energy from its galaxy’s stars to power computers, space flight, communication, or something we can’t yet imagine, fundamental thermodynamics tells us that this energy must be radiated away as heat in the mid-infrared wavelengths,” said Wright. “This same basic physics causes your computer to radiate heat while it is turned on.”
However, it was not until space-based telescopes like WISE were deployed that it became possible to make sensitive measurements of this radiation. WISE is one of three infrared missions currently in space, the other two being NASA’s Spitzer Space Telescope and the Herschel Space Observatory – a European Space Agency mission with important NASA participation.
WISE is different from these missions in that it surveys the entire sky and is designed to cast a net wide enough to catch all sorts of previously unseen cosmic interests. And there are few things more interesting than the prospect of advanced alien civilizations!
To search for them, Roger Griffith – a postbaccalaureate researcher at Penn State and the lead author of the paper – and colleagues scoured the entries in the WISE satellites database looking for evidence of a galaxy that was emitting too much mid-infrared radiation. He and his team then individually examined and categorized 100,000 of the most promising galaxy images.
And while they didn’t find any obvious signs of a Type II civilization or Dyson Spheres in any of them, they did find around 50 candidates that showed unusually high levels of mid-infrared radiation. The next step will be to confirm whether or not these signs are due to natural astronomical processes, or could be an indication of a highly advanced civilization tapping their parent star for energy.
In any case, the team’s findings were quite interesting and broke new ground in what is sure to be an ongoing area of research. The only previous study, according to the G-HAT team, surveyed only about 100 galaxies, and was unable to examine them in the infrared to see how much heat they emitted. What’s more, the research may help shed some light on the burning questions about the very existence of intelligent, extra-terrestrial life in our universe.
“Our results mean that, out of the 100,000 galaxies that WISE could see in sufficient detail, none of them is widely populated by an alien civilization using most of the starlight in its galaxy for its own purposes,” said Wright. “That’s interesting because these galaxies are billions of years old, which should have been plenty of time for them to have been filled with alien civilizations, if they exist. Either they don’t exist, or they don’t yet use enough energy for us to recognize them.”
Alas, it seems we are no closer to resolving the Fermi Paradox. But for the first time, it seems that investigations into the matter are moving beyond theoretical arguments. And given time, and further refinements in our detection methods, who knows what we might find lurking out there? The universe is very, very big place, after all.
The research team’s first research paper about their Glimpsing Heat from Alien Technologies Survey (G-HAT) survey appeared in the Astrophysical Journal Supplement Series on April 15, 2015.
With the Dawn spacecraft now heading towards the dwarf planet/asteroid Ceres, the mission has suddenly gotten even more intriguing. The Herschel space observatory has discovered water vapor around Ceres, and the vapor could be emanating from water plumes — much like those that are on Saturn’s moon Enceladus – or it could be from cryovolcanism from geysers or icy volcano.
“This is the first time water vapor has been unequivocally detected on Ceres or any other object in the asteroid belt and provides proof that Ceres has an icy surface and an atmosphere,” said Michael Küppers of ESA in Spain, lead author of a paper in the journal Nature.
Ceres might be considered to have a bit of an identity crisis, and this new discovery might complicate things even more. When it was discovered in 1801, astronomers thought it was a planet orbiting between Mars and Jupiter. Later, other bodies with similar orbits were found, marking the discovery of our Solar System’s main belt of asteroids.
Ceres laid claim as the largest asteroid in our Solar System, but in 2006, the International Astronomical Union reclassified Ceres as a dwarf planet because of its large size.
But now, could Ceres also have comet-like attributes? Herschel scientists say the most straightforward explanation of the water vapor production is through sublimation, where ice is warmed and transformed directly into gas, dragging the surface dust with it, and exposing fresh ice underneath to sustain the process. This is how comets work.
Ceres is roughly 950 kilometers (590 miles) in diameter. The best guess on Ceres composition is that it is layered, perhaps with a rocky core and an icy outer mantle. Ice had been theorized to exist on Ceres but had not been detected conclusively, until now.
Herschel used its far-infrared vision with the HIFI instrument to see a clear spectral signature of the water vapor. But, interestingly, Herschel did not see water vapor every time it looked. There were variations in the water signal during the dwarf planet’s 9-hour rotation period. The telescope spied water vapor four different times, on one occasion there was no signature. The astronomers deduced that almost all of the water vapor was seen to be coming from just two spots on the surface.
Although Herschel was not able to make a resolved image of Ceres, the team was able to derive the distribution of water sources on the surface.
“We estimate that approximately 6 kg of water vapour is being produced per second, requiring only a tiny fraction of Ceres to be covered by water ice, which links nicely to the two localised surface features we have observed,” says Laurence O’Rourke, Principal Investigator for the Herschel asteroid and comet observation programme called MACH-11, and second author on the paper.
The two emitting regions are about 5% darker than the average on Ceres. Since darker regions are able to absorb more sunlight, they are then likely the warmest regions, resulting in a more efficient sublimation of small reservoirs of water ice, the team said.
They added that this new finding could have significant implications for our understanding of the evolution of the Solar System.
“Herschel’s discovery of water vapour outgassing from Ceres gives us new information on how water is distributed in the Solar System,” said Göran Pilbratt, ESA’s Herschel Project Scientist. “Since Ceres constitutes about one fifth of the total mass of asteroid belt, this finding is important not only for the study of small Solar System bodies in general, but also for learning more about the origin of water on Earth.”
Dawn is scheduled to arrive at Ceres in the spring of 2015 after spending more than a year orbiting the large asteroid Vesta. Dawn will give us the closest look ever at Ceres surface and provide more insight into this latest finding.
“We’ve got a spacecraft on the way to Ceres, so we don’t have to wait long before getting more context on this intriguing result, right from the source itself,” said Carol Raymond, the deputy principal investigator for Dawn. “Dawn will map the geology and chemistry of the surface in high resolution, revealing the processes that drive the outgassing activity.”
We knew it was coming, but it is still sad to see the end of a mission. Controllers for the Herschel space telescope sent final commands today to put the observatory into a heliocentric parking orbit. Commands were sent at 12:25 GMT on June 17, 2013, marking the official end of operations for Herschel. But expect more news from this spacecraft’s observations, as there is still a treasure trove of data that that will keep astronomers busy for many years to come. Additionally, maneuvers done by the spacecraft allowed engineers to test out control techniques that can’t normally be tested in-flight during a mission.
You can watch a video of Herschel’s final “live” moments below:
Herschel’s science mission had already ended in April when the liquid helium that cooled the observatory’s instruments ran out.
Herschel will now be parked indefinitely in a heliocentric orbit, as a way of “disposing” of the spacecraft. It should be stable for hundreds of years, but perhaps scientists will figure out another use for it in the future. One original idea for disposing of the spacecraft was to have it impact the Moon, a la the LCROSS mission that slammed into the Moon in 2009, and it would kick up volatiles at one of the lunar poles for observation by another spacecraft, such as the Lunar Reconnaissance Orbiter. But that idea has been nixed in favor of the parking orbit.
Some of the maneuvers that were tested before the spacecraft was put into its final orbit were some in-orbit validations and analysis of hardware and software.
“Normally, our top goal is to maximise scientific return, and we never do anything that might interrupt observations or put the satellite at risk,” says Micha Schmidt, Herschel’s Spacecraft Operations Manager at the European Space Operations Center. “But the end of science meant we had a sophisticated spacecraft at our disposal on which we could conduct technical testing and validate techniques, software and the functionality of systems that are going to be reused on future spacecraft. This was a major bonus for us.”
The test requests came from other missions. For example, the ExoMars team requested doing some validations using Herschel’s Visual Monitoring Camera since ExoMars will have a similar camera, and the Euclid spacecraft team asked for some reaction wheel tests.
On May 13-14, engineers commanded Herschel to fire its thrusters for a record 7-hours and 45-minutes. This ensured the satellite was boosted away from its operational orbit around the L2 Sun–Earth Lagrange Point and into a heliocentric orbit, further out and slower than Earth’s orbit. This depleted most of the fuel, and the final thruster command today used up all of the remaining fuel. Today’s final command was the last step in a complex series of flight control activities and thruster maneuvers designed to take Herschel into a safe disposal orbit around the Sun; additionally all its systems were turned off.
“Herschel has not only been an immensely successful scientific mission, it has also served as a valuable flight operations test platform in its final weeks of flight. This will help us increase the robustness and flexibility of future missions operations,” said Paolo Ferri, ESA’s Head of Mission Operations. “Europe really received excellent value from this magnificent satellite.”
The Great Orion Nebula has captivated observers for at least four hundred years, but the ancient Mayans may have known about its secrets long before then. According to legend, the nebula might have been the smoke situated between the “Three Hearthstones” and the light of the emerging stars seen as the very embers of creation itself. Now the ESO-operated Atacama Pathfinder Experiment (APEX) in Chile has revealed what we cannot see. At wavelengths too long for human vision, this new image shows us an ancient fire dance painted in colors of cold interstellar dust.
As we know, deposits of gas and interstellar dust are virtual star factories. However, the very material which creates stars also masks them. So how do we peer behind the veil? The answer is to observe at alternative wavelengths of light. In this case, the submillimetre wavelength reveals what our eyes cannot see… dust grains igniting the view, even though they are just a few tens of degrees above absolute zero. This makes the APEX telescope with its submillimetre-wavelength camera LABOCA, located at an altitude of 5000 metres above sea level on the Chajnantor Plateau in the Chilean Andes, the perfect instrument to play the tune for this cold fire dance.
Take a look around the picture. It’s just a small portion of a vast complex known as the Orion Molecular Cloud. Wafting across hundreds of light years space some 1350 light years away, this rich arena of hot young stars, cold dust clouds and bright nebula is the epitome of stellar creation. The image reveals the submillimetre-wavelength glow in shades of orange and it is combined with visible light for a total visual experience. Note deep ribbons, sheets and bubbles… These are the product of gravitational collapse and the effects of stellar winds. Powerful stellar processes are at work here. The atmospheres of the stars are crafting the clouds much the same way a gentle breeze swirls the smoke from a fire.
As beautiful as it is, there is still science behind the imagery. Astronomers have employed the data taken with ESA’s Herschel Space Observatory, along with the APEX information, to aid them in their search for early star formation. At this point in time, the researchers have been able to verify more than a dozen candidate protostars – objects which appear far brighter at longer wavelengths rather than short. It’s a triumph for the researchers. These new observations could well be the youngest protostars so far observed and it brings astronomers just one step closer to witnessing the moment when a star ignites.
It’s a simple menu, but smoking hot. The black hole at the center of the Milky Way galaxy is sucking in ultra-hot molecular gas, as seen through the eyes of the Herschel space telescope.
“The biggest surprise was quite how hot the molecular gas in the innermost central region of the galaxy gets. At least some of it is around 1000ºC [1832º F], much hotter than typical interstellar clouds, which are usually only a few tens of degrees above the –273ºC [-460ºF] of absolute zero,” stated the European Space Agency.
Herschel, which is out of coolant and winding down its scientific operations, will continue producing results in the next few years as scientists crunch the results. The telescope has found a bunch of basic molecules in the Milky Way that include water vapour and carbon monoxide, and has been engaged in looking to learn more about the gas that surrounds the massive black hole at our galaxy’s center.
In a region called Sagittarius* (Sgr A*), this huge black hole — four million times the mass of the sun — is thankfully a safe distance from Earth. It’s 26,000 light years away from the solar system.
Trouble is, there’s a heckuva lot of dust blocking our view to the center of the galaxy. Herschel got around that problem by taking pictures in the far-infrared, seeking heat signatures that can bely intense activity in and around the black hole.
“Herschel has resolved the far-infrared emission within just 1 light-year of the black hole, making it possible for the first time at these wavelengths to separate emission due to the central cavity from that of the surrounding dense molecular disc,” stated Javier Goicoechea of the Centro de Astrobiología, Spain, lead author of a paper reporting the results.
The science team supposes that there are strong shocks within the gas (which is magnetized) that help turn up the heat. The shocks could occur when gas clouds butt up against each other, or material shoots out Fast and Furious-style between stars and protostars (young stars.)
“The observations are also consistent with streamers of hot gas speeding towards Sgr A*, falling towards the very center of the galaxy,” stated Goicoechea. “Our galaxy’s black hole may be cooking its dinner right in front of Herschel’s eyes.”
A large comet that peppered Jupiter two decades ago brought water into the giant planet’s atmosphere, according to new research from the Herschel space observatory.
Shoemaker-Levy 9 astounded astronomers worldwide when its 21 fragments hit Jupiter in June 1994. The event was predicted and observatories were trained on Jupiter as the impact occurred. The dark splotches the comet left behind were even visible in small telescopes. But apparently, those weren’t the only effects of the collision.
Herschel’s infrared camera revealed there is two to three times more water in the southern hemisphere of the planet, where the comet slammed into the atmosphere, than in the northern hemisphere. Further, the water is concentrated in high altitudes, around the various sites where Shoemaker-Levy 9 left its mark.
It is possible, researchers acknowledged, that water could have come from interplanetary dust striking Jupiter, almost like a “steady rain.” If this were the case, however, scientists expect the water would be evenly distributed and also would have filtered to lower altitudes. Jupiter’s icy moons were also in the wrong locations, researchers said, to have sent water towards the massive planet.
Internal water rising up was ruled out because it cannot penetrate the “cold trap” between Jupiter’s stratosphere and cloud deck, the researchers added.
“According to our models, as much as 95 percent of the water in the stratosphere is due to the comet impact,” said Thibault Cavalié of the Astrophysical Laboratory of Bordeaux, in France, who led the research.
While researchers have suspected for years that Jupiter’s water came from the comet — ESA’s Infrared Space Observatory saw the water there years ago — these new observations provide more direct evidence of Shoemaker-Levy 9’s effect. The results were published in Astronomy and Astrophysics.
Herschel’s find provides more fodder for two missions that are scheduled for Jupiter observations in the coming few years. The first goal for NASA’s Juno spacecraft, which is en route and will arrive in 2016, is to figure out how much water is in Jupiter’s atmosphere.
Additionally, ESA’s Jupiter Icy moons Explorer (JUICE) mission is expected to launch in 2022. “It will map the distribution of Jupiter’s atmospheric ingredients in even greater detail,” ESA stated.
While ESA did not link the finding to how water came to be on Earth, some researchers believe that it was comets that delivered the liquid on to our planet early in Earth’s history. Others, however, say that it was outgassing from volcanic rocks that added water to the surface.
Mars appeared to be full of water in the ancient past, as evidenced by a huge, underground trench recently discovered by scientists. There is frozen water at the Martian poles, and both the Curiosity and Spirit/Opportunity rover missions have found evidence of flowing water on the surface in the past.
The outer solar system also has its share of water, including in all four giant planets (Jupiter, Saturn, Uranus and Neptune) and (in ice form) on various moons. Even some exoplanets have water vapor in their atmospheres.
“All four giant planets in the outer solar system have water in their atmospheres, but there may be four different scenarios for how they got it,” added Cavalié. “For Jupiter, it is clear that Shoemaker-Levy 9 is by far the dominant source, even if other external sources may contribute also.”
Most of the early galaxies that astronomers have been able to observe are small with a low-to-moderate amount of star production. But now the Herschel Space Observatory has found a massive dust-filled galaxy churning out stars at an incredible rate, with all of this taking place back when the cosmos was a just 880 million years old. The galaxy is about as massive as our Milky Way, but produces stars at a rate 2,000 times greater, prompting the researchers to call it a “maximum-starburst” galaxy.
The astronomers involved in its discovery say its mere existence challenges our theories of galaxy evolution.
“Massive, intense starburst galaxies are expected to only appear at later cosmic times,” says Dominik Riechers, currently an assistant professor at Cornell. “Yet, we have discovered this colossal starburst just 880 million years after the Big Bang, when the universe was at little more than 6 percent of its current age. Riechers is the first author of the paper describing the findings in the April 18 issue of the journal Nature.
The prevailing thought on early galaxy and star formation has been that the first galaxies to form were relatively small and lightweight, containing only a few billion times the mass of our Sun. They form their first stars at rates of a few times that experienced by the Milky Way today, and the galaxies would grow by merging with other small galaxies. In theory, galaxies as massive as the newly found galaxy – named HFLS3 — should not be present so soon after the Big Bang.
HFLS3 appears as little more than a faint, red smudge in images from the Herschel Multi-tiered Extragalactic Survey (HerMES).
The extreme distance to HFLS3 means that its light has travelled for almost 13 billion years across space before reaching us. We therefore see it as it existed in the infant Universe, just 880 million years after the Big Bang or at 6.5% of the Universe’s current age.
Even at that young age, HFLS3 was already close to the mass of the Milky Way, with roughly 140 billion times the mass of the Sun in the form of stars and star-forming material. After another 13 billion years, it should have grown to be as big as the most massive galaxies known in the local Universe.
“Looking for the first examples of these massive star factories is like searching for a needle in a haystack; the Herschel dataset is extremely rich,” said Riechers.
Tens of thousands of massive, star-forming galaxies have been detected by Herschel as part of HerMES and sifting through them to find the most interesting ones is a challenge.
“This particular galaxy got our attention because it was bright, and yet very red compared to others like it,” said co-investigator Dave Clements of Imperial College London.
While the discovery of this single galaxy isn’t enough to overturn current theories of galaxy formation, finding more galaxies like this one could challenge those theories, the astronomers say. At the very least, theories will have to be modified to explain how this galaxy formed, Riechers says.
“This galaxy is just one spectacular example, but it’s telling us that extremely vigorous star formation was possible early in the universe,” says Jamie Bock, professor of physics at Caltech and a coauthor of the paper.
Artist concept of Ebb and Flow, the two GRAIL spacecraft in orbit of the Moon. Credit: NASA
The Herschel space telescope is slated to be decommissioned next March as the observatory’s supply of cryogenic helium will be depleted. One idea for “disposing” of the spacecraft was to have it impact the Moon, a la the LCROSS mission that slammed into the Moon in 2009, and it would kick up volatiles at one of the lunar poles for observation by another spacecraft, such as the Lunar Reconnaissance Orbiter. However, that idea has been nixed in favor of parking Herschel in a heliocentric orbit. But don’t be disappointed if you were hoping for a little lunar fireworks. There will soon be a double-barreled event as the twin GRAIL spacecraft will impact the moon’s surface on December 17, 2012.
NASA will be providing more information about the GRAIL spacecrafts’ impacts at a briefing on Thursday, but the Gravity Recovery and Interior Laboratory (GRAIL) team said last week that they were still formulating ideas for the impact scenario, and looking at the possibility of aiming the crashes so they are within the field-of-view of instruments on LRO. The two spacecraft are running out of fuel – Principal Investigator Maria Zuber said they have to do three maneuvers every day to keep the spacecraft from slamming into the Moon on their own – and earlier this year the duo were lowered from their prime mission orbit of 55 kilometers above the Moon to 23 km, and this week were lowered to 11 km to enable even higher resolution data.
The two spacecraft have been providing unprecedented detail about the Moon’s internal structure as they send radio signals to each other and monitor any changes in distance between the two as they circle the Moon. Changes as small as 50 nanometers per second have been measured, and last week the team detailed how they were able to create the most detailed gravity map of the Moon, as well as make determinations that the Moon’s inner crust is nearly pulverized.
We’ll provide more information about the GRAIL impacts when it becomes available, but preliminary details are that the impacts will take place on Dec. 17 at 19:28 UTC (2:28 p.m. EST).
The impact by LCROSS (Lunar Crater Observation and Sensing Satellite) confirmed the presence of water ice and an array of volatiles in a permanently shadowed crater at the Moon’s South Pole, and it is expected GRAIL would be targeted for similar observations.
Artist’s concept of Herschel at the L2 libration point one million miles from Earth. Credit: ESA
The Herschel team had said earlier this year that because the cryogenic superfluid helium coolant is running out — and the spacecraft needs to be at temperatures as low as 0.3 Kelvin, or minus 459 degrees Fahrenheit to make its observations — one idea of getting rid of the spacecraft would be to impact it on the Moon. This week, they posted on the Herschel website that ‘the lunar impact option is feasible, but carries an additional cost on top of that of the heliocentric orbit option. The ESA Executive has decided that the Herschel spacecraft will be “parked” indefinitely in heliocentric orbit.”
The Herschel operational large halo orbit around L2 is unstable, and so the orbit needs regular “maintenance,” and consequently, after end-of-helium (expected in March 2013), the spacecraft will need to be “parked” somewhere else with no need of orbit maintenance.
Herschel team member Chris North told Universe Today that the mission operators needed to get some engineering tests done to determine if the Moon impact was feasible. “Basically they hand it over to engineers who do things that are considered too risky during the scientific mission itself – e.g. test the attitude control to its limits to see what it can withstand!” North said via email. He added that most people he had spoken with were all for the impact, — having it “go out in a blaze of glory.”
But, surprisingly, the costs for impact are greater than leaving it in a parking orbit for a few hundred years. It’s orbit may have to be maintained again in the future, as some estimates put it at potentially impacting Earth at some point in several hundred years.
And for anyone worried that a lunar impact by the GRAIL spacecraft will “hurt” the Moon, one look at the Moon shows that it has been hit in the past and continues to get impacted by asteroids and meteoroids, with no adverse affect to its orbit.
As LCROSS principal investigator Tony Colaprete said about the LCROSS impact, “What we’re doing with the Moon is something that occurs naturally four times a month on the Moon, whether we’re there or not. The difference with LCROSS is that it is specifically targeted at a certain spot, Cabeus crater,” and that the laws of physics mean there will be a miniscule perturbation.
Even though the Centaur rocket stage that hit the Moon was expect to kick up about 350 tons of lunar regolith, “The impact has about 1 million times less influence on the Moon than a passenger’s eyelash falling to the floor of a 747 jet during flight,” Colaprete said.
The two GRAIL spacecraft are about the size of washing machines, much smaller than the Centaur rocket, so will have less of an impact.