If you look to the morning sky – to the east that is, as the sun’s rising – you will notice a bright star in the firmament, one that should not be there. Theoretically, stars only come out at night and should be well on their way to bed by the time the sun rises, correct? Well, that’s because the Morning Star, as it’s known, isn’t a star at all, but the planet Venus. It is both the morning and evening star, the former when it appears in the east during sunrise and the latter when it appears in the west during sunset. Because of its unique nature and appearance in the sky, this “star” has figured prominently in the mythologies of many cultures.
In ancient Sumerian mythology, it was named Inanna (Babylonian Ishtar), the name given to the goddess of love and personification of womanhood. The Ancient Egyptians believed Venus to be two separate bodies and knew the morning star as Tioumoutiri and the evening star as Ouaiti. Likewise, believing Venus to be two bodies, the Ancient Greeks called the morning star Phosphoros (or Eosphoros) the “Bringer of Light” (or “Bringer of Dawn”) and the evening star they called Hesperos (“star of the evening”). By Hellenistic times, they had realized the two were the same planet, which they named after their goddess of love, Aphrodite. The Phoenicians, never ones to be left out where astronomy and mythology were concerned, named it Astarte, after their own goddess of fertility. In Iranian mythology, especially in Persian mythology, the planet usually corresponds to the goddess Anahita, and sometimes AredviSura, the goddesses of fertility and rivers respectively. Mirroring the ancient Greeks, they initially believed the planet to be two separate objects, but soon realized they were one.
The Romans, who derived much of their religious pantheon from the Greek tradition and near Eastern tradition, maintained this trend by naming the planet Venus after their goddess of love. Later, the name Lucifer, the “bringer of light”, would emerge as a Latinized form of Phosphoros (from which we also get the words phosphorus and phosphorescence). This would prove influential to Christians during the Middle Ages who used it to identify the devil. Medieval Christians thusly came to identify the Morningstar with evil, being somewhat more concerned with sin and vice than fertility and love! However, the identification of the Morningstar as a symbol of fertility and womanhood remains entrenched, best demonstrated by the fact that the astronomical symbol for Venus happens to be the same as the one used in biology for the female sex: a circle with a small cross beneath.
The Morningstar also figures prominently in the mythology of countless other cultures, including the Mayans, Aborigines, and Maasai people of Kenya. To all of these cultures, the Morningstar still serves as an important spiritual, agricultural and astrological role. To the Chinese, Japanese, Koreans and Vietnamese, she is known literally as the “metal star”, based on the Five Elements.
We have written many articles about the Morning Star for Universe Today. Here’s an article about how to find Venus in the sky, and here’s an article about the brightest planet.
Shuttle Discovery still on the launchpad. Credit: Alan Walters (awaltersphoto.com) for Universe Today.
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UPDATE: The launch has now been delayed until Nov. 30, as a crack was found in the foam on Discovery’s external tank after the fuel was offloaded this morning. Engineers posting on Twitter said the hydrogen leak this morning may have been a lucky break, as the crack had ice underneath and may have easily come off during launch. The crack was not seen previously.
It seems as through space shuttle Discovery keeps coming up with excuses to delay the launch of her final mission to space, and the launch pad facilities and weather are conspiring along with her. Originally scheduled to launch on Nov. 1, this latest delay comes from a hydrogen leak in a vent arm attached to the shuttle’s external tank. The work required will push back any further launch attempt until at least Monday, Nov. 8. That is the last day available in the current launch window, and if it doesn’t launch then the window closes until Nov. 30, due to unfavorable sun angles for when the shuttle would be docked to ISS.
This is not the first time a leak has occurred in the vent arm, but this time the leak was “substantial” said Launch Director Mike Leinbach.
“The signature of the leak is similar to what we’ve seen in the past when we’ve had leaks there, although the magnitude was higher this time and it occurred earlier in our tanking process,” he said.
Discovery’s 11-day mission to the International Space Station will bring a new storage module and the first humanoid robot, Robonaut 2, or R2 to the station. The Nov. 8 launch time is now scheduled for 12:53 Eastern STANDARD Time (17:53 UT).
Previous delays have stemmed from leaks in different systems, an electrical glitch and rainy, windy weather.
The launch scrubs have disappointed participants of the launch Tweet-up, where NASA allows Twitterers a chance to view a launch from Kennedy Space Center. While some of the participants are waiting out the delays, most have had to return home. This marks the first time there has been a launch delay when NASA has held a Tweet-up for a shuttle liftoff.
If you are needing to see a launch, try keeping an eye on a Delta II rocket launch from Vandenberg Air Force Base in California, with the COSMO Earth observing satellite. This rocket, too has had its share of delays, but is now slated for launch on Friday, Nov. 5 at 10:20 pm EDT (7:20 pm PDT).
Eyes on the Solar System - a 3d environment browser application that operates in real time, letting you see what our robot spacecraft are up to.
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NASA’s beta version of Eyes on the Solar System, built by JPL and Caltech, offers a neat way of tracking a range of current space missions – for example, as Nancy Atkinson mentioned yesterday, you can follow EPOXI’s flyby of comet Hartley 2. Reminiscent of Celestia, this browser application gives you a 3D environment running in real time and is updated regularly with NASA spacecraft mission data.
To get it operating, you can just click to the NASA link where you are prompted to install a Unity Web Player plug-in. This is fast and straight forward, from my experience. I did strike a problem with a certain small and squishy 64bit system that starts with X (where the menu text didn’t display correctly), but it ran fine on other systems. It is a beta version after all – and I feel obliged to note you should load at your own risk, yada, yada.
Anyhow, if you choose to proceed, you can then move around the solar system with left mouse click-hold and scroll wheel actions – or there’s the usual keyboard alternatives, or even on-screen controls. In default mode, a number of celestial bodies are shown and labeled, as are several spacecraft, which you can zoom over to by clicking on them. You can add more objects from the Visual Controls menu. Default settings have comets hidden, so you’ll need to add them to do an EPOXI-Hartley 2 encounter simulation.
There are some online tutorials you can take from the opening screen – which are short and useful – to get a quick run-through of the options available.
Eyes - in photo mode - showing EPOXI on approach to Hartley 2. If you're not a purist, you can also back-light an image. For example, to light up EPOXI in this image - where the Sun is not at the right angle to do it.
Like Celestia, you can speed up, slow down and move back and forth through time. This means you can replay EPOXI’s closest approach to Hartley 2 – or go right back to 1997 and zoom out to watch Cassini leave Earth and travel to Saturn via Venus and Earth flybys until it reaches Saturn in 2004 – all of which you can enjoy in about 5 seconds after cranking up the passage of time. You can also pick an ‘over the shoulder’ view to ride with Cassini through the F and G rings on its first approach to Saturn.
Unlike Celestia, because Eyes is mainly about spacecraft missions, its environment only covers the period from 1950 to 2050 and (curses) I couldn’t find any options to add in fictional spacecraft.
For a bit of edu-tainment you can access right-click controls which allow you to measure distances between objects – and monitor how those distances change as the objects move over time. For a bit of fun, you can also compare spacecraft to scale objects – with a choice between scientist, Porsche and football stadium. As one of the brief tutorials will explain, Voyager 1 is about the size of a Porsche.
The image shows the first area of sky viewed as part of the Herschel-ATLAS survey. The five inset show enlarged views of the five distant galaxies whose images are being gravitationally lensed by foreground galaxies (unseen by Herschel). The distant galaxies are not only very bright, but also very red in colour in this image, showing that they are brighter at the longer wavelengths measured by the SPIRE instrument. Image credits: ESA/SPIRE/Herschel-ATLAS/SJ Maddox (top); ESA/NASA/JPL-Caltech/Keck/SMA (bottom).
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One of the predictions of Einstein’s predictions from general relativity was that gravity could distort space itself and potentially, act as a lens. This was spectacularly confirmed in 1919 when, during a solar eclipse, Arthur Eddington observed stars near the Sun were distorted from their predicted positions. In 1979, this effect was discovered at much further distances when astronomers found it to distort the image of a distant quasar, making one appear as two. Several other such cases have been discovered since then, but these instances of gravitational lensing have proven difficult to find. Searches for them have had a low success rate in which less than 10% of candidates are confirmed as gravitational lenses. But a new method using data from Herschel may help astronomers discover many more of these rare occurrences.
The Herschel telescope is one of the many space telescopes currently in use and explores the portion of the spectrum from the far infrared to the submillimeter regime. A portion of its mission is to produce a large survey of the sky resulting in the Herschel ATLAS project which will take deep images of over 550 square degrees of the sky.
While Herschel explores this portion of the electromagnetic spectrum in far greater detail than its predecessors, in many ways, there’s not much to see. Stars emit only very faintly in this range. The most promising targets are warm gas and dust which are better emitters, but also far more diffuse. But it’s this combination of facts that will allow Herschel to potentially discover new lenses with improved efficiency.
The reason is that, although galaxies lack strong emission in this regime in the modern universe, ancient galaxies gave off far more since during the first 4 billion years. During that time, many galaxies were dominated by dust being warmed by star formation. Yet due to their distance, they too should be faint… Unless a gravitational lens gets in the way. Thus, the majority of small, point-like sources in the ALTAS collection are likely to be lensed galaxies. As Dr Mattia Negrello, of the Open University and lead researcher of the study explains, “The big breakthrough is that we have discovered that many of the brightest sources are being magnified by lenses, which means that we no longer have to rely on the rather inefficient methods of finding lenses which are used at visible and radio wavelengths.”
These panels show a zoom of one of the lenses, with high resolution images from Keck (optical light, blue) and the submillimeter Array (sub-millimetre light, red). Image credits: ESA/NASA/JPL-Caltech/Keck/SMA
Already, this new technique has turned up at least five strong candidates. A paper, to be published in the current issue of Science discusses them. Each of them received followup observations from the Z-Spec spectrometer on the California Institute of Technology Submillimeter Observatory. The furthest of these these objects, labeled as ID81, showed a prominent IR spectral line had a redshift of 3.04, putting it at a distance of 11.5 billion lightyears. Additionally, each system showed the spectral profile of the foreground galaxy, demonstrating that the combined light received was indeed two galaxies and the bright component was a gravitational lens.
This method of using gravitational lenses will allow the Herschel team to probe distant galaxies in detail never before achieved. As with all telescopes, longer wavelengths of observations result in less resolution which means that, even if one of the distant systems were to be broken into distinct portions, Herschel would be unable to resolve them. But the fact that we can see them at all means their spectral signatures of the galaxies as a whole can still be studied. Additionally, as Professor Steve Eales from Cardiff University and the other leader of the survey noted: “We can also use this technique to study the lenses themselves.” This potential to explore the mass of the nearby galaxies may help astronomers to understand and constrain the enigmatic Dark Matter that makes up ~80% of the mass in our universe.
Dr Loretta Dunne of Nottingham University and joint-leader of the Herschel-ATLAS survey adds, “What we’ve seen so far is just the tip of the iceberg. Wide area surveys are essential for finding these rare events and since Herschel has only covered one thirtieth of the entire Herschel-ATLAS area so far, we expect to discover hundreds of lenses once we have all the data. Once found, we can probe the early Universe on the same physical scales as we can in galaxies next door.”
Chandrayaan-1 3D color photo sent by the Moon Mineralogy Mapper. Credit: ISRO
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Scientists analyzing data from the Moon Mineralogy Mapper instrument or M Cubed, on the Chandrayann-1 spacecraft found two different kinds of never-before-seen lunar rocks – one hidden in a basin on the far side of the Moon and the other staring right at us on the near side. Just four minerals — plagioclase feldspar, pyroxene, olivine, and ilmenite — account for 98-99% of the crystalline material of the lunar crust, but the composition of these newly found rocks are two different kinds of spinels, a magnesium spinel and a chromite spinel. The composition and location of these new rock types are extremely puzzling, and lunar scientists are trying to determine more details about these mysterious Moon rocks.
Universe Today talked with Dr. Carle Pieters from Brown University who is the Principal Investigator for M Cubed as well as Dr. Jessica Sunshine from the University of Maryland, a co- investigator with the project.
Universe Today: Dr. Pieters, tell us about the newly found rocks on the far side.
Dr. Carle Pieters: The rock type on the far side of the Moon that is so unusual is a magnesium spinel, which typically has iron, magnesium, and aluminum oxide. In looking in detail at the spectral properties of the Moscoviense Basin on the far side — and in particular the material along the inner-most ring of this basin — we noticed there were a few little areas that were spectroscopically unusual. So, of course we investigated those in more detail. We saw three primary different compositions, and two we understand and had seen elsewhere, and they are rich in iron bearing minerals called pyroxene and olivine, and we saw small areas of these that are widely separated.
But then the third kind of mineral, the magnesium spinel, we had never seen before on the Moon, and what is interesting is not only is there an unusual abundance of this particular mineral, but it also has a lack of the pyroxenes and olivines that we see elsewhere. So there are several mysteries that are interwoven here. One, is why do we have a concentration of this spinel mineral and however it got concentrated in this area, why aren’t the other minerals that we are familiar with also there, because they are not.
So this is a big mystery and it is a very exciting one because now we have to reexamine our understanding of the character of the lunar crust, in particular to the depths that might have been tapped by this enormous basin and that we are now looking at as exposed on the surface.
Universe Today: So, what does this tell you about this region on the Moon?
Pieters: Not only are these unusual areas compositionally, and they are only about a kilometer or two in size, but in every method we’ve been able to look at thus far, in every wavelength and resolution, they have no other distinguishing properties. Typically, on the Moon to indentify an usual composition we look for a fresh crater that has excavated and exposed material on the surface of the Moon. These areas have no fresh craters, no disturbance at all across their surface, even at the highest resolution that is seen with the LROC (Lunar Reconnaissance Orbiter Camera) instrument which measures a half a meter resolution.
These are old surfaces that have been undisturbed but have an extremely unusual composition. And even the space weathering that has occurred on the surface throughout the billions of years of history on the Moon has not erased their unusual compositions. So, they are unusual for the kind of compositions we see, but they are also unusual because they have no identifying property that allows us to identify them in our imagery which is quite unusual for features on the surface of the Moon.
In the dark mantle deposits of the Sinus Aestuum (left), deposits of chromite spinel light up like beacons (right), but the nearby Rima Bode has no spinel. Credit: Jessica Sunshine, University of Maryland
Universe Today: Now let’s move to the near side of the Moon, where Dr. Jessica Sunshine and her team went looking for unusual data.
Dr. Jessica Sunshine: One of the things I was asked to be in charge of was looking for anomalies, things that just didn’t look like the rest of the Moon. And of course you never know what’s going to happen under those circumstances. Carle had already discovered there seemed to be a magnesium spinel on the far side of the Moon and I went looking to see where else it could be. We found that the only place that we had anything that looked like the spinel mineral in the data we had was on the near side and it was an extremely large deposit in the middle of the central nearside, almost exactly dead center at zero-zero. And we started looking a little more carefully and realized that it wasn’t really the same kinds of things that Carle found, which truly was a new rock type on the far side of the Moon, but something really usual about the region.
We had already known the region was full of what we call dark mantle deposits or pyroclastic deposits, which is firefountaining deposits. This came from explosive eruptions of lava and gas over large areas of the Moon, about the size of Massachusetts. And we knew that three of them were there, it just turned out that one of them was compositionally different from the other ones, and in particular it had the kind of spinel which is a chromite, because it has chrome in it, and now we’re busy trying to figure out why this deposit is different from the one next door, and what does it mean. And we’re still working that process out as we speak.
Universe Today: What is it like to find something new like this on the side of the Moon that humans have been able to see for thousands of years?
Sunshine: Yes, I tend to title my talks on the subject something like, “Hidden in Plain Sight” because they are! It’s right there and I think this is a really fascinating part of this because we have been starring at the Moon, as humanity for millennia and if our eyes were slightly different we would see this one really dark spot in the middle of the Moon that is different from anywhere else.
Universe Today: What specifically about the Chandrayaan-1 spacecraft and the Mcubed instrument made these discoveries possible?
Sunshine: M Cubed collects data over a much broader range of light than our human eyes can. We can all see the rainbow, we’re all familiar with that, from blue to red, but there is light at shorter wavelengths, which we call ultraviolet, and particularly for this case, there is light at shorter wavelengths called infrared. M Cubed goes farther into the infrared than humans can see and it is there we are able to see diagnostic fingerprints of different kinds of minerals. So I suspect there are certain kinds of bugs who would look at the Moon and would have known these deposits are there because their vision goes into the infrared!
Universe Today: So, Dr. Pieters, does these new discoveries tell us there are still more mysteries to find on the Moon?
Pieters: Oh, absolutely! We’ve just barely scratched the surface here. This is thrilling from a spectroscapist’s point of view, of course, but also from someone who is trying to understand how planets work, and in particular how this wonderful small body in our neighborhood is telling us about the characteristics of crustal evolution and fundamental properties of planetary surfaces.
You can listen to a version of this interview on the 365 Days of Astronomy podcast and the NASA Lunar Science Institute podcasts
At best, the few extrasolar planets we have imaged directly are just points of light. But what can that light tell us about the planet? Maybe more than we thought. As you probably know the, Deep Impact spacecraft flew by comet Hartley 2 today, taking images from only 700 km away. But maneuvering to meet up with the comet is not the only job this spacecraft has been doing. The EPOXI mission also looked for ways to characterize extrasolar planets and the team made a discovery that should help identify distinctive information about extrasolar planets. How did they do it? By using the Deep Impact spacecraft to look at the planets in our very own solar system.
The spacecraft imaged the planetary bodies in our solar system — in particular the Earth, Mars and our Moon — (see here for movies of the Moon transiting Earth) and astronomer Lucy McFadden and UCLA graduate Carolyn Crow compared the reflected red, blue, and green light and grouped the planets according to the similarities they saw. The planets fall into very distinct regions on this plot, where the vertical direction indicates the relative amount of blue light, and the horizontal direction the relative amount of red light.
This suggests that when we do have the technology to gather light from individual exoplanets, astronomers could use color information to identify Earth-like worlds. “Eventually, as telescopes get bigger, there will be the light-gathering power to look at the colors of planets around other stars,” McFadden says. “Their colors will tell us which ones to study in more detail.”
On the plot, the planets cluster into groups based on similarities in the wavelengths of sunlight that their surfaces and atmospheres reflect. The gas giants Jupiter and Saturn huddle in one corner, Uranus and Neptune in a different one. The rocky inner planets Mars, Venus, and Mercury cluster off in their own corner of “color space.”
But Earth really stands out, and its uniqueness comes from two factors. One is the scattering of blue light by the atmosphere, called Rayleigh scattering, after the English scientist who discovered it. The second reason Earth stands out in color is because it does not absorb a lot of infrared light. That’s because our atmosphere is low in infrared-absorbing gases like methane and ammonia, compared to the gas giant planets Jupiter and Saturn.
“It is Earth’s atmosphere that dominates the colors of Earth,” Crow says. “It’s the scattering of light in the ultraviolet and the absence of absorption in the infrared.”
So, this filtering approach could provide a preliminary look at exoplanet surfaces and atmospheres, giving us an inkling of whether the planet is rocky or a gas planet, or what kind of atmosphere it has.
EPOXI is a combination of the names for the two extended mission components for the Deep Impact spacecraft: the first part of the acronym comes from EPOCh, (Extrasolar Planet Observations and Characterization) and the flyby of comet Hartley 2 is called the Deep Impact eXtended Investigation (DIXI).
Comet Hartley as seen by the EPOXI spacecraft at closest approach. Credit: NASA
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NASA’s Deep Impact spacecraft came within 700 kilometers (435 miles) of Comet Hartley 2 at 10:01 a.m. EDT (1401 GMT) today, imaging with several cameras. Here are the first pictures released of the closest approach.
The scientific team watched along with viewers online and on NASA TV as the images were returned to Earth, about an hour after the spacecraft made its closest approach. First impressions? It is a peanut with jets.
“This is a type of moment that scientists live for,” said JPL’s Don Yeomans, “to get new results in such a dramatic fashion. The images are clear, taken as spacecraft was approaching, then as it swung past and moved away.”
The Sun is off to right, and visible is the icy surface of the comet throwing dust and gas towards the Sun.
Another view of Comet Hartley 2 during EXPOXI close approach. Credit: NASA
More images will be coming down from the spacecraft and Yeomans said the scientists will be examining Hartley 2, looking for the origination spots of the jets. “Are the jets coming from the surface, or is it coming from well beneath where heat of Sun reaches into the comet? We’ll be looking for how many jets, or if possibly the whole comet outgassing. There is a single obvious jet coming off towards the Sun, but also you can see one at the 7 o’clock position, which was evident in previous images, too.”
Image of Hartley 2 as the EXPOXI spacecraft moved away from comet. Credit:NASA
The spacecraft uses several high-resolution instruments, and one camera can image the entire comet with a resolution of about seven meters (about 23 feet) per pixel. The spacecraft also acquired 199 medium-resolution images.
From previous images taken by EPOXI from a distance and radar images taken from the ground, scientists knew Hartley 2 was a bi-lobate comet, which means peanut- or pickle-shaped. But they didn’t know if it was a solid surface or a contact binary, where two smaller cometesimals were stuck together.
But, Yeomans said, these images show the comet is of a solid, one-piece construction.
EPOXI Principal Investigator Mike A’Hearn agreed. “Every time we go to a comet they are full of big surprises,” he said. “The comets we’ve seen up close all seem to work the same way, but they look very different so there must be some fundamental differences in the ways they work. It could be they came from different parts of the early solar system or that they evolved very differently. Finding out how the solar system formed is really what we want out of this.”
The discoverer of Hartley 2, Malcolm Hartley, was on hand at JPL for the closest approach. He found the comet 26 years ago as a smudge on photographic plates taken at the Siding Spring Observatory in Australia. “I was doing quality control of photographic plates and I noticed faint object with a telltale glow like a comet,” said Hartley, who still works at the same observatory. “It has been very interesting to be here, and it has been interesting for the science team and quite a challenge for the engineers. There’s going to be enough data downloaded to keep researchers busy for several years.”
The crew of STS-133 will have to wait a little longer for their date with destiny - this time thanks to weather. Photo Credit: NASA/Kim Shiflett
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Discovery’s final flight faced its first hurdle in the form of a fuel leak in its right OMS pod. This problem seemed solved, but using an over-abundance of caution mission managers had the seals around the affected flange replaced. Then unrelated leaks of hydrogen and helium pushed the launch back to Nov. 2 and then Nov. 3. With that problem resolved many thought Discovery’s problems were behind her – enter a voltage issue in the number three engine’s backup control system. This conspired to push the launch back to Nov. 4.
However, in the early morning hours of Nov. 4 it was obvious that Florida’s turbulent weather would not allow a launch on this day and mission managers scrubbed the launch for at least 24 hours. Weather for Friday shows a 70 percent chance of favorable conditions. If Discovery does launch tomorrow, it will take place at 3:04 p.m. EDT.
Discovery’s final mission, STS-133, will deliver the Leonardo Multipurpose Module (PMM) with its cargo – including the first humanoid robot to be sent into space – Robonaut-2 (R2). Also riding along on this mission is the Express Logistics Carrier-4 and spare parts. Like the other remaining shuttle flights, these new components and supplies are designed to leave the space station better prepared for when the space shuttles are retired next year.
The crew of STS-133 will be comprised of Commander Steve Lindsey, Pilot Eric Boe and Mission Specialists; Alvin Drew, Nicole Stott, Tim Kopra and Michael Barratt. All of these astronauts are space flight veterans.
The name itself conjures up imagines of mini nukes and sophisticated space-age gadgets doesn’t it? Well for some people it does. For others, Plutonium (Pu, atomic number of 94 on the periodic table of elements) spawns images of nuclear reactors, atomic energy and nuclear waste. All of these are true to an extent, but the reality behind this radioactive element is understandably more complex. For starters, plutonium is a silvery white actinide metal that is radioactive, and hence quite dangerous when exposed to living tissue. It is one of the key ingredients in the making of atomic weapons, but is also produced in nuclear reactors as a result of slow fission. There are also several isotopes of the element, but for our purposes, the most important is Plutonium-239, a fissile isotope that is used for both nuclear power and weapons and has a half-life of 24,100 years.
Plutonium-238 was first discovered as an element on Dec.14th1940, and then chemically identified on February 23rd 1941through the deuteron bombardment of Uranium in a cyclotron by Glenn T. Seaborg and his team of scientists, working out of the University of California in Berkley. The team submitted a paper publishing their findings; however, this paper was retracted when it became clear that Plutonium-239 was a fissile material that could be useful in the construction of an atomic weapon. At this time, the US was deep into the development of an atomic bomb (aka. the Manhattan Project) because it was believed that Germany was doing the same. For this reason, publication of Seaborg’s work was delayed until 1946, a year after the Second World War ended and security surrounding atomic research was no longer a concern. Seaborg decided to name the element after Pluto because of the recent discovery of element 93, Neptunium, and felt that element 94 should accordingly be named after the next planet in the Solar System.
Towards the end of WWII, two nuclear reactors were created which would produce the plutonium used in the construction of “Trinity”, “Fat Man” and other atomic weapons. These were the X-10 Graphite Reactor facility in Oak Ridge (which later became the Oak Ridge National Laboratory) and the Hanford B reactor (built in 1943 and 45 respectively). Large stockpiles were subsequently built up by the US and USSR during the Cold War, and have since become the focus of nuclear proliferation treaty concerns. Today, it is estimated that several tonnes of plutonium isotopes exist in our biosphere, the result of atomic testing during the 1950’s and 60’s.
Pluto, we hardly knew ya! Don’t worry, she’s not going anywhere. However, this once happy planet will no longer be listed amongst the “planets” in our solar system. According to International Astronomical Union (IAU), which began meeting in August of 2006, the term Plutoid now applies to Pluto, as well as any other small stellar body that exist beyond the range of Neptune. Arriving at this working definition in 2008, two years after first meeting, the IAU defines the term Plutoids thusly: “Plutoids are celestial bodies in orbit around the Sun at a semimajor axis greater than that of Neptune that have sufficient mass for their self-gravity to overcome rigid body forces so that they assume a hydrostatic equilibrium (near-spherical) shape, and that have not cleared the neighbourhood around their orbit.”
The reason the IAU began meeting in the first place was to iron out some ambiguities that exist in the terminology of astronomy. For example, thought some might find it shocking, astronomers had never actually come up with a definition of “planet”. Originally, a planet meant a “wandering star” – ie. a star that appeared to move from constellation to constellation. This was the definition used by ancient astronomers, and it applied to the sun and moon as well. However, Copernicus’s heliocentric model changed all that; now it was clear that the Earth was a planet itself and moved around the Sun with the rest of them. In addition, more and planets were being discovered beyond Jupiter, such as Uranus and Neptune, and then between Jupiter and Mars. This included Ceres, Pallas, Vesta, and Juno, but astronomers soon realized that these bodies were far too small to fit with the rest of the planets.
Then came Pluto’s discovery. At the time, scientists thought it to be several times larger than it actually was; accordingly they placed it on the list of planets. Eventually, its true size was realized and other bodies similar to Pluto in size and composition were found far beyond Neptune, in what is known as the Kuiper Belt. Pluto was to these stellar objects what Ceres was to large objects in the asteroid belt – that is to say, comparable in size. Astronomers proposed several names for these objects, but matters did not come to a head until Eris was discovered. This dwarf planet was actually larger than Pluto, 2500 km in diameter, making it twenty-seven percent larger than Pluto.
In the end, the IAU could only resolve this matter by removing Pluto from the list of planets and devising a new category for dwarf planets that could no longer be considered true planets. Plutoid was the result, and now applies to the trans-Neptunian objects of Pluto, Haumea, Makemake, and Eris.
