Stellar motions distort the future sky. Map: Bob King, Source: Stellarium
If we could transport Ptolemy, a famous astronomer who lived circa 90 – 168 A.D. in Alexandria, Egypt, he would have noticed the shift in position of Arcturus, Sirius and Aldebaran since his time. Everything else would appear virtually unchanged.
You go out and look at the stars year after year and never see any of them get up and walk away from their constellations. Take a time machine back to the days of Plato and Socrates and only careful viewing would reveal that just three of the sky’s naked eye stars had budged: Arcturus, Sirius and Aldebaran. And then only a little. Their motion was discovered by Edmund Halley in 1718 when he compared the stars’ positions then to their positions noted by the ancient Greek astronomers. In all three cases, the stars had moved “above a half a degree more Southerly at this time than the Antients reckoned them.”
NGC 4414 is a spiral galaxy that resembles our own Milky Way. I’ve drawn in the orbits of several stars. Both disk and halo stars orbit about the center, but halo stars describe long elliptical orbits that take them well beyond the disk. When a star plunges through the disk, if it happens to be relatively nearby as in the case of Arcturus, the star will appear to move relatively quickly across the sky. Both distance and the type of orbit a star has can affect how fast it moves from our perspective. Credit: NASA/ESA with orbits by the author
Stars are incredibly far away. I could throw light years around like I often do here, but the fact is, you can get a real feel for their distance by noting that during your lifetime, none will appear to move individually. The gems of the night and our sun alike revolve around the center of the galaxy. At our solar system’s distance from the center — 26,000 light years or about halfway from center to edge — it takes the sun about 225 million years to make one revolution around the Milky Way.
That’s a LONG time. The other stars we see on a September night take a similar length of time to orbit. Now divide the average lifetime of some 85 years into that number, and you’ll discover that an average star moves something like .00000038% of its orbit around the galactic center every generation. Phew, that ain’t much! No wonder most stars don’t budge in our lifetime.
This graphic, made using SkyMap software created by Chris Marriott, shows the motion of Arcturus over a span of 8,000 years.
Sirius, Aldebaran and Arcturus and several other telescopic stars are close enough that their motion across the sky becomes apparent within the span of recorded history. More powerful telescopes, which expand the scale of the sky, can see a great many stars amble within a human lifetime. Sadly, our eyes alone only work at low power!
Precession of Earth’s axis maintains its usual 23.5 degree tilt, but this causes the axis to describe a circle in the sky like a wobbling top. The photo is an animation that repeats 10 seconds, so hang in there. Credit: Wikimedia Commons
But we needn’t invest billions in building a time machine to zing to the future or past to see how the constellation outlines become distorted by the individual motions of the stars that compose them. We already have one! Just fire up a free sky charting software program like Stellarium and advance the clock. Like most such programs, it defaults to the present, but let’s look ahead. Far ahead.
If we advance 90,000 years into the future, many of the constellations would be unrecognizable. Not only that, but more locally, the precession of Earth’s axis causes the polestar to shift. In 2016, Polaris in the Little Dipper stands at the northernmost point in the sky, but in 90,000 years the brilliant star Vega will occupy the spot. Tugs from the sun and moon on Earth’s equatorial bulge cause its axis to gyrate in a circle over a period of about 26,000 years. Wherever the axis points defines the polestar.
I advanced Stellarium far enough into the future to see how radically the Big Dipper changes shape over time. Notice too that Vega will be the polestar in that distant era. Map: Bob King, Source: Stellarium
Take a look at the Big Dipper. Wow! It’s totally bent out of shape yet still recognizable. The Pointer Stars no longer quite point to Polaris, but with some fudging we might make it work. Vega stands near the pole, and being much closer to us than the rest of Lyra’s stars, has moved considerably farther north, stretching the outline of the constellation as if taffy.
Now let’s head backwards in time 92,000 years to 90,000 B.C. The Dipper then was fairly unrecognizable, with both Vega and Arcturus near the pole. Map: Bob King , Source: Stellarium
Time goes on. We look up at the night sky in the present moment, but so much came before us and much will come after. Constellations were unrecognizable in the past and will be again in the future. In a fascinating discussion with Michael Kauper of the Minnesota Astronomical Society at a recent star party, he described the amount of space in and between galaxies as so enormous that “we’re almost not here” in comparison. I would add that time is so vast we’re likewise almost not present. Make the most of the moment.
Is there an up out there? New research says no. Out there in the universe, one direction is much like another. Credit: NASA; ESA; Z. Levay and R. van der Marel, STScI; T. Hallas; and A. Mellinger
Direction is something we humans are pretty accustomed to. Living in our friendly terrestrial environment, we are used to seeing things in term of up and down, left and right, forwards or backwards. And to us, our frame of reference is fixed and doesn’t change, unless we move or are in the process of moving. But when it comes to cosmology, things get a little more complicated.
For a long time now, cosmologists have held the belief that the universe is homogeneous and isotropic – i.e. fundamentally the same in all directions. In this sense, there is no such thing as “up” or “down” when it comes to space, only points of reference that are entirely relative. And thanks to a new study by researchers from the University College London, that view has been shown to be correct.
For the sake of their study, titled “How isotropic is the Universe?“, the research team used survey data of the Cosmic Microwave Background (CMB) – the thermal radiation left over from the Big Bang. This data was obtained by the ESA’s Planck spacecraft between 2009 and 2013.
The cosmic microwave background radiation, enhanced to show the anomalies. Credit: ESA and the Planck Collaboration
The team then analyzed it using a supercomputer to determine if there were any polarization patterns that would indicate if space has a “preferred direction” of expansion. The purpose of this test was to see if one of the basic assumptions that underlies the most widely-accepted cosmological model is in fact correct.
The first of these assumptions is that the Universe was created by the Big Bang, which is based on the discovery that the Universe is in a state of expansion, and the discovery of the Cosmic Microwave Background. The second assumption is that space is homogenous and istropic, meaning that there are no major differences in the distribution of matter over large scales.
This belief, which is also known as the Cosmological Principle, is based partly on the Copernican Principle (which states that Earth has no special place in the Universe) and Einstein’s Theory of Relativity – which demonstrated that the measurement of inertia in any system is relative to the observer.
This theory has always had its limitations, as matter is clearly not evenly distributed at smaller scales (i.e. star systems, galaxies, galaxy clusters, etc.). However, cosmologists have argued around this by saying that fluctuation on the small scale are due to quantum fluctuations that occurred in the early Universe, and that the large-scale structure is one of homogeneity.
Timeline of the Big Bang and the expansion of the Universe. Credit: NASA
By looking for fluctuations in the oldest light in the Universe, scientists have been attempting to determine if this is in fact correct. In the past thirty years, these kinds of measurements have been performed by multiple missions, such as the Cosmic Background Explorer (COBE) mission, the Wilkinson Microwave Anisotropy Probe (WMAP), and the Planck spacecraft.
For the sake of their study, the UCL research team – led by Daniela Saadeh and Stephen Feeney – looked at things a little differently. Instead of searching for imbalances in the microwave background, they looked for signs that space could have a preferred direction of expansion, and how these might imprint themselves on the CMB.
As Daniela Saadeh – a PhD student at UCL and the lead author on the paper – told Universe Today via email:
“We analyzed the temperature and polarization of the cosmic microwave background (CMB), a relic radiation from the Big Bang, using data from the Planck mission. We compared the real CMB against our predictions for what it would look like in an anisotropic universe. After this search, we concluded that there is no evidence for these patterns and that the assumption that the Universe is isotropic on large scales is a good one.”
Basically, their results showed that there is only a 1 in 121 000 chance that the Universe is anisotropic. In other words, the evidence indicates that the Universe has been expanding in all directions uniformly, thus removing any doubts about their being any actual sense of direction on the large-scale.
A “now and then” all-sky image captured by the Planck spacecraft, simultaneously showing our galaxy and its structures seen as in recent history; and ‘then’ – the red afterglow of the Big Bang seen as it was just 380,000 years later. Credit: ESA
And in a way, this is a bit disappointing, since a Universe that is not homogenous and the same in all directions would lead to a set of solutions to Einstein’s field equations. By themselves, these equations do not impose any symmetries on space time, but the Standard Model (of which they are part) does accept homogeneity as a sort of given.
These solutions are known as the Bianchi models, which were proposed by Italian mathematician Luigi Bianchi in the late 19th century. These algebraic theories, which can be applied to three-dimensional spacetime, are obtained by being less restrictive, and thus allow for a Universe that is anisotropic.
On the other hand, the study performed by Saadeh, Feeney, and their colleagues has shown that one of the main assumptions that our current cosmological models rest on is indeed correct. In so doing, they have also provided a much-needed sense of closer to a long-term debate.
“In the last ten years there has been considerable discussion around whether there were signs of large-scale anisotropy lurking in the CMB,” said Saadeh. “If the Universe were anisotropic, we would need to revise many of our calculations about its history and content. Planck high-quality data came with a golden opportunity to perform this health check on the standard model of cosmology and the good news is that it is safe.”
So the next time you find yourself looking up at the night sky, remember… that’s a luxury you have only while you’re standing on Earth. Out there, its a whole ‘nother ballgame! So enjoy this thing we call “direction” when and where you can.
And be sure to check out this animation produced by the UCL team, which illustrates the Planck mission’s CMB data:
Uranus and Neptune, the Solar System’s ice giant planets. Credit: Wikipedia Commons
“Hitler’s acid” is a colloquial name used to refer to Orthocarbonic acid – a name which was inspired from the fact that the molecule’s appearance resembles a swastika. As chemical compounds go, it is quite exotic, and chemists are still not sure how to create it under laboratory conditions.
But it just so happens that this acid could exist in the interiors of planets like Uranus and Neptune. According to a recent study from a team of Russian chemists, the conditions inside Uranus and Neptune could be ideal for creating exotic molecular and polymeric compounds, and keeping them under stable conditions.
The study was produced by researchers from the Moscow Institute of Physics and Technology (MIPT) and the Skolkovo Institute of Science and Technology (Skoltech). Titled “Novel Stable Compounds in the C-H-O Ternary System at High Pressure”, the paper describes how the high pressure environments inside planets could create compounds that exist nowhere else in the Solar System.
Orthocarbonic acid (also known as Hitler’s acid). Credit: Moscow Institute of Physics and Technology
Professor Artem Oganov – a professor at Skoltech and the head of MIPT’s Computational Materials Discovery Lab – is the study’s lead author. Years back, he and a team of researchers developed the worlds most powerful algorithm for predicting the formation of crystal structures and chemical compounds under extreme conditions.
Known as the Universal Structure Predictor: Evolutionary Xtallography (UPSEX), scientists have since used this algorithm to predict the existence of substances that are considered impossible in classical chemistry, but which could exist where pressures and temperatures are high enough – i.e. the interior of a planet.
With the help of Gabriele Saleh, a postdoc member of MIPT and the co-author of the paper, the two decided to use the algorithm to study how the carbon-hydrogen-oxygen system would behave under high pressure. These elements are plentiful in our Solar System, and are the basis of organic chemistry.
Until now, it has not been clear how these elements behave when subjected to extremes of temperature and pressure. What they found was that under these types of extreme conditions, which are the norm inside gas giants, these elements form some truly exotic compounds.
Diagram of the interior structure of Uranus. Credit: Moscow Institute of Physics and Technology
“The smaller gas giants – Uranus and Neptune – consist largely of carbon, hydrogen and oxygen. We have found that at a pressure of several million atmospheres unexpected compounds should form in their interiors. The cores of these planets may largely consist of these exotic materials.”
Under normal pressure – i.e. what we experience here on Earth (100 kPa) – any carbon, hydrogen or oxygen compounds (with the exception of methane, water and CO²) are unstable. But at pressures in the range 1 to 400 GPa (10,000 to 4 million times Earth normal), they become stable enough to form several new substances.
These include carbonic acid, orthocarbonic acid (Hitler’s acid) and other rare compounds. This was a very unusual find, considering that these chemicals are unstable under normal pressure conditions. In carbonic acid’s case, it can only remain stable when kept at very low temperatures in a vacuum.
Diagram of the interior structure of Neptune. Credit: Moscow Institute of Physics and Technology
At pressures of 314 GPa, they determined that carbonic acid (H²CO³) would react with water to form orthocarbonic acid (H4CO4). This acid is also extremely unstable, and so far, scientists have not yet been able to produce it in a laboratory environment.
This research is of considerable importance when it comes to modelling the interior of planets like Uranus and Neptune. Like all gas giants, the structure and composition of their interiors have remained the subject of speculation due to their inaccessible nature. But it could also have implications in the search for life beyond Earth.
According to Oganov and Saleh, the interiors of many moons that orbit gas giants (like Europa, Ganymede and Enceladus) also experience these types of pressure conditions. Knowing that these kinds of exotic compounds could exist in their interiors is likely to change what scientist’s think is going on under their icy surfaces.
“It was previously thought that the oceans in these satellites are in direct contact with the rocky core and a chemical reaction took place between them,” said Oganov. “Our study shows that the core should be ‘wrapped’ in a layer of crystallized carbonic acid, which means that a reaction between the core and the ocean would be impossible.”
Europa’s cracked, icy surface imaged by NASA’s Galileo spacecraft in 1998. Credit: NASA/JPL-Caltech/SETI
For some time, scientists have understood that at high temperatures and pressures, the properties of matter change pretty drastically. And while here on Earth, atmospheric pressure and temperatures are quite stable (just the way we like them!), the situation in the outer Solar System is much different.
By modelling what can occur under these conditions, and knowing what chemical buildings blocks are involved, we could be able to determine with a fair degree of confidence what the interior’s of inaccessible bodies are like. This will give us something to work with when the day comes (hopefully soon) that we can investigate them directly.
Who knows? In the coming years, a mission to Europa may find that the core-mantle boundary is not a habitable environment after all. Rather than a watery environment kept warm by hydrothermal activity, it might instead by a thick layer of chemical soup.
Then again, we may find that the interaction of these chemicals with geothermal energy could produce organic life that is even more exotic!
View from the Curiosity rover at the foot of Aeolis Mons, before the rover starts to climb the mountain. Credit: NASA
After four years on Mars, the Curiosity rover has made some pretty impressive discoveries. These have ranged from characterizing what Mars’ atmosphere was like billions of years ago to discovering organic molecules and methane there today. But arguably the biggest discovery Curiosity has made has been uncovering evidence of warm, flowing water on Mars’ surface.
Unfortunately, now faced with what could be signs of water directly in its path, NASA is forced to enact strict protocols. These signs take the form of dark streaks that have been observed along the sloping terrain of Aeolis Mons (aka. Mount Sharp), which the rover has been preparing to climb. In order to prevent contamination, the rover must avoid any contact with them, which could mean a serious diversion.
These sorts of dark streaks are known as recurring slope lineae (RSLs) because of their tendency to appear, fade away and reappear seasonally on steep slopes. The first RSLs were reported in 2011 by the Mars Reconnaissance Orbiter in a variety of locations, and are now seen as proof that water still periodically flows on Mars (albiet in the form of salt-water).
Mosaic of the Valles Marineris hemisphere of Mars, as it would appear from orbit. Credit: NASA/JPL-Caltech
Since that time, a total of 452 possible RSLs have been observed, mostly in Mars’s southern mid-latitudes or near the equator (particularly in Mars’ Valles Marineris). They are generally a few meters wide, and appear to lengthen at the warmest times of the year, then fade during the colder times.
These seasonal flows of salt water are believed to have come from ice trapped about a meter below the surface. Ordinarily, such features would present an opportunity to conduct research. But doing so would cause the water source to be contaminated by Earth microbes aboard Curiosity. And right now, Curiosity has bigger fish to fry (so to speak).
During its planned climb, Curiosity was supposed to pass within a few kilometers of an RSL. However, if NASA determines that the risk is too high, the rover will have to alter its course. Unfortunately, that presents a major challenge, since there is currently only one clear route between Curiosity’s current location and its next destination.
But then again, Curiosity may not have to alter its course at all. Or it could find a route that lets it still accomplish its scientific goals, depending on the circumstances. As Ashwin R. Vasavada, the Project Scientist at the Mars Science Laboratory, told Universe Today via email:
“It may depend on the distance between the rover and a potentially sensitive region, for example. Based on that understanding, we’ll determine the right course of action. For example, it may be possible to achieve Curiosity’s science goals while maintaining a safe distance. Another possible outcome is that we determine that there are no Recurring Slope Lineae on Mount Sharp.”
MRO image of Gale Crater illustrating the landing location and trek of the Rover Curiosity. Credit: NASA/JPL, illustration, T.Reyes
For years, NASA scientists have been seeking to obtain samples from different locations around Mount Sharp. By studying the sedimentary deposits in the mountainside, the rover’s science team hopes to see how Mars’ environment changed over the past 3 billion years. As Vasavada explained:
“Curiosity’s science mission has focused on understanding whether the area around 5-km high Mount Sharp ever had conditions suitable for life. We’ve already found evidence for an ancient, 3-billion-year-old habitable environment out on the plains around the mountain, and in the lowest levels of the mountain.”
“The geology indicates that a series of lakes once was present in the basin of the crater, before the mountain took shape. Curiosity will continue climbing lower Mount Sharp to see how long these habitable conditions lasted. Every step higher we go, we encounter rocks that are a bit younger, but still around 3 billion years old.”
In the end, the job of determining the risk falls to NASA’s Planetary Protection Office. In addition to reviewing the current predicament, the issue of pre-mission safety standards is also likely to come up. Prior to its deployment to Mars, the Curiosity rover was only partially sterilized, and it is currently unknown how long Earth microbes could survive in the Martian atmosphere, or how far they could be carried in Mars’ atmosphere.
These dark streaks, called recurring slope lineae (RSL), are on the sloped wall of a crater on Mars. Credit: NASA/JPL-Caltech/Univ. of Arizona
Answering these questions and coming up with new protocols that will address them in advance will come in handy for future missions – particularly the Mars 2020 Rover mission. In the course of its mission, which will include obtaining samples and leaving them behind for possible retrieval by a future crewed mission, the rover is likely to encounter several RSLs.
One of the Mars 2020 rover’s primary tasks will be finding evidence of microbial life, so ensuring that Earth microbes don’t get in the way will be of extreme importance. And with crewed missions on the horizon, knowing how we can prevent contaminating Mars with our own germs (of which there are many) is paramount!
On its currently project path, the Curiosity rover would not get closer than 2 km from the potential RSL (which it is currently 5 km from). And as Vasavada indicated, it is not known at the present time what alternate routes Curiosity could take, or if a diversion in the rover’s path will effect it’s overall mission.
“It’s unclear at this time,” he said. “But I’m optimistic that we can find a solution that protects Mars, allows us to accomplish our mission goals, and even gives us new insight into modern water on Mars, if it is there.”
The Milky Way is like NGC 4594 (pictured), a disc shaped spiral galaxy with around 200 billion stars. The three main features are the central bulge, the disk, and the halo. Credit: ESO
Maybe we take our beloved Milky Way galaxy for granted. As far as humanity is concerned, it’s always been here. But how did it form? What is its history?
Our Milky Way galaxy has three recognized stellar components. They are the central bulge, the disk , and the halo. How these three were formed and how they evolved are prominent, fundamental questions in astronomy. Now, a team of researchers have used the unique property of a certain type of star to help answer these fundamental questions.
The type of star in question is called the blue horizontal-branch star (BHB star), and it produces different colors depending on its age. It’s the only type of star to do that. The researchers, from the University of Notre Dame, used this property of BHB’s to create a detailed chronographic (time) map of the Milky Way’s formation.
This map has confirmed what theories and models have predicted for some time: the Milky Way galaxy formed through mergers and accretions of small haloes of gas and dust. Furthermore, the oldest stars in our galaxy are at the center, and younger stars and galaxies joined the Milky Way over billions of years, drawn in by the galaxy’s growing gravitational pull.
The team who produced this study includes astrophysicist Daniela Carollo, research assistant professor in the Department of Physics at the University of Notre Dame, and Timothy Beers, Notre Dame Chair of Astrophysics. Research assistant professor Vinicius Placco, and other colleagues rounded out the team.
“We haven’t previously known much about the age of the most ancient component of the Milky Way, which is the Halo System,” Carollo said. “But now we have demonstrated conclusively for the first time that ancient stars are in the center of the galaxy and the younger stars are found at longer distances. This is another piece of information that we can use to understand the assembly process of the galaxy, and how galaxies in general formed.”
This dazzling infrared image from NASA’s Spitzer Space Telescope shows hundreds of thousands of stars crowded into the swirling core of our spiral Milky Way galaxy. Credit: NASA/JPL-Caltech
The Sloan Digital Sky Survey (SDSS) played a key role in these findings. The team used data from the SDSS to identify over 130,000 BHB’s. Since these stars literally “show their age”, mapping them throughout the Milky Way produced a chronographic map which clearly shows the oldest stars near the center of the galaxy, and youngest stars further away.
“The colors, when the stars are at that stage of their evolution, are directly related to the amount of time that star has been alive, so we can estimate the age,” Beers said. “Once you have a map, then you can determine which stars came in first and the ages of those portions of the galaxy. We can now actually visualize how our galaxy was built up and inspect the stellar debris from some of the other small galaxies being destroyed by their interaction with ours during its assembly.”
Astronomers infer, from various data-driven approaches, that different structural parts of the galaxy have different ages. They’ve assigned ages to different parts of the galaxy, like the bulge. That makes sense, since everything can’t be the same age. Not in a galaxy that’s this old. But this map makes it even clearer.
As the authors say in their paper, “What has been missing, until only recently, is the ability to assign ages to individual stellar populations, so that the full chemo-dynamical history of the Milky Way can be assessed.”
This new map, with over 130,000 stars as data points, is a pretty important step in understanding the evolution of the Milky Way. It takes something that was based more on models and theory, however sound they were, and reinforces it with more constrained data.
Update: The chronographic map, as well as a .gif, can be viewed here.
Peering through the thick dust clouds of the galactic bulge (center of the galaxy) an international team of astronomers has revealed the unusual mix of stars in the stellar cluster known as Terzan 5. The new results indicate that Terzan 5 is in fact one of the bulge's primordial building blocks, most likely the relic of the very early days of the Milky Way. Credit: NASA/ESA/Hubble/F. Ferraro
Peering through the thick dust clouds of the galactic bulge (center of the galaxy) an international team of astronomers has revealed the unusual mix of stars in the stellar cluster known as Terzan 5. The new results indicate that Terzan 5 is in fact one of the bulge’s primordial building blocks, most likely the relic of the very early days of the Milky Way. Credit: NASA/ESA/Hubble/F. Ferraro
Not many people have heard of the globular star cluster Terzan 5. It’s a big ball of stars resembling spilled sugar like so many other globular clusters. A very few globulars are bright enough to see with the naked eye; Terzan 5 is faint because it lies far away in the direction of the center of Milky Way galaxy inside its central bulge. Here, the stars that formed at the galaxy’s birth are packed together in great numbers. They are the “old ones” of the Milky Way.
Today, a team of astronomers revealed that Terzan 5 is unlike any globular cluster known. Most Milky Way globulars contain stars of just one age, about 11-12 billion years. They formed around the same time as the Milky Way itself, used up all their available gas early to build stars and then spent the remaining billions of years aging. Most orbit the galaxy’s center in a vast halo like moths whirring around a bright light. Oddball Terzan 5 has two populations aged 12 billion and 4.5 billion years old and it’s located inside the galactic bulge.
Globular clusters are distributed in a spherical halo about the star-rich core or bulge at the center of the disk of the Milky Way galaxy. Credit: Science Frontiers Online
The team used the cameras on the Hubble Space Telescope as well as a host of ground-based telescopes to find compelling evidence for the two distinct kinds of stars. Not only do they show a large gap in age, but the differ in the elements they contain. Terzan 5’s dual populations point to a star formation process that wasn’t continuous but dominated by two distinct bursts of star formation.
“This requires the Terzan 5 ancestor to have large amounts of gas for a second generation of stars and to be quite massive. At least 100 million times the mass of the Sun,” explains Davide Massari, co-author of the study.
Its unusual properties make Terzan 5 the ideal candidate for the title of “living fossil” from the early days of the Milky Way. Current theories on galaxy formation assume that vast clumps of gas and stars interacted to form the primordial bulge of the Milky Way, merging and dissolving in the process.
While the properties of Terzan 5 are uncommon for a globular cluster, they’re very similar to the stars found in the galactic bulge. Remnants of those gaseous clumps appear to have stuck around intact since the days of our galaxy’s birth, one of them evolving into the present day Terzan 5. That makes it a relic from the Milky Way’s infant days and one of the earliest galactic building blocks. Later, the cluster, which held onto some of its remaining gas, experienced a second burst of star formation.
This current model of the Milky Way galaxy shows the yellow-hued galactic bulge formed by ancient stars well along in their evolution, in contrast to the bluer, younger stars in the spiral arms. Credit: NASA/JPL-Caltech/R. Hurt (SSC/Caltech)
“Some characteristics of Terzan 5 resemble those detected in the giant clumps we see in star-forming galaxies at high-redshift (galaxies just beginning to form in the remote universe in the far distant past), suggesting that similar assembling processes occurred in the local and in the distant universe at the epoch of galaxy formation,” said Dr. Francesco Ferraro from the University of Bologna, Italy, who headed up the team.
The Milky Way on a late September night offers an opportunity to contemplate the grand form of the galaxy. Credit: Bob King
Terzan 5’s chandelier-like presence is helping astronomers understand how our galaxy was assembled. Reconstructing the past is one of the key occupations of astronomy. The present is continually departing with every passing moment. Soon enough, every piece of information slips into the past tense. In the near-past, which records humanity’s comings and goings, details are often forgotten or lost. The deep past is even worse. With no one around and only scattered clues, astronomers continually look for fragmental remains that when woven into the fabric of a theory, reveal patterns and processes before we came to be.
SpaceX and NASA find themselves at odds over the company's fueling policy. Credit: SpaceX
SpaceX experienced a rather serious setback last week as a Falcon 9 rocket exploded on the launch pad while preparing for a static fire test. The launch was meant to deploy one of Spacecom latest communications satellites (AMOS-6), which was also destroyed in the accident. Mercifully, no one was hurt, and an investigation was quickly mounted to determine the root cause.
However, in the aftermath of the explosion, it appears that SpaceX could be facing legal battles, as Spacecom indicated that it is seeking compensation for the loss of their satellite. According to a recent press released by the Israel-based telecommunications company, this will either take the form of $50 million, or a free flight aboard another SpaceX launch.
As the sixth satellite to be launched by the telecommunications company, the AMOS-6 satellite was intended to provide phone, video and internet services for the Middle East, Europe, and locations across sub-Sahara Africa. As such, it’s destruction was certainly a loss for the company.
A Falcon 9 test firing its nine first-stage Merlin engines at Cape Canaveral Air Force Station in Feb of 2015. Credit: NASA/Frankie Martin
But as they stated in their press release – which was released on Monday, Sept. 5th – their plan is “to recover funds invested in the project” and to replace the satellite as soon as possible. As David Pollack, Spacecom CEO and president, was quoted as saying:
“Spacecom has crafted a plan of action which represents the foundation upon which we shall recover from AMOS-6’s loss. Our program includes, among other measures, exploring the possibility of procuring and launching a replacement satellite. Working quickly and efficiently, management is engaging with current and potential partner. Spacecom will serve all of its current and future financial commitments.”
In addition to covering their losses, these moves are clearly intended to ensure that the company can still move ahead with its planned merger. Prior to the launch, Spacecom was engaged in talks with the Beijing Xinwei Group – a Chinese telecommunications company – about being acquired for $285 million. One of the conditions of this deal was the successful launch of the AMOS-6 and completion of in orbit testing.
As Pollack told the Financial Times, his company is still in the process of negotiating the merger, but the price may come down as a result of the loss. “We are speaking to them;” he said, “we are trying to adapt it to the new situation. It definitely might go ahead… everybody is trying to keep the deal”.
The damaged gantry at the SpaceX launch pad after the explosion. Credit: Karla Thompson
Spacecom has also suggested that the firm might pursue an additional $205 million in compensation from Israel Aerospace Industries, which manufactured the satellite. Not surprising, since the price of their stock had dropped by over a third since the accident took place.
Since the accident took place, SpaceX has been keeping the public updated on the results of their investigation. On Friday, Sept 2nd, they released the latest finds, which included where the problems began:
“The anomaly on the pad resulted in the loss of the vehicle. This was part of a standard pre-launch static fire to demonstrate the health of the vehicle prior to an eventual launch. At the time of the loss, the launch vehicle was vertical and in the process of being fueled for the test. At this time, the data indicates the anomaly originated around the upper stage liquid oxygen tank. Per standard operating procedure, all personnel were clear of the pad. There were no injuries.”
No indications have been given yet as to what could have caused the tanks to explode, but the company is still processing the data and posting updates on a regular basis. In any event, the recent accident appears to have been a minor setback for the private aerospace giant, which will be pushing ahead with a full year of launch contracts.
This will likely include the first launch of the Falcon Heavy, which is expected to take place before 2016 is out.
Artist's concept of an interstellar craft. Credit and Copyright: Mark Rademaker
The “impossible” EM Drive (also known as the RF resonant cavity thruster) is one of those concepts that just won’t seem to die. Despite being subjected to a flurry of doubts and skepticism from the beginning that claim its too good to be true and violates the laws of physics, the EM Drive seems to be clearing all the hurdles placed in its way.
For years now, one of the most lingering comments has been that the technology has not passed peer-review. This has been the common retort whenever news of successful tests have been made. But, according to new rumors, the EM Drive recently did just that, as the paper that NASA submitted detailing the successful tests of their prototype has apparently passed the peer review process.
A model of the EmDrive. EM Drive prototype by NASA/Eagleworks. Credit: NASA Spaceflight Forum
Now before anyone gets too excited, a quick reality check is necessary. At this time, everything said by Dr. Rodal has yet to be confirmed, and the comment has since been deleted. However, in his comment, Rodal did specify the paper would be titled “Measurement of Impulsive Thrust from a Closed Radio Frequency Cavity in Vacuum”.
He also named the papers authors, which includes Harold White – the Advanced Propulsion Team Lead for the Johnson Space Center’s Advanced Propulsion Physics Laboratory (aka. Eagleworks). Paul March was also named, another member of Eagleworks and someone who is associated with past tests.
On top of all that, the IB Times story indicated that he also posted information that appeared to be taken from the paper’s abstract:
“Thrust data in mode shape TM212 at less than 8106 Torr environment, from forward, reverse and null tests suggests that the system is consistently performing with a thrust to power ratio of 1.2 +/- 0.1 mN/Kw ()”.
Artist Mark Rademaker’s concept for the IXS Enterprise, which relies on the Aclubierre Drive – something NASA’s Eagleworks is also investigating. Credit: Mark Rademaker/flickr.com
But even if the rumor is true, there are other things that need to be taken into account. For instance, the peer-review process usually means that an independent panel of experts reviewed the work and determined that it is sufficient to merit further consideration. It does not mean the conclusions reached are correct, or that they won’t be subject to contradiction by follow-up investigations.
However, we may not have to wait long before the next test to happen. Guido Fetta is the CEO of Cannae Inc., the inventor of the Cannae Drive (which is based on Shawyer’s design). As he announced on August 17th of this year, the Cannae engine would be launched into space on board a 6U CubeSat in order to conduct tests in orbit.
As Fetta stated on their website, Cannae has formed a new company (Theseus Space Inc.) to commercialize their thruster technology, and will use this deployment to see if the Cannae drive can generate thrust in a vacuum:
“Theseus is going to be launching a demo cubesat which will use Cannae thruster technology to maintain an orbit below a 150 mile altitude. This cubesat will maintain its extreme LEO altitude for a minimum duration of 6 months. The primary mission objective is to demonstrate our thruster technology on orbit. Secondary objectives for this mission include orbital altitude and inclination changes performed by the Cannae-thruster technology.”
If feasible, a mission using the EM Drive could travel from Earth to Pluto in just 18 months, compared to the 9.5 years taken by the New Horizons mission. Credit: NASA / Johns Hopkins University Applied Physics Laboratory / Southwest Research Institute
By remaining in orbit for six months, the company will have ample time to see if the satellite is experiencing thrust without the need for propellant. While no launch date has been selected yet, it is clear that Fetta wants to move forward with the launch as soon as possible.
And as David Hambling of Popular Mechanics recently wrote, Fetta is not alone in wanting to get orbital tests underway. A team of engineers in China is also hoping to test their design of the EM Drive in space, and Shawyer himself wants to complete this phase before long. One can only hope their drives all prove equal to the enterprise!
While this could be an important milestone for the EM Drive, it still has a long way to go before NASA and other space agencies consider using them. So we’re still a long away from spacecraft that can send a crewed mission to Mars in 70 days (or one to Pluto in just 18 months).
The March 2016 penumbral lunar eclipse seen from Calliope, Australia. Image credit and copyright: Teale Britstra.
Hey, how ’bout that annular eclipse last week? Some great images flooded in to Universe Today, as the final solar eclipse for 2016 graced the African continent. This not only marked the start of the second and final eclipse season for 2016, but it also set us up for the final eclipse of the year next week.
The path of next week’s penumbral eclipse through the Earth’s shadow. Adapted from NASA/GSFC/F. Espenak.
We’re talking about the penumbral lunar eclipse coming up next week on September 16th, 2016. this sort of eclipse occurs when the Moon just misses the dark inner core (umbra) of the Earth’s shadow, and instead, drifts through its relatively bright outer cone, known as the penumbra. Though not the grandest show as eclipses go, astute observers should notice a subtle light tea-colored shading of the Full Moon, and perhaps the ragged dark edge of the umbra on the northwestern limb of the Moon as it brushes by around mid-eclipse.
The visibility map for next week’s eclipse. Image credit: NASA/GSFC/Fred Espenak.
The entirety of the eclipse will be visible from the region surrounding the Indian Ocean on the evening of Friday, September 6th. Viewers in Australia, New Zealand and Japan will see the eclipse transpire at moonset, and the eclipse will get underway at moonrise for observers in western Africa and Europe.
The eclipse runs from first contact at 16:55 Universal Time (UT) to 20:54 UT when the Moon quits the Earth’s shadow almost four hours later. Mid-eclipse occurs at 18:55 UT, with the Moon 91% immersed in the Earth’s outer shadow.
Tales of the Saros
This particular eclipse is member 9 of the 71 lunar eclipses in saros series 147. This saros began on July 2nd 1890 and runs through to the final eclipse in the cycle on May 1st 2990. It will produce its very first partial eclipse next time around on September 28th 2034, and its first total lunar eclipse on June 6th, 2449.
Why penumbrals? Aren’t they the ultimate non-event when it comes to eclipses? Like with much of observational astronomy, a penumbral lunar eclipse pushes our skills as a visual athlete to the limit. Check out the waxing gibbous Moon the night before the eclipse, then the Moon the night of the event. If you didn’t know any better, could you tell the difference from one night to the next? Often, the camera can see what the eye can’t. Photographing the Moon before, during and after a penumbral eclipse will often bring out the subtle shading on post-comparison. You’ll want to photograph the Moon when its high in the sky and free of atmospheric distortion low to the horizon, which tends to discolor the Moon. Such a high-flying Moon during mid-eclipse favors the Indian Subcontinent this time around. We’ve yet to see a good convincing time-lapse documenting a penumbral eclipse, though such a feat is certainly possible.
See anything… shady going on? Here’s the penumbral lunar eclipse from this past March. Image credit and copyright: Neeraj Ladia
When is an eclipse… not an eclipse? By some accounts, the Moon underwent a very shallow penumbral one cycle ago on August 18th, 2016, though the brush past the shadow was so slight that many lists, including the NASA’s GSFC eclipse page omitted it. Three eclipses (a lunar partial and a penumbral, or two penumbrals and one solar) can occur in one eclipse season, if the nodes of the Moon’s orbit where it intersects the ecliptic fall just right. This last occurred in 2013, and will happen again in 2020.
And when there’s a lunar eclipse, there’s also a Full Moon. The September Full Moon is the Harvest Moon, providing a few extra hours of illumination to get the crops in. This year, the Harvest Moon falls just six days from the equinox on September 22nd, marking the start of astronomical Fall in the northern hemisphere and Spring in the southern. The relative ecliptic angle also ensures that moonrise only slides back by a slight amount each evening for observers in mid-northern latitudes around the Harvest Moon.
Can’t wait til the next eclipse? Well, 2017 has four of ’em: an annular on February 26th favoring South America, two lunars (another penumbral on February 11th and a partial on August 7th) and oh yeah, there’s a total solar eclipse crossing the United States on August 21st. And the next total lunar eclipse? The dry spell is broken on January 31st, 2018, when a total lunar eclipse favoring the Pacific Rim occurs. Yeah, we got spoiled with four back-to-back lunar eclipses during the Blood Moon tetrad of 2014-2015…
The planet Venus, as imaged by the Magellan 10 mission. The planet's inhospitable surface makes exploration extremely difficult. Credit: NASA/JPL
Welcome back to our series on Settling the Solar System! Today, we take a look at Earth’s “sister planet”, the hellish, yet strangely similar planet Venus. Enjoy!
Since humans first began looking up at the skies, they have been aware of Venus. In ancient times, it was known as both the “Morning Star” and the “Evening Star”, due to its bright appearance in the sky at sunrise and sunset. Eventually, astronomers realized that it was in fact a planet, and that like Earth, it too orbited the Sun. And thanks to the Space Age and numerous missions to the planet, we have learned exactly what kind of environment Venus has.
With an atmosphere so dense that it makes regular surface imaging impossible, heat so intense it can melt lead, and sulfuric acid rain, there seems little reason to go there. But as we’ve learned in recent years, Venus was once a very different place, complete with oceans and continents. And with the right technology, colonies could be built above the clouds, where they would be safe.
So what would it take to colonize Venus? As with other proposals for colonizing the Solar System, it all comes down to having the right kinds of methods and technologies, and how much are we willing to spend.
At a closest average distance of 41 million km (25,476,219 mi), Venus is the closest planet to Earth. Credit: NASA/JPL/Magellan
Examples in Fiction:
Since the early 20th century, the idea of colonizing Venus has been explored in science fiction, mainly in the form of terraforming it. The earliest known example is Olaf Stapleton’sLast And First Men(1930), two chapters of which are dedicated to describing how humanity’s descendants terraform Venus after Earth becomes uninhabitable; and in the process, commit genocide against the native aquatic life.
By the 1950s and 60s, terraforming began to appear in many works of science fiction. Poul Anderson also wrote extensively about terraforming in the 1950s. In his 1954 novel, The Big Rain, Venus is altered through planetary engineering techniques over a very long period of time. The book was so influential that the term term “Big Rain” has since come to be synonymous with the terraforming of Venus.
In 1991, author G. David Nordley suggested in his short story (“The Snows of Venus”) that Venus might be spun-up to a day-length of 30 Earth days by exporting its atmosphere of Venus via mass drivers. Author Kim Stanley Robinson became famous for his realistic depiction of terraforming in the Mars Trilogy – which included Red Mars, Green Mars and Blue Mars.
In 2012, he followed this series up with the release of 2312, a science fiction novel that dealt with the colonization of the entire Solar System – which includes Venus. The novel also explored the many ways in which Venus could be terraformed, ranging from global cooling to carbon sequestration, all of which were based on scholarly studies and proposals.
Artist’s conception of a terraformed Venus, showing a surface largely covered in oceans. Credit: Wikipedia Commons/Ittiz
Proposed Methods:
All told, most proposed methods for colonizing Venus emphasize ecological engineering (aka. terraforming) to make the planet habitable. However, there have also been suggestions as to how human beings could live on Venus without altering the environment substantially.
For instance, according to Inner Solar System: Prospective Energy and Material Resources, by Viorel Badescu, and Kris Zacny (eds), Soviet scientists have suggested that humans could colonize Venus’ atmosphere rather than attempting to live on its hostile surface since the 1970s.
More recently, NASA scientist Geoffrey A. Landis wrote a paper titled “Colonization of Venus“, in which he proposed that cities could be built above Venus’ clouds. At an altitude of 50 km above the surface, he claimed, such cities would be safe from the harsh Venusian environment:
“[T]he atmosphere of Venus is the most earthlike environment (other than Earth itself) in the solar system. It is proposed here that in the near term, human exploration of Venus could take place from aerostat vehicles in the atmosphere, and that in the long term, permanent settlements could be made in the form of cities designed to float at about fifty kilometer altitude in the atmosphere of Venus.”
Artist’s concept of a Venus cloud city — a possible future outcome of the High Altitude Venus Operational Concept (HAVOC) plan. Credit: Advanced Concepts Lab/NASA Langley Research Center
At an altitude of 50 km above the surface, the environment has a pressure of approximately 100,000 Pa, which is slightly less than Earth’s at sea level (101,325 Pa). Temperatures in this regions also range from 0 to 50 °C (273 to 323 K; 32 to 122 °F), and protection against cosmic radiation would be provided by the atmosphere above, with a shielding mass equivalent to Earth’s.
The Venusian habitats, according to Landis’ proposal, would initially consists of aerostats filled with breathable air (a 21:79 oxygen-nitrogen mix). This is based on the concept that air would be a lifting gas in the dense carbon dioxide atmosphere, possessing over 60% of the lifting power that helium has on Earth.
These would provide initial living spaces for colonists, and could act as terraformers, gradually converting Venus’ atmosphere into something livable so the colonists could migrate to the surface. One way to do this would be to use these very cities as solar shades, since their presence in the clouds would prevent solar radiation from reaching the surface.
This would work particularly well if the floating cities were made of low-albedo materials. Alternately, reflective balloons and/or reflecting sheets of carbon nanotubes or graphene could be deployed from these. This offers the advance of in-situ resource allocation, since atmospheric reflectors could be built using locally-sourced carbon.
In addition, these colonies could serve as platforms where chemical elements were introduced into the atmosphere in large amounts. This could take the form of calcium and magnesium dust (which would sequester carbon in the form of calcium and magnesium carbonates), or a hydrogen aerosol (producing graphite and water, the latter of which would fall to the surface and cover roughly 80% of the surface in oceans).
NASA has begun exploring the possibility of mounting crewed missions to Venus as part of their High Altitude Venus Operational Concept (HAVOC), which was proposed in 2015. As outlined by Dale Arney and Chris Jones from NASA’s Langley Research Center, this mission concept calls for all crewed portions of the missions to be conducted from lighter than air craft or from orbit.
Potential Benefits:
The benefits of colonizing Venus are many. For starters, Venus it the closest planet to Earth, which means it would take less time and money and send missions there, compared to other planets in the Solar System. For example, the Venus Express probe took just over five months to travel from Earth to Venus, whereas the Mars Express probe took nearly six months to get from Earth to Mars.
In addition, launch windows to Venus occur more often, every 584 days when Earth and Venus experience an inferior conjunction. This is compared to the 780 days it takes for Earth and Mars to achieve opposition (i.e. the point in their orbits when they make their closest approach).
Compared to a mission to Mars, a mission to Venus’ atmosphere would also subject astronauts to less in the way of harmful radiation. This is due in part to Venus’ greater proximity, but also from Venus’ induced magnetosphere – which comes from the interaction of its thick atmosphere with solar wind.
Also, for floating settlements established in Venus’ atmosphere, there would be less risk of explosive decompression, since there would not be a significant pressure difference between the inside and outside of the habitats. As such, punctures would pose a lesser risk, and repairs would be easier to mount.
In addition, humans would not require pressurized suits to venture outside, as they would on Mars or other planets. Though they would still need oxygen tanks and protection against the acid rain when working outside their habitats, work crews would find the environment far more hospitable.
Venus is also close in size and mass to the Earth, resulting in a surface gravity that would be much easier to adapt to (0.904 g). Compared to gravity on the Moon, Mercury or Mars (0.165 and 0.38 g), this would likely mean that the health effects associated with weightlessness or microgravity would be negligible.
In addition, a settlement there would have access to abundant materials with which to grow food and manufacture materials. Since Venus’ atmosphere is made mostly out of carbon dioxide, nitrogen and sulfur dioxide, these could be sequestered to create fertilizers and other chemical compounds.
CO² could also be chemically separated to create oxygen gas, and the resulting carbon could be used to manufacture graphene, carbon nanotubes and other super-materials. In addition to being used for possible solar shields, they could also be exported off-world as part of the local economy.
Challenges:
Naturally, colonizing a planet like Venus also comes with its share of difficulties. For instance, while floating colonies would be removed from the extreme heat and pressure of the surface, there would still be the hazard posed by sulfuric acid rain. So addition to the need for protective shielding in the colony, work crews and airships would also need protection.
Second, water is virtually non-existent on Venus, and the composition of the atmosphere would not allow for synthetic production. As a result, water would have to be transported to Venus until it be produced onsite (i.e. bringing in hydrogen gas to create water form the atmosphere), and extremely strict recycling protocols would need to be instituted.
Solar shades placed in orbit of Venus are a possible means of terraforming the planet. Credit: IEEE Spectrum/John MacNeill
And of course, there is the matter of the cost involved. Even with launch windows occurring more often, and a shorter transit time of about five months, it would still require a very heavy investment to transport all the necessary materials – not to mention the robot workers needed to assemble them – to build even a single floating colony in Venus’ atmosphere.
Still, if we find ourselves in a position to do so, Venus could very become the home of “Cloud Cities”, where carbon dioxide gas is processed and turned into super-materials for export. And these cities could serve as a base for slowly introducing “The Big Rain” to Venus, eventually turning into the kind of world that could truly live up to the name “Earth’s sister planet”.
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