Space and astronomy news
Is there life out there in the Universe? That is a question that has plagued humanity long before we knew just how vast the Universe was – i.e. before the advent of modern astronomy. Within the 20th century – thanks to the development of modern telescopes, radio astronomy, and space observatories – multiple efforts have been made in the hopes of finding extraterrestrial intelligence (ETI).
Continue reading “What is the Drake Equation?”
If you’ve read enough of our articles, you know I’ve got an uneasy alliance with the Sun. Sure, it provides the energy we need for all life on Earth. But, it’s a great big ongoing thermonuclear reaction, and it’s right there! As soon as we get fusion, Sun, in like, 30 years or so, I tell you, we’ll be the ones laughing.
But to be honest, we still have so many questions about the Sun. For starters, we don’t fully understand the solar wind blasting out of the Sun. This constant wind of charged particles is constantly blowing out into space, but sometimes it’s stronger, and sometimes it’s weaker.
What are the factors that contribute to the solar wind? And as you know, these charged particles are not healthy for the human body, or for our precious electronics. In fact, the Sun occasionally releases enormous blasts that can damage our satellites and electrical grids.
How can we predict the intensity so that we can be better prepared for dangerous solar storms? Especially the Carrington-class events that might take down huge portions of our modern society.
Perhaps the biggest mystery with the Sun is the temperature of its corona. The surface of the Sun is hot, like 5,500 degrees Celsius. But if you rise up into the atmosphere of the Sun, into its corona, the temperature jumps beyond a million degrees.
The list of mysteries is long. And to start understanding what’s going on, we’ll need to get much much closer to the Sun.
Good news, NASA has a new mission in the works to do just that.
The mission is called the Parker Solar Probe. Actually, last week, it was called the Solar Probe Plus, but then NASA renamed it, and that reminded me to do a video on it.
It’s pretty normal for NASA to rename their spacecraft, usually after a dead astronomer/space scientist, like Kepler, Chandra, etc. This time, though, they renamed it for a legendary solar astronomer Eugene Parker, who developed much of our modern thinking on the Sun’s solar wind. Parker just turned 90 and this is the first time NASA has named it after someone living.
Anyway, back to the spacecraft.
The mission is due to launch in early August 2018 on a Delta IV Heavy, so we’re still more than a year away at this point. When it does, it’ll carry the spacecraft on a very unusual trajectory through the inner Solar System.
The problem is that the Sun is actually a very difficult place to reach. In fact, it’s the hardest place to get to in the entire Solar System.
Remember that the Earth is traveling around the Sun at a velocity of 30 km/s. That’s almost three times the velocity it takes to get into orbit. That’s a lot of velocity.
In order to be able to get anywhere near the Sun, the probe needs to shed velocity. And in order to do this, it’s going to use gravitational slingshots with Venus. We’ve talked about gravitational slingshots in the past, and how you can use them to speed up a spacecraft, but you can actually do the reverse.
The Parker Solar Probe will fall down into Venus’ gravity well, and give orbital velocity to Venus. This will put it on a new trajectory which takes it closer to the Sun. It’ll do a total of 7 flybys in 7 years, each of which will tweak its trajectory and shed some of that orbital momentum.
You know, trying to explain orbital maneuvering is tough. I highly recommend that you try out Kerbal Space Program. I’ve learned more about orbital mechanics by playing that game for a few months than I have in almost 2 decades of space journalism. Go ahead, try to get to the Sun, I challenge you.
Anyway, with each Venus flyby, the Parker Solar Probe will get closer and closer to the Sun, well within the orbit of Mercury. Far closer than any spacecraft has ever gotten to the Sun. At its closest point, it’ll only be 5.9 million kilometers from the Sun. Just for comparison, the Earth orbits at an average distance of about 150 million kilometers. That’s close.
And over the course of its entire mission, the spacecraft is expected to make a total of 24 complete orbits of the Sun, analyzing that plasma ball from every angle.
The orbit is also highly elliptical, which means that it’s going really really fast at its closest point. Almost 725,000 km/h.
In order to withstand the intense temperatures of being this close to the Sun, NASA has engineered the Parker Solar Probe to shed heat. It’s equipped with an 11.5 cm-thick shield made of carbon-composite. For that short time it spends really close to the Sun, the spacecraft will keep the shield up, blocking that heat from reaching the rest of its instruments.
And it’s going to get hot. We’re talking about more than 1,300 degrees Celsius, which is about 475 times as much energy as a spacecraft receives here on Earth. In the outer Solar System, the problem is that there just isn’t enough energy to power solar panels. But where Parker is going, there’s just too much energy.
Now we’ve talked about the engineering difficulties of getting a spacecraft this close to the Sun, let’s talk about the science.
The biggest question astronomers are looking to solve is, how does the corona get so hot. The surface is 5,500 Celsius. As you get farther away from the Sun, you’d expect the temperature to go down. And it certainly does once you get as far as the orbit of the Earth.
But the Sun’s corona, or its outer atmosphere, extends millions of kilometers into space. You can see it during a solar eclipse as this faint glow around the Sun. Instead of dropping, the temperature rises to more than a million degrees.
What could be causing this? There are a couple of ideas. Plasma waves pushed off the Sun could bunch up and release their heat into the corona. You could also get the crisscrossing of magnetic field lines that create mini-flares within the corona, heating it up.
The second great mystery is the solar wind, the stream of charged protons and electrons coming from the Sun. Instead of a constant blowing wind, it can go faster or slower. And when the speed changes, the contents of the wind change too.
There’s the slow wind, that goes a mere 1.1 million km/h and seems to emanate from the Sun’s equatorial regions. And then the fast wind, which seems to be coming out of coronal holes, cooler parts in the Sun’s corona, and can be going at 2.7 million km/h.
Why does the solar wind speed change? Why does its consistency change?
The Parker Solar Probe is equipped with four major instruments, each of which will gather data from the Sun and its environment.
The FIELDS experiment will measure the electric and magnetic fields and waves around the Sun. We know that much of the Sun’s behavior is driven by the complex interaction between charged plasma in the Sun. In fact, many physicists agree that magnetohydrodynamics is easily one of the most complicated fields you can get into.
Integrated Science Investigation of the Sun, or ISOIS (which I suspect needs a renaming) will measure the charged particles streaming off the Sun, during regular solar activity and during dangerous solar storms. Can we get any warning before these events occur, giving astronauts more time to protect themselves?
Wide-field Imager for Solar PRobe or WISPR is its telescope and camera. It’s going to be taking close up, high resolution images of the Sun and its corona that will blow our collective minds… I hope. I mean, if it’s just a bunch of interesting data and no pretty pictures, it’s going to be hard to make cool videos showcasing the results of the mission. You hear me NASA, we want pictures and videos. And science, sure.
And then the Solar Wind Electrons Alphas and Protons Investigation, or SWEAP, will measure type, velocity, temperature and density of particles around the Sun, to help us understand the environment around it.
One interesting side note, the spacecraft will be carrying a tiny chip on board with photos of Eugene Parker and a copy of his original 1958 paper explaining the Sun’s solar wind.
I know we’re still more than a year away from liftoff, and several years away before the science data starts pouring in. But you’ll be hearing more and more about this mission shortly, and I’m pretty excited about what it’s going to accomplish. So stay tuned, and once the science comes in, I’m sure you’ll hear plenty more about it.
On August 15th, 1977, astronomers using the Big Ear radio telescope at Ohio State University detected a 72-second radio signal coming from space. This powerful signal, which quickly earned the nickname the “Wow! signal”, appeared to be coming from the direction of the Sagittarius Constellation, and some went so far as to suggest that it might be extra-terrestrial in origin.
Since then, the Wow! signal has been an ongoing source of controversy among SETI researchers and astronomers. While some have maintained that it is evidence of extra-terrestrial intelligence (ETI), others have sought to find a natural explanation for it. And thanks a team of researchers from the Center of Planetary Science (CPS), a natural explanation may finally have been found.
In the past, possible explanations have ranged from asteroids and exoplanets to stars and even signals from Earth – but these have all been ruled out. And then in 2016, the Center for Planetary Science – a Florida-based non-profit scientific and astronomical organization – proposed a hypothesis arguing that a comet and/or its hydrogen cloud could be the cause.
This was based on the fact that the Wow! signal was transmitting at a frequency of 1,420 MHz, which happens to be the same frequency as hydrogen. This explanation was also appealing because the movement of the comet served as a possible explanation for why the signal has not been detected since. To validate this hypothesis, the CPS team reportedly conducted 200 observations using a 10-meter radio telescope.
This telescope, they claim, was equipped with a spectrometer and a custom feed horn designed to collect a radio signal centered at 1420.25 MHz. Between Nov. 27th, 2016, and Feb. 24th, 2017, they monitored the area of space where the Wow! signal was detected, and found that a pair of Solar comets (which had not been discovered in 1977) happened to conform to their observations, and could therefore have been the source.
Spectra obtained from these comets – P/2008 Y2(Gibbs) and 266/P Christensen – indicated that they were emitting a radio frequency that was consistent with the Wow! signal. As Antonio Paris (a professor at the CPS), described in a recent paper that appeared in the Journal of the Washington Academy of Sciences:
“The investigation discovered that comet 266/P Christensen emitted a radio signal at 1420.25 MHz. All radio emissions detected were within 1° (60 arcminutes) of the known celestial coordinates of the comet as it transited the neighborhood of the ‘Wow!’ Signal. During observations of the comet, a series of experiments determined that known celestial sources at 1420 MHz (i.e., pulsars and/or active galactic nuclei) were not within 15° of comet 266/P Christensen.”
The team also examined three other comets to see if they emitted similar radio signals. These comets – P/2013 EW90 (Tenagra), P/2016 J1-A (PANSTARRS), and 237P/LINEAR – were selected randomly from the JPL Small Bodies database, and were confirmed to emit a radio signal at 1420 MHz. Therefore, the results of this investigation conclude that the 1977 “Wow!” Signal was a natural phenomenon from a Solar System body.
However, not everyone is convinced. In response to the paper, Yvette Cendes – a PhD student with the Dunlap Institute at the University of Toronto – wrote a lengthy response on reddit as to why it fails to properly address the Wow! signal. For starters, she cites how the research team measured the signal strength in terms of decibels:
“I have never, ever, EVER used dB in a paper, nor have I ever read a paper in radio astronomy that measured signal strength in dB (except perhaps in the context of an instrumentation paper describing the systems of a radio telescope, i.e. not science but engineering.) We use a different unit in astronomy for flux density, the Jansky (Jy), where 1 Jy= ?230 dBm/(m2·Hz). (dB is a log scale, and Janskys are not.)”
Another point of criticism is the lack of detail in the paper, which would make reproducing the results very difficult – a central requirement where scientific research is concerned. Specifically, they do not indicate where the 10-meter radio telescope they used came from – i.e. which observatory of facility it belonged to, or even if it belonged to one at all – and are rather vague about its technical specification.
Last, but not least, there is the matter of the environment in which the observations took place, which are not specified. This is also very important for radio astronomy, as it raised the issue of interference. As Cendes put it:
“This might sound pedantic, but this is insanely important in radio astronomy, where most signals we ever search for are a tiny fraction of the man-made ones, which can be millions of times brighter than an astronomical signal. (A cell phone on the moon would be one of the brighter radio astronomy sources in the sky, to give you an idea!) Radio Frequency Interference (RFI) is super important for the field, so much that people can spend their careers on it (I’ve written a chapter on my thesis on this myself), and the “radio environment” of an observatory can be worth a paper in itself.”
Beyond these apparent incongruities, Cendes also states that the hypothesis for the experiment was flawed. Essentially, the Big Ear searched for the same signal for a period of 22 years, but found nothing. If the comet hypothesis held true, there should be an explanation as to why no trace of the signal was found until this time. Alas, one is lacking, as far as this most recent study is concerned.
“And now you likely have an idea on why one-off events are so hard to prove in science,” she claims. “But then, this is really the major reason the Wow! signal is unsolved to this day- without a plausible explanation, [without] additional data, we just will never know.”
Though it may be hard to accept, it is entirely possible that we may never know what the Wow! signal truly was – whether it was a one-off event, a naturally-occurring phenomena, or something else entirely. And if the comet hypothesis should prove to be unverifiable, then that is certainly good news for the SETI enthusiasts!
While the elimination of natural explanations doesn’t prove that things like Wow! signal are proof of alien civilizations, it at least indicates that this possibility cannot be ruled out just yet. And for those hopeful that evidence of intelligent life will be someday found, that’s really the best we can hope for… for now!
Further Reading: Journal of the Washington Academy of Sciences, Astronomer Here!
When it comes time to explore Mars with crewed missions, a number of challenges will present themselves. Aside from the dangers that come with long-duration missions to distant bodies, there’s also the issue of the hazards presented by the Martian landscape. It’s desiccated and cold, it gets exposed to a lot of radiation, and its pretty rugged to boot! So astronauts will need a way to get around and conduct research in comfort and safety.
To meet this challenge, NASA created a vehicle that looks like it could give the Batmobile a run for its money! It’s known as the Mars Rover Concept Vehicle (MRCV) a working vehicle/mobile laboratory that was unveiled last week (June 5th, 2017) to kick off NASA’s Summer of Mars. Those who attended the event at the Kennedy Space Center Visitor Complex were fortunate to be the first to see the new Mars explorer vehicle up close.
Running from June 5th to September 4th, 2017, the Summer of Mars showcases the planning, components and technologies that will make NASA’s proposed “Journey to Mars” happen by the 2030s. According to Rebecca Shireman, the assistant manager of public relations for the Kennedy Visitor Complex, the program will also provide a survey of NASA’s studies of the Red Planet.
As she said in a NASA press statement:
“It’s an all-encompassing effort to review the history of our efforts to explore Mars and look ahead to what is being planned. We hope this will encourage young people to want to learn more about being a part of the effort to go to Mars.”
Astronaut Scott Kelly was also on hand to help unveil the vehicle, which could prove to be the prototype for future off-world transportation. Kelly also took the occasion to tell audiences about the year he spent aboard the ISS – which lasted from March 27th, 2015, to Feb. 3rd, 2016 – and the vital research he took part in. But in the end, the MRCV was the main attraction of the event.
Measuring 8.5 meters (28 feet) long, 3.65 m (14 feet) wide, and 3.35 m (11 feet) tall, this vehicle is equipped with massive wheels that are designed to handle dunes, rocks and craters – all of which are very common on Mars. It also has a mobile lab attached to the rear, which is capable of being detached for the sake of conducting autonomous research in-situ.
The front end, meanwhile, is designed for scouting, and features life support, navigation and communication systems provided by the Global Positioning System. Rather than relying on gasoline or a Multi-Mission Radioisotope Thermoelectric Generator (MMRTP) like the Curiosity rover, the MRCV relies on an electric motor which is powered by solar panels and a 700-volt battery.
While it is not likely to be seeing the red sands of Mars in its lifetime, it is hoped that future generations of astronauts (including those who make the journey in the 2030s) will rely on mobile research labs like this one in order to explore the Martian surface, and use the mobile laboratory to conduct research whenever and wherever its called for.
To the casual observer, this vehicle may look a little Batman-esque. Not surprising, considering that the vehicle was built by the same people who built a replica the Batmobile featured in the Christopher Nolan remakes – Parker Brothers Concepts of Port Canaveral. To build the MRCV, they incorporated input from NASA experts to ensure that it was built with the conditions and resources of Mars in mind.
Between mid-July and August, NASA will be conducting a tour along the eastern seaboard, showcasing the MRCV in several major cities. But before it ships out, people will have a chance to see it at the Kennedy Space Center Visitor Complex for a few more weeks. After the tour is complete, the rover will return to the visitor complex to be part of the new Astronaut Training Experience (ATX) attraction opening this coming fall.
For a full list of the attractions and events taking place at the Kennedy Space Center during the Summer of Mars (or to book tickets online) be sure to check out their website.
I do wonder, would it be too much to hope that NASA will start working on a civilian model of this vehicle? I can imagine plenty of people around the world would be willing to pay good money to have something like this in their garage! And who doesn’t like the idea of being able to do a little off-roading followed by some in-situ research?
Further Reading: NASA, Kennedy Space Center
During the 18th century, famed French astronomer Charles Messier noted the presence of several “nebulous objects” in the night sky. Having originally mistaken them for comets, he began compiling a list of them so that others would not make the same mistake he did. In time, this list (known as the Messier Catalog) would come to include 100 of the most fabulous objects in the night sky.
One of these objects is the open star cluster known as Messier 46, which is located about 5,500 light years away in the southern Puppis constellation. Located in close proximity to another open cluster (Messier 47), this bright, rich cluster is about 300 million years old and is home to many stars – an estimated 500 – and some impressive nebulae too.
Crammed into about 30 light years of space, around 150 resolvable stars and up to 500 possible stellar members all took off together on a journey through space some 300 million years ago. At this point in time, they are about 5,400 light years away from our solar system, but they aren’t standing still. They’re pulling away from us at a speed of 41.4 kilometers per second.
If you notice something just a bit different about one of the stars along the northern edge – then you’ve caught on to one of the most famous features of Messier 46 – its resident planetary nebula. While radial velocities show it probably isn’t a true member of the cluster, it’s still a cool feature!
But, is there more to this cluster than that? You bet. Messier 46 has also been highly studied for its core properties. As Saurabh Sharma (et al) indicated in a 2006 study:
“The study of Galactic open clusters is of great interest in several astrophysical aspects. Young open clusters provide information about current star formation processes and are key objects for clarifying questions of Galactic structure, while observations of old and intermediate-age open clusters play an important role in studying the theories of stellar and Galactic evolution. A detailed analysis of the structure of coronae of open clusters is needed to understand the effects of external environments, like the Galactic tidal field and impulsive encounters with interstellar clouds, etc., on dynamical evolution of open clusters. Extensive studies of the coronal regions of clusters have not been carried out so far mainly because of unavailability of photometry in a large field around open star clusters. The ability to obtain improved photometry of thousands of stars means that large-scale studies of open clusters can be conducted to study the spatial structure and stability of Galactic open clusters. With the addition of photometry of a nearby field region it is possible to construct luminosity functions (LFs) and MFs, which are useful for understanding cluster-formation processes and the theory of star formation in open clusters.”
Messier 46 is an original discovery of Charles Messier, caught on February 19, 1771, just after he released his first catalog of entries. In his journal, he wrote:
“A cluster of very small stars, between the head of the Great Dog and the two hind feet of the Unicorn, [its position] determined by comparing this cluster with the star 2 Navis, of 6th-magnitude, according to Flamsteed; one cannot see these stars but with a good refractor; the cluster contains a bit of nebulosity.”
At the time of its discovery, Messier had not published his findings quite as immediately as we do today, so another astronomer also independently discovered this cluster as well… Caroline Herschel. “March 4th, [17]83. 1 deg S following the nebula near the 2nd Navis… a Nebula the figure is done by memory. My Brother observed it with 227 and found it to be, an astonishing number of stars. it is not in Mess. catalogue.”
It would be John Herschel in 1833 who would discover the planetary nebula while cataloging it: “The brightest part of a very fine rich cluster; stars of 10th magnitude; which fills the field. Within the cluster at its northern edge is a fine planetary nebula.”
But, as always, Admiral Symth has a way with words and observations. As he wrote of the object:
“A very delicate double star in a fine cluster, outlying the Galaxy, over Argo’s poop. A 8 1/2 [mag], and B 11, both pale white.A noble though rather loose assemblage of stars from the 8th to the 13th magnitude, more than filling the field, especially in length, with power 93; the most compressed part trending sf [south following, SE] and np [north preceding, NW]. Among the larger [brighter] stars on the northern verge is an extremely faint planetary nebula, which is 39 H. IV. [NGC 2438], and 464 of his son’s Catalogue. This was discovered by Messier in 1769, who considered it as being “rather enveloped in nebulous matter;” this opinion, however, must have arisen from the splendid glow of mass, for judging from his own remark, it is not likely that he perceived the planetary nebula on the north. WH [William Herschel], who observed it in 1786, expressly says, “no connexion with the cluster, which is free from nebulosity.” Such is my own view of attentively gazing; but the impression left on the senses, is that of awful vastness and bewildering distance, – yet including the opinion, that those bodies bespangled the vastness of space, may differ in magnitude and other attributes.”
Pretty amazing considering these gentlemen did all of their observations visually and knew nothing about today’s parallaxes, radial velocities or any other type of thing. May your own observations be as talented…
There is no simple way of finding Messier 46 in the finderscope of a telescope, but it’s not too hard with binoculars. Begin your hunt a little more than a fistwidth east/northeast of bright Sirius (Alpha Canis Majoris)… or about 5 degrees (3 finger widths) south of Alpha Monoceros. There you will find two open clusters that will usually appear in the same average binocular field of view. M46 is the easternmost of the pair.
It will appear slightly dimmer and the stars will be more concentrated. In the finderscope it will appear as a slightly foggy patch, while neighboring western M47 will try to begin resolution. Because M46’s stars are fainter, it is better suited to darker sky conditions, showing as a compression in binoculars and will resolve fairly well with even a small telescope. However, you will need at least a 6″ telescope to perceive the planetary nebula.
And here are the quick facts on this Messier Object to help you get started:
Object Name: Messier 46
Alternative Designations: M46, NGC 2437
Object Type: Open Galactic Star Cluster
Constellation: Puppis
Right Ascension: 07 : 41.8 (h:m)
Declination: -14 : 49 (deg:m)
Distance: 5.4 (kly)
Visual Brightness: 6.0 (mag)
Apparent Dimension: 27.0 (arc min)
We have written many interesting articles about Messier Objects here at Universe Today. Here’s Tammy Plotner’s Introduction to the Messier Objects, , M1 – The Crab Nebula, M8 – The Lagoon Nebula, and David Dickison’s articles on the 2013 and 2014 Messier Marathons.
Be to sure to check out our complete Messier Catalog. And for more information, check out the SEDS Messier Database.
Sources:
Understanding the Universe and how it has evolved over the course of billions of years is a rather daunting task. On the one hand, it involves painstakingly looking billions of light years into deep space (and thus, billions of years back in time) to see how its large-scale structure changed over time. Then, massive amounts of computing power are needed to simulate what it should look like (based on known physics) and seeing if they match up.
That is what a team of astrophysicists from the University of Zurich (UZH) did using the “Piz Daint” supercomputer. With this sophisticated machine, they simulated the formation of our entire Universe and produced a catalog of about 25 billion virtual galaxies. This catalog will be launched aboard the ESA’s Euclid mission in 2020, which will spend six years probing the Universe for the sake of investigating dark matter.
The team’s work was detailed in a study that appeared recently in the journal Computational Astrophysics and Cosmology. Led by Douglas Potter, the team spent the past three years developing an optimized code to describe (with unprecedented accuracy) the dynamics of dark matter as well as the formation of large-scale structures in the Universe.
The code, known as PKDGRAV3, was specifically designed to optimally use the available memory and processing power of modern super-computing architectures. After being executed on the “Piz Daint” supercomputer – located at the Swiss National Computing Center (CSCS) – for a period of only 80 hours, it managed to generate a virtual Universe of two trillion macro-particles, from which a catalogue of 25 billion virtual galaxies was extracted.
Intrinsic to their calculations was the way in which dark matter fluid would have evolved under its own gravity, thus leading to the formation of small concentrations known as “dark matter halos”. It is within these halos – a theoretical component that is thought to extend well beyond the visible extent of a galaxy – that galaxies like the Milky Way are believed to have formed.
Naturally, this presented quite the challenge. It required not only a precise calculation of how the structure of dark matter evolves, but also required that they consider how this would influence every other part of the Universe. As Joachim Stadel, a professor with the Center for Theoretical Astrophysics and Cosmology at UZH and a co-author on the paper, told Universe Today via email:
“We simulated 2 trillion such dark matter “pieces”, the largest calculation of this type that has ever been performed. To do this we had to use a computation technique known as the “fast multipole method” and use one of the fastest computers in the world, “Piz Daint” at the Swiss National Supercomputing Centre, which among other things has very fast graphics processing units (GPUs) which allow an enormous speed-up of the floating point calculations needed in the simulation. The dark matter clusters into dark matter “halos” which in turn harbor the galaxies. Our calculation accurately produces the distribution and properties of the dark matter, including the halos, but the galaxies, with all of their properties, must be placed within these halos using a model. This part of the task was performed by our colleagues at Barcelona under the direction of Pablo Fossalba and Francisco Castander. These galaxies then have the expected colors, spatial distribution and the emission lines (important for the spectra observed by Euclid) and can be used to test and calibrate various systematics and random errors within the entire instrument pipeline of Euclid.”
Thanks to the high precision of their calculations, the team was able to turn out a catalog that met the requirements of the European Space Agency’s Euclid mission, whose main objective is to explore the “dark universe”. This kind of research is essential to understanding the Universe on the largest of scales, mainly because the vast majority of the Universe is dark.
Between the 23% of the Universe which is made up of dark matter and the 72% that consists of dark energy, only one-twentieth of the Universe is actually made up of matter that we can see with normal instruments (aka. “luminous” or baryonic matter). Despite being proposed during the 1960s and 1990s respectively, dark matter and dark energy remain two of the greatest cosmological mysteries.
Given that their existence is required in order for our current cosmological models to work, their existence has only ever been inferred through indirect observation. This is precisely what the Euclid mission will do over the course of its six year mission, which will consist of it capturing light from billions of galaxies and measuring it for subtle distortions caused by the presence of mass in the foreground.
Much in the same way that measuring background light can be distorted by the presence of a gravitational field between it and the observer (i.e. a time-honored test for General Relativity), the presence of dark matter will exert a gravitational influence on the light. As Stadel explained, their simulated Universe will play an important role in this Euclid mission – providing a framework that will be used during and after the mission.
“In order to forecast how well the current components will be able to make a given measurement, a Universe populated with galaxies as close as possible to the real observed Universe must be created,” he said. “This ‘mock’ catalogue of galaxies is what was generated from the simulation and will be now used in this way. However, in the future when Euclid begins taking data, we will also need to use simulations like this to solve the inverse problem. We will then need to be able to take the observed Universe and determine the fundamental parameters of cosmology; a connection which currently can only be made at a sufficient precision by large simulations like the one we have just performed. This is a second important aspect of how such simulation work [and] is central to the Euclid mission.”
From the Euclid data, researchers hope to obtain new information on the nature of dark matter, but also to discover new physics that goes beyond the Standard Model of particle physics – i.e. a modified version of general relativity or a new type of particle. As Stadel explained, the best outcome for the mission would be one in which the results do not conform to expectations.
“While it will certainly make the most accurate measurements of fundamental cosmological parameters (such as the amount of dark matter and energy in the Universe) far more exciting would be to measure something that conflicts or, at the very least, is in tension with the current ‘standard lambda cold dark matter‘ (LCDM) model,” he said. “One of the biggest questions is whether the so called ‘dark energy’ of this model is actually a form of energy, or whether it is more correctly described by a modification to Einstein’s general theory of relativity. While we may just begin to scratch the surface of such questions, they are very important and have the potential to change physics at a very fundamental level.”
In the future, Stadel and his colleagues hope to be running simulations on cosmic evolution that take into account both dark matter and dark energy. Someday, these exotic aspects of nature could form the pillars of a new cosmology, one which reaches beyond the physics of the Standard Model. In the meantime, astrophysicists from around the world will likely be waiting for the first batch of results from the Euclid mission with baited breath.
Euclid is one of several missions that is currently engaged in the hunt for dark matter and the study of how it shaped our Universe. Others include the Alpha Magnetic Spectrometer (AMS-02) experiment aboard the ISS, the ESO’s Kilo Degree Survey (KiDS), and CERN’s Large Hardon Collider. With luck, these experiments will reveal pieces to the cosmological puzzle that have remained elusive for decades.
Further Reading: UZH, Computational Astrophysics and Cosmology
Summer is almost here, and for the northern hemisphere, that means warm nights for observing. But what to observe? We’re here with a list of events and targets for you to enjoy over the summer. Get your calendars handy, and start organizing some events with your friends, and then get out there!
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Welcome back to Constellation Friday! Today, in honor of the late and great Tammy Plotner, we will be dealing with the “Southern Crown” – the Corona Australis constellation!
In the 2nd century CE, Greek-Egyptian astronomer Claudius Ptolemaeus (aka. Ptolemy) compiled a list of all the then-known 48 constellations. This treatise, known as the Almagest, would be used by medieval European and Islamic scholars for over a thousand years to come, effectively becoming astrological and astronomical canon until the early Modern Age.
One of these was the Coronoa Australis constellation, otherwise known as the “Southern Crown”. This small, southern constellation is one of the faintest in the night sky, where it is bordered by the constellations of Sagittarius, Scorpius, Ara and Telescopium. Today, it is one of the 88 modern constellations recognized by the International Astronomical Union.
Corona Australis – the “Southern Crown” – is the counterpart to Corona Borealis – the “Northern Crown”. To the ancient Greeks, this constellation wasn’t seen as a crown, but a laurel wreath. According to some myths, Dionysus was supposed to have placed a wreath of myrtle as a gift to his dead mother into the underworld as well. Either way, this small circlet of dim stars definitely has the appearance of a wreath – or crown – and belongs to legend!
Like many of the Greek constellations, it is believed that Corona Australis was recorded by the ancient Mesopotamian in the MUL.APIN – where it may have been called MA.GUR (“The Bark”). While recorded by the Greeks as early as the 3rd century BCE, it was not until Ptolemy’s time (2nd century CE) that it was recorded as the “Southern Wreath”, a name that has stuck ever since.
In Chinese astronomy, the stars of Corona Australis are located within the Black Tortoise of the North and were known as ti’en pieh (“Heavenly Turtle”). During the Western Zhou period, the constellation marked the beginning of winter. To medieval Islamic astronomers, Corona Australis was known alternately as Al Kubbah (“the Tortoise”), Al Hiba (“the Tent”) or Al Udha al Na’am (“the Ostrich Nest”).
In 1920, the constellation was included in the list of 88 constellations formally recognized by the IAU.
Corona Australis is a small, faint constellation that has no bright stars, consists of 6 primary stars and contains 14 stellar members with Bayer/Flamsteed designations. There is one meteor shower associated with Corona Australis – the Corona-Australids which peak on or about March 16 each year and are active between March 14th through the 18th. The fall rate is minimal, with an average of about 5 to 7 per hour.
It’s brightest star, Alpha Coronae Australis (Alphekka Meridiana), is a class A2V star located about 130 light years from Earth. It is also the only properly-named star in the constellation. It’s second brightest star, Beta Coronae Australis, is a K-type bright giant located approximately 510 light years distant.
And then there’s R Coronae Australis, a well-known variable star that is located approximately 26.8 light years from Earth. This relatively young star is still in the process of formation – accreting material onto its surface from a circumstellar disk – and is located within a star forming region of dust and gas known as NGC 6726/27/29.
Corona Australis is also home to several Deep Sky Objects, such as the Corona Australis Nebula. This bright reflection nebula, which is located about 420 light years away, was formed when several bright stars became entangled with a dark cloud of dust. The cloud is a star-forming region, with clusters of young stars embedded inside, and consists of three nebulous regions – NGC 6726, NGC 6727, and NGC 6729.
Other reflection nebulas include NGC 6726/6727 and the fan-shaped NGC 6729. Corona Australis also boasts many star clusters, such as the large, bright globular cluster known as NGC 6541. There’s also the Coronet cluster, a small open star cluster that is located approximately 420 light years from Earth. The cluster lies at the heart of the constellation and is one of the nearest known regions that experiences ongoing star formation.
Corona Australis is visible at latitudes between +40° and -90° and is best seen at culmination during the month of August. It can be explored using both binoculars and small telescopes. Let’s start with binoculars and a look at Alpha Coronae Australis – the only star in the constellation to have a proper name.
Called Alfecca Meridiana – or “the sixth star in the river Turtle” – Alpha is a spectral class A2V star which is located about 160 light years from Earth. Alfecca Meridiana is a fast rotator, spinning at least at 180 kilometers per second at its equator, 90 times faster than our Sun and making a full rotation in about 18 hours.
Even more interesting is the fact that Alpha is a Vega-like star, pouring out excess infrared radiation that appears to be coming from a surrounding disk of cool dust. Just what does that mean? It means that Alfecca Meridiana could possibly have a planetary system!
Now have a look at Beta. Although this orange class K (K0) giant star is rather ordinary, where it’s at is not. It’s sitting on the edge of the Corona Australis Molecular Cloud, a dusty, dark star-forming region which contains huge amounts of nebulae. While Beta does seem pretty plain, it is almost 5 times larger than our Sun and 730 times brighter. Not bad for a star that’s about a hundred million years old!
Now, take a look at a really bizarre star – Epsilon Coronae Australis. At a distance of 98 light years, there doesn’t seem to be much going on with this fifth magnitude, faint stellar point, but there is. That’s because Epsilon isn’t one star – but two. Epsilon is an eclipsing binary with two very similar eclipses that take place within an orbital period of 0.5914264 days, as first a faint star passes in front of the bright one that gives us 95 or so percent of the light, and then the bright one passes in front of the fainter.
So what does that mean? It means that if you sit right there at watch, you can see the changes in less than 7 hours. While watching for hours for a half magnitude drop might not seem like your cup of tea, think about what you’re watching…. These two stars are actually contacting each other as they go by! Can you imagine stars spinning so fast that they produce huge amounts of magnetic activity and dark starspots that also add to the variation as they swing in and out of view? Sharing mass and pulling at each other in just a matter of hours? Now that’s a show worth watching…
Now try variable star R Coronae Borealis (RA 19 53 65 Dec -36 57 97). Here we have another unusual one – a “Herbig Ae/Be” pre-main sequence star. The star is an irregular variable with more frequent outbursts during times of greater average brightness, but it also has a long-term periodic variation of about 1,500 days and about 1/2 magnitude that may be linked to changes in its circumstellar shell, rather than to stellar pulsations. Although R Coronae Australis is 40 times brighter than Sol, and about 2 to 10 times larger, most of its stellar luminosity is obscured because the star is still accreting matter. Protoplanetary bodies? Maybe!
Keep your binoculars handy and get out the telescope as we start deep sky first with NGC 6541. Also known as Caldwell 78 and Bennett 104, this beautiful 6th magnitude globular cluster was first discovered by N. Cacciatore on March 19, 1826. It belongs in our Milky Way galaxy’s inner halo structure and it is rather metal poor in structure – but beautifully resolved in a telescope. In binoculars, this splendid southern sky study will appear as a large faint globular with a bright star to the northeast.
Now head for the telescope and NGC 6496 (RA 17 59 0 Dec -44 16). At right around magnitude 9, this globular cluster also has a bonus nebula attached to it. Collectively known as Bennett 100, Dreyer described it as a “nebula plus cluster” but it will take dark skies to make out both. Look for 5th magnitude star SAO 228562 that accompanies it. In a small telescope, only a hazy, faint patch can be seen, but larger aperture does get some resolution.
Try emission/reflection nebula NGC 6729 (RA 19 01 55 Dec -36 57 30) next. In a wide field, you can place NGC 6726, NGC 6727, NGC 6729 and the double star BSO 14 in the same eyepiece. The three nebulae NGC 6726-27, and NGC 6729 were discovered by Johann Friedrich Julius Schmidt, during his observations at Athen Observatory in 1861. The nebula are very faint and almost comet-like in appearance and the double star is easily split. Don’t forget to mark your notes as having captured Caldwell 68!
We have written many interesting articles about the constellation here at Universe Today. Here is What Are The Constellations?, What Is The Zodiac?, and Zodiac Signs And Their Dates.
Be sure to check out The Messier Catalog while you’re at it!
For more information, check out the IAUs list of Constellations, and the Students for the Exploration and Development of Space page on Canes Venatici and Constellation Families.
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During late summer in the Southern hemisphere on Mars, the angle of the sunlight as it strikes the surface brings out some subtle details on the planet’s surface.
In this image, the HiRISE camera on board NASA’s Mars Reconnaissance Orbiter (MRO) captured an area of frozen carbon dioxide on the surface. Some of the carbon dioxide ice has melted, giving it a swiss-cheese appearance. But there is also an unusual hole or crater on the right side of the image, with some of the carbon dioxide ice clearly visible in the bottom of the pit.
NASA scientists are uncertain what exactly caused the unusual pit. It could be an impact crater, or it could be a collapsed pit caused by melting or sublimation of sub-surface carbon dioxide ice.
MRO has been in orbit around Mars for over 10 years, and has completed over 50,000 orbits. The MRO has two cameras. The CTX camera is lower resolution, and has imaged over 99% of the Martian surface. HiRISE is the high-resolution camera that is used to closely examine areas and objects of interest, like the unusual surface pit in this image.
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