Sandra Bullock as Ryan Stone in Warner Bros. Pictures' dramatic thriller "Gravity," a Warner Bros. Pictures release.
Image Credit: Courtesy of Warner Bros. Pictures
Actors for a new movie coming out in October 2013 received tips about life in space from NASA astronaut Cady Coleman. “Gravity” is the story of two astronauts (played by George Clooney and Sandra Bullock) whose shuttle is destroyed by a run-in with space junk during an EVA, stranding them both in orbit and struggling for survival.
While developing her role, Bullock gave Coleman a call while she was aboard the space station. At the time, the actress asked Coleman to elaborate on what it’s like living and moving about in microgravity. “I told her that I had long hair, and if you pulled a hair out and pushed it against something, you could move yourself across the space station,” said Coleman. “That’s how little force it takes.”
You can see more of their discussion below, as well as the heart-pounding trailer for the movie:
NASA says that although this dire scenario makes for gripping Hollywood entertainment, NASA actively works to protect its astronauts and vehicles from the dangers portrayed in the movie. From protective shielding and meticulous and methodical training on the ground and in space covering everything from spacewalking to fires or decompression inside the space station, NASA’s ground crews and astronauts are as prepared as they can be for potential anomaly, no matter how remote they may be.
Black holes are the most exotic and awe inspiring objects in the Universe.
Take the mass of an entire star. Compress it down into an object so compact that the force of gravity defies comprehension.
Nothing, not even light, can escape the pull of gravity from a black hole.
The idea was first conceived in the 18th century by the geologist John Mitchell. He realized that if you could compress the Sun down by several orders of magnitude, it would have gravity so strong that you’d need to be going faster than the speed of light to escape it.
Initially, black holes were considered nothing more than abstract mathematical concepts; even Einsten assumed they didn’t actually exist. But in 1931, the astronomer Chandrasekhar calculated that certain high mass stars might be able to collapse into black holes after all.
They turned out to be real, and over the next few decades, astronomers found many examples out in the Universe.
Stars are held in perfect balance by two opposing forces. There’s the inward pressure of gravity, attempting to collapse the star, counteracted by the outward pressure of the emitted radiation.
This artist’s concept illustrates a supermassive black hole with millions to billions times the mass of our sun. Supermassive black holes are enormously dense objects buried at the hearts of galaxies. Image credit: NASA/JPL-CaltechAt the core, millions of tonnes of hydrogen are being converted into helium every second, releasing gamma radiation. This fusion process is an exothermic reaction, meaning it releases more energy than it requires.
As the star consumes the last of its hydrogen, it switches to the stockpiles of helium that it has built up. After it runs out of helium, it switches to carbon, and then oxygen.
Since the star continues to pump out radiation, it balances out the gravitational forces trying to compress it.
Stars with the mass of our Sun pretty much stop there. Not massive enough to continue the fusion reaction, beyond oxygen, they become a white dwarf and cool down.
But for stars with about 5 times the mass of our Sun, the fusion process continues further up the periodic table to silicon, aluminum, potassium, and so on, all the way to iron.
No energy can be produced by fusing iron atoms together. It’s the stellar equivalent of ash.
And so, in a fraction of a second, the radiation from the star turns off. Without that outward pressure from the radiation, gravity wins out and the star implodes. An entire star’s mass collapses down into a smaller and smaller volume of space.
The velocity you would need to escape from the star goes up, until not even light is going fast enough to escape.
And this is how you form a black hole.
Well, that’s the main way.
You can also get black holes when dense objects, like neutron stars, collide with one another.
And then there are the supermassive black holes at the heart of every galaxy. And to be honest, astronomers still don’t know how those monsters formed.
This chart provides and accurate size comparison for every science fiction starship imaginable. Credit: Dirk Loechel. Click for original large version.
Have you always wanted to know how a Xurian Scout Fighter compares to a Valor-class Type-2 Valkyrie Attack Fighter? Wonder no more. DeviantARTist Dirk Loechel has created what is likely the most accurate and complete size comparison chart of almost every science fiction starship, from famous Star Trek and Stars Wars battle cruisers to ships from games like Halo to vessels from obscure sci-fi books. This new chart is an updated version of one Loechel made earlier. It looks like Loechel is taking suggestions for doing another update if you find he’s missed some.
Click on the image above to have access to the large original version on DeviantART, and enjoy the diversion.
While on the ISS, astronaut Karen Nyberg made this dinosaur for her son, created from reclaimed velcro-like fabric that lines the Russian food containers. Credit: Karen Nyberg via Pinterest.
Astronaut Karen Nyberg wins Pinterest. Not only has she made her 3-year old son a dinosaur toy, she created it while IN SPACE, and scored a super-coup by making it from the reclaimed velcro-like fabric that lines the Russian food containers on the International Space Station. Nyberg said the dinosaur is stuffed with scraps from a used t-shirt.
Upcycling in space … wow. She’s clearly now outdone every crafter both on and off the planet. As one commenter on Pinterest said, “How awesome to have someone promoting/demonstrating crafting, science and education and a mother’s love from the ISS!”
You can see more of Nyberg’s handiwork while she’s been in space, as well as pictures she’s taken of planet Earth, the science experiments she’s doing and more on her Pinterest page. She will be on the ISS until November 11.
The rock chosen for the first contact science investigations for the Curiosity rover. Credit: NASA/JPL-Caltech
A strange rock encountered by the Mars Curiosity rover early in its mission has few similarities to other rocks found on the Red Planet, a new study says. In fact, the “Jake_M” rock is most similar to a rare kind of Earth rock called a mugearite, which is often found in ocean islands and continental rift zones.
“Such rocks are so uncommon on Earth that it would be highly unlikely that, if you landed a spacecraft on Earth in a random location, the first rock you encountered within a few hundred meters of your landing site would be an alkaline rock like Jake_M,” stated Edward Stolper, a geology professor at the California Institute of Technology.
Jake_M is named after Jacob “Jake” Matijevic, a Curiosity operations systems chief engineer who died two weeks after the rover landed last year. The rock was sampled about two weeks after Curiosity hit the surface, and was revealed to have sodium and potassium in it (which makes it chemically alkaline.)
The NASA team threw in every bit of data they could to model the Mars Curiosity landing. Credit: NASA
It’s probable that the rock came to be, the scientists said, after partially melting in the interior of Mars and then coming up to the surface. “As it cooled, crystals formed, and the chemical composition of the remaining liquid changed (just as, in the making of rock candy, a sugar-water solution becomes less sweet as it cools and sugar crystallizes from it),” CalTech stated.
Models examining the formation conditions suggest that Jake_M originated from an area some tens of miles or kilometers in the interior of Mars relative to the surface, and that the magma it formed in might have had a reasonably high proportion of dissolved water. This type of magma (called alkaline magma) is uncommon on Earth, but may be more common on Mars than previously believed.
You can read more details about the rock, as well as a series of four other papers published about science from MSL in the Sept. 27 edition of Science.
NASA's Mars rover Curiosity used a new technique, with added autonomy for the rover, in placement of the tool-bearing turret on its robotic arm during the 399th Martian day, or sol, of the mission. This image from the rover's front Hazard Avoidance Camera (Hazcam) on that sol shows the position of the turret during that process, with the Alpha Particle X-ray Spectrometer (APXS) instrument placed close to the target rock. Credit: NASA/JPL-Caltech
NASA’s Curiosity rover has discovered a new patch of pebbles formed and rounded eons ago by flowing liquid water on the Red Planet’s surface along the route she is trekking across to reach the base of Mount Sharp – the primary destination of her landmark mission.
Curiosity made the new finding at a sandstone outcrop called ‘Darwin’ during a brief science stopover spot called ‘Waypoint 1’.
Before arriving at Waypoint 1, the question was- “Did life giving water once flow here on the Red Planet?
The answer now is clearly ‘Yes!’ – And it demonstrates the teams wisdom in pausing to inspect ‘Darwin’.
The discovery at Darwin is significant because it significantly broadens the area here that was altered by flowing liquid water.
This mosaic of nine images, taken by the Mars Hand Lens Imager (MAHLI) camera on NASA’s Mars rover Curiosity, shows detailed texture in a conglomerate rock bearing small pebbles and sand-size particles. Credit: NASA/JPL-Caltech/MSSS
The presence of water is an essential prerequisite for the formation and evolution of life.
“Curiosity has arrived at Waypoint 1,” project scientist John Grotzinger, of the California Institute of Technology in Pasadena, told Universe Today at the time.
The robot pulled into ‘Waypoint 1’ on Sept. 12 (Sol 392).
“It’s a chance to study outcrops along the way,” Grotzinger told me.
This mosaic of four images taken by the Mars Hand Lens Imager (MAHLI) camera on NASA’s Mars rover Curiosity shows detailed texture in a ridge that stands higher than surrounding rock. The rock is at a location called “Darwin,” inside Gale Crater. Exposed outcrop at this location, visible in images from the High Resolution Imaging Science Experment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter, prompted Curiosity’s science team to select it as the mission’s first waypoint for several days during the mission’s long trek from the “Glenelg” area to Mount Sharp. Image Credit: NASA/JPL-Caltech/MSSS
The six wheeled rover is in the initial stages of what is sure to be an epic trek across the floor of her landing site inside the nearly 100 mile wide Gale Crater – that is dominated by humongous Mount Sharp that reaches over 3 miles (5 Kilometers) into the red Martian Sky.
“We examined pebbly sandstone deposited by water flowing over the surface, and veins or fractures in the rock,” said Dawn Sumner of University of California, Davis, a Curiosity science team member with a leadership role in planning the stop, in a NASA statement about Darwin and Waypoint 1.
“We know the veins are younger than the sandstone because they cut through it, but they appear to be filled with grains like the sandstone.”
Curiosity deploys robot arm to investigate the ‘Darwin’ rock outcrop up close at ‘Waypoint 1’ on Sept 20 (Sol 399). This photo mosaic was assembled from navcam images taken on Sept 20, 2013. Credit: NASA/JPL-Caltech/Ken Kremer/Marco Di Lorenzo
Waypoint 1 is the first of up to five waypoint stops planned along the roving route that stretches about 5.3 miles (8.6 kilometers) between the “Glenelg” area, where Curiosity worked for more than six months through the first half of 2013, and the currently planned entry point at the base of Mount Sharp.
To date, the robot has now driven nearly 20% of the way towards the base of the giant layered Martian mountain she will eventually scale in search of life’s ingredients.
“Darwin is named after a geologic formation of rocks from Antarctica,” Grotzinger informed Universe Today.
‘Waypoint 1’ was an area of intriguing outcrops that was chosen based on high resolution orbital imagery taken by NASA’s Mars Reconnaissance Orbiter (MRO) circling some 200 miles overhead.
Investigation of the conglomerate rock outcrop dubbed ‘Darwin’ was the top priority of the Waypoint 1 stop.
The finding of a cache of watery mineral veins was a big added science bonus that actually indicates a more complicated story in Mars past – to the delight of the science team.
“We want to understand the history of water in Gale Crater,” Sumner said.
“Did the water flow that deposited the pebbly sandstone at Waypoint 1 occur at about the same time as the water flow at Yellowknife Bay? If the same fluid flow produced the veins here and the veins at Yellowknife Bay, you would expect the veins to have the same composition.’
“We see that the veins are different, so we know the history is complicated. We use these observations to piece together the long-term history.”
The Rover inspected Darwin from two different positions over 4 days, or Martian Sols and conducted ‘contact science’ by deploying the robotic arm and engaging the science instrument camera and spectrometer mounted on the turret at the arms terminus.
The Alpha Particle X-ray Spectrometer (APXS) collected spectral measurements of the elemental chemistry and the Mars Hand Lens Imager is a camera showing the outcrops textures, shapes and colors.
Curiosity investigates the ‘Darwin’ rock outcrop up close after arriving for a short stay at ‘Waypoint 1’ on Sept 12 (Sol 392). This photo mosaic was assembled from navcam images taken on Sept 12, 2013. Credit: NASA/JPL-Caltech/Ken Kremer/Marco Di Lorenzo
What’s the origin of Darwin’s name?
“Darwin comes from a list of 100 names the team put together to designate rocks in the Mawson Quadrangle – Mawson is the name of a geologist who studied Antarctic geology,” Grotzinger told me.
“We’ll stay just a couple of sols at Waypoint 1 and then we hit the road again,” Grotzinger told me.
And indeed on Sept. 22, the rover departed Darwin and Waypoint 1 on a westward heading to resume the many months long journey to Mount Sharp.
Learn more about Curiosity, Mars rovers, MAVEN, Orion, Cygnus, Antares, LADEE and more at Ken’s upcoming presentations
Oct 3: “Curiosity, MAVEN and the Search for Life on Mars – (3-D)”, STAR Astronomy Club, Brookdale Community College & Monmouth Museum, Lincroft, NJ, 8 PM
Oct 8: NASA’s Historic LADEE Lunar & Antares/Cygnus ISS Rocket Launches from Virginia”; Princeton University, Amateur Astronomers Assoc of Princeton (AAAP), Princeton, NJ, 8 PM
An adapter recently installed on the ISS's Canadarm II, with the message, "Installed by your friendly Expedition 36 Crew." Credit: NASA/ESA/Luca Parmitano.
We humans have certain tendencies toward the eternal. We like to leave our mark by somehow saying “I was here!” or send messages to the future about what we’ve accomplished. We’re also intrigued by things like the Voyager record, the Pioneer plaque, and we all love those “send your name on a spacecraft” opportunities NASA has.
This recent image, above, posted by astronaut Luca Parmitano on Twitter of a message written on a new piece for the International Space Station’s Canadarm 2 is an example of leaving a little message to the future (albeit, one that the majority of us might never get to see) and it prompted me to wonder if there are more “secret messages” like that on the ISS — messages of remembrance or good wishes from the people who built, designed or installed various components, or messages passed down from one crew to the next.
NASA astronaut Tom Marshburn, who returned from a 5-month stint on the ISS in May of 2013, said there are plenty of memorable messages, signatures and objects left by the station’s builders or previous crews.
“We did a lot of maintenance during our flight and rotated out a lot of the experiment racks and we saw many signatures on the internal hull or on the inside parts of the racks,” Marshburn told Universe Today via phone from Johnson Space Center. “Things like ‘Greetings from the Water Recovery team!’ with everyone’s signature. That’s fairly prevalent on the inside, particularly behind the racks, but not in plain view.”
But he’s never seen anything on the external parts of the space station before.
“I have heard that engineers who have built different components and even external structures, like to sign their names to internal pieces that no one can actually see, but the engineers know their name is up in space,” he said. “I’ve done three spacewalks, and I’ve never seen anything like that on the outside — like in the picture from Luca Parmitano — so that’s a rarity to see something like that.”
There are some signatures plainly visible on the interior, however: signed mission stickers from all the visiting Space Shuttle crews and the Expedition crews adorn the walls in certain parts of the ISS.
But how about other messages that crews leave for future inhabitants?
Japan Aerospace Exploration Agency astronaut Koichi Wakata exercises using the Advanced Resistive Exercise Device (ARED) in the International Space Station. (NASA)
Marshburn said there are several “helpful” notes that are left by former crew members to assist or instruct future crews — important ‘lessons learned’ or little reminders.
“One of the favorite messages left by a former resident of the station is near the resistive exercise machine,” Marshburn said. “This machine allows you to lift the equivalent of 600 pounds, so there is a lot of stored energy there and you have to be careful with it, making sure you follow procedures carefully. There is a placard there that someone just wrote with a Sharpie: ‘Nothing is as important as what you are doing right now.’ That has become a mantra for a lot of people on the ISS, and we quoted quite often. I really like that one.”
There’s also a nice ‘aide-mémoire’ in the space station bathroom.
“Everyone has to urinate into a funnel that goes into a hose,” Marshburn explained. “We are pretty good about cleaning ourselves up in the bathroom, but some crewmembers have not been so good about cleaning up the equipment because written in Sharpie on the wall in the bathroom is, ‘Blessed are those who wipe the funnel.’ That’s just a good little reminder.”
In addition to messages, there are objects left by previous crews that end up as talismans or things that are used over and over.
A closeup of Gort in the Destiny Lab on the ISS. Credit: NASA.
“There is a four-inch version of Gort, the robot figure from the movie “The Day the Earth Stood Still” stuck on the wall where we gather in the Destiny Lab for our daily planning conferences,” Marshburn said. “He sometimes gets unstuck and floats around the ISS, so whenever we find him wandering around, we stick him back up on the wall. He’s kind of ubiquitous.”
There’s also a little toy astronaut figure that ends up floating around and showing up in different places.
“We don’t know who brought them up, but they have been retained and remain as mascots for the crews,” Marshburn said.
The toy left on the ISS that Marshburn enjoyed the most was a ping pong ball.
“That is a wonderful toy,” he said. “While you are eating, you can bounce it off the wall and figure out the best angles to have it come right back to you. Or you can spin it around a hatch and the centripetal force will just keep it spinning around and around.”
Chris Hadfield in the Cupola of the ISS. Credit: NASA
Also on board are musical instruments — an electric piano, guitar and ukulele – that get a lot of use. Additionally, previous astronauts have left reading material, so by now there is a shoebox-sized library of books to read.
“After working on computers most of the day, it’s nice to grab a real book and read during your off time,” Marshburn said.
Since Marshburn and his crewmates — Canadian astronaut Chris Hadfield and Russian cosmonaut Roman Romanenko — launched to the space station on December 19, 2012, they really enjoyed the bag-full of holiday ornaments that are on board. “There’s a 2-foot Christmas tree, stockings, and an elf hat,” he said, “which was nice because it was a tiny piece of home, a little bit of Christmas.”
There’s also Mardi Gras hats, Happy Birthday signs, and flags of each country associated with the International Space Station.
So, any other secret “just between astronauts” messages up on the space station?
“There aren’t any that I saw or even know about that I couldn’t share with you!” Marshburn said with a laugh. “But I don’t know how much mission control even knows about some of these things.”
Astronaut Tom Marshburn during an EVA on May 11, 2013 to replace a pump controller box on the International Space Station that was leaking coolant. Credit: NASA.
The launch of Chan'ge-2 with 3rd stage (arrowed) now known as 2010 Q (Credit CALT).
Can’t find asteroid 2010 QW1 in the Minor Planet Database? No, the “Men in Black” didn’t secretly remove this Earth-orbiting asteroid from the listing… but recent top-notch detective work by astronomers did.
The mystery of this object all started back on August 23rd of this year, when the PanSTARRS sky survey based on the summit of Haleakala on the island of Maui in Hawai’i spotted an asteroid that was given the provisional designation of 2013 QW1.
The object was in a wide-ranging orbit around the Earth, leading astronomers to wonder if it was a naturally captured asteroid or perhaps space debris from a previous launch. Either solution to the dilemma would be fascinating. Our large Moon keeps the Earth pretty well swept clear of debris, though a “second Moon,” however small, would be an interesting find. And if 2013 QW1 were to prove artificial, it just might be a piece of history.
The European Space Agency’s NEO Coordination Centre decided to take up the challenge. A call went out to track and observe the 2013 QW1, and a team led by Elisabetta Dotto of INAF-Observatorio di Roma & Maria Barucci & Davide Perna of the Observatoire de Paris managed to get time on the Italian Telescopio Nazaionale Galileo based at La Palma to obtain a spectrum of the object.
“It was a bit of a challenge, because the object was moving fast with respect to a typical NEO,” said Dr. Perna in a recent ESA press release.
The team used an instrument known as DOLORES to make the crucial measurements. DOLORES stands for the Device Optimized for LOw RESolution. The spectrum obtained in the early morning hours of August 25th shows something much brighter than your typical asteroid, but is characteristic of a painted metallic object.
The launch of Chan’ge-2 with 3rd stage (arrowed) now known as 2013 QW1 (Credit: CALT).
And thus, 2013 QW1 was removed from the ledger of NEO asteroids maintained by the IAU Minor Planet Center (MPEC). And the leading suspect? The third stage booster of a Chinese Long March 3C rocket that launched the Chang’e 2 spacecraft from Xichang, China on October 1st, 2010.
Chang’e-2 entered lunar orbit 8 days after launch, and departed on June 8th of the following year after studying and mapping the Moon. Chang’e-2 then went on to become the first spacecraft to directly reach the L2 Lagrange point 1.5 million kilometres beyond Earth from lunar orbit. The spacecraft also made the first flyby of NEO asteroid 4179 Toutatis on December 13th of last year. The probe is estimated to continue functioning into 2014, and will be used to hone China’s ability to track objects in deep space.
The NORAD tracking identification assigned to the 3rd stage booster that launched Chan’ge-2 is 2010-50B.
This sort of discovery is not without precedent.
The launch of Apollo 12, with the 3rd stage (arrowed) would one day be “asteroid Joo2E3”. (Credit: NASA).
On September 3rd, 2002, amateur astronomer Bill Yeung discovered an asteroid tentatively designated J002E3. Subsequent studies revealed that the asteroid had a spectrum consistent with that of titanium oxide paint, a decidedly unasteroid-like coating for a space rock to sport. This was, however, a common veneer in use during the Apollo era, and it is now known that J002E3 is the S-IVB third stage booster that launched the second mission to land men on the Moon on November 14th, 1969. Unlike other boosters, such as the one that launched Apollo 14, the Apollo 12 3rd stage did not impact the Moon as part of seismic experiments. After a brief period as a “pseudo-moon” of the Earth, J002E3 was kicked out into solar orbit in June 2003 and may return to our neighborhood once again in the 2040s.
NASA’s Lunar Reconnaissance Orbiter has documented the lunar crash sites of these historic boosters. It’s of note that the Apollo 10 Lunar Module Snoopy remains discarded out in solar orbit as well, having been used as a dress rehearsal for the historic Apollo 11 landing. Apollo 10 never landed on the Moon. Efforts have been made by UK astronomer Nick Howes to recover it as well.
And there are more relics of the Space Age awaiting discovery. One of the first things we always check in the case of a pass by a newly discovered NEO closer than the Moon to the Earth is its history, to see if it matches up with any launches headed out beyond Earth orbit in the past.
And the upcoming Mars launches of MAVEN and India’s Mars Orbiter Mission in October & November will be the first to depart Earth orbit since 2011. These will give future generations of asteroid hunters new human-made space hardware to ponder.
The B612 Foundation’s asteroid-hunting Sentinel Space Telescope will also “up the game,” scouting for asteroids from a vantage point interior to the Earth’s orbit. Sentinel is slated for launch in 2016 atop a SpaceX Falcon 9 rocket.
And no, the fabled “Black Knight” satellite of UFO conspiracy buffs’ dreams is nowhere to be found.
What other fascinating relics of the Space Age lie are out there in the solar system, waiting to tell their tale?
The Hulk (Bruce Banner), as portrayed in The Avengers. Credit: Marvel & Subs
When Bruce Banner gets angry, he gets big and green and strong and well, vengeful. The Hulk is the stuff of comic book legend and as Mark Ruffalo recently showed us in The Avengers, Banner’s/Hulk’s personality can transform on a dime.
Turns out rapid transformations are the case in astronomy, too! Scientists found a peculiar neutron star that can change from radio pulsar, to X-ray pulsar, back and forth. In the Hulk’s case, a big dose of gamma rays likely fuelled his ability to transform. This star’s superpowers, however, likely come from a companion star.
“What we’re seeing is a star that is the cosmic equivalent of ‘Dr. Jekyll and Mr. Hyde,’ with the ability to change from one form to its more intense counterpart with startling speed,” stated Scott Ransom, an astronomer at the National Radio Astronomy Observatory.
“Though we have known that X-ray binaries — some of which are observed as X-ray pulsars — can evolve over millions of years to become rapidly spinning radio pulsars, we were surprised to find one that seemed to swing so quickly between the two.”
A neutron star and its companion flipping between accretion (when it emits X-rays) and when accretion has stopped (when it emits radio pulses). Credit: Bill Saxton; NRAO/AUI/NSF. Animation by Elizabeth Howell
The star’s double personality came to light after astronomers made an accidental double-discovery. IGR J18245-2452, as the star is called, was flagged as a millisecond radio pulsar in 2005 using the National Science Foundation’s Robert C. Byrd Green Bank Telescope. Then this year, another team found an X-ray pulsar in the same region of the star cluster M28.
It took a little while to sort out the confusion, we’re sure, but eventually astronomers realized it was the same object behaving differently. That said, they were mighty confused: “This was particularly intriguing because radio pulses don’t come from an X-ray binary and the X-ray source has to be long gone before radio signals can emerge,” stated lead researcher Alessandro Papitto, who is with of Institute of Space Sciences in Catalunya (Institut d’Estudis Espacials de Catalunya) in Spain.
The key, it turns out, comes from the interplay with the star’s companion. Material doesn’t flow continuously, as astronomers previously believed is true of these system types, but in bunches. Starting and stopping the flow then led to swings in the behavior, making the star alternate between X-ray and radio emissions.
– A neutron star that has a normal star nearby forms an X-ray binary, which happens when the neutron star poaches starstuff off its companion. When the material hits the neutron star, the stuff gets really hot and emits X-rays.
– When the material stops, magnetic fields on the neutron produce radio waves. These appear to blink on and off from the perspective of Earth, as the neutron rotates super-fast (several times a second).
In the case of IGR J18245-2452, it behaved like an X-ray binary star for about a month, stopped suddenly, and then sent out radio waves for a while before flipping back again. (A month is less than a blink in astronomical terms, when you recall the universe is 13.8 billion years old.)
To take the longer view, astronomers used to believe that X-ray binaries could evolve into radio emitters over time. Now, though, it appears a star can be these two things at almost the same time.
“During periods when the mass flow is less intense, the magnetic field sweeps away the gas and prevents it from reaching the surface and creating X-ray emission,” NASA stated. “With the region around the neutron star relatively gas free, radio signals can easily escape and astronomers detect a radio pulsar.”
A whole suite of telescopes in Earth and space contributed to this discovery, but of note: the X-ray source was first spotted with the International Gamma-Ray Astrophysics Laboratory (INTEGRAL). You can read more details in the paper published in Nature.
Artist's conception of an Earth-like exomoon orbiting a gaseous planet. Image credit: Avatar, 20th Century Fox
Astronomers believe that hidden deep within the wealth of data collected by NASA’s Kepler mission are minuscule signatures confirming the presence of exomoons. With such a promising discovery on the horizon, researchers are beginning to address the factors that may deem these alien moons habitable.
A new study led by Dr. René Heller from McMaster University in Canada and Dr. Jorge Zuluaga from the University of Antioquia in Colombia takes a theoretical look at habitability – exploring the key components that may make exomoons livable. While stellar and planetary heating play a large role, it’s quickly becoming clear that the magnetic environments of exomoons may be even more critical.
An exoplanet’s habitability is first and foremost based on the circumstellar habitable zone – the temperature band around a star in which water may exist in its liquid state. Exomoons, however, have an additional set of constraints that affect their habitability. In a set of recent papers, Dr. Heller and Dr. Rory Barnes (from the University of Washington) defined a “circumplanetary habitable edge,” which is roughly analogous to the circumstellar habitable zone.
Here the question of habitability is based on the relationship between the exomoon and its host planet. The additional energy source from the planet’s reflected starlight, the planet’s thermal emission, and tidal heating in the moon may create a runaway greenhouse effect, rendering the exomoon uninhabitable.
One look at Io – Jupiter’s closest Galilean satellite – shows the drastic effects a nearby planet may have on its moon. The strong gravitational pull of Jupiter distorts Io into an ellipsoid, whose orbit around the giant planet is eccentric due to perturbations from the other Galilean moons. As the orbital distance between Jupiter and Io varies on an eccentric orbit, Io’s ellipsoidal shape oscillates, which generates enormous tidal friction. This effect has led to over 400 active volcanic regions.
Note that this is an edge, not a zone. It defines only an innermost habitable orbit, inside which a moon would become uninhabitable. The exomoon must exist outside this edge in order to avoid intense planetary illumination or tidal heating. Exomoons situated in distant orbits, well outside the circumplanetary habitable edge, have a chance at sustaining life.
But the question of habitability doesn’t end here. Harmful space radiation can cause the atmosphere of a terrestrial world to be stripped off. Planets and moons rely heavily on magnetic fields to act as protective bubbles, preventing harmful space radiation from depleting their atmospheres.
With this in mind, Heller and Zuluaga set out to understand the evolution of magnetic fields of extrasolar giants, which are thought to affect their moons. It’s unlikely that small, Mars-sized exomoons will produce their own magnetic fields. Instead, they may have to rely on an extended magnetic field from their host planets.
This planetary magnetosphere is created by the shock between the stellar wind and the intrinsic magnetic field of the planet. It has the potential to be huge, protecting moons in very distant orbits. Within our own Solar System Jupiter’s magnetosphere ends at distances up to 50 times the size of the planet itself.
Heller and Zuluaga computed the evolution of the extent of a planetary magnetosphere. “Essentially, as the pressure of the stellar wind decreases over time, the planetary magnetic shield expands,” Dr. Heller told Universe Today. “In other words, the planetary magnetosphere widens over time.”
Evolution of the host planets magnetosphere (represented by the blue line) for Neptune-, Saturn-, and Jupiter-like planets. All increase over time by a varying amount.
The team applied these two models to three scenarios: Mars-sized moons orbiting Neptune-, Saturn-, and Jupiter-like planets. These three systems were always located in the center of the circumstellar habitable zone of a 0.7 solar-mass star. Here are the take-home messages:
1.) Mars-like exomoons beyond 20 planetary radii around any of the three host planets act like free planets around a star. They are well outside the habitable edge, experiencing no significant tidal heating or illumination. While their extreme distance is promising, they will never be enveloped within their host planet’s magnetosphere and are therefore unlikely to harbor life.
2.) Mars-like exomoons between 5 and 20 planetary radii face a range of possibilities. “Intriguingly, formation theory and observations of moons in the Solar System tell us that this is the range in which we should expect most exomoons to reside,” explains Dr. Heller.
For an exomoon beyond the habitable edge of a Neptune-like planet it may take more than the age of the Earth, that is, 4.6 billion years to become embedded within its host planet’s magnetosphere. For a Saturn-like planet it may take even longer, but for a Jupiter-like planet it will take less than 4.3 billion years.
3.) Mars-like exomoons inside 5 planetary radii are enveloped within the planetary magnetosphere early on but not habitable as they orbit within the planet’s habitable edge.
In order for an exomoon to be habitable it must exist well outside the habitable edge, safe from stellar and planetary illumination as well as tidal heating. But at the same time it must also exist near enough to its host planet to be embedded within the planet’s magnetosphere. The question of habitability depends on a delicate balance.
Dr. Zuluaga stressed that “one of the key consequences of this initial work is that although magnetic fields have been recognized as important factors determining the habitability of terrestrial planets across the Universe, including the Earth, Mars, and Venus, in the case of moons, the magnetic environment could be even more critical at defining the capacity of those worlds to harbor life.”
The paper has been accepted for publication in the Astrophysical Journal Letters and is available for download here.
