And if you’re interested in looking back, here’s an archive to all the past Carnivals of Space. If you’ve got a space-related blog, you should really join the carnival. Just email an entry to [email protected], and the next host will link to it. It will help get awareness out there about your writing, help you meet others in the space community – and community is what blogging is all about. And if you really want to help out, sign up to be a host. Send an email to the above address.
This colorized composite shows more than half of Earth’s disk over the coast of Argentina and the South Atlantic Ocean as the Juno probe slingshotted by on Oct. 9, 2013 for a gravity assisted acceleration to Jupiter. The mosaic was assembled from raw images taken by the Junocam imager. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
Juno Portrait of Earth
This false color composite shows more than half of Earth’s disk over the coast of Argentina and the South Atlantic Ocean as the Juno probe slingshotted by on Oct. 9, 2013 for a gravity assisted acceleration to Jupiter. The mosaic was assembled from raw images taken by the Junocam imager. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
See below a gallery of Earth from Juno[/caption]
During a crucial speed boosting slingshot maneuver around Earth on Oct. 9, NASA’s Jupiter-bound Juno probe snapped a dazzling gallery of portraits of our Home Planet over the South American coastline and the Atlantic Ocean. See our mosaics of land, sea and swirling clouds above and below, including several shown in false color.
But an unexpected glitch during the do or die swing-by sent the spacecraft into ‘safe mode’ and delayed the transmission of most of the raw imagery and other science observations while mission controllers worked hastily to analyze the problem and successfully restore Juno to full operation on Oct. 12 – but only temporarily!
Because less than 48 hours later, Juno tripped back into safe mode for a second time. Five days later engineers finally recouped Juno and it’s been smooth sailing ever since, the top scientist told Universe Today.
“Juno is now fully operational and on its way to Jupiter,” Juno principal investigator Scott Bolton told me today. Bolton is from the Southwest Research Institute (SwRI), San Antonio, Texas.
“We are completely out of safe mode!”
NASA’s Juno probe captured the image data for this composite picture during its Earth flyby on Oct. 9 over Argentina, South America and the southern Atlantic Ocean. Raw imagery was reconstructed and aligned by Ken Kremer and Marco Di Lorenzo, and false-color blue has been added to the view taken by a near-infrared filter that is typically used to detect methane. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
With the $1.1 Billion Juno probe completely healthy once again and the nail-biting drama past at last, engineers found the time to send the stored photos and research data back to ground station receivers.
“The science team is busy analyzing data from the Earth flyby,” Bolton informed me.
The amateur image processing team of Ken Kremer and Marco Di Lorenzo has stitched together several portraits from raw images captured as Juno sped over Argentina, South America and the South Atlantic Ocean and within 347 miles (560 kilometers) of the surface. We’ve collected the gallery here for all to enjoy.
Several portraits showing the swirling clouds and land masses of the Earth’s globe have already been kindly featured this week by Alan Boyle at NBC News and at the Daily Mail online.
NASA’s Juno probe captured the image data for this composite picture during its Earth flyby on Oct. 9 over Argentina, South America and the southern Atlantic Ocean. Raw imagery was stitched by Ken Kremer and Marco Di Lorenzo in this view taken by a near-infrared filter that is typically used to detect methane. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
Raw images from the Junocam camera are collected in strips – like a push broom. So they have to be carefully reconstructed and realigned to match up. But it can’t be perfect because the spacecraft is constantly rotating and its speeding past Earth at over 78,000 mph.
So the perspective of Earth’s surface features seen by Junocam is changing during the imaging.
And that’s what is fascinating – to see the sequential view of Earth’s beautiful surface changing as the spacecraft flew over the coast of South America and the South Atlantic towards Africa – from the dayside to the nightside.
This composite shows more than half of Earth’s disk over the coast of Argentina and the South Atlantic Ocean as the Juno probe slingshotted by on Oct. 9, 2013 for a gravity assisted acceleration to Jupiter. The mosaic was assembled from raw images taken by the Junocam imager. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
It’s rare to get such views since only a few spacecraft have swung by Earth in this manner – for example Galileo and MESSENGER – on their way to distant destinations.
Coincidentally this week, the Cygnus cargo carrier departed the ISS over South America.
Fortunately, the Juno team knew right from the start that the flyby of Earth did accomplish its primary goal of precisely targeting Juno towards Jupiter – to within 2 kilometers of the aim point, despite going into safe mode.
“We are on our way to Jupiter as planned,” Juno Project manager Rick Nybakken, told me in a phone interview soon after the flyby of Earth. Nybakken is from NASA’s Jet Propulsion Lab in Pasadena, CA.
“None of this affected our trajectory or the gravity assist maneuver – which is what the Earth flyby is,” he said.
Juno swoops over Argentina
This reconstructed day side image of Earth is one of the 1st snapshots transmitted back home by NASA’s Jupiter-bound Juno spacecraft during its speed boosting flyby on Oct. 9, 2013. It was taken by the probes Junocam imager and methane filter at 12:06:30 PDT and an exposure time of 3.2 milliseconds. Juno was flying over South America and the southern Atlantic Ocean. The coastline of Argentina is visible at top right. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer
It also accelerated the ships velocity by 16,330 mph (26,280 km/h) – thereby enabling Juno to be captured into polar orbit about Jupiter on July 4, 2016.
Dayside view of a sliver of Earth snapped by Juno during flyby on Oct. 9, 2013. This mosaic is stitched from raw image data captured by methane near-infrared filter on Junocam imager at 11:57:30 PDT. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
The safe mode did not impact the spacecraft’s trajectory one smidgeon!
It was likely initiated by an incorrect setting for a fault protection trigger for the spacecraft’s battery when Juno was briefly in an eclipse during the flyby.
Nybakken also said that the probe was “power positive and we have full command ability,” while it was in safe mode.
Safe mode is a designated fault protective state that is preprogrammed into spacecraft software in case something goes amiss. It also aims the craft sunwards thereby enabling the solar arrays to keep the vehicle powered.
False-color composite of a sliver of Earth snapped by Juno during flyby on Oct. 9, 2013. This mosaic is stitched from raw image data captured by methane near-infrared filter on Junocam imager at 11:57:30 PDT. Credit: NASA/JPL/SwRI/MSSS/Ken Kremer/Marco Di Lorenzo
The Earth flyby maneuver was necessary because the initial Atlas V rocket launch on Aug. 5, 2011 from Cape Canaveral Air Force Station, FL was not powerful enough to place Juno on a direct trajectory flight to Jupiter.
As of today, Juno is more than was 6.7 million miles (10.8 million kilometers) from Earth and 739 million miles (7.95 astronomical units) from Jupiter. It has traveled 1.01 billion miles (1.63 billion kilometers, or 10.9 AU) since launch.
With Juno now on course for our solar system’s largest planet, there won’t be no any new planetary images taken until it arrives at the Jovian system in 2016. Juno will then capture the first ever images of Jupiter’s north and south poles.
We have never seen Jupiter’s poles imaged from the prior space missions, and it’s not possible from Earth.
During a year long mission at Jupiter, Juno will use its nine science instruments to probe deep inside the planet to reveal its origin and evolution.
“Jupiter is the Rosetta Stone of our solar system,” says Bolton. “It is by far the oldest planet, contains more material than all the other planets, asteroids and comets combined and carries deep inside it the story of not only the solar system but of us. Juno is going there as our emissary — to interpret what Jupiter has to say.”
Based on what we’ve seen so far, Junocam is sure to provide spectacular views of the gas giants poles and cloud tops.
Where is the coldest place in the Universe? Right now, astronomers consider the “Boomerang Nebula” to have the honors. Located about 5,000 light-years away in the constellation Centaurus, this pre-planetary nebula carries a temperature of about one Kelvin – or a brisk, minus 458 degrees Fahrenheit. That makes it even colder than the natural background temperature of space! What makes it more frigid than the elusive afterglow of the Big Bang? Astronomers are employing the powers of the Atacama Large Millimeter/submillimeter Array (ALMA) telescope to tell us more about its chilly properties and unusual shape.
The “Boomerang” is different all the way around. It is not yet a planetary nebula. The fueling light source – the central star – just isn’t hot enough yet to emit the massive amounts of ultra-violet radiation which lights up the structure. Right now it is illuminated by starlight shining off its surrounding dust grains. When it was first observed in optical light by our terrestrial telescopes, the nebula appeared to be shifted to one side and that’s how it got its fanciful name. Subsequent observations with the Hubble Space Telescope revealed an hour-glass structure. Now, enter ALMA. With these new observations, we can see the Hubble images only show part of what’s happening and the dual lobes seen in the older data were probably only a “trick of the light” as presented by optical wavelengths.
“This ultra-cold object is extremely intriguing and we’re learning much more about its true nature with ALMA,” said Raghvendra Sahai, a researcher and principal scientist at NASA’s Jet Propulsion Laboratory in Pasadena, California, and lead author of a paper published in the Astrophysical Journal. “What seemed like a double lobe, or ‘boomerang’ shape, from Earth-based optical telescopes, is actually a much broader structure that is expanding rapidly into space.”
So what is going on out there that makes the Boomerang such a cool customer? It’s the outflow, baby. The central star is expanding at a frenzied pace and it is lowering its own temperature in the process. A prime example of this is an air conditioner. It uses expanding gas to create a colder core and as the breeze blows over it – or in this case, the expanding shell – the environment around it is cooled. Astronomers were able to determine just how cool the gas in the nebula is by noting how it absorbed the constant of the cosmic microwave background radiation: a perfect 2.8 degrees Kelvin (minus 455 degrees Fahrenheit).
Credit: NASA/ESA“When astronomers looked at this object in 2003 with Hubble, they saw a very classic ‘hourglass’ shape,” commented Sahai. “Many planetary nebulae have this same double-lobe appearance, which is the result of streams of high-speed gas being jettisoned from the star. The jets then excavate holes in a surrounding cloud of gas that was ejected by the star even earlier in its lifetime as a red giant.”
However, the single-dish millimeter wavelength telescopes didn’t see things the same as Hubble. Rather than a skinny waist, they found a fuller figure – a “nearly spherical outflow of material”. According to the news release, ALMA’s unprecedented resolution permitted researchers to determine why there was such a difference in overall appearance. The dual-lobe structure was evident when they focused on the distribution of carbon monoxide molecules as seen at millimeter wavelengths, but only toward the inside of the nebula. The outside was a different story, though. ALMA revealed a stretched, cold gas cloud that was relatively rounded. What’s more, the researchers also pinpointed a thick corridor of millimeter-sized dust grains enveloping the progenitor star – the reason the outer cloud took on the appearance of a bowtie in visible light! These dust grains shielded a portion of the star’s light, allowing just a glimpse in optical wavelengths coming from opposite ends of the cloud.
“This is important for the understanding of how stars die and become planetary nebulae,” said Sahai. “Using ALMA, we were quite literally and figuratively able to shed new light on the death throes of a Sun-like star.”
There’s even more to these new findings. Even though the perimeter of the nebula is beginning to warm up, it’s still just a bit colder than the cosmic microwave background. What could be responsible? Just ask Einstein. He called it the “photoelectric effect”.
So much space news, so little time. We had a great Weekly Space Hangout with several of our familiar space journalist friends. No huge stories, but lots of interesting tidbits, about asteroid protection, balloon trips to the edge of space, and the discovery of the furthest galaxy.
Host: Fraser Cain
Panel: Alan Boyle, Amy Shira Teitel, David Dickinson, Nancy Atkinson, Elizabeth Howell
We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.
Computer generated simulation of an asteroid strike on the Earth. Credit: Don Davis/AFP/Getty Images
“If we get hit 20 years from now, that’s not bad luck. That’s stupidity.”
That’s what former NASA astronaut Ed Lu has to say about asteroids and our efforts to search for them. He delivered those comments at a panel discussion today at New York’s American Museum of Natural History. He and several other astronauts spoke on behalf of the Association of Space Explorers (which, as the name implies, consists of astronauts, cosmonauts and the like.)
We guess that as astute readers of our publication, you know that a planetary threat from asteroids (and comets) exists. And there’s certainly more we can do; when that 17-meter asteroid blasted Russia earlier this year, Lu said most space agencies learned about it from social media!
So what’s being done about these threats? Here’s a roundup of the panel discussion’s information and some related information.
Asteroid searching and deflection:
Since Lu is the CEO of the B612 Foundation, there was a heavy emphasis on the agency’s proposed Sentinel telescope. Intended to launch in 2018, it would survey the solar system in infrared and seek out potential hazards.
To date, NASA’s NEO Observations Program has found 95 per cent of near-Earth objects larger than one kilometer, Jet Propulsion Laboratory scientist Amy Mainzer told Universe Today in a separate conversation today.
Mainzer also brought us up to speed on the Near-Earth Object Camera (NEOCam)proposal, which she’s been working on since 2005. Her group received technology development funding in 2010 to improve their infrared detectors, which succeeded in passing recent tests. Their group will seek more funding for NASA in the next opportunity.
TheWISE spacecraft’s NEOWISE mission, meanwhile, is going to restart early next year, Mainzer added. “While NEOWISE is not nearly as capable as NEOCam will be, it will improve our knowledge of the diameters and albedos of about 2,000 NEOs and tens of thousands of main belt asteroids,” Mainzer wrote. “With the NEOWISE prime mission, we discovered more than 34,000 new asteroids and observed >158,000 in total. We have used our data from NEOWISE to set constraints on the number of NEOs and potentially hazardous asteroids.”
Former NASA astronaut Tom Jones shared this slide concerning ideas for asteroid defense. Credit: Tom Jones/Association for Space Explorers/AMNH/Ustream (screenshot)
Getting the United Nations involved:
This week, the United Nations Committee on the Peaceful Uses of Outer Space adopted several steps related to asteroids. It’s planning an International Asteroid Warning Group (to share detections and warn of potential impacts), an Impact Disaster Planning Advisory Group, and a Space Missions Planning and Advisory Group (which would look at deflection missions, options, costs, etc.)
Why go with the United Nations? In the panel, NASA Apollo astronaut Rusty Schweickart explained it this way: deciding how to deflect an asteroid posts risks. You might be moving the impact path past a country that would not have been at risk before the deflection. It’s best to make such moves internationally, rather than having (say) the United States make a decision that could increase Russia’s risk to an asteroid.
The problem? Working by committee is slow, says former Romanian astronaut Dumitru-Dorin Prunariu: “You would think with the United Nations that we started to think about asteroids only in 2007, 8 or 9, but the first input was done by 1999 at the Unispace conference, the United Nations International Conference in Space.” People have been working hard, to be sure, but making a good, inclusive plan just takes time. An action team was formed in 2001, a working group was in place by 2007, and the adoptions by UNCOPUOS (as we stated earlier) took place this week.
An artist’s conception of a space exploration vehicle approaching an asteroid. Credit: NASA
Cost of all of this:
Schweickart: “Money is hardly an issue in this. This is a very inexpensive thing to do. It’s organizational setting the actual criteria, thresholds whatever.” It would only cost 1% of the NASA budget for the next 10 years, and less than 0.5% after that. (The NASA budget request for 2014 was $17.7 billion, so 1% of that is $177 million.)
The panel members emphasized that it’s best to start the search early and find the threatening asteroids before things become an emergency. If a moderate-sized asteroid was discovered only a few months out, it might be better just to evacuate the affected area rather than try to pull together a last-minute mission to stop the asteroid.
Planetary Scientist Sara Seager. Image courtesy MIT.
Astronomers have now discovered one thousand extrasolar planets, reaching a milestone in modern astronomy. (See a recent Universe Today article on the subject.) While many have contributed to this achievement, Dr. Sara Seager of MIT has played a large role over the past two decades by contributing vastly to the field of exoplanet characterization. Her theoretical work led to the first detection of an exoplanet atmosphere.
The following is a condensed interview I held with Seager earlier this week.
What first pulled you in to the field of astronomy?
When I was 10 I got to see a really dark sky (well outside her hometown of Toronto, Canada). I stepped out in the middle of the night and I just saw so many stars. I wish you and everyone could see that. So many stars, I just couldn’t believe it.
You were working at Harvard for your PhD in the mid ‘90s when we first detected exoplanets. What was that like?
The mood was quite different. Today everybody wants to talk about it (exoplanets) and write about it. There’s a lot of hype. But back then it was very quiet.
There was a huge amount of skepticism too. People don’t like change. I want you to imagine a world where the gas giants like Jupiter and Saturn are very far from the star and the terrestrial planets like Earth, Mercury, Venus, and Mars are very close to the star. People had constructed theories on how planetary bodies form based on that one example.
So when the first planets around sun-like stars were found, they were Jupiter-mass planets, but they were several times closer to their star than Mercury is to our Sun. It offended all thoughts, theories, and paradigms … As scientists we’re supposed to be skeptical and push back on new discoveries and theories that are upsetting the system. There was huge skepticism.
An exoplanet seen from its moon (artist’s impression). Via the IAU.
How difficult was it during this time to work on exoplanets?
Many people, including my graduate student peers and faculty said, “Why are you doing this (working on exoplanet research)? This is not going to happen. And even if exoplanets are real we’re never going to be able to study their atmospheres,” which is what my PhD was on.
What pushed you through despite all the skepticism?
Ironically, I was not committed to a career in science. I didn’t feel like I needed to be involved with something that was at the 100 percent certainty level. I was free because I didn’t have a plan. I had nothing to lose by doing something I thought was really cool and exciting.
When you’re doing a PhD you’re really learning how to answer a tough question. Usually if you do a homework set in high school, or college, there’s already a known answer. But when you’re doing a PhD, if you’re asking a really hard question that has never been asked before you’re answering that question with your own tools that you’ve developed yourself.
At that time, I knew… the real thing is not just what you’re working on but it’s the tools that you’re using and the things that you’re learning. At the end of the day if you don’t stay in science you have gained a skill that most people don’t have.
Artist concept of an exoplanet. Credit: David A. Hardy. What changed then? What kept you in science after graduate school?
I had freedom and really enjoyed what I was doing.
What is your motivation for studying exoplanets? Why should we study exoplanets?
We want to know: Are we alone? We want to know if there is life beyond earth. Eventually we will have dozens to hundreds of potential earth-like planets to study in detail. We want to look at their atmospheres for signs of life by way of biosignature gases.
What do you think is the likelihood that we will discover an earth-like planet orbiting a sun-like star?
Well, it really just depends if we can rally resources and interest in doing this problem. We think we know how to find an earth-like planet around a sun-like star. But it’s a very very very hard endeavor. We think that the earths are out there. It’s just a matter of building the sophisticated space telescopes that we need.
So what are the chances? It’s really more of a political and economical question more than anything else. I think it’s inevitable that eventually we will find one.
Do you have a favorite planet?
I always like to say my favorite planet is the next planet. We have a sort of ADD (attention deficit disorder) in this field where we’re propelled and motivated forward by finding the next exciting planet. Artist’s impression of exoplanets around other stars. Credits: ESA/AOES Medialab We’ve reached a huge milestone in astronomy of detecting one thousand exoplanets. What does this milestone mean to you?
There’s a caveat here, an uncertainty. We don’t know which one is going to be number one thousand because we don’t agree on the definition of a planet. And even if we did, there’s an uncertainty in the mass and size measurements such that some objects that are called planets probably aren’t planets depending on what definition you want. Occasionally a planet is retracted.
But in general, we’re about to pass the one thousandth mark. What do I think? I think it’s phenomenal. I mean I’m so excited.
The study of exoplanets really started as a field where no one wanted to work on it. People thought it was never going to happen, they thought even if there were real planets we’d never get any measurements beyond stamp collecting – a derogatory phrase we sometimes use in astronomy for science that is not that useful. You just find discoveries and they pile up because you don’t know what to do with them.
We’ve changed the paradigm of planet formation, found exotic types of planets, and we’re right on our way to finding another Earth. So I think it couldn’t be better.
We know that hundreds of thousands of asteroids orbit the Sun, and a very few have a high risk of striking Earth. There are also asteroids that haven’t been discovered yet that can surprise us, as evidenced by the explosion over Chelyabinsk, Russia, last February. This event was confirmation that an asteroid strike is a risk we do face. But also, how do scientists counter the pseudo-scientific claims and fears that asteroids seem to generate? And what opportunities do asteroids provide for mining useful resources?
Watch live today (Friday, October 25, 2013) at 15:00 UTC (11 am EDT) as astrophysicist Neil deGrasse Tyson, astronauts Rusty Schweickart, Tom Jones, Ed Lu, Soichi Noguchi and others discuss the research and the steps that are being taken to avoid these potential natural disasters. With current space technology, scientists know how to deflect the majority of hazardous near-Earth objects, but these technologies have not yet been tested in space, and prevention is only possible if nations work together on detection and deflection.
NASA astronauts Mike Hopkins and Karen Nyberg (edge of picture, at left) examine a faulty spacesuit aboard the International Space Station during Expedition 37 in October 2013. In July 2013, Italian astronaut Luca Parmitano had to abort a spacewalk after a water leak arose while wearing the spacesuit. The cause is still under investigation. Credit: NASA/YouTube (screenshot)
Here’s the latest attempt to hunt down the water leak that aborted Luca Parmitano’s spacewalk in July: two astronauts aboard the International Space Station removed and replaced a fan pump and water separator inside the spacesuit earlier this week.
All spacewalks with NASA suits are on hold while the agency investigates the leak, and they have been trying mightily. In late July, then on-station NASA astronaut Chris Cassidy demonstrated how the pool of water spread within the helmet (as you can see in these YouTube videos).
This week, on-orbit NASA astronauts Mike Hopkins and Karen Nyberg delved further. While the astronauts are trained before their missions on some suit repairs, this particular type was not something that was covered before they left Earth. After Mission Control walked them through what to do, the astronauts proceeded cautiously as they did the work, NASA said.
“Our engineering teams have identified several different components of the suit, designing a big fault tree, and this is just one of the components that we think could have contributed to the leak in the suit,” said Alex Kanelakos, an extra-vehicular activity flight controller and astronaut instructor, in a new YouTube video.
“Specifically, the water separator is what we’re concentrating our efforts on today.”
As Kanelakos explained, a motor inside the suit drives the fan pump and water separator. The fan circulates oxygen, and the pump pumps the coolant fluid. The water separator, meanwhile, takes out moisture (water) from the ventilation loop and gas that could be trapped inside the water coolant loop. The dried-out air is then returned to the crew member for breathing, and the cycle continues.
Astronaut Chris Cassidy works with Luca Parmitano’s spacesuit, which had a water leak on July 16, 2013. Credit: NASA
In September, Cassidy told Universe Today that the spacesuit is expected to come back to Earth during a future SpaceX Dragon cargo flight. That type of spacecraft is (unusually among space trucks) designed to survive re-entry in the atmosphere, allowing engineers on the ground to examine the spacesuit after it comes back.
Cassidy added that the situation was serious, and he supported NASA’s decision to end the spacewalk (which he was also participating in.) He didn’t think, however, that Parmitano was in immediate danger of drowning. For his part, Parmitano wrote a blog post on the European Space Agency website after his spacewalk, saying that space is an “inhospitable” arena.
Italian astronaut Luca Parmitano during a spacesuit fit check before his mission. Credit: NASA
As any astronaut is trained to do, Parmitano did consider other contingencies while the leak was happening, he wrote:
“The only idea I can think of is to open the safety valve by my left ear: if I create controlled depressurisation, I should manage to let out some of the water, at least until it freezes through sublimation, which would stop the flow. But making a ‘hole’ in my spacesuit really would be a last resort,” he wrote.
That fix, however, was not implemented as Parmitano and Cassidy made their way back to the station in time for their crewmates to repressurize the hatch and bring their Italian crewmate safely inside.
Recent images of Comet ISON along with spectral data. Credit and copyright: Chris Schur.
Undoubtedly, you’ve been seeing the recent images of Comet ISON now that it is approaching its close encounter with the Sun on November 28. ISON is currently visible to space telescopes like the Hubble and amateur astronomers with larger telescopes. But you might be wondering why many images show the comet with a green-ish “teal” or blue-green color.
Amateur Astronomer Chris Schur has put together this great graphic which provides information on the spectra of what elements are present in the comet’s coma.
For the conspiracy theorists out there, the green color is actually a good omen, and lots of comets display this color. The green color is a sign the comet is getting more active as gets closer to the Sun – meaning it is now putting on a good show for astronomers, and if it can continue to hold itself together, it might become one of the brightest comets in the past several years.
“ISON’s green color comes from the gases surrounding its icy nucleus,” says SpaceWeather.com’s Tony Phillips. “Jets spewing from the comet’s core probably contain cyanogen (CN: a poisonous gas found in many comets) and diatomic carbon (C2). Both substances glow green when illuminated by sunlight in the near-vacuum of space.”
Comet ISON on October 4, 2013 as seen over Arizona, viewed with a 12.5″ telescope, over an hour exposure time. Credit and copyright: Chris Schur.
Both are normally colorless gases that fluoresce a green color when excited by energetic ultraviolet light in sunlight.
And if those poisonous gasses sound dangerous, don’t worry. They are spread out in space much too thinly to touch us here on Earth. So don’t fall prey to fear mongers who are out to bilk the masses – like people did in 1910 when Comet Halley made a return to the skies and swindlers pitched their ‘gas masks’ and special ‘comet pills’ for protection. And of course, nothing happened.
But back to the color. Chris Schur provided this info along with his graphic:
Your readers may appreciate knowing why comets can appear this color. The background image is the shot I took with my 12.5″ and an ST10xme CCD camera for 20 minutes in mid-October. A pale coloration of the front of the coma is seen. To the lower left is a shot with the same instrument but with a 100 lpmm (line pair per millimeter) diffraction grating in front of the CCD chip to break out the spectra of the objects in the entire field.
Here ISON is faintly seen to the left of center, and the first order spectra a band to its right. But the real answer comes when we use the software called Rspec to analyze this band of light. The result is on the lower right. Normally reflected sunlight is rather flat and bland, and mostly that is what ISON is right now, reflected from dust. But labeled are two humps in the blue and green parts of the spectrum labeled “C2” for a carbon molecule. This blue/green emission pair is what gives ISON the color.
Chris notes that as the comet nears the Sun, astronomers and astrophotographers will be able to resolve more spectral details in the comet. “It will be exciting to watch the changes as more molecules pop out,” Chris said via email, “and possibly when it is closest to the Sun, we just may see some metal lines like iron or magnesium from MELTED vaporized rock. How exciting!”
And for those who insist there is something nefarious about Comet ISON, take a look at this FAQ from our friend Stuart Atkinson, who hosts the great site Waiting for ISON. He addresses the many conspiracy theories that are out there regarding this comet.
X-ray emissions from the supermassive black hole in the center of the Milky Way galazy, about 26,000 light years from Earth. Credit: NASA/CXC/APC/Université Paris Diderot/M.Clavel et al
How’s that for a beacon? NASA’s Chandra X-ray Observatory has tracked down evidence of at least a couple of past luminous outbursts near the Milky Way’s huge black hole. These flare-ups took place sometime in the past few hundred years, which is very recently in astronomical terms.
“The echoes from Sagittarius A were likely produced when large clumps of material, possibly from a disrupted star or planet, fell into the black hole,” the Chandra website stated.
“Some of the X-rays produced by these episodes then bounced off gas clouds about 30 to 100 light years away from the black hole, similar to how the sound from a person’s voice can bounce off canyon walls. Just as echoes of sound reverberate long after the original noise was created, so too do light echoes in space replay the original event.”
The astronomers saw evidence of “rapid variations” in how X-rays are emitted from gas clouds circling the hole, revealing clues that the area likely got a million times brighter at times.
