What do you get when you combine 15 radio telescopes on Earth and one in space? You get an enormous “virtual telescope” that is 63,000 miles across. And when you point it at a distant black hole, you get the highest resolution image every seen in astronomy.
Although it looks just like a big green blob, it’s actually an enormously energetic jet of matter streaming out of a black hole. And this black hole is 900 million light years away.
As reported at Popular Science, it required an array of 15 radio telescopes on Earth, and the Russian space telescope Spektr-R, to capture the image. This technique—called interferometry—is like creating a telescope that is 63,000 miles across. The detail it provides is like seeing a 50 cent coin on the Moon.
For perspective, the object in the image is 186 billion miles long, at minimum, and would just barely fit in the Oort Cloud.
The jet at the heart of BL Lacertae, with the Oort Cloud and Alpha Centauri for comparison. Image: Gomez et. al., A Lobanov, NRAO.
China has released hundreds of images of the Moon, taken by its Chang’e 3 lander and its companion rover, Yutu. It’s been 50 years since the first lunar photos were taken by astronauts on NASA’s Apollo 11 mission. China is the third nation to land on the Moon, with the USA and the USSR preceding them.
Even though the Yutu rover’s engine failed after a short time on the lunar surface, the mission’s camera systems have captured hundreds of images.
Thanks to the hard work of Emily Lakdawalla at The Planetary Society, who wrestled with a somewhat cumbersome Chinese website, and stitched some of these images together, we can get a first-hand look at what Chang’e 3 and Yutu were up to.
Here are some of our favourites.
Pyramid Rock, as named by the Chinese. This rock was ejected when the crater immediately behind it was created. Image: Chinese Academy of Sciences/China National Space Administration/The Science and Application Centre for Moon and Deep Space Exploration/Emily Lakdawalla.
This is a 360 degree panoramic image of the rover and part of the lander. Bright white rocks litter the rim of the crater on the left. Image: Chinese Academy of Sciences/China National Space Administration/The Science and Application Centre for Moon and Deep Space Exploration/Emily Lakdawalla.The Yutu lander looks at its tracks in the lunar soil. Image: Chinese Academy of Sciences/China National Space Administration/The Science and Application Centre for Moon and Deep Space Exploration/Emily Lakdawalla.This image shows a lot of detail of the Yutu rover. Image: Chinese Academy of Sciences/China National Space Administration/The Science and Application Centre for Moon and Deep Space Exploration/Emily Lakdawalla.
Emily Lakdawalla talks more about the camera systems here, and talks about what other images might be coming soon.
Universe Today reported on the Chinese Moon mission here.
The Moon is the first object in space that fascinates we Earthlings. The Sun might be more prominent, but you can’t stare at the Sun without ocular damage. Anyone can gaze at the Moon, with or without binoculars or a telescope, and wonder where it came from and what it all means.
New evidence from a team at UCLA is clarifying the story of the Moon’s origins. According to this research, the Moon was formed as a result of a massive collision between Earth and a “planet embryo” about the size of Mars called Theia. This collision happened about 100 million years after the Earth was formed. Published on January 29th in the journal Science, this new geological evidence strengthens the case for the collision model.
The researchers compared Earth rocks with rocks retrieved from the Moon over the years. (Over 380kg of rocks have been brought back to Earth.) They found that these samples—collected on Apollo missions 12, 15, and 17—had the same chemical composition as seven rocks collected from Earth’s mantle, in Hawaii and Arizona. The key to the comparison lies in the nature of the oxygen atoms in the rocks.
Oxygen is a highly reactive element. It is easily combined with other elements, and is the most common element in the Earth’s crust. There are several different oxygen isotopes present in the Earth’s crust, and on other bodies in the solar system. The amount of each isotope present on each body is the “fingerprint” that makes the formation of each body different.
But the team at UCLA has shown that Earth and the Moon share the same cocktail of oxygen isotopes. They have the same fingerprint. This means that somehow, someway, their formation is linked. It can’t be pure coincidence. Says Edward Young, lead author of the new study, “We don’t see any difference between the Earth’s and the Moon’s oxygen isotopes; they’re indistinguishable.”
So how did this happen? How do Earth and the Moon share the same oxygen fingerprint? Enter Theia, an embryonic planet that got in the way of Earth’s orbit around the Sun. And as the research shows, this collision had to be more than a glancing blow. The collision had to be direct and cataclysmic.
This video shows how the collision would have played out.
A glancing blow would mean that the Moon would be mostly made of Theia, and would therefore have a different oxygen isotope fingerprint than Earth. But the fact that the Earth and Moon are indistinguishable from each other means that Theia had to have been destroyed, or rather, had to become part of both the Earth and the Moon.
“Theia was thoroughly mixed into the Earth and the Moon, and evenly dispersed between them. This explains why we don’t see a different signature of Theia in the Moon versus Earth,” said Young.
If this collision had not taken place, our Solar System would look very different, with an additional rocky planet in the inner regions. We also would have no Moon, which would have changed the evolution of life on Earth.
This collision theory, called the Theia Impact, or the Big Splash, has been around since 2012. But in 2014, a team of German researchers reported in Science that the Earth and Moon have different oxygen isotope ratios, which threw the collision formation theory into doubt. These new results confirm that it was a cataclysmic collision that gave birth to the Moon, and changed our Solar System forever.
The Ariane 5 rocket is a workhorse for delivering satellites and other payloads into orbit, but fitting the James Webb Space Telescope (JWST) inside one is pushing the boundaries of the Ariane 5’s capabilities, and advancing our design of space observatories at the same time.
The Ariane 5 is the most modern design in the ESA’s Ariane rocket series. It’s responsible for delivering things like Rosetta, the Herschel Space Observatory, and the Planck Observatory into space. The ESA is supplying an Ariane 5 to the JWST mission, and with the planned launch date for that mission less than three years away, it’s a good time to check in with the Ariane 5 and the JWST.
The Ariane 5 has a long track record of success, often carrying multiple satellites into orbit in a single launch. Here’s its most recent launch, on January 27th from the ESA’s spaceport in French Guiana. This is Ariane 5’s 70th successful launch in a row.
But launching satellites into orbit, though still an amazing achievement, is becoming old hat for rockets. 70 successful launches in a row tells us that. The Ariane 5 can even launch multiple satellites in one mission. But launching the James Webb will be Ariane’s biggest challenge.
The thing about satellites is, they’re actually getting smaller, in many cases. But the JWST is huge, at least in terms of dimensions. The mass of the JWST—6,500 kg (14,300 lb)—is just within the limits of the Ariane 5. The real trick was designing and building the JWST so that it could fit into the cylindrical space atop an Ariane 5, and then “unfold” into its final shape after separation from the rocket. This video shows how the JWST will deploy itself.
The JWST is like a big, weird looking beetle. Its gold-coated, segmented mirror system looks like multi-faceted insect eyes. Its tennis-court sized heat shield is like an insect’s shell. Or something. Cramming all those pieces, folded up, into the nose of the Ariane 5 rocket is a real challenge.
Because the JWST will live out its 10-year (hopefully) mission at L2, rather than in orbit around Earth, it requires this huge shield to protect itself from the sun. The instruments on the James Webb have to be kept cool in order to function properly. The only way to achieve this is to have its heat shield folded up inside the rocket for launch, then unfolded later. That’s a very tricky maneuver.
But there’s more.
The heart of the James Webb is its segmented mirror system. This group of 18 gold-coated, beryllium mirrors also has to be folded up to fit into the Ariane 5, and then unfolded once it’s separated from the rocket. This is a lot trickier than launching things like the Hubble, which was deployed from the space shuttle.
Something else makes all this folding and unfolding very tricky. The Hubble, which was James Webb’s predecessor, is in orbit around Earth. That means that astronauts on Shuttle missions have been able to repair and service the Hubble. But the James Webb will be way out there at L2, so it can’t be serviced in any way. We have one chance to get it right.
Right now, the James Webb is still under construction in the “Clean Room” at NASA’s Goddard Space Flight Centre. A precision robotic arm system is carefully mounting Webb’s 18 mirrors.
A robotic arm positions one of James Webb’s 18 mirrors. Image: NASA/Chris Gunn
There’s still over two years until the October 2018 launch date, and there’s a lot of testing and assembly work going on until then. We’ll be paying close attention not only to see if the launch goes as planned, but also to see if the James Webb—the weird looking beetle—can successfully complete its metamorphosis.
Saturn’s Rings are amazing to behold. Since they were first observed by Galileo in 1610, they have been the subject of endless scientific interest and popular fascination. Composed of billions of particles of dust and ice, these rings span a distance of about 282,000 km (175,000 miles) – which is three quarters of the distance between the Earth and its Moon – and hold roughly 30 quintillion kilograms (that’s 3.0. x 1018 kg) worth of matter.
All of the Solar System’s gas giants, from Jupiter to Neptune, have their own ring system – albeit less visible and picturesque ones. Sadly, none of the terrestrial planets (i.e. Mercury, Venus, Earth and Mars) have such a system. But just what would it look like if Earth did? Putting aside the physical requirements that it would take for a ring system to exist, what would it be like to look up from Earth and see beautiful rings reaching overhead?
Amateur astronomer Chris Schur of Arizona had only five minutes to observe and photograph Comet Catalina this morning before twilight got the better of the night. In that brief time, he secured two beautiful images and made a quick observation through his 80mm refractor. He writes:
“Very difficult observation on this one. (I observed) it visually with the 35mm Panoptic ocular. It was a round, slightly condensed object with no sign of the twin tails that show up in the images. After five minutes, we lost it visually as it was 2° degrees up in bright twilight. Images show it for a longer time and a beautiful emerald green head with two tails forming a Y shaped fan.”
Comet Catalina stands some 3° high over Lake Superior near Duluth, Minn. (U.S.) at 5:55 a.m. this morning, Nov. 22. Stars are labeled with their magnitudes. Details: 200mm lens, f/2.8, ISO 1250, 3-seconds. Credit: Bob King
Schur estimated the comet’s brightness at around magnitude +6. What appears to be the dust tail extends to the lower right (southeast) with a narrower ion tail pointing north. With its twin tails, I’m reminded of a soaring eagle or perhaps a turkey vulture rocking back and forth on its wings. While they scavenge for food, Catalina soaks up sunlight.
I also headed out before dawn for a look. After a failed attempt to spot the new visitor on Saturday, I headed down to the Lake Superior shoreline at 5:30 a.m. today and waited until the comet rose above the murk. Using 7×50 binoculars in a similar narrow observing window, I could barely detect it as a small, fuzzy spot 2.5° south of 4th magnitude Lambda Virginis at 5:50 a.m. 10 minutes after the start of astronomical twilight. The camera did better!
Chris’s first photo was taken when the comet rose. This one was photographed minutes later with twilight coming on. Credit: Chris Schur
With the comet climbing about 1° per day, seeing conditions and viewing time will continue to improve. The key to seeing it is finding a location with an unobstructed view to the southeast — that’s why I chose the lake — and getting out while it’s still dark to allow time to identify the star field and be ready when the comet rises to greet your gaze.
North is up and east to the left in these two photos of the comet made by Dr. D.T. Durig at 6:23 a.m. EST on Nov. 21st from Cordell-Lorenz Observatoryin Sewanee, Tenn. He estimated the coma diameter at ~2 arc minutes with a tail at least 10 arc minutes long . “I get a nuclear magnitude of 10.3 and an total mag of around 7.8, but that is with only 5-10 reference stars,” wrote Durig. Credit: Dr. Douglas T. Durig
Alan Hale, discoverer of Comet Hale-Bopp,also tracked down Catalina this morning with an 8-inch (20-cm) reflector at 47x. He reported its magnitude at ~+6.1 with a 2-arc-minute, well-condensed coma and a faint wisp of tail to the southeast. In an e-mail this morning, Hale commented on the apparent odd angle of the dust tail:
“Since the comet is on the far side of the sun as seen from Earth, with the typical dust tail lagging behind, that would seem to create the somewhat strange direction. It (the tail) almost seems to be directed toward the Sun, but it’s a perspective effect.”
Venus glares inside the cone of the zodiacal light this morning at the start of astronomical twilight. Jupiter is seen at top and Mars two-thirds of the way from Jupiter to Venus. Arcturus shines at far left. Credit: Bob King
There were side benefits to getting up early today. Three bright planets lit up Leo’s tail and Virgo’s “Cup” and a magnificent display of zodiacal light rose from the lake to encompass not only the comet but all the planets as well.
Get ready for a man-made fireball. A object discovered by the Catalina Sky Survey on Oct 3rd temporarily designated WT1190F is predicted to impact the Earth about 60 miles (100 km) off the southern coast of Sri Lanka around 6:20 Universal Time (12:20 a.m CST) on November 13.
The object orbits Earth with a period of about three weeks. Because it was also observed twice in 2013 by the same survey team, astronomers have the data they need to model its orbit and trajectory, and as far anyone can tell, it’s likely man-made.
The first two stages of the Saturn V rockets used to send the seven Apollo missions to the Moon fell back to Earth, but the third stage (S-IVB), pictured here, propelled the spacecraft into a lunar trajectory. Could this be WT1190F? Credit: NASA
Solar radiation pressure, the physical “push” exerted by photons of sunlight, is proportional to a space object’s area-to-mass ratio. Small, lightweight objects get pushed around more easily than heavier, denser ones. Taking that factor into account in examining WT1190F’s motion over two years, the survey team has indirectly measured WT1190F’s density at about 10% that of water. This is too low to be a typical asteroid made of rock, but a good fit with a hollow shell, possibly the upper stage of a rocket.
Spectacular re-entry of the Jules Verne ATV-1 cargo ship over the Pacific Ocean on September 29, 2008. Still image from a TV camera operated by Jessie Carpenter and Bill Moede of NASA Ames Research Center. A similar spectacle is expected on November 13 south of Sri Lanka.
It’s also quite small, at most only about six feet or a couple of meters in diameter. Most or all of it is likely to burn up upon re-entry, creating a spectacular show for anyone near the scene. During the next week and a half, the European Space Agency’s NEO (Near-Earth Object) Coordination Centeris organizing observing campaigns to collect as much data as possible on the object, according to a posting on their website. The agency has two goals: to better understand satellite re-entries from high orbits and to use the opportunity to test our readiness for a possible future event involving a real asteroid. The latter happened once before when 2008 TC3(a real asteroid) was spotted on October 6, 2008 and predicted to strike Earth the very next day. Incredibly, it did and peppered the Sudan with meteorites that were later recovered.
Assuming WT1190F is artificial, its trans-lunar orbit (orbit that carries it beyond the Moon) hints at several possibilities. Third stages from the Saturn-V rockets that launched the Apollo missions to the Moon are still out there. It could also be a stage from one of the old Russian or more recent Chinese lunar missions. Even rockets used to give interplanetary probes a final push are game.
Near-Earth object J002E3 discovery images taken by Bill Yeung on September 3, 2002. The 16th magnitude object was tentatively identified as the Apollo 12 third stage rocket. Animation created by Bob Denny.
Case in point. What was thought initially to be a new asteroid discovered by amateur astronomer Bill Yeung on September 3, 2002 proved a much better fit with an Apollo 12 S-IVB (third) stage after University of Arizona astronomers found that spectra taken of the object strongly correlated with absorption features seen in a combination of man-made materials including white paint, black paint, and aluminum, all consistent with Saturn V rockets.
On April 14th 1970, the Apollo 13 Saturn IVB upper stage impacted the moon north of Mare Cognitum. The impact crater, which is roughly 30 meters in diameter, is clearly visible in this photo taken by the Lunar Reconnaissance Orbiter. Credit: NASA/Goddard/Arizona State University
Apollo 13’s booster was the first deliberately crashed into the Moon, where it blew out it a crisp, 98-foot-wide (30-meter) crater. Why do such a crazy thing? What better way to test the seismometers left by the Apollo 12 crew? All subsequent boosters ended their lives similarly in the name of seismography. Third stages from earlier missions — Apollos 8, 10 and 11 — entered orbit around the Sun, while Apollo 12, which is orbiting Earth, briefly masqueraded as asteroid J002E3.
The nominal impact point is located about 60 miles south of the island nation Sri Lanka. Given the object’s small size and mass, it will likely be completely incinerated during re-entry. Credit: Bill Gray at Project Pluto
Bill Gray at Project Pluto has a page up about the November 13 impact of WT1190F with more information. Satellite and asteroid watchers are hoping to track the object before and right up until it burns up in the atmosphere. Currently, it’s extremely faint and moving eastward in Orion. You can click HERE for an ephemeris giving its position at the JPL Horizons site. How exciting if we could see whatever’s coming down before its demise on Friday the 13th!
Trick or treat! I think we’re definitely in for a treat. 2015 TB145 will fly past Earth at a safe distance slightly farther than the moon’s orbit on Oct. 31 at 12:05 p.m. CDT (17:05 UT). Estimated at 1,300 feet (400-meters) across, this Great Pumpkin of an asteroid will be big enough and close enough to show in small telescopes.
Do I hear the doorbell ringing already?
Shining faintly at 18th magnitude on October 22, 2015 TB145 is already under study by amateur and professional astronomers. Its close approach will make for an excellent opportunity to learn a great deal about its surface properties and orbit. Watch for it to brighten up to magnitude +10.1 at peak, bright enough to see in a 4.5-inch telescope. Credit: Gianluca Masi
The close approach of such of TB145 will make for great science opportunities, too. Several optical observatories and the radar capabilities of the agency’s Deep Space Network at Goldstone, California will be tracking this flying mountain as will many amateur astronomers. The 110-foot (34-meter) Goldstone antenna will ping the asteroid with radio waves; the returning echoes will be collected by dishes in West Virginia and Puerto Rico and used to construct images showing the object’s surface features, shape and dimensions. NASA scientists hope to obtain radar images of the asteroid as fine as about 7 feet (2 meters) per pixel.
“The close approach of 2015 TB145 at about 1.3 times the distance of the moon’s orbit, coupled with its size, suggests it will be one of the best asteroids for radar imaging we’ll see for several years,” said Lance Benner, of JPL, who leads NASA’s asteroid radar research program. “We plan to test a new capability to obtain radar images with two-meter resolution for the first time and hope to see unprecedented levels of detail.”
View of the orbit of asteroid 2015 TB145. Its orbit is inclined about 39° to the plane of the Solar System. Credit: P. Chodas (NASA/JPL – Caltech)
Astronomers first nabbed asteroid 2015 TB145 on Oct. 10, 2015, using the University of Hawaii’s Pan-STARRS-1 (Panoramic Survey Telescope and Rapid Response System) telescope atop Mt. Haleakala in Maui. According to the catalog of near-Earth objectskept by the Minor Planet Center, this is the closest currently known approach by an object this large until asteroid 1999 AN10 (about 2,600 feet or 800-m in size) zips by at about 1 lunar distance in August 2027.
The gravitational influence of the asteroid is so small it will have no detectable effect on the Moon or anything here on Earth, including our planet’s tides or tectonic plates. But the planet will certainly have an effect on the asteroid. Earth’s gravity will deflect TB145’s path during the close approach, making it tricky this far out to create an accurate map of its flight across the sky. That’s why the two maps I’ve included with this article are only approximate. As we get closer to Halloween, further refinements in the asteroid’s orbit will allow for more accurate path-making.
TB145’s path starting at 4 hours UT on Oct. 31 (11 p.m. CDT Oct. 30). This view faces east. Tick marks show its hourly position. At the start of the path, the asteroid will shine around magnitude 11.4 but will gradually brighten through the night. To convert from UT, subtract 4 hours for EDT, 5 for CDT, 6 for MDT and 7 for PDT. Click for a large version. Credit: Chris Marriott’s SkyMap
Because the asteroid passes so near Earth, parallax will shift its path north or south up to 1/2°. Parallax is the apparent shift in an object’s position against the more distant background stars depending on the observer’s location on Earth. You can see how parallax works using your eyes and a finger. Stick your arm straight out in front of you and hold up your index finger. Open and close your right and then your left eye in a back and forth blinking pattern and watch your finger jump back and forth across the more distant background. Each eye sees the thumb from a slightly different perspective, causing it to shift position against the distant scene.
Graphic depicting the orbit of asteroid 2015 TB145. The asteroid will safely fly past Earth slightly farther out than the moon’s orbit on Halloween. Credit: P. Chodas (NASA/JPL – Caltech)
This happens all the time with the Moon. You might see it conjunct with a bright planet where skywatchers on the opposite side of the planet see an occultation. That’s why it’s best to make your own map of TB145’s wild ride across the sky. When closest to Earth, the asteroid will cover a Full Moon diameter about every 3 minutes as it tears by us at 22 miles per second (35 km/sec). Without a good map, it’ll get away from you.
Method #1: Using Stellarium
Download the free sky-plotting program Stellarium. Once you’ve set your location, either hit F2 or click on the Configuration icon in the lower left corner of your screen. Now select the Plugins tab then Solar System Editor. Click on Configure at the bottom of the tab, choose Solar System and click Import orbital elements in MPC format.
Next, select the Asteroids option and then from the bookmarks list, choose MPCORB: near-Earth asteroids (NEAs) and then Get orbital elements. Allow the list — a very large one — to load then scroll through it until you find 2015 TD145 and put a check mark in the box. Then click Add objects.
Stellarium view of the sky and featured asteroid seen from northern, Minnesota at 11:55 p.m. October 30, 2015. Notice that a bright, waning gibbous Moon will be nearby during the best viewing opportunities for the Americas, which will make 2015 TB145 a little harder to spot.
Still with me? OK, close the Solar System editor and press F3 or select the magnifying glass icon in the lower left corner of your screen, then type in the asteroid’s name exactly as 2015 TD145. Hit enter and you’ll see a set of rotating red crosshairs. Bingo! This where the asteroid will be at the time you chose. You can adjust your magnitude range, field of view and even download additional files of fainter stars and deep sky objects. Unfortunately, Stellarium can’t draw an arc showing TB145’s changing position with time. Cross your fingers that appears in the next iteration.
Method #2: Download up-to-date orbital elements into your sky-charting program
2015 TB145 belongs to the Apollo family of asteroids, whose orbits cross that of Earth. Amor asteroids approach but don’t cross, while Atens also cross Earth’s path but spend most of their time inside our orbit. Credit: ESA
Let’s say you already have a sky-charting program like Guide, Dance of the Planets, MegaStar or Starry Night. Go to the Minor Planet &Comet Ephemeris Serviceand type in 2015 TB145 in the big, blank box. Next, scroll down and select your program from the list and click on Get Ephemerides/HTML page. Save the file of orbital elements that pops up and place into the appropriate folder in your program. Open your program, select 2015 TB145 and make a chart!
Method #3: Manually input orbital elements into your program
You can also go to JPL’s Horizons site for the very latest orbital elements you can manually input in your program. 2015 TB145 is expected to be as bright as magnitude +10.1 (no problem in a 4.5-inch scope) but that occurs during the afternoon for the Americas. The Middle East and Asia are the place to be for closest approach. Peak brightness over the U.S. will occur before dawn on Halloween, so you can begin observation around 11 p.m. local time Friday evening October 30 when Orion comes up in the east. The asteroid starts shines at around magnitude +11-11.5 that evening and brightens overnight to around +10.3-10.5 before dawn for the Americas.
A word about tracking fast-moving asteroids. I’ve found that the best way to catch sight of one is to “camp” at the place they’ll pass at a certain time. Say you want to see TB145 at 1:15 a.m. October 31. Make a chart that shows its position every 15 minutes. Five minutes before it arrives at the 1:15 a.m. spot, point your telescope there and wait for a “moving star” to enter the field of view. If you don’t see it right way, wait a few minutes and pan around to the north and south of the location. By the way, the asteroid will pass less than a degree northwest of the Crab Nebula (M1) in Taurus around 10:30 UT (5:30 a.m. CDT).
Be aware that the bright, waning gibbous Moon will be within 10° of the asteroid when it’s best visible in the Americas. While this will make observing the asteroid more challenging, don’t let it stop you from trying. If bad weather gets in the way, Gianluca Masi has you covered. He’ll live-stream the flyby on his Virtual Telescope sitebeginning at 0:00 UT (7 p.m CDT) on October 31st.
One way or another, we’ll all have a shot at seeing the Great Pumpkin asteroid this Halloween.
2015 TB145 looks stellar in this photo taken on October 24th when it glowed at only 16th magnitude. Credit: Peter Lake
UPDATE Oct. 27, 2015: There’s been some discussion about TB145’s orbit resembling that of a comet along with speculation it might be a dead or dormant comet. Amateur and professional astronomers have been watching it closely, looking for hints of activity such as a fuzzy coma. So far, photos show the asteroid as completely stellar.
I also wanted to update you on its visibility. Those with 10-inch or larger telescopes can begin looking for the object Thursday night Oct. 29th when it reaches magnitude +13.5. The following night it leaps to +11.5 with a peak brightness of +10.0 occurring around 14:00 UT (9 a.m. CDT) on Halloween. TB145 fades rapidly thereafter – down to 15th magnitude just 8 hours later.
A brand new batch of Pluto and Charon photos showed up today on the New Horizons LORRI (LOng-Range Reconnaissance Imager) site. The photos were taken during the close flyby of the system on July 14, 2015 and show rich detail including craters and parallel cracks on Charon and thousands of small pits punctuating Pluto’s nitrogen ice landscape. Have at ’em!
This wider view shows the snakeskin-like textured surface of Pluto’s icy plains riddled with small pits. It almost looks like the dark areas in the sinuous channels between the mounds were once covered with frost or ice that has since sublimated away. They look similar to the polar regions on Mars where carbon dioxide frost burns off in the spring to reveal darker material beneath. Credit: NASA/JHUAPL/SwRI
The first couple images feature the region informally known as Sputnik Planum. According to a releasefrom NASA today, scientists think the region is composed of volatile ices such as solid nitrogen. They theorize that the pits and troughs – typically hundreds of meters across and tens of meters deep – are possibly formed by sublimation or evaporation of these ices in Pluto’s thin atmosphere. Still, their curious shapes and alignments remain a mystery. Adding to the intrigue is that even when seen up close, no impact craters are visible, testifying to the icy plain’s extreme geologic youth.
By the way, there are more images at the LORRI link at top. I picked a representative selection but I encourage you to visit and explore.
Now that’s what I call getting a photo in low light. Sunlight scrapes across rugged mountains as well as highlight the ubiquitous pitted terrain. Credit: NASA/JHUAPL/SwRILife’s definitely the pits on Pluto’s Tombaugh Regio. This photo shows the fainter “ghost” pits well. Is ice filling them in or are we seeing the beginning of a pit’s formation? Credit: NASA/JHUAPL/SwRIA fine view of Pluto’s largest moon Charon and its vast canyon system. Credit: NASA/JHUAPL/SwRILooking over Charon’s dark north polar region, the border of which is highlighted by several beautiful rayed craters. Not that it’s necessarily related, but the dark spot reminds me of a lunar mare or sea. On the moon, cracks in the crust allowed lava to fill gigantic basins to create the maria. Could material from beneath Charon have bubbled up to fill an ancient impact? Credit: NASA/JHUAPL/SwRISpeaking of the Moon, the large cracks at left resemble lunar rills, some of which formed through faulting / fracturing and others as conduits for lava flows. The multiple, fine cracks are interesting. Credit: NASA/JHUAPL/SwRISplendid rayed crater with an interesting contrast between dark and light ejecta. Credit: NASA/JHUAPL/SwRIA busy region on Charon, the meeting place of different terrains. Credit: NASA/JHUAPL/SwRI
“Bizarre.” “Interesting.” “Giant transit”. That were the reactions of Planet Hunters project volunteers when they got their first look at the light curve of the otherwise normal sun-like star KIC 8462852 nearly.
Of the more than 150,000 stars under constant observation during the four years of NASA’s primary Kepler Mission (2009-2013), this one stands alone for the inexplicable dips in its light. While almost certainly naturally-caused, some have suggested we consider other possibilities.
Kepler-11, a sun-like star orbited by six planets. At times, two or more planets pass in front of the star at once, as shown in this artist’s conception of a simultaneous transit of three planets observed by the Kepler spacecraft on Aug. 26, 2010. During each pass or transit, the star’s light fades in a periodic way. Credit: NASA/Tim Pyle
You’ll recall that the orbiting Kepler observatory continuously monitored stars in a fixed field of view focused on the constellations Lyra and Cygnus hoping to catch periodic dips in their light caused by transiting planets. If a drop was seen, more transits were observed to confirm the detection of a new exoplanet.
And catch it did. Kepler found 1,013 confirmed exoplanets in 440 star systems as of January 2015 with 3,199 unconfirmed candidates. Measuring the amount of light the planet temporarily “robbed” from its host star allowed astronomers to determine its diameter, while the length of time between transits yielded its orbital period.
Graph showing the big dip in brightness of KIC 8462852 around 800 days (center) followed after 1500 days whole series of dips of varying magnitude up to 22%. The usual drop in light when an exoplanet transits its host star is a fraction of a percent. The star’s normal brightness has been set to “1.00” as a baseline. Credit: Boyajian et. all
Volunteers with the Planet Hunters project, one of many citizen science programs under the umbrella of Zooniverse, harness the power of the human eye to examine Kepler light curves (a graph of a star’s changing light intensity over time), looking for repeating patterns that might indicate orbiting planets. They were the first to meet up with the perplexing KIC 8462852.
A detailed look at a small part of the star’s light curve reveals an unknown, regular variation of its light every 20 days. Superimposed on that is the star’s 0.88 day rotation period. Credit: Boyajian et. all
This magnitude +11.7 star in Cygnus, hotter and half again as big as the Sun, showed dips all over the place. Around Day 800 during Kepler’s run, it faded by 15% then resumed a steady brightness until Days 1510-1570, when it underwent a whole series of dips including one that dimmed the star by 22%. That’s huge! Consider that an exo-Earth blocks only a fraction of a percent of a star’s light; even a Jupiter-sized world, the norm among extrasolar planets, soaks up about a percent.
Exoplanets also show regular, repeatable light curves as they enter, cross and then exit the faces of their host stars. KIC 8462852’s dips are wildly a-periodic.
Could a giant comet breakup and subsequent cascading breakups of those pieces be behind KIC 8462852’s erratic changes in brightness? Credit: NASA
Whatever’s causing the flickering can’t be a planet. With great care, the researchers ruled out many possibilities: instrumental errors, starspots (like sunspots but on other stars), dust rings seen around young, evolving stars (this is an older star) and pulsations that cover a star with light-sucking dust clouds.
What about a collision between two planets? That would generate lots of material along with huge clouds of dust that could easily choke off a star’s light in rapid and irregular fashion.
A great idea except that dust absorbs light from its host star, warms up and glows in infrared light. We should be able to see this “infrared excess” if it were there, but instead KIC 8462852 beams the expected amount of infrared for a star of its class and not a jot more. There’s also no evidence in data taken by NASA’s Wide-field Infrared Survey Explorer (WISE) several years previously that a dust-releasing collision happened around the star.
Our featured star shines at magnitude +11.7 in the constellation Cygnus the Swan (Northern Cross) high in the southern sky at nightfall this month. A 6-inch or larger telescope will easily show it. Use this map to get oriented and the map below to get there. Source: Stellarium
After examining the options, the researchers concluded the best fit might be a shattered comet that continued to fragment into a cascade of smaller comets. Pretty amazing scenario. There’s still dust to account for, but not as much as other scenarios would require.
Detailed map showing stars to around magnitude 12 with the Kepler star identified. It’s located only a short distance northeast of the open cluster NGC 6886 in Cygnus. North is up. Click to enlarge. Source: Chris Marriott’s SkyMap
Being fragile types, comets can crumble all by themselves especially when passing exceptionally near the Sun as sungrazing comets are wont to do in our own Solar System. Or a passing star could disturb the host star’s Oort comet cloud and unleash a barrage of comets into the inner stellar system. It so happens that a red dwarf star lies within about 1000 a.u. (1000 times Earth’s distance from the Sun) of KIC 8462852. No one knows yet whether the star orbits the Kepler star or happens to be passing by. Either way, it’s close enough to get involved in comet flinging.
So much for “natural” explanations. Tabetha Boyajian, a postdoc at Yale, who oversees the Planet Hunters and the lead author of the paper on KIC 8462852, asked Jason Wright, an assistant professor of astronomy at Penn State, what he thought of the light curves. “Crazy” came to mind as soon he set eyes on them, but the squiggles stirred a thought. Turns out Wright had been working on a paper about detecting transiting megastructures with Kepler.
There are Dyson rings and spheres and a Dyson swarm depicted here. Could this or a variation of it be what we’re seeing around KIC 8462852? Not likely, but a fun thought experiment. Credit: Wikipedia
In a recent blog, he writes: “The idea is that if advanced alien civilizations build planet-sized megastructures — solar panels, ring worlds, telescopes, beacons, whatever — Kepler might be able to distinguish them from planets.” Let’s assume our friendly aliens want to harness the energy of their home star. They might construct enormous solar panels by the millions and send them into orbit to beam starlight down to their planet’s surface. Physicist Freeman Dyson popularized the idea back in the 1960s. Remember the Dyson Sphere, a giant hypothetical structure built to encompass a star?
From our perspective, we might see the star flicker in irregular ways as the giant panels circled about it. To illustrate this point, Wright came up with a wonderful analogy:
“The analogy I have is watching the shadows on the blinds of people outside a window passing by. If one person is going around the block on a bicycle, their shadow will appear regularly in time and shape (like a regular transiting planet). But crowds of people ambling by — both directions, fast and slow, big and large — would not have any regularity about it at all. The total light coming through the blinds might vary like — Tabby’s star.”
The Green Bank Telescope is the world’s largest, fully-steerable telescope. The GBT’s dish is 100-meters by 110-meters in size, covering 2.3 acres of space. Credit: NRAO/AUI/NSF
Even Wright admits that the “alien hypothesis” should be seen as a last resort. But to make sure no stone goes unturned, Wright, Boyajian and several of the Planet Hunters put together a proposal to do a radio-SETI search with the Green Bank 100-meter telescope. In my opinion, this is science at its best. We have a difficult question to answer, so let’s use all the tools at our disposal to seek an answer.
KIC 8462852, photographed on Oct. 15, 2015. It’s an F3 V star (yellow-white dwarf) located about 1,480 light years from Earth. Credit: Gianluca Masi
In the end, it’s probably not an alien megastructure, just like the first pulsar signals weren’t sent by LGM-1 (Little Green Men). But whatever’s causing the dips, Boyajian wants astronomers to keep a close watch on KIC 8462852 to find out if and when its erratic light variations repeat. I love a mystery, but answers are even better.
