Artist's impression of the 100-kg Philae lander (screenshot) Credit: ESA/DLR
In less than a month, on November 12, 2014, the 100-kg Philae lander will separate from ESA’s Rosetta spacecraft and descend several kilometers down to the dark, dusty and frozen surface of Comet 67P/Churyumov-Gerasimenko, its three spindly legs and rocket-powered harpoon all that will keep it from crashing or bouncing hopelessly back out into space. It will be the culmination of a decade-long voyage across the inner Solar System, a testament to human ingenuity and inventiveness and a shining example of the incredible things we can achieve through collaboration. But first, Philae has to get there… it has to touch down safely and successfully become, as designed, the first human-made object to soft-land on the nucleus of a comet. How will the little spacecraft pull off such a daring maneuver around a tumbling chunk of icy rubble traveling over 18 km/s nearly 509 million km away? The German Aerospace Center (DLR) has released a “trailer” for the event, worthy of the best sci-fi film. Check it out below.
Want to see more? Of course you do. Keep an eye out for the 11-minute short film “Landing on a Comet – The Rosetta Mission” to be released soon on YouTube here, and follow the latest news from the Rosetta mission here (and here on Universe Today, too!)
“The reason we’re at this comet is for science, no other reason. We’re doing this to get the best science. To characterize this comet has never been done before.”
Original Material: DLR (CC-BY 3.0)
Footage: ESA
Credit 67P image: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA
Music: Omega by TimMcMorris
Earth and the Moon imaged by the MESSENGER spacecraft on Oct. 8, 2014
Yes, it’s another time-lapse of the October 8 lunar eclipse that was observed by skywatchers across half the Earth… except that these images weren’t captured from Earth at all; this was the view from Mercury!
The animation above was constructed from 31 images taken two minutes apart by the MESSENGER spacecraft between 5:18 a.m. and 6:18 a.m. EDT on Oct. 8, 2014.
“From Mercury, the Earth and Moon normally appear as if they were two very bright stars,” said Hari Nair, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory, which developed and operates the MESSENGER mission for NASA. “During a lunar eclipse, the Moon seems to disappear during its passage through the Earth’s shadow, as shown in the movie.”
According to Nair the images have been zoomed by a factor of two and the Moon’s brightness has been increased by a factor of about 25 to enhance visibility. Captured by MESSENGER’s narrow-angle camera, Earth and the Moon were 0.713 AU (106.6 million km / 66.2 million miles) away from Mercury when the images were acquired.
Want to see some great photos of the eclipse shared by talented photographers around the world? Click here.
The Oct. 8 “Hunter’s Moon” eclipse was the second and last total lunar eclipse of 2014. The next will occur on April 4 of next year… but by that time MESSENGER won’t be around to witness it.
Launched August 3, 2004, MESSENGER entered orbit at Mercury on March 18, 2011. It is currently nearing the end of its missions as well as its its operational life, but we still have several more months of observations to look forward to from around the Solar System’s innermost planet before MESSENGER makes its final pass and ultimately impacts Mercury’s surface in March 2015.
Video credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
Illustration of MESSENGER in orbit around Mercury (NASA/JPL/APL)
A little over a week before NASA’s MAVEN spacecraft fired its rockets to successfully enter orbit around Mars, MESSENGER performed a little burn of its own – the second of four orbit correction maneuvers (OCMs) that will allow it to remain in orbit around Mercury until next March. Although it is closing in on the end of its operational life it’s nice to know we still have a few more months of images and discoveries from MESSENGER to look forward to!
MESSENGER’s orientation after the start of orbit correction maneuver 10 (OCM-10). Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Carnegie Institution of Washington
The first OCM burn was performed on June 17, raising MESSENGER’s orbit from 115 kilometers (71.4 miles) to 156.4 kilometers (97.2 miles) above the surface of Mercury. That was the ninth OCM of the MESSENGER mission, and at 11:54 a.m. EDT on Sept. 12, 2014, the tenth was performed.
At the time of this most recent maneuver, MESSENGER was in an orbit with a closest approach of 24.3 kilometers (15.1 miles) above the surface of Mercury. With a velocity change of 8.57 meters per second (19.17 miles per hour), the spacecraft’s four largest monopropellant thrusters (with a small contribution from four of the 12 smallest monopropellant thrusters) nudged the spacecraft to an orbit with a closest approach altitude of 94 kilometers (58.4 miles). This maneuver also increased the spacecraft’s speed relative to Mercury at the maximum distance from Mercury, adding about 3.2 minutes to the spacecraft’s eight-hour, two-minute orbit period.
OCM-10 lasted for 2 1/4 minutes and added 3.2 minutes to the spacecraft’s 8-hour, 2-minute-long orbit. (Source)
The next two burns will occur on October 24 and January 21.
After its two final successful burns MESSENGER will be out of propellant, making any further OCMs impossible. At the planned end of its mission MESSENGER will impact Mercury’s surface in March of 2015.
Built and operated by The Johns Hopkins University Applied Physics Laboratory (JHUAPL), MESSENGER launched from Cape Canaveral Air Force Station on August 3, 2004. It entered orbit around Mercury on March 18, 2011, the first spacecraft ever to do so. Since then it has performed countless observations of our Solar System’s innermost planet and has successfully mapped 100% of its surface. Check out the infographic below showing some of the amazing numbers racked up by MESSENGER since its launch ten years ago, and read more about the MESSENGER mission here.
“MESSENGER by the Numbers” – an infographic by NASA
Image of Rosetta's solar array and comet 67P/C-G taken by Philae on Sept. 7, 2014 (ESA/Rosetta/Philae/CIVA)
Spacecraft “selfies” are always a treat and this one is doubly awesome: taken by the Philae lander piggybacked onto ESA’s Rosetta, it shows one of the spacecraft’s 14-meter-long (46-foot) solar arrays glinting with reflected sunlight while off in the distance is the double-lobed nucleus of Comet 67P/Churyumov-Gerasimenko!
Rosetta has been circling the comet for over a month now and returning some truly amazing images, but leave it to little Philae to put it all into perspective. Such a show-stealer! (Not that we mind, of course.)
The image above was acquired with Philae’s CIVA (Comet nucleus Infrared and Visible Analyzer) instrument on Sept. 7, 2014, from a distance of 50 km (31 miles) from Comet 67P/C-G. It’s actually a composite of two separate images made with different exposures adjusted for the lighting disparities between the spacecraft and comet.
Artist impression of Philae on the surface of comet 67P/Churyumov-Gerasimenko. Credit: ESA/ATG medialab
The Philae (say “FEE-lay”) lander itself weighs 100 kg (220 lbs) and is about a meter wide and 80 cm high (3.2 x 2.6 feet). The CIVA instrument, one of ten installed on the lander, is composed of seven miniature cameras that will take panoramic pictures of 67P’s surface and reconstruct its structure in 3D, as well as a microscope and a near-infrared imager to study its composition, texture, and reflectivity. (Source)
This is the second image from Philae this year to feature part of the Rosetta spacecraft (but the first to show the comet); the previous was taken in April 2014.
Back in 2007 Philae took a shot that showed Rosetta’s solar panel and Mars; check that one out here.
Currently Rosetta is being transitioned to its Global Mapping Phase (GMP). This is an incredibly intensive process that will determine how close the spacecraft will be able to get to the surface of the comet as engineers search for the best landing area to which to deploy Philae in November.
Learn more about the Rosetta mission and Comet 67P/C-G here.
Animation of Pluto and Charon showing nearly a full rotation (NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute)
Now here’s something I guarantee you’ve never seen before: a video of the dwarf planet Pluto and its largest moon Charon showing the two distinctly separate worlds actually in motion around each other! Captured by the steadily-approaching New Horizons spacecraft from July 19–24, the 12 images that comprise this animation were acquired with the Long Range Reconnaissance Imager (LORRI) instrument from distances of 267 million to 262 million miles (429 million to 422 million km) and show nearly a full orbital rotation. Absolutely beautiful!
For a close-up video of the two worlds in motion, click below:
Pluto and Charon rotation movie from New Horizons (enlarged view)
Pluto and Charon are seen circling a central gravitational point known as the barycenter, which accounts for the wobbling motion. Since Charon is 1/12th the mass of Pluto the center of mass between the two actually lies a bit outside Pluto’s radius, making their little gravitational “dance” readily apparent.
(The same effect happens with the Earth and Moon too, but since the barycenter lies 1,700 km below Earth’s surface it’s not nearly as obvious.)
“The image sequence showing Charon revolving around Pluto set a record for close range imaging of Pluto—they were taken from 10 times closer to the planet than the Earth is,” said New Horizons mission Principal Investigator Alan Stern, of the Southwest Research Institute. “But we’ll smash that record again and again, starting in January, as approach operations begin.”
Artist concept of the New Horizons spacecraft. Credit: NASA
Launched January 19, 2006, New Horizons is now in the final year of its journey to the Pluto system. On August 25 it will pass the orbit of Neptune – which, coincidentally, is 25 years to the day after Voyager 2’s closest approach – and then it’s on to Pluto and Charon, which New Horizons will become the first spacecraft to fly by on July 14, 2015, at distances of 10,000 and 27,000 km respectively. Find out where New Horizons is right now here.
Source: New Horizons
Credit: NASA/Johns Hopkins University Applied Physics Laboratory/Southwest Research Institute
Image of Io taken in the near-infrared with adaptive optics at the Gemini North telescope on August 29. In addition to the extremely bright eruption on the upper right limb of the satellite, the lava lake Loki is visible in the middle of Io’s disk, as well as the fading eruption that was detected earlier in the month by de Pater on the southern (bottom) limb. Io is about one arcsecond across. Image credit: Katherine de Kleer/UC Berkeley/Gemini Observatory/AURA
Jupiter’s innermost moon, Io — with over 400 active volcanoes, extensive lava flows and floodplains of liquid rock — is by far the most geologically active body in the Solar System. But last August, Io truly came alive with volcanism.
Three massive volcanic eruptions led astronomers to speculate that these presumed rare outbursts were much more common than previously thought. Now, an image from the Gemini Observatory captures what is one of the brightest volcanoes ever seen in our Solar System.
“We typically expect one huge outburst every one or two years, and they’re usually not this bright,” said lead author Imke de Pater from the University of California, Berkeley, in a press release. In fact, only 13 large eruptions were observed between 1978 and 2006. “Here we had three extremely bright outbursts, which suggest that if we looked more frequently we might see many more of them on Io.”
De Pater discovered the first two eruptions on August 15, 2013, from the W. M. Keck Observatory in Hawaii. The brightest was calculated to have produced a 50 square-mile, 30-feet thick lava flow, while the other produced flows covering 120 square miles. Both were nearly gone when imaged days later.
The third and even brighter eruption was discovered on August 29, 2013, at the Gemini observatory by UC Berkeley graduate student Katherine de Kleer. It was the first of a series of observations monitoring Io.
Images of Io tracking the evolution of the eruption as it decreased in intensity over 12 days. Due to Io’s rapid rotation, a different area of the surface is viewed on each night; the outburst is visible with diminishing brightness on August 29 & 30 and September 1, 3, & 10. Image credit: Katherine de Kleer / UC Berkeley / Gemini Observatory / AURA
This allowed the observations to “represent the best day-by-day coverage of such an eruption,” said de Kleer. The team was able to conclude that the energy emitted from the late-August eruption was about 20 Terawatts, and expelled many cubic kilometers of lava.
“At the time we observed the event, an area of newly-exposed lava on the order of tens of square kilometers was visible,” said de Kleer. “We believe that it erupted in fountains from long fissures on Io’s surface, which were over ten-thousand-times more powerful than the lava fountains during the 2010 eruption of Eyjafjallajokull, Iceland, for example.”
The team hopes that monitoring Io’s surface annually will reveal the style of volcanic eruptions on the moon, the composition of the magma, and the spatial distribution of the heat flows. The eruptions may also shed light on an early Earth, when heat from the decay of radioactive elements — as opposed to the tidal forces influencing Io — created exotic, high-temperature lavas.
“We are using Io as a volcanic laboratory, where we can look back into the past of the terrestrial planets to get a better understanding of how these large eruptions took place, and how fast and how long they lasted,” said coauthor Ashley Davies.
The latest results have been published in the journal Icarus.
Artist's concept of OSIRIS-REx at Bennu. (Credit: NASA/GSFC)
I love anything that attempts to provide a sense of scale about the Solar System (see here and here for even more examples) and this one brings us down past the Sun, planets, and moons all the way to asteroid size — specifically asteroid 101955 Bennu, the target of the upcoming OSIRIS-REx mission.
Created by the OSIRIS-REx “321Science!” team, consisting of communicators, film and graphic arts students, teens, scientists, and engineers, the video shows some relative scales of our planet compared to the Sun, and also the actual size of asteroid Bennu in relation to some familiar human-made structures that we’re familiar with. (My personal take-away from this: Bennu — one of those “half grains of sand” — is a rather small target!)
A NASA New Frontiers mission, OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer) will launch in Sept. 2016 on a two-year journey to the asteroid 101955 Bennu. Upon arrival OSIRIS-REx will map Bennu’s surface and also measure the Yarkovsky effect, by which asteroids’ trajectories can change over time due to the small force exerted by radiant heat.
Comet 67P/Churyumov-Gerasimenko imaged by OSIRIS on July 29, 2014
WOW! We’re really getting to the good stuff now! This is no computer-generated shape model, this is the real deal: the double-lobed nucleus of Comet 67P/C-G, as imaged by Rosetta’s OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) narrow-angle camera on Tuesday, July 29. At the time just about a week away from making its arrival, ESA’s spacecraft was 1,950 km (1,211 miles) from the comet when this image was taken. (That’s about the distance between Providence, Rhode Island and Miami, Florida… that’s one fancy zoom lens, Rosetta!)
Comet 67P/Churyumov-Gerasimenko imaged on July 14, 2014 by OSIRIS from a distance of approximately 12,000 km. (ESA)
This latest image reveals some actual surface features of the 4-km-wide comet, from a few troughs and mounds to the previously-noted bright band around the “neck” connecting the two lobes. The resolution in the July 29 OSIRIS image is 37 meters per pixel.
Since Rosetta is quickly closing the gap between itself and the comet we can only expect better images to come in the days ahead, so stay tuned — this is going to be an exciting August!
Keep up with the latest news on ESA’s Rosetta blog here, and find out where exactly Rosetta and Comet 67P/C-G are in the Solar System here.
An artist's conception of the hot local bubble. Image Credit: NASA
I spent this past weekend backpacking in Rocky Mountain National Park, where although the snow-swept peaks and the dangerously close wildlife were staggering, the night sky stood in triumph. Without a fire, the stars, a few planets, and the surprisingly bright Milky Way provided the only light to guide our way.
But the night sky as seen by the human eye is relatively dark. Little visible light stretching across the cosmos from stars, nebulae, and galaxies actually reaches Earth. The entire night sky as seen by an X-ray detector, however, glows faintly.
The origins of the soft X-ray glow permeating the sky have been highly debated for the past 50 years. But new findings show that it comes from both inside and outside the Solar System.
Decades of mapping the sky in X-rays with energies around 250 electron volts — about 100 times the energy of visible light — revealed soft emission across the sky. And astronomers have long searched for its source.
At first, astronomers proposed a “local hot bubble” of gas — likely carved by a nearby supernova explosion during the past 20 million years — to explain the X-ray background. Improved measurements made it increasingly clear that the Sun resides in a region where interstellar gas is unusually sparse.
But the local bubble explanation was challenged when astronomers realized that comets were an unexpected source of soft X-rays. In fact, this process, known as solar wind charge exchange, can occur anywhere atoms interact with solar wind ions.
After this discovery, astronomers turned their eyes to within the Solar System and began to wonder whether the X-ray background might be produced by the ionized particles in the solar wind colliding with diffuse interplanetary gas.
In order to solve the outstanding mystery, a team of astronomers led by Massimilliano Galeazzi from the University of Miami developed an X-ray instrument capable of taking the necessary measurements.
Galeazzi and colleagues rebuilt, tested, calibrated, and adapted X-ray detectors originally designed by the University of Wisconsin and flown on sounding rockets in the 1970s. The mission was named DXL, for Diffuse X-ray emission from the Local Galaxy.
On Dec. 12, 2012, DXL launched from the White Sands Missile Range in New Mexico atop a NASA Black Brant IX sounding rocket. It reached a peak altitude of 160 miles and spent a total of five minutes above Earth’s atmosphere.
The data collected show that the emission is dominated by the local hot bubble, with, at most, 40 percent originating from within the Solar System.
“This is a significant discovery,” said lead author Massimiliano Galeazzi from the University of Miami in a press release. “Specifically, the existence or nonexistence of the local bubble affects our understanding of the galaxy in the proximity to the Sun and can be used as foundation for future models of the Galaxy structure.”
It’s now clear that the Solar System is currently passing through a small cloud of cold interstellar gas as it moves through the Milky Way.
Colors indicate the density of interstellar helium near Earth and its enhancement in a downstream cone as the neutral atoms respond to the sun’s gravity (blue is low density, red is high). Also shown are the observing angles for DXL and ROSAT. Image Credit: NASA’s Goddard Space Flight Center
The cloud’s neutral hydrogen and helium atoms stream through the Solar System at about 56,000 mph (90,000 km/h). The hydrogen atoms quickly ionize, but the helium atoms travel at a path largely governed by the Sun’s gravity. This creates a helium focusing cone — a breeze focused downstream from the Sun — with a much greater density of neutral atoms. These easily collide with solar wind ions and emit soft X-rays.
The confirmation of the local hot bubble is a significant development in our understanding of the interstellar medium, which is crucial for understanding star formation and galaxy evolution.
“The DXL team is an extraordinary example of cross-disciplinary science, bringing together astrophysicists, planetary scientists, and heliophysicists,” said coauthor F. Scott Porter from NASA’s Goddard Space Flight Center. “It’s unusual but very rewarding when scientists with such diverse interests come together to produce such groundbreaking results.”
Have you ever heard that spacecraft can speed themselves up by performing gravitational slingshot maneuvers? What’s involved to get yourself going faster across the Solar System.
Let’s say you want to go back in time and prevent Kirk from dying on the Enterprise B.
You could use a slingshot maneuver. You’d want to be careful that you don’t accidentally create an alternate reality future where the Earth has been assimilated by the Borg, because Kirk wasn’t in the Nexus to meet up with Professor Picard and Sir Iandalf Magnetopants, while they having the best time ever gallivanting around New York City.
*sigh* Ah, man. I really love those guys. What was I saying? Oh right. One of the best ways to increase the speed of a spacecraft is with a gravitational slingshot, also known as a gravity assist.
There are times that fantasy has bled out too far into the hive mind, and people confuse a made up thing with an actual thing because of quirky similarities, nomenclature and possibly just a lack of understanding.
So, before we go any further a “gravitational slingshot” is a gravity assist that will speed up an actual spacecraft, “slingshot maneuver” is made up bananas nonsense. For example, when Voyager was sent out into the Solar System, it used gravitational slingshots past Jupiter and Saturn to increase its velocity enough to escape the Sun’s gravity.
So how do gravitational assists work? You probably know this involves flying your spacecraft dangerously close to a massive planet. But how does this help speed you up? Sure, as the spacecraft flies towards the planet, it speeds up. But then, as it flies away, it slows down again. Sort of like a skateboarder in a half pipe.
This process nets out to zero, with no overall increase in velocity as your spacecraft falls into and out of the gravity well. So how do they do it? Here’s the trick. Each planet has an orbital speed travelling around the Sun.
As the spacecraft approaches the planet, its gravity pulls the much lighter spacecraft so that it catches up with the planet in orbit. It’s the orbital momentum from the planet which gives the spacecraft a tremendous speed boost. The closer it can fly, the more momentum it receives, and the faster it flies away from the encounter.
To kick the velocity even higher, the spacecraft can fire its rockets during the closest approach, and the high speed encounter will multiply the effect of the rockets. This speed boost comes with a cost. It’s still a transfer of momentum. The planet loses a tiny bit of orbital velocity.
If you did enough gravitational slingshots, such as several zillion zillion slingshots, you’d eventually cause the planet to crash into the Sun. You can use gravitational slingshots to decelerate by doing the whole thing backwards. You approach the planet in the opposite direction that it’s orbiting the Sun. The transfer of momentum will slow down the spacecraft a significant amount, and speed up the planet an infinitesimal amount.
Messenger’s complicated flyby trajectory. Credit: NASA
NASA’s MESSENGER spacecraft made 2 Earth flybys, 2 Venus flybys and 3 Mercury flybys before it was going slowly enough to make an orbital insertion around Mercury. Ulysses, the solar probe launched in 1990, used gravity assists to totally change its trajectory into a polar orbit above and below the Sun. And Cassini used flybys of Venus, Earth and Jupiter to reach Saturn with an efficient flight path.
Nature sure is trying to make it easy for us. Gravitational slingshots are an elegant way to slow down spacecraft, tweak their orbits into directions you could never reach any other way, or accelerate to incredible speeds.
It’s a brilliant dance using orbital mechanics to aid in our exploration of the cosmos. It’s a shining example of the genius and the ingenuity of the minds who are helping to push humanity further out into the stars.
What do you think? What other places is the general comprehension between actual facts and fictional knowledge blurring, just like the “slingshot maneuver” and “gravitational slingshot”?
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