Tag: asteroids

Astronomer discovers newest farthest solar system object

8:16 am

Worlds without end: An astronomer leading a team looking for a large planet beyond Pluto has broken their own record and found a new solar system object that is the farthest known from the Sun.

That’s when he saw it, a faint object at a distance 140 times farther from the sun than Earth — the farthest solar system object yet known, some 3.5 times more distant than Pluto. The object, if confirmed, would break his team’s own discovery, announced in December, of a dwarf planet 120 times farther out than Earth, which they nicknamed “Farout.” For now, they are jokingly calling the new object “FarFarOut”. “This is hot off the presses,” he said during his rescheduled talk on 21 February.

I like the names for both.

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Confirmed: Hayabusa-2 grabbed got a sample of Ryugu

9:22 pm

The Hayabusa-2 science team has confirmed that in the spacecraft’s quick touchdown on the surface of the asteroid Ryugu today it successfully snagged an asteroid sample.

Mission team members announced at about 6:30 p.m. EST (2330 GMT) today that the order to fire the bullet had been issued, and that Hayabusa2 had moved away from Ryugu as planned. But it took a few more hours for them to confirm that the bullet had indeed fired, and that sample collection occurred.

…The collected samples are key to this objective: The Ryugu material will come down to Earth in a special return capsule in December 2020. Scientists in labs around the world can then scrutinize the stuff with far more advanced equipment than the Hayabusa2 team could pack onto a single spacecraft.

The sample bounty will include more than just the material Hayabusa2 collected today. The mothership is expected to grab two more samples in the coming weeks and months. The second sampling sortie will unfold much like today’s did, but the third will be dramatically different: Hayabusa2 will fire a copper projectile into Ryugu, wait a bit for the dust to clear, and then swoop in to grab material from the newly created crater. This formerly subsurface stuff will be pristine, unaffected by weathering from deep-space radiation.

More thrills to come, obviously.

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Hayabusa-2 has begun approach to Ryugu

8:37 am

Ryugu during approach

Hayabusa-2 has begun its approach to Ryugu, aiming for a quick touchdown and sample grab at approximately 7:06 pm (Eastern) tonight. The image at the right is the most recent taken during the approach.

The risks? From the Hayabusa-2 website:

Our original schedule planned for touchdown in late October of last year (2018). However, Ryugu was revealed as a boulder strewn landscape that extended across the entire surface, with no flat or wide-open regions. Before arriving at Ryugu, it was assumed there would be flat areas around 100 meters in size. But far than finding this, we have not even seen flat planes 30 meters across!

During the scheduled time for touchdown in late October, we did not touchdown but descended and dropped a target marker near the intended landing site. We were able to drop the target marker in almost the planned spot and afterwards we examined the vicinity of the target marker landing site in detail. Finally, the area denoted L08-E1 was selected as the place for touchdown.

From the first link above you can see approach images as they are downloaded today, about once every half hour.

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Hayabusa-2 prepares to land

9:54 am

Ryugu's northen hemisphere

The JAXA science team has released a set of images taken in January by Hayabusa-2 of its landing site on Ryugu, describing how those images helped map the region where touchdown will occur on February 22. The image on the right is one such image.

[It] shows a diagonally imaged photograph of Ryugu, captured by moving the spacecraft towards the direction of the north pole. The upper side of the image shows the north pole and reveals a landscape dominated with many large boulders. The white band extending to the left and right slightly below the center of the image is the equatorial ridge (Ryujin Ridge). The arrow tip marks the planned touchdown site and you can see this site is on the main ridge.

This is the first time we have images the northern hemisphere of Ryugu. In this observation, we acquired data on the equatorial region of Ryugu, the southern and northern hemisphere. Imaging the entire area is very important for creating accurate global shape models for Ryugu.

They should begin beaming images down of the landing approach sometime tomorrow, and will do so about every 30 minutes throughout the sequence.

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Asteroid to eclipse Sirius, the sky’s brightest star, on February 18

8:46 am

On February 18, 2019 a four-mile wide asteroid is going to pass in front of Sirius, the sky’s brightest star, and block its light for just under two seconds.

Can a 7-kilometer-wide asteroid make Sirius disappear? You bet it can. That just might happen on Monday night, February 18th. That evening around 10:30 p.m. MST (5:30 UT February 19th), there’s a good probability that the 17th-magnitude 4388 Jürgenstock will occult the sky’s brightest star for up to 1.8 seconds. Visibility stretches along a narrow path from the southern tip of Baja California to the Las Cruces–El Paso region, up through the Great Plains, and north to the Winnipeg area. While only a limited number of people may see this event, anytime Sirius disappears, however briefly, it’s news!

In the U.S. the narrow path cuts through New Mexico, Colorado, Nebraska, South Dakota, and North Dakota. If you live in or near this path, this is definitely worth watching, especially since it will be happening at a convenient hour in the evening.

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Recent Cuba meteorite estimated to have weighed about 360 tons

1:36 pm

Using its imaged track from several sources, scientists have now estimated the size and weight of the recent spectacular fireball over Cuba as being several meters across and weighing about 360 tons.

After reconstructing the trajectory in the atmosphere, the Colombian astronomers “played back” the impact and found that the culprit, a rock with an estimated size of several meters and a weight of about 360 tons, came from an eccentric orbit around the Sun with an average distance to our star of 1.3 astronomical units (1 astronomical-unit = 150 million km). Before impacting the Earth, the rock completed a turn around the Sun every 1.32 years. All that came to an end on February 1, 2019 when both, the rock and the Earth, found themselves at the same point in space, at the same time. The worse part was for the rock!

The article spends most of its time selling a computer model the scientists have developed that they claim can predict the approach trajectory of meteorites, something I find quite unconvincing. However, the result above is important for different reasons. Routinely astronomers today discover new small asteroids just days before they zoom harmlessly past the Earth. Each time one of these new near Earth asteroids is found, the press automatically goes into “Chicken Little mode,” suggesting that should this object have hit the Earth it would have caused massive damage.

Most of these newly discovered asteroids are about the same size as the Cuba meteorite, if not smaller. Thus, this meteorite gives us a clear idea of how completely harmless these other near Earth asteroids are. In fact, this impact suggests to me that in most cases an asteroid would have to be about ten times larger to pose a significant threat.

Keep this number — 360 tons — in mind the next time another near Earth asteroid is discovered.

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New Horizons’ farewell image of Ultima Thule

4:34 pm

Ultima Thule's shape

The New Horizons science team has released the last sequence of images taken by the spacecraft as flew away after its flyby.

The link has a nice video of that sequence. However, it is the information gleaned from this sequence that is most interesting.

The newly released images also contain important scientific information about the shape of Ultima Thule, which is turning out to be one of the major discoveries from the flyby.

The first close-up images of Ultima Thule – with its two distinct and, apparently, spherical segments – had observers calling it a “snowman.” However, more analysis of approach images and these new departure images have changed that view, in part by revealing an outline of the portion of the KBO that was not illuminated by the Sun, but could be “traced out” as it blocked the view to background stars.

Stringing 14 of these images into a short departure movie, New Horizons scientists can confirm that the two sections (or “lobes”) of Ultima Thule are not spherical. The larger lobe, nicknamed “Ultima,” more closely resembles a giant pancake and the smaller lobe, nicknamed “Thule,” is shaped like a dented walnut.

The image on the right shows their preliminary guess at Ultima Thule’s overall shape, as suggested by these new images.

The spacecraft has still not sent back the images it took during its closest approach, so there are likely more surprises coming.

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Rare asteroid orbiting near Venus discovered

11:51 am

The Zwicky Transient Facility (ZTF), a new sky survey telescope whose main goal is to find Near Earth asteroids, has discovered a rare asteroid orbiting near Venus.

A state-of-the-art sky-surveying camera, the Zwicky Transient Facility, or ZTF, detected the asteroid on January 4, 2019. Designated 2019 AQ3, the object has the shortest “year” of any recorded asteroid, with an orbital period of just 165 days. It also appears to be an unusually big asteroidal specimen. “We have found an extraordinary object whose orbit barely strays beyond Venus’ orbit—that’s a big deal,” said Quanzhi Ye, a postdoctoral scholar at IPAC, a data and science center for astronomy at Caltech. Ye called 2019 AQ3 a “very rare species,” further noting that “there might be many more undiscovered asteroids out there like it.”

…The orbit, as it turns out, is angled vertically, taking 2019 AQ3 above and below the plane where the planets run their laps around the sun. Over its short year, 2019 AQ3 plunges inside of Mercury, then swings back up just outside of Venus’ orbit.

The telescope, in operation since March 2018, and so far found

nearly 60 new near-Earth asteroids. Two of these were spotted in July 2018 mere hours before they gave Earth quite a close shave. Designated 2018 NW and 2018 NX, the duo of bus-sized asteroids whipped past at a distance of about 70,000 miles, or only a third of the way to the moon. Fortunately, the newfound 2019 AQ3 poses no threat; the closest it ever comes to Earth is about 22 million miles.

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Rock from Earth, found on Moon?

2:24 pm

The uncertainty of science: Scientists studying rocks brought back by the Apollo 14 lunar mission have concluded that one sample originally came from the Earth, and if so would be the oldest known Earth rock.

It is possible that the sample is not of terrestrial origin, but instead crystallized on the Moon, however, that would require conditions never before inferred from lunar samples. It would require the sample to have formed at tremendous depths, in the lunar mantle, where very different rock compositions are anticipated. Therefore, the simplest interpretation is that the sample came from Earth.

The team’s analyses are providing additional details about the sample’s history. The rock crystallized about 20 kilometers beneath Earth’s surface 4.0-4.1 billion years ago. It was then excavated by one or more large impact events and launched into cis-lunar space. Previous work by the team showed that impacting asteroids at that time were producing craters thousands of kilometers in diameter on Earth, sufficiently large to bring material from those depths to the surface. Once the sample reached the lunar surface, it was affected by several other impact events, one of which partially melted it 3.9 billion years ago, and which probably buried it beneath the surface. The sample is therefore a relic of an intense period of bombardment that shaped the Solar System during the first billion years. After that period, the Moon was affected by smaller and less frequent impact events. The final impact event to affect this sample occurred about 26 million years ago, when an impacting asteroid hit the Moon, producing the small 340 meter-diameter Cone Crater, and excavating the sample back onto the lunar surface where astronauts collected it almost exactly 48 years ago (January 31–February 6, 1971).

The scientists also admit that their conclusion is controversial and will be disputed. If true, however, it suggests that there is significant material on the Moon from the early Earth that can provide a window into parts our planet’s history that are presently inaccessible.

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Oblique close-up image of Ceres

9:50 am

Ceres from Dawn

The Dawn science team has released an oblique close-up image of Ceres, taken in May 2018 before the Dawn mission ended. To the right is a reduced resolution version, with the full resolution photograph viewable if you click on it.

Dawn captured this view on May 19, 2018. The image shows the limb of Ceres at about 270E, 30N looking south. The spatial resolution is about 200 feet (60 meters) per pixel in the nearest parts of the image. The impact crater to the right (only partially visible) is Ninsar, named after a Sumerian goddess of plants and vegetation. It is about 25 miles (40 kilometers) in diameter.

Bright seeps running down the interior rims of several craters are visible. To my eye, the image also suggests an overall softness to Ceres. Its surface is like a sandbox, easily reshaped significantly by each impact.

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Orbital images of Bennu

9:32 am

Close-up of Bennu's southern hemisphere

The OSIRIS-REx science team has released two new images of Bennu’s southern hemisphere, taken from orbit. The image on the right is a cropped section of the highest resolution version of a montage of two images. Click on the image to see the entire two-image montage.

These two OpNav images of Bennu’s southern hemisphere, which each have an exposure time of about 1.4 milliseconds, were captured Jan. 17 from a distance of about one mile (1.6 km). They have been cropped and the contrast has been adjusted to better reveal surface features. The large boulder – fully visible in the middle of the left frame and in partial shadow in lower portion of right frame – is about 165 feet (50 meters) across.

The cropped section to the right shows that large boulder in the middle of the frame.

I’m sorry, but when I look at this rubble-pile asteroid I cannot help but think of the cat-litter clumps I remove from our cats’ litter box. The only fundamental difference is that the grains in cat litter are made to be a uniform size, while at Bennu the grains are much coarser and not uniform. Nonetheless, this asteroid is a clump of many grains, just like those cat litter clumps, and will likely crumple easily into a cloud of grains if smacked just hard enough.

This knowledge is actually very critical, as Bennu is a potentially dangerous asteroid with an orbit that might have it impact the Earth in about two hundred years.

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New impact on the Martian south polar cap

10:02 am

New impact on Mars' south pole

Cool image time! The image to the right, cropped to post here, was taken on October 5, 2018 by the high resolution camera on Mars Reconnaissance Orbiter (MRO) and shows a recent meteorite impact that occurred sometime between July and September of 2018 on the Martian polar cap . If you click on the image you can see the entire photograph. As noted in the captioned press release,

It’s notable because it occurred in the seasonal southern ice cap, and has apparently punched through it, creating a two-toned blast pattern.

The impact hit on the ice layer, and the tones of the blast pattern tell us the sequence. When an impactor hits the ground, there is a tremendous amount of force like an explosion. The larger, lighter-colored blast pattern could be the result of scouring by winds from the impact shockwave. The darker-colored inner blast pattern is because the impactor penetrated the thin ice layer, excavated the dark sand underneath, and threw it out in all directions on top of the layer.

Location on edge of south polar cap

It is not known yet the size of this meteorite. The location is shown in the overview image to the right, with the impact indicated by the white dot. The black circle in the middle of the image is the south pole itself, an area where MRO’s orbit does not allow imagery. This location, on the edge of the Martian polar cap, is helpful to scientists because it has excavated material from below the cap, providing them a peek into previously unseen the geology there. Had the impact been farther south, on the thicker cap, that hidden material below the cap would likely not have been exposed.

The cap itself is made up of both ice and frozen carbon dioxide, though the CO2 is mostly seen as frost during winter months that evaporates during the summer.

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Moon hit by small meteorite during eclipse

12:57 pm

During the lunar eclipse two days ago on January 20, 2018 amateur astronomers were able to record the impact of a small meteorite.

The MIDAS survey is a Moon-watching that scours video of its surface in the hopes of detecting the tiny flashes associated with meteorite impacts. In this case, MIDAS scored a home run, and it was the first time the system was able to spot an impact during a total lunar eclipse.

“In total I spent almost two days without sleeping, including the monitoring time during the eclipse,” [Jose] Madiedo explained to Gizmodo. “I was exhausted when the eclipse ended—but when the automatic detection software notified me of a bright flash, I jumped out of my chair. It was a very exciting moment because I knew such a thing had never been recorded before.”

The meteorite itself wasn’t terribly large, and is estimated to have only been around 22 pounds.

I have embedded the video of the impact below the fold. It is very short, and the flash is not very impressive, but it still is quite cool.
» Read more

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No Planet X needed

9:11 am

The uncertainty of science: New computer models now suggest that the orbits of the known Kuiper Belt objects can be explained without the need for the theorized large Planet X.

The weirdly clustered orbits of some far-flung bodies in our solar system can be explained without invoking a big, undiscovered “Planet Nine,” a new study suggests.

The shepherding gravitational pull could come from many fellow trans-Neptunian objects (TNOs) rather than a single massive world, according to the research.

“If you remove Planet Nine from the model, and instead allow for lots of small objects scattered across a wide area, collective attractions between those objects could just as easily account for the eccentric orbits we see in some TNOs,” study lead author Antranik Sefilian, a doctoral student in the Department of Applied Mathematics and Theoretical Physics at Cambridge University in England, said in a statement.

When you think about it, having many many scattered small objects in the Kuiper Belt makes much more sense than a few giant planets. Out there, it would be difficult for large objects to coalesce from the solar system’s initial accretion disk. The density of material would be too low. However, you might get a lot of small objects from that disk, which once formed would be too far apart to accrete into larger planets.

The use of the term “Planet Nine” by these scientists however is somewhat annoying, and that has less to do with Pluto and more to do with the general understanding of what it means to be a planet that has been evolving in the past two decades. There are clearly more than eight planets known in the solar system now. The large moons of the gas giants as well as the larger dwarf planets, such as Ceres, have been shown to have all the complex features of planets. And fundamentally, they are large enough to be spheres, not misshaped asteroids.

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Ceres’ bright spots in Occator Crater

9:26 am

Occator Crater bright spot

Cool image time! The Dawn science team has released some additional images taken shortly before the mission’s conclusion when Dawn was in its closest orbit of the dwarf planet Ceres. On the right is a tiny cropped portion of a much larger mosaic of the bright spots on the floor of Occator Crater, focusing on one large bright spot that also includes a fissure cutting across it. If you click on the image you can see the entire mosaic, covering an additional four more bright areas.

The mosaic was taken in June 2018 from a distance of 21 miles.

The press release describes these bright areas as “deposits of salts, in particular sodium carbonate, possibly extruded through fractures connecting the surface to a deep reservoir of salty liquid.” That surely looks confirmed by the fissures in the image to the right.

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Hayabusa-2 to grab asteroid samples in February

9:36 am

The Hayabusa-2 science team has decided that it will make their first attempt to land and grab samples from the asteroid Ryugu in February.

“The time has finally come,” JAXA senior project member Takashi Kubota said at a news conference on Jan. 8. “Two candidate landing spots have their own advantages and drawbacks, but we will robustly try to collect samples.” The two sites are near the equator of the asteroid. JAXA said it will pick one by early February.

Between Feb. 18 and Feb. 23, the Hayabusa 2 will start descending from its “home position” at an altitude of 20 kilometers from the asteroid. JAXA will use “target markers,” which will be dropped on Ryugu beforehand, to guide the probe.

Hayabusa 2 is scheduled to make three touch-and-go landings.

There are clearly risks here, since the asteroid is strewn so completely with rocks and boulders.

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More results from New Horizons

1:42 pm

Today’s press conference did not release any significantly new images. In fact, they did not provide much new information at all. They noted that based on the data obtained so far, they have confirmed that Ultima Thule has no moons closer than 100 miles, or further than 500 miles, but they have not yet gotten the data that looks in that gap.

They created a stereoscopic image using two images produced thirty minutes apart. This helps tell us where the bumps and depressions are on the surface, something that cannot be clearly determined from the first image because the sun was shining directly on it, producing no shadows. From this it appears that the smaller lobe has a very significant bump. More data from New Horizons will have to be downloaded to confirm this.

The reddish color of Ultima Thule places it in the center of a class of Kuiper Belt objects dubbed cold classical objects. This will help them better determine its make-up as more data arrives.

Overall, this press conference was mostly hype. They don’t yet have enough data from the spacecraft, and won’t have it for weeks. I’m therefore puzzled why they bothered today, unless they did it simply to keep the hype up about the mission so as to encourage funding to look for another object to fly past.

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OSIRIS-REx’s first survey of Bennu

8:33 am

The OSIRIS-REx science team has released a short movie of Bennu made up of images taken by the spacecraft’s navigation camera during its preliminary approaches to the asteroid from November 30 to December 31, 2018.

You can watch it here. Because this is the navigation camera, the view is generally from far away. Nonetheless, you can see that during the passes over the north pole, the equator, and the south pole, the asteroid’s entire surface became visible as the asteroid rotated. From this they will be able to use the images taken by the high resolution cameras to create an excellent detailed global.

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“We have a snow-man!”

12:30 pm

Ultima Thule, the snowman

The quote in the headline comes from Alan Stern, the principle scientist for New Horizons, during today’s press conference revealing the first high resolution images of Ultima Thule. The press release for this conference is now online. The image on the right is a reduced cropped version of the main release image today. If you click on it you can see the full resolution version.

The images reveal that Ultima Thule actually is two objects in contact with each other. In addition, the snowman description is apt, as it has a mottled appearance as if it was shaped roughly and somewhat gently over time. Tiny pebbles and rocks softly came together to form two snowballs that then eventually came to touch and join.

They describe this as the most primitive object ever observed. It is also dark, and red in color, like dark reddish dirt.

More images and data is still coming in, to be released in another press conference tomorrow.

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Another image of Ultima Thule

9:47 am

Ultima Thule again

The image on the right was released during this morning’s first briefing outlining the successful confirmation of New Horizons’ fly-by of Ultima Thule (still on-going as I post this). It, along with other data, has provided an explanation for why the scientists have not detected a significant variation in brightness: Our view is looking down at the object’s poles

Images taken during the spacecraft’s approach — which brought New Horizons to within just 2,200 miles (3,500 kilometers) of Ultima at 12:33 a.m. EST — revealed that the Kuiper Belt object may have a shape similar to a bowling pin, spinning end over end, with dimensions of approximately 20 by 10 miles (32 by 16 kilometers). Another possibility is Ultima could be two objects orbiting each other. Flyby data have already solved one of Ultima’s mysteries, showing that the Kuiper Belt object is spinning like a propeller with the axis pointing approximately toward New Horizons. This explains why, in earlier images taken before Ultima was resolved, its brightness didn’t appear to vary as it rotated. The team has still not determined the rotation period.

They note that the highest resolution images will not arrive until February, though they do expect some good images by tomorrow.

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“We have a healthy spacecraft.”

8:44 am

The words above were just announced in the control room for New Horizons. They have confirmation that the spacecraft survived the fly-by of Ultima Thule, and is now ready to begin downloading the data it obtained.

It will take literally a year to get all of that data. They will be holding a first press conference within an hour to outline in greater detail the spacecraft’s status, followed by another briefing at 2 pm Eastern where they will likely release the first images.

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First faint image of Ultima Thule

8:09 am

Ultima Thule, first image

In anticipation of receiving data from the fly-by just past midnight last night, the New Horizons team has released the image above, taken 24 hours earlier.

Just over 24 hours before its closest approach to Kuiper Belt object Ultima Thule, the New Horizons spacecraft has sent back the first images that begin to reveal Ultima’s shape. The original images have a pixel size of 6 miles (10 kilometers), not much smaller than Ultima’s estimated size of 20 miles (30 kilometers), so Ultima is only about 3 pixels across (left panel). However, image-sharpening techniques combining multiple images show that it is elongated, perhaps twice as long as it is wide (right panel). This shape roughly matches the outline of Ultima’s shadow that was seen in observations of the object passing in front of a star made from Argentina in 2017 and Senegal in 2018.

This object is definitely strangely shaped.

New Horizons is traveling fast, which is why we won’t get good images until practically the instant the fly-by happens. And the first downloads from that fly-by are due to arrive within the next two hours. Keep your fingers crossed that the spacecraft operated as programmed and captured Ultima Thule in all its weird glory.

One point about the sad state of journalism these days. Numerous media publications posted stories last night celebrating that fly-by, as if they knew it was a success. This is bunk. We won’t know what happened until this morning. To imply we do is the hallmark of fake news.

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OSIRIS-REx moves into close orbit with Bennu

4:02 pm

OSIRIS-REx has successfully completed an eight second engine burn to place it into a close orbit with the asteroid Bennu.

Now, the spacecraft will circle Bennu about a mile (1.75 kilometers) from its center, closer than any other spacecraft has come to its celestial object of study. (Previously the closest orbit of a planetary body was in May 2016, when the Rosetta spacecraft orbited about four miles (seven kilometers) from the center of the comet 67P/Churyumov-Gerasimenko.) The comfortable distance is necessary to keep the spacecraft locked to Bennu, which has a gravity force only 5-millionths as strong as Earth’s. The spacecraft is scheduled to orbit Bennu through mid-February at a leisurely 62 hours per orbit.

There is a bit of hype here. Other spacecraft have gotten far closer (NEAR, Hayabusa-1, Hayabusa-2) but then retreated for a variety of reasons. What makes this different is the plan to stay this close while they compile detailed data about Bennu’s surface in preparation for touchdown to grab a sample.

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OSIRIS-REx flies over Bennu’s north pole

10:09 am

Bennu's north pole

Cool movie time! OSIRIS-REx has completed its first planned fly-over of Bennu, this time above its north pole, and the science team has released a short movie showing part of that fly-over. I have embedded the movie below the fold.

This series of MapCam images was taken over the course of about four hours and 19 minutes on Dec. 4, 2018, as OSIRIS-REx made its first pass over Bennu’s north pole. The images were captured as the spacecraft was inbound toward Bennu, shortly before its closest approach of the asteroid’s pole. As the asteroid rotates and grows larger in the field of view, the range to the center of Bennu shrinks from about 7.1 to 5.8 miles (11.4 to 9.3 km).

They have four more fly-overs of the asteroid’s poles and equator as they assemble a detailed map of its surface.
» Read more

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New asteroid radar images

12:59 pm

near-Earth asteroid 2003 SD220

Cool radar images! The set of radar images above of near-Earth asteroid 2003 SD220 were created by combining radar data from three different radar telescopes on Earth, Arecibo in Puerto Rico, Green Bank in West Virginia, and Goldstone in California. As the press release notes:

The asteroid will fly safely past Earth on Saturday, Dec. 22, at a distance of about 1.8 million miles (2.9 million kilometers). This will be the asteroid’s closest approach in more than 400 years and the closest until 2070, when the asteroid will safely approach Earth slightly closer.

The radar images reveal an asteroid with a length of at least one mile (1.6 kilometers) and a shape similar to that of the exposed portion of a hippopotamus wading in a river.

The images have a resolution of 12 feet per pixel, so a close look should be able to reveal any large boulders, should they exist. Instead, I see a soft surface that to me resembles the surface of a sand dune, floating unattached to anything in space.

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No rotational light curve from Ultima Thule?

8:55 pm

Data from New Horizons as it is quickly approaching Ultima Thule has found that even though the object is expected to be oblong or even two objects it has shown absolutely no variation in light as it rotates.

Even though scientists determined in 2017 that the Kuiper Belt object isn’t shaped like a sphere – that it is probably elongated or maybe even two objects – they haven’t seen the repeated pulsations in brightness that they’d expect from a rotating object of that shape. The periodic variation in brightness during every rotation produces what scientists refer to as a light curve.

“It’s really a puzzle,” said New Horizons Principal Investigator Alan Stern, of the Southwest Research Institute. “I call this Ultima’s first puzzle – why does it have such a tiny light curve that we can’t even detect it? I expect the detailed flyby images coming soon to give us many more mysteries, but I did not expect this, and so soon.”

They have several theories, all implausible, to explain this. It could be they are looking at the object’s pole. Or maybe a dust cloud or numerous tumbling moons surround the object and hide the light variation.

Fortunately, we shall have an answer to this mystery in less than two weeks, when New Horizons zips past.

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Comparing Ryugu and Bennu

9:30 am

Link here. As much as they are alike, which is not surprising as they both come from the same asteroid family, the article notes the surprising differences.



Both asteroids are also liberally strewn with boulders – a challenge to mission planners on each team, who hope to descend close enough to scoop up samples for return to Earth. “It’s certainly more rugged than we had expected,” Lauretta says. 

But while boulders on Ryugu look to be unpleasantly ubiquitous, Bennu’s terrain is more varied, with more-obvious places where a safe touchdown might be possible. And, Lauretta notes, the OSIRIS-REx spacecraft is only recently arrived.

“We have a long time to explore and make the crucial decisions about where to go,” he says.

The biggest difference has to do with water. Even though scientists believe them to be portions of the same parent body, which broke apart between 800 million and one billion years ago, Bennu appears to be water rich, while Ryugu is less so. Within a week of arrival, infrared spectrometers on OSIRIS-REx were finding evidence of water-bearing minerals, and not just in localised patches. “We saw this in every single one of the spectra we have taken to date,” says Amy Simon, of NASA’s Goddard Space Flight Centre in Greenbelt, Maryland. 

One of the reasons Bennu was chosen as OSIRIS-REx’s target, Lauretta says, was the hope it would be rich in water, and possibly in organic compounds.

The similarities and differences in the samples both spacecraft will bring back will be most revealing.

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New Horizons sees no hazards, will do closest fly-by of Ultima Thule

9:04 am

After three weeks of intense observations and seeing no significant objects orbiting close to the Kuiper Belt object Ultima Thule, the New Horizons team has decided to go for the closest fly-by on January 1, 2019.

After almost three weeks of sensitive searches for rings, small moons and other potential hazards around the object, New Horizons Principal Investigator Alan Stern gave the “all clear” for the spacecraft to remain on a path that takes it about 2,200 miles (3,500 kilometers) from Ultima, instead of a hazard-avoiding detour that would have pushed it three times farther out. With New Horizons blazing though space at some 31,500 miles (50,700 kilometers) per hour, a particle as small as a grain of rice could be lethal to the piano-sized probe.

We should begin to see more detailed images soon. Because of the speed in which New Horizons is traveling, it will not get very close until it is almost on top of Ultima Thule, so the best images will all occur over a very short span of time.

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Saturn’s rings are dying

8:56 am

Using new ground-based observations, scientists now predict that Saturn’s rings are dying at the fastest predicted rate, and will disappear within 300 million years, at the most.

Dr Tom Stallard, Associate Professor in Planetary Astronomy at the University of Leicester and Dr James O’Donoghue, who studied for his PhD at the University of Leicester, have found that Saturn’s rings are dying at the maximum rate estimated from Voyager 1 and 2 observations made decades ago.

The rings of ice are being pulled into Saturn by gravity as particles of ice under the influence of Saturn’s magnetic field. Dr O’Donoghue, who now works at NASA’s Goddard Space Flight Center in Greenbelt, Maryland said: “We estimate that this ‘ring rain’ drains the equivalent of an Olympic-sized swimming pool from Saturn’s rings in half an hour. The entire ring system will be gone in 300 million years.”

Dr O’Donoghue believes that the rings could even disappear quicker than this. “Add to this the Cassini-spacecraft detected ring-material falling into Saturn’s equator, and the rings have less than 100 million years to live.”

Over the decades I have read numerous papers by scientists saying that rings this bright and large must be a relatively short-lived event, and that we are lucky to have seen them. This research only reinforces this conclusion.

At the same time, we do not yet know the frequency or the cause of the events that give rise such bright rings. It could be that such rings are short-lived, but happen frequently enough that it is still not rare to see them in any solar system. And we won’t know this until we get a more complete census of many solar systems, seen up-close.

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