Tag: science

Alan Stern gives the IAU a piece of his mind

9:39 am

New Horizons’ principle investigator yesterday told the International Astronomical Union what he thinks of their definition of a planet:

“It’s bulls—,” he told Tech Insider (and said we could quote him on that).

The problem, Stern said, is that the reclassification largely stemmed from the opinions of astronomers, not planetary scientists. His beef here is that astronomers study a large variety of celestial objects and cosmic phenomena, while planetary scientists focus solely on planets, moons, and planetary systems.

“Why would you listen to an astronomer about a planet?” Stern said. He compared it to going to a podiatrist for brain surgery instead of a brain surgeon. “Even though they’re both doctors, they have different expertise,” Stern said. “You really should listen to planetary scientists that know something about this subject. When we look at an object like Pluto, we don’t know what else to call it.”

Stern’s opinion is not unique among planetary scientists. I have interviewed many, and read reports by others, which consistently say that they object strongly to the IAU’s definition. To them, if a object has enough mass to force it into a sphercial shape, it is a planet.

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Philae results published

9:32 am

Cool image time! The Philae science team yesterday published in Science a set of papers describing their results from the lander’s approach and bouncing landing on Comet 67P/C-G.

Data were obtained during the lander’s seven-hour descent to its first touchdown at the Agilkia landing site, which then triggered the start of a sequence of predefined experiments. But shortly after touchdown, it became apparent that Philae had rebounded and so a number of measurements were carried out as the lander took flight for an additional two hours some 100 m above the comet, before finally landing at Abydos.

Some 80% of the first science sequence was completed in the 64 hours following separation before Philae fell into hibernation, with the unexpected bonus that data were ultimately collected at more than one location, allowing comparisons between the touchdown sites.

The images from lander so far released show the approach to the first site, with one boulder getting larger and larger as it descends, followed by images at the final landing site, showing a fractured, uneven, and very rough surface with the lander apparently sitting sideways with one foot off the ground.

An animation of the first touchdown, created by these images, can be viewed here.

Update: A good summary of the results can be read here.

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The supernova of 1987 finally begins to fade

7:32 pm

Almost thirty years after Supernova 1987a became the first naked eye supernova since the invention of the telescope, the necklace ring of spots that the explosion’s shockwave ignited in the late 1990s are finally beginning to fade.

But now the hotspots have slowly begun to fade, Claes Fransson (Stockholm University, Sweden) and colleagues report in the June 10th Astrophysical Journal Letters. The team studied images taken by the Hubble Space Telescope from 1994 to 2014, and spectra from the Very Large Telescope spanning 2000 to 2013. Based on the rate at which the hotspots are fading, the researchers predict the glittering necklace will fade away sometime between 2020 and 2030, with the calculations favoring closer to 2020. The clumps of gas in the central ring are likely dissolving, thanks to a combination of instabilities and conduction in the hot gas surrounding the clumps. In other words, the central ring is being destroyed.

The show really isn’t over. The aftermath of a star exploding goes on for thousands of years. So to will SN1987a’s show.

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Astronomers confirm existence of Earthlike exoplanet 21 light years away

12:22 pm

Worlds without end: Astronomers have confirmed the existence of a rocky Earthlike exoplanet only 21 light years away.

HD 219134b is also the closest exoplanet to Earth to be detected transiting, or crossing in front of, its star and, therefore, perfect for extensive research. “Transiting exoplanets are worth their weight in gold because they can be extensively characterized,” said Michael Werner, the project scientist for the Spitzer mission at NASA’s Jet Propulsion Laboratory in Pasadena, California. “This exoplanet will be one of the most studied for decades to come.”

The planet has a mass 4.5 times that of Earth, and orbits its sun every three days, which means it is not likely to harbor life. Its sun also harbors three other small exoplanets, but little is known of them.

Expect a lot more news coming from HD 219134b, however. With transits every three days, astronomers are going to have a lot of opportunities to study its atmosphere and make-up.

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Counting bats on a Saturday evening

8:00 am

While most normal people spend their Saturday evenings going out to dinner followed by either a movie or a show, I spent this past Saturday doing something entirely different: counting bats!

There is a local cave here in the Tucson area that is a maternity colony for one species of bats. During the summer the females gather here to gossip and then give birth to their babies, after which they move on until next year. Because of a desire to help these bats, a few years ago the managers of the cave decided to close it during the summer months. This way humans wouldn’t be there to disturb the mothers during their labor.

The managers also decided to do regular bat counts of the bats leaving the cave each evening to feed, in order to get an estimate of the population size. To everyone’s delight they found the numbers rising year-to-year, following the summer closure. The total population of bats isn’t actually going up, but it appears that bats are finding this cave to be a good place to give birth, so more and more of them are making it their summer residence.

In the end the situation will contribute to an actual rise in population, as providing the maternity colony a safe haven will allow for more successful births and more babies.

In the past three years the bat count numbers over each summer would exhibit a typical bell curve, going up and then declining as the summer progressed, with the largest numbers ranging between 75 to 150 each night. However, last year there was one evening in which no bats left the cave. The bat biologist leading the bat count, Sandy Wolf, has theorized that this might be because the mothers are synchronizing their labor so that everyone gives birth at the same time and, because of that, on that night no one exits for feeding.. She knows that some species do this, but for this particular species such behavior has never been documented.

Anyway, she decided to find out. This has required that someone be at the entrance counting the bats at least every other evening. (In past years the counts were only done about once a week.) This has required more help, and thus Sandy has called for volunteers to do the work.

And that is how I and fellow caver Jerry Isaman ended up hiking up the hill to the cave with digital camera, infrared lights, and monitor this past Saturday.

» Read more

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Puzzling red arcs on the Saturn moon Tethys

10:44 am

Red arcs on Tethys

Baffling image time! Images taken in April 2015 by Cassini of the Saturn moon Tethys have produced the best images yet of the puzzling red arcs on the moon’s surface, first identified in 2004.

The origin of the features and their reddish color is a mystery to Cassini scientists. Possibilities being studied include ideas that the reddish material is exposed ice with chemical impurities, or the result of outgassing from inside Tethys. They could also be associated with features like fractures that are below the resolution of the available images.

Except for a few small craters on Saturn’s moon Dione, reddish-tinted features are rare on other moons of Saturn. Many reddish features do occur, however, on the geologically young surface of Jupiter’s moon Europa. “The red arcs must be geologically young because they cut across older features like impact craters, but we don’t know their age in years.” said Paul Helfenstein, a Cassini imaging scientist at Cornell University, Ithaca, New York, who helped plan the observations. “If the stain is only a thin, colored veneer on the icy soil, exposure to the space environment at Tethys’ surface might erase them on relatively short time scales.”

I could also file this under “the uncertainty of science”, as the scientists at this point haven’t the slightest idea what created these arcs.

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How Comet 67P/C-G interacts with the solar wind

9:19 am

Accumulating data from Rosetta is now giving scientists an excellent picture of how this comet interacts with the solar wind as it moves in towards its closest approach to the Sun.

They have seen that the number of water ions – molecules of water that have been stripped of one electron – accelerated away from the comet increased hugely as 67P/C-G moved between 3.6AU (about 538 million km) and 2.0AU (about 300 million km) from the Sun. Although the day-to-day acceleration is highly variable, the average 24-hour rate has increased by a factor of 10,000 during the study, which covered the period August 2014 to March 2015.

The water ions themselves originate in the coma, the atmosphere of the comet. They are placed there originally by heat from the Sun liberating the molecules from the surface ice. Once in gaseous form, the collision of extreme ultraviolet light displaces electrons from the molecules, turning them into ions. Colliding particles from the solar wind can do this as well. Once stripped of some of their electrons, the water ions can then be accelerated by the electrical properties of the solar wind.

Not all of the ions are accelerated outwards, some will happen to strike the comet’s surface. Solar wind particles will also find their way through the coma to hit home. When this happens, they cause a process called sputtering, in which they displace atoms from material on the surface – these are then ‘liberated’ into space.

There’s more at the link, including animations and simulations.

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New Pluto data released

11:54 am

Pluto

Cool image time! During today’s New Horizons’ press conference, principal investigator Alan Stern noted that only 4%-5% of the data has been recovered. They have finished first phase of download and are moving into second phase, which will be dominated by engineering and other data, not images. So, for the next couple of months they will only be able to release images once and awhile. Beginning in September images, however, they will begin downloading images at a much faster pace.

Some results from today:
» Read more

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Worlds without end

1:01 pm

Last week’s fly-by of Pluto by New Horizons illustrated forcefully once again the power of exploration on the human mind, and how that exploration always carries surprises that delight and invigorate us.

First of all, the images from that fly-by demonstrated clearly that the decision by the International Astronomical Union (IAU) to declare Pluto a non-planet was very much premature. Even project scientist Alan Stern himself enthusiastically noted at the start of Friday press conference that Pluto-Charon was a “double planet system”.

The IAU definition itself was faulty and difficult to apply. The clause that required a planet to have “cleared the neighborhood around its orbit” made little sense in the real universe, as even the Earth has not successfully cleared its orbit after several billion years. Was the IAU suggesting the Earth was not a planet?

New Horizons’s discovery last week that even a small object like Pluto, orbiting the Sun on its own with no gas giant nearby to provide tidal heating, can still exhibit significant and on-going geological activity, shows that our understanding of what defines a planet is at this time quite limited. We simply don’t know enough about planetary evolution and formation to definitively define the term. Nor do we have enough knowledge to determine if Pluto falls into that category, though the data strongly suggests that it does.

Are planets made up of only gas giants, rocky terrestrial planets like the Earth, and dwarf planets like Ceres and Pluto? Or are there numerous other as yet unknown categories?
» Read more

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Astronomers confirm Kepler discovery of near twin of Earth

10:08 am

Worlds without end! In the release today of another set of Kepler data, astronomers have announced the discovery in that dataset of a new twin of Earth.

The newly discovered Kepler-452b is the smallest planet to date discovered orbiting in the habitable zone — the area around a star where liquid water could pool on the surface of an orbiting planet — of a G2-type star, like our sun. The confirmation of Kepler-452b brings the total number of confirmed planets to 1,030. …

Kepler-452b is 60 percent larger in diameter than Earth and is considered a super-Earth-size planet. While its mass and composition are not yet determined, previous research suggests that planets the size of Kepler-452b have a good chance of being rocky. While Kepler-452b is larger than Earth, its 385-day orbit is only 5 percent longer. The planet is 5 percent farther from its parent star Kepler-452 than Earth is from the Sun. Kepler-452 is 6 billion years old, 1.5 billion years older than our sun, has the same temperature, and is 20 percent brighter and has a diameter 10 percent larger.

While this exoplanet is certainly not identical to Earth, it is close enough that the possibility of alien life — really alien life — could very likely exist upon it.

The dataset also included 11 other Earth twin candidate exoplanets that still need to be confirmed.

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Haze spotted over Ceres’ double bright spot

9:15 am

Dawn, in orbit around Ceres, has detected a haze above the dwarf planet’s double bright spot, suggesting that the tiny asteroid/planet is still geologically active.

Haze on Ceres would be the first ever observed directly in the asteroid belt. In 2014, researchers using the European Space Agency’s Herschel Space Observatory reported seeing water vapour spraying off Ceres, which suggested that it was geologically active1. At least one-quarter of Ceres’s mass is water, a much greater proportion than seen in most asteroids.

Bright spots pepper Ceres’s surface, but the haze has so far been seen in only one location — a crater named Occator, which has a large bright area at its centre and several smaller spots nearby. Mission scientists have been trying to work out whether the bright spots are made of ice, evaporated salts or other minerals, or something else entirely.

Some team members had been leaning towards the salt explanation, but the discovery of haze suggests the presence of sublimating ice. “At noontime, if you look at a glancing angle, you can see what seems to be haze,” Russell says. “It comes back in a regular pattern.” The haze covers about half of the crater and stops at the rim.

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Mountains and craters on Pluto?

9:09 am

The edge of Tombaugh Regio

Cool image time! Even as they download new images for a press conference on Friday, the New Horizons’ science team has released a new close-up of Tombaugh Regio, showing both a new mountain range within it as well as its sharply defined western contact with the dark whale feature, which now appears to be heavily cratered and old.

“There is a pronounced difference in texture between the younger, frozen plains to the east and the dark, heavily-cratered terrain to the west,” said Jeff Moore, leader of the New Horizons Geology, Geophysics and Imaging Team (GGI) at NASA’s Ames Research Center in Moffett Field, California. “There’s a complex interaction going on between the bright and the dark materials that we’re still trying to understand.” While Sputnik Planum is believed to be relatively young in geological terms – perhaps less than 100 million years old — the darker region probably dates back billions of years. Moore notes that the bright, sediment-like material appears to be filling in old craters (for example, the bright circular feature to the lower left of center).

Make sure you click through to see the full resolution image. It is quite astonishing. They have also released a new image each of two of Pluto’s moons.

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Iran’s parliament questioning Iran nuclear deal

11:24 am

Democracy in action! Iran’s parliament is likely to demand changes to Iran deal before voting for its approval.

The ironies here are tragic. While their parliament stands up for its constitutional rights, our Congress, run by Republicans, has ceded its power to the President, with the Senate giving up its constitutional right to only approve treaties with a two-third majority. Instead, they got down on their knees and handed Obama the power to make this very bad treaty without their full consent. What idiots.

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Internet tycoon commits $100 million to alien life search

9:16 am

Russian internet entrepreneur Yuri Milner has given SETI $100 million for a ten year project to accelerate their effort to search for evidence of extraterrestrial life.

Understanding why SETI needs private funding is important:

SETI has been going on since 1960, when radio telescopes became sensitive enough to detect signals from another planet if it was broadcasting signals similar to those which our civilization does. Researchers developed devices that could monitor millions of frequencies at once for any signal that looked at all different from that produced by astronomical objects or the natural background. At first funded by universities and NASA, public funding for SETI was axed by Congress in the early 1990s. Since then, the nonprofit SETI League has received funding of a few million dollars a year from private donors.

Congress correctly cut the funds because it isn’t really the business of the federal government to search for alien life. Some taxpayers really don’t want their money used for that purpose, and they should have the right to say no. Instead, Congress essentially told SETI to do it right: Get private funding from people who want the research done. The work will be done more efficiently for less, and no one will be required to contribute who doesn’t want to.

Milner’s contribution now is the biggest donation yet, and suggests that interest in this research is building culturally.

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Philae status update

9:01 am

Engineers on the Rosetta team are struggling to figure out why they cannot get a solid communications lock with their Philae lander, and have come up with several explanations.

One possible explanation being discussed at DLR’s Lander Control Center is that the position of Philae may have shifted slightly, perhaps by changing its orientation with respect to the surface in its current location. The lander is likely situated on uneven terrain, and even a slight change in its position – perhaps triggered by gas emission from the comet – could mean that its antenna position has also now changed with respect to its surroundings. This could have a knock-on effect as to the best position Rosetta needs to be in to establish a connection with the lander.

Another separate issue under analysis is that one of the two transmission units of the lander appears not to be working properly, in addition to the fact that one of the two receiving units is damaged. Philae is programmed to switch periodically back and forth between these two transmission units, and after tests on the ground reference model, the team has sent a command to the lander to make it work with just one transmitter. As Philae is able to receive and accept commands of this kind in the “blind”, it should execute it as soon as it is supplied with solar energy during the comet’s day.

They have heard from Philae since July 9. Because of comet activity they have had to pull Rosetta back away from the nucleus to protect it, and are now focusing its primary activity on observations, not communications with Philae. They will continue to try to bring Philae back to full functioning life, but the priority is now the comet.

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Dawn resumes descent to Ceres

11:45 pm

After a several week pause while engineers analyzed the issue that caused the spacecraft to go into safe mode on June 30, they have now resumed their descent to a lower orbit to take higher resolution images of Ceres.

The spacecraft experienced a discrepancy in its expected orientation on June 30, triggering a safe mode. Engineers traced this anomaly to the mechanical gimbal system that swivels ion engine #3 to help control the spacecraft’s orientation during ion-thrusting. Dawn has three ion engines and uses only one at a time. Dawn’s engineering team switched to ion engine #2, which is mounted on a different gimbal, and conducted tests with it from July 14 to 16. They have confirmed that the spacecraft is ready to continue with the exploration of Ceres.

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More Pluto news!

10:36 am

Sputnik Planum on Pluto

At a press conference today Alan Stern led off by dubbing Pluto-Charon as a “double planet system”. Some new results:

  • Tombaugh Regio (the heart) has been identified as a region of carbon monoxide.
  • The atmosphere extends out to about 600 miles. It is comprised of hydrocarbosn, methane, and nitrogen, with nitrogen the main component. It is naturally escaping from the planet, ionized by the solar wind. The consequence is that a substantial amount of Pluto has evaporated away over time. The numbers are not yet quantified, but will be as more data arrives.
  • The images once again suggest significant activity over time, both of erosion and tectonic processes. One flat plain, dubbed Sputnik Planum, is what one scientist described as “difficult to explain terrain.” The image is to the right. Some of its features resemble icecap glaciers, which are formed by processes that do not exist on Pluto. There also appear to be wind streaks on this planum!
  • They have named a mile high mountain has been dubbed Norgay Montes after the man who accompanied Edmund Hillary to the summit of Mt. Everest.

As the scientists warned today, every conclusion right now is very speculative, and should be taken with a very big grain of salt.

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Weird geology on Charon

12:57 pm

Charon's mountain in a moat

As they await the arrival of more data from New Horizons, the science team have highlighted this interesting and entirely puzzling feature revealed in their first global image from Charon, shown in the image on the right, a mountain inside a depression. Note also the nearby rill-like depressions running from one crater to the next.

My first thought is that the mountain, which in this relatively low resolution image looks almost like a really gigantic boulder, is made of material denser than the ground in which it sits, and some heating event caused the ground to soften and collapse, dropping the mountain-sized boulder down into the sinkhole.

I am guessing of course. What we have here is a very alien environment, with geological processes in temperatures and densities and gravities to which we are wholly unfamiliar. What we would normally expect to happen is not something we should expect to normally happen on either Charon or Pluto.

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Growing and eating lettuce on ISS

8:59 am

Astronauts are about to eat a crop of romaine lettuce that they have grown entirely from seed on ISS.

The story is important as it indicates that the engineering to grow plants in space is continuing to improve. The article however is very wrong when it says that this will be the first salad grown and eaten in space. Russian astronauts have been working on this problem on their space stations since the 1970s, and in at least one case — which was captured on video almost a decade ago — have eaten space-grown lettuce. (I wrote about this event for Air & Space back in 2003.)

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Astronomers find exoplanet twin of Jupiter

4:03 pm

Worlds without end: Astronomers have discovered an exoplanet with the same mass as Jupiter orbiting its star in a very similar orbit.

Not only that, but:

The planet’s host, the solar twin HIP 11915, is not only similar in mass to the Sun, but is also about the same age. To further strengthen the similarities, the composition of the star is similar to the Sun’s. The chemical signature of our Sun may be partly marked by the presence of rocky planets in the Solar System, hinting at the possibility of rocky planets also around HIP 11915.

I immediately wonder if this star also has rocky inner planets.

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First New Horizons fly-by images released

12:31 pm

Ice mountains on Pluto

Many cool images! I will only post one, on the right, of the ice mountains seen at the southernmost edge of Tombauh Regio. More can be seen here.

Some quick facts revealed during today’s the press conference:

  • They have gotten good data on Pluto’s atmosphere. Earlier data just before fly-by suggested that there are specific regions on the surface that have a lot of methane, but with different properties depending on location.
  • They have found that the surface of Charon is active. It also looks like a weird Moon, cratered, with a dark mare region they have dubbed Mordor. Its cause however is not the same as the Moon. There are also a large sequence of troughs and cliffs that are unlike other planets. Some areas are very smooth, as they they have been repaved after cratering. And there is a canyon that is very very deep, 3 miles deep, that makes it relatively deeper than any other canyon in the solar system.
  • Pluto’s moon Hydra is not spherical, and in fact looks like an asteroid.
  • The white heart is now been named Tombaugh Regio after one of Pluto’s discoverers. In its southern extent there are mountains and strange pits. And this area has no impact craters, meaning this is a very young surface, less than 100 million years old. The mountains have to made of ice, which is essentially the only thing that can be bedrock at Pluto’s temperatures, based on what they think Pluto is composed of.
  • The data shows repeatedly that a tiny planet can still have geological activity after billions of years, even without a giant gas giant nearby to produce tidal heating.
  • They have named the giant whale-shaped dark region at the equator Cthulu Regio.

The data and images will be coming back from New Horizons for the next year, so the show is certainly not over.

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“We are in lock with telemetry with the spacecraft!”

5:56 pm

The quote above was a confirmation from mission control that New Horizons survived the fly-by and is functioning perfectly.

They are still confirming if everything is A-Okay, but so far everything appears to exactly that. People are very jubilant at mission control.

They got the signal early, at the very beginning of their window.

They have now confirmed that they have a healthy spacecraft, and that “They are outbound from Pluto.”

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Pluto and Charon in false color

5:03 pm

Pluto and Charon in false color

While waiting for word about how New Horizons has fared during its close fly-by of Pluto, the science team today released the false color images on the right of both Pluto and Charon to illustrate the complicated surface geology of both planetary bodies.

The new color images reveal that the “heart” of Pluto actually consists of two remarkably different-colored regions. In the false-color image, the heart consists of a western lobe shaped like an ice cream cone that appears peach color in this image. A mottled area on the right (east) side looks bluish. A mid-latitude band appears in shades ranging from pale blue through red. Even within the northern polar cap, in the upper part of the image, various shades of yellow-orange indicate subtle compositional differences. This image was obtained using three of the color filters of the Ralph instrument on July 13 at 3:38 am EDT and received on the ground on at 12:25 pm.

The surface of Charon is viewed using the same exaggerated color. The red on the dark northern polar cap of Charon is attributed to hydrocarbon and other molecules, a class of chemical compounds called tholins. The mottled colors at lower latitudes point to the diversity of terrains on Charon. This image was obtained using three of the color filters of the Ralph instrument on July 13 at 3:38 am EDT and received on the ground on at 12:25 pm.

Word on the spacecraft’s status will arrive at around 9 pm (eastern) tonight. Images and data will then follow, assuming all is well.

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Some speculations from scientists about Pluto data

10:28 am

Using the images and data so far received from New Horizons, planetary scientists outline some of their tentative conclusions as well as speculate about what it means.

[Alan Stern, New Horizons’ principal investigator] says Pluto’s surface appears to be much less heavily cratered than its large moon, Charon—which implies that the surface has been paved over in some way. That smoothing process could come from internal heat that keeps rock and ice soft, or by the frosts that snow down and blanket the surface in fresh ice. “Either [Pluto’s] internal engine continues to run, and there are active processes that are taking place,” Stern says, “or those atmospheric processes are themselves covering up the geology, and covering up the craters.”

Jonathan Lunine, a planetary scientist at Cornell University, not on the New Horizons team, favors the latter explanation. His initial impression is that Pluto is far more cratered than Triton, the moon of Neptune that is about the same size as Pluto and is thought to be a captured Kuiper belt object. Triton has a famous “cantaloupe” terrain, thought to have formed as heat, driven by Saturn’s tidal pull, allowed molten blobs of ice to rise and overturn. Parts of Pluto’s rugged surface seem to be far more carved and cratered, Lunine says. “It’s telling me that [Pluto’s] crust was not heated and modified to the extent that it was on Triton.”

Above all, however, I like Lunine’s comment at the end of the article:

Lunine says the emerging diversity on Pluto—of both active atmospheric and geological processes—makes him disagree with the decision of International Astronomical Union to call Pluto a dwarf. “This really is a planet,” he says. He notes that electrons have a double definition as a particle and a wave. “Why can’t we call Pluto a planet and a Kuiper belt object?” he asks. “I think we have to think of it as both.”

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Pluto just before close encounter

9:39 am

Pluto just before close encounter

Today’s cool image, on the right, is the last one New Horizons sent back to Earth before its July 14th close encounter. Be sure you click here to see the full resolution version. It is quite spectacular. It was taken from about 476,000 miles, about twice the distance to the Moon.

The quality of this image strongly suggests that all will go well with the encounter today. However,

Per the plan, the spacecraft currently is in data-gathering mode and not in contact with flight controllers at the Johns Hopkins University Applied Physical Laboratory (APL) in Laurel, Maryland. Scientists are waiting to find out whether New Horizons “phones home,” transmitting to Earth a series of status updates that indicate the spacecraft survived the flyby and is in good health. The “call” is expected shortly after 9 p.m. tonight.

So, at 9 pm (Eastern) we will hear from New Horizons on its status. Images and data from the encounter itself however will arrive over time, beginning tonight and continuing throughout the coming months.

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The size of Pluto pinned down

12:59 pm

Data from New Horizons has allowed scientists to more firmly determine, for the first time, Pluto’s precise size.

Mission scientists have found Pluto to be 1,473 miles (2,370 kilometers) in diameter, somewhat larger than many prior estimates. Images acquired with the Long Range Reconnaissance Imager (LORRI) were used to make this determination. This result confirms what was already suspected: Pluto is larger than all other known solar system objects beyond the orbit of Neptune. “The size of Pluto has been debated since its discovery in 1930. We are excited to finally lay this question to rest,” said mission scientist Bill McKinnon, Washington University, St. Louis.

Pluto’s newly estimated size means that its density is slightly lower than previously thought, and the fraction of ice in its interior is slightly higher. Also, the lowest layer of Pluto’s atmosphere, called the troposphere, is shallower than previously believed.

This means that Pluto is at this moment the largest Kuiper Belt object so far known, bigger than Eris, the Kuiper Belt planet discovered in 2005 that had been thought to be bigger than Pluto and whose existence was used by some to demote Pluto’s status as a planet.

I say, they are both planets, because they are both heavy enough for gravity to have forced them to become spherical.

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The approaching perihelion of Comet 67P/C-G

9:08 am

The Rosetta science team has prepared a FAQ outlining what we should expect next month as Comet 67P/C-G reaches and passes its closest point to the Sun, with Rosetta (and hopefully Philae) there to watch.

The most interesting detail they note is this:

Will the comet break apart during perihelion?

The comet has not broken apart during its many previous orbits, so it is not expected to do so this time, but it cannot be ruled out. Scientists are keen to watch the possible evolution of a 500 m-long fracture that runs along the surface of the neck on the comet during the peak activity.

You can see an image from Rosetta that shows this fracture here. As I wrote then,

The biggest fracture line appears to be a meandering line that is traveling from the image’s top center to its mid-right. There also appear to be parallel lines below it. As we are looking at the nucleus’s neck, these lines suggest that the connection between the two large lobes is somewhat strained, and that it is not unlikely that these two sections will break apart at some time in the future. Though there is no way to predict at this time when that will happen, it will be truly exciting if it happens when Rosetta is in the neighborhood.

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