Asteroids Archives

March 12, 2014December 23, 2015 by Brian Koberlein

Why the Asteroid Belt Doesn’t Threaten Spacecraft

Artist's impression of the asteroid belt. Image credit: NASA/JPL-Caltech

When you think of the asteroid belt, you probably imagine a region of rock and dust, with asteroids as far as the eye can see. Such a visual has been popularized in movies, where spaceships must swerve left and right to avoid collisions. But a similar view is often portrayed in more scientific imagery, such as the artistic rendering above. Even the first episode of the new Cosmos series portrayed the belt as a dense collection of asteroids. But the reality is very different. In reality the asteroid belt is less cluttered than often portrayed. Just how much less might surprise you.

The Sloan digital sky survey (SDSS) has identified more than 100,000 asteroids in the solar system. Not all of these lie within the asteroid belt, but there are about 80,000 asteroids in the belt larger than a kilometer. Of course there are asteroids smaller than that, but they are more difficult to detect, so we aren’t exactly sure how many there are.

The pyramid-shaped zodiacal light cone is centered on the same path the sun and planets take across the sky called the ecliptic. This map shows the sky 90 minutes after sunset in early March facing west. Created with Stellarium

We have a pretty good idea, however, because the observations we have indicate that the size distribution of asteroids follows what is known as a power law distribution. For example, with a power law of 1, for every 100-meter wide asteroid there would be 10 with a diameter of 10 meters and 100 with a diameter of 1 meter. Based upon SDSS observations, asteroids seem to follow a power law of about 2, which means there are likely about 800 trillion asteroids larger than a meter within the belt. That’s a lot of rock. So much that sunlight scattering off the asteroid belt and other dust in the solar system is the source of zodiacal light.

But there is also a lot of volume within the asteroid belt. The belt can be said to occupy a region around the Sun from about 2.2 to 3.2 times the distance from the Earth to the Sun from the Sun (AU), with a thickness of about 1 AU. A bit of math puts that at about 50 trillion trillion cubic kilometers. So even though there are trillions of asteroids, each asteroid has billions of cubic kilometers of space on average. The asteroid belt is hardly something you would consider crowded. It should be emphasized that asteroids in the belt are not evenly distributed. They are clustered into families and groups. But even such clustering is not significant compared to the vast space it occupies.

An actual image from within the asteroid belt, taken from the NEAR probe as it was heading toward Eros (center). Credit: NASA — An actual image from within the asteroid belt, taken from the NEAR probe as it was heading toward Eros (center).
Credit: NASA

You can even do a very rough calculation to get an idea of just how empty the asteroid belt actually is. If we assumed that all the asteroids lay within a single plane, then on average there is 1 asteroid within an area roughly the size of Rhode Island. Within the entire United States there would be about 2000 asteroids, most of them only a meter across. The odds of seeing an asteroid along a cross-country road trip, much less hitting one, would be astoundingly small. So you can see why we don’t worry about space probes hitting an asteroid on their way to the outer solar system. In fact, to get even close to an asteroid takes a great deal of effort.

March 7, 2014December 29, 2015 by Fraser Cain

Weekly Space Hangout – March 7, 2014: Cosmos Premiere & NASA Budget

Host: Fraser Cain
Astrojournalists: David Dickinson, Matthew Francis, Casey Dreier, Jason Major, Brian Koberlein, Alan Boyle

This week’s stories:

Alan Boyle (@b0yle, cosmiclog.com ):
Cosmos premiere!

David Andrew Dickinson (@astroguyz):
Watch the Close Pass of NEO 2014 DX110
Daylight Saving time: A Spring Forward or a Step Back?
A Natural Planetary Defense Against Solar Storms

Matthew Francis (@DrMRFrancis, BowlerHatScience.org):
Using gravitational lensing to measure a spinning quasar
CosmoAcademy classes

Casey Dreier (Planetary.org):
The 2015 NASA Budget Request
NASA Kinda Embraces Exploring Europa

Jason Major (@JPMajor, LightsInTheDark.com):
That’s the way the asteroid crumbles

Brian Koberlein (@briankoberlein, briankoberlein.com):
*Possible* evidence for dark matter WIMPs
Black Holes exceed Eddington limit
Using quasars in a quantum experiment

We record the Weekly Space Hangout every Friday at 12:00 pm Pacific / 3:00 pm Eastern. You can watch us live on Google+, Universe Today, or the Universe Today YouTube page.

March 6, 2014December 23, 2015 by Nancy Atkinson

Hubble Telescope Watches Asteroid Disintegrate in Space

This series of images shows the asteroid P/2013 R3 breaking apart, as viewed by the NASA/ESA Hubble Space Telescope in 2013. This is the first time that such a body has been seen to undergo this kind of break-up. Credit: NASA, ESA, D. Jewitt (UCLA).

Back in 2010, astronomers discovered an asteroid that was breaking apart due to a head-on collision with another asteroid. But now they have seen an asteroid break apart – with no recent collision required.

Asteroid P/2013 R3 appears to be crumbling apart in space, and astronomers using the Hubble Space Telescope recently saw the asteroid breaking into as many as 10 smaller pieces. The best explanation for the break-up is the Yarkovsky–O’Keefe–Radzievskii–Paddack (YORP) effect, a subtle effect from sunlight that can change the asteroid’s rotation rate and basically cause a rubbly-type asteroid to spin apart.

“This is a really bizarre thing to observe — we’ve never seen anything like it before,” said co-author Jessica Agarwal of the Max Planck Institute for Solar System Research, Germany. “The break-up could have many different causes, but the Hubble observations are detailed enough that we can actually pinpoint the process responsible.”

Astronomers first noticed this asteroid on September 15, 2013 and it appeared as a weird, fuzzy-looking object, as seen by the Catalina and Pan-STARRS sky-survey telescopes. A follow-up observation on Oct. 1 with the W.M. Keck telescope on Hawaii’s Mauna Kea revealed three co-moving bodies embedded in a dusty envelope that is nearly the diameter of Earth.

Then on October 29, 2013, astronomers used the Hubble Space Telescope to observe the object and saw there were actually 10 embedded objects, each with comet-like dust tails. The four largest rocky fragments are up to 200 meters/yards in radius, about twice the length of a football field.

The Hubble data showed that the fragments are drifting away from each other at a leisurely pace of 1.6 km/hr (one mile per hour), which would be slower than a strolling human.

“Seeing this rock fall apart before our eyes is pretty amazing,” said David Jewitt, from UCLA’s Department of Physics and Astronomy, who led the investigation.

The slowness of the speed at which the pieces are coming apart makes it unlikely that the asteroid is disintegrating because of a collision. That would be instantaneous and violent, with the pieces traveling away from each other at much higher speeds.

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Jewitt also said the asteroid is not coming unglued due to the pressure of interior ices warming and vaporizing, like comets do as they approach the Sun. The asteroid is too cold for ices to significantly sublimate, and it has presumably maintained its nearly 480 million-km (300 million–mile) distance from the Sun for much of its life.

Jewitt described the YORP torque effect as like grapes on a stem being gently pulled apart due to centrifugal force of an unusually shaped asteroid as it speeds up in its spin. This effect occurs when light from the Sun is absorbed by a body and then re-emitted as heat. When the shape of the emitting body is not perfectly regular, more heat is emitted from some regions than others. This creates a small imbalance that causes a small but constant torque on the body, which changes its spin rate. This effect has been discussed by scientists for several years but, so far, never reliably observed.

For the break-up to happen, P/2013 R3 must have a weak, fractured interior, probably as the result of previous but ancient collisions with other asteroids. Most small asteroids, in fact, are thought to have been severely damaged in this way, giving them a “rubble pile” internal structure. P/2013 R3 itself is probably the product of collisional shattering of a bigger body some time in the last billion years.

With Hubble’s recent discovery of an a different active asteroid spouting six tails (P/2013 P5), astronomers are seeing more circumstantial evidence that the pressure of sunlight may be the primary force that disintegrates small asteroids (less than a mile across) in the Solar System.

The asteroid’s remnant debris, estimated at weighing in at 200,000 tons, in the future will provide a rich source of meteoroids, Jewitt said. Most will eventually plunge into the sun, but a small fraction of the debris may one day enter the Earth’s atmosphere to blaze across the sky as meteors, he said.

The discovery is published online March 6 in Astrophysical Journal Letters. A preprint of the paper can be found here.

Sources: UCLA, Hubble ESA

February 24, 2014December 23, 2015 by Nancy Atkinson

Watch a Car-Sized Asteroid Slam Into the Moon

An image of the flash resulting from the impact of a large meteorite on the lunar surface on 11 September 2013, obtained with the MIDAS observatory. Credit: J. Madiedo / MIDAS

Hey, all you astro-photographers/videographers out there: were you shooting the Moon back on September 11, 2013? You may want to review your footage and see if you captured a bright flash which occurred at about 20:07 GMT. Astronomers say a meteorite with the mass of a small car slammed into the Moon at that time and the impact produced a bright flash, and it even would have been easy to spot from the Earth.

According to astronomers Jose M. Madiedo, from the University of Huelva and Jose L. Ortiz, from the Institute of Astrophysics of Andalusia both in Spain, this impact was the longest and brightest confirmed lunar impact flash ever observed, as the “afterglow” of the impact remained visible for 8 seconds.

The astronomers think the bright flash was produced by an impactor of around 400 kg with a width of between 0.6 and 1.4 meters. The rock hit may have hit Mare Nubium at about 61,000 kilometers per hour (38,000 miles per hour) — although the uncertainty of the impact is fairly high, the team says in their paper. But if it is as high as they think, it may have created a new crater with a diameter of around 40 meters. The impact energy was equivalent to an explosion of roughly 15 tons of TNT.

This beats the previous largest impact seen – which occurred just six months earlier in March 2013 – which was estimated to pack as much punch as 5 tons of TNT. Astronomers that explosion was caused by a 40 kg meteoroid measuring 0.3 to 0.4 meters wide, traveling about 90,000 km/hr (56,000 mph.)

How often does an asteroid hit the Moon? Astronomers actually aren’t very sure.

On average, 33 metric tons (73,000 lbs) of meteoroids hit Earth every day, the vast majority of which harmlessly ablates or burns up high in Earth’s atmosphere, never making it to the ground. The Moon, however, has little or no atmosphere, so meteoroids have nothing to stop them from striking the surface.

The lunar impact rate is so uncertain because observations for objects in the mass range of visible impacts from Earth are quite few. But now, astronomers have set up networks of telescopes that can detect them automatically. NASA has the Automated Lunar and Meteor Observatory (ALaMO) at Marshall Space Flight Center, and the Spanish telescopes are part of the Moon Impacts Detection and Analysis System (MIDAS) system.

Lunar meteors hit the ground with so much kinetic energy that they don’t require an oxygen atmosphere to create a visible explosion. The flash of light comes not from combustion but rather from the thermal glow of molten rock and hot vapors at the impact site.

This thermal glow can be detected from Earth as short-duration flashes through telescopes. Generally, these flashes last just a fraction of a second. But the flash detected on September 11, 2013 was much more intense and longer than anything observed before.

Mosaic of zoomed images showing the flash evolution from the Sept. 11, 2013 impact during the first 2 seconds. Time increases from left to right in each row, starting from the upper left. The time interval between two consecutive images in the same row is 0.1 s. Credit: Madiedo, Ortiz, et al. 2014.

“Our telescopes will continue observing the Moon as our meteor cameras monitor the Earth’s atmosphere,” said Madiedo and Ortiz in a press release. “In this way we expect to identify clusters of rocks that could give rise to common impact events on both planetary bodies. We also want to find out where the impacting bodies come from.”

You can read the team’s paper here.

February 22, 2014December 23, 2015 by Nancy Atkinson

An Incredible Visualization of Asteroids from the Sloan Digital Sky Survey

Illustration from Parker et al, 2008, of the decomposition of the main-belt asteroid population into families and background objects in proper a vs. sin(i) (left panels) and proper a vs. e (right panels). The top panels show all (background and family) objects in the data subset. The two middle panels show objects from 37 identi?ed families, and the bottom two panels show the background population. Credit: Parker et al, 2008.

Who knew asteroids could be so beautiful and mesmerizing? In 2008, a group of astronomers led by Alex Parker did a study of the size distribution of asteroid families using data from the Sloan Digital Sky Survey. Asteroid families often have distinctive optical colors, the team said, and they were able to offer an improved way to separate out the family members into their colors. This resultant animation put together just this week by Parker shows the orbital motions of over 100,000 asteroids, with colors illustrating the compositional diversity and relative sizes of the asteroids.

“The compositional gradient of the asteroid belt is clearly visible,” says Parker, “with green Vesta-family members in the inner belt fading through the blue C-class asteroids in the outer belt, and the deep red Trojan swarms beyond that.”

All main-belt asteroids and Trojan asteroids with orbits known to high precision are shown in the video and the animation is rendered with a timestep of 3 days. Via Twitter, Parker said this animation took — from start to finish — 20 hours to render on 8 CPUs.

For reference, the average orbital distances of Mercury, Venus, Earth, Mars, and Jupiter are illustrated with rings.

Painted Stone: Asteroids in the Sloan Digital Sky Survey from Alex Parker on Vimeo.

February 18, 2014December 23, 2015 by Bob King

‘Moby Dick’ Asteroid 2000 EM26 is Missing – Help Astronomers Find It

Yesterday evening you may have dropped by to watch Slooh’s live coverage of asteroid 2000 EM26 as it passed just 8.8 lunar distances of Earth. Surprise – the space rock never showed up! Slooh’s robotic telescope attempted to recover the asteroid and share its speedy travels with the world but failed to capture an image at the predicted position.

Now nicknamed Moby Dick after the elusive whale in Herman Melville’s novel of the same name, the asteroid’s gone missing in the deep sea of space. Earthlings need fear no peril; it’s not headed in our direction anytime soon. Either the asteroid’s predicted path was in error or the object was much fainter than expected. More likely the former.

Last night’s coverage attempt of 2000 E26’s close flyby of Earth

2000 EM26’s predicted brightness at the time was around magnitude 15.4, not bright but well within range of the telescope. Rather than throwing their hands up in the air, the folks at Slooh are calling upon amateur astronomers make a photographic search for the errant space rock in the next few nights.

Since the asteroid was last observed 14 years ago for only 9 days, it isn’t too surprising that uncertainties in its position could add up over time, shifting the asteroid’s position and path to a different part of the sky by 2014. According to Daniel Fischer, German amateur astronomer and astronomy writer, the positions were off by 100 degrees! As Paul Cox, Slooh’s Observatory Director, points out:

“Discovering these Near Earth Objects isn’t enough. As we’ve seen with 2000 EM26, all the effort that went into its discovery is worthless unless followup observations are made to accurately determine their orbits for the future. And that’s exactly what Slooh members are doing, using the robotic telescopes at our world-class observatory site to accurately measure the precise positions of these asteroids and comets.”

If a determined, modern-day Ahab doesn’t find this asteroidal Moby Dick, one of the large scale robotic telescope surveys probably will. Here’s a link to the NASA/JPL particulars including brightness, coordinates and distance for 2000 EM26.

Similar sized asteroids, including ones passing even closer to Earth, zip by every month. 2000 EM26 received a lot of coverage yesterday likely because it arrived near the time of the anniversary of the Chelyabinsk meteorite fall over Russia. Though it remains scarce for now, eyes are on the sky to find the asteroid again and refine its orbit. Hopefully the beast won’t get away next time.

Check out the lively discussion going on at Asteroid and Comet Researcher List. More information HERE.

February 5, 2014December 23, 2015 by Elizabeth Howell

Astronomers Look “Inside” an Asteroid for the First Time

Itokawa, a peanut-shaped asteroid that has different densities in its small body. Credit: ESO/JAXA

From directly inferring the inside of an asteroid for the first time, astronomers have discovered these space rocks can have strange variations in density. The observations of Itokawa — which you may remember from the Japanese Hayabusa mission that landed on the asteroid in 2005 — not only teach us more about how asteroids came to be, but could help protect Earth against stray space rocks in the future, the researchers said.

“This is the first time we have ever been able to to determine what it is like inside an asteroid,” stated Stephen Lowry, a University of Kent scientist who led the research. “We can see that Itokawa has a highly varied structure; this finding is a significant step forward in our understanding of rocky bodies in the solar system.”

It’s not clear why Itokawa has such different densities at opposite sides of its peanut shape; perhaps it was two asteroids that rubbed up against each other and merged. At just shy of six American football fields long, the space rock has density varying from 1.75 to 2.85 grams per cubic centimetre. This precise measurement came courtesy of the European Southern Observatory’s New Technology Telescope in Chile.

The telescope calculated the speed and speed changes of Itokawa’s spin and combined that information with data on how sunlight can affect the spin rate. Asteroids are generally tiny and irregularly shaped sorts of bodies, which means the effect of heat on the body is not evenly distributed. That small difference makes the asteroid’s spin rate change.

This heat effect (more properly called the Yarkovsky-O’Keefe-Radzievskii-Paddack effect) is slowly making Itokawa’s spin rate go faster, at a rate of 0.045 seconds every Earth year. This change, previously unexpected by scientists, is only possible if the peanut bulges have different densities, the scientists said.

“Finding that asteroids don’t have homogeneous interiors has far-reaching implications, particularly for models of binary asteroid formation,” added Lowry. “It could also help with work on reducing the danger of asteroid collisions with Earth, or with plans for future trips to these rocky bodies.”

More details on the research will be available in the journal Astronomy and Astrophysics.

Source: European Southern Observatory

January 22, 2014December 23, 2015 by Nancy Atkinson

Herschel Discovers Water Vapor Spewing from Ceres

Artist’s impression of Ceres. Credit: ESA.

With the Dawn spacecraft now heading towards the dwarf planet/asteroid Ceres, the mission has suddenly gotten even more intriguing. The Herschel space observatory has discovered water vapor around Ceres, and the vapor could be emanating from water plumes — much like those that are on Saturn’s moon Enceladus – or it could be from cryovolcanism from geysers or icy volcano.

“This is the first time water vapor has been unequivocally detected on Ceres or any other object in the asteroid belt and provides proof that Ceres has an icy surface and an atmosphere,” said Michael Küppers of ESA in Spain, lead author of a paper in the journal Nature.

Ceres might be considered to have a bit of an identity crisis, and this new discovery might complicate things even more. When it was discovered in 1801, astronomers thought it was a planet orbiting between Mars and Jupiter. Later, other bodies with similar orbits were found, marking the discovery of our Solar System’s main belt of asteroids.

Ceres laid claim as the largest asteroid in our Solar System, but in 2006, the International Astronomical Union reclassified Ceres as a dwarf planet because of its large size.

But now, could Ceres also have comet-like attributes? Herschel scientists say the most straightforward explanation of the water vapor production is through sublimation, where ice is warmed and transformed directly into gas, dragging the surface dust with it, and exposing fresh ice underneath to sustain the process. This is how comets work.

Ceres is roughly 950 kilometers (590 miles) in diameter. The best guess on Ceres composition is that it is layered, perhaps with a rocky core and an icy outer mantle. Ice had been theorized to exist on Ceres but had not been detected conclusively, until now.

This graph shows variability in the intensity of the water absorption signal detected at Ceres by the Herschel space observatory on March 6, 2013. Credit: ESA.

Herschel used its far-infrared vision with the HIFI instrument to see a clear spectral signature of the water vapor. But, interestingly, Herschel did not see water vapor every time it looked. There were variations in the water signal during the dwarf planet’s 9-hour rotation period. The telescope spied water vapor four different times, on one occasion there was no signature. The astronomers deduced that almost all of the water vapor was seen to be coming from just two spots on the surface.

Although Herschel was not able to make a resolved image of Ceres, the team was able to derive the distribution of water sources on the surface.

“We estimate that approximately 6 kg of water vapour is being produced per second, requiring only a tiny fraction of Ceres to be covered by water ice, which links nicely to the two localised surface features we have observed,” says Laurence O’Rourke, Principal Investigator for the Herschel asteroid and comet observation programme called MACH-11, and second author on the paper.

The two emitting regions are about 5% darker than the average on Ceres. Since darker regions are able to absorb more sunlight, they are then likely the warmest regions, resulting in a more efficient sublimation of small reservoirs of water ice, the team said.

They added that this new finding could have significant implications for our understanding of the evolution of the Solar System.

“Herschel’s discovery of water vapour outgassing from Ceres gives us new information on how water is distributed in the Solar System,” said Göran Pilbratt, ESA’s Herschel Project Scientist. “Since Ceres constitutes about one fifth of the total mass of asteroid belt, this finding is important not only for the study of small Solar System bodies in general, but also for learning more about the origin of water on Earth.”

Dawn is scheduled to arrive at Ceres in the spring of 2015 after spending more than a year orbiting the large asteroid Vesta. Dawn will give us the closest look ever at Ceres surface and provide more insight into this latest finding.

“We’ve got a spacecraft on the way to Ceres, so we don’t have to wait long before getting more context on this intriguing result, right from the source itself,” said Carol Raymond, the deputy principal investigator for Dawn. “Dawn will map the geology and chemistry of the surface in high resolution, revealing the processes that drive the outgassing activity.”

Sources: ESA, NASA, Nature

January 15, 2014December 23, 2015 by Nancy Atkinson

Hitch a Ride on the Next Mission to an Asteroid

This is an artist's concept of NASA's OSIRIS-REx spacecraft preparing to take a sample from asteroid Bennu. Credit: NASA/Goddard/Chris Meaney

NASA and the Planetary Society are teaming up to give everyone the opportunity tag along on the next mission to an asteroid … well, your name can go along on the trip, anyway! You can submit your name to be added on to a microchip that will be aboard the Origins-Spectral Interpretation Resource Identification Security Regolith Explorer (OSIRIS-REx) spacecraft, which will launch to the asteroid Bennu in 2016 and arrive in 2018.

“We’re thrilled to be able to share the OSIRIS-REx adventure with people across the Earth, to Bennu and back,” said Dante Lauretta, principal investigator of the OSIRIS-REx mission from the University of Arizona in Tucson. “It’s a great opportunity for people to get engaged with the mission early and join us as we prepare for launch.”

The spacecraft will spend more than two years at the 1,760-foot (500-meter)-wide asteroid. The spacecraft will collect a sample of Bennu’s surface and return it to Earth in 2023 in a sample return capsule.

The “Messages to Bennu!” microchip will travel to the asteroid on the spacecraft, and once the sample return capsule deploys, the spacecraft will be placed into a long-term solar orbit around the Sun, along with the microchip and every name on it.

You can submit your name at this website. The deadline is September 30, 2014.

After you submit your name, you can download and print a certificate.

“You’ll be part of humankind’s exploration of the solar system — How cool is that?” said Bill Nye, chief executive officer of The Planetary Society.

Participants who “follow” or “like” the mission on Facebook will receive updates on the location of their name in space from launch time until the asteroid samples return to Earth. Facebook fans also will be kept apprised of mission progress and late-breaking news through regular status updates.

The OSIRIS-REx mission goal is to address basic questions about the composition of the very early solar system, the source of organic materials and water that made life possible on Earth, and to better predict the orbits of asteroids that represent collision threats to the Earth. It will collect a minimum of 2 ounces (60 grams) of surface material.

Find out more about the mission here and here.

December 10, 2013December 23, 2015 by Nancy Atkinson

Space Shuttle-Sized Asteroid 2013 XY8 to Fly Past Earth on Dec. 11

Asteroid 2013 XY8 imaged on 2013, December 10, 2013 by E. Guido, N. Howes and M. Nicolini/Remanzacco Observatory.

A newly-discovered asteroid about the size of a space shuttle will fly past Earth on December 11, 2013 at a very safe distance of 760,000 kilometers (470,000 miles). The closest approach of Asteroid 2013 XY8 will be 11:14 UT, and its size is estimated between 31 – 68 meters. This asteroid is zipping along at about 14 kilometers per second, and of course at about 2 lunar distances away, there is no danger of this asteroid hitting Earth. The asteroid was discovered on Dec. 7 by the team at the Catalina Sky Survey, and our friends Ernesto Guido, Nick Howes and Martino Nicolini from the Remanzacco Observatory have provided a follow-up image of the asteroid, taken just this morning.

You can see an animation of it here, and more information at their website.

And as usual with close passing asteroids, the Virtual Telescope Project will is offering a live, online event sharing real-time images of 2013 XY8 with live commentary by their science staff. “It will be a nice opportunity to spy this 40 meter large asteroid moving across the stars,” said Gianluca Masi from the Virtual Telescope Project.

The feed is live now, and you can watch below: