We are not Alone: Government Sensors Shed New Light on Asteroid Hazards

How hazardous are the thousands and millions of asteroids that surround the third rock from the Sun – Earth? Since an asteroid impact represents a real risk to life and property, this is a question that has been begging for answers for decades. But now, scientists at NASA’s Jet Propulsion Laboratory have received data from a variety of US Department of Defense assets and plotted a startling set of data spanning 20 years.

This latest compilation of data underscores how frequent some of these larger fireballs are, with the largest being the Chelyabinsk event on February 15, 2013 which injured thousands in Russia. The new data will improve our understanding of the frequency and presence of small and large asteroids that are hazards to populated areas anywhere on Earth.

On Feb. 28, 2009, Peter Jenniskens (SETI/NASA), finds his first 2008TC3 meteorite after an 18-mile long journey. "It was an incredible feeling," Jenniskens said. The African Nubian Desert meteorite of Oct 7, 2008 was the first asteroid whose impact with Earth was predicted while still in space approaching Earth. 2008TC3 and Chelyabinsk are part of the released data set. (Credit: NASA/SETI/P.Jenniskens)
On Feb. 28, 2009, Peter Jenniskens (SETI/NASA), finds his first 2008TC3 meteorite after an 18-mile long journey. “It was an incredible feeling,” Jenniskens said. The meteorite which impacted in the Nubian Desert of Africa on Oct 7, 2008 was the first asteroid whose impact with Earth was predicted while still in space approaching Earth. Meteorite 2008TC3 and Chelyabinsk’s are part of the released data set. (Credit: NASA/SETI/P.Jenniskens)

The data from “government sensors” – meaning “early warning” satellites to monitor missile launches (from potential enemies) as well as infrasound ground monitors – shows the distribution of bolide (fireball) events. The data first shows how uniformly distributed the events are around the world. This data is now released to the public and researchers for more detailed analysis.

The newest data released by the US government shows both how frequent bolides are and also how effectively the Earth’s atmosphere protects the surface. A subset of this data had been analyzed and reported by Dr. Peter Brown from the University of Western Ontario, Canada and his team in 2013 but included only 58 events. This new data set holds 556 events.

The newly released data also shows how the Earth’s atmosphere is a superior barrier that prevents small asteroids’ penetration and impact onto the Earth’s surface. Even the 20 meter (65 ft) Chelyabinsk asteroid exploded mid-air, dissipating the power of a nuclear blast 29.7 km (18.4 miles, 97,400 feet) above the surface. Otherwise, this asteroid could have obliterated much of a modern city; Chelyabinsk was also saved due to sheer luck – the asteroid entered at a shallow angle leading to its demise; more steeply, and it would have exploded much closer to the surface. While many do explode in the upper atmosphere, a broad strewn field of small fragments often occurs. In historical times, towns and villages have reported being pelted by such sprays of stones from the sky.

NASA and JPL emphasized that investment in early detection of asteroids has increased 10 fold in the last 5 years. Researchers such as Dr. Jenniskens at the SETI Institute has developed a network of all-sky cameras that have determined the orbits of over 175,000 meteors that burned up in the atmosphere. And the B612 Foundation has been the strongest advocate of discovering of all hazardous asteroids. B612, led by former astronauts Ed Lu and Rusty Schweikert has designed a space telescope called Sentinel which would find hazardous asteroids and help safeguard Earth for centuries into the future.

Speed is everything. While Chelyabinsk had just 1/10th the mass of Nimitz-class super carrier, it traveled 1000 times faster. Its kinetic energy on account of its speed was 20 to 30 times that released by the nuclear weapons used to end the war against Japan – about 320 to 480 kilotons of TNT. Briefly, asteroids are considered to be any space rock larger than 1 meter and those smaller are called meteoroids.

Two earlier surveys can be compared to this new data. One by Eugene Shoemaker in the 1960s and another by Dr. Brown. The initial work by Shoemaker using lunar crater counts and the more recent work of Dr. Brown’s group, utilizing sensors of the Department of Defense, determined estimates of the frequency of asteroid impacts (bolide) rates versus the size of the small bodies. Those two surveys differ by a factor of ten, that is, where Shoemaker’s shows frequencies on the order of 10s or 100s years, Brown’s is on the order of 100s and 1000s of years. The most recent data, which has adjusted Brown’s earlier work is now raising the frequency of hazardous events to that of the work of Shoemaker.

The work of Dr. Brown and co-investigators led to the following graph showing the frequency of collisions with the Earth of asteroids of various sizes. This plot from a Letter to Nature by P. Brown et al. used 58 bolides from data accumulated from 1994 to 2014 from government sensors. Brown and others will improve their analysis with this more detailed dataset. The plot shows that a Chelyabinsk type event can be expected approximately every 30 years though the uncertainty is high. The new data may reduce this uncertainty. Tungunska events which could destroy a metropolitan area the size of Washington DC occur less frequently – about once a century.

The estimated cumulative flux of impactors at the Earth. The bolide impactor flux at Earth (Bolide flux 1994-2013 - black circles) based on ~20 years of global observations from US Government sensors and infrasound airwave data. Global coverage averages 80% among a total of 58 observed bolides with E > 1 kt and includes the Chelyabinsk Chelyabinsk bolide (far right black circle). This coverage correction is approximate and the bolide flux curve is likely a lower limit. The full caption is at bottom. (Credit: P. Brown, Letter to Nature, 2013, Figure 3)
The estimated cumulative flux of impactors at the Earth. The bolide impactor flux at Earth (Bolide flux 1994-2013 – black circles) based on ~20 years of global observations from US Government sensors and infrasound airwave data. Global coverage averages 80% among a total of 58 observed bolides with E > 1 kt and includes the Chelyabinsk Chelyabinsk bolide (far right black circle). This coverage correction is approximate and the bolide flux curve is likely a lower limit. The full caption is at bottom. (Credit: P. Brown, Letter to Nature, 2013, Figure 3)

Asteroids come in all sizes. Smaller asteroids are much more common, larger ones less so. A common distribution seen in nature is represented by a bell curve or “normal” distribution. Fortunately the bigger asteroids number in the hundreds while the small “city busters” count in the 100s of thousands, if not millions. And fortunately, the Earth is small in proportion to the volume of space even just the space occupied by our Solar System. Additionally, 69% of the Earth’s surface is covered by Oceans. Humans huddle on only about 10% of the surface area of the Earth. This reduces the chances of any asteroid impact effecting a populated area by a factor of ten.

Altogether the risk from asteroids is very real as the Chelyabinsk event underscored. Since the time of Tugunska impact in Siberia in 1908, the human population has quadrupled. The number of cities of over 1 million has increased from 12 to 400. Realizing how many and how frequent these asteroid impacts occur plus the growth of the human population in the last one hundred years raises the urgency for a near-Earth asteroid discovery telescope such as B612’s Sentinel which could find all hazardous objects in less than 10 years whereas ground-based observations will take 100 years or more.

Reference:
New Map Shows Frequency of Small Asteroid Impacts, Provides Clues on Larger Asteroid Population

Full Caption of the included plot from LETTERS TO NATURE, The Chelyabinsk airburst : Implications for the Impact Hazard, P.G. Brown, et al.

The estimated cumulative flux of impactors at the Earth. The bolide impactor flux at Earth (Bolide flux 1994-2013 – black circles) based on ~20 years of global observations from US Government sensors and infrasound airwave data. Global coverage averages 80% among a total of 58 observed bolides with E > 1 kt and includes the Chelyabinsk Chelyabinsk bolide (far right black circle). This coverage correction is approximate and the bolide flux curve is likely a lower limit. The brown-coloured line represents an earlier powerlaw fit from a smaller dataset for bolides between 1 – 8 m in diameter15. Error bars represent counting statistics only. For comparison, we plot de-biased estimates of the near-Earth asteroid impact frequency based on all asteroid survey telescopic search data through mid- 2012 (green squares)8 and other earlier independently analysed telescopic datasets including NEAT discoveries (pink squares) and finally from the Spacewatch (blue squares) survey, where diameters are determined assuming an albedo of 0.1. Energy for telescopic data is computed assuming a mean bulk density of 3000 kgm-3 and average impact velocity of 20.3 kms-1. The intrinsic impact frequency for these telescopic data was found using an average probability of impact for NEAs as 2×10-9 per year for the entire population. Lunar crater counts converted to equivalent impactor flux and assuming a geometric albedo of 0.25 (grey solid line) are shown for comparison9, though we note that contamination by secondary craters and modern estimates of the NEA population which suggest lower albedos will tend to shift this curve to the right and down. Finally, we show estimated influx from global airwave measurements conducted from 1960-1974 which detected larger (5-20m) bolide impactors (upward red triangles) using an improved method for energy estimation compared to earlier interpretations of these same data.

Asteroid 2014 SC324 Zips By Earth Friday Afternoon – Tips on How to See it

What a roller coaster week it’s been. If partial eclipses and giant sunspots aren’t your thing, how about a close flyby of an Earth-approaching asteroid?  2014 SC324 was discovered on September 30 this year by the Mt. Lemmon Survey high in the Catalina Mountains north of Tucson, Arizona. Based on brightness, the tumbling rock’s size is estimated at around 197 feet (60-m), on the large side compared to the many small asteroids that whip harmlessly by Earth each year.

Near-Earth asteroid 2014 SC324 caught in the camera on October 23. The telescope tracked on the zippy space rock, causing the stars to trail. Credit: Gianluca Masi
Near-Earth asteroid 2014 SC324 caught in the camera on October 23. The telescope tracked on the zippy space rock, causing the stars to trail. Credit: Gianluca Masi

Closest approach happens around 2 p.m. CDT (7 p.m. UT) Friday afternoon when our fast friend misses Earth by just 351,000 miles (565,000 km) or 1.5 times the distance to the Moon. This is a very safe distance, so we can finish up our lunches without a jot of concern. But the asteroid’s  combination of size and proximity means amateur astronomers with a 10-inch or larger telescope will be able to track it across the sky beginning tonight (Oct. 23) and continuing through tomorrow night. 2014 SC324 should shine tolerably bright this evening at around magnitude +13.5.

Bright here is something of a euphemism, but when it comes to new Earth-approaching asteroids, this is within range of many amateur instruments. And because 2014 SC324 is “only” a half million miles away tonight, it’s not moving so fast that you can’t plot its arc on a single star chart, spot it and go for a ride.


Simulation based on recent data showing the known asteroids orbiting the Sun

By Friday evening, the new visitor will have faded a bit to magnitude +14. You can create a track for 2014 SC324 by inputting its orbital elements into a variety of astro software programs like MegaStar, the Sky, and Le Ciel. Elements are available via the Minor Planet Center and Horizons. Once saved, the program will make a track of the asteroid’s movement at selected time intervals. Print out the chart and you’re ready for the hunt!

Illustration of small asteroids passing near Earth. Credit: ESA / P. Carril
Illustration of small asteroids passing near Earth. Credit: ESA / P. Carril

You can also go to Horizons, ask for a list of positions every 15 minutes for example and then hand plot those positions in right ascension (R.A.) and declination (Dec.) on a star map.  This is what I do. I find the the general chunk of sky the asteroid’s passing through, print the map and then mark positions in pencil and connect them all with a line. Now I’ve got a chart I can use at the telescope based on the most current orbit.

Tonight the errant mountain will rumble through Aries the Ram, which is conveniently located in the eastern sky below Andromeda and the Great Square of Pegasus at nightfall.

Finding a dim, fast-moving object is doubtless an exciting challenge, but if you lack the equipment or the weather doesn’t cooperate, you can see the show online courtesy of Italian astrophysicist Gianluca Masi. He’ll stream the close encounter live on his Virtual Telescope Project website beginning at 7 p.m. CDT (midnight UT) tomorrow night October 24-25.

Clear skies!

Get Ready for Sunday’s Close Flyby of Asteroid 2014 RC

Guess who’s dropping by for a quick visit this weekend? On Sunday, a 60-foot-wide (20-meters) asteroid named 2014 RC will skim just 25,000 miles (40,000 km) from Earth. That’s within spitting distance of all those geosynchronous communication and weather satellites orbiting at 22,300 miles. 

Size-wise, this one’s similar to the Chelyabinsk meteorite that exploded over Russia’s Ural Mountains region in February 2013. But it’s a lot less scary. 2014 RC will cleanly miss Earth this time around, and although it’s expected back in the future, no threatening passes have been identified. Whew!

2014 RC will pass along the outer edge of the geosynchronous satellite belt, home to many weather and communications satellites. The chance of a hit is close to infinitesimal. Click for more information and detailed finder charts. Credit: SatFlare
2014 RC will pass along the outer edge of the geosynchronous satellite belt, home to many weather and communications satellites. The chance of a hit is close to infinitesimal. Click for more information and detailed finder charts. Credit: SatFlare

NEOs or Near Earth Asteroids are defined as space rocks that come within about 28 million miles of Earth’s orbit. Nearly once a month astronomers discover an Earth-crossing asteroid that passes within the moon’s orbit.  In spite of hype and hoopla, none has threatened the planet. As of February 2014, we know of 10,619 near-Earth asteroids. It’s estimated that 93% of all NEOs larger than 1 km have been discovered but 99% of the estimated 1 million NEOs 100 feet (30-meters) still remain at large.

No surprise then that new ones pop up routinely in sky surveys. Take this past Sunday night for example, when the Catalina Sky Survey nabbed 2014 RA, a 20-foot (6-meter) space rock that whistled past Earth that evening at 33,500 miles (54,000 km). It’s now long gone.

Artist view of an asteroid (with companion) passing near Earth. Credit: P. Carril / ESA
Artist view of an asteroid (with companion) passing near Earth. Credit: P. Carril / ESA

2014 RC was picked up on or about September 1-2 by both the Catalina Sky Survey and Pan-STARRS 1 survey telescope atop Mt. Haleakala in Maui. The details are still being worked out as to which group will take final discovery credit. Based on current calculations, 2014 RC will pass closest to Earth around 2:15 p.m. EDT (18:15 UT) on Sunday, September 7th. When nearest, the asteroid is expected to brighten to magnitude +11.5 – too dim for naked eye observing but visible with a good map in 6-inch and larger telescopes.

Seeing it will take careful planning. Unlike a star or planet, this space rock will be faint and barreling across the sky at a high rate of speed. Discovered at magnitude +19, 2014 RC will brighten to magnitude +14 during the early morning hours of September 7th. Even experienced amateurs with beefy telescopes will find it a challenging object in southern Aquarius both because of low altitude and the unwelcome presence of a nearly full moon.


64-frame movie showing Toutatis tumbling through space only 4.3 million miles from Earth on Dec. 12-13. Credit: NASA/Goldstone radar

Closest approach happens in daylight for North and South America , but southern hemisphere observers might spot it with a 6-inch scope as a magnitude +11.5  “star” zipping across the constellations Pictor and Puppis. 2014 RC fades rapidly after its swing by Earth and will quickly become impossible to see in all amateur telescopes, though time exposure photography will keep the interloper in view for a few additional hours.

2014 RC accelerates across the sky from 4 a.m. to 4 p.m EDT in this path created by Gianluca Masi using SkyX Pro software and the latest positions from JPL.
2014 RC accelerates across the sky between 4 a.m. to 4 p.m EDT September 7 in this path created by Gianluca Masi using SkyX Pro software and the latest positions from JPL.

Most of us won’t have the opportunity to run outside and see the asteroid, but Gianluca Masi and his Virtual Telescope Project site will cover it live starting at 6 p.m. EDT (22:00 UT). Lance Benner, who researches radar imaging of near-Earth and main-belt asteroids, hopes to image 2014 RC with 230-foot (70-m) radar dish at the Goldstone complex on September 5-7 and possibly the big 1,000-foot (305-m) radar dish at Arecibo. Both provide images based on radar echoes that show asteroids up close with shapes, craters, ridges and all.

Asteroid 2014 KH39 Zips Just 1.1 LD from Earth – Watch it LIVE June 3

Got any plans Tuesday? Good. Keep them but know this. That day around 3 p.m. CDT (20:00 UT) asteroid 2014 KH39 will silently zip by Earth at a distance of just 272,460 miles (438,480 km) or 1.14 LDs (lunar distance). Close as flybys go but not quite a record breaker. The hefty space rock will buzz across the constellation Cepheus at nearly 25,000 mph (11 km/sec) near the Little Dipper at the time.

Observers in central Europe and Africa will have  dark skies for the event, however at magnitude +17 the asteroid will be too faint to spot in amateur telescopes. No worries. The Virtual Telescope Project, run by astrophysicist Gianluca Masi, will be up and running with real-time images and live commentary during the flyby. The webcast begins at 2:45 p.m. CDT June 3.

2014 KH39 was discovered on May 24 by Richard Kowalski of the Catalina Sky Survey. (Kowalski is the same astronomer who discovered asteroid 2008 TC3, the small asteroid that impacted in Sudan in 2008). Further observations by the CSS and additional telescopes like Pan-STARRS 1 in Hawaii nailed down its orbit as an Earth-approacher with an approximate size of 72 feet (22 meters). That’s a tad larger than the 65-foot Chelyabinsk asteroid that exploded into thousands of small stony meteorites over Russia in Feb. 2013.

Diagram showing the orbit of 2014 KH39. Yellow shows the portion of its orbit above the plane of Earth’s orbit (grey disk); blue is below the plane. When farthest, the asteroid travels beyond Mars into the asteroid belt. It passes closest to Earth around 3 p.m. CDT June 3. Credit: IAU Minor Planet Center
Diagram showing the orbit of 2014 KH39. Yellow shows the portion of its orbit above the plane of Earth’s orbit (grey disk); blue is below the plane. When farthest, the asteroid travels beyond Mars into the asteroid belt. It passes closest to Earth around 3 p.m. CDT June 3. Credit: IAU Minor Planet Center

Since this asteroid will safely miss Earth we have nothing to fear from the flyby. I only report it here to point out how common near-Earth asteroids are and how remarkable it is that we can spot them at all. While we’re a long ways from finding and tracking all potentially hazardous asteroids, dedicated sky surveys turn up dozens of close-approaches every year. On the heels of 2014 KH39, the Earth-approaching asteroid 2014 HQ124 will pass 3.3 LDs away 5 days later on June 8. With a diameter estimated at more than 2,100 feet (650-m) it’s expected to become as bright as magnitude +13.7. Southern hemisphere observers might track it with 8-inch and larger telescopes as its speeds across Horologium and Eridanus the morning before closest approach.

The chart shows the cumulative known total of near-Earth asteroids (NEAs) vs. time. The blue area shows all NEAs while the red shows those roughly 1 km and larger. Thanks to many surveys underway as well as help from space probes like the Wide-Field Infrared Explorer (WISE), discovery totals have been ramping up. Credit: NASA
The chart shows the cumulative known total of near-Earth asteroids (NEAs) vs. time. The blue area shows all NEAs while the red shows those roughly 1 km and larger. Thanks to many ground-based surveys underway as well as space probes like the Wide-field Infrared Survey Explorer (WISE), discovery totals have ramped up in recent years. There are probably millions of NEOs smaller than 140 meters waiting to be discovered. Credit: NASA

Perusing the current list of upcoming asteroid approaches, these two will be our closest visitors at least through early August. Near-Earth objects (NEOs) are comets and asteroids whose original orbits have been re-worked by the gravity of the planets – primarily Jupiter – into new orbits that allow them to approach relatively close to Earth. The ones we’re most concerned about are a subset called Potentially Hazardous Asteroids or PHAs, defined as objects that approach within 4.65 million miles (7.48 million km) of Earth and span 500 feet (150-m) across or larger. The key word here is ‘potential’. PHAs won’t necessarily hit the Earth – they only have the potential to do so over the vastness of time. On the bright side, PHAs make excellent targets for sampling missions.

Most near-Earth asteroids fall into three classes named after the first asteroid discovered in that class. Apollo and Aten asteroids cross Earth's orbit; Amors orbit just beyond Earth but cross Mars' orbit. Credit: Wikipedia
Most near-Earth asteroids fall into three classes named after the first asteroid discovered in that class. Apollo and Aten asteroids cross Earth’s orbit; Amors orbit just beyond Earth but cross Mars’ orbit. Credit: Wikipedia

As of May 30, 2014, 11,107 near-Earth objects have been discovered with 860 having a diameter of 1 km or larger. 1,481 of them have been further classified as potentially hazardous. NASA’s Near-Earth Object Program estimates that over 90% of NEOs larger than 1 km (the most potentially lethal to the planet) have been discovered and they’re now working to find 90% of those larger than 459 feet (140 meters) across. Little by little we’re getting to better know the neighborhood.

The probability that either 2014 KH39 and 2014 HQ124 will hit Earth on this round is zero. Nor do we know of any asteroid in the near future on a collision course with the planet. Enjoy the day.

Surprise: Earth Is Hit By a Lot More Asteroids Than You Thought

“The fact that none of these asteroid impacts shown in the video was detected in advance is proof that the only thing preventing a catastrophe from a ‘city-killer’ sized asteroid is blind luck.”

– Ed Lu, B612 Foundation CEO and former NASA astronaut

When we think of recent large asteroid impacts on Earth, only a handful may come to mind. In particular, one is the forest-flattening 1908 Tunguska explosion over Siberia (which may have been the result of a comet) and another is the February 2013 meteor that exploded over Chelyabinsk, shattering windows with its air blast. Both occurred in Russia, the largest country on Earth, and had human witnesses — in the case of the latter many witnesses thanks to today’s ubiquitous dashboard cameras.

While it’s true that those two observed events took place 105 years apart, there have been many, many more large-scale asteroid impacts around the world that people have not witnessed, if only due to their remote locations… impact events that, if they or ones like them ever occurred above a city or populated area, could result in destruction of property, injuries to people, or worse.

(And I’m only referring to the ones we’ve found out about over the past 13 years.)

A new video released by the B612 Foundation shows a visualization of data collected by a global nuclear weapons test network. It reveals 26 explosive events recorded from 2000 to 2013 that were not the result of nuclear detonations — these were impacts by asteroids, ranging from one to 600 kilotons in energy output.

Update: a list of the 26 aforementioned impacts and their energy outputs is below:

8/25/2000 (1-9 kilotons) North Pacific Ocean
4/23/2001 (1-9 kilotons) North Pacific Ocean
3/9/2002 (1-9 kilotons) North Pacific Ocean
6/6/2002 (20+ kilotons) Mediterranean Sea
11/10/2002 (1-9 kilotons) North Pacific Ocean
9/3/2004 (20+ kilotons) Southern Ocean
10/7/2004 (10-20 kilotons) Indian Ocean
10/26/2005 (1-9 kilotons) South Pacific Ocean
11/9/2005 (1-9 kilotons) New South Wales, Australia
2/6/2006 (1-9 kilotons) South Atlantic Ocean
5/21/2006 (1-9 kilotons) South Atlantic Ocean
8/9/2006 (1-9 kilotons) Indian Ocean
9/2/2006 (1-9 kilotons) Indian Ocean
10/2/2006 (1-9 kilotons) Arabian Sea
12/9/2006 (10-20 kilotons) Egypt
9/22/2007 (1-9 kilotons) Indian Ocean
12/26/2007 (1-9 kilotons) South Pacific Ocean
10/7/2008 (1-9 kilotons) Sudan
10/8/2009 (20+ kilotons) South Sulawesi, Indonesia
9/3/2010 (10-20 kilotons) South Pacific Ocean
12/25/2010 (1-9 kilotons) Tasman Sea
4/22/2012 (1-9 kilotons) California, USA
2/15/2013, (20+ kilotons) Chelyabinsk Oblast, Russia
4/21/2013 (1-9 kilotons) Santiago del Estero, Argentina
4/30/2013 (10-20 kilotons) North Atlantic Ocean
(Source: B612 Foundation)

To include the traditonally macabre comparison, the bomb used to destroy Hiroshima at the end of World War II was about 15 kilotons; the Nagasaki bomb was 20.

This evening former NASA astronauts Ed Lu, Tom Jones, and Apollo 8 astronaut Bill Anders will present this video to the public at a live Q&A event at the Museum of Flight in Seattle, Washington.

CEO and co-founder of the B612 Foundation, Ed Lu is working to increase awareness of asteroids and near-Earth objects with the ultimate goal of building and launching Sentinel, an infrared observatory that will search for and identify as-yet unknown objects with orbits that intersect Earth’s. The event, titled “Saving the Earth by Keeping Big Asteroids Away,” will be held at 6 p.m. PDT. It is free to the public and the visualization above is now available online on the B612 Foundation website. A press event will also be taking place at 11:30 a.m. PDT, and will be streamed live here.

Currently there is no comprehensive dynamic map of our inner solar system showing the positions and trajectories of these asteroids that might threaten Earth. The citizens of Earth are essentially flying around the Solar System with eyes closed. Asteroids have struck Earth before, and they will again – unless we do something about it.

– B612 Foundation

Want to support the Sentinel mission? Donate online here.

Added 4/24: The April 22 press conference at the Museum of Flight can be watched in its entirety below:

Technical note: While B612 and Ed Lu are presenting a new visualization on April 22, the data behind it are not entirely new. Previous surveys on NEA populations have determined within reasonable parameters the number of objects and likelihood of future impacts of varying sizes using data from WISE and ground-based observatories… see a series of slides by Alan Harris of JPL/Caltech here. (ht Amy Mainzer)

Also, if you have questions on the asteroid visualization, there are some FAQs on the B612 site here.

Watch This Asteroid Not Hit Earth

Earlier today the near-Earth asteroid 2013 NJ sailed by, coming as close as 2.5 lunar distances — about 960,000 km/596,500 miles. That’s a relatively close call, in astronomical terms, but still decidedly a miss (if you hadn’t already noticed.) Which is a good thing since 2013 NJ is estimated to be anywhere from 120–260 meters wide (400-850 feet) and would have caused no small amount of damage had its path intersected ours more intimately.

Luckily that wasn’t the case, and instead we get watch 2013 NJ as it harmlessly passes by in the video above, made from images captured by “shadow chaser” Jonathan Bradshaw from his observatory in Queensland, Australia. Nice work, Jonathan!

Keep tabs on known near-Earth objects on the JPL close pass page here.

“Oddball” Asteroid is Really a Comet

It’s a case of mistaken identity: a near-Earth asteroid with a peculiar orbit turns out not to be an asteroid at all, but a comet… and not some Sun-dried burnt-out briquette either but an actual active comet containing rock and dust as well as CO2 and water ice. The discovery not only realizes the true nature of one particular NEO but could also shed new light on the origins of water here on Earth.

JPL Near-Earth Object database map of 3552 Don Quixote's orbit
JPL Near-Earth Object database map of 3552 Don Quixote’s orbit

Designated 3552 Don Quixote, the 19-km-wide object is the third largest near-Earth object — mostly rocky asteroids that orbit the Sun in the vicinity of Earth.

According to the IAU, an asteroid is coined a near-Earth object (NEO) when its trajectory brings it within 1.3 AU from the Sun and within 0.3 AU of Earth’s orbit.

About 5 percent of near-Earth asteroids are thought to actually be dead comets. Today an international team including Joshua Emery, assistant professor of earth and planetary sciences at the University of Tennessee, have announced that Don Quixote is neither.

an asteroid is coined a Near Earth Asteroid (NEA) when its trajectory brings it within 1.3 AU from the Sun and  hence within 0.3 AU of the Earth's orbit.
An asteroid is coined a near-Earth object (NEO) when its trajectory brings it within 1.3 AU from the Sun and within 0.3 AU of Earth’s orbit. (IAU)

“Don Quixote has always been recognized as an oddball,” said Emery. “Its orbit brings it close to Earth, but also takes it way out past Jupiter. Such a vast orbit is similar to a comet’s, not an asteroid’s, which tend to be more circular — so people thought it was one that had shed all its ice deposits.”

Read more: 3552 Don Quixote… Leaving Our Solar System?

Using the NASA/JPL Spitzer Space Telescope, the team — led by Michael Mommert of Northern Arizona University — reexamined images of Don Quixote from 2009 when it was at perihelion and found it had a coma and a faint tail.

Emery also reexamined images from 2004, when Quixote was at its farthest distance from the Sun, and determined that the surface is composed of silicate dust, which is similar to comet dust. He also determined that Don Quixote did not have a coma or tail at this distance, which is common for comets because they need the sun’s radiation to form the coma and the sun’s charged particles to form the tail.

The researchers also confirmed Don Quixote’s size and the low, comet-like reflectivity of its surface.

“The power of the Spitzer telescope allowed us to spot the coma and tail, which was not possible using optical telescopes on the ground,” said Emery. “We now think this body contains a lot of ice, including carbon dioxide and/or carbon monoxide ice, rather than just being rocky.”

This discovery implies that carbon dioxide and water ice might be present within other near-Earth asteroids and may also have implications for the origins of water on Earth, as comets are thought to be the source of at least some of it.

The amount of water on Don Quixote is estimated to be about 100 billion tons — roughly the same amount in Lake Tahoe.

“Our observations clearly show the presence of a coma and a tail which we identify as molecular line emission from CO2 and thermal emission from dust. Our discovery indicates that more NEOs may harbor volatiles than previously expected.”

– Mommert et al., “Cometary Activity in Near–Earth Asteroid (3552) Don Quixote “

The findings were presented Sept. 10 at the European Planetary Science Congress 2013 in London.

Source: University of Tennessee press release

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3552 Quixote isn’t the only asteroid found to exhibit comet-like behavior either — check out Elizabeth Howell’s recent article, “Asteroid vs. Comet: What the Heck is 3200 Phaethon?” for a look at another NEA with cometary aspirations.

A Parting Look at 2012 DA14: Was This a Warning Shot from Space?

Just as anticipated, on Friday, Feb. 15, asteroid 2012 DA14 passed us by, zipping 27,000 kilometers (17,000 miles) above Earth’s surface — well within the ring of geostationary weather and communications satellites that ring our world. Traveling a breakneck 28,100 km/hr (that’s nearly five miles a second!) the 50-meter space rock was a fast-moving target for professional and amateur observers alike. And even as it was heading away from Earth DA14 was captured on camera by a team led by MIT researcher Dr. Nicholas Moskovitz using the 2.1-meter telescope at the Kitt Peak National Observatory in Tucson, AZ. The team’s images are shown above as an animated gif (you may need to click the image to play it.)

This object’s close pass, coupled with the completely unexpected appearance of a remarkably large meteor in the skies over Chelyabinsk, Russia on the morning of the same day, highlight the need for continued research of near-Earth objects (NEOs) — since there are plenty more out there where these came from.

“Flybys like this, particularly for objects smaller than 2012 DA14, are not uncommon. This one was special because we knew about it well in advance so that observations could be planned to look at how asteroids are effected by the Earth’s gravity when they come so close.”

– Dr. Nicholas Moskovitz, MIT

The animation shows 2012 DA14 passing inside the Little Dipper, crossing an area about a third the size of the full Moon in 45 minutes. North is to the left.

(For a high-resolution version of the animation, click here.)

Exterior of the 2.1-meter telescope of the Kitt Peak National Observatory (NOAO)
Exterior of the 2.1-meter telescope of the Kitt Peak National Observatory (NOAO/AURA/NSF)

According to the National Optical Astronomy Observatory, which operates the Kitt Peak Observatory, Dr. Moskovitz’ NSF-supported team “are analyzing their data to measure any changes in the rotation rate of the asteroid after its close encounter with the Earth. Although asteroids are generally too small to resolve with optical telescopes, their irregular shape causes their brightness to change as they rotate. Measuring the rotation rate of the asteroid in this way allows the team to test models that predict how the earth’s gravity can affect close-passing asteroids. This will lead to a better understanding of whether objects like 2012 DA14 are rubble piles or single solid rocks.

“This is critical to understanding the potential hazards that other asteroids could pose if they collide with the Earth.”

So just how close was DA14’s “close pass?” Well, if Earth were just a few minutes farther along in its orbit, we would likely be looking at images of its impact rather than its departure.*

Although this particular asteroid isn’t expected to approach Earth so closely at any time in the foreseeable future — at least within the next 130 years — there are lots of such Earth-crossing objects within the inner Solar System… some we’re aware of, but many that we’re not. Identifying them and knowing as many details as possible about their orbits, shapes, and compositions is key.

Even this soon after the Feb. 15 flyby observations of 2012 DA14 have provided more information on its orbit and characteristics., allowing for fine-tuning of the data on it.

According to the Goldstone Radar Observatory web page, the details on 2012 DA14 are as follows:
Semimajor axis                   1.002 AU
Eccentricity                          0.108
Inclination                           10.4 deg
Perihelion distance           0.893 AU
Aphelion distance              1.110 AU
Absolute magnitude (H)   24.4
Diameter                               ~50 meters (+- a factor of two)
Rotation period                   ~6 h  (N. Moskovitz, pers. comm.)
Pole direction                      unknown
Lightcurve amplitude        ~1 mag  (N. Moskovitz, pers. comm.)
Spectral class                       Ld  (N. Moskovitz, pers. comm.)

Goldstone is currently conducting radar observations on the asteroid. A radar map of its surface and motion is anticipated in the near future.

Read more about Dr. Moskovitz’ observations on the NOAO website here, and see more images of 2012 DA14 captured by astronomers around the world in our previous article.

A bright meteor witnessed over Russia on Feb. 15, 2013 (RussiaToday)
A bright daytime meteor witnessed over Russia on Feb. 15, 2013 (RussiaToday)

Also, in an encouraging move by international leaders in the field, during the fiftieth session of the Scientific and Technical Subcommittee of the Committee on the Peaceful Uses of Outer Space, currently being held from at the United Nation Office in Vienna, near-Earth objects are on the agenda with a final report to be issued by an Action Team. Read the report PDF here.

*According to astronomer Phil Plait, while the orbits of Earth and DA14 might intersect at some point, on the 15th of February 2013 the asteroid slipped just outside of Earth’s orbit — a little over 17,000 miles shy. “It was traveling one way and the Earth another, so they could not have hit each other on this pass no matter where Earth was in its orbit,” he wrote in an email. Still, 17,000 miles is a very close call astronomically, and according to Neil deGrasse Tyson on Twitter, it “will one day hit us, like the one in Russian [sic] last night.” When? We don’t know yet. That’s why we must keep watching.

In Two Weeks This 50-Meter Asteroid Will Buzz Our Planet

 Asteroid 2012-DA14 will pass Earth closely on Feb. 15, 2013 (NASA)

On February 15 a chunk of rock about 50 meters wide will whiz by Earth at nearly 8 km/s, coming within 27,680 km of our planet’s surface — closer than many weather and communications satellites.

For those of you more comfortable with imperial units, that’s 165 feet wide traveling 17,800 mph coming within 17,200 miles. But regardless whether you prefer meters or miles, in astronomy that’s what’s called a close call.

Scientists stress that there’s no danger of an impact by this incoming asteroid, designated 2012-DA14, but it’s yet another reminder that in our neck of the Solar System we are definitely not alone.

“2012-DA14 will definitely not hit Earth,” says JPL’s near-Earth object specialist Don Yeomans. “The orbit of the asteroid is known well enough to rule out an impact.”

But with 2012-DA14’s upcoming February flyby Yeomans notes, “this is a record-setting close approach.”

The rocky asteroid will come within about 4 Earth radii, which is well within the orbits of geosynchronous satellites. During its closest approach at 19:26 UTC it should be visible in the sky to amateur telescopes (but not the naked eye), becoming as bright as an 7th- or 8th-magnitude star.

2012da14_s

Radar observatories will be watching 2012-DA14 during the days leading up to and following its approach in an attempt to better determine its size, shape and trajectory. NASA’s Goldstone facility will have an eye — er, dish — on DA14, but it won’t be visible to Arecibo. Stay tuned for more info!

Read more about 2012-DA14 on the JPL Near-Earth Object Program page here.

Say Hello to Asteroid 2007 PA8

Radar images of asteroid 2007 PA8 acquired on October 28, 29 and 30. (NASA/JPL-Caltech/Gemini)

Take a good look at asteroid 2007 PA8 — over the past week it was making its closest pass of Earth for the next 200 years… and NASA’s 230-foot (70-meter) -wide Deep Space Network antenna at Goldstone, California snapped its picture as it went by.

All right, maybe no “pictures” were “snapped”… 2007 PA8 is a small, dark body that only came within four million miles (6.5 million kilometers) today, Nov. 5 (0.043 AU, or 17 times the distance from Earth to the Moon). But the radar capabilities of the Deep Space Network antenna in California’s Mojave Desert can bounce radar off even the darkest asteroids, obtaining data that can be used to create a detailed portrait.

In the image above, a composite of radar data acquired on October 28, 29 and 30, we can see the irregular shape of 2007 PA8 as it rotates slowly — only once every 3-4 days. The perspective is looking “down” at the 1-mile (1.6-km) -wide asteroid’s north pole, showing ridges and perhaps even some craters.

Although classified as a Potentially Hazardous Asteroid (PHA) by the IAU’s Minor Planet Center the trajectory of 2007 PA8 is well understood. It is not expected to pose any impact threat to Earth in the near or foreseeable future.

2007 PA8 was discovered by LINEAR on August 9, 2007.

Read more about asteroid radar imaging here, and find out more about asteroids at JPL’s Asteroid Watch site here.

Get more information on the known properties of 2007 PA8 here.

Source: NASA Solar System Exploration. Image credits: NASA/JPL-Caltech/Gemini