Asteroids Archives

April 20, 2015December 23, 2015 by Bob King

Close Encounter of the Asteroid Kind – 2015 HD1 Skims By Earth Tonight

Newly found asteroid 2015 HD1 will pay a close visit to Earth overnight, zipping by at just 45,600 miles at 3:11 a.m. Tuesday morning. Credit: Gianluca Masi

If you wake up in the middle of the night with weird dreams about flying asteroids, I wouldn’t be surprised. Around 3 a.m. (CDT) tomorrow morning April 21, a 50-foot-wide asteroid will hurdle just 0.2 lunar distances or 45,600 miles over your bed.

The Mt. Lemmon Survey, based in Tucson, Arizona, snagged the space rock Saturday. 2015 HD1 is about as big as a full grown T-rex through not nearly as scary, since it will safely miss Earth … but not by much.

Simulated view of a small asteroid passing near Earth. Credit: NASA — Artist view of a small asteroid passing near Earth. Credit: NASA

Geostationary satellites, used for global communications, weather forecasting and satellite TV, are parked in orbits about 22,300 miles above the Earth. 2015 HD1 will zip by at just twice that distance, putting it in a more select group of extremely close-approaching objects. Yet given its small size, even if it were to collide with Earth, this dino-sized rock would probably break up into a shower of meteorites.

Lucky for all of us, astronomers conducting photographic surveys like the one at Mt. Lemmon rake the skies every clear night, turning up a dozen or more generally small, Earth-approaching asteroids every month. None yet has been found on a collision course with Earth, but many pass within a few lunar distances.

A common misunderstanding about approaching asteroids concerns Earth’s gravity. While our planet has plenty of gravitational pull, it’s no match for speedy asteroids. We can’t “pull” them in like some tractor beam.

Because they’re moving at miles per second velocities, they have lots of angular momentum (desire to keep moving in the direction they’re headed). Only asteroids headed directly for us have any hope of striking our atmosphere and potentially leaving fragments behind as meteorites.

Still, both Earth and asteroid interact. Close-approaching asteroids often will have their orbits altered by Earth’s gravity. They come in in one direction and leave on a slightly different one after Earth weighs in (literally!)

All the known asteroids orbiting the Sun – in 3D

Moving rapidly across the constellations Hydra, Antlia and Puppis tomorrow morning, 2015 HD1 is expected to reach climb briefly to magnitude +13.2. That’s faint, but with a good map, amateur astronomers with 8-inch or larger telescopes will see it move in real time across the sky like a slow satellite. To create a map, you’ll need sky-charting software like MegaStar, The Sky or Starry Night and these orbital elements.

Maximum brightness and visibility occurs between about 1 and 3 a.m CDT (6-8 UT) for observers in low northern or southern latitudes. From the West Coast, the asteroid will be low in the southwestern sky around 10 p.m. local time. Hawaiian skywatchers will get the brightest views with the asteroid highest in the sky around 9 p.m. local time. IF you live in the eastern two-thirds of the U.S., it’s either too far south or will have set by the time it’s bright enough to see.

No worries. Italian astronomer Gianluca Masi will once again fire up his telescope to provide live views of 2015 HD1 on his Virtual Telescope Project website today April 20 starting at 4 p.m. CDT (21:00 UT). So if you like, you can get a gander after all.

April 1, 2015December 23, 2015 by Ken Kremer

OSIRIS-REx Asteroid Sampler Enters Final Assembly

Artist concept of OSIRIS-REx, the first U.S. mission to return samples from an asteroid to Earth. Credit: NASA/Goddard

OSIRIS-Rex, NASA’s first ever spacecraft designed to collect and retrieve pristine samples of an asteroid for return to Earth has entered its final assembly phase.

Approximately 17 months from now, OSIRIS-REx is slated to launch in the fall of 2016 and visit asteroid Bennu, a carbon-rich asteroid.

Bennu is a near-Earth asteroid and was selected for the sample return mission because it “could hold clues to the origin of the solar system and host organic molecules that may have seeded life on Earth,” says NASA.

The spacecraft is equipped with a suite of five science instruments to remotely study the 492 meter meter wide asteroid.

Eventually it will gather rocks and soil and bring at least a 60-gram (2.1-ounce) sample back to Earth in 2023 for study by researchers here with all the most sophisticated science instruments available.

The precious sample would land arrive at Utah’s Test and Training Range in a sample return canister similar to the one for the Stardust spacecraft.

The OSIRIS-REx – which stands for Origins, Spectral Interpretation, Resource Identification, Security, Regolith Explorer – spacecraft passed a critical decision milestone on the road to launch and has been officially authorized by NASA to transition into this next mission phase.

The decision meeting to give the go ahead for final assembly was held at NASA Headquarters in Washington on March 30 and was chaired by NASA’s Science Mission Directorate, led by former astronaut John Grunsfeld who was the lead spacewalker on the final shuttle servicing mission to the Hubble Space Telescope in 2009.

“This is an exciting time for the OSIRIS-REx team,” said Dante Lauretta, principal investigator for OSIRIS-Rex at the University of Arizona, Tucson, in a stetement.

“After almost four years of intense design efforts, we are now proceeding with the start of flight system assembly. I am grateful for the hard work and team effort required to get us to this point.”

In a clean room facility near Denver, Lockheed Martin technicians began assembling a NASA spacecraft that will collect samples of an asteroid for scientific study. Working toward a September 2016 launch, the OSIRIS-REx spacecraft will be the first U.S. mission to return samples from an asteroid back to Earth. Credit: Lockheed Martin

The transition to the next phase known as ATLO (assembly, test and launch operations) is critical for the program because it is when the spacecraft physically comes together, says Lockheed Martin, prime contractor for OSIRIS-REx. Lockheed is building OSIRIS-Rex in their Denver assembly facility.

“ATLO is a turning point in the progress of our mission. After almost four years of intense design efforts, we are now starting flight system assembly and integration of the science instruments,” noted Lauretta.

Over the next six months, technicians will install on the spacecraft structure its many subsystems, including avionics, power, telecomm, mechanisms, thermal systems, and guidance, navigation and control, according to NASA.

“Building a spacecraft that will bring back samples from an asteroid is a unique opportunity,” said Rich Kuhns, OSIRIS-REx program manager at Lockheed Martin Space Systems, in a statement.

“We can feel the momentum to launch building. We’re installing the electronics in the next few weeks and shortly after we’ll power-on the spacecraft for the first time.”

OSIRIS-REx is scheduled for launch in September 2016 from Cape Canaveral Air Force Station in Florida aboard a United Launch Alliance Atlas V 411 rocket, which includes a 4-meter diameter payload fairing and one solid rocket motor. Only three Atlas V’s have been launched in this configuration.

“In just over 500 days, we will begin our seven-year journey to Bennu and back. This is an exciting time,” said Lauretta.

The spacecraft will reach Bennu in 2018 and return a sample to Earth in 2023.

Bennu is an unchanged remnant from the collapse of the solar nebula and birth of our solar system some 4.5 billion years ago, little altered over time.

The Atlas V with MMS launches, as seen by this camera placed in the front of the launchpad. Copyright © Alex Polimeni — OSIRIS-REx will launch in 2016 on an Atlas V similar to this one lofting NASA’s MMS satellites on March 12, 2015, as seen by this camera placed in the front of the launchpad. Copyright © Alex Polimeni

Significant progress in spacecraft assembly has already been accomplished at Lockheed’s Denver manufacturing facility.

“The spacecraft structure has been integrated with the propellant tank and propulsion system and is ready to begin system integration in the Lockheed Martin highbay,” said Mike Donnelly, OSIRIS-REx project manager at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, in a statement.

“The payload suite of cameras and sensors is well into its environmental test phase and will be delivered later this summer/fall.”

OSIRIS-REx is the third mission in NASA’s New Frontiers Program, following New Horizons to Pluto and Juno to Jupiter, which also launched on Atlas V rockets.

The most recent Atlas V launched NASA’s MMS quartet of Earth orbiting science probes on March 12, 2015.

OSIRIS-REx logo

NASA’s Goddard Space Flight Center in Greenbelt, Maryland, is responsible for overall mission management.

OSIRIS-REx complements NASA’s Asteroid Initiative – including the Asteroid Redirect Mission (ARM) which is a robotic spacecraft mission aimed at capturing a surface boulder from a different near-Earth asteroid and moving it into a stable lunar orbit for eventual up close sample collection by astronauts launched in NASA’s new Orion spacecraft. Orion will launch atop NASA’s new SLS heavy lift booster concurrently under development.

Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.

Ken Kremer

Artist's concept of the OSIRIS-REx spacecraft collecting a sample from asteroid 1999 RQ36. Credit: NASA — Artist’s concept of the OSIRIS-REx spacecraft collecting a sample from asteroid 1999 RQ36. Credit: NASA

Juno soars skyward to Jupiter on Aug. 5, 2011 from launch pad 41 at Cape Canaveral Air Force Station at 12:25 p.m. EDT. View from the VAB roof. Credit: Ken Kremer/kenkremer.com — OSIRIS-REx is the 3rd mission in NASA’s New Frontiers program. It follows NASA’s Juno orbiter seen here soaring skyward to Jupiter on Aug. 5, 2011 from launch pad 41 at Cape Canaveral Air Force Station at 12:25 p.m. EDT. View from the VAB roof. Credit: Ken Kremer/kenkremer.com

March 31, 2015December 23, 2015 by David Dickinson

Seeking Ceres: Following the Brave New World Through 2015

A little world is making big headlines in 2015. NASA’s Dawn spacecraft entered orbit around 1 Ceres on March 6^th, 2015, gaving us the first stunning images of the ~900 kilometre diameter world. But whether you refer to Ceres as a dwarf planet, minor planet, or the king of the asteroid belt, this corner of the solar system’s terra incognita is finally open for exploration. It has been a long time coming, as Ceres has appeared as little more than a wandering, star-like dot in the telescopes of astronomers for over two centuries since discovery.

Untitled — The orbit of 1 Ceres. Credit: NASA/JPL

And the good news is, you can observe Ceres from your backyard if you know exactly where to look for it with binoculars or a small telescope. We’ll admit, we had an ulterior motive on pulling the trigger on this post three months prior to opposition on July 24th, as Dawn will soon be exiting its ‘shadow phase’ and start unveiling the world to us up close. The first science observations for Dawn begin in mid-April.

Ceres spends all of 2015 looping through the constellations of Capricornus, Microscopium and Sagittarius. This places it low to the south for northern hemisphere observers on April 1^st in the early morning sky. Ceres will pass into the evening sky by mid-summer. Ceres orbits the Sun once every 4.6 years in a 10.6 degree inclination path relative to the ecliptic that takes it 2.6 AU to 3 AU from the Sun. The synodic period of Ceres is, on average, 467 days from one opposition to the next.

Shining at magnitude +8, April 1^st finds Ceres near the Capricornus/Sagittarius border. Ceres can reach magnitude +6.7 during a favorable opposition. Note that Ceres is currently only 20 degrees east of the position of Nova Sagittarii 2015 No. 2, currently still shining at 4th magnitude. June 29th and November 25th are also great times to hunt for Ceres in 2015 as it loops less than one degree past the 4^th magnitude star Omega Capricorni.

June 30 — Ceres meets up with Omega Capricorni on June 29th. Credit: Stellarium.

You can nab Ceres by carefully noting its position against the starry background from night to night, either by sketching the suspect field, or photographing the region. Fans of dwarf planets will recall that 1 Ceres and 4 Vesta fit in the same telescopic field of view last summer, and now sit 30 degrees apart. Ceres is now far below the ecliptic plane, but will resume getting occulted by the passing Moon on February 3^rd, 2017.

Left — The Palermo transit instrument used to discover Ceres. From *Della Specola Astronomica* (1792)

Ceres was discovered by Giuseppe Piazzi on the first day of the 19^th century on January 1^st, 1801. Ceres was located on the Aries/Cetus border just seven degrees from Mars during discovery. Piazzi wasn’t even on the hunt for new worlds at the time, but was instead making careful positional measurements of stars with the 7.5 centimetre Palermo Circle transit telescope.

At the time, the discovery of Ceres was thought to provide predictive proof of the Titus-Bode law: here was a new planet, just where this arcane numerical spacing of the planets said it should be. Ceres, however, was soon joined by the likes of Juno, Pallas, Vesta and many more new worldlets, as astronomers soon came to realize that the solar system was not the neat and tidy place that it was imagined to be in the pre-telescopic era.

To date, the Titus-Bode law remains a mathematical curiosity, which fails to hold up to the discovery of brave new exoplanetary systems that we see beyond our own.

The view from Ceres itself would be a fascinating one, as an observer on the Cererian surface would be treated to recurrent solar transits of interior solar system worlds. Mercury would be the most frequent, followed by Venus, which transits the Sun as seen from Ceres 3 times in the 21^st century: August 1^st, 2042, November 19^th, 2058 and February 13^th 2068. Mars actually transits the Sun as seen from Ceres even earlier on June 9^th, 2033. Curiously, we found no transits of the Earth as seen from Ceres during the current millennium from 2000 to 3000 AD!

From Ceres, Jupiter would also appear 1.5’ in diameter near opposition, as opposed to paltry maximum of 50” in size as seen from the Earth. This would be just large enough for Jupiter to exhibit a tiny disk as seen from Ceres with the unaided eye. The four major Galilean moons would be visible as well.

The mysteries of Ceres beckon. Does the world harbor cryovolcanism? Just what are those two high albedo white dots? Are there any undiscovered moons orbiting the tiny world? If a fair amount of surface ice is uncovered, Ceres may soon become a more attractive target for human exploration than Mars.

All great thoughts to ponder, as this stellar speck in the eyepiece of your backyard telescope becomes a brand new world full of exciting possibilities.

March 26, 2015December 23, 2015 by Jason Major

No, a Giant Asteroid Isn’t Going to “Skim” Earth on Friday

Asteroid 2014 YB35 will safely pass Earth at 4.5 million km on Friday, March 27. (Composite image by J. Major showing asteroid Lutetia imaged by ESA's Rosetta, Earth and Moon imaged by NASA's Galileo, and the Milky Way imaged by ESO and Serge Brunier.)

There are ways to report on occasional close approaches by near-Earth objects (NEOs) that convey the respectful awareness of their presences and the fact that our planet shares its neighborhood with many other objects, large and small… and that sometimes their paths around the Sun bring them unnervingly close to our own.

Then there’s just straight-up over-sensationalism intended to drum up page views by scaring the heck out of people, regardless of facts.

Apparently this is what’s happened regarding the upcoming close approach by NEO 2014 YB35. An asteroid of considerable (but definitely not unprecedented) size – estimated 440-990 meters in diameter, or around a third of a mile across – YB35 will pass by Earth on Friday, March 27, coming as close as 11.7 times the distance between Earth and the Moon at 06:20 UTC.

11.7 lunar distances. That’s 4.5 million kilometers, or almost 2.8 million miles. Cosmically close, sure, but far from “skimming”…and certainly with no danger of an impact or any of the nasty effects that would be a result thereof. None. Zero. Zilch. NASA isn’t concerned, and you shouldn’t be either.

I typically wouldn’t even bother writing up something like this, except that I have been seeing posts shared among acquaintances on Facebook and Twitter that refer to sensationalist articles portraying the event as a frightening near-miss by an apocalyptic object. I won’t link to those articles here but in short they focus heavily on the destructive nature of an object the size of YB35 were it to hit Earth and how it would wipe out “all species” of life on our planet wholesale, and how YB35 is “on course” with Earth’s orbit.

The problem I have is that these statements, although technically not false in themselves, are not being used to demonstrate the potential danger of large-scale cosmic impact events but rather to frighten and alarm people about this particular pass. Which is not any way to responsibly inform the public about impacts, asteroids, and what we can or should be doing to mitigate these dangers.

Orbital diagram of 2014 YB35 for March 27, 2015. Via JPL's Small-Body Database. — Orbital diagram of 2014 YB35 for March 27, 2015. Via JPL’s Small-Body Database.

First observed through the Catalina Sky Survey in Dec. 2014, YB35 is a good-sized asteroid. It will come relatively close to Earth on Friday but more than plenty far enough away to not pose any danger or have any physical effects on Earth in any way (similar to the close pass of the smaller asteroid 2014 UR116 in December.) YB35 will actually make slightly closer passes in March 2033 and in 2128, but still at similar distances.

YB35 is, for all intents and purposes, one of the many potentially-hazardous* asteroids that won’t hit us, and NASA is well aware of nearly all of the NEOs in its size range thanks in no small part to space observatories like NEOWISE and various ground-based survey projects around the world. They will observe this event for the increased information on YB35 that can be gathered, but they are not “on alert” and the astronomers certainly aren’t “terrified.”

Should we take this as a reminder that large asteroids are out there and we should be as diligent as we can about identifying them? Yes, certainly. Should we support missions that would help spot and track near-Earth objects as well as those that would provide a way to potentially deflect any large incoming ones? Of course. Should we drop to our knees and cry “why?!” or sleep in our backyard bunkers tonight surrounded by bottled water and cans of beans? Not at all.

So don’t believe the hype, don’t go max out your credit cards, and please don’t sleep in your bunker. Pass it on.

Want to learn more about NEOs and close approaches? Visit JPL’s Near-Earth Object Program page here. Also, watch a fascinating animation showing the discovery rate of asteroids in the Solar System from 1980-2011 by Scott Manley below.

*Note: Potentially-hazardous asteroids (PHAs) are those larger than 150m whose orbits could cross Earth’s in the future, not necessarily that they will or that Earth will be sharing the same place when and if they do.

March 13, 2015March 15, 2015 by Jason Major

This Is The Asteroid That Didn’t Hit Us

All right, sure – there are a lot of asteroids that don’t hit us. And of course quite a few that do… Earth is impacted by around 100 tons of space debris every day (although that oft-stated estimate is still being researched.) But on March 10, 2015, a 12–28 meter asteroid dubbed 2015 ET cosmically “just missed us,” zipping past Earth at 0.3 lunar distances – 115,200 kilometers, or 71, 580 miles.*

The video above shows the passage of ~~2015 ET~~ across the sky on the night of March 11–12, tracked on camera from the Crni Vrh Observatory in Slovenia. It’s a time-lapse video (the time is noted along the bottom) so the effect is really neat to watch the asteroid “racing along” in front of the stars… but then, it was traveling a relative 12.4 km/second!

UPDATE 3/14: As it turns out the object in the video above is not 2015 ET; it is a still-undesignated NEO. (My original source had noted this incorrectly as well.) Regardless, it was an almost equally close pass not 24 hours after 2015 ET’s! Double tap. (ht to Gerald in the comments.) UPDATE #2: The designation for the object above is now 2015 EO6.

Continue reading “This Is The Asteroid That Didn’t Hit Us”

March 7, 2015December 23, 2015 by Bob King

Scientists in Orbit Over Dawn’s Arrival at Ceres

The slim crescent of Ceres smiles back as the dwarf planet awaits the arrival of an emissary from Earth. This image was taken by NASA’s Dawn spacecraft on March 1, 2015, just a few days before the mission achieved orbit around the dwarf planet. Because of its angle of approach (see video above) Dawn saw Ceres from its backside, which from its perspective, was mostly in darkness. Credit: NASA/JPL

Dawn’s approach and trajectory as it begins its orbital “dance” with Ceres. As you watch, note the timeline at upper right.

Dawn made it! After a 14-month tour of the asteroid Vesta and 2 1/2 years en route to Ceres, the spacecraft felt the gentle tug of Ceres gravity and slipped into orbit around the dwarf planet at 6:39 a.m. (CST) Friday morning.

“We feel exhilarated,” said lead researcher Chris Russell at the University of California, Los Angeles, after Dawn radioed back the good news.

Not only is this humankind’s first probe to orbit a dwarf planet, Dawn is the only spacecraft to fly missions to two different planetary bodies. Dawn’s initial orbit places it 38,000 miles (61,000 km) from Ceres with a view of the opposite side of Ceres from the Sun. That’s why we’ll be seeing photos of the dwarf planet as a crescent for the time being. If you watch the video, you’ll notice that Dawn won’t see Ceres’ fully sunlit hemisphere until early-mid April.

Dawn’s spiral descent from survey orbit to the high altitude mapping orbit. The trajectory progresses from blue to red over the course of the six weeks. The red dashed segments are where the spacecraft is not thrusting with its ion propulsion system (as explained in April). Credit: NASA/JPL - See more at: http://dawnblog.jpl.nasa.gov/2014/06/30/dawn-journal-june-30-2/#sthash.CZ2WGsDQ.dpuf — Dawn’s spiral descent from survey orbit to the high altitude mapping orbit. The trajectory progresses from blue to red over the course of the six weeks. The red dashed segments are where the spacecraft is not thrusting with its ion propulsion system. Credit: NASA/JPL

The spacecraft will spend the next month gradually spiraling down to Ceres to reach its “survey orbit” of 2,730 miles in April. From there it will train its science camera and visible and infrared mapping spectrometer to gather pictures and data. The leisurely pace of the orbit will allow Dawn to spend more than 37 hours examining Ceres’ dayside per revolution. NASA will continue to lower the spacecraft throughout the year until it reaches its minimum altitude of 235 miles.

As Dawn maneuvers into orbit, its trajectory takes it to the opposite side of Ceres from the sun, providing these crescent views. These additional pictures were taken on March 1 at a distance of 30,000 miles (49,000 km). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

“Since its discovery in 1801, Ceres was known as a planet, then an asteroid and later a dwarf planet,” said Marc Rayman, Dawn chief engineer and mission director at JPL. “Now, after a journey of 3.1 billion miles (4.9 billion kilometers) and 7.5 years, Dawn calls Ceres, home.”

More about Dawn’s incredible accomplishment can be found in the excellent Dawn Journal, written by Dawn chief engineer and mission director Marc Rayman.

February 11, 2015December 23, 2015 by David Dickinson

The Number of Asteroids We Could Visit and Explore Has Just Doubled

There’s a famous line from Shakespeare’s Hamlet that says “There are more things in heaven and Earth, Horatio, than are dreamt of in your philosophy,” and the same now holds true for brave new worlds for humans to explore.

This result was published earlier this week courtesy of the NASA/JPL Near-Earth Program Office. The study found that the number of possible asteroid targets for human exploration has now doubled from the 666 known in the first study, completed in late 2010.

This information comes from NHATS, which stands for the Near Earth Object Human Spaceflight Accessible Targets Study. Yes, it’s an acronym containing acronyms. NHATS is an automated system based out of Greenbelt, Maryland which monitors and periodically updates its list of potential target candidates for accessibility. The NHATS system data is readily accessible to the public online, and as of February 11^th 2015, 1346 NHATS compliant asteroids are known.

NEO orbit types. — NEA orbit types. Credit: Brent Barbee/NASA/GSFC

This is the Holy Grail for the future of manned spaceflight, and will represent a good stepping stone (bad pun intended) for future crewed missions to Mars. Several hundred NHATS asteroids require less time and energy to reach than the Red Planet, and a few dozen even require less energy to reach than it does to enter lunar orbit.

Relative delta-V and return velocity is crucial. Apollo astronauts were subject to a blistering 11 kilometre per second reentry velocity on their return from the Moon, and future asteroid missions would be subject to the same style of trajectory on return to Earth from a solar orbit.

Mission to an NEO: a typical orbital profile. Credit: Brent Barbee/NASA/GSFC

The test of the Orion heat shield on reentry during last year’s EFT-1 flight was a step in this direction, and the next test will be an uncrewed launch atop an SLS rocket in September 2018. If all goes according to schedule — and NASA can successfully weather the ever-shifting political winds of multiple future changes of administration — expect to see astronauts exploring an NHATS asteroid placed in lunar orbit sometime around late 2023.

I know. “When I was a kid back in the 70’s…” we expected to be vacationing on Callisto by 2015, as well.

Brent Barbee at NASA’s Goddard Space Flight Center designed the automated NHATS system. It pulls data from a source that many comet and asteroid hunters are familiar with: JPL’s Small Bodies Database. The NHATS system then makes trajectory calculations and patches in conical solutions for possible spacecraft trajectories and actually gives potential launch window dates for future missions. Seriously, its fun to play with… you can even tailor and filter these by target dates versus maximum velocity constraints and the length of stays.

The orbit of asteroid 1943 Anteros. Credit: NASA/JPL.

The first discovered NHATS-compliant NEO was 2.3 kilometre 1943 Anteros way back in 1973, and famous alumni on the NHATS list also include 10 metre asteroid 2011 MD, which passed 12,000 kilometres from the Earth on June 27^th, 2011. 2011 MD is on NASA’s short list of asteroids ideal for human exploration. Another famous asteroid on the NHATS list is 99942 Apophis which — triskaidekaphobics take note — will safely miss the Earth by 31,300 kilometres on Friday the 13^th, April 2029. More are added every day, and the growing curve of discoveries also closely mirrors the rise of automated all-sky surveys such as LINEAR, PanSTARRS and the Catalina Sky Survey, though dedicated amateurs do get in on the act occasionally as well.

To date, over 12,000 NEA asteroids are now known, and you can expect future surveys such as the Large Synoptic Survey Telescope set to see first light in 2021 to add to their ranks. The Sentinel space telescope set to launch in 2017 will also boost the known number of NEOs as it covers our sunward blind spot from an orbit interior to the Earth’s. Remember Chelyabinsk? That could actually be a great rallying cry for Sentinel’s cause, as the asteroid came at the Earth from a sunward direction and avoided the sky sweeping robotic eyes of astronomers.

Sometimes, NEOs turn out to be returning space junk from the early Space Age (a low relative velocity and low orbital inclination is often a dead giveaway). Earth has also been known to capture an NEO as an occasional temporary second Moon, as occurred in 2006 in the case of asteroid 2006 RH120.

The LSST mirror in the Tuscon Mirror Lab. Photo by author.

But beyond just creating a database, the NHATS system also presents key opportunities for astronomers to perform follow-up observations of NEO asteroids, which is vital for precisely characterizing their orbits. Two future missions are also planned to return samples from NHATS asteroids: Hayabusa 2, which launched on December 3^rd 2014 headed for asteroid 1999 JU₃ in July 2018, and the OSIRIS-REx mission, set to launch in late 2016 headed for asteroid 101955 Bennu in 2018.

NHATS is providing a crucial target list for that day when first human footfall on an asteroid occurs… or should we say docking?

February 5, 2015December 23, 2015 by Bob King

An Even Closer View of Ceres Shows Multiple White Spots Now

One several images NASA's Dawn spacecraft took on approach to Ceres on Feb. 4, 2015 at a distance of about 90,000 miles (145,000 kilometers) from the dwarf planet. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

NASA’s Dawn spacecraft has acquired its latest and closest-yet snapshot of the mysterious dwarf planet world Ceres. These latest images, taken on Feb. 4, from a distance of about 90,000 miles (145,000 km) clearly show craters – including a couple with central peaks – and a clearer though still ambiguous view of that wild white spot that has so many of us scratching our heads as to its nature.

Get ready to scratch some more. The mystery spot has plenty of company.

Take a look at some still images I grabbed from the video which NASA made available today. In several of the photos, the white spot clearly looks like a depression, possibly an impact site. In others, it appears more like a rise or mountaintop. But perhaps the most amazing thing is that there appear to be not one but many white dabs and splashes on Ceres’ 590-mile-wide globe. I’ve toned the images to bring out more details:

Here the spot appears more like a depression. Frost? Ice? Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Here the white spot is at the asteroid's left limb. You can also see additional smaller spots that remind me of rayed lunar craters. Credit: — Here the white spot is at the asteroid’s left limb. You can also see lots of additional smaller spots that remind me of rayed lunar craters. Of course, they may be something else entirely. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Look down along the lower limb to spot a crater with a cool central peak. Credit: — Look down along the lower limb to spot a crater with a cool central peak. Note also how many white spots are now visible on Ceres. The mystery spot is a little right of center in this view. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Our mystery white spot is further right of center. Is it a rise or a hole? Credit: — Our mystery white spot is further right of center. Is it a rise or a hole?Are the streaks rays for fresh material from an impact the way the lunar crater Tycho appears from Earth? Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Yet another view of the mystery spot. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA

Now let’s take a look at an additional NASA animation of Ceres made using processed images. As the spot first rounds the limb it looks like a depression. But just before it disappears around the backside a pointed peak seems to appear. Intriguing, isn’t it?

January 31, 2015December 23, 2015 by Bob King

Awesome New Radar Images of Asteroid 2004 BL86

Individual radar images of 2004 BL86 and its moon. The asteroid appears very lumpy, possibly from unresolved crater rims. The moon appears elongated but that may be an artifact and not its true shape. Credit: NASA

New video of 2004 BL₈₆ and its moon

Newly processed images of asteroid 2004 BL₈₆ made during its brush with Earth Monday night reveal fresh details of its lumpy surface and orbiting moon. We’ve learned from both optical and radar data that Alpha, the main body, spins once every 2.6 hours. Beta (the moon) spins more slowly.

The images were made by bouncing radio waves off the surface of the bodies using NASA’s 230-foot-wide (70-meter) Deep Space Network antenna at Goldstone, Calif. Radar “pinging” reveals information about the shape, velocity, rotation rate and surface features of close-approaching asteroids. But the resulting images can be confusing to interpret. Why? Because they’re not really photos as we know it.

For one, the moon appears to be revolving perpendicular to the main body which would be very unusual. Most moons orbit their primary approximately in the plane of its equator like Earth’s moon and Jupiter’s four Galilean moons. That’s almost certainly the case with Beta. Radar imagery is assembled from echoes or radio signals returned from the asteroid after bouncing off its surface. Unlike an optical image, we see the asteroid by reflected pulses of radio energy beamed from the antenna. To interpret them, we’ll need to put on our radar glasses.

Bright areas don’t necessarily appear bright to the eye because radar sees the world differently. Metallic asteroids appear much brighter than stony types; rougher surfaces also look brighter than smooth ones. In a sense these aren’t pictures at all but graphs of the radar pulse’s time delay, Doppler shift and intensity that have been converted into an image.

Another set of images of 2004 BL86 and its moon. Credit: NAIC Observatory / Arecibo Observatory — Another set of images of 2004 BL₈₆ and its moon. Credit: NAIC Observatory / Arecibo Observatory

In the images above, the left to right direction or x-axis in the photo plots the toward and away motion or Doppler shift of the asteroid. You’ll recall that light from an object approaching Earth gets bunched up into shorter wavelengths or blue-shifted compared to red-shifted light given off by an object moving away from Earth. A more rapidly rotating object will appear larger than one spinning slowly. The moon appears elongated probably because it’s rotating more slowly than the Alpha primary.

Meanwhile, the up and down direction or y-axis in the images shows the time delay in the reflected radar pulse on its return trip to the transmitter. Movement up and down indicates a change in 2004 BL86’s distance from the transmitter, and movement left to right indicates rotation. Brightness variations depend on the strength of the returned signal with more radar-reflective areas appearing brighter. The moon appears quite bright because – assuming it’s rotating more slowly – the total signal strength is concentrated in one small area compared to being spread out by the faster-spinning main body.

If that’s not enough to wrap your brain around, consider that any particular point in the image maps to multiple points on the real asteroid. That means no matter how oddly shaped 2004 BL₈₆ is in real life, it appears round or oval in radar images. Only multiple observations over time can help us learn the true shape of the asteroid.

You’ll often notice that radar images of asteroids appear to be lighted from directly above or below. The brighter edge indicates the radar pulse is returning from the leading edge of the object, the region closest to the dish. The further down you go in the image, the farther away that part of the asteroid is from the radar and the darker it appears.

Imagine for a moment an asteroid that’s either not rotating or rotating with one of its poles pointed exactly toward Earth. In radar images it would appear as a vertical line!

If you’re curious to learn more about the nature of radar images, here are two great resources:

* How Radio Telescopes Get “Images” of Asteroids by Emily Lakdawalla
* Goldstone Solar System Radar Observatory: Earth-Based Planetary Mission Support and Unique Science Results

January 30, 2015December 23, 2015 by Nancy Atkinson

It Looks Like an Asteroid Strike Can’t Cause a Worldwide, Dinosaur-Killing Firestorm

Computer generated simulation of an asteroid strike on the Earth. Credit: Don Davis/AFP/Getty Images

For decades, scientists have debated the cause of the mass extinction that wiped out the dinosaurs and other life 65 million years ago. While the majority of researchers agree that a massive asteroid impact at Chicxulub, Mexico is the culprit, there have been some dissenters. Now, new research is questioning just a portion of the asteroid/Cretaceous-Paleogene extinction scenario. While the scientists involved in the study don’t doubt that such an asteroid impact actually happened, their research shows it is just not possible that vast global firestorms could have ravaged our planet and be the main cause of the extinction.

Researchers from the University of Exeter, University of Edinburgh and Imperial College London recreated the vast energy released from a 15-km wide asteroid slamming into Earth, which occurred around the time that dinosaurs became extinct.

They found that close to the impact site — a 180 km wide crater in Mexico — the heat pulse would have lasted for less than a minute. This intense but short-lived heat, the team says, could not have ignited live plants, challenging the idea that the impact led to global firestorms.

However, they did find that the effects of the impact would actually be worse on the other side of the planet, where less intense but longer periods of heat could have ignited live plant matter.

“By combining computer simulations of the impact with methods from engineering we have been able to recreate the enormous heat of the impact in the laboratory,” said Dr. Claire Belcher from the University of Exeter. “This has shown us that the heat was more likely to severely affect ecosystems a long distance away, such that forests in New Zealand would have had more chance of suffering major wildfires than forests in North America that were close to the impact. This flips our understanding of the effects of the impact on its head and means that palaeontologists may need to look for new clues from fossils found a long way from the impact to better understand the mass extinction event.”

The Cretaceous-Paleogene extinction was one of the biggest in Earth’s history and geologic evidence of the impact has been discovered in rock layers around the world from this time period. Some critics of the asteroid impact theory as a cause of the extinction have pointed to some of the microfossils from the Gulf of Mexico that show the impact occurred well before the extinction and could not have been its primary cause. Others point to volcanism that produced the Deccan traps of India around this time as a possible cause of the extinction.

But multiple models have showed such an impact would have instantly caused devastating shock waves, tsunamis, and the release of large amounts of dust, debris and gases that would have led to a low light levels and a prolonged cooling of Earth’s surface. The darkness and a global winter would have decimated the planet life and the dependent animals.

So while fire and brimstone may not have played a big role in the Cretaceous-Paleogene extinction, there was plenty of destruction and mayhem for the resulting extinction of more than 70% of known species.

Here’s a video from the researchers that shows their findings that close to the impact site, the heat pulse was too short to ignite live plant material.

Their research is published in the Journal of the Geological Society.

Source: University Exeter