The planetoid Vesta, which was studied by the Dawn probe between July 2011 and September 2012. Credit: NASA
The brightest asteroid visible from Earth prowls across Cetus the Whale this month. Vesta shines at magnitude +6.3, right at the naked eye limit for observers with pristine skies, but easily coaxed into view with any pair of binoculars. With the moon now gone from the evening sky, you can start your search tonight.
Facing southeast around 10 p.m. local time in early October. 4 Vesta — its formal designation as the fourth asteroid discovered — travels along a short arc south of the easily-found star, Iota Ceti. Shoot a line from the Square of Pegasus south to arrive at Deneb Kaitos, Cetus’ brightest star, and from their to Iota Ceti and Vesta. Detailed map below. Source: Stellarium
Vesta came to opposition on September 28 and remains well-placed for viewing through early winter. Today’s it’s 134 million miles (225 million km) from Earth or about 5 million miles farther the Mars’ average distance from us. Although it’s one of the largest asteroids in the inner asteroid belt between Mars and Jupiter with a diameter of 326 miles (525 km), it never appears larger than a point of light even in many professional telescopes. Your binocular view will be as satisfying as the one through Mt. Palomar.
Like an inverted belly button, a spectacular central peak more than 14 miles high rises from the 310-mile-wide crater Rheasilvia. Credit: NASA
Discovered by the German astronomer Heinrich Olbers in March 1807, Vesta was named for the Roman goddess of home and hearth. NASA’s Dawn spacecraft, currently in orbit around another asteroid, Ceres, visited Vesta between July 2011 and September 2012, taking thousands of close-up images and measuring the mineral make-up of its soil and crust. We learned a few things while we were there:
Vesta is differentiated into crust, mantle and core just like the bigger planets are. That’s why you’ll sometimes hear it described as a “protoplanet”, the first of its kind discovered in our solar system.
A class of igneous meteorites fallen to Earth called Howardites, eucrites and diogenites (HED-meteorites) were confirmed as actual pieces of the asteroid that found their way here after being blasted into space by impact.
Some of the meteorites / rocks that pelted the asteroid from elsewhere in the solar system are water-rich.
Vesta’s covered in craters like the moon
A staggering-large 310-mile-wide (500 km) impact crater named Rheasilvia marks its south pole. The basin’s central peak rises to 14.3 miles (23 km), more than twice the height of Mt. Everest.
Cornelia Crater on the asteroid Vesta. The crater is about 4 to 5 million years old. On the right is an inset image showing an example of curved gullies that may have been carved by water, indicated by the short white arrows, and a fan-shaped deposit, indicated by long white arrows. The inset image is about 0.62 miles (1 km) wide. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
You can see it all in your mind’s eye the next clear night. For skywatchers at mid-northern latitudes, Vesta climbs into good view around 10 o’clock in early October and 8 o’clock by month’s end. If you’re familiar with gangly Cetus, you can start with the 2nd magnitude star Deneb Kaitos, the brightest star in the constellation. If not, begin your Vestan voyage from the Great Square in Pegasus, high in the southeastern sky.
Once you’ve arrived at Deneb Kaitos, locate Iota Ceti, 10 degrees to the northwest. The star makes finding Vesta easy in binoculars this month. Stars shown to magnitude +7. North is up and the asteroid’s position is marked every 5 days at 10 p.m. Vesta fades slowly during the month to mag. 6.8 by Nov. 1. CDT. Source: Chris Marriott’s SkyMap software
Drop a line through the two stars along the left side of the Square and continue it down toward the southern horizon. You’ll run right into DK. Now elevate your gaze — or aim your binoculars — one outstretched fist (10°) or about two binocular fields of view above and right of Deneb Kaitos to find Iota Ceti (mag. 3.6).
Once you’ve got Iota, the asteroid will be in your field of view close by. Use the detailed chart to pinpoint its location with respect to Iota. Easy, right? Well, I hope so. Bon voyage to Vesta!
36 years ago today, a strange event was detected over the Southern Indian Ocean that remains controversial. On September 22nd, 1979, an American Vela Hotel satellite detected an atmospheric explosion over the southern Indian Ocean near the Prince Edward Islands. The event occurred at 00:53 Universal Time on the pre-dawn nighttime side of the Earth. Vela’s gamma-ray and x-ray detectors rang out in surprise, along with its two radiometers (known as Bhangmeters) which also captured the event.
The approximate location of the flash seen by the Vela-5b satellite Image credit: Wikimedia Commons/public domain
What was it?
Even today, the source of the Vela Incident remains a mystery. Designed to detect nuclear detonations worldwide and enforce the Partial Nuclear Test Ban Treaty, the Vela satellites operated for about ten years and were also famous for discovering evidence for extra-galactic gamma-ray bursts.
A Vela payload in the lab. Image credit: The U.S. Department of Defense
Vela-5B was the spacecraft from the series that detected the mysterious flash. A Titan-3C rocket launched Vela 5B (NORAD ID 1969-046E) on May 23rd, 1969 from Vandenberg Air Force Base in California.
One of the first things scientists realized early on in the Cold War is that the Universe is a noisy place, and that this extends across the electromagnetic spectrum. Meteors, lightning, cosmic rays and even distant astrophysical sources can seem to mimic certain signature aspects of nuclear detonations. The ability to discern the difference between human-made and natural events became of paramount importance and remains so to this day: the hypothetical scenario of a Chelyabinsk-style event over two nuclear armed states already on a political hair-trigger edge is a case in point.
Over the years, the prime suspect for the Vela Incident has been a joint South African-Israeli nuclear test. The chief piece of evidence is the characteristic ‘double-flash’ recorded by Vela, characteristic of a nuclear detonation. Said event would’ve been an approximately 3 kiloton explosion; for context, the bomb dropped on Hiroshima had a 15 kiloton yield, and the Chelyabinsk event had an estimated equivalent explosive force of 500 kilotons. As a matter of fact, the Vela Incident became a topic of discussion on the day Chelyabinsk occurred, as we sought to verify the assertion of whether Chelyabinsk was ‘the biggest thing’ since the 1908 Tunguska event.
A bolide event captured over Pennsylvania in early 2015. Image credit: Bill Ingalls/NASA
The Carter administration played down the Vela Incident at the time, though U.S. Air Force dispatched several WC-135B surveillance aircraft to the area, which turned up naught. Though detectors worldwide reported no increase of radioactive fallout, the ionospheric observatory at Arecibo did detect an atmospheric wave on the same morning as the event.
Israel ratified the Limited Test Ban Treaty in 1964. To date, Israel has never acknowledged that the test took place or the possession of nuclear weapons. Over the years, other suspect states have included Pakistan, France and India. Today, probably the only true final confirmation would come from someone stepping forward who was directly involved with the test, as it must have required the silence of a large number of personnel.
A comparison of the Vela event with a known nuclear test and a typical “zoo event’. Image credit: Vela Event Alert 747, Los Alamos Nat’l Laboratory
Was it a reentry or a bolide? Again, the signature double flash seen by the Vela satellite makes it unlikely. A micrometeoroid striking the spacecraft could have caused an anomalous detection known as a ‘zoo event,’ mimicking a nuclear test. Los Alamos researchers who have analyzed the event over the years remain convinced in the assertion that the 1979 Vela Incident had all the hallmark signatures of a nuclear test.
A U.S. nuclear detonation during Operation Upshot-Knothole in 1953. Image credit: National Nuclear Security Administration/Public Domain
Shortly after the Cold War, the U.S. Department of Defense made much of its atmospheric monitoring data public, revealing that small meteorites strike us much more often than realized. Sadly, this type of continual monitoring accompanied by public data release has declined in recent years mostly due to budgetary concerns, though monitoring of the worldwide environment for nuclear testing via acoustic microphone on land, sea and eyes overhead in space continues.
And it’s frightening to think how close we came to a nuclear exchange during the Cold War on several occasions. For example: in 1960, an Distant Early Warning System based in Thule, Greenland mistook the rising Moon for a Soviet missile launch (!) The United States also conducted nuclear tests in space shortly before the Test Ban Treaty went into effect, including Starfish Prime:
The Vela Incident remains a fascinating chapter of the Cold War, one where space and the geopolitical intrigue overlap. Even today, parsing out the difference between human-made explosions and the cataclysmic events that pepper the cosmos remains a primary concern for the continued preservation of our civilization.
Tactical nuclear weapons from around the world seen on display at the Nuclear Science Museum in Albuquerque, New Mexico. Image credit: Dave Dickinson
-Listen to an interesting discussion on monitoring nuclear plants worldwide via neutrino emissions.
-For a fascinating in-depth discussion on the continued relevance of the Vela Incident, check out this recent article by The Bulletin of Atomic Scientists.
Observational astronomy is a study in patience. Since the introduction of the telescope over four centuries ago, steely-eyed observers have watched the skies for star-like or fuzzy points of light that appear to move. Astronomers of yore discovered asteroids, comets and even the occasional planet this way. Today, swiftly moving satellites have joined the fray. Still other ‘new stars’ turn out to be variables or novae.
Tombaugh’s mechanical ‘steampunk starblinker’ on display at the Lowell observatory. Image credit: Dave Dickinson
The advent of photography in the late 19th century upped the game… you’ll recall that Clyde Tombaugh used a blink comparator to discover Pluto from the Lowell Observatory in 1930. Clyde’s mechanical shutter device looked at glass plates in quick sequence. Starblinker takes this idea a step further, allowing astro-imagers to compare two images in rapid sequence in a similar ‘blink comparator’ fashion. You can even quickly compare an image against one online from, say, the SDSS catalog or Wikipedia or an old archival image. Starblinker even automatically orients and aligns the image for you. Heck, this would’ve been handy during a certain Virtual Star Party early last year hosted by Universe Today, making the tale of the ‘supernova in M82 that got away’ turn out very differently…
Often times, a great new program arises simply because astrophotographers find a need where no commercial offering exists. K3CCD Tools, Registax, Orbitron and Deep Sky Stacker are all great examples of DIY programs that filled a critical astronomy need which skilled users built themselves.
“I started to code the software after the mid of last month,” Starblinker creator Marco Lorrai told Universe Today. “I knew there was a plugin for MaximDL to do this job, but nothing for people like me that make photos just with a DSLR… I own a 250mm telescope, and my images go easily down to magnitude +18 so it is not impossible to find something interesting…”
Starblinker is a free application, and features a simple interface. Advanced observers have designed other programs to sift through video and stacks of images in the past, but we have yet to see one with such a straight-forward user interface with an eye toward quick and simple use in the field.
Starblinker screenshot. Image credit: Marco Lorrai
“The idea came to me taking my astrophotos: many images are so rich with stars, why not analyze (them) to check if something has changed?” Lorrai said. “I started to do this check manually, but the task was very thorny, because of differences in scale and rotation between the two images. Also, the ‘blinking’ was done loading two alternating windows containing two different images… not the best! This task could be simplified if someone already has a large set of images for comparison with one old image (taken) with the same instrument… a better method is needed to do this check, and then I started to code Starblinker.”
Why Starblinker
I can see a few immediate applications for Starblinker: possible capture of comets, asteroids, and novae or extragalactic supernovae, to name a few. You can also note the variability of stars in subsequent images. Take images over the span of years, and you might even be able to tease out the proper motion of nearby fast movers such as 61 Cygni, Kapteyn’s or even Barnard’s Star, or the orbits of double stars. Or how about capturing lunar impacts on the dark limb of the Moon? It may sound strange, but it has been done before… and hey, there’s a lunar eclipse coming right up on the night of September 27/28th. Just be careful to watch for cosmic ray hits, hot pixels, satellite and meteor photobombs, all of which can foil a true discovery.
The Dumbell Nebula (M27). Note the (possible) variable star (marked). Image credit: Marco Lorrai
“A nice feature to add could be the support for FITS images and I think it could be very nice that… the program could retrieve automatically a comparison image, to help amateurs that are just starting (DSLR imaging).” Lorrai said.
And here is our challenge to you, the skilled observing public. What can YOU do with Starblinker? Surprise us… as is often the case with any hot new tech, ya just never know what weird and wonderful things folks will do with it once it’s released in the wild. Hey, discover a comet, and you could be immortalized with a celestial namesake… we promise that any future ‘Comet Dickinson’ will not be an extinction level event, just a good show…
Think you’ve discovered a comet? Nova? A new asteroid? Inbound alien invasion fleet? OK, that last one might be tweet worthy, otherwise, here’s a handy list of sites to get you started, with the checklist of protocols to report a discovery used by the pros:
Artist's depiction of the asteroid belt between Mars and Jupiter. Credit: David Minton and Renu Malhotra
4.6 billion years ago, our Solar System formed from a collection of gas and dust surrounding our nascent Sun. While much of the gas and dust in this protoplanetary disk coalesced to form the planets, some of the debris was left over.
Some of debris was shattered remnants of planetesimals – bodies within the young Sun’s solar nebula that never grew large enough to become planets, and scientists theorize that large collisions in the early, chaotic Solar System pulverized these planetesimals into smaller pieces. Other debris never came together due to the massive gravitational pull from Jupiter.
These rocky remnants are now the asteroids that travel about our Solar System. Since these “leftovers” contain clues about the early days of our Solar System, scientists are eager to study them.
Definition of an Asteroid
Asteroids are rocky, metallic bodies that orbit the Sun. They are made from different kinds of rock and metals, with the metals being mostly nickel and iron. They are sometimes called “minor planets” but they are much, much smaller than the planets or moons. They don’t have atmospheres, but about 150 asteroids are known to have small “moons” orbiting them, and some even have two moons. There are also binary (double) asteroids, where two rocky bodies of roughly equal size orbit each other, as well as triple asteroid systems.
At least one asteroid has rings. This surprise discovery was made in 2013 when scientist watched Asteroid Chariklo pass in front of a star. The asteroid made the background star “blink” several times, which led to the discovery that two rings are surrounding the asteroid.
The asteroids of the inner Solar System and Jupiter: The donut-shaped asteroid belt is located between the orbits of Jupiter and Mars. Credit: Wikipedia Commons
Location
The majority of known asteroids are in the asteroid belt, a large donut-shaped ring located between the orbits of Mars and Jupiter, and orbit approximately 2 to 4 AU (186 million to 370 million miles/300 million to 600 million kilometers) from the Sun. (*Note: 1 AU, or Astronomical Unit, equals the distance from the Earth to the Sun.)
Sometimes, the orbits of some asteroids get perturbed or altered from gravitational interactions with planets or other asteroids and they end up coming closer to the Sun, and therefore closer to Earth. These asteroids are known as Near Earth Asteroids, and are classified as NEAs if their orbits bring them within 1.3 AU (121 million miles/195 million kilometers) of the Earth.
Asteroids that actually cross Earth’s orbital path are known as Earth-crossers and, an asteroid is called a Potentially Hazardous Asteroid (PHA) if it will come less than .05 AU from Earth.
In addition to the asteroid belt, however, there have been recent discussions among astronomers about the potential existence of large number asteroids in the far reaches of our Solar System in the Kuiper Belt and Oort Cloud.
Number of Asteroids
There are millions of asteroids in our Solar System. Some scientists estimate the asteroid belt has between 1.1 and 1.9 million asteroids larger than 1 kilometer (0.6 mile) in diameter, and millions of smaller ones. Most of the undiscovered asteroids are likely the smaller ones (less than 100 km across) which are more difficult to detect. Other astronomers estimate there are over 150 million asteroids in the entire Solar System. New asteroids are being discovered all the time.
On average, three new NEAs are found every day. As of September 06, 2015, 13,024 Near-Earth objects have been discovered. About 875 of these NEOs are asteroids with a diameter of approximately 1 kilometer or larger. Also, 1,609 of these NEOs have been classified as Potentially Hazardous Asteroids (PHAs), but none at this time are expected to impact Earth. Check the NASA NEO website for updates.
Contrary to popular imagery that might be seen in science fiction movies and imagery, the asteroid belt is mostly empty. According to NASA, the average distance between objects in the asteroid belt is greater than 1-3 million km. The asteroids are spread over such a large volume that you likely would not run into an asteroid if you sent a spacecraft through the asteroid belt. Even though there may be millions of asteroids in the asteroid belt, most are small. Astronomers say if you put all of them together, the combination would be smaller than our moon.
Asteroids are not easy to spot because they often are made from dark material, and are difficult to find against the darkness of outer space. There are several dedicated surveys using both Earth-based telescopes and spacecraft searching the skies for asteroids. They include:
Catalina Sky Survey
Pan-STARRS
LINEAR
Spacewatch
NEOWISE
You can find more information about NASA’s NEO Search Program here.
Ceres compared to asteroids visited to date, including Vesta, Dawn’s mapping target in 2011. Image by NASA/ESA/JAXA. Compiled by Paul Schenck.
Shape and Size
Most asteroids are irregularly shaped, though some are nearly spherical, and they are often pitted or cratered from impacts with other asteroids. As they revolve around the Sun in elliptical orbits, the asteroids also rotate, and have some quite erratic movements, and literally tumble through space.
The size of what classifies as an asteroid is not extremely well defined, as an asteroid can range from a pebbles, to a few meters wide – like a boulder — to objects that are hundreds of kilometers in diameter. The largest asteroid is asteroid Ceres at about 952 km (592 miles) in diameter, and Ceres is so large that it is also categorized as a dwarf planet. Over 200 asteroids are known to be larger than 100 km (60 miles), with sixteen asteroids known to have diameters of 240 kilometers (150 miles) or greater.
Asteroids we’ve seen up close show various shapes. Credit: NASA
The following animation is based on a 2008 a study of the size distribution of asteroid families using data from the Sloan Digital Sky Survey and was created by Alex Parker.
Composition
Most asteroids are made of rock — with some composed of clay and silicate — and different metals, mostly nickel and iron. Other precious metals have been found on some asteroids, including platinum and gold. A wide variety of minerals have also been found on various asteroids including olivine and pyroxene, which are also found on meteorites that have landed on Earth.
Most asteroids contain vast amounts of carbon, which means they closely follow the elemental composition of the Sun. There are indications that asteroids also contain water or ice in their interiors, and observations by the Dawn mission shows indications that water may have flowed across the surface of Vesta.
You can find more details about what asteroids are made of at our article here.
Asteroids are different from comets, which are mostly rock and ice. Comets usually have tails, which are made from ice and debris sublimating as the comet gets close to the Sun. Asteroids typically don’t have tails, even those near the Sun. But recently, astronomers have seen some asteroids that have sprouted tails, such as asteroid P/2010 A2. This seems to happen when the asteroid has been hit or pummeled by other asteroids and dust or gas is ejected from their surfaces, creating a sporadic tail effect. These so-called “active asteroids” are a newly recognized phenomenon, and as of this writing, only 13 known active asteroids have been found in the main asteroid belt, and so they are very rare.
Asteroid classifications
Asteroids have a few different classifications based on their location and make-up.
Location classifications are:
Main Belt Asteroids: (which includes the majority of known asteroids which orbit within the asteroid belt between Mars and Jupiter)
Trojans: These asteroids share an orbit with a larger planet, but do not collide with it because they gather around two special places in the orbit (called the L4 and L5 Lagrangian points). There, the gravitational pull from the sun and the planet are balanced by a trojan’s tendency to otherwise fly out of the orbit. The Jupiter trojans form the most significant population of trojan asteroids. It is thought that they are as numerous as the asteroids in the asteroid belt. There are Mars and Neptune trojans, and NASA announced the discovery of an Earth trojan in 2011.
Near-Earth Asteroids: These objects have orbits that pass close by that of Earth.
Then, there are subgroups of Near-Earth asteroids, and are categorized by their orbits.
Atiras are NEAs whose orbits are contained entirely with the orbit of the Earth, having a distance of less than 1 AU. They are named after asteroid 163693 Atira.
Atens are Earth-crossing NEAs with semi-major axes smaller than Earth’s, with a distance of less than 1 AU. They are named after asteroid 2062 Aten.
Apollos are Earth-crossing NEAs with semi-major axes larger than Earth’s, with a distance of less than 1 AU. They are named after asteroid 1862 Apollo.
Amors are Earth-approaching NEAs with orbits outside of Earth’s but inside of Mars’ orbit. They are named after asteroid 1221 Amor.
Classification by the composition tell us what the asteroid is made of, and this is related to how far from the Sun an asteroid formed. Some experienced high temperatures after they formed and partly melted, with iron sinking to the center and forcing basaltic (volcanic) lava to the surface. Only one such asteroid, Vesta, survives to this day. There are three basic types of asteroids:
C-type (chondrite) asteroids are most common, making up about 75 percent of known asteroids. They are very dark in appearance and probably consist of clay and silicate rocks. They are among the most ancient objects in the solar system. Their composition is thought to be similar to the Sun, but depleted in hydrogen, helium, and other volatiles. C-type asteroids mainly are in the asteroid belt’s outer regions.
S-types (stony) are made up of silicate materials and nickel-iron, and accounts for about 17 percent of known asteroids. They are brighter than C-type and they dominate the inner asteroid belt.
M-types (metallic) are made from nickel and iron and accounts for about 8 percent of known asteroids. They are brighter than C-type and they can be found in the asteroid belt’s middle region.
Asteroid Impacts with Earth
How likely is it that our planet could be hit by a large asteroid or comet? We do know that Earth and the Moon have been struck many times in the past by asteroids whose orbits bring them into the inner Solar System. You can see pictures some of Earth’s largest and most spectacular impact craters here.
Studies of Earth’s history indicate that about once every 5,000 years or so (on average) an object the size of a football field hits Earth and causes significant damage. Once every few million years on average an object large enough to cause regional or global disaster impacts Earth.
Satellite views of the Chicxulub impact site. Image credit: NASA/JPL
There is strong scientific evidence that asteroid impacts played a major role in the mass extinctions documented in Earth’s fossil records. It is widely accepted that an impact 65 million years ago of an asteroid or comet at least 6 miles (10 kilometers) in diameter in the Yucatan peninsula, known as the Chicxulub crater is associated with the extinction of the dinosaurs.
We know of only a handful of recent large asteroid impacts. 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, breaking windows and injuring many, mostly from broken glass.
But a recent study by the B612 Foundation found that there were 26 explosive airburst events similar to the Chelyabinsk event recorded from 2000 to 2013. The explosions asteroids ranged from one to 600 kilotons in energy output.
NASA says that about once a year, an automobile-sized asteroid hits Earth’s atmosphere, creates an impressive fireball, and burns up before reaching the surface.
NEOs still pose a danger to Earth today, but NASA, ESA and other space agencies have search programs that have discovered hundreds of thousands of main-belt asteroids, comets. None at this time pose any threat to Earth. You can find out more on this topic at NASA’s Near Earth Object Program website.
All asteroids and comets visited by spacecraft as of November 2010 Credits: Montage by Emily Lakdawalla. Ida, Dactyl, Braille, Annefrank, Gaspra, Borrelly: NASA / JPL / Ted Stryk. Steins: ESA / OSIRIS team. Eros: NASA / JHUAPL. Itokawa: ISAS / JAXA / Emily Lakdawalla. Mathilde: NASA / JHUAPL / Ted Stryk. Lutetia: ESA / OSIRIS team / Emily Lakdawalla. Halley: Russian Academy of Sciences / Ted Stryk. Tempel 1, Hartley 2: NASA / JPL / UMD. Wild 2: NASA / JPL.
History
We’ve gained knowledge of asteroids from three main sources: Earth-based remote sensing, data from spacecraft and laboratory analysis of meteorites.
Here are some important dates in the history of our knowledge and study of asteroids, including spacecraft missions that flew by or landed on asteroids:
1801: Giuseppe Piazzi discovers the first and largest asteroid, Ceres, orbiting between Mars and Jupiter. 1898: Gustav Witt discovers Eros, one of the largest near-Earth asteroids. 1991-1994: The Galileo spacecraft takes the first close-up images of an asteroid (Gaspra) and discovers the first moon (later named Dactyl) orbiting an asteroid (Ida). 1997-2000: The NEAR Shoemaker spacecraft flies by Mathilde and orbits and lands on Eros. 1998: NASA establishes the Near Earth Object Program Office to detect, track and characterize potentially hazardous asteroids and comets that could approach Earth. 2006: Japan’s Hayabusa becomes the first spacecraft to land on, collect samples and take off from an asteroid. 2006: Ceres attains a new classification — dwarf planet — but retains its distinction as the largest known asteroid. 2007: The Dawn spacecraft is launched on its journey to the asteroid belt to study Vesta and Ceres. 2008: The European spacecraft Rosetta, on its way to study a comet in 2014, flies by and photographs asteroid Steins, a type of asteroid composed of silicates and basalts. 2010: Japan’s Hayabusa returns its asteroid sample to Earth. 2010: Rosetta flies by asteroid Lutetia, revealing a primitive survivor from the violent birth of our solar system. 2011-2015: Dawn studies Vesta, becoming the first spacecraft to orbit a main-belt asteroid. It now is studying the dwarf planet Ceres, located in the main asteroid belt.
Below is a list of links to articles about asteroids in general, asteroid related events in history, and some specific asteroids. Many hours of research are waiting for you. Enjoy!
Topographic elevation map of Ceres showing some newly-named craters. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA.
Ceres’ topography is revealed in full (but false) color in a new map created from elevation data gathered by NASA’s Dawn spacecraft, now nearly five months in orbit around the dwarf planet orbiting the Sun within the main asteroid belt.
With craters 3.7 miles (6 km) deep and mountains rising about the same distance from its surface, Ceres bears a resemblance to some of Saturn’s frozen moons.
“The craters we find on Ceres, in terms of their depth and diameter, are very similar to what we see on Dione and Tethys, two icy satellites of Saturn that are about the same size and density as Ceres,” said Paul Schenk, Dawn science team member and a geologist at the Lunar and Planetary Institute (LPI) in Houston, TX. “The features are pretty consistent with an ice-rich crust.”
Check out a rotation video of Ceres’ topography below:
In addition to elevation mapping Ceres has also had some of its more prominent craters named. No longer just “bright spot crater” and “Spot 1,” these ancient impact scars now have official IAU monikers… from the Roman Occator to the Hawaiian Haulani to the Hopi Kerwan, craters on Ceres are named after agriculture-related gods and goddesses of mythologies from around the world.
Ceres’ famous “bright spot” crater is now named Occator, after the Roman god of harrowing. (NASA/JPL-Caltech/UCLA/MPS/DLR/IDA)
Dawn is currently moving closer toward Ceres into its third mapping orbit. By mid-August it will be 900 miles (1448 km) above Ceres’ surface and will proceed with acquiring data from this lower altitude, three times closer than it has been previously.
At 584 miles (940 km) in diameter Ceres is about 40 percent the size of Pluto.
NASA’s Dawn spacecraft is the first to successfully enter orbit around two different mission targets and the first to orbit a dwarf planet. Its first target was the asteroid Vesta, which it orbited from July 2011 to September 2012. Dawn arrived in orbit at Ceres on March 6, 2015 and there it will remain during its primary science phase and beyond; Ceres is now Dawn’s permanent home.
Ceres (left, Dawn image) compared to Tethys (right, Cassini image) at comparative scale sizes. (Credits: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA and NASA/JPL-Caltech/SSI. Comparison by J. Major.)
Move over, Pluto... Disney already has dibs on Mercury as seen in this MESSENGER photo. Image credit: NASA/JHAPL/Carnegie institution of Washington
“Look, it has a tiny face on it!”
This sentiment was echoed ‘round the web recently, as an image of Pluto’s tiny moon Nix was released by the NASA New Horizons team. Sure, we’ve all been there. Lay back in a field on a lazy July summer’s day, and soon, you’ll see faces of all sorts in the puffy stratocumulus clouds holding the promise of afternoon showers.
Pluto’s moon Nix as imaged by New Horizons from 590,000 kilometers distant. Image credit: NASA/JHUAPL/SWRI
This predilection is so hard-wired into our brains, that often our facial recognition software sees faces where there are none. Certainly, seeing faces is a worthy survival strategy; not only is this aspect of cognition handy in recognizing the friendlies of our own tribe, but it’s also useful in the reading of facial expressions by giving us cues of the myriad ‘tells’ in the social poker game of life.
And yes, there’s a term for the illusion of seeing faces in the visual static: pareidolia. We deal lots with pareidolia in astronomy and skeptical circles. As NASA images of brave new worlds are released, an army of basement bloggers are pouring over them, seeing miniature bigfoots, flowers, and yes, lots of humanoid figures and faces. Two craters and the gash of a trench for a mouth will do.
Now that new images of Pluto and its entourage of moons are pouring in, neural circuits ‘cross the web are misfiring, seeing faces, half-buried alien skeletons and artifacts strewn across Pluto and Charon. Of course, most of these claims are simply hilarious and easily dismissed… no one, for example, thinks the Earth’s Moon is an artificial construct, though its distorted nearside visage has been gazing upon the drama of humanity for millions of years.
Do you see the ‘Man in the Moon?’ Image credit: Dave Dickinson
The psychology of seeing faces is such that a whole region of the occipital lobe of the brain known as the fusiform face area is dedicated to facial recognition. We each have a unique set of neurons that fire in patterns to recognize the faces of Donald Trump and Hillary Clinton, and other celebs (thanks, internet).
Damage this area at the base of the brain or mess with its circuitry, and a condition known as prosopagnosia, or face blindness can occur. Author Oliver Sacks and actor Brad Pitt are just a few famous personalities who suffer from this affliction.
The ‘Snowman of Vesta,’ as imaged by NASA’s Dawn spacecraft. Image credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Conversely, ‘super-recognizers’ at the other end of the spectrum have a keen sense for facial identification that verges on a super-power. True story: my wife has just such a gift, and can immediately spot second-string actors and actresses in modern movies from flicks and television shows decades old.
It would be interesting to know if there’s a correlation between face blindness, super-recognition and seeing faces in the shadows and contrast on distant worlds… to our knowledge, no such study has been conducted. Do super-recognizers see faces in the shadowy ridges and craters of the solar system more or less than everyone else?
A well-known example was the infamous ‘Face on Mars.’ Imaged by the Viking 1 orbiter in 1976, this half in shadow image looked like a human face peering back up at us from the surface of the Red Planet from the Cydonia region.
Image credit: The ‘Face on Mars’: HiRISE vs Viking 1 (inset): Image credit: NASA/JPL
But when is a face not a face?
Now, it’s not an entirely far-fetched idea that an alien entity visiting the solar system would place something (think the monolith on the Moon from Arthur C. Clarke’s 2001: A Space Odyssey) for us to find. The idea is simple: place such an artifact so that it not only sticks out like a sore thumb, but also so it isn’t noticed until we become a space-faring society. Such a serious claim would, however, to paraphrase Carl Sagan, demand serious and rigorous evidence.
But instead of ‘Big NASA’ moving to cover up the ‘face,’ they did indeed re-image the region with both the Mars Reconnaissance Orbiter and Mars Global Surveyor at a much higher resolution. Though the 1.5 kilometer feature is still intriguing from a geological perspective… it’s now highly un-facelike in appearance.
A ‘face’ or… more fun with ‘scifi spacecraft pareidolia.’ Image credit: NASA/JPL/Paramount Pictures
Of course, it won’t stop the deniers from claiming it was all a big cover-up… but if that were the case, why release such images and make them freely available online? We’ve worked in the military before, and can attest that NASA is actually the most transparent of government agencies.
We also know the click bait claims of all sorts of alleged sightings will continue to crop up across the web, with cries of ‘Wake up, Sheeople!’ (usually in all caps) as a brave band of science-writing volunteers continue to smack down astro-pareidolia on a pro bono basis in battle of darkness and light which will probably never end.
What examples of astro-pareidolia have you come across in your exploits?
The brightest spots on dwarf planet Ceres are seen in this image taken by NASA's Dawn spacecraft on June 6, 2015. The picture was taken from an altitude of 2,700 miles (4,400 kilometers). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
The crater that contains those puzzlingly bright spots on Ceres may harbor an equally puzzling haze. Or not. The hints of haze on the dwarf planet, seen in some of the images coming from NASA’s Dawn spacecraft, add another intriguing twist to Ceres’ mysteries.
The hubbub over haze arose this week during the Exploration Science Forum at NASA’s Ames Research Center in California. For months, Dawn’s scientists have been observing – and trying to make sense out of – unusually reflective spots within Ceres’ craters that show up when the asteroid turns into the sunlight. The team has speculated that they could be frozen pools of water ice, or patches of light-colored, salt-rich material.
The brightest spots are known collectively as Spot 5, and sit inside Occator Crater on Ceres. Dawn’s principal investigator, Chris Russell of the University of California at Los Angeles, told the forum that some type of haze could be seen inside the crater at certain times of Ceres’ day, according to reports from Nature and the Planetary Society. Nature quoted Russell as saying the bright spots “could be providing some atmosphere in this particular region of Ceres.”
Last year, scientists with the European Space Agency’s Herschel mission reported detecting signs of water vapor rising from Ceres’ surface, and it would be tempting to suggest that the water vapor is emanating from bright icy spots and creating the haze. That would strengthen Ceres’ status as the only asteroid with a significant atmosphere and a subsurface reservoir of water, and stoke speculation about life on Ceres.
However, Russell told Universe Today that it’s way too early to give in to temptation.
“I was speaking from less than a handful of images, and the interpretation of the images is disputed by some team members,” Russell said in an email. “I would like the debate to go on internally before we make a pronouncement one way or the other. I of course have my personal opinion, but I am not always right.”
Russell said the ice-vs.-salt debate is continuing. “I originally was an advocate of ice, because of how bright the spots seemed to be,” he said. However, the bright material’s albedo, or reflectivity factor, is about 50 percent – which is less than Russell originally thought. “This could be salt and is unlikely to be ice. I think the team opinion is now more in line with salt,” he said.
Either way, Russell doesn’t see any way for the spots to form without internal activity on Ceres. “Thus, the very existence of the spots tells us that there is some active process going on,” he told Universe Today.
Will we ever know if the haze is for real? Or what the spots are made of? As the Magic 8-Ball might say, “Ask again later.” The Dawn spacecraft recently recovered from a mechanical glitch and is gradually descending to a closer mapping orbit, around an altitude of 900 miles (1,500 kilometers). That will provide a much better look at Occator Crater and what lies within.
“Eventually I am expecting the spectral data will unambiguously tell us what has happened to the surface,” Russell said, “but it is a little too soon to be sure.”
This image of Ceres was taken by NASA's Dawn spacecraft on May 7, 2015, from a distance of 8,400 miles (13,600 kilometers). Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Video caption: This new video animation of Ceres was created from images taken by NASA’s Dawn spacecraft at altitudes of 8,400 miles (13,600 kilometers) and 3,200 miles (5,100 kilometers) away. Vertical dimension has been exaggerated by a factor of two and a star field added. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Scientists leading NASA’s Dawn mission to dwarf planet Ceres have just released a brand new animated video showing a dramatic fly over of the heavily cratered world featuring its mysterious bright spots whose exact origin and nature remain elusive.
Meanwhile, the venerable probe has just successfully entered its new and lower mapping orbit on June 3 from which researchers hope to glean hordes of new data to unravel the secrets of the bright spots and unlock the nature of Ceres origin and evolution.
Pockmarked Ceres is an alien world unlike any other in our solar system.
“Dawn completed the maneuvering to reach its second mapping orbit and stopped ion-thrusting on schedule. Since May 9, the spacecraft has reduced its orbital altitude from 8,400 miles (13,600 kilometers) to 2,700 miles (4,400 kilometers),” reported Marc Rayman, Dawn Chief Engineer/ Mission Director of NASA’s Jet Propulsion Laboratory, Pasadena, California.
“As Dawn flew 2,700 miles (4,400 kilometers) over Ceres’ north pole on June 5 that marked the beginning of the new mapping phase, and Dawn began taking photos and making other measurements on schedule.”
Each orbit of Dawn around Ceres at this second science mapping orbit lasts 3.1 days.
The new video was created by the research team based on observations of Ceres that were taken from Dawn’s initial mapping orbit, at an altitude of 8,400 miles (13,600 kilometers), as well as the most recent navigational images taken from 3,200 miles (5,100 kilometers), according to NASA.
It is based on data from over 80 images captured by Dawn’s framing cameras which were provided The German Aerospace Center (DLR) and Max Planck Institute for Solar System Research in Göttingen, Germany.
The images were used to provide a three-dimensional video view. The vertical dimension is exaggerated by a factor of two in the video.
“We used a three-dimensional terrain model that we had produced based on the images acquired so far,” said Dawn team member Ralf Jaumann of the German Aerospace Center (DLR), in Berlin.
“They will become increasingly detailed as the mission progresses — with each additional orbit bringing us closer to the surface.”
Imagery of the mysterious bright spots show them to seemingly be sheets of many spots of water ice, and not just single huge patches. The famous duo of ice spots are located inside the middle of a 57 miles (92 kilometers) wide crater situated in Ceres northern hemisphere.
Dawn is an international science mission managed by NASA’s Jet Propulsion Laboratory, Pasadena, California. The trio of science instruments are from the US, Germany and Italy.
The framing camera was provided by the Max Planck Institute for Solar System Research, Göttingen, Germany and the German Aerospace Center (DLR).
This view of Ceres was taken by Dawn spacecraft on May 23 and shows finer detail becoming visible on the dwarf planet. The spacecraft snapped the image at a distance of 3,200 miles (5,100 kilometers) with a resolution of 1,600 feet (480 meters) per pixel. Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Dawn will spend most if June at this second mapping orbit before firing up the ion engines and spiraling yet lower for a mission expected to last until at least June 2016.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
Dawn’s spiral descent from its first mapping orbit (RC3) to its second (survey). The two mapping orbits are shown in green. The color of Dawn’s trajectory progresses through the spectrum from blue, when it began ion-thrusting on May 9, to red, when ion-thrusting concludes on June 3. The red dashed sections show where Dawn is coasting, mostly for telecommunications. The first two coast periods include OpNav 8 and 9. Image credit: NASA/JPL-Caltech
On June 2, 2015 a small asteroid - Nimoy - was named for Leonard Nimoy who played the fictional Mr. Spock in Star Trek. Credit: NASA/JPL
“Fascinating, Captain.” If he were alive today, Leonard Nimoy, who played the half Vulcan-half human Mr. Spock in the Star Trek TV and movies series, would undoubtedly have raised an eyebrow and uttered a signature “fascinating” at the news this week that an asteroid now bears his name.
4864 Nimoy, a mountain-sized rock roughly 6 miles (10 km) across, orbits the Sun once every 3.9 years within the inner part of the main asteroid belt between Mars and Vulcan, er Jupiter.
Here’s the announcement from the Minor Planet Center made on June 2:
Leonard Nimoy as Mr. Spock. Credit: CBS Television
(4864) Nimoy = 1988 RA5
Discovered 1988 Sept. 2 by H. Debehogne at the European Southern Observatory.
Leonard Nimoy (1931–2015) was an American actor, film director and poet. Best known for his portrayal of the half-Vulcan/half-human science officer Spock in the original “Star Trek” TV series and subsequent movies, Nimoy wrote two autobiographies:
I Am Not Spock (1975) and I Am Spock (1995). M.P.C. 94384
4864 Nimoy was discovered by Belgian astronomer Henri Debehogne on September 2, 1988 and given the provisional designation 1988 RA5. This month, Spock’s “star” doesn’t get any brighter than 16th magnitude as it slowly tracks from Capricornus into Sagittarius in the late night sky. Come mid-July, amateurs with 14-inch or larger telescopes might glimpse it when it brightens to magnitude 15.
Spock – Fascinating!
Though portrayed as logical to a fault, Spock’s chilly exterior hid a heart as big as Jupiter. He was the hero of every nerd, and the perfect foil to Shatner’s Captain Kirk’s emotional excesses. Nimoy’s character showed that command of the facts and rational thinking made one very useful in dangerous and difficult situations. And great to poke fun at.
A few “Best of Spock” moments
While Leonard Nimoy’s name will forever tumble about the asteroid belt, his fictional character got there before him. Or did it? 2309 Mr. Spock (former 1971 QX1) was discovered by James Gibson on August 16, 1971. An outer main belt asteroid about 13 miles (21 km) across and orbiting the Sun every 5.23 years, it’s actually not named for the Star Trek character. Nope. Gibson named it for his cat.
The sky facing southeast around 2 a.m. in early June. Leonard Nimoy’s asteroid is currently in Capricornus where it borders with Sagittarius. Source: Stellarium
The act prompted the International Astronomical Union (IAU) in 1985 to ban the use of pet names for asteroids. Aw, come on IAU, where’s your sense of humor? Then again, Nimoy’s Spock might have considered the new rule quite logical.
Various meteorites from 2008 TC3.
Credit: P. Jenniskens, et. al. Click image for full description
Asteroids, meteors, and meteorites … It might be fair to say these rocks from space inspire both wonder and fear among us Earthlings. But knowing a bit more about each of them and how they differ may eliminate some potential misgivings. While all these rocks originate from space, they have different names depending their location — i.e. whether they are hurtling through space or hurtling through the atmosphere and impacting Earth’s surface.
In simplest terms here are the definitions:
Asteroid: a large rocky body in space, in orbit around the Sun.
Meteoroid: much smaller rocks or particles in orbit around the Sun.
Meteor: If a meteoroid enters the Earth’s atmosphere and vaporizes, it becomes a meteor, which is often called a shooting star.
Meteorite: If a small asteroid or large meteoroid survives its fiery passage through the Earth’s atmosphere and lands on Earth’s surface, it is then called a meteorite.
Another related term is bolide, which is a very bright meteor that often explodes in the atmosphere. This can also be called a fireball.
Let’s look at each in more detail:
Asteroids An artists impression of an asteroid belt. Credit: NASA
Asteroids are found mainly in the asteroid belt, between Mars and Jupiter. Sometimes their orbits get perturbed or altered and some asteroids end up coming closer to the Sun, and therefore closer to Earth. In addition to the asteroid belt, however, there have been recent discussions among astronomers about the potential existence of large number asteroids in the Kuiper Belt and Oort Cloud. You can read a paper about this concept here, and a good article discussing the topic here.
The asteroid Vesta as seen by the Dawn spacecraft. Credit: NASA/JPL-Caltech/UCAL/MPS/DLR/IDA
Asteroids are sometimes referred to as minor planets or planetoids, but in general, they are rocky bodies that do not have an atmosphere. However, a few have their own moons. Our Solar System contains millions of asteroids, many of which are thought to be the shattered remnants of planetesimals – bodies within the young Sun’s solar nebula that never grew large enough to become planets.
The size of what classifies as an asteroid is not extremely well defined, as an asteroid can range from a few meters wide – like a boulder — to objects that are hundreds of kilometers in diameter. The largest asteroid is asteroid Ceres at about 952 km (592 miles) in diameter, and Ceres is so large that it is also categorized as a dwarf planet.
Most asteroids are made of rock, but as we explore and learn more about them we know that some are composed of metal, mostly nickel and iron. According to NASA, a small portion of the asteroid population may be burned-out comets whose ices have evaporated away and been blown off into space. Recently, astronomers have discovered some asteroids that mimic comets in that gas and dust are emanating from them, and as we mentioned earlier, there appears to be a large number of bodies with asteroid-like compositions but comet-like orbits.
How Often Do Asteroids Hit Earth?
Meteor Crater near Winslow, Arizona. Image credit: NASA.
While we know that some asteroids pass very close to Earth’s orbit around the Sun, we’ve been lucky in the history of humanity that we haven’t had a large asteroid hit Earth in the past several thousand years. It wasn’t until satellite imagery of Earth became widely available that scientists were able to see evidence of past asteroid impacts.
One of the more famous impact craters on Earth is Meteor Crater in Arizona in the US, which was made by an impact about 50,000 years ago. But there are about 175 known impact around the world – a few are quite large, like Vredefort Crater in South Africa which has an estimated radius of 190 kilometers (118 miles), making it the world’s largest known impact structure on Earth. Another notable impact site is off the coast of the Yucatan Peninsula in Mexico, and is believed to be a record of the event that led to the extinction of the dinosaurs 65 million years ago. You can see images of some of the most impressive Earth impact craters here.
These days, asteroid impacts are less of a threat. NASA estimates that about once a year an automobile-sized asteroid enters Earth’s atmosphere, creates an impressive fireball and disintegrates before ever reaching the surface. Studies of Earth’s history indicate that about once every 5,000 years or so on average an object the size of a football field hits Earth and causes significant damage. Once every few million years on average an object large enough to cause regional or global disaster impacts Earth. You can find more information about the frequency of impacts in this article from NASA.
Meteors, Meteoroids and Bolides
A bright meteor from September 21, 1994. Credit: John Chumack.
Space debris smaller than an asteroid are called meteoroids. A meteoroid is a piece of interplanetary matter that is smaller than an asteroid and frequently are only millimeters in size. Most meteoroids that enter the Earth’s atmosphere are so small that they vaporize completely and never reach the planet’s surface. When they burn up during their descent, they create a beautiful trail of light known as a meteor, sometimes called a shooting star.
Mostly these are harmless, but larger meteors that explode in the atmosphere – sometimes called bolides — can create shockwaves, which can cause problems. In February 2013 a meteor that exploded over Chelyabinsk, Russia shattered windows with its air blast. This meteoroid or bolide was estimated to be 18 meters (59 feet) in diameter. In 1908, a rocky meteoroid less than 100 meters in diameter is believed to have entered the atmosphere over the Tunguska region of Siberia in 1908 and the resulting shockwave knocked down trees for hundreds of square kilometers
How often is Earth hit by meteroids?
Chelyabinsk fireball recorded by a dashcam from Kamensk-Uralsky north of Chelyabinsk where it was still dawn.
Because of the Chelyabinsk meteor in 2013, astronomers have acquired more information about the frequency of larger meteors that hit Earth, and there is now a growing consensus that the Earth gets hit by bigger space rocks more often than we previously thought. You can read more about that concept here.
This video from the B612 Foundation shows a visualization of the location of 26 space rocks that hit Earth between 2000 and 2013, each releasing energy equivalent to some of our most powerful nuclear weapons. The B612 foundation says that a Hiroshima-scale asteroid explosion happens in our atmosphere on average once a year, but many are not detected because they explode high in the atmosphere, or because most of the Earth’s surface is water and even a large percentage of land is fairly uninhabited by humans.
Estimates vary of how much cosmic dust and meteors enter Earth’s atmosphere each day, but range anywhere from 5 to 300 metric tons. Satellite observations suggest that 100-300 metric tons of cosmic dust enter the atmosphere each day. This figure comes from the rate of accumulation in polar ice cores and deep-sea sediments of rare elements linked to cosmic dust, such as iridium and osmium.
But other measurements – which includes meteor radar observations, laser observations and measurements by high altitude aircraft — indicate that the input could be as low as 5 metric ton per day. Read more about this here.
For a documented list of bolide events, you can check out this page from JPL.
Meteorite A stunning slice of the Glorieta pallasite meteorite cut thin enough to allow light to shine through its many olivine crystals. Credit: Mike Miller
If any part of a meteoroid survives the fall through the atmosphere and lands on Earth, it is called a meteorite. Although the vast majority of meteorites are very small, their size can range from about a fraction of a gram (the size of a pebble) to 100 kilograms (220 lbs) or more (the size of a huge, life-destroying boulder). Meteorites smaller than 2mm are classified as micrometeorites.
Meteorites have traditionally been divided into three broad categories, depending on their structure, chemical and isotopic composition and mineralogy. Stony meteorites are rocks, mainly composed of silicate minerals; iron meteorites that are largely composed of metallic iron-nickel; and, stony-iron meteorites that contain large amounts of both metallic and rocky material.
Meteorites have also been found on the Moon and Mars and conversely, scientists have traced the origination of the meteorites found here on Earth to four other bodies: the Moon, Mars, the asteroid 4 Vesta, and the comet Wild 2. Meteorites are the source of a great deal of the knowledge that we have have about the composition of other celestial bodies.
How Often Do Meteorites Hit 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)
According to the Planetary Science Institute, it is estimated that probably 500 meteorites reach the surface of the Earth each year, but less than 10 are recovered. This is because most fall into water (oceans, seas or lakes) or land in remote areas of the Earth that are not accessible, or are just not seen to fall.
In short, the difference between asteroids and meteors all comes down to a question of location. Asteroids are always found in space. Once it enters an atmosphere, it becomes a meteor, and then a meteorite after it hits the ground. Each are made of the same basic materials – minerals and rock – and each originated in space. The main difference is where they are when they are being observed.
