Asteroids are rocky objects in space that can be hundreds of miles wide, or just a few feet across. Most of them in our solar system are in orbit between Mars and Jupiter. The Trojan asteroids are in two clusters, in front of and behind Jupiter. In the next photo, see an image captured by an unmanned probe launched in 1996.
Image Credit: Lunar and Planetary Institute
Near Earth Asteroid Rendezvous Shoemaker, an unmanned probe, launched in 1996, was the first spacecraft to land on an asteroid. Before it did, it captured these images of its target, Eros. Next up, see an unusual trail of debris.
Image Credit: NASA/Goddard Space Flight Center Scientific Visualization Studio
In 2010, the Hubble Space Telescope captured this unusual X-shaped trail of debris 90 million miles from the Earth. Researchers thought it could have resulted from a collision between two asteroids. Do you know what an impact crater looks like?
Image Credit: NASA/ESA/D. Jewitt (UCLA)
The Aorounga impact crater is about 10.5 miles (17 kilometers) wide, and was caused by an asteroid hundreds of millions of years ago. Next up, see an asteroid captured by the Jupiter-bound probe Galileo.
Image Credit: NASA/JPL-Caltech
The asteroid Ida was discovered in 1884. More than a century later, NASA scientist Ann Harch analyzed data returned by the Jupiter-bound probe Galileo and discovered Dactyl -- the first observed moon of an asteroid. In the next photo, see an amazing image taken by the NASA spacecraft Stardust.
Image Credit: NASA/JPL
These images are from NASA spacecraft Stardust. Launched in 1999, it had encounters with asteroid Annefrank and comets Wild 2 and Tempel 1. Samples from Wild 2 the craft sent back contained the organic chemical glycerin. Have you ever seen a space shuttle liftoff?
Image Credit: NASA/JPL-Caltech/University of Maryland/Cornell
In 2007, NASA sent the Dawn spacecraft on a 1.7 billion-mile journey to asteroids Ceres and Vesta. Dwarf planet Ceres, the first known asteroid, was discovered by Italian priest and astronomer Giuseppe Piazzi in 1801.
Image Credit: NASA/Sandra Joseph and Rafael Hernandez
An artist's conception of Dawn en route to the asteroid Vesta, shown at left, and another asteroid, the dwarf planet Ceres, at right. Scientists hope the mission will help us understand the formation of the solar system. Do you know what an asteroid fragment looks like up close?
Image Credit: NASA/JPL-Caltech
A 1.4 pound (.631 kg) piece of Vesta that fell into western Australia as an asteroid in 1960. It consists almost entirely of pyroxene, a mineral component of lava flows on Earth. Mars, the moon and Vesta are the only extraterrestrial bodies scientists have samples of. In the next photo, see how NASA began mapping the universe.
Image Credit: NASA/R. Kempton (New England Meteoritical Services)
In January 2010, NASA's Wide-Field Infrared Survey Explorer (WISE) began mapping the universe in unprecedented detail. The red dot is the first asteroid it discovered, 2010 AB78, is about 0.6 miles (1 km) in diameter and 98 million miles (158 million km) from Earth.
Image Credit: NASA/JPL-Caltech/UCLA
This diagram shows a top-down view of our asteroid belt, which lies between the orbits of Mars (the red orbit ring) and Jupiter (the purple orbit ring). During its mapping travels, the WISE will see hundreds of thousands of asteroids that have diameters wider than 1.9 miles (3 kilometers). See all of those green dots? They represent populations of asteroids, and the yellow dots illustrate the asteroid populations WISE is expected to see. You'd be forgiven for seeing all of that traffic and wondering, "which of these are close to Earth?" Populations of so-called "near-Earth objects" -- comets and asteroids with orbits that pass relatively close to Earth's path around the sun (the blue orbit ring here) -- are shown in red. (It would be nice if there were fewer red dots, wouldn't it?) NASA expects WISE to detect about 1,000 near-Earth asteroids.
Image Credit: NASA/JPL-Caltech
NASA's Spitzer space telescope, during its travels, observed the dusty remnants of shredded asteroids around several dead stars. Here we see an artist's concept that illustrates one such dead star (or "white dwarf"), surrounded by the hurtling shards of a disintegrating asteroid. Such observations by the Spitzer give astronomers a better idea about the composition of rocky planets that orbit other stars.
Image Credit: NASA/JPL-Caltech
Potato, anyone? Or how about an asteroid? This image was captured by NASA's Near Earth Asteroid Rendezvous mission in 2000. It's a close-up of Eros, one of the near-Earth asteroids we mentioned a couple of images ago. It has an orbit that brings it somewhat close to our home turf, although not close enough that anyone is sounding the alarm. It's just one of many other near-Earth asteroids the Spitzer space telescope has observed.
Image Credit: NASA/JHUAPL
Against the stunning backdrop of a spiral galaxy, we see an asteroid tearing through space. It's the bright-red object in the lower-right area of the picture. The asteroid's name is 3540 Protesilaos, and this mosaic image shows the asteroid at different points in its orbit around the sun. The Wide-Field Infrared Survey Explorer observed it 10 times, though only some of the frames it shot were used in this image. The galaxy behind the asteroid is Messier 74, whose multiple spiral arms can plainly be seen.
Image Credit: NASA/JPL-Caltech/UCLA
This artist's concept illustrates the first known Earth Trojan asteroid. It was discovered by NEOWISE, the asteroid-hunting (Near-Earth Object) portion of NASA's WISE mission. The asteroid is depicted in gray and its orbit around the sun is shown in green. Earth's orbit around the sun is marked by the blue dots. (Note that the objects are not drawn to scale.) Trojans are asteroids that share an orbit with a planet, circling around the sun in front of or behind it. The asteroids never cross the paths of or collide with the planets, because they -- planet and asteroid -- are in the same orbit. The asteroid in this illustration, 2010 TK7, has an extreme orbit that takes it far above and below the plane of Earth's orbit. The most welcome news is that, at least for the next 100 years, NASA says 2010 TK7 won't come anywhere near us. That is, if you agree that 15 million miles (24 million kilometers) isn't considered "near."
Image Credit: Paul Wiegert, University of Western Ontario, Canada
This artist's illustration shows a huge asteroid belt orbiting a star that's about the same age and size as our sun. The belt surrounds a nearby star called HD 69830, shining away about 41 light years out, in the constellation Puppis. The Spitzer space telescope first encountered evidence for this potential asteroid belt when it observed warm dust around the star. The dust is presumed to be from asteroids smashing together. The belt depicted here is is larger than our own solar system's asteroid belt. It's also closer to its star: It lies just inside an orbit equivalent to that of Venus.
Image Credit: NASA/JPL-Caltech/T. Pyle (SSC)
The Dawn spacecraft brings us this picture of bright material extending from the Canuleia crater, on the surface of the craft's target of study: the asteroid Vesta. The material appears to have been thrown out of the crater during the impact that created it. Canuleia crater is about 6 miles (10 kilometers) in diameter, and the bright material is cast off 12 to 19 miles (20 to 30 kilometers) beyond the crater's rim. That must have been some impact! This shot, taken during high-altitude mapping orbit, covers about 2,000 square miles (5,000 square kilometers). Vesta smiles for the camera in our next picture too.
Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/UMD
NASA's Hubble space telescope took these pictures of Vesta while it prepared for the Dawn spacecraft's visit to the neighborhood. Each image captures a view of Vesta during its 5.34-hour rotation period. Vesta was 131 million miles (211 million kilometers) from Earth when it posed for these shots from the Hubble. The images underscore the difference in brightness and color on the asteroid's surface. As we've seen, Dawn, of course, would go on to get sharp, close-up images of the asteroid.
Image Credit: NASA/ESA/STScI/UMd
Now we get to see how the asteroid Vesta stacks up against other asteroids out there in the cosmos. This composite image compares seven asteroids with Vesta. shows the comparative sizes of eight asteroids. Until recently, Lutetia (upper right), with a diameter of 81 miles (130 kilometers), was the largest asteroid visited by a spacecraft. But Lutetia would be punching way out of its class to take on Vesta, which is also considered a protoplanet because it's a large body that almost became a planet. As it's plain to see, Vesta simply dwarfs all other small bodies in this image, with its diameter at about 330 miles (530 kilometers). Next we'll look at Vesta's "snowman."
Image Credit: NASA/JPL-Caltech/JAXA/ESA
This image is a mosaic from the Dawn spacecraft. It features dark material (see arrows) near a series of craters on Vesta that are known collectively by NASA as the "snowman.". The dark, ejected material is a mixture of components that probably includes not only dark material thrown out from the craters during the impacts that created them but also an even darker melt that occurred during the impact. Luckily for this snowman, the melt presents no danger to it. We'll get another nice close-up of Vesta in the next picture.
Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA/ASU
The Dawn spacecraft took this picture of the enormous asteroid Vesta on July 24, 2011. Next up, we'll visit an alien planet.
Image Credit: NASA
This illustration shows an artist's rendition of what the night sky might look like from a hypothetical alien planet, in a star system that has an asteroid belt that's 25 times more massive than the one in our own solar system. It's not just a fanciful notion either: The Spitzer space telescope found evidence for just such a belt around a nearby star called HD 69830. The telescope's sharp, infrared eyes spotted dust, presumably from asteroids banging together. While the telescope did not find direct evidence for a planet in the asteroid-belted system, astronomers theorize that one or more may be present. In our solar system, if you check out the sky on a moonless night, as far away as possible from city lights, you can see the sunlight that is scattered by dust in our asteroid belt appearing as a dim band stretching up from the horizon when the sun is about to rise or set. Such light in the HD 69830 star system would be 1,000 times brighter than our own, brighter even than the Milky Way.
Image Credit: NASA/JPL-Caltech
We've talked a lot about Vesta in our gallery, but another asteroid on NASA's radar has been Ceres. It's the largest asteroid we know about, at 590 miles in diameter (950 kilometers), and it may in fact be a "mini-planet" containing pure water ice underneath its surface. The Hubble space telescope shows that Ceres has some of the same characteristics as rocky, terrestrial planets like Earth. Too, its shape is almost round, like Earth's. This suggests to scientists that the asteroid may have a rocky inner core and a thin, dusty outer crust.
Image Credit: NASA, ESA, J.-Y. Li (University of Maryland) and G. Bacon (STScI)
We'll leave Ceres now and return to Vesta, to see the giant asteroid's south pole, which has cliffs that are several miles or kilometers high, deep grooves and craters. Astronomers for the Dawn mission aren't sure yet just how such unusual features formed. One theory is that collisions with other asteroids may have been responsible for such cliffs, as might have any internal processes that occurred during the asteroid's early phases.
Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Here's a rather eerie radar image of asteroid 2005 YU55. It was doing an Earth flyby of sorts when the picture was taken. At the time it smiled for this photo, it was about 860,000 miles (1.38 million kilometers) from Earth. Not so very far away, at least in galactic terms.
Image Credit: NASA/JPL-Caltech
This infrared image from NASA's Wide-field Infrared Survey Explorer -- or WISE, as we have noted elsewhere -- happened to catch an asteroid in our solar system passing by. You can see it streaking leftward in the lower part of the image. The asteroid is known as 1719 Jens. It's passing in front of the Tadpole Nebula, a star factory about 12,000 light years away.
Image Credit: NASA/JPL-Caltech/UCLA
NASA's Dawn is up to its observant ways again in this image of Vesta. Dawn took this 3-D view from an orbit of about 1,700 miles (2,700 kilometers) above the surface of the asteroid. We can see the many impact craters that serve as reminders that this big chunk of rock had a tough childhood. This 3-D picture provides scientists with the chance to better understand the structure of craters on asteroids as well as the properties of the material on Vesta's surface.
Image Credit: NASA/JPL-Caltech/UCLA/MPS/DLR/IDA
Near the beginning of our gallery, we took a look at the asteroid Eros. Here's an even closer look at the asteroid, from a September 2000 shot taken by NEAR Shoemaker. The broad, curved depression that stretches vertically across the picture is a part of the asteroid that was steeped too thoroughly in shadow for a good picture, during an earlier orbital pass, but on this occasion the NEAR Shoemaker probe got the area it wanted. Next we'll look at a system that has double the asteroid fun!
Image Credit: NASA
This artist's conception shows Epsilon Eridani, just 10 light years away, the closest known planetary system to our own. It's so close in fact that it can be seen with he naked eye in the night skies. The Spitzer space telescope has been able to reveal that the system has two asteroid belts. The inner belt appears here as the yellowish ring around the star, and the outer asteroid belt is seen in the foreground.
Image Credit: NASA/JPL-Caltech
We'll finish our gallery with a chilling reminder that asteroids, while often rather lumpy-, distant- and hazy-looking, can strike without warning and really pack a wallop. Even here! (Just ask the dinosaurs, whose extinction may well have come from the business end -- well, if it had one -- of an inbound asteroid.) Here we see an object that, catching scientists off guard thanks to its size, slammed into Jupiter on July 19, 2009, leaving a dark bruise the size of our Pacific Ocean (marked in the image with a square). The spot was first observed by an amateur astronomer in Australia, and soon enough observatories worldwide, including the Hubble telescope, were zooming in on Jupiter's new bruise. It's theorized a rogue asteroid was the cause of the mayhem.
Image Credit: NASA, ESA, M. Wong, H. Hammel, I. de Pater, and the Jupiter Impact Team
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