NASA Image of the Day for October 9th

Vesta Sizes Up

 

This composite image shows the comparative sizes of nine asteroids. Up until now, Lutetia, with a diameter of 81 miles (130 kilometers), was the largest asteroid visited by a spacecraft, which occurred during a flyby. Vesta dwarfs all other small bodies in this image.

Asteroid Vesta also is considered a protoplanet because it’s a large body that almost became a planet and has a diameter of approximately 330 miles (530 kilometers). was the largest asteroid visited by a spacecraft, which occurred during a flyby. Vesta dwarfs all other small bodies in this image.

Asteroid Vesta also is considered a protoplanet because it’s a large body that almost became a planet and has a diameter of approximately 330 miles (530 kilometers).

Image Credit: NASA/JPL-Caltech/JAXA/ESA

Astronomy Picture of the Day For October 1st

Astronomy Picture of the Day

Discover the cosmos!Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2011 October 1

Asteroids Near Earth
Illustration Credit: NASA, JPL-Caltech, WISE 

Explanation: Though the sizes are not to scale, the Sun and planets of the inner solar system are shown in this illustration, where each red dot represents an asteroid. New results from NEOWISE, the infrared asteroid hunting portion of the WISE mission, are shown on the left compared to old population projections of mid-size or larger near-Earth asteroids from surveys at visible wavelengths. And the good news is, NEOWISE observations estimate there are 40 percent fewer near-Earth asteroids that are larger than 100 meters (330 feet), than indicated by visible light searches. Based on infrared imaging, the NEOWISE results are more accurate as well. Heated by the Sun, asteroids of the same size radiate the same amount of infrared light, but can reflect very different amounts of visible sunlight depending on how shiny their surface is, or their surface albedo. That effect can bias surveys based on optical observations. NEOWISE results reduce the estimated number of mid-size near-Earth asteroids from about 35,000 to 19,500, but the majority still remain undiscovered.

Astronomy Picture of the Day for Sept. 19th

Astronomy Picture of the Day

Discover the cosmos!Each day a different image or photograph of our fascinating universe is featured, along with a brief explanation written by a professional astronomer.

2011 September 19

The South Pole of Asteroid Vesta
Image Credit: NASA, JPL-Caltech, UCLA, MPS, DLR, IDA 

 

Explanation: What created the circular structure around the south pole of asteroid Vesta? Pictured above, the bottom of the second largest object in the asteroid belt was recently imaged for the first time by the robotic Dawn satellite that arrived last month. A close inspection of the 260-meter resolution image shows not only hills and craters and cliffs and more craters, but ragged circular features that cover most of the lower right of the 500-kilometer sized object. Early speculation posits that the structure might have been created by a collision and coalescence with a smaller asteroid. Alternatively, the features might have originated in an internal process soon after the asteroid formed. New clues might come in the next few months as Dawn spirals down toward the rocky world and obtains images of increasingly high resolution.