Category Archives: Comets and Asteroids
Comets are the icy remnants left over from the formation of the Solar System. They circle the Sun in highly elliptical orbits that can range in length from several years to several million years, depending on their origin, and while they are usually quiet and dark when they get close enough to the Sun they are briefly heated enough to melt—technically sublimate—some of their frozen material, forming a cloud of gas and dust and a long tail sometimes big and bright enough to be visible from Earth.
But for the majority of their travels most comets are dark and difficult to spot, especially those originating from the Oort Cloud, an enormous spherical zone of icy debris surrounding our Solar System 186 billion miles away. Now, using infrared data from NASA’s WISE spacecraft, researchers have concluded that there are many more so-called “long period” comets visiting from the Oort Cloud than previously suspected—at least seven times more—and that they’re larger than we thought, too…many over half a mile across.
This is our best look yet at asteroid 2014 JO25, which made its closest pass by Earth for at least the next 500 years on April 19, 2017. The animation above is composed of radar observations made from NASA’s Goldstone facility in California when the asteroid was between 1.53 and 1.61 million miles away. These and earlier, lower-resolution images obtained the previous day (you can see those here) showed this asteroid to be a contact binary—two objects connected by a “neck” of material, not unlike the comet 67P that ESA’s Rosetta mission explored. The largest section of JO25 is estimated to be 2,000 feet (610 meters) wide, and at its widest the entire asteroid is about 3,300 feet (1 km) across. Observations also show JO25 rotates once every 4.5 hours.
SPACE NEWS FLASH: On Wednesday, April 19, the asteroid 2014 JO25 will pass by Earth, coming as close as about 1.1 million miles at 12:24 UTC (8:24 a.m. EDT / 5:24 a.m. PDT). Yes, this asteroid is fairly large—just under half a mile across—and is traveling very fast—about 21 miles a second— BUT even so it poses no danger to Earth as 1.1 million miles is still over four and a half times the distance to the Moon…and it’s simply not going to get any closer than that.
It’s. Just. Not.
Remember when I mentioned that NASA’s OSIRIS-REx spacecraft was going to be scanning for “Trojan” asteroids at Earth-Sun L4? Well the results are in and survey says: no new Trojans (besides 2010 TK7, which we already knew about.) But the search wasn’t in vain—it gave mission scientists a chance put the spacecraft’s OCAMS instruments to the test and they passed with flying colors.
In fact the MapCam camera did so well it was able to image 17 main belt asteroids from L4, some two full magnitudes dimmer than expected.
“The Earth-Trojan Asteroid Search was a significant success for the OSIRIS-REx mission,” said OSIRIS-REx principal investigator Dante Lauretta of the University of Arizona, Tucson. “In this first practical exercise of the mission’s science operations, the mission team learned so much about this spacecraft’s capabilities and flight operations that we are now ahead of the game for when we get to Bennu.”
Read the full story on the OSIRIS-REx site here: OSIRIS-REx Asteroid Search Tests Instruments, Science Team
See that big rock there? (It’s easy because there’s a big yellow arrow pointing to it.) That’s a 100-foot/30-meter wide boulder that was imaged sitting on the surface of Comet 67P/Churyumov-Gerasimenko by ESA’s Rosetta on May 2, 2015. Nine months later Rosetta captured another image of the same area in which that huge stone had clearly moved—find out below just how far!