But if you think that's too close for comfort, how about an asteroid passing within just 140,000 miles (only 60% of the distance between the Earth and moon) of our planet? Guess what?… already happened earlier this morning.
Discovered only two days ago, XE54 came about as close to crashing into Earth as an asteroid can without actually doing so - close enough to be "eclipsed by Earth's shadow, causing its shadow to 'wink out' for a short time," according to Universe Today.
With a diameter of just 72-160 feet, XE54 is a far cry from the over six-mile wide asteroid that wiped out dinosaurs (and about 50% of all life's species) 65 million years ago. But, while it's possible an asteroid of this size would produce nothing more than a brilliant fireball as it disintegrated after entering the atmosphere, a direct hit by remaining rock chunks on a populated region could be disastrous.
Believe it or not, a surprise near miss of this sort is not especially unusual. In June 2011, an steroid estimated about 30 feet in size ("2011 MD") passed by Earth and missed a direct hit by only 7,500 miles. An even closer encounter occurred earlier in 2011 when another small asteroid missed Earth by just 3,400 miles.
NASA's Voyager 1 spacecraft has discovered a new layer of the solar system that scientists hadn't known was there, researchers announced today (Dec. 3).
Voyager 1 and its sister probe Voyager 2 have been traveling through space since 1977, and are close to becoming the first manmade objects to leave the solar system.
Scientists haven't been sure exactly when that exit would occur, and now say the spacecraft are likely in the outermost region of the solar system, which is defined by the extent of the heliosphere, the large bubble of charged particles the sun puffs out around itself. Voyager 1, in particular, has entered a new region of the heliosphere that scientists are calling a "magnetic highway," which allows charged particles from inside the heliosphere to flow outward, and particles from the galaxy outside to come in.
An unmanned flyby mission to Pluto's Charon, sample return missions to Jupiter's moon Europa or Saturn's Titan, or a sample-gathering flight through Jupiter's atmosphere or the ice water jets of Saturn's Enceladus — all are said to be possible with the 286,000-pound (130,000 kilograms) launch capabilities of the Space Launch System.
Such large cargos will be transported under a nose-cone fairing that will have a diameter of about 30 feet (10 meters), giving the Space Launch System a useful payload volume of about 38,846 cubic feet (1,100 cubic meters). The rocket itself has a diameter of about 25 feet (8.4 meters).
Voyager 1 is the most distant man-made object and is thought to have recently escaped the sun's sphere of influence. The probe, launched 35 years ago, is therefore mankind's first interstellar vehicle careening into the vast expanse of space between the stars.
Needless to say, as one of two deep space probes launched in 1977, Voyager 1 has explored previously unknown regions of the solar system, making groundbreaking discoveries as it went. Now, in a new paper published in the Journal of Geophysical Research, scientists analyzing data streaming from the spacecraft have uncovered a small mystery right at the solar system's magnetic boundary with the interstellar medium.
As the sun travels through the galaxy, it carries its magnetic field with it, creating a magnetic "bubble" — the heliosphere — that all planets, spacecraft and people live inside. Until recently, Voyager 1 (and her sister probe Voyager 2) have also existed completely inside the sun's environment. Both probes could detect the high energy particles streaming from the sun and they 'felt' the solar magnetic field. At time of writing, Voyager 1 is nearly 122 AU from the sun (over three times the average Pluto-sun distance) and it takes over 17 hours for a signal to travel from the probe to Earth.
So, in an effort to detect when the Voyager probes might exit the heliosphere, scientists have kept a watchful eye on two key pieces of data — particle energy counts and magnetic field strength (and orientation).
n 2004, scientists realized that Voyager 1 had traveled through the "termination shock" — a region where the solar wind begins to interact with the interstellar medium. Then, in 2010, the probe crossed into a stagnation region just beyond the termination shock known as the "heliosheath" — this is where the solar wind slows to zero and the magnetic field becomes compressed and begins to fluctuate.
The capsule was sent by the California-based company SpaceX, the first of 12 missions it will perform for US space agency Nasa.
It landed in the Pacific Ocean west of Mexico at 12:22 local time (19:22 GMT).
The robotic Dragon ship lifted off on 7 October, with 400kg of food, clothing, experiments and spares for the orbiting platform's six astronauts, and docked three days later.
On its return, the capsule carried broken machinery and medical samples gathered by the astronauts aboard the ISS over the course of the past year.
SpaceX's next mission is expected in January, although the company will need to satisfy Nasa before then that the cause of an engine anomaly experienced by Dragon's launch rocket during its 7 October ascent has been understood, and that corrective action has been taken.