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Although sunlight is more intense on Saturday, winter in the Northern Hemisphere is unaffected, due to the 23.5-degree tilt of Earth's axis. Being closer to the sun does not change the Earth's tilt, so the North Pole is still tilted away from the sun. Six months from now, on July 5, Earth will be at its farthest from the sun, known as its aphelion, meaning "far from the sun." At perihelion, Earth is about 91.5 million miles from the sun, and at aphelion, it is around 94.5 million miles away. Between perihelion and aphelion, there is about a 6.7% difference...

Normal Axis tilt 23.5 degrees Current Axis Tilt & new Tropic lines

A similar process is playing out with the probe's speed: At the peak of its first two perihelions, the spacecraft traveled at about 213,200 mph (343,000 km/h), also breaking records, but future close approaches will see the Parker Solar Probe moving still faster. These close grazes are anxious times for scientists and engineers on the mission because the spacecraft is out of communication with Earth for several days before and after each perihelion. The radio silence is designed to let the spacecraft focus on keeping its instruments tucked safely behind the thick shield that protects them from the incredible heat...

In a sequence of images taken by Rosetta’s scientific camera OSIRIS, the brilliant, well-defined jet erupts from the side of the comet’s neck in the Anuket region. It was first seen in a photo taken at 8:24 a.m. CDT, but not in one taken 18 minutes earlier, and had faded significantly in an image captured 18 minutes later. The camera team estimates the material in the jet was traveling at a minimum of 22 mph (10 meters/sec), but possibly much faster. It’s the brightest jet ever seen by Rosetta. Normally, the camera has to be set to overexpose 67P/C-G’s nucleus...

Currently, ISON sits about a magnitude below the projected light curve, (see below) but that isn’t all that unusual for a comet. Already, there’s been increasing talk of “ISON being a dud,” but as Universe Today’s Nancy Atkinson pointed out in a recent post, these assertions are still premature. The big question is what ISON will do leading up to perihelion, and if it will survive its passage 1.1 million kilometres above the surface of the Sun on November 28th to become a fine comet in the dawn skies in the weeks leading up to Christmas. Of course, there’s much...

[The following is an exact transcript of this podcast.] Happy New Year! And don’t feel bad about taking today off. After all, you’ve traveled far. And I’m not talking about the trip home from the party last night. According to NASA, just by being on the planet Earth in the last year, you’ve zipped about 584 million miles around the sun to get back where you were. At an average speed of about 67,000 miles per hour. Again, not talking about the drive home last night. Of course, the trip was not a perfect circle. As Kepler showed, the Earth’s...

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. 2003 January 30 Comet Kudo-Fujikawa: Days in the Sun Credit: SOHO - LASCO Consortium, ESA, NASA Explanation: Cruising through the inner Solar System, new Comet Kudo-Fujikawa reached perihelion, its closest approach to the Sun, yesterday, January 29. Passing within 28.4 million kilometers of the Sun, this comet came much closer than innermost planet Mercury basking only 57.9 million kilometers from our parent star. So close to the Sun,...