After a brief lull, solar activity is back in full swing. The largest sunspot groups look like showy parade floats wheeling across the sun’s northern hemisphere. The three largest spots are approximately the size of the planet Jupiter. Using a safe solar filter this morning, I saw Groups 1260 and 1263 with the naked eye. Even more exciting, Group 1260 has a ‘delta class’ magnetic field, where dark sunspot cores called umbrae of different magnetic polarities are closely packed together inside the larger penumbrae. In the photo above, the umbrae are the dark dots surrounded by the paler penumbrae.
Like a bunch of Democrats and Republicans squeezed into a small room, the atmosphere in a delta configuration can get testy. The jumble of north and south magnetic fields in close proximity can lead to sudden connections between them, releasing vast amounts of energy in the form of X-class solar flares. X- flares can damage sensitive satellite electronics, cause radio blackouts and initiate spectacular displays of northern and southern lights.
If you have a scope with a safe filter, have a look at the home star in the coming days. Sunspots are very dynamic. Groups can change shape, number and extent day by day as they move westward with the sun’s rotation.
In case you haven’t heard the news, Earth’s got a new little buddy named 2010 TK7, a 1,000 foot long Trojan asteroid orbiting in a stable region called the L4 Lagrangian point just ahead of our planet. Trojans are asteroids that share an orbit with a planet at two stable points 60 degrees ahead and 60 degrees behind it. These areas are where the sun and the planet’s gravity balance out neatly, allowing small objects like asteroids to remain there relatively undisturbed.
Trojans are named for characters in Homer’s epic The Iliad and The Odyssey, thus we have Achilles, Icarion and Hektor, three of the many hundreds of thousands of Trojans orbiting in giant Jupiter’s stable zones.
2010 TK7 is the very first Earth Trojan. It was discovered by the Wide-Field Infrared Survey Explorer (WISE) during its grand survey of the entire sky in infrared light. Astronomers using WISE have observed 155,000 asteroids in the main
belt between Mars and Jupiter, and more than 500 near-Earth asteroids and discovered
132 that were previously unknown.
This animation illustrates the orbit of 2010 TK7 as it performs a large looping motion around the stable Lagrangian point ahead of Earth.
Earth Trojans are difficult to find, because they lie in the same direction as the sun in the daytime sky. But 2010 TK7 orbits around the L4 stable point well above and below Earth’s orbit, so it appears farther from the sun than a routine Trojan, making it an easier catch. It’s located a nominal 50 million miles from our planet, but its unusual looping orbit means its distance from us varies over time. Not to worry. The asteroid’s orbit is well-defined and for at least the next 100 years, it won’t come closer to Earth than 12.4 million miles.
Besides Jupiter’s hoard of Trojans, Mars has four and Neptune eight. Watch the video and you’ll see how the newly-discovered asteroid precedes Earth in its orbit. Our two worlds perform an orbital ballet for all to marvel. You can read more about 2010 TK7 HERE.
One last news note. The Dawn space probe has returned a new closeup photo of the asteroid Vesta. Science operations and detailed mapping should begin in early August. Scientists are hoping to learn the origin of its totally ‘groovy’ surface.