Van 5 tot 6 Juni 2012 zullen miljoenen mensen in de gelegenheid zijn om Venus voor de Zon te zien voorbijgaan. Venus doet daar ongeveer 6 uur over en zal te zien zijn als een kleine zwarte punt op het oppervlakte van de Zon. De volgende maal dat dit te zien is is in het jaar 2117
When a moderate-sized M-class flare erupted from the Sun on May 17, it sent out a barrage of high-energy solar particles that belied its initial intensity. These particles traveled at nearly the speed of light, crossing the 93 million miles between the Sun and Earth in a mere 20 minutes and impacting our atmosphere, causing cascades of neutrons to reach the ground — a rare event known as a ground level enhancement, or GLE.
The first such event since 2006, the GLE was recorded by a joint Russian/Italian spacecraft called PAMELA and is an indicator that the peak of solar maximum is on the way.
The PAMELA spacecraft — which stands for Payload for Antimatter-Matter Exploration and Light-nuclei Astrophysics — is designed to detect high-energy cosmic rays streaming in from intergalactic space. But on May 17, scientists from NASA’s Goddard Space Flight Center convinced the Russian team in charge of PAMELA to grab data from the solar event occurring much closer to home.
This graph shows the neutrons detected by a neutron detector at the University of Oulu in Finland from May 16 through May 18, 2012. (University of Oulu/NASA's Integrated Space Weather Analysis System)
The result: the first observations from space of the solar particles that trigger the neutron storms that make up a GLE. Scientists hope to use the data to learn more about how GLEs are created, and why the May 17 “moderate” solar flare ended up making one.
Begin Time: 2012 Jun 06 2003 UTC
Description: Type IV emissions occur in association with major eruptions on the sun and are typically associated with strong coronal mass ejections and solar radiation storms
The M-Class flare from Wednesday did produce a Coronal Mass Ejection. This image by STEREO Ahead COR2 from a side view of the Sun indicates that a majority of the cloud is headed south. There may be a small portion that could be Earth directed. Stay tuned for further updates.
Type IV is a smooth continuum of broadband bursts primarily in the meter range (30–300 MHz). These bursts are associated with some major flare events beginning 10 to 20 minutes after the flare maximum, and can last for hours.
A minor geomagnetic storm that crested during the opening hours of June 12th is subsiding now. At maximum, it ranked 5 on the 0-to-9 K-index scale of magnetic disturbances and turned the skies purple over Dawsonville, New Brunswick:
"The auroras lasted just a couple of minutes, [but they were beautiful]," says photographer Bart Firth. "They were blue to purple in color."
The storm was sparked by an episode of "negative IMF." That is, south-pointing magnetic fields in the solar wind opened a crack in Earth's magnetosphere; solar wind poured in and fueled the display. NOAA forecasters estimate a 10% to 20% chance of similar storms in the next 24 hours as the solar wind continues to blow.
CHANCE OF FLARES: NOAA forcasters estimate a 40% chance of M-class solar flares today as a phalanx of sunspots turns toward Earth. The most likely source of geoeffective eruptions is sunspot AR1504, which has grown into an active region almost 10 times wider than Earth. Solar flare alerts: text, voice.
As predicted, the sunspot has flared. Magnetic fields above AR1504 erupted on June 13th at 1319 UT, producing a long-duration M1-class solar flare. NASA's Solar Dynamics Observatory recorded the extreme UV glow of the blast:
The ongoing explosion is taking hours to unfold, which means it is very powerful despite its middling M1-peak. Long duration flares often hurl coronal mass ejections (CMEs) into space, and this one is probably no exception. Stay tuned for updates about a possible Earth-directed CME.
We're on the cusp of one of the greatest scientific accomplishments of all time, but we may not know when the moment strikes. Or, rather, there may be no moment.
An artist's rendering of the two Voyager spacecraft at the outer edge of our solar system (NASA)
Last week, in the corners of the Internet devoted to outer space, things started to get a little, well, hot. Voyager 1, the man-made object farthest away from Earth, was encountering a sharp uptick in the number of a certain kind of energetic particles around it. Had the spacecraft become the first human creation to "officially" leave the solar system?
It's hard to overstate how wild an accomplishment this would be: A machine, built here on Earth by the brain- and handiwork of humans, has sailed from Florida, out of Earth's orbit, beyond Mars, beyond the gas giants of Jupiter and Saturn, and may now have left the heliosphere -- tiny dot in the universe beholden to our sun. Had it really happened? How would we know?
We're not quite there yet, Voyager's project scientist and former head of NASA's Jet Propulsion Lab, Edward Stone, told me. The spacecraft is on its way out -- "it's leaving the solar system" -- but we don't know how far it has to go or what that transition to interstellar space will look like.
Voyager launched in 1977. Today, Voyager I is about 121 astronomical units (the rough distance from the Sun to the Earth) away. That is so far that it takes 16 hours for the radio signals it transmits to reach us. (Voyager II is about 22 astronomical units -- approximately seven years -- behind.) It is traveling at about 17 kilometers per second (38,000 miles per hour), propelled by the slingshot effect from flying by Jupiter and Saturn. ("It's well above escape velocity," Stone said.) The spacecraft's cameras have been turned off since 1990, when it took the pictures for the famous Family Portrait mosaic that captures the planets as they appeared as Voyager I looked back over the solar system it had traveled across.
Family Portrait (NASA)
Now the data coming back aren't photographs but levels of different kinds of particles in the outer edge of the sun's bubble (the heliosphere), known as the heliosheath, the farthest the solar winds reach, which Voyager I entered in December 2004. And it was some of those data -- the levels of a certain cosmic-ray particle -- that provoked the recent speculation that Voyager I had finally flown the coop.
Some cosmic ray particles enter the heliosphere and we can see them here from Earth. But a slower type has a hard time entering the heliosphere. Last month, the sum of those slower particles, suddenly ticked up about 10 percent, "the fastest increase we've seen," Stone says. But an uptick does not mean Voyager has crossed over, though it does mean we're getting close. When Voyager does finally leave and enter the space "out there where all the particles are," the level will stop rising. The rising itself means that Voyager is not out there, yet. "But," cautions Stone, "we don't know. I mean this is the first time any spacecraft has been there." Since nothing's ever been there before, we don't know what it will look like, which makes it a little hard to recognize "it" at all. "That's the exciting thing," he continues.
Two other indicators that Voyager I has left the heliosphere -- an absence of certain lower-energy particles that don't leave our system and a change in the magnetic field -- have not yet happened, though there have been some decreases of the energy particles, but, Stone says, "it's not zero." Additionally, to complicate matters even further, beyond the heliosphere in interstellar space there are comets that orbit the sun and are therefore part of the solar system.
It would be nice, fulfilling even, if at the edge of the heliosphere there were, well, an actual edge, a boundary between our bubble and the cosmos. But, it's probably not going to be so cut and dry. "The boundary," Stone postulates, "will not be an instantaneous thing. [Voyager] won't suddenly be outside." Rather, the exit will be turbulent, "a mix of inside and outside," and the work of Stone and the other Voyager scientists is trying to square the different data -- the particles and the magnetic field -- to try to understand what that transition from inside to outside looks like. That turbulent region may take several months to get through.
But even without a clean break in the offing, it's hard not to sit on the edge of your seat to wait for this moment -- this months-long moment -- to pass. "We're looking at our data every day -- we listen to these spacecraft every day, for a few hours every day -- to keep track of what's going on. ... It's very exciting from a scientific point of view, when you're seeing something that nobody's seen before."
So perhaps Voyager won't make its mark with a sudden, defining event that echoes across generations as a sort of before-and-after dividing line across human history, like the line separating the time when a human's voice had never traveled across a wire to an ear miles away -- and when it had -- or before a human foot had left its imprint on the moon, and when that print was there. But Stone is okay with that: "Well you know actually Voyager has had a lot of those moments as we flew by Jupiter, Saturn, Uranus, and Neptune. One after the other, we found something that we hadn't realized was there to be discovered."