Late last year one of Nasa's most powerful space telescopes has turned its gaze on the Sun for the first time to capture this stunning image.
When a coronal hole is present, though, the wind speed can double to nearly 500 miles (800 km) per second. The material constantly flowing outward is called the solar wind, which typically 'blows' at around 250 miles (400 km) per second. While it's unclear what causes coronal holes, they correlate to areas on the sun where magnetic fields soar up and away, failing to loop back down to the surface, as they do elsewhere.
The holes are important to our understanding of space weather, as they are the source of a high-speed wind of solar particles that streams off the sun some three times faster than the slower wind elsewhere. The acceleration of particles in the magnetosphere is studied by NASA's Van Allen Probes mission.Īs Solar Cycle 24 fades, the number of flares each day will get smaller, but the coronal holes provide another source of space weather that needs to be understood and predicted.Ĭoronal holes are a typical feature on the sun, though they appear at different places and with more frequency at different times of the sun's activity cycle.
The polar coronal hole can remain visible for five years or longer.Įach time a coronal hole rotates by the Earth we can measure the particles flowing out of the hole as a high-speed stream, another source of space weather.Ĭharged particles in the Earth's radiation belts are accelerated when the high-speed stream runs into the Earth's magnetosphere. They can be seen for a long time, although the exact shape changes all the time. In the parts of the corona where the particles leave the sun, the glow is much dimmer and the coronal hole looks dark.Ĭoronal holes were first seen in images taken by astronauts on board NASA's Skylab space station in 19. Those trapped particles can heat up and glow, giving us the lovely AIA images. Particles moving along those magnetic fields can leave the sun rather than being trapped near the surface. 1, 2015 by the Atmospheric Imaging Assembly (AIA) instrument on NASA's Solar Dynamics Observatory, shows the coronal hole as a dark region in the south.Ĭoronal holes are regions of the corona where the magnetic field reaches out into space rather than looping back down onto the surface. The incredible image was captured on Jan. Known as a coronal hole, the phenomenon occurred near the south pole - and is seen as a dark area covered all of its base in these stunning images. SDO captured images of the filament in numerous wavelengths, each of which helps highlight material of different temperatures on the sun.īy looking at such features in different wavelengths and temperatures, scientists learn more about what causes these structures, as well as what catalyzes their occasional eruptions.Įarlier in the year, a huge hole appeared on the solar surface. Sometimes they also erupt out into space, releasing solar material in a shower that either rains back down or escapes out into space, becoming a moving cloud known as a coronal mass ejection, or CME. 'This means the line is, in fact, an enormous swatch of colder material hovering in the sun's atmosphere, the corona,' Nasa said.įilaments can float sedately for days before disappearing. Nasa's Solar Dynamics Observatory, or SOD, shows colder material as dark and hotter material as light. Stretched out, that line – or solar filament as scientists call it – would be more than 533,000 miles long, and longer than 67 Earths lined up in a row. It shows a vast filament of material snaked across the lower half of the sun on Feb.10, 2015, forming a dark 'smile' line. Just days ago, after Hubble captured an amazing image of a 'smiling' galaxy, Nasa has revealed an equally emotive picture of the sun looking sad. Scientists are looking at that data now to see if they can determine what circumstances might have led to flares eruptions alone. In this case, the sun produced only flares and no CMEs, which, while not unheard of, is somewhat unusual for flares of that size. They can occur by themselves or can be accompanied by what's called a coronal mass ejection, or CME, in which a giant cloud of solar material erupts off the sun, achieves escape velocity and heads off into space. Solar flares are bursts of light, energy and X-rays.
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Five years into its mission, SDO continues to send back tantalizing imagery to incite scientists' curiosity.įor example, in late 2014, SDO captured imagery of the largest sun spots seen since 1995 as well as a torrent of intense solar flares.