Earthshine


This video takes us around the Moon and shows how it is illuminated not only by the brilliant light of the Sun but also by light reflected from the Earth. The trip starts on the side facing away from Earth where part of the surface is brightly illuminated by the Sun but the rest is totally dark. Moving around the Moon, the Earth rises, and its reflected bluish light illuminates the Moon’s surface. This dull glow is the earthshine. (You can clearly see it from Earth when the Moon appears as a crescent in the evening or morning sky.) When the Sun emerges from behind the Moon, the brilliant crescent is seen, but the earthshine is still faintly visible.

Video Credit: ESO

SDO Sees the Moon Transit the Sun. Twice.


On 9 and 10 September, 2018, the Solar Dynamics Observatory, SDO, saw two lunar transits as the Moon passed in front of the Sun. A transit happens when one celestial body passes between another and an observer. This first lunar transit lasted one hour, from 2030 to 2130 UTC and covered 92 percent of the Sun. The second transit happened several hours later, 0152 until 0241 UTC and only obscured 34 percent of the Sun at its peak.

From SDO’s perspective, the Moon seems to move in one direction and then double back. It appears to do so because the spacecraft’s orbit catches up and passes the Moon during the first transit.

Image Credits: NASA

Earthshine


This video takes us around the Moon and shows how it is illuminated not only by the brilliant light of the Sun but also by light reflected from the Earth. The trip starts on the side facing away from Earth where part of the surface is brightly illuminated by the Sun but the rest is totally dark. Moving around the Moon, the Earth rises, and its reflected bluish light illuminates the Moon’s surface. This dull glow is the earthshine. (You can clearly see it from Earth when the Moon appears as a crescent in the evening or morning sky.) When the Sun emerges from behind the Moon, the brilliant crescent is seen, but the earthshine is still faintly visible.

Video Credit: ESO

A Hole on the Sun


coronalholeThe Solar Dynamics Observatory took these images of a large coronal hole on the Sun last week. Coronal holes are the source of a high-speed wind of solar particles that streams off the Sun some three times faster than the normal solar wind. It’s not clear what causes coronal holes, but they correlate to areas on the Sun where magnetic fields flow away from the surface without looping back as they do elsewhere.

Image Credit: NASA

Lines of Force


magnetic_field_lines_2When we were in school, many of us saw that demonstration about a magnet’s lines of force using iron filings on a piece of paper covering a magnet. This illustration lays a depiction of the Sun’s magnetic fields over an image taken by the Solar Dynamics Observatory. Note how the magnetic fields are densest near the bright spots visible on the Sun’s surface. They are magnetically strong active regions, and many of the field lines link one active region with another.

Image Credit: NASA

Cascading Magnetic Arches


This time lapse video was taken by the Solar Dynamics Observatory using UV light and shows a dark solar filament above the Sun’s surface that became unstable and erupted, generating a cascade of magnetic arches. A small eruption to the upper right of the filament may have been related to its collapse. The arches of solar material glow as they emit light in extreme ultraviolet wavelengths, highlighting the charged particles spinning along the Sun’s magnetic field lines.

Video Credit: NASA

Coronal Loops


Coronal LoopsThe Atmospheric Imaging Assembly instrument aboard the Solar Dynamics Observatory images the solar atmosphere in 10 wavelengths every 10 seconds. Its data is used to link changes in the surface to interior changes in the Sun.In this image the Sun’s magnetic field can be readily visualized through bright strands called “coronal loops”. Loops are shown here in a blended overlay with the magnetic field measured by SDO’s Helioseismic and Magnetic Imager shown underneath. Blue and yellow represent the opposite polarities of the magnetic field.

Image Credit: NASA

Canyon of Fire


A magnetic filament of solar material erupted from the sun in late September. The 200,000 mile long filament ripped through the Sun’s corona, leaving behind what looks like a canyon of fire. This video combines two days of satellite data. The glowing canyon traces the channel where magnetic fields held the filament aloft before the explosion.

These images were captured by the Solar Dynamics Observatory which monitors the Sun in a variety of wavelengths. The red images shown in the movie highlight plasma at temperatures of 50,000 °C and are good for observing filaments as they form and erupt. The yellow images, showing material with temperatures around 500,000 °C, are useful for observing material flowing along the Sun’s magnetic field lines. This shows up in the movie as loops across the area of the eruption. The brown images at the beginning of the movie show material at temperatures of 1,000,000 °C. Comparing the brown with the other colors  reveals that the two swirling ribbons moving farther away from each other are the footprints of the giant magnetic field loops, which are growing and expanding as the filament moves upward.

[youtube http://www.youtube.com/watch?v=Qurh_BZ-O2E]

Video Credit: NASA

An Eclipse


sunvenusuv3A rare solar eclipse occurred last year. Usually it’s the Moon that eclipses the Sun. Last year, the planet Venus took its turn. The black dot in the picture is Venus crossing in front of the Sun. In this case, the Sun was imaged in three colors of ultraviolet light by the Earth-orbiting Solar Dynamics Observatory.  The dark region on the right of the Sun’s face is a large coronal hole.

As I said, these eclipses are rare. The next Venusian solar eclipse will occur in 2117.

Image Credit: NASA

A Lunar Crossing


NASA has a fleet of satellites that observe the Sun. Occasionally, the Moon moves between the Solar Dynamics Observatory and the Sun. That happened for about 1-1/2 hours on 6 August. While the view is obscured, some science data is lost, but some engineering data is gained. The sharp edge of the Moon’s limb provides an opportunity to measure how the satellite’s optics are diffracting light, and that information is used to maintain calibration for sharp imaging. This time lapse video compresses the event into 11 seconds.

[youtube https://www.youtube.com/watch?v=QrcNzAmgEhc]

Video Credit: NASA

Eclipses Seen From Orbit


SDOEarthEclipse-LunarTransit2013NASA’s Solar Dynamics Observatory (SDO) recently entered its semiannual eclipse season, a period of three weeks during which Earth blocks its view of the sun for a part of each day. Yesterday, SDO observed two transits. Earth blocked SDO’s view of the Sun from about 06:15 to 07:45 UTC, and from around 11:30 to 12:45 UTC, the Moon moved between the satellite and the Sun for a partial eclipse.

The edge of Earth’s shadow appears fuzzy. That’s because some light from the Sun comes through Earth’s atmosphere. The shadow line of the Earth appears almost straight because the Earth is much closer to SDO and appears to be larger than the Sun.

Because the moon has no atmosphere, its curved shape can be seen clearly, and the line of its shadow is crisp and clean. Any spacecraft observing the sun from Earth orbit has to deal with such eclipses, but SDO‘s orbit is designed to minimize their interference.

Image Credit: NASA

Sun and Moon


On 7 October, 2010, NASA’s Solar Dynamics Observatory (SDO) recorded its first lunar transit when the new moon passed directly between the spacecraft (in geosynchronous orbit) and the sun. With SDO watching the sun in a wavelength of extreme ultraviolet light, the dark moon created a partial eclipse of the sun. Image Credit: NASA