On July 6, 2016, engineers instructed NASA’s Solar Dynamics Observatory, or SDO, to roll 360 degrees on one axis. SDO dutifully performed the seven-hour maneuver, while producing some dizzying data: For this period of time, SDO images – taken every 12 seconds – appeared to show the sun spinning, as if stuck on a pinwheel. This video was taken by SDO’s Atmospheric Imaging Assembly instrument in extreme ultraviolet wavelengths that are typically invisible to our eyes, but was colorized here in gold for easy viewing.
This maneuver happens twice a year to help SDO’s Helioseismic and Magnetic Imager, or HMI, instrument take precise measurements of the solar limb, the outer edge of the sun as seen by SDO. Were the sun perfectly spherical, this would be a much simpler task. But the solar surface is dynamic, leading to occasional distortions. This makes it hard for HMI to find the sun’s edge when it’s perfectly still. HMI’s biannual roll lets each part of the camera look at the entire perimeter of the sun, helping it map the sun’s shape much more precisely.
HMI tracks variations in the solar limb over time to help us understand how the shape of the sun changes with respect to the solar cycle, the sun’s 11-year pattern of solar activity. The more we know about what drives this activity – activity that can include giant eruptions of solar material and radiation that can create hazards for satellites and astronauts – the better we may someday predict its onset.
Forecasters expect the next Solar Minimum to arrive in 2019-2020. Between now and then, there will be lots of spotless suns. At first, the blank stretches will be measured in days; later in weeks and months. Don’t expect space weather to grow quiet, however. Solar Minimum brings many interesting changes. For instance, as the extreme ultraviolet output of the sun decreases, the upper atmosphere of Earth cools and collapses. This allows space junk to accumulate around our planet. Also, the heliosphere shrinks, bringing interstellar space closer to Earth. Galactic cosmic rays penetrate the inner solar system with relative ease. Indeed, a cosmic ray surge is already underway. Goodbye sunspots, hello deep-space radiation!
The average number of sunspots has been dropping steadily for months:
The Mercury transit was seen by observers on the ground and by satellites in space. The best views of the transit came from the Solar Dynamics Observatory (SDO) spacecraft, whose multiple imagers showed the transit in different parts of the spectrum:
Another SDO view:
Here is a NASA panel discussion about the transit:
On Monday the planet Mercury will transit across the face of the Sun as seen from earth between about 7:12 am and 2:42 pm EDT : Mercury Enters Spotlight on May 9 – NASA.
This video shows the path that it will take:
Don’t ever look directly at the sun. There are various safe ways to observe the transit such as using a solar filter over a telescope aperature or to project the image onto a white board with a pinhole. The transit will also be webcast from various sites.
Here are some sites with information on webcasts and tips on viewing the transit directly:
NASA launched a new website Monday so the world can see images of the full, sunlit side of the Earth every day. The images are taken by a NASA camera one million miles away on the Deep Space Climate Observatory (DSCOVR), a partnership between NASA, the National Oceanic and Atmospheric Administration (NOAA) and the U.S. Air Force.
Earth rotates through an entire day as captured in this animation of 22 still images taken on Sept. 17, 2015 by NASA’s Earth Polychromatic Imaging Camera (EPIC) camera on the Deep Space Climate Observatory (DSCOVR) spacecraft. Credits: NASAOnce a day NASA will post at least a dozen new color images of Earth acquired from 12 to 36 hours earlier by NASA’s Earth Polychromatic Imaging Camera (EPIC). Each daily sequence of images will show the Earth as it rotates, thus revealing the whole globe over the course of a day. The new website also features an archive of EPIC images searchable by date and continent.
The primary objective of NOAA’s DSCOVR mission is to maintain the nation’s real-time solar wind monitoring capabilities, which are critical to the accuracy and lead time of space weather alerts and forecasts from NOAA. NASA has two Earth-observing instruments on the spacecraft. EPIC’s images of Earth allow scientists to study daily variations over the entire globe in such features as vegetation, ozone, aerosols, and cloud height and reflectivity.
EPIC is a four megapixel CCD camera and telescope. The color Earth images are created by combining three separate single-color images to create a photographic-quality image equivalent to a 12-megapixel camera. The camera takes a series of 10 images using different narrowband filters — from ultraviolet to near infrared — to produce a variety of science products. The red, green and blue channel images are used to create the color images. Each image is about 3 megabytes in size.
“The effective resolution of the DSCOVR EPIC camera is somewhere between 6.2 and 9.4 miles (10 and 15 kilometers),” said Adam Szabo, DSCOVR project scientist at NASA’s Goddard Space Flight Center, Greenbelt, Maryland.
Since Earth is extremely bright in the darkness of space, EPIC has to take very short exposure images (20-100 milliseconds). The much fainter stars are not visible in the background as a result of the short exposure times.
The DSCOVR spacecraft orbits around the L1 Lagrange point directly between Earth and the sun. This orbit keeps the spacecraft near the L1 point and requires only occasional small maneuvers, but its orbit can vary from 4 to 15 degrees away from the sun-Earth line over several years.
EPIC was built by Lockheed Martin’s Advanced Technology Center, in Palo Alto, California. Using an 11.8-inch (30-centimeter) telescope and 2048 x 2048 CCD detector, EPIC measures in the ultraviolet, visible and near-infrared areas of the spectrum. The data from all 10 wavelengths are posted through a website hosted by the Atmospheric Science Data Center at NASA’s Langley Research Center, Hampton, Virginia. All images are in the public domain.
NASA uses the vantage point of space to increase our understanding of our home planet, improve lives, and safeguard our future. NASA develops new ways to observe and study Earth’s interconnected natural systems with long-term data records. The agency freely shares this unique knowledge and works with institutions around the world to gain new insights into how our planet is changing.
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