SDO Stamps are on Sale!

USPS Forever stamps featuring SDO images were released by the Post Office on Friday in a ceremony at the Greenbelt, Maryland, Post Office. The stamps have 10 SDO images in each set:

The Summer Solstice (Northen Hemisphere) occurred at 11:32 pm ET yesterday (June 20, 2021). Celebrate the solstice with SDO Stamps. Send someone the Sun!

SDO Images will be on US Stamps in June!

According to this NASA News Release, SDO images will be featured on a set of USPS First Class Forever stamps. Here's what the stamps will look like.

SDO's 100's of millions of images of the Sun’s dynamic and dazzling beauty have captivated millions of people. Near the summer solstice of 2021 you should be able to use these select 10 as beautiful stamps. Watch for them!

See SDO 4k Movies and Projected over Dublin

Trinity College Dublin (Ireland) is running a campaign in Dublin called City of Physics, showing the city of Dublin the beauty of physics. For their opening nights at the end of October, they projected images from the SDO instrument onto a city centre building. A short video is available to show the reaction of people in the city is at https://www.youtube.com/watch?v=mpEj_4aanDA. Check out the undergraduate students busy talking to Dubliners about SDO.

When SDO was launched TVs were displaying 720p resolution. In the five years since we have seen TV screens at 1080p and now UltraHD (3840 pixels by 2160 pixels.) This means we can show half of the Sun in full SDO resolution on commercially available screens. As a result, NASA has released a new of 4k ultra-HD movies of SDO imagery. These are also on YouTube. But to get the full impact of the UltraHD resolution you need to download the movies from SVS website.

The SDO webpage also has a list of UltraHD movies. We are planning to start releasing daily UltraHD movies.

If only UltraHD allowed us to show the entire disk of the Sun at the native resolution of the SDO imagers! But that must await the next generation of screens.

An Astronomical Picture of SDO

One of the cool things about knowing astronomers is the clever things they do with cameras. Here is one example. William Livingston, a solar astronomer living in Tucson, AZ, has taken pictures of the geostationary satellite ring since about 2001. These satellites tend to be big, and stay in one place over the Earth. By taking a long exposure (here about 9 hours), the satellites are almost points of light while the stars are long trails. (A nine hour star trail would cover 135 degrees of the sky.) Here is an example from March 2014. You can see 40 satellites in the center of the picture, all but one labeled with their name. SDO orbits the Sun every 24 hours, but at an angle to where these satellites orbit. Because it does not hover over the same place on Earth, SDO moves up and down through the geostationary satellites every day. So SDO isn't a point of light, it is another trail moving across the star trails. To help you find it, SDO is labeled on the plot. It is the very faint trail moving downward from between DirecTV 11 and DirecTV 8 to the l in Solar.

Dr. Livingston has been taking these pictures since 2001. I found a link about some of his first pictures. Another link describes the settings for digital cameras if you want to try to take pictures yourself. You'll need a dark sky and a steady mount!

Thanks to Bill for sending me these pictures.

Happy Perihelion!

Today, January 4, at 1200 UTC (7 am EST), the Earth was at perihelion. This is when we were closest to the Sun in our orbit around the Sun. At perihelion, the center of the Earth was a little over 147 million km (about 91.4 million miles) from the center of the Sun. Why do we care?

The Earth orbits the Sun along an ellipse. That means sometimes we’re farther from the Sun and sometimes closer. The average distance of the Earth from the Sun is about 150 million km (about 93 million miles, one Astronomical Unit or AU). Perihelion is the starting time for that orbit. The distance of perihelion is also important. The perihelion distance of the Earth is about 1.67% closer than the average distance.

When the Earth is closer to the Sun it receives more sunlight and when it is further away it receives less sunlight. That means the timing and distance of perihelion can affect our climate. That doesn’t mean that being closer to the Sun automatically means warmer weather.

Our seasons are caused by the tilt of the earth’s rotation axis compared to our orbit around the Sun. In January the northern hemisphere of the Earth is tilted away from the Sun and the northern latitudes have winter. At the same time those living in southern latitudes experience summer. Because the tilt determines the seasons we mark our seasons by the solstices and equinoxes.

But the changing distance does affect our climate. It appears to make southern winters a little less frigid and northern summers a little milder. In the past the difference was more dramatic.

The timing of perihelion in the year changes slowly. Right now perihelion happens in northern winter, while 11,000 years ago it happened in northern summer. That changed the severity of the seasons.

If we wait even longer (several hundred thousand years) the shape of the Earth’s orbit also changes, with the eccentricity changing from nearly 0 (almost circular) to the current value of 0.0167 to 0.06. A circular orbit means the distance to the Sun does not change, while a more elliptical orbit means the amount of sunlight hitting the Earth changes even more during the year. Right now the amount of sunlight hitting the Earth at perihelion is about 6.5% greater than what hits the Earth at the furthest distance. At an eccentricity of 0.06 that would increase to 27%.

These are just two of the Milankovitch cycles that were developed to explain glaciations.

SDO instruments were built to allow for the changing distance and apparent size of the Sun during a year. But it’s nice to know that those changes do other things as well.

Have a Happy Perihelion Day!

Camilla Corona SDO in Photonics Magazine

The last page of the February 2013 issue of Photonics Spectra featured the SDO mascot, Camilla Corona SDO. Her latest trips have been to the Emerald City ComiCon in Seattle and the SWSX in San Antonio. Camilla encourages children of all ages to ask questions about the Sun and space. She explores space in her spare time, flying to the stratosphere on balloons.
Congratulations to Camilla and Romeo Durscher, her executive secretary for creating an excellent excuse to ask questions.

The Think Scientifically Books are Out

The first two Think Scientifically books are available from SDO Educators Website. Each book focuses on a key science theme and includes a hands-on science lesson, math and language arts activities, and other educational resources that can be easily utilized in the classroom. The books are based on national standards and were written by teachers. Both books can be downloaded as pdf files from this website.

SDO began High Gain Antenna (HGA) handover season on February 23 and all handovers have been successful since then. The FOT is ready for the beginning of eclipse season on March 6. The next momentum unload maneuver in scheduled for March 14.