Scroll down to read this post.


My July fund-raising campaign, celebrating the 13th anniversary of the start of this website, has now ended. This was the second most successful monthly fund-raising campaign ever. Thank you again to everyone who has who donated or subscribed. It is difficult to explain what your support means to me.


You can still donate or subscribe to support my work if you wish, either by giving a one-time contribution or a regular subscription. There are four ways of doing so:


1. Zelle: This is the only internet method that charges no fees. All you have to do is use the Zelle link at your internet bank and give my name and email address (zimmerman at nasw dot org). What you donate is what I get.


2. Patreon: Go to my website there and pick one of five monthly subscription amounts, or by making a one-time donation.

3. A Paypal Donation:

4. A Paypal subscription:

5. Donate by check, payable to Robert Zimmerman and mailed to
Behind The Black
c/o Robert Zimmerman
P.O.Box 1262
Cortaro, AZ 85652

Scientists confirm Parker entered Sun’s corona in April 2021

Scientists yesterday announced that the Parker Solar Probe successfully entered the Sun’s corona for the first time during its April 2021 close fly-by.

More information here, including some excellent short movies made from images created by Parker’s instruments.

The top edge of the corona is dubbed the Alfvén surface, and Parker’s passage across that boundary three different times during the April ’21 fly-by revealed it to be a sharp boundary that also has a great deal of topography. From the second link:

The first time Parker passed the Alfvén surface was the longest; it flew through the atmosphere for about five hours. Even as it continued flying toward the Sun, though, it popped back out, only to submerge again more deeply when it was at its closest approach — but briefly, that time exiting after just half an hour. Then, on its way outward, the spacecraft once again skimmed beneath the surface for a few hours.

“[The Alfvén surface] has to be wrinkly,” Kasper says. “It’s not fuzzy — it’s well-defined while we’re under it — but the surface has some structure to it.” So while the probe sees a smooth change in conditions while crossing the boundary, where the boundary is can change. The reason for this wrinkly surface is still an open question, though the researchers suspect the crossing over a pseudostreamer lower in the corona pushed the boundary out to enable the first crossing.

What’s clear is that inside the Sun’s atmosphere, conditions are different than just outside. Parker saw plasma waves moving back and forth instead of flowing outward. That difference was visible not just to the SWEAP and FIELDS instruments, which measure particles and electric and magnetic fields, respectively, but also to the probe’s WISPR imager.

The Parker science team also indicated that the preliminary data from the probe’s next two fly-bys — the most recent in November that was the closest yet — suggest it passed through the corona then as well.

One of the biggest unsolved mysteries about the Sun’s corona is that it appears to have a temperature in the millions of degrees, far hotter than the Sun’s surface below, something that is counter-intuitive. The expectation was that the atmosphere would be cooler than the surface. Finding out why the corona is hotter is one of the main science goals of Parker. It appears the probe is finally gathering data that might help solve that mystery.

Genesis cover

On Christmas Eve 1968 three Americans became the first humans to visit another world. What they did to celebrate was unexpected and profound, and will be remembered throughout all human history. Genesis: the Story of Apollo 8, Robert Zimmerman's classic history of humanity's first journey to another world, tells that story, and it is now available as both an ebook and an audiobook, both with a foreword by Valerie Anders and a new introduction by Robert Zimmerman.

The ebook is available everywhere for $5.99 (before discount) at amazon, or direct from my ebook publisher, ebookit. If you buy it from ebookit you don't support the big tech companies and the author gets a bigger cut much sooner.

The audiobook is also available at all these vendors, and is also free with a 30-day trial membership to Audible.

"Not simply about one mission, [Genesis] is also the history of America's quest for the moon... Zimmerman has done a masterful job of tying disparate events together into a solid account of one of America's greatest human triumphs."--San Antonio Express-News


  • William

    I would like to land on the sun one day. Of course I would only go at night.

  • I did not know that the corona had a definite boundary; thinking of gas diffusion, and all. The videos were fantastic, and it’s not only the solar scientists finding out about the Sun.

  • Peter Monta

    It reminds me of Vernor Vinge’s Zones of Thought. If I remember correctly, the boundaries were said to be irregular and dynamic with a fractal dimension slightly larger than 2.

    Fortunately the Parker probe apparently still operates correctly in the “slow zone”.

  • Spectrum Shift

    What have we learned ? There’s more to “know” than we can possibly imagine.

Readers: the rules for commenting!


No registration is required. I welcome all opinions, even those that strongly criticize my commentary.


However, name-calling and obscenities will not be tolerated. First time offenders who are new to the site will be warned. Second time offenders or first time offenders who have been here awhile will be suspended for a week. After that, I will ban you. Period.


Note also that first time commenters as well as any comment with more than one link will be placed in moderation for my approval. Be patient, I will get to it.

Leave a Reply

Your email address will not be published. Required fields are marked *