Sky & Telescope - April 2021 - 4

SPECTRUM

by Peter Tyson

Our Moment in the Sun

The Essential Guide to Astronomy
Founded in 1941 by Charles A. Federer, Jr.
and Helen Spence Federer

THESE ARE EXCITING TIMES for studies of our star - you might

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APRIL 2 021 * SK Y & TELESCOPE

EDITORIAL
Editor in Chief Peter Tyson
Senior Editors J. Kelly Beatty, Alan M. MacRobert
Science Editor Camille M. Carlisle
News Editor Monica Young
Associate Editor Sean Walker
Observing Editor Diana Hannikainen
Consulting Editor Gary Seronik
Editorial Assistant Sabrina Garvin
Senior Contributing Editors
Dennis di Cicco, Richard Tresch Fienberg,
Robert Naeye, Roger W. Sinnott
Contributing Editors
Howard Banich, Jim Bell, Trudy Bell, John E. Bortle,
Greg Bryant, Thomas A. Dobbins, Alan Dyer,
Tom Field, Tony Flanders, Ted Forte, Steve Gottlieb,
David Grinspoon, Shannon Hall, Ken Hewitt-White,
Johnny Horne, Bob King, Emily Lakdawalla,
Rod Mollise, James Mullaney, Donald W. Olson,
Jerry Oltion, Joe Rao, Dean Regas, Fred Schaaf,
Govert Schilling, William Sheehan, Mike Simmons,
Mathew Wedel, Alan Whitman, Charles A. Wood
Contributing Photographers
P. K. Chen, Akira Fujii, Robert Gendler,
Babak Tafreshi

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even call it a golden age. In the past decade alone, we've advanced
our understanding tremendously, with three instruments in particular deserving special attention.
Launched in 2010, the Solar Dynamics Observatory has taken
millions of images of the Sun. On the roiling solar surface, it has detected
plasma tornadoes spinning at up to 300,000 kilometers per hour (186,000
mph), and giant plasma waves that whip across the surface at close to 5 million kph. It has revealed large " dark " patches whose disappearance can help
scientists determine when the Sun's magnetic ﬁeld reversed. It has discovered
an entirely new kind of solar explosion - spontaneous magnetic reconnection -
which might aid in resolving a long-standing mystery: why the Sun's corona is
millions of degrees hotter than its surface.
Meanwhile, the Parker Solar Probe is making its
own revelations (S&T: Nov. 2020, p. 20). Launched in
2018 and approaching within 15 million miles of the
solar surface, this well-shielded spacecraft is seeking
answers to that coronal mystery as well as investigating how the solar wind arises and why it spews from
the corona in the way it does. Parker has already spied
never-before-seen switchbacks, in which the magnetic
S The entire Earth would
ﬁeld embedded in the solar wind suddenly reverses
fit inside this single
direction for seconds or minutes at a time.
sunspot imaged by the
Even more recently, in December 2019, Hawai'i's
Inouye Solar Telescope.
new Daniel K. Inouye Solar Telescope captured its ﬁrst
image of the Sun. With its 4-meter (13-foot) primary mirror, the Inouye Solar
Telescope enables us to see features three times smaller than anything we could
see before. In coming years, it will look at how the Sun's magnetic ﬁelds are
generated and destroyed, and what roles they play in the organization of plasma
structure and the abrupt releases of energy seen on our own and other stars. It
will also explore the mechanisms responsible for solar variability - important
for protecting astronauts in space and power grids on Earth.
Despite all we've learned - and because of it - many puzzles remain. Colin
Stuart addresses one of the knottiest in his cover story on page 12: the solar
abundance problem. It boils down to how many elements heavier than hydrogen
and helium the Sun contains. Two groups of scientists, who each swear by their
results, come up with different answers. As Stuart explains, that calls into question our understanding not only of our own star but of all
stars and even their planets.
Keep your shades handy. Like the Sun itself, future ﬁndings promise to be nothing short of dazzling.

AMERICAN ASTRONOMICAL
SOCIETY
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State University
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At-Large Trustees Marcel Agüeros, Columbia University;
Kelsey Johnson, University of Virginia; Tereasa Brainerd,
Boston University; Hannah Jang-Condell, University of
Wyoming; Edmund Bertschinger, MIT

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Sky & Telescope - April 2021

Table of Contents for the Digital Edition of Sky & Telescope - April 2021