Sky & Telescope - March 2024 - 10

Sunspot number
PLOT OF SUNSPOT NUMBERS: NOAA SWPC;
IC 342: ESA / EUCLID / EUCLID CONSORTIUM / NASA, IMAGE
PROCESSING BY J.-C. CUILLANDRE (CEA PARIS-SACLAY), G. ANSELMI; CC BY-SA 3.0 IGO
NEWS NOTES
THE SUN
New Forecast Resets Solar
Cycle Expectations
A NEW FORECAST has sunspot
numbers and other solar activity
peaking sooner and at a higher level
than expected. This new prediction
has important consequences for space
operations, including provisions for the
safety of satellites and astronauts.
The Sun's 11-year cycle takes it from
being relatively sunspot-less at minimum,
to spot-filled at maximum, and
back again. With more sunspots come
more frequent solar flares, coronal mass
ejections, and a stronger solar wind.
In 2019, a panel of researchers
worked with the National Oceanic and
Atmospheric Administration's Space
Weather Prediction Center (SWPC)
to forecast the current Solar Cycle 25
(S&T: Jan. 2021, p. 12). They originally
predicted that solar maximum would
occur between December 2024 and
March 2026, with a monthly sunspot
count around 105 to 125. That's low
compared to the average peak number.
In the years since, the Sun surprised
us to the upside, with more sunspots
Euclid's First Light
100
150
200
50
2020
2022
2024
2026
Year
2028
2030
pThe plot shown here compares the number of sunspots predicted now (purple line) to the
number predicted in 2019 (pink shaded area). The jagged black line shows the actual number
of sunspots recorded each month, which is higher than the 2019 prediction.
and greater solar activity than expected.
Now, an updated prediction calls for
Solar Cycle 25 to peak between January
and October 2024, with a maximum
sunspot number between 137 and 173.
The prediction marks the debut
of SWPC's experimental prediction
product, updated on a monthly basis on
the Space Weather Prediction Testbed
website. " We expect that our new
experimental forecast will be much
more accurate than the 2019 panel
prediction, " says Mark Miesch (University
of Colorado, Boulder), solar cycle
lead at SWPC. " It's a pretty significant
change. " In addition to more accurate
space weather forecasts, the revised
predictions will also help astronomers
understand the solar interior.
" What jumped out at me from the
prediction is its asymmetry, with a
decay phase much longer than its rise
phase, " says Ryan French (National
Solar Observatory), who was not
involved in the prediction. " This means
we can look forward to continuing high
solar activity (including frequently
enhanced aurorae) until at least 2027. "
Another upside is that, according
to the new forecast, the April 8th solar
eclipse will occur around solar maximum,
which could give us more impressive
views of the corona during totality.
¢COLIN STUART
The European Space Agency has published the first color
images from its Euclid space telescope, and they're gorgeous.
One of the first galaxies Euclid observed is the
Milky Way-like IC 342, 11 million light-years away in Camelopardalis.
The image assigns 0.7, 1.1, and 1.7 microns
to the blue, green, and red channels, respectively. Hot
stars appear white, hot hydrogen gas appears blue, and
regions rich in dust and cooler, molecular gas are red. Between
the spiral arms, far more distant galaxies are visible.
Each image from the 1.2-meter Euclid telescope covers
an area more than twice the size of the full Moon, with an
angular resolution of 0.2 arcseconds. Euclid is now using
its infrared instrument to map the 3D distribution of 1.5 billion
galaxies out to distances of 10 billion light-years. This
map will reveal the evolution of the large-scale structure
of the universe, governed by dark matter and dark energy.
Meanwhile, precision measurements of galaxy shapes,
which are affected by the gravitational distortions of
intervening matter, will yield information on dark matter's
distribution. " Everything suggests that Euclid will perform
even better than expected, " says science team member
Henk Hoekstra (Leiden University, The Netherlands), " and
that the mission will reach its scientific goals. "
¢ GOVERT SCHILLING
10 MARCH 2024 * SKY & TELESCOPE
2032
Number of sunspots observed monthly
Range of Cycle 25 prediction
New, experimental prediction

Sky & Telescope - March 2024

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