THE
AFTERMATH
OF A
STELLAR
TANTRUM
Around 3,500 years ago,
a spectacular explosion
rocked the star-forming
region Sharpless 2–106.
The culprit: a massive star,
called S106 IR, at the heart
of this nebula. S106 IR
formed from the collapse of
its parent molecular cloud a
mere 100,000 years ago. The
star then devoured nearby
gas, ballooning from an esti-
mated initial 10 times the
mass of the Sun to 15 solar
masses. Around that time,
scientists think, a compan-
ion star may have interacted
with S106 IR, causing the
explosion. — CAITLYN BUONGIORNOWWW.ASTRONOMY.COM 11
SPACEX DEFENDS STARLINK
OVER COLLISION CONCERNS
As SpaceX’s Starlink constellation of internet service satellites has grown — with
nearly 2,000 in orbit at the end of February — so has scrutiny of its potential to
cause collisions.
On Dec. 3 of last year, China submitted a complaint to the United Nations
Committee on the Peaceful Uses of Outer Space, saying that the nation’s crewed
space station was forced to maneuver to avoid a potential collision with a Starlink sat-
ellite on two occasions, July 1 and Oct. 21, 2021.
Then, on Feb. 7, NASA’s human spaceflight division submitted a letter to the Federal
Communications Commission raising concerns about SpaceX’s plans for its second-
generation constellation of 30,000 more satellites. NASA said a megaconstellation of
that size would raise the risk of collisions in space that could threaten its satellites and
astronauts.
On Feb. 22, SpaceX pushed back on those concerns, arguing that Starlink was
designed to be safe and sustainable. The company cited several design features,
including that Starlink satellites are highly maneuverable and deorbit themselves after
their service life; their onboard collision avoidance-system autonomously takes action
to avoid collisions; and the satellites launch to very low orbits to perform initial system
checks — just 130 miles (210 kilometers) high, where they quickly reenter the atmo-
sphere if they fail to come online.
SpaceX experienced one risk of the latter strategy Feb. 3, when it launched a batch
of 49 Starlink satellites despite predictions of a geomagnetic storm. Flares from the
Sun enhanced activity in Earth’s magnetic field, warming the atmosphere and caus-
ing it to expand into space. SpaceX said the Starlink craft experienced 50 percent
more drag than usual and, as a result, 38 of the 49 satellites fell out of orbit and were
destroyed. “Despite such challenges, SpaceX firmly believes that a low insertion alti-
tude is key for ensuring responsible space operations,” the company said.
The statement also revealed details on how Starlink satellites autonomously avoid
collisions. If public tracking data show a Starlink satellite has a 1-in-100,000 chance of
a collision with another craft, it automatically “assumes maneuver responsibility” and
takes avoiding action. If data indicate a “high-probability conjunction with another
maneuverable satellite,” SpaceX says it coordinates any maneuvers with that satellite’s
operator.
“This is certainly the most detailed explanation SpaceX have given of their pro-
cedures,” Jonathan McDowell, an astrophysicist at the Harvard-Smithsonian Center
for Astrophysics, told Astronomy. “It is welcome, although a couple years later than it
could have been.” — MARK ZASTROWUP AND AWAY. A Falcon 9 rocket
launching from Cape Canaveral carries
46 Starlink satellites to orbit Feb. 21. SPACEX“SU
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