14 ASTRONOMY • OCTOBER 2019
QUANTUM GRAVITY
Quasars are the energetic centers of young
galaxies, powered by a supermassive black
hole that is surrounded by a vast disk of hot
material swirling inward. These turbulent
whirlpools energetically f ling matter and
radiation outward — allowing us to observe
them — which can be bad news for the host
galaxy. To form stars, a galaxy needs cold
gas that can clump together, not gas that’s
heated up and swept away by a raging black
hole. So, quasars are thought to signal a
downturn in a galaxy’s ability to form stars.
But Allison Kirkpatrick of the University
of Kansas found a set of galaxies that contain
both violent quasars and cold pools of gas,
meaning these galaxies might still be capable
of making new stars. She presented these
“cold quasars” June 12 at the 234th meeting
of the American Astronomical Society.
Kirkpatrick found the cold quasars
when matching quasars seen in the Sloan
Digital Sky Survey to those found by the
X-ray-seeking XMM-Newton telescope
and the infrared-hunting Herschel Space
Observatory. X-rays come from active black
holes, while infrared light traces glowing gas
and dust — prime star-forming regions.Quasars are sometimes seen enshrouded
in a cloud of material. Researchers think
this is an intermediate phase, when the qua-
sar has turned on but hasn’t yet had time to
blow away the dust and gas around it. Such
dust-obscured quasars appear red because
as their light shines through the surround-
ing material, it picks up a reddish hue, simi-
lar to the way a sunset appears red when
light from the setting Sun travels through
progressively more of Earth’s atmosphere.
But Kirkpatrick spotted bright blue,
luminous quasars within galaxies with cold
gas signatures. That implies the quasars
have blown away the material immediately
around them but haven’t swept the gas
and dust entirely out of the galaxy yet. She
theorizes that cold quasars are yet another,
shorter intermediate phase lasting 10 mil-
lion to 100 million years. This cosmically
brief period could explain why cold quasars
seem novel: They’re simply not around long
enough to show up in big numbers.
To find out just how many galaxies go
through this stage, Kirkpatrick is seeking
more cold quasars, which will reveal whether
this phase is common or rare.^ — K.H., J.P.Cold quasars are a new stage
of galaxy evolution
SpaceX’s ambitious Starlink project could
put more than 10,000 satellites into orbit
and rewrite the future of the internet. After
a May launch released the first sixty 500-
pound (227 kilograms) satellites, they were
clearly visible in the night sky.
But CEO Elon Musk had repeatedly said
on Twitter that the satellites wouldn’t be
seen. Astronomers now worry the satellites
could increase light pollution, interfere with
radio signals, and contribute to the growing
issue of space debris. This image of galaxies,
captured May 25 from Lowell Observatory in
Arizona, is marred by reflected light from more than 25 Starlink satellites passing overhead.
In early June, several astronomical groups, including the American Astronomical Society (AAS), issued
statements expressing concern about Starlink’s potential to damage research. The AAS and other groups
are now in discussions with SpaceX about mitigating impacts of future satellite launches. — K.H.Astronomy groups concerned about
Starlink satellites
1,
The number of
new supernovae,
or exploding
stars, captured
by the Subaru
Telescope,
including nearly
60 objects more
than 8 billion
light-years away.
VICTORIAG
IRGIS/LOW
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L^ OBSERVATORYRED VS. BLUE. A luminous blue quasar blows
away the star-forming material (orange-red) from
its host galaxy in this artist’s concept. Over time,
quasars first clear their immediate surroundings
and then their entire galaxy of gas and dust, bring-
ing star formation to a virtual end. MICHELLE VIGEANT