Page 12 - Astronomy - October 2017 USA

ASTRONEWS RULED OUT. Physicists looking to explain the cosmic inflation that happened shortly after the Big Bang have ruled out
the presence of the light inflaton, a particle with properties similar to the Higgs boson but a lower mass.

HUBBLE WEIGHS A WHITE DWARF BRIEFCASE

COSMIC MAGNIFYING GLASS
limit (1.4 solar masses), it will explode as a A team led by James Lowenthal of Smith College has
supernova, which astronomers can use to discovered that gravitational lensing may be respon-
accurately measure distances. If our under- sible for the brightest galaxies in the sky. Of a sample
of 31 of the brightest galaxies at infrared wave-
standing of the relationship is incorrect, it
lengths, 11 have been observed with the Hubble
would affect the distances calculated. Space Telescope. All of them are gravitationally
Only three other white dwarfs have been lensed star-forming galaxies seen 8 billion to 11.5 bil-
lion years ago birthing stars at a rate 1,000 or more
weighed, but their masses were measured
times that of the Milky Way. Despite the distorted
via their gravitational effects on a binary images created by the lenses, the team can use these
companion. The masses derived for white new, clearer images to reconstruct the galaxies and
dwarfs in binary systems could be affected better understand their high rates of star formation.
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by a process called mass transfer between
NOT QUITE NEIGHBORS. The white dwarf the stars, which would contaminate the OUR LOCAL VOID
Stein 2051B (bright central object) can be seen Researchers at the University of Wisconsin–Madison
superimposed on the sky with a background star mass-radius relationship. Although Stein have discovered evidence that the Milky Way and its
(lower left), whose light was bent by the white dwarf 2051B has a binary companion, it’s so far Local Group may exist inside a large void. A local void
could explain the “tension” currently observed in the
passing in front of it. NASA, ESA, AND K. SAHU (STSCI) away — at least 5 billion miles (8 billion
Hubble constant, which measures how fast the uni-
km) — that the two cannot exchange mass. verse is expanding. The effects of this void, and the
A bowling ball depressing a mattress, Sahu’s team plotted it on the white dwarf ferent values observed when measuring the Hubble
ccording to the theory of general rela-
Once the mass of 2051B was measured,
pull of the mass beyond it, might contribute to dif-
tivity, mass bends space-time like a
constant using nearby versus faraway indicators.
mass-radius relation. Their result fit per-
•
causing light to follow a curved path.
fectly with the model. “When I saw that it MOLECULAR BLACK HOLE
In 1919, Sir Arthur Eddington measured
was right exactly on here, I almost fell off Scientists unexpectedly generated a “black hole” in a
the deflection of background stars caused lab using X-ray pulses. Using the Linac Coherent
my chair,” Sahu explained.
by our Sun during a total solar eclipse. Stein 2051B’s excellent fit confirms our Light Source (LCLS) X-ray free-electron laser at the
SLAC National Accelerator Laboratory, researchers
Nearly a century later, astronomers have current evolutionary theory of white dwarfs stripped iodine atoms of their electrons with a burst
used the Hubble Space Telescope (HST) to and agrees with our understanding of the of concentrated energy (100 quadrillion kilowatts per
observe this effect caused by a star outside matter that makes up these objects. “This is cubic centimeter). As a result, the iodine atoms
our solar system for the first time. really a confirmation of the theory that we began pulling in electrons from surrounding atoms.
Kailash Sahu of the Space Telescope have been using so far,” Sahu said. This is similar to the forces at work in a black hole,
though these objects exhibit a gravitational pull
Science Institute announced the result at instead of electromagnetic attraction. — J. W., A. K.
— Alison Klesman
the 230th Meeting of the American
Astronomical Society. Sahu’s team used the
HST to capture the deflection of light from 70 The number of Jupiter masses an object
a background star as a white dwarf, the needs to ignite hydrogen fusion as a star.
remnant of a star once like our Sun, passed
in front of it.
Although this deflection was about 1,000 FIRE IN THE SKY The largest fireball occurred above FAST
times smaller than the one Eddington mea- Chelyabinsk, Russia, on February 15, 2013, FACT
and released about 440 kilotons of energy.
sured, Hubble’s precision allowed astrono-
mers to see it clearly. From the deflection,
they were able to measure the mass of the
white dwarf, Stein 2051B. The work
appeared in the June 7 issue of Science.
Stein 2051B is 17 light-years away. In
March 2015, it passed in front of a star
5,000 light-years distant, causing its light to
bend by 2 milliarcseconds. Seeing that bend ASTRONOMY: ROEN KELLY, AFTER ALAN B. CHAMBERLIN (JPL/CALTECH)
was like trying to watch an insect crawl
across the face of a quarter from a distance
of about 1,500 miles (2,400 kilometers).
This is the first time a deflection due to
general relativity has been measured using
a star other than our Sun. And measuring
the mass of Stein 2051B is the first “clean SKYLIGHT. Astronomers define a fireball as any Impact energy (kilotons)
meteor brighter than magnitude –3. For the past
test for [the] mass-radius relationship,” three decades, U.S. government sensors have been
Sahu explained. recording such events across the globe. Although 0.1 1 10 100
The mass-radius relationship for white the network doesn’t record every fireball, it gives
a good picture of the pummeling Earth receives from solar system debris. This chart depicts the brightest
dwarfs leads to the Chandrasekhar limit. If events from April 15, 1988, to June 20, 2017; the relative size and color of each circle represents the fireball’s
a white dwarf accumulates mass over this estimated total impact energy. — Richard Talcott
12 ASTRONOMY • OCTOBER 2017