Sky and Telescope - May 2018 - 9

STARS

EXOPLANETS

Hefty Stars Prompt
Birth Debate

Some Planets Are Bigger
Than They Appear

A NEW STUDY FOUND more mas-

ized that the nebula had given birth
to some behemoths: The birth weight
of the largest star they observed was
equivalent to 200 Suns, notably larger
than previous observations, which had
suggested that stars aren't born with
more than 150 Suns' worth of mass.
It could be that the nebula's conditions allow relatively more massive
stars to form. However, to prove that
star formation really isn't universal,
the team will have to replicate these
same methods in other regions, cautions Nathan Bastian (Liverpool John
Moores University, UK).

NEARBY STARS CAN MAKE some
exoplanet candidates look smaller than
they really are, Carl Ziegler (University of North Carolina, Chapel Hill)
reported at the American Astronomical Society meeting in Washington,
D.C. The results come from the RoboAO system, which is following up on
some 4,000 candidate exoplanets from
NASA's Kepler mission. The automated
laser-guided adaptive optics system took
rapid-ﬁre images of each target star,
looking for stellar companions that
might muck up the data.
Of 3,857 stars observed with RoboAO, almost 600 had stellar companions.
The extra stars' light contaminated
exoplanet transits, making their dips
appear smaller and thus giving the
impression that the planets themselves
are smaller. Generally, having another
star in the system makes planets twice
as wide as they ﬁrst appear. Because of
this contamination, 8 of the 26 potentially rocky, habitable-zone worlds studied might actually be gaseous. Among
them are the conﬁrmed planets Kepler438b and Kepler-437b, which could be 2
to 3 times larger than estimated if they
orbit their system's secondary star.

■ MONICA YOUNG

■ CAMILLE M. CARLISLE

sive stars than expected in an intense
region of star-formation, begging the
question: Does the process of star formation always happen the same way?
As gas clouds collapse into stars,
they fragment, producing many
smaller stars and only a few bigger
ones. Astronomers have long debated
what factors might affect this process.
The Tarantula Nebula (30 Doradus) is the perfect testing ground. The
windswept hub of giant stars-to-be is
located more than 160,000 light-years
away in the Large Magellanic Cloud,
where conditions mimic those of the
universe's early years.
Fabian Schneider (University of
Oxford, UK) and colleagues used the
FLAMES spectrograph on the Very
Large Telescope in Chile to collect
spectra for 800 of the nebula's stars.
The team then calculated the region's
initial mass function based on 247
single stars with at least 15 times the
Sun's mass. The results appear in the
January 5th Science.
To their surprise, Schneider and
colleagues found more massive stars
relative to low-mass stars than standard formulas predict. They also real-

p Schneider's team studied the bright, central
regions of the Tarantula Nebula.

TA R A N T UL A NEBUL A: ESO / R. FOSBURY (ST-ECF );
V EN US: JA X A / ISAS / DA RTS / DA MIA BOUIC

Akatsuki's Views of Venus
Japan's Venus-bound orbiter Akatsuki survived great odds to reach its objective and is now wowing scientists with results. Akatsuki has been at Venus since
December 2015, and in its ﬁnal science orbit since April 4, 2016. The very elliptical orbit has a period of 10.5 days, traveling from a closest approach of around
10,000 km (6,000 mi) to its farthest point 360,000 km (220,000 mi) from the planet.
Akatsuki carries ﬁve cameras to view Venus in different wavelengths, each one
penetrating into Venus's atmosphere to a different depth. Unfortunately, its two
infrared cameras suffered an electrical fault in December 2016, but three cameras capturing ultraviolet, visible, and long-infrared wavelengths still function.
The ultraviolet imager (UVI) records high-altitude clouds illuminated by sunlight,
as pictured here. Drifting along at elevations of 65 to 75 km, these clouds consist
mostly of sulfuric acid. Amateur image processor Damia Bouic combined UVI images taken from different distances to create this composite. Read more and see
additional stunning images at https://is.gd/Akatsukiviews.
■ EMILY LAKDAWALLA

s k y a n d t e l e s c o p e . c o m * M AY 2 0 1 8

https://www.is.gd/Akatsukiviews http://www.skyandtelescope.com

Sky and Telescope - May 2018

Table of Contents for the Digital Edition of Sky and Telescope - May 2018