My first Magazine Sky & Telescope - 04.2019 | Página 14

NEWS NOTES
EXOPLANETS
NASA’s TESS Mission Announces New Planets
ASTRONOMERS ON NASA’S Transiting
Exoplanet Survey Satellite (TESS) team
have announced the discovery of eight
confi rmed planets, as well as more than
300 exoplanet candidates.
Launched in April 2018 (S&T: Aug.
2018, p. 8), TESS began science opera-
tions last July, searching for planets
around 200,000 of the nearest stars. At
press time, the mission had monitored
six sky sectors for 27 days apiece.
LHS 3844 b
The new fi nds, presented at the
American Astronomical Society meeting
on January 7th, use only the fi rst three
months of observations. While the cata-
log paper is still forthcoming, the team
provided details on three of the smallest
confirmed planets:
q The locations of three confi rmed small plan-
ets are labeled in sections from TESS’s fi rst-
light image. (The Small and Large Magellanic
Clouds appear at left and right, respectively.)
Pi Mensae c
HD 21749 b
Pi Mensae c (S&T: Jan. 2019, p. 12)
is a super-Earth about fi ve times Earth’s
mass that circles its Sun-like star in six
days. A previously discovered gas giant
accompanies it on a highly elongated
six-year orbit.
LHS 3844 b is a hot, slightly more-
than-Earth-size planet that circles its
red dwarf star in just 11 hours.
HD 21749 b, the newest discovery,
is a sub-Neptune that’s three times
Earth’s girth but 23 times its mass. It’s
denser than Neptune, but not so much
that it’s rocky; astronomers suspect
it has a thick, heavy atmosphere. The
planet is on a 36-day orbit and was
discovered with additional transit data
from ground-based telescopes.
As Principal Investigator George
Ricker (MIT) points out, the space-
craft is in a stable orbit, its cameras are
performing beautifully, it has oodles
of propellant left, and the only mov-
ing parts are four momentum wheels
that should last decades. As long as the
mission continues to receive funding,
there’s no reason TESS can’t keep on
keeping on for at least another decade.
IN BRIEF
Most Distant Solar System
Object Discovered
Nicknamed “Farout,” the object provisionally
designated 2018 VG 18 currently orbits the Sun
somewhere between 115 and 125 astronomi-
cal units. That’s more than three times farther
out than Pluto is, on average, and more
distant than any other objects known. Scott
Sheppard and colleagues discovered the ob-
ject in November using the Subaru telescope
in Hawai‘i. Graduate student Will Oldroyd
(Northern Arizona University) joined the team
in early December for further observations
using one of the Magellan telescopes in Chile.
The additional images enabled the scientists
to measure the object’s motion against back-
ground stars, giving its distance. The team
found Farout as part of their ongoing search
for Planet X, an as-yet undetected world
thought to be shaping the orbits of several
distant solar system objects (S&T: Oct. 2017,
p. 16). However, depending on the shape of
Farout’s orbit, it could take another one to
three years of observations before the team
nails down its orbital parameters and deter-
12
A PR I L 2 019 • SK Y & TELESCOPE
mines whether it, too, has been infl uenced by
the putative Planet X.
■ MONICA YOUNG
M77 Supernova Discovered
On November 24th the DLT40 survey, con-
ducted with a 0.4-meter telescope in Chile,
picked up a 15.4-magnitude supernova in
M77, a bright, barred spiral galaxy in Cetus.
Designated 2018ivc, the new supernova
brightened only briefl y; intervening dust
dimmed and reddened its light. It fi rst ap-
peared as a tiny pinprick of light 8.7” east and
16.1” north of the center of the galaxy along
the edge of the bright inner disk. Spectros-
copy revealed a Type II supernova, whose
blast sent debris fl ying outward at some
13,500 km/s (30.2 million mph). This is the
fi rst recorded supernova in M77.
■ BOB KING
White Dwarfs’ Crystal Cores
White dwarfs face a crystallized fate, as-
tronomers report in the January 10th Nature.
When the European Space Agency’s Gaia
satellite revealed precise distances, and
thus luminosities, to 1.7 billion stars last year
(S&T: Aug. 2018, p. 9), it also measured these
properties for 200,000 white dwarfs — a
thousandfold increase compared to what was
previously available. Pier-Emmanuel Tremblay
(University of Warwick, UK) and colleagues
placed 15,000 of the nearest white dwarfs on
a diagram that plots magnitude against color,
which serves as a proxy for temperature.
The white dwarfs fall exactly where certain
evolutionary models had predicted. These
models suggest that, as white dwarfs cool,
their cores experience a phase transition.
When white dwarfs fi rst form, they pack so
much matter into so small a space that the
atomic nuclei join together into a kind of
fl uid, while the electrons become unbound
into a gaseous haze. But once white dwarfs
cool below 10 million degrees, the nuclei fl uid
solidifi es. Moreover, the nuclei release heat
as they settle into an ordered structure, so
the crystallization actually delays the white
dwarf’s overall cooling. Cooling resumes
once the core is fully solid. Based on these
fi ndings, Tremblay predicts that the Sun will
crystallize, too, in about 10 billion years’ time.
■ MONICA YOUNG
■ MONICA YOUNG