Page 17 - Astronomy - October 2017 USA

ASTRONEWS RADIATION WARNING. NASA’s Human Research Program is studying simulated space radiation to determine
the long-term effects of space flight on astronauts’ health in preparation for manned missions to Mars.

Juno’s early results reveal a mysterious Jupiter

Since arriving at Jupiter on July 4, atmosphere, while bands at other
2016, the Juno spacecraft has latitudes spawn additional atmo-
been showing planetary scientists spheric structures.
a brand-new view of the planet, Juno revealed a magnetic field
including a deeply turbulent 10 times stronger than any on
atmosphere and a “lumpy” mag- Earth, varying in strength across
netic field. the planet. “This uneven distribu-
“It was a long trip to get to tion suggests that the field might
Jupiter, but these first results be generated by dynamo action
already demonstrate it was closer to the surface, above the
well worth the journey,” said layer of metallic hydrogen,” said
Diane Brown, a Juno program Jack Connerney, the mission’s
executive at NASA’s Washington deputy principal investigator and
Headquarters, in a May press leader of the probe’s magnetic
release. The results from Juno’s field investigation at NASA’s
first data-collection pass of the Goddard Space Flight Center.
planet — at an altitude of 2,600 “We knew, going in, that Jupiter
miles (4,200 kilometers) on would throw us some curves,” said
August 27, 2016 — were recently Scott Bolton, Juno principal inves-
published in Science and tigator from the Southwest NASA/JPL-CALTECH/SwRI/MSSS/GERALD EICHSTÄDT/SEÁN DORAN
Geophysical Research Letters. Research Institute in San Antonio.
Those results include images “But now that we are here, we are
from JunoCam, which showed finding that Jupiter can throw the
Earth-sized storms clustered at heat, as well as knuckleballs and
the planet’s north and south sliders. There is so much going on
poles. Data from the Microwave here that we didn’t expect that we
Radiometer demonstrated that have had to take a step back and LIGHT AND DARK. Jupiter’s atmosphere contains numerous bands and belts;
Jupiter’s equatorial belt pene- begin to rethink of this as a whole each band in this JunoCam image is wider than Earth. Three white, oval-shaped
trates deep into the planet’s new Jupiter.” — A. K. storms are visible, part of the planet’s “String of Pearls.”
4,034 The number of potential exoplanets currently identified

using data from the Kepler spacecraft.

EXPLOSIVE END. Though there are many subclasses, supernovae fall into
two general types: massive stars reaching the end of their lives (type II) and
white dwarfs accreting more matter than they can physically support (type Ia).
Type II supernovae are responsible for distributing heavy elements throughout
the cosmos; type Ia supernovae are “standard candles” used to accurately
measure distances to very distant galaxies, thereby determining the expansion
rate (and acceleration) of the universe. — A. K. White dwarfs are themselves remnants of Sun-like stars
(<8 M ) that did not explode upon death. If a white
Sun
dwarf has a binary companion, it can pull material off
this nearby star and grow until a critical mass (called
the Chandrasekhar limit, about 1.4 M Sun ) is reached.
This triggers a runaway nuclear reaction that tears
the white dwarf apart, causing a type Ia supernova.

Because type Ia supernovae
Alternatively, type Ia supernovae may always occur at roughly the
During a massive star’s (≥8 M Sun ) lifetime, pressure generated by fusion processes occur when two white dwarfs in a binary same mass (1.4 M Sun ), they
hold the core up. As fusion slows, the pressure diminishes and the core shrinks. system spiral inward (left) and eventually have the same intrinsic
Eventually, the material inside the core reaches a critical point, triggering a recoil merge (right). If the resulting object is brightness and the observed ASTRONOMY: ROEN KELLY
effect. The resulting explosive shock wave tears through the star’s outer layers. greater than the Chandrasekhar limit, it brightness can be used to
Stars of any mass greater than 8 M Sun can cause a type II supernova, so these will also explode in a type Ia supernova. calculate distance.
events vary greatly in brightness.
Supernova 1987A is one of the most famous modern supernovae. This FAST
type II supernova had a progenitor about 18 times the mass of our Sun. FACT
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