Astronomy - September 2015

ASTRONEWS

ASTRONEWS

ASTROCONFIDENTIAL BY KARRI FERRON

Nanoflares are spontaneous solar heating

bursts that each reach some 18 million

degrees F (10 million degrees C).

FAST

FACT

20 ASTRONOMY • SEPTEMBER 2015

EATING HABITS. Astronomers read galaxy NGC 1512’s past eating habits in the processed clumps of gas scattered

across its face, material that it must have absorbed from other smaller galaxies.

WHAT HEATS THE SUN’S OUTER ATMOSPHERE?

At several million kelvins, the Sun’s outer

atmosphere, called the corona, is a thousand

times hotter than the underlying solar sur-

face. Understanding what heats the corona

to its extreme temperatures is one of the

cornerstone questions in space science. New

evidence has revealed that coronal heating

takes the form of impulsive energy bursts

called nanof lares. Although puny by solar

standards, each one is the equivalent of a

50-megaton hydrogen bomb, the largest ever

detonated on Earth. Millions of nanoflares

occur every second across the Sun, and

together they pack a real wallop.

Nanoflares have been difficult to study

because we are unable to observe individual

occurrences. Even with the resolution of our

most powerful telescopes, we are stuck see-

ing multiple overlapping events along the

line of sight. As a consequence, progress has

had to rely on a combination of observa-

tions and theoretical modeling. By compar-

ing what we see with what we expect to see

based on computer simulations,

we can infer the properties of the

energy release. Recently, we have

detected faint emission from super-

hot plasma (highly ionized gas).

This only can be produced by nanoflares,

and we consider it to be the “smoking gun.”

So, what is a nanof lare? That’s still an

open question, but the most likely expla-

nation is that it represents the sudden

breaking of stressed magnetic fields that

extend upward from the solar surface and

permeate the corona. Turbulent motions

at the surface cause the coronal fields to

become tangled and twisted much like rub-

ber bands. Eventually, the fields break and

release bursts of energy — nanof lares — in

a process called magnetic reconnection. It

is at the heart of many different phenomena

occurring throughout the solar system and

the universe. By studying nanof lares, we

hope to learn more about these other phe-

nomena as well.

NASA’s next Mars lander readies for launch

The hunt for major cosmic game is on. And

while scientists have spent a century seeking

the gravitational waves that Albert Einstein first

predicted as a consequence of his general theory

of relativity, this time could be different. In May,

the Laser Interferometer Gravitational-wave

Observatories (LIGO) finished a seven-year

upgrade that increases its sensitivity tenfold.

Astronomers expect these ripples in the fabric of

space-time are created during violent events like

supernova explosions and colliding black holes.

Their hope is to one day use gravitational waves

to unravel new details of the cosmos’ most vio-

lent events. First they have to find them. — E. B.

LIGO ramps up search

for gravitational waves

James A. Klimchuk

Astrophysicist in the Heliophysics Division

at NASA Goddard Space Flight Center,

Greenbelt, Maryland

COURTESY JAMES A. KLIMCHUK

NASA/JPL-CALTECH/LOCKHEED MARTIN

BEST PRACTICE. This is how NASA’s next Mars lander, InSight, will look when it deploys on the Red Planet’s

surface one year from now and begins to study its crust, mantle, and core for the first time. Lockheed Martin

Space Systems in Denver has finished building the spacecraft and moved on to the final testing phase ahead

of the March 2016 launch. InSight deployed its solar panels during tests April 30, and engineers entered a

seven-month environmental testing phase that will expose the car-sized craft to space-like hazards. NASA also

announced plans to deploy CubeSats as InSight enters orbit at Mars and use the tiny instruments to observe

the landing. If it succeeds, the lander could help tell astronomers how rocky planets form. — E. B.

GRAVITY LAB. Physicists have put Einstein to the

test for more than a century, and yet general relativ-

ity’s gravity waves remain unconfirmed. LIGO hopes

to change that beginning this fall. LIGO LABORATORY