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Glowing

galaxies

A tiny neutron star shines brightly.

This vivid image shows the slow

merger of the two galaxies that make

up the Whirlpool Galaxy (M51).

They both sit 23 million light-years

from Earth. The photo combines

optical imagery (appearing in blue)

from the Sloan Digital Sky Survey

with X-ray data (shown in green)

from NASA’s NuSTAR mission.

Much to astronomers’ surprise,

the supermassive black holes in the

centers of these two galaxies are not

shining as intensely in X-rays as

expected. Researchers think this may

be due to a brief dip in brightness as

the black holes “f licker” over time.

Odder still, the X-ray emission

from these behemoths is matched by

an object millions of times less mas-

sive: a single, incredibly dense neutron

star about 12 miles (20 kilometers)

across and two times the mass of the

Sun. This neutron star is situated

on the left side of the main galaxy,

where its green glow can easily be

seen. Astronomers think the neutron

star’s strong magnetic field could be

causing it to blast out high-energy

X-rays, and that the other green spots

of X-ray emission in the colliding

galaxies could also be neutron stars.

— Amber Jorgenson

PUZZLE PIECE

Neptune’s newly

discovered smallest

moon, Hippocamp,

may be a piece broken

off from the larger

moon Proteus.

TALK IT OUT

A Northwestern University

model will use data from

isolation experiments to

predict and avoid crew

communications problems

on missions to Mars.

DUSTY DISCOVERY

While searching data for

brown dwarfs, citizen

scientist Melina Thévenot

discovered the first white

dwarf surrounded by

multiple dusty rings.

NASA/JPL-CALTECH, IPAC. TOP FROM LEFT: ESA/HUBBLE, NASA, L. CALÇADA; NASA; NASA’S GODDARD SPACE FLIGHT CENTER/SCOTT WIESSINGER