Sky and Telescope - July 2016 - 12

News Notes

GALAXIES I Rare Super Spirals Discovered
ies to a couple hundred and discovered
that, although most were ellipticals, 53
were super spirals.
Given the small number found, these
giants are clearly rare. Astronomers don't
know how they're created. Four of the 53
galaxies look like they're midway through
merging with another galaxy, and at
least 10 seem to be in clusters or groups.
But the others look fairly isolated. So it's
unclear if super spirals form via mergers or via cosmic pipelines of cold gas
that would feed the growing disk from
the inside out (S&T: Sept. 2015, p. 16).
Astronomers will need to study how star
formation and neutral gas are distributed
in the spirals in order to narrow in on the
origins, the team suggests in the February 1st Astrophysical Journal.
It's curious that the galaxies are forming so many stars so recently in cosmic
history. Galaxies this massive would
normally be well on the way to becoming
"red and dead." Somehow, super spirals
managed not to choke oﬀ or heat up the
cold gas supplies they need in order to
make stars.

Navy Resumes Celestial Navigation
Course. In response to modern security
threats, the U.S. Naval Academy in Annapolis,
Maryland, has resumed training oﬃcers in
the lost art of celestial navigation. Although
this training used to be required, the advent
of GPS technology led the Navy ROTC to end
it in 2000, and the academy phased it out as
well in 2006. But commercial GPS jammers
are now readily available on the internet -
and attacks, space debris, or solar storms
could knock out GPS satellites. So the academy brought back celestial-navigation theory
for its 2015 summer session. The class of 2017
will be the ﬁrst in more than a decade with
basic instruction in "shooting the stars."

verse just 400 million years old (in astrospeak,
at a redshift, z, of 11.1, which refers to how
much the universe's expansion has shifted
the galaxy's spectra). The previous record
holder was MACS0647-JD at 435 million years
after the Big Bang (z = 10.7), but its redshift
is not as precisely measured. Although the
universe didn't start forming stars until it was
about 100 million years old, GN-z11 already
holds a billion Suns' worth of mass in its
stars. It's churning out even more at a rate
between 14 and 34 solar masses per year.
Thanks to all those suns, GN-z11 is incredibly
luminous, radiating three times the amount of
ultraviolet light typical of galaxies in this early
era, Pascal Oesch (Yale) and others report in
the March 10th Astrophysical Journal.

■ DAVID DICKINSON

■ MONICA YOUNG

Hubble Finds Most Distant Galaxy Yet.
Astronomers have found a humdinger of a
galaxy dubbed GN-z11, which dwells in a uni-

Planet in the Hyades. Professional and
amateur astronomers perusing K2 observations have found a young, Neptune-size

planet in the Hyades open cluster. What's
interesting about the world, called K2-25b,
is its size: 10% the width of its parent star,
a spotty, red M dwarf. No other planet has
been found around an M dwarf that's so
comparably large, Andrew Mann (University
of Texas at Austin) and colleagues report
in the February 10th Astrophysical Journal.
The planet might be puﬀed up and losing its
primordial atmosphere due to the radiation
pouring out of the young, active star, which
is 650 to 800 million years old. Astronomers
will need two pieces of information to check
this theory: the planet's mass (instruments
that could detect it are now coming online,
Mann says), and whether planets in other
young systems are also abnormally large.
The repurposed Kepler spacecraft has also
observed the Pleiades and Praesepe (a.k.a.
Beehive) open clusters, so hopefully more
worlds will turn up in the data.

SDSS

ellipticals, gargantuan football-shaped
collections of old stars. But Patrick
Ogle (Caltech) and his team have found
distant spirals that are bigger, brighter,
and starbirthing-mightier than expected
from their nearby brethren. These
newfound galaxies, which the team calls
superlumious spirals or "super spirals"
for short, have disks between 180,000
and 440,000 light-years wide, and they're
churning out stars at a rate of 5 to 65
solar masses each year. For comparison,
the Milky Way's disk spans roughly
100,000 light-years, and each year it produces merely the equivalent of one Sun's
mass in new stars.
Team members sorted through the
NASA/IPAC Extragalactic Database to
see what kind of big-picture insights they
could glean from its archive. They picked
out 1,616 galaxies with redshifts less
than 0.3 (meaning the light we see left
them less than 3.5 billion years ago) and
luminosities more than eight times that
of the Milky Way. Through a process of
"how much/what kind of data do we have
on this galaxy" elimination, the team
whittled down the group of bright galax-

The super spiral designated 2MASX
J16014061+2718161 is the brightest galaxy in a
galaxy cluster and appears here with other disk
galaxy companions (smaller blue smudges).

Astronomers have identiﬁed 53 "super
spirals" - spiral galaxies that are huge
and incredibly luminous - as part of a
project exploring archived observations.
Across the cosmos the biggest, brightest galaxies are usually not spirals but

IN BRIEF

12

July 2016 sky & telescope

■ CAMILLE M. CARLISLE

■ CAMILLE M. CARLISLE
Sky and Telescope - July 2016

Table of Contents for the Digital Edition of Sky and Telescope - July 2016
