Sky & Telescope - July 2024 - 58

WILLIAM PENDRILL
JULY 2024 OBSERVING
Pro-Am Conjunction by Diana Hannikainen
Cool
Neighbors
Help astronomers find
challenging dim objects.
Y
ou may have heard the phrase
" failed star. " It's a term often bandied
about for brown dwarfs, a class of
object intermediate to planets and stars.
But brown dwarfs represent much more
than their moniker implies, as they hold
clues to the evolutionary histories of
both planets and stars.
Cool Neighbors. Brown dwarfs are
much less massive than regular, mainsequence
stars, weighing in at 1% to 8%
the mass of the Sun. In planetary terms,
that's around 10 to 80 Jupiters. They're
not massive enough to sustain nuclear
fusion in their cores (hence their nickname),
but they do emanate a pale infrared
glow thanks to residual heat from
their formation process. All this means
that they're generally cooler and smaller
than regular stars, making these dim
targets extremely challenging to find.
Nevertheless, astronomers persist at
seeking them out for a variety of reasons.
One is that brown dwarfs can give
us insights into exoplanets. Their atmospheres
exhibit signatures of water and
methane, compounds that are also present
in gas-giant exoplanets. But there's
one rather vexing feature of exoplanets:
They orbit blindingly bright host stars.
Brown dwarfs, on the other hand, often
wander through space alone, their feeble
light not drowned out by a companion.
So, by studying the chemical composition
of large numbers of brown dwarfs,
researchers may gain insight into exoplanets.
(See S&T: Mar. 2022, p. 34.)
Astronomers identified the first
brown dwarf in the 1990s and have
58 JULY 2024 * SKY & TELESCOPE
BIG THINGS COME IN SMALL PACKAGES Brown dwarfs may be small and dim, but
they pack a punch when it comes to the information they provide on the evolutionary
processes of both stars and exoplanets.
subsequently found a few thousand, but
there should be many more lurking out
there. Space missions - such as NASA's
Wide-field Infrared Survey Explorer
(WISE), which received a second lease
on life as the near-Earth object hunter
NEOWISE - are spewing out reams
of data that may contain the imprints
of these elusive targets. Professional
astronomers are turning to you for help
mining this mother lode via a Zooniverse
project called Backyard Worlds:
Cool Neighbors.
From the comfort of your desk.
Because brown dwarfs are so dim, the
only ones we have hopes of detecting
are those that are relatively close to our
solar system. Their apparent motion in
space should stand out against the more
distant background stars (see, e.g., S&T:
Dec. 2023, p. 74). So to find them, you
can employ the same technique that
Clyde Tombaugh used to discover Pluto
in 1930: Compare images of the same
field of sky taken at different times and
see if anything moved.
Getting involved is easy: Head to
the project homepage (https://is.gd/
cool_neighbors), click on the " Classify "
button at top right, and you're good to
go! (Do also take a look at their tutorial,
though, for helpful tips.) Amateur
Dan Caselden, co-investigator of Cool
Neighbors, says, " It's a simple yes-orno
process - either you see something
move, in which case you hit YES, or you
don't, and you hit NO. "
What happens if you think you
stumble upon what's known in the
lingo as a mover? First thing to do is to
crosscheck with SIMBAD (https://is.gd/
astro_simbad), the go-to database for
professional and amateur astronomers
alike. If you find your target listed, move
on to the next field in the project. If your
target isn't listed, upload your info -
and get excited. (But not too excited: The
research team has to verify that your
finding is indeed a brown dwarf and not
an artifact.) Don't despair if you don't
find anything the first few tries - or
even tens of tries. Cool Neighbors' excellent
FAQ page notes that it takes about
60 tries to spot a known object and a wee
while longer for something unknown.
Caselden himself has reported hundreds
of discoveries, some still awaiting
confirmation. He urges you to give it a
try: " You'll be working with a lovely and
inspiring community, and you'll contribute
directly to science. " He would know:
Caselden won this year's AAS Chambliss
Amateur Achievement Award thanks to
his work with Backyard Worlds.
¢ Observing Editor DIANA HANNIKAINEN
is delighted brown dwarfs are getting the
attention they deserve.
https://is.gd/astro_simbad https://is.gd/astro_simbad https://is.gd/cool_neighbors https://is.gd/cool_neighbors
Sky & Telescope - July 2024

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