Page 19 - Astronomy - October 2017 USA

ASTRONEWS DEATH BLOW. Using data from LIGO, Rochester Institute of Technology researchers have determined that an exploding
star may give the resulting black hole a “kick” that affects its alignment in space.

Enceladus’ odd tilt from an ancient collision?

Equator
NASA/JPL-CALTECH/SPACE SCIENCE INSTITUTE/CORNELL UNIVERSITY

Tiger
stripes

Tiger stripes
Original south pole Current south pole

POLAR WANDERER. Enceladus’ “tiger stripes” are geological scars normally associated with equatorial
regions. The left-hand image depicts what may have been the moon’s original orientation, while the right-
hand image shows how the moon’s tilt has dramatically changed likely due to a large asteroid impact.
Saturn’s oddball moon Enceladus may be a equator, shifting that region toward the cur-
jumbled mess, according to research pub- rent south pole. Incidentally, that’s where the
lished April 30 in Icarus. moon’s geysers are most active. Enceladus
Researchers at Cornell University, NASA, has an ocean underneath its ice crust that fre-
and the University of Texas say the poles of quently spurts water into space.
the moon are about 55 degrees off from The initial aftermath of the collision would
where they should be. The telltale signs of have left Enceladus without a stable axis,
this misalignment are a group of basins form- instead chaotically wobbling around for a time.
ing a rough line across the moon’s surface The moon would have resettled after about a
that would be expected at its equator — million years with an entirely new orientation.
except this chain is currently far off from the Such a collision may also explain why the
current equator as defined by its spin. moon’s south pole is rife with geological
This means something changed Enceladus’ activity, while its north pole is relatively inert.
tilt, likely an asteroid striking near the moon’s — J. W.

All stars may be born in pairs

The Perseus molecular cloud may be reveal-
ESO ing a strange truth about the universe: Most
Three for the stars, if not all, are born in pairs. This means
that the Sun could have lost a companion
price of one that’s somewhere out there — and it may be
one of several known stars.
All stars form in molecular clouds, such as
SEEING TRIPLE. The European Southern the one in Perseus. Radio observations of the
Observatory snapped this 3-gigapixel picture of area showed many of its stars are forming in
(bottom to top) the Omega Nebula, the Eagle Nebula, multiple-star systems. Models based on the
and a gas cloud called Sharpless 2–54. The objects are data further showed that the conditions BILL SAXTON, ALMA (ESO/NAOJ/NRAO), NRAO/AUI/NSF
all about 7,000 light-years away and may have formed inside the cloud could be reproduced only if
from the same primordial gas clouds. Each has since all the stars were originally born in pairs.
become an area of star formation. The Eagle Nebula Protostars have been observed to form in
is home to the so-called “Pillars of Creation,” a star egg-shaped cores within larger molecular
forming region that is one of the most famous images clouds. The models based on the Perseus
taken with the Hubble Space Telescope. — J. W. molecular cloud show that these cores tend MISSING SIBLING. ALMA captured this radio
to form two concentrations of mass as they image of a multiple-star system forming inside
collapse, and thus two stars rather than one. the Perseus molecular cloud. Modeling based on
So why doesn’t the Sun have a binary com-
observations of the cloud indicates that all stars
20 years panion (well, depending on whom you ask)? It may be born in systems of two or more stars.
seems that 60 percent of stars lose their
binary sister over time, gaining a wider dis- The authors of the paper, published in the
How long the United States tance from their partner until they are gravita- Monthly Notices of the Royal Astronomical
tionally severed. The pairs that form also may Society, say more work is needed to confirm
has been continually operating not include two objects with similar masses, their hypothesis. But if it’s true, the hunt may
spacecraft on or around Mars. meaning that some former companions could be on for the companion the Sun once had.
be brown dwarfs cast out by larger stars. — J. W.

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