NEXT MARS ROVER WILL HAVE 23 EYES
NASA
When the Mars Pathfinder touched down in 1997, it had five cameras: two
on a mast that popped up from the lander, and three on NASA's first
rover, Sojourner. Since then, camera technology has seen appreciable
improvement. Photo-sensors that were improved by the space programme
have become commercially ubiquitous. Cameras have shrunk in size,
increased in quality and are now carried in every cellphone and laptop.
That same evolution has returned to space. The Mars 2020 mission will
have more 'eyes' than any rover before it -- a grand total of 23, to
create sweeping panoramas, reveal obstacles, study the atmosphere, and
assist instruments. They will provide dramatic views during the rover's
descent to Mars and be the first to capture images of a parachute as it
opens in the atmosphere of another planet. There will even be a camera
inside the rover's body, which will study samples as they are stored and
left on the surface for collection by a future mission. They represent
a steady progression since Pathfinder: after that mission, the Spirit
and Opportunity rovers were designed with 10 cameras each, including on
their landers; Mars Science Laboratory's Curiosity rover has 17. Camera
technology keeps improving; each successive mission is able to utilize
the improvements, with better performance and lower cost. The cameras
on Mars 2020 will include more colour and 3-D imaging than on Curiosity.
On the new rover, the engineering cameras have been upgraded to acquire
high-resolution, 20-megapixel colour images.
COLD DUST AROUND NEAREST STAR
ESO
The ALMA Observatory in Chile has detected dust around the closest star
to the Solar System, Proxima Centauri. The new observations reveal the
glow coming from cold dust in a region from one to four times as far
from Proxima Centauri as the Earth is from the Sun. The data also hint
at the presence of an even cooler outer dust belt and may indicate the
presence of an elaborate planetary system. Those structures are similar
to the much larger belts in the Solar System, and are expected to be
made from particles of rock and ice that failed to form planets.
Proxima Centauri is the closest star to the Sun. It is a faint red
dwarf lying just four light-years away in the southern constellation
Centaurus. It is orbited by the Earth-sized temperate world Proxima b,
discovered in 2016 and the closest planet to the Solar System. But
there is more to this system than just a single planet. The new ALMA
observations reveal emission from clouds of cold cosmic dust surrounding
the star. The dust around Proxima is important because, following the
discovery of the terrestrial-type planet Proxima b, it is the first
indication of the presence of an elaborate planetary system, and not
just a single planet, around the star closest to the Sun. Dust belts
are the remains of material that did not form into larger bodies such as
planets. The particles of rock and ice in the belts vary in size from a
tiny dust grain, smaller than a millimetre across, up to asteroid-like
bodies many kilometres in diameter.
Dust appears to lie in a belt that extends a few hundred million kilo-
metres from Proxima Centauri and has a total mass of about one hundredth
of the Earth's mass. The belt is estimated to have a temperature of
about -230 degrees Celsius, as cold as that of the Kuiper Belt in the
outer Solar System. There are also hints in the ALMA data of another
belt of even colder dust about ten times further out. If the outer belt
is confirmed, its nature is intriguing, given its very cold environment
far from a star that is cooler and fainter than the Sun. Both belts
are much further from Proxima Centauri than the planet Proxima b, which
orbits just four million kilometres from its parent star. That suggests
that Proxima Centauri may have a multiple planet system with a rich
history of interactions that resulted in the formation of a dust belt.
Further study may also provide information that might point to the
locations of as-yet-unidentified additional planets. Proxima Centauri's
planetary system is also particularly interesting because there are
plans -- the Starshot project -- for future direct exploration of the
system with microprobes attached to laser-driven sails. A knowledge of
the dust environment around the star would be needed for planning such a
mission.
CLOSEST TEMPERATE WORLD ORBITING QUIET STAR
ESO
A team working with the High-Accuracy Radial-velocity Planet Searcher
(HARPS) at the La Silla Observatory in Chile has found that the red
dwarf star Ross 128 is orbited by a low-mass exoplanet every 9.9 days.
That Earth-sized world is expected to be temperate, with a surface
temperature that may also be close to that of the Earth. Ross 128 is
the 'quietest' nearby star to host such a temperate exoplanet. Red
dwarfs are some of the coolest, faintest -- and most common -- stars
in the Universe. That makes them very good targets in the search for
exoplanets, so they are increasingly being studied. In fact, it is
easier to detect small cool analogues of the Earth around such stars
than around stars more similar to the Sun. Many red dwarf stars,
including Proxima Centauri, are subject to flares that occasionally
bathe their orbiting planets in deadly ultraviolet and X-ray radiation.
However, it seems that Ross 128 is a much quieter star, and so its
planets may be the closest known comfortable abode for possible life.
Although it is currently 11 light-years from the Earth, Ross 128 is
moving towards us and is expected to become our nearest stellar
neighbour in just 79 000 years -- a blink of the eye in cosmic terms.
Ross 128b will by then have taken the crown from Proxima b and become
the closest exoplanet to the Earth.
With the data from HARPS, the team found that Ross 128b orbits 20
times closer to its star than the Earth orbits the Sun. Despite that
proximity, Ross 128b receives only 1.38 times more radiation than the
Earth. As a result, Ross 128b's equilibrium temperature is estimated
to lie between -60 and 20C, thanks to the cool and faint nature of its
small red-dwarf host star, which has just over half the surface
temperature of the Sun. While the scientists involved in this discovery
consider Ross 128b to be a temperate planet, uncertainty remains as to
whether the planet lies inside, outside, or on the cusp of the habitable
zone, where liquid water may exist on a planet's surface. Astronomers
are now detecting more and more temperate exoplanets, and the next stage
will be to study their atmospheres, composition and chemistry in more
detail. Vitally, the detection of biomarkers such as oxygen in the very
closest exoplanet atmospheres will be an important next step, which
ESO's Extremely Large Telescope (ELT) is in the prime position to take.
RED GIANT STAR GIVES GLIMPSE OF SUN'S FUTURE
Chalmers University of Technology
A team of astronomers has used the telescope ALMA (Atacama Large
Millimetre/submillimetre Array) to make the sharpest observations yet
of a star with the same initial mass as the Sun. The new images show
for the first time details on the surface of the red giant W Hydrae,
320 light-years distant in the constellation of Hydra. W Hydrae is
an example of an AGB (asymptotic-giant-branch) star. Such stars are
cool, bright, old, and lose mass via stellar winds. The name derives
from their positions in the famous Hertzsprung-Russell diagram, which
classifies stars according to their brightness and temperature. Stars
like the Sun evolve over time-scales of thousands of millions of years.
When they reach old age, they puff up and become bigger, cooler and more
prone to lose mass in the form of stellar winds. Stars manufacture
important elements like carbon and nitrogen. When they reach the red-
giant stage, those elements are released into space, ready to be used in
subsequent generations of new stars. ALMA's images provide the clearest
view yet of the surface of a red giant with a mass similar to that of
the Sun. Earlier sharp images have shown details on much more massive,
red supergiant stars like Betelgeuse and Antares. The observations have
also surprised the scientists. The presence of an unexpectedly compact
and bright spot provides evidence that the star possesses surprisingly
hot gas in a layer above its surface: a chromosphere. An alternative
possibility is at least as surprising: that the star was undergoing a
giant flare when the observations were made. The scientists are now
carrying out new observations, both with ALMA and other instruments, in
an effort to understand W Hydrae's surprising atmosphere.
'MONSTER' PLANET DISCOVERED
RAS
A giant planet, which should not exist according to planet-formation
theory, has been discovered around a distant star. The existence of the
'monster' planet, NGTS-1b, challenges theories of planet formation which
state that a planet of that size could not be formed around such a small
star. According to those theories, small stars can readily form rocky
planets but do not gather enough material together to form Jupiter-sized
planets. NGTS-1b however, is a 'gas giant' -- owing to its size and
temperature, it is known as a 'hot Jupiter', a class of planets that are
at least as large as our Solar System's Jupiter, but with around 20%
less mass. Unlike Jupiter, however, NGTS-1b is very close to its star
-- just 3% of the distance between the Earth and the Sun, and completes
an orbit every 2.6 days, so a year on NGTS-1b lasts two and a half
Earth-days. In contrast, the host star is small, with a radius and mass
half that of our Sun. NGTS-1b is the first planet discovered by the
Next-Generation Transit Survey (NGTS), which is being conducted at ESO's
Paranal Observatory in the Atacama Desert in Chile and employs an array
of 12 telescopes to scour the sky. The researchers made their discovery
by continually monitoring patches of the night sky over many months, and
detecting red light from the star with innovative red-sensitive cameras.
They noticed dips in the light from the star every 2.6 days, implying
that a planet was orbiting and periodically blocking the starlight.
Using those data, they then tracked the planet's orbit and calculated
the size, position and mass of NGTS-1b by measuring the radial velocity
of the star. In fact, that method, measuring how much the star wobbles
owing to the gravitational attraction of the planet, seemed the best way
of measuring NGTS-1b's size.
COSMIC 'RECIPE' FOR NEARBY UNIVERSE
NASA/Goddard Space Flight Center
Before its brief mission ended unexpectedly in 2016 March, Japan's
Hitomi X-ray observatory captured exceptional information about the
motions of hot gas in the Perseus galaxy cluster. Now, scientists have
been able to analyze more deeply the chemical make-up of that gas,
providing new insights into the stellar explosions that formed most of
the elements and cast them into space. The Perseus cluster, located 240
million light-years away in its namesake constellation, is the brightest
galaxy cluster in X-rays and among the most massive ones that are 'near'
the Earth. It contains thousands of galaxies orbiting within a thin hot
gas, all bound together by gravity. The gas averages 50 million degrees
Celsius and is the source of the cluster's X-ray emission. Using
Hitomi's high-resolution Soft X-ray Spectrometer (SXS) instrument,
researchers observed the cluster between 2016 Feb. 25 and March 6,
acquiring a total exposure of nearly 3.4 days. The SXS observed an
unprecedented spectrum, revealing a landscape of X-ray peaks emitted
from various chemical elements with a resolution some 30 times better
than had previously been achieved. The scientific team shows that the
proportions of elements found in the cluster are nearly identical to
the ones astronomers see in the Sun. There was no reason to expect that
initially, since the Perseus cluster is a different environment with a
different history from our Sun's. After all, clusters represent an
average chemical distribution from many types of stars in many types of
galaxies that formed long before the Sun. One group of elements is
closely tied to a particular class of stellar explosion, called Type Ia
supernovae. Those blasts are thought to be responsible for producing
most of the Universe's chromium, manganese, iron and nickel -- metals
collectively known as 'iron-peak' elements. Type Ia supernovae entail
the total destruction of a white dwarf, a compact remnant produced by
stars like the Sun. Although stable on its own, a white dwarf can
undergo a runaway thermonuclear explosion if it is paired with another
object as part of a binary system. That occurs either by merging with a
companion white dwarf or, when paired with a nearby normal star, by
stealing some of its partner's gas. The transferred matter can accumu-
late on the white dwarf, gradually increasing its mass until it becomes
unstable and explodes.
An important open question has been whether the exploding white dwarf is
close to the stability limit -- about 1.4 solar masses -- regardless of
its origins. Different masses produce different amounts of iron-peak
metals, so a detailed tally of those elements over a large region of
space, like the Perseus galaxy cluster, could indicate which kinds of
white dwarfs blew up more often. It turns out that a combination of
Type Ia supernovae, with different masses at the moments of their
explosions, is needed to produce the chemical abundances that we see in
the gas at the middle of the Perseus cluster. Astronomers can confirm
that at least about half of Type Ia supernovae must have reached nearly
1.4 solar masses. Taken together, the findings suggest that the same
combination of Type Ia supernovae producing iron-peak elements in our
Solar System also produced those elements in the cluster's gas. That
means that the Solar System and the Perseus cluster experienced broadly
similar chemical evolution, suggesting that the processes forming stars
-- and the systems that became Type Ia supernovae -- were comparable in
the two locations. Although this is just one example, there is no clear
reason to doubt that such similarity could extend beyond our Sun and the
Perseus cluster to other galaxies with different properties.
ONE OF OLDEST OBJECTS IN UNIVERSE OBSERVED
University of Massachusetts at Amherst
Astronomers using the Large Millimeter Telescope (LMT) have detected
the second-most-distant dusty, star-forming galaxy ever found in the
Universe -- born in the first thousand million years after the Big Bang.
It is the oldest object ever detected by the LMT, and at present there
is only one other object like it known, a slightly older and more
distant one. Seeing an object within the first thousand million years
is remarkable, because the Universe was fully ionized, that is, it was
too hot and too uniform to form anything for the first 400 million
years. So our best guess is that the first stars and galaxies and black
holes all formed within the first 500 to 1000 million years. The newly
observed object is very close to being one of the first galaxies ever to
form. This result is not a surprise, because it is what the LMT was
built to do, but it excites astronomers. High-redshift, very-distant
objects are a class of mythical beasts in astrophysics. Astronomers
always knew that there were some out there that are enormously large and
bright, but they are invisible in visible light because they are so
obscured by the thick dust clouds that surround their young stars.
Paradoxically, the most prolific star-forming galaxies and thus the most
luminous are also the most difficult to study with optical telescopes
like the Hubble Space Telescope because they are also the most obscured
by dust. Determining the extremely high redshift of this object with
millimetre waves is a highlight result from the LMT, which can see
through the dust in the radio and millimetre wavelengths. The new
object was first detected by astronomers using the Herschel space
telescope, but for such distant objects, that instrument can take only
relatively blurry pictures that yield little information.
The LMT, located on the summit of a 15,000-foot extinct volcano in
Mexico's central state of Puebla, began collecting its first light in
2011 as a 32-metre millimetre-wavelength radio telescope. It has since
been built out to its full 50-metre diameter and when fully operational
this winter it will be the largest, most sensitive single-aperture
instrument of its kind in the world. It is expected to be at the
forefront of new discoveries about the oldest, most distant objects in
the Universe. In millimetre wavelengths, one of the most common and
easily detected spectral lines is that of carbon monoxide (CO), which
the LMT was designed to trace. For independent confirmation of the
large redshift observed, astronomers at the Harvard-Smithsonian Center
for Astrophysics made additional observations with the Smithsonian
Sub-millimeter Array telescope on Mauna Kea, Hawaii. That allowed the
researchers to create a more detailed image of the new object, referred
to as G09 83808, and to confirm its redshift with a carbon emission
line. Further, the phenomenon of gravitational lensing, which appears
to magnify objects whose light passes near massive objects, as predicted
by Einstein's theory of general relativity, came into play in this
study. A huge galaxy between the object G09 83808 and the observers
on Earth acts as a magnifying glass and makes it look about 10 times
brighter and closer than it really is. With the LMT coming fully online
in the next couple of months, its higher resolution and higher sensiti-
vity will enable astronomers to see more such distant objects.
Topic: Late November Astronomy Bulletin (Read 1850 times)