This is What Happens When a Black Hole Gobbles up a Star

This is What Happens When a Black Hole Gobbles up a Star:

At the center of our galaxy resides a Supermassive Black Hole (SMBH) known as Sagittarius A. Based on ongoing observations, astronomers have determined that this SMBH measures 44 million km (27.34 million mi) in diameter and has an estimated mass of 4.31 million Solar Masses. On occasion, a star will wander too close to Sag A and be torn apart in a violent process known as a tidal disruption event (TDE).

These events cause the release of bright flares of radiation, which let astronomers know that a star has been consumed. Unfortunately, for decades, astronomers have been unable to distinguish these events from other galactic phenomena. But thanks to a new study from by an international team of astrophysicists, astronomers now have a unified model that explains recent observations of these extreme events.

The study – which recently appeared in the Astrophysical Journal Letters under the title “A Unified Model for Tidal Disruption Events” – was led by Dr. Jane Lixin Dai, a physicist with the Niels Bohr Institute’s Dark Cosmology Center. She was joined by members from University of Maryland’s Joint Space-Science Institute and the University of California Santa Cruz (UCSC).

Illustration of the supermassive black hole at the center of the Milky Way. Credit: NRAO/AUI/NSF

As Enrico Ramirez-Ruiz – the professor and chair of astronomy and astrophysics at UC Santa Cruz, the Niels Bohr Professor at the University of Copenhagen, and a co-author on the paper – explained in a UCSC press release:

“Only in the last decade or so have we been able to distinguish TDEs from other galactic phenomena, and the new model will provide us with the basic framework for understanding these rare events.”

In most galaxies, SMBHs do not actively consume any material and therefore do not emit any light, which distinguishes them from galaxies that have Active Galactic Nuclei (AGNs). Tidal disruption events are therefore rare, occurring only once about every 10,000 years in a typical galaxy. However, when a star does get torn apart, it results in the release of an intense amount of radiation. As Dr. Dai explained:

“It is interesting to see how materials get their way into the black hole under such extreme conditions. As the black hole is eating the stellar gas, a vast amount of radiation is emitted. The radiation is what we can observe, and using it we can understand the physics and calculate the black hole properties. This makes it extremely interesting to go hunting for tidal disruption events.”

Illustration of emissions from a tidal disruption event shows in cross section what happens when the material from a disrupted star is devoured by a black hole. Credit: Jane Lixin Dai

In the past few years, a few dozen candidates for tidal disruption events (TDEs) have been detected using wide-field optical and UV transient surveys as well as X-ray telescopes. While the physics are expected to be the same for all TDEs, astronomers have noted that a few distinct classes of TDEs appear to exist. While some emit mostly x-rays, others emit mostly visible and ultraviolet light.

As a result, theorists have struggled to understand the diverse properties observed and create a coherent model that can explain them all. For the sake of their model, Dr. Dai and her colleagues combined elements from general relativity, magnetic fields, radiation, and gas hydrodynamics. The team also relied on state-of-the-art computational tools and some recently-acquired large computer clusters funded by the Villum Foundation for Jens Hjorth (head of DARK Cosmology Center), the U.S. National Science Foundation and NASA.

Using the model that resulted, the team concluded that it is the viewing angle of the observer that accounts for the differences in observation.  Essentially, different galaxies are oriented randomly with respect to observers on Earth, who see different aspects of TDEs depending on their orientation. As Ramirez-Ruiz explained:

“It is like there is a veil that covers part of a beast. From some angles we see an exposed beast, but from other angles we see a covered beast. The beast is the same, but our perceptions are different.”

Artist’s impression of the Large Synoptic Survey Telescope. Credit: lsst.org

In the coming years, a number of planned survey projects are expected to provide much more data on TDEs, which will help expand the field of research into this phenomena. These include the Young Supernova Experiment (YSE) transient survey, which will be led by the DARK Cosmology Center at the Niels Bohr Institute and UC Santa Cruz, and the Large Synoptic Survey Telescopes (LSST) being built in Chile.

According to Dr. Dai, this new model shows what astronomers can expect to see when viewing TDEs from different angles and will allow them to fit different events into a coherent framework. “We will observe hundreds to thousands of tidal disruption events in a few years,” she said. “This will give us a lot of ‘laboratories’ to test our model and use it to understand more about black holes.”

This improved understanding of how black holes occasionally consume stars will also provide additional tests for general relativity, gravitational wave research, and help astronomers to learn more about the evolution of galaxies.

Further Reading: UCSC, Astrophysical Journal Letters

The post This is What Happens When a Black Hole Gobbles up a Star appeared first on Universe Today.

What are the Chances that the Next Generation LSST Could Find New Planets in the Solar System?

What are the Chances that the Next Generation LSST Could Find New Planets in the Solar System?:

In the past few decades, thanks to improvements in ground-based and space-based observatories, astronomers have discovered thousands of planets orbiting neighboring and distant stars (aka. extrasolar planets). Strangely enough, it is these same improvements, and during the same time period, that enabled the discovery of more astronomical bodies within the Solar System.

These include the “minor planets” of Eris, Sedna, Haumea, Makemake, and others, but also the hypothesized planetary-mass objects collectively known as Planet 9 (or Planet X). In a new study led by the Lowell Observatory, a team of researchers hypothesize that the Large Synoptic Survey Telescope (LSST) – a next-generation telescope that will go online in 2022 – has a good chance of finding this mysterious planet.

Their study, titled “On the detectability of Planet X with LSST“, recently appeared online. The study was led by David E. Trilling, an astrophysicist from the Northern Arizona University and the Lowell Observatory, and included Eric C. Bellm from the University of Washington and Renu Malhotra of the Lunar and Planetary Laboratory at The University of Arizona.

Artist’s impression of the Large Synoptic Survey Telescope (LSST). Credit: lsst.org

Located on the Cerro Pachón ridge in north-central Chile, the 8.4-meter LSST will conduct a 10-year survey of the sky that will deliver 200 petabytes worth of images and data that will address some of the most pressing questions about the structure and evolution of the Universe and the objects in it. In addition to surveying the early Universe in order to understand the nature of dark matter and dark energy, it will also conduct surveys of the remote areas of the Solar System.

Planet 9/X is one such object. In recent years, the existence of two planetary-mass bodies have been hypothesized to explain the orbital distribution of distant Kuiper Belt Objects. While neither planet is thought to be exceptionally faint, the sky locations of these planets are poorly constrained – making them difficult to pinpoint. As such, a wide area survey is needed to detect these possible planets.

In 2022, the LSST will carry out an unbiased, large and deep survey of the southern sky, which makes it an important tool when it comes to the search of these hypothesized planets. As they state in their study:

“The possibility of undiscovered planets in the solar system has long fascinated astronomers and the public alike. Recent studies of the orbital properties of very distant Kuiper belt objects (KBOs) have identified several anomalies that may be due to the gravitational influence of one or more undiscovered planetary mass objects orbiting the Sun at distances comparable to the distant KBOs.

Animated diagram showing the spacing of the Solar Systems planet’s, the unusually closely spaced orbits of six of the most distant KBOs, and the possible “Planet 9” (aka. “Planet X”). Credit: Caltech/nagualdesign

These studies include Trujillo & Sheppard’s 2014 study where they noticed similarities in the orbits of distant Trans-Neptunian Objects (TNOs) and postulated that a massive object was likely influencing them. This was followed by a 2016 study by Sheppard & Trujillo where they suggested that the high perihelion objects Sedna and 2012 VP113 were being influence by an unknown massive planet.

This was followed in 2016 by Konstantin Batygin and Michael E. Brown of Caltech suggesting that an undiscovered planet was the culprit. Finally, Malhotra et al. (2016) noted that the most distant KBOs have near-integer period ratios, which was suggestive of a dynamical resonance with a massive object in the outer Solar System. Between these studies, various mass and distance estimates were formed that became the basis of the search for this planet.

Overall, these estimates indicated that Planet 9/X was a super-Earth with anywhere between 5 to 20 Earth masses, and orbited the Sun at a distance of between 150 – 600 AU. Concurrently, these studies have also attempted to narrow down where this Super-Earth’s orbit will take it throughout the outer Solar System, as evidenced by the perturbations it has on KBOs.

Unfortunately, the predicted locations and brightness of the object are not yet sufficiently constrained for astronomers to simply look in the right place at the right time and pick it out. In this respect, a large area sky survey must be carried out using moderately large telescopes with a very wide field of view. As Dr. Trilling told Universe Today via email:

“The predicted Planet X candidates are not particularly faint, but the possible locations on the sky are not very well constrained at all. Therefore, what you really need to find Planet X is a medium-depth telescope that covers a huge amount of sky. This is exactly LSST. LSST’s sensitivity will be sufficient to find Planet X in almost all its (their) predicted configurations, and LSST will cover around half of the known sky to this depth. Furthermore, the cadence is well-matched to finding moving objects, and the data processing systems are very advanced. If you were going to design a tool to find Planet X, LSST is what you would design.”

The orbits of several KBOs provide indications about the possible existence of Planet 9. Credit: Caltech/R. Hurt (IPAC)

However, the team also acknowledges that within certain parameters, Planet 9/X may not be detectable by the LSST. For example, it is possible that that there is a very narrow slice of predicted Planet 9/X parameters where it might be slightly too faint to be easily detected in LSST data. In addition, there is also a small possibility that irregularities in the Planet 9/X cadence might lead to it being missed.

There is the even the unlikely ways in which Planet 9/X could go undetected in LSST data, which would come down to a simple case of bad luck. However, as Dr. Trilling indicated, the team is prepared for these possibilities and is hopeful they will find Planet 9/X, assuming there’s anything to find:

“The more likely conclusion if planet X is not detected in LSST data is that planet X doesn’t exist – or at least not the kind of planet X that has been predicted. In this case, we’ve got to work harder to understand how the Universe created this pattern of orbits in the outer Solar System that I described above. This is a really fun part of science: make a prediction and test it, and find that the result is rarely what is predicted. So now we’ve got to work harder to understand the universe. Hopefully this new understanding makes new predictions that we then can test, and we repeat the cycle.”

The existence of Planet 9/X has been one of the more burning questions for astronomers in recent years. If its existence can be confirmed, astronomers may finally have a complete picture of the Solar System and its dynamics. If it’s existence can be ruled out, this will raise a whole new series of questions about what is going on in the Outer Solar System!

Further Reading: arXiv

The post What are the Chances that the Next Generation LSST Could Find New Planets in the Solar System? appeared first on Universe Today.

Across The Universe - In the Heart of the Heart Nebula

In the Heart of the Heart Nebula:

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Each day a different image or photograph of our fascinating universe is
featured, along with a brief explanation written by a professional astronomer.


2018 February 14

Explanation:
What's that inside the Heart Nebula?

First, the large emission nebula dubbed
IC 1805 looks, in whole, like a human heart.

It's shape perhaps fitting of the
Valentine's Day,
this heart glows brightly in red light
emitted by its most prominent element:
hydrogen.

The red glow and the larger shape are all created by a
small group of stars near the
nebula's center.

In the heart of the
Heart
Nebula are young stars from the open star cluster
Melotte 15 that are eroding away several picturesque
dust pillars with their energetic light and winds.

The open cluster of stars contains a few
bright stars nearly 50 times the mass of our Sun,
many dim stars only a fraction of the mass of our Sun, and an
absent microquasar
that was expelled millions of years ago.

The Heart Nebula is located about 7,500 light years away toward the
constellation
of the mythological Queen of Aethiopia (Cassiopeia).

Across The Universe - Jupiter in Infrared from Hubble

Jupiter in Infrared from Hubble:

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Each day a different image or photograph of our fascinating universe is
featured, along with a brief explanation written by a professional astronomer.


2018 February 21

Jupiter in Infrared from Hubble

Image Credit:
NASA,
ESA,
Hubble;
Data:
Michael Wong
(UC Berkeley)
et al.;
Processing &
License:
Judy Schmidt


Explanation:
Jupiter looks a bit different in infrared light.

To better understand
Jupiter's cloud motions and to help NASA's robotic
Juno spacecraft understand the
planetary context of the small fields that it sees, the
Hubble Space Telescope is being directed to
regularly image the entire Jovian giant.

The colors of Jupiter
being monitored go beyond the normal human visual range to include both
ultraviolet and
infrared light.

Featured here in 2016, three bands of near-infrared light have been digitally reassigned into a mapped color image.

Jupiter appears
different in infrared
partly because the amount of sunlight reflected back is distinct,
giving differing cloud heights and latitudes discrepant brightnesses.

Nevertheless, many familiar features on
Jupiter remain, including the
light zones and dark belts that circle the planet near the equator, the
Great Red Spot on the lower left, and the
string-of-pearls storm systems south of the Great Red Spot.

The poles glow because high altitude haze there is energized by charged
particles from Jupiter's
magnetosphere.

Juno has now completed
10 of 12 planned science orbits of Jupiter and continues to record data that are helping humanity to
understand not only Jupiter's weather but
what lies beneath Jupiter's thick clouds.




Tomorrow's picture: roses aren't red

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Across The Universe - When Roses Aren t Red

When Roses Aren t Red:

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2018 February 22

When Roses Aren't Red

Image Credit &
Copyright:

Eric Coles and
Mel Helm



Explanation:

Not all roses are red
of course,
but they can still be very pretty.

Likewise, the beautiful
Rosette
Nebula and other star forming regions are often shown in
astronomical images with a predominately red hue,
in part because the dominant emission in the nebula is
from hydrogen atoms.

Hydrogen's strongest optical emission line, known as H-alpha,
is in the red region of the spectrum, but the beauty of an
emission nebula need not be appreciated
in red light alone.

Other
atoms in the nebula are also excited by energetic
starlight and produce narrow emission lines as well.

In this gorgeous view of the Rosette Nebula,
narrowband images are combined to show
emission from sulfur atoms in red, hydrogen in blue, and
oxygen in green.

In fact, the
scheme of mapping these narrow atomic
emission lines into broader colors is adopted in
many Hubble images
of stellar nurseries.

The image spans about 100 light-years in
the constellation Monoceros, at the 3,000 light-year
estimated
distance of the
Rosette
Nebula.

To make the Rosette red, just follow
this link or
slide your cursor over the image.



Tomorrow's picture: the moon isn't blue

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Across The Universe - Facing NGC 6946

Facing NGC 6946:

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2018 February 24

Facing NGC 6946

Composite Image Data -

Subaru Telescope
(NAOJ) and Robert Gendler;

Processing -

Robert Gendler



Explanation:

From our vantage point in the
Milky Way Galaxy, we see
NGC 6946
face-on.

The big, beautiful
spiral galaxy
is located just 20 million light-years away, behind a veil of
foreground dust and stars in the high and far-off
constellation of Cepheus.

From the core outward, the galaxy's colors change from the yellowish
light of old stars in the center to young blue star
clusters and reddish star forming regions along the loose, fragmented
spiral arms.

NGC 6946 is also bright in
infrared light and
rich in gas and dust, exhibiting a high star birth and
death rate.

In fact, since the early 20th century
ten
confirmed supernovae, the
death explosions
of massive stars, were
discovered in NGC 6946.

Nearly 40,000 light-years across, NGC 6946 is also known as the
Fireworks Galaxy.

This remarkable portrait of NGC 6946
is a composite that includes
image
data from the 8.2 meter Subaru Telescope
on Mauna Kea.



Tomorrow's picture: star fire

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Across The Universe - NGC 613 in Dust, Stars, and a Supernova

NGC 613 in Dust, Stars, and a Supernova:

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featured, along with a brief explanation written by a professional astronomer.


2018 February 28

NGC 613 in Dust, Stars, and a Supernova

Image Credit:
NASA,
ESA,
Hubble,
S. Smartt
(QUB);
Acknowledgement:
Robert Gendler;
Insets: Victor Buso


Explanation:
Where did that spot come from?

Amateur astronomer Victor Buso was testing out a new camera on his telescope in 2016 when he noticed a curious spot of light appear -- and remain.

After reporting
this unusual observation,
this spot was determined to be light from a
supernova
just as it was becoming visible -- in an earlier stage
than had ever been photographed optically before.

The discovery before and after images, taken about an hour apart,
are shown in the inset of a
more detailed image
of the same spiral galaxy,
NGC 613,
taken by the Hubble Space Telescope.

Follow-up observations show that
SN 2016gkg was likely the explosion of a
supergiant star,
and Buso likely captured the stage where the outgoing
detonation wave
from the stellar core
broke through
the star's surface.

Since astronomers have spent years
monitoring galaxies for supernovas without seeing such a "break out" event,
the odds of Buso capturing this
have been compared to
winning a lottery.




Tomorrow's picture: the lunar 15

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Across The Universe - Arcs, Jets, and Shocks near NGC 1999

Arcs, Jets, and Shocks near NGC 1999:

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Each day a different image or photograph of our fascinating universe is
featured, along with a brief explanation written by a professional astronomer.


2018 March 7

Arcs, Jets, and Shocks near NGC 1999

Image Credit & Copyright:
Mark Hanson;
Annotation: Sakib Rasool
(StarSurfin)


Explanation:
This tantalizing array of nebulas and stars can be found
about two degrees south of the famous
star-forming Orion Nebula.

The
region abounds with energetic young stars producing jets and
outflows that push through the surrounding
material at speeds of hundreds of kilometers per second.

The interaction creates luminous shock
waves known as
Herbig-Haro (HH) objects.

For example, the graceful, flowing arc just right of center
is cataloged as
HH 222, also called the
Waterfall Nebula.

Seen below the Waterfall, HH 401 has a distinctive cone shape.

The bright bluish nebula below and left of center
is NGC 1999, a dusty cloud reflecting
light from an embedded variable star.

The entire cosmic vista spans over 30 light-years, near the edge of the
Orion Molecular Cloud
Complex
some 1,500 light-years distant.




Open Science:
Browse 1,600+ codes in the Astrophysics Source Code Library

Tomorrow's picture: open space

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Across The Universe - Horsehead: A Wider View

Horsehead: A Wider View:

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featured, along with a brief explanation written by a professional astronomer.


2018 March 9

Horsehead: A Wider View

Composition and Processing:
Robert Gendler


Image Data:
ESO,
VISTA,
HLA,
Hubble Heritage Team (STScI/AURA)



Explanation:

Combined image data from the massive,
ground-based
VISTA telescope and the
Hubble Space
Telescope was used to create
this
wide perspective
of the interstellar landscape surrounding
the famous Horsehead Nebula.

Captured at near-infrared wavelengths, the region's dusty
molecular cloud sprawls across the scene that covers
an angle about
two-thirds the size of the Full Moon on the sky.

Left to right the frame spans just over 10 light-years
at the Horsehead's estimated distance of 1,600 light-years.

Also known as
Barnard 33,
the still
recognizable Horsehead Nebula
stands at the upper right,
the near-infrared glow of a dusty pillar topped with newborn stars.

Below and left, the bright reflection nebula NGC 2023 is itself
the illuminated environs of a hot young star.

Obscuring
clouds
below the base of the Horsehead and on the outskirts of
NGC 2023 show the tell-tale far red emission of energetic jets,
known as Herbig-Haro objects,
also associated with newborn stars.



Tomorrow's picture: clair de lune

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Across The Universe - Dual Particle Beams in Herbig Haro 24

Dual Particle Beams in Herbig Haro 24:

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2018 March 11

Dual Particle Beams in Herbig-Haro 24

Image Credit:
NASA,
ESA,
Hubble Heritage
(STScI/AURA)/Hubble-Europe
Collaboration;

Acknowledgment:
D. Padgett (NASA's GSFC),
T. Megeath (U. Toledo),
B. Reipurth (U. Hawaii)


Explanation:
This might look like a double-bladed
lightsaber, but these two cosmic jets actually beam outward from
a
newborn star in a galaxy near you.

Constructed from Hubble Space Telescope image data, the stunning
scene spans about half a light-year across
Herbig-Haro 24 (HH 24), some 1,300 light-years away in the
stellar nurseries
of the Orion B molecular cloud complex.

Hidden from direct view,
HH 24's
central protostar is
surrounded by cold dust and gas flattened into a rotating
accretion disk.

As material from the disk falls toward the young stellar object it heats up.

Opposing jets are blasted out along the
system's rotation axis.

Cutting through the region's interstellar matter, the narrow,
energetic jets produce a series of glowing shock fronts
along their path.




Tomorrow's picture: flying over earth

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Across The Universe - The Complete Galactic Plane: Up and Down

The Complete Galactic Plane: Up and Down:

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Each day a different image or photograph of our fascinating universe is
featured, along with a brief explanation written by a professional astronomer.


2018 March 13

Explanation:
Is it possible to capture the entire plane of our galaxy in a single image?

Yes, but not in one exposure -- and it took some planning to do it in two.

The top part of the
featured image is the night sky above
Lebanon,
north of the equator, taken in 2017 June.

The image was taken at a time when the central band of the
Milky Way Galaxy passed directly overhead.

The bottom half was similarly captured six months later in
latitude-opposite
Chile, south of
Earth's equator.

Each image therefore captured the night sky in
exactly the opposite direction of the other, when fully half the Galactic plane was visible.

The southern half was then inverted -- car and all -- and digitally
appended
to the top half to show the entire central
band of our Galaxy, as a circle, in a single image.

Many stars and nebulas are visible, with the
Large Magellanic Cloud
being particularly notable inside the lower half of the complete galactic circle.

Across The Universe - Interstellar Asteroid ‘Oumuamua Had a Violent Past

Interstellar Asteroid ‘Oumuamua Had a Violent Past:

On October 19th, 2017, the Panoramic Survey Telescope and Rapid Response System-1 (Pan-STARRS-1) telescope in Hawaii announced the first-ever detection of an interstellar asteroid – I/2017 U1 (aka. ‘Oumuamua). Originally mistaken for a comet, follow-up observations conducted by the European Southern Observatory (ESO) and others confirmed that ‘Oumuamua was actually a rocky body that had originated outside of our Solar System.

Since that time, multiple investigations have been conducted to determine ‘Oumuamua’s structure, composition, and just how common such visitors are. At the same time, a considerable amount of attention has been dedicated to determining the asteroid’s origins. According to a new study by a team of international researchers, this asteroid had a chaotic past that causes it to tumble around chaotically.

The study, titled “The tumbling rotational state of 1I/‘Oumuamua“, recently appeared in the scientific journal Nature Astronomy. The study was led by Wesley C. Fraser, a research fellow at the University of Queens Belfast’s Astrophysics Research Center, and included members from the Academy of Sciences of the Czech Republic, the The Open University and the University of Belgrade.



As they indicate, the discovery of ‘Oumuamua has provided scientists with the first opportunity to study a planetesimal born in another planetary system. In much the same way that research into Near-Earth Asteroids, Main Belt Asteroids, or Jupiter’s Trojans can teach astronomers about the history and evolution of our Solar System, the study of a ‘Oumuamua would provide hints as to what was going on when and where it formed.

For the sake of their study, Dr. Fraser and his international team of colleagues have been measuring ‘Oumuamua brightness since it was first discovered. What they found was that ‘Oumuamua wasn’t spinning periodically (like most small asteroids and planetesimals in our Solar System), but chaotically. What this means is that the asteroid has likely been tumbling through space for billions of years, an indication of a violent past.

While it is unclear why this is, Dr. Fraser and his colleagues suspect that it might be due to an impact. In other words, when ‘Oumuamua was thrown from its own system and into interstellar space, it is possible it collided violently with another rock. As Dr. Fraser explained in a Queen’s University Belfast press release:

“Our modelling of this body suggests the tumbling will last for many billions of years to hundreds of billions of years before internal stresses cause it to rotate normally again. While we don’t know the cause of the tumbling, we predict that it was most likely sent tumbling by an impact with another planetesimal in its system, before it was ejected into interstellar space.”

These latest findings mirror what other studies have been able to determine about ‘Oumuamua based on its object changes in its brightness. For example, brightness measurements conducted by the Institute for Astronomy in Hawaii – and using data from the ESO’s Very Large Telescope (VLT) – confirmed that the asteroid was indeed interstellar in origin, and that its shape is highly elongated (i.e. very long and thin).

However, measurements of its color have produced little up until now other than confusion. This was due to the fact that the color appeared to vary between measurements. When the long face of the object is facing telescopes on Earth, it appears largely red, while the rest of the body has appeared neutral in color (like dirty snow). Based on their analysis, Dr. Fraser and his team resolved this mystery by indicating that the surface is “spotty”.

In essence, most of the surface reflects neutrally, but one of its long faces has a large red region – indicating the presence of tholins on its long surface. A common feature of bodies in the outer Solar System, tholins are organic compounds (i.e. methane and ethane) that have turned a deep shade of reddish-brown thanks to their exposure to ultra-violet radiation.

What this indicates, according to Dr. Fraser, is broad compositional variations on ‘Oumuamua, which is unusual for such a small body:

“We now know that beyond its unusual elongated shape, this space cucumber had origins around another star, has had a violent past, and tumbles chaotically because of it. Our results are really helping to paint a more complete picture of this strange interstellar interloper. It is quite unusual compared to most asteroids and comets we see in our own solar system,” comments Dr Fraser.

Oumuamua as it appeared using the William Herschel Telescope on the night of October 29. Queen’s University Belfast/William Herschel Telescope

To break it down succinctly, ‘Oumuamua may have originated closer to its parent star (hence its rocky composition) and was booted out by strong resonances. In the course of leaving its system, it collided with another asteroid, which sent it tumbling towards interstellar space. It’s current chaotic spin and its unusual color are both testaments to this turbulent past, and indicate that its home system and the Solar System have a few things in common.

Since its arrival in our system, ‘Oumuamua has set off a flurry of scientific research. All over the world, astronomers are hoping to get a glimpse of it before it leaves our Solar System, and there are even those who hope to mount a robotic mission to rendezvous with it before its beyond our reach (Project Lyra). In any event, we can expect that this interstellar visitor will be the basis of scientific revelations for years to come!

This study is the third to be published by their team, which has been monitoring ‘Oumuamua since it was first observed in October. All studies were conducted with support provided by the Science and Technology Facilities Council.

Further Reading: Queen’s University Belfast

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Across The Universe - It Turns Out, Andromeda is Younger Than Earth… Sort Of

It Turns Out, Andromeda is Younger Than Earth… Sort Of:

Since ancient times, astronomers have looked up at the night sky and seen the Andromeda galaxy. As the closest galaxy to our own, scientists have been able to observe and scrutinize this giant spiral galaxy for millennia. By the 20th century, astronomers realized that Andromeda was the Milky Way’s sister galaxy and was moving towards us. In 4.5 billion years, it will even merge with our own to form a supergalaxy.

However, it seems astronomers were wrong about the Andromeda galaxy in one major respect. According to recent study led by a team of French and Chinese astronomers, this giant spiral galaxy formed from a major merger that occurred less than 3 billion years ago. This means that Andromeda, as we know it today, is effectively younger than our very own Solar System, which has it beat by about 1.5 billion years!

The study, titled “A 2-3 billion year old major merger paradigm for the Andromeda galaxy and its outskirts“, recently appeared in the Monthly Notices of the Royal Astronomical Society. Led by Francois Hammer, the Principle Investigator of the Galaxies, Etoiles, Physique et Instrumentation (GEPI) department at the Paris Observatory, the team included members from the Chinese Academy of Sciences and the University of Strasbourg.



For the sake of their study, the relied on data gathered by recent surveys that noted considerable differences between the Andromeda and Milky Way galaxies. The first of these studies, which took place between 2006 and 2014, demonstrated all Andromeda has a wealth of young blue stars in its disk (less than 2 billion years old) that undergo random motions over large scales. This is contrast to the stars in the Milky Way’s disk, which are subject only to simple rotation.

In addition, deep observations conducted between 2008 and 2014 with the French-Canadian telescope in the Hawaiian Islands (CFHT) indicated some interesting things about Andromeda’s halo. This vast region, which is 10 times the size of the galaxy itself, is populated by gigantic currents of stars. The most prominent of which is called the “Giant Stream”, a warped disk that has shells and clumps at its very edges.

Using this data, the French-Chinese collaboration then created a detailed numerical model of Andromeda using the two most powerful computers available in France – the Paris Observatory’s MesoPSL and the National Center for Scientific Research’s (CNRS) IDRIS-GENCI supercomputer. With the resulting numerical model, the team was able to demonstrate that these recent observations could be explained only by a recent collision.

Basically, they concluded that between 7 and 10 billion years ago, Andromeda consisted of  two galaxies that had slowly achieved a encountering orbit. After optimizing the trajectories of both galaxies, they determined that they would have collided 1.8 to 3 billion years ago. This collision is what gave birth to Andromeda as we know it today, which effectively makes it younger than our Solar System – which formed almost 4.6 billion years ago.



What’s more, they were able to calculate mass distributions for both parent galaxies that merged to formed Andromeda, which indicated that the larger galaxy was four times the size of the smaller. But most importantly, the team was able to reproduce in detail all the structures that compose Andromeda today – including the bulge, the bar, the huge disk, and the presence of young stars.

The presence of young blue stars in its disk, which has remained unexplained until now, is attributable to a period of intense star formation that took place after the collision. In addition, structures like the “Giant Stream” and the shells of the halo belonged to the smaller parent galaxy, whereas the diffuse clumps and the warped nature of the halo were derived from the larger one.

Their study also explains why the features attributed to the smaller galaxy have an under-abundance in heavy elements compared to the others – i.e. it was less massive so it formed fewer heavy elements and stars. This study is immensely significant when it comes to galactic formation and evolution, mainly because it is the first numerical simulation that has succeeded in reproducing a galaxy in such detail.

It is also of significance given that such a recent impact it could have left materials in the Local Group. In other words, this study could have implications that range far beyond our galactic neighborhood. It is also a good example of how increasingly sophisticated instruments are leading to more detailed observations which, when combined with increasingly sophisticated computers and algorithms, are leading to more detailed models.

https://upload.wikimedia.org/wikipedia/commons/transcoded/d/da/Andromeda_and_Milky_Way_collision.ogv/Andromeda_and_Milky_Way_collision.ogv.480p.webm

One can only wonder if future extra-terrestrial intelligence (ETI) will draw similar conclusions about our own galaxy once it merges with Andromeda, billions of years from now. The collision and resulting features are sure to be of interest to anyone advanced species that’s around to study it!

Further Reading: Paris Observatory, Monthly Notices of the Royal Astronomical Society

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Across The Universe - Neptune’s Huge Storm Is Shrinking Away In New Images From Hubble

Neptune’s Huge Storm Is Shrinking Away In New Images From Hubble:

Back in the late 1980’s, Voyager 2 was the first spacecraft to capture images of the giant storms in Neptune’s atmosphere. Before then, little was known about the deep winds cycling through Neptune’s atmosphere. But Hubble has been turning its sharp eye towards Neptune over the years to study these storms, and over the past couple of years, it’s watched one enormous storm petering out of existence.

“It looks like we’re capturing the demise of this dark vortex, and it’s different from what well-known studies led us to expect.” – Michael H. Wong, University of California at Berkeley.

When we think of storms on the other planets in our Solar System, we automatically think of Jupiter. Jupiter’s Great Red Spot is a fixture in our Solar System, and has lasted 200 years or more. But the storms on Neptune are different: they’re transient.

Voyager 2 captured this image of Neptune in 1982, when it was over 7 million km (4.4 million miles) away from the planet. The Great Dark Spot in the middle of the image was the first storm ever seen on Neptune. Image: By NASA (JPL image) [Public domain], via Wikimedia Commons

The storm on Neptune moves in an anti-cyclonic direction, and if it were on Earth, it would span from Boston to Portugal. Neptune has a much deeper atmosphere than Earth—in fact it’s all atmosphere—and this storm brings up material from deep inside. This gives scientists a chance to study the depths of Neptune’s atmosphere without sending a spacecraft there.

The first question facing scientists is ‘What is the storm made of?’ The best candidate is a chemical called hydrogen sulfide (H2S). H2S is a toxic chemical that stinks like rotten eggs. But particles of H2S are not actually dark, they’re reflective. Joshua Tollefson from the University of California at Berkeley, explains: “The particles themselves are still highly reflective; they are just slightly darker than the particles in the surrounding atmosphere.”

“We have no evidence of how these vortices are formed or how fast they rotate.” – Agustín Sánchez-Lavega, University of the Basque Country in Spain.

But beyond guessing what chemical the spot might me made of, scientists don’t know much else. “We have no evidence of how these vortices are formed or how fast they rotate,” said Agustín Sánchez-Lavega from the University of the Basque Country in Spain. “It is most likely that they arise from an instability in the sheared eastward and westward winds.”

There’ve been predictions about how storms on Neptune should behave, based on work done in the past. The expectation was that storms like this would drift toward the equator, then break up in a burst of activity. But this dark storm is on its own path, and is defying expectations.

“We thought that once the vortex got too close to the equator, it would break up and perhaps create a spectacular outburst of cloud activity.” – Michael H. Wong, University of California at Berkeley.

“It looks like we’re capturing the demise of this dark vortex, and it’s different from what well-known studies led us to expect,” said Michael H. Wong of the University of California at Berkeley, referring to work by Ray LeBeau (now at St. Louis University) and Tim Dowling’s team at the University of Louisville. “Their dynamical simulations said that anticyclones under Neptune’s wind shear would probably drift toward the equator. We thought that once the vortex got too close to the equator, it would break up and perhaps create a spectacular outburst of cloud activity.”

Rather than going out in some kind of notable burst of activity, this storm is just fading away. And it’s also not drifting toward the equator as expected, but is making its way toward the south pole. Again, the inevitable comparison is with Jupiter’s Great Red Spot (GRS).

The GRS is held in place by the prominent storm bands in Jupiter’s atmosphere. And those bands move in alternating directions, constraining the movement of the GRS. Neptune doesn’t have those bands, so it’s thought that storms on Neptune would tend to drift to the equator, rather than toward the south pole.

Jupiter’s prominent storm, the Great Red Spot, is held in place by the alternating storm bands in Jupiter’s atmosphere. Image: By NASA, ESA, and A. Simon (Goddard Space Flight Center) [Public domain], via Wikimedia Commons

This isn’t the first time that Hubble has been keeping an eye on Neptune’s storms. The Space Telescope has also looked at storms on Neptune in 1994 and 1996. The video below tells the story of Hubble’s storm watching mission.



The images of Neptune’s storms are from the Hubble Outer Planets Atmosphere Legacy (OPAL) program. OPAL gathers long-term baseline images of the outer planets to help us understand the evolution and atmospheres of the gas giants. Images of Jupiter, Saturn, Uranus and Neptune are being taken with a variety of filters to form a kind of time-lapse database of atmospheric activity on the four gas planets.

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Across The Universe - Astronomers Observe the Rotating Accretion Disk Around the Supermassive Black Hole in M77

Astronomers Observe the Rotating Accretion Disk Around the Supermassive Black Hole in M77:

During the 1970s, scientists confirmed that radio emissions coming from the center of our galaxy were due to the presence of a Supermassive Black Hole (SMBH). Located about 26,000 light-years from Earth between the Sagittarius and Scorpius constellation, this feature came to be known as Sagittarius A*. Since that time, astronomers have come to understand that most massive galaxies have an SMBH at their center.

What’s more, astronomers have come to learn that black holes in these galaxies are surrounded by massive rotating toruses of dust and gas, which is what accounts for the energy they put out. However, it was only recently that a team of astronomers, using the the Atacama Large Millimeter/submillimeter Array (ALMA), were able to capture an image of the rotating dusty gas torus around the supermassive black hole of M77.

The study which details their findings recently appeared in the Astronomical Journal Letters under the title “ALMA Reveals an Inhomogeneous Compact Rotating Dense Molecular Torus at the NGC 1068 Nucleus“. The study was conducted by a team of Japanese researchers from the National Astronomical Observatory of Japan – led by Masatoshi Imanishi – with assistance from Kagoshima University.

The central region of the spiral galaxy M77. The NASA/ESA Hubble Space Telescope imaged the distribution of stars. ALMA revealed the distribution of gas in the very center of the galaxy. Credit: ALMA (ESO/NAOJ/NRAO)/Imanishi et al./NASA/ESA Hubble Space Telescope and A. van der Hoeven

Like most massive galaxies, M77 has an Active Galactic Nucleus (AGN), where dust and gas are being accreted onto its SMBH, leading to higher than normal luminosity. For some time, astronomers have puzzled over the curious relationship that exists between SMBHs and galaxies. Whereas more massive galaxies have larger SMBHs, host galaxies are still 10 billion times larger than their central black hole.

This naturally raises questions about how two objects of vastly different scales could directly affect each other. As a result, astronomers have sought to study AGN is order to determine how galaxies and black holes co-evolve. For the sake of their study, the team conducted high-resolution observations of the central region of M77, a barred spiral galaxy located about 47 million light years from Earth.

Using ALMA, the team imaged the area around M77’s center and were able to resolve a compact gaseous structure with a radius of 20 light-years. As expected, the team found that the compact structure was rotating around the galaxies central black hole. As Masatoshi Imanishi explained in an ALMA press release:

“To interpret various observational features of AGNs, astronomers have assumed rotating donut-like structures of dusty gas around active supermassive black holes. This is called the ‘unified model’ of AGN. However, the dusty gaseous donut is very tiny in appearance. With the high resolution of ALMA, now we can directly see the structure.”

Motion of gas around the supermassive black hole in the center of M77. The gas moving toward us is shown in blue and that moving away from us is in red. Credit: ALMA (ESO/NAOJ/NRAO), Imanishi et al.

In the past, astronomers have observed the center of M77, but no one has been able to resolve the rotating torus at its center until now. This was made possible thanks to the superior resolution of ALMA, as well as the selection of molecular emissions lines. These emissions lines include hydrogen cyanide (HCN) and formyl ions (HCO+), which emit microwaves only in dense gas, and carbon monoxide – which emits microwaves under a variety of conditions.

The observations of these emission lines confirmed another prediction made by the team, which was that the torus would be very dense. “Previous observations have revealed the east-west elongation of the dusty gaseous torus,” said Imanishi. “The dynamics revealed from our ALMA data agrees exactly with the expected rotational orientation of the torus.”

However, their observations also indicated that the distribution of gas around an SMBH is more complicated that what a simple unified model suggests. According to this model, the rotation of the torus would follow the gravity of the black hole; but what Imanishi and his team found indicated that gas and dust in the torus also exhibit signs of highly random motion.

These could be an indication that the AGN at the center of M77 had a violent history, which could include merging with a small galaxy in the past. In short, the team’s observations indicate that galactic mergers may have a significant impact on how AGNs form and behave. In this respect, their observations of M77s torus are already providing clues as to the galaxy’s history and evolution.

NASA’s Spitzer Space Telescope captured this stunning infrared image of the center of the Milky Way Galaxy, where the black hole Sagitarrius A resides. Credit: NASA/JPL-Caltech

The study of SMBHs, while intensive, is also very challenging. On the one hand, the closest SMBH (Sagitarrius A*) is relatively quiet, with only a small amount of gas accreting onto it. At the same time, it is located at the center of our galaxy, where it is obscured by intervening dust, gas and stars. As such, astronomers are forced to look to other galaxies to study how SMBHs and their galaxies co-exist.

And thanks to decades of study and improvements in instrumentation, scientists are beginning to get a clear glimpse of these mysterious regions for the first time. By being able to study them in detail, astronomers are also gaining valuable insight into how such massive black holes and their ringed structures could coexist with their galaxies over time.

Further Reading: ALMA, arXiv

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