astrobites 2018

Find out the latest thinking about our universe.
User avatar
bystander
Apathetic Retiree
Posts: 17663
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

A Delicate Binary Dance

Post by bystander » Thu Nov 08, 2018 6:43 pm

A Delicate Binary Dance
Astrobites | 2018 Nov 06
Stephanie Hamilton wrote:
Sometimes the little things in life are the most important.

In the case of the Solar System’s life, those little things are asteroids, comets, and Kuiper Belt objects — the leftover debris that didn’t conglomerate into planets. The giant planets (Jupiter, Saturn, Uranus, and Neptune) have tugged these smaller objects around during the Solar System’s 4.5 billion year lifetime, often ejecting them completely. Astronomers can deduce the past behavior of the giant planets by studying the small bodies of the Solar System and how they are distributed. In other words, the Solar System’s smallest members are an important key to unlocking its dynamical past.

With several hundred thousand known asteroids and a few thousand known Kuiper Belt objects, astronomers are just starting to understand the Solar System’s complex history. However, the early days of our Solar System largely remain a mystery (and by early days, I actually mean the first several hundred million years). Various ideas have been proposed to explain how the planets formed and arrived at their current orbits. Each theory predicts variations in observable features of the Solar System, such as how small bodies are distributed. All generally agree that the giant planets underwent some degree of migration, yet none satisfactorily explain what we observe. Today’s bite throws another wrench into the story. The subject? A peculiar binary asteroid named (617) Patroclus-Menoetius. ...

Evidence for Very Early Migration of the Solar System Planets
from the Patroclus-Menoetius Binary Jupiter Trojan
~ David Nesvorný et al
viewtopic.php?t=38681
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

User avatar
bystander
Apathetic Retiree
Posts: 17663
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Re: astrobites 2018

Post by bystander » Thu Nov 08, 2018 7:01 pm

No, astronomers did not just claim that ‘Oumuamua is an extraterrestrial probe
Astrobites | 2018 Nov 07
Samuel Factor wrote:
If you have been paying attention to space news recently you may have seen stories suggesting that the interstellar object ‘Oumuamua, which passed through our solar system just over a year ago, could have been an extraterrestrial probe. Some headlines are a bit sensational (e.g. Scientists say mysterious ‘Oumuamua’ object could be an alien spacecraft (NBC News), Mysterious interstellar object floating in space might be alien, say Harvard researchers (USA Today), or An Alien Spacecraft May Have Passed Through Our Solar System Last Year, Claim Scientists (IFL Science!)) while other articles are a little more doubtful (e.g. Interstellar object may have been alien probe, Harvard paper argues, but experts are skeptical (CNN)). Today’s paper is the source of these articles and, while the premise is a little less far-fetched than you might think, the conclusion lacks transparency. ...
Could Solar Radiation Pressure Explain 'Oumuamua's Peculiar Acceleration? ~ Shmuel Bialy, Abraham Loeb
viewtopic.php?t=37698
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

User avatar
bystander
Apathetic Retiree
Posts: 17663
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Black Holes During the Cosmic Dawn

Post by bystander » Thu Nov 08, 2018 7:20 pm

Black Holes During the Cosmic Dawn
Astrobites | 2018 Nov 08
Joshua Kerrigan wrote:
Cosmologically important phenomena are typically discussed on the scales of gigaparsecs (Gpc); to give you some idea of the sizes involved, one Gpc could fit approximately 33 thousand Milky Way galaxies end-to-end. That’s a pretty crazy scale and with that in mind today we’ll gain an understanding for how astrophysical events beginning on the order of parsecs can have far-reaching affects cosmologically.

The cosmological period prior to the reionization of the Universe’s hydrogen is typically described as being the cosmic dawn. This stage in the history of the Universe is marked by the formation of the first stars and galaxies. But it doesn’t end there, connecting these large structures throughout the Universe is the Intergalactic Medium (IGM). The IGM during the cosmic dawn consists of mostly neutral hydrogen, and compared to galaxies, is much less dense (10-27 kg/m3 compared to the density of our Milky Way which is ~10-19 kg/m3). The UV radiation from these early stars and galaxies are what most astronomers and cosmologists believe led to reionization. Put simply, this ionizing radiation extended symmetrically from these sources and over time these regions of reionized IGM began to overlap leading to complete reionization. While this is our current `best guess’, cosmologists typically wonder: ‘What roles do other structures play during this period?’ One type of galaxy of interest are those containing Active Galactic Nuclei (AGN), which are galaxies with a very dense core with a supermassive black hole (SMBH) at its center that is accreting matter. These AGN are extremely luminous and can produce a lot of X-ray and UV emissions. What we’ll be exploring today is how these SMBH influence the surrounding regions. ...

Observing the Influence of Growing Black Holes on the Pre-reionization IGM ~ Evgenii O. Vasiliev, Shiv K. Sethi, Yuri A. Shchekinov
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

User avatar
bystander
Apathetic Retiree
Posts: 17663
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Feeding black holes, up close and personal

Post by bystander » Tue Nov 13, 2018 4:31 pm

Feeding black holes, up close and personal
Astrobites | 2018 Nov 12
Joanna Ramasawmy wrote:
Supermassive black holes — the phenomenal engines that power the brightest objects in the universe, quasars — are observed only moments (ok, a few hundred million years) after the Big Bang. These observations present a major problem for astrophysics: how can these supermassive objects grow so large in such a short space of time?

There are a few competing scenarios for the formation of supermassive black holes, or SMBHs. ... A critical factor in working out which of these scenarios is most likely is our understanding of how black holes grow. And it’s complicated. The main ingredient is gas, but funnelling that gas into a black hole depends on processes spanning orders of magnitude in distance, from the megaparsecs-wide large scale structure of the cosmic web down to the relatively miniscule intricacies of gas falling into the event horizon of a black hole as small as our own solar system. Creating a simulation that can explore this detail as well as taking the largest structures in the universe into account is, as the authors of today’s astrobite put it, a “tremendous computational challenge”. ...

Zooming in on Supermassive Black Holes: How Resolving Their Gas Cloud Host
Renders Their Accretion Episodic
~ Ricarda S. Beckmann, Julien Devriendt, Adrianne Slyz
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

User avatar
bystander
Apathetic Retiree
Posts: 17663
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

A hidden reservoir of multi-planet systems?

Post by bystander » Tue Nov 13, 2018 4:44 pm

A hidden reservoir of multi-planet systems?
Astrobites | 2018 Nov 13
Eckhart Spalding wrote:
Kepler is dead, long live Kepler! It would be an understatement to say that the Kepler spacecraft transformed our understanding of exoplanets, and it’s sad to see it go. Kepler made an especially big impact on our understanding of exoplanet systems with Neptune- or Earth-sized planets, especially those close in to their stars, and with periods of fewer than ~100 days. In combination with ground-based transit and radial velocity (RV) surveys, the thousands of planets we now know of make it possible to actually do population syntheses and start to understand the demographics of exoplanet systems.

For example, we have learned that there is a pretty solid correlation between host star metallicity and the presence of hot Jupiter planets, which may be evidence for core-accretion models of planet formation. Strangely, systems of multiple, rocky planets appear around stars with a wide range of metallicities. Could it be that there just isn’t enough material in protoplanetary disks around metal-poor stars to feed Jovian-mass planets? Or are there severe observational biases in play? RV surveys have tended to avoid metal-poor stars, because they have fewer absorption lines to measure; maybe metal-poor stars haven’t been sampled enough? Even more curiously, systems with hot Jupiters appear to be very distinct from compact multi-planet systems: they tend not to overlap. To try to resolve some of these conundrums, the authors of today’s paper shed new light on the relation of exoplanet system type to host star metallicity. ...

Compact Multi-planet Systems are more Common around Metal-poor Hosts ~ John M. Brewer et al
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

User avatar
bystander
Apathetic Retiree
Posts: 17663
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Old but gold: a huge primordial proto-cluster

Post by bystander » Thu Nov 15, 2018 5:00 pm

Old but gold: a huge primordial proto-cluster
Astrobites | 2018 Nov 14
Natalia Del Coco wrote:
The biggest structures know in the Universe are galaxy clusters (GC): they are made of hundreds or even thousands of galaxies, lots of gas and a huge amount of dark matter. But a long time ago, these giants were actually babies. Right after the Big Bang, when no galaxies, stars or even molecules were formed yet, the Universe was extremely homogeneous, although it had density fluctuations with relative amplitude of ~ 10-5. During the cosmos’ expansion, the regions that initially were slightly heavier became increasingly heavier, because mass attracts mass. Then, clumps of gas turned into stars. Due to their mutual gravitational attraction force, they gradually got closer to each other, growing into galaxies, which congregated further – also because of the gravity – into today’s GC (for a deeper understanding, read this).

Since looking at distant astronomical objects means to look into the past, we may be able to see the progenitors of the GC, the proto-clusters. They should be far from us (at high redshifts, z), comprised by dozens of galaxies forming lots of stars, therefore containing a huge amount of dust and gas (the stars’ ingredients). In other words, we should see these proto-clusters as distant aggregations of galaxies that are very bright and very red, and therefore visible only in the submillimeter/millimeter from Earth (which are the color and wavelength detected in earth frame from the gas and dust radiation of distant galaxies when heated by its stars). To observe these systems may teach us about how the Universe and its structures evolve through the cosmic time. In today’s paper, the authors report the discovery of a proto-cluster core with extreme characteristics: super dense, super massive and super old. ...

An Extreme Protocluster of Luminous Dusty Starbursts in the Early Universe - I. Oteo et al
viewtopic.php?t=38233
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

User avatar
bystander
Apathetic Retiree
Posts: 17663
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

How can you tell if a young planet is migrating?

Post by bystander » Thu Nov 15, 2018 5:08 pm

How can you tell if a young planet is migrating?
Astrobites | 2018 Nov 15
Michael Hammer wrote:
Imagine if we could watch planetary systems take shape. We would point our telescopes at the nearest and brightest newly-formed stars that are still surrounded by some of the leftover material from the cloud in which they formed. We would then see this leftover material mold itself into a disk around the star, a so-called “proto-planetary disk” made up of mostly gaseous molecules and a small, but sufficient amount of dust for building planets. Every day, we could observe each disk and watch each system evolve.

With a series of snapshots, we would see things like the first planetesimals coalescing from what started out as microscopic micron-sized dust. We would see the gas in the disk slowly spill onto the star. We would see the dust in the disk drift through the gas and fall towards the star as well. And eventually, we would see the planetesimals grow large enough to form planets the size of the Earth or even Jupiter. Once these planets form, we would also see whether each one stays where it formed or if they migrate and move either towards or away from their stars.

Unfortunately, many of these processes last not days, but thousands of years, or even the entire lifetime of the disk itself (3 to 10 million years). To make matters worse, planets that have just formed are often extremely difficult to spot as they are typically too small, too dim, and also enshrouded by the disks in which they formed. Both of these factors make it difficult to study the processes that sculpt planetary systems.

In particular, we cannot wait millennia to see if planets migrate away from where they formed or if they just stay where they are. This issue is of paramount importance since we cannot develop good models of how specific planets formed if we do not even know where they formed. In today’s paper, Farzana Meru et al. propose a solution to that problem by developing a new way to probe whether a planet is migrating through the disk, just from looking at observations of dust at a single point in time. ...

Is the Ring Inside or Outside the Planet?
The Effect of Planet Migration on Dust Rings
~ Farzana Meru et al
viewtopic.php?t=38808
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

User avatar
Ann
4725 Å
Posts: 9117
Joined: Sat May 29, 2010 5:33 am

Re: Old but gold: a huge primordial proto-cluster

Post by Ann » Thu Nov 15, 2018 5:35 pm

bystander wrote:
Thu Nov 15, 2018 5:00 pm
Old but gold: a huge primordial proto-cluster
Astrobites | 2018 Nov 14
Natalia Del Coco wrote:
The biggest structures know in the Universe are galaxy clusters (GC): they are made of hundreds or even thousands of galaxies, lots of gas and a huge amount of dark matter. But a long time ago, these giants were actually babies. Right after the Big Bang, when no galaxies, stars or even molecules were formed yet, the Universe was extremely homogeneous, although it had density fluctuations with relative amplitude of ~ 10-5. During the cosmos’ expansion, the regions that initially were slightly heavier became increasingly heavier, because mass attracts mass. Then, clumps of gas turned into stars. Due to their mutual gravitational attraction force, they gradually got closer to each other, growing into galaxies, which congregated further – also because of the gravity – into today’s GC (for a deeper understanding, read this). ...

An Extreme Protocluster of Luminous Dusty Starbursts in the Early Universe - I. Oteo et al
viewtopic.php?t=38233
Natalia del Coco wrote:

The lower limit value obtained was solar masses per year, being the highest found until now.
...
For the primer, they utilized the CI emission lines, achieving a minimal value of times the solar mass.

The second one was calculated in three different manners, reaching up to times the solar mass (for comparison, the estimated mass of the Local Group is times the solar mass).
I don't get it.

Ann
Color Commentator

BDanielMayfield
Don't bring me down
Posts: 1788
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: East Idaho

Re: Old but gold: a huge primordial proto-cluster

Post by BDanielMayfield » Fri Nov 16, 2018 5:59 am

Ann wrote:
Thu Nov 15, 2018 5:35 pm
Natalia del Coco wrote:

The lower limit value obtained was _____ solar masses per year, being the highest found until now.
...
For the primer, they utilized the CI emission lines, achieving a minimal value of ______ times the solar mass.

The second one was calculated in three different manners, reaching up to _______ times the solar mass (for comparison, the estimated mass of the Local Group is ______ times the solar mass).
I don't get it.

Ann
Nor could anyone else Ann. She must have left filling in the numbers as an exercise for the reader :?:
"Happy are the peaceable ... "

User avatar
Ann
4725 Å
Posts: 9117
Joined: Sat May 29, 2010 5:33 am

Re: Old but gold: a huge primordial proto-cluster

Post by Ann » Fri Nov 16, 2018 6:12 am

BDanielMayfield wrote:
Fri Nov 16, 2018 5:59 am
Ann wrote:
Thu Nov 15, 2018 5:35 pm
Natalia del Coco wrote:

The lower limit value obtained was _____ solar masses per year, being the highest found until now.
...
For the primer, they utilized the CI emission lines, achieving a minimal value of ______ times the solar mass.

The second one was calculated in three different manners, reaching up to _______ times the solar mass (for comparison, the estimated mass of the Local Group is ______ times the solar mass).
I don't get it.

Ann
Nor could anyone else Ann. She must have left filling in the numbers as an exercise for the reader :?:
Obviously. :wink:

The task she has given us, filling in the missing numbers, is a bit hard for the average amateur astro nerd. :P

Ann
Color Commentator

User avatar
bystander
Apathetic Retiree
Posts: 17663
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Re: Old but gold: a huge primordial proto-cluster

Post by bystander » Fri Nov 16, 2018 2:19 pm

Ann wrote:
Thu Nov 15, 2018 5:35 pm
Natalia del Coco wrote:
The lower limit value obtained was 6500 solar masses per year, being the highest found until now.
...
For the primer, they utilized the CI emission lines, achieving a minimal value of 6.6×1011 times the solar mass.

The second one was calculated in three different manners, reaching up to 4.4×1013 times the solar mass

(for comparison, the estimated mass of the Local Group is 4.2×1012 times the solar mass).
The first three values are from the abstract of the referenced paper (DOI: 10.3847/1538-4357/aaa1f1).
The mass for the Local Group I took from the abstract of arXiv:1312.2587.
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor

User avatar
Ann
4725 Å
Posts: 9117
Joined: Sat May 29, 2010 5:33 am

Re: Old but gold: a huge primordial proto-cluster

Post by Ann » Fri Nov 16, 2018 3:47 pm

bystander wrote:
Fri Nov 16, 2018 2:19 pm
Ann wrote:
Thu Nov 15, 2018 5:35 pm
Natalia del Coco wrote:
The lower limit value obtained was 6500 solar masses per year, being the highest found until now.
...
For the primer, they utilized the CI emission lines, achieving a minimal value of 6.6×1011 times the solar mass.

The second one was calculated in three different manners, reaching up to 4.4×1013 times the solar mass

(for comparison, the estimated mass of the Local Group is 4.2×1012 times the solar mass).
The first three values are from the abstract of the referenced paper (DOI: 10.3847/1538-4357/aaa1f1).
The mass for the Local Group I took from the abstract of arXiv:1312.2587.
Thanks, bystander! :D

Ann
Color Commentator

BDanielMayfield
Don't bring me down
Posts: 1788
Joined: Thu Aug 02, 2012 11:24 am
AKA: Bruce
Location: East Idaho

Re: astrobites 2018

Post by BDanielMayfield » Fri Nov 16, 2018 4:38 pm

Ann is by no means an "average amateur astro nerd."

Come to think of it, none of us are. Especially bystander. Well done sir.
"Happy are the peaceable ... "

User avatar
bystander
Apathetic Retiree
Posts: 17663
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Why don’t they just break up?

Post by bystander » Sat Nov 17, 2018 3:41 am

Why don’t they just break up?
Astrobites | 2018 Nov 16
Thankful Cromartie wrote:
Known for their extreme density and unfathomably rapid rotation rates, millisecond pulsars (MSPs) are among the Universe’s most exotic treasures. Here at astrobites, however, one rotation every few milliseconds isn’t good enough — we need to know why they won’t spin faster. ...

The authors of today’s featured article conducted simulations to explore the spin period distribution in low-mass X-ray binary (LMXB) neutron stars, which are actively accreting matter from their low-mass stellar companions. They investigated what spin period distributions would result from three different GW emission mechanisms. Observations have suggested that the population of rapidly rotating, accreting pulsars is bimodal in spin frequency (see Figure 1), with an excess of MSPs in the 550-600 Hz range. If their GW emission simulations could reproduce such a distribution, it might aid in understanding the mysterious lack of ultra-fast MSPs. ...

Population Synthesis of Accreting Neutron Stars Emitting Gravitational Waves ~ Fabian Gittins, Nils Andersson
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk.
— Garrison Keillor