astrobites 2017

Find out the latest thinking about our universe.
User avatar
bystander
Apathetic Retiree
Posts: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Galaxy Clusters across Cosmic Time

Postby bystander » Fri Mar 10, 2017 5:22 pm

Same ol’ same ol’? Galaxy Clusters across Cosmic Time
astrobites | 2017 Mar 09
Gourav Khullar wrote:
We have come a long way since the 1930s, when the words ‘galaxy cluster‘ were posited for the first time by Fritz Zwicky, in relation with the presence of dark matter in the Coma cluster. Developments in multi-wavelength astrophysics have allowed us to probe different components of a cluster with different telescopes. For example, star-forming galaxies of galaxy clusters are observed using optical telescopes because starlight in these galaxies loves emitting photons with the roughly the same energy that we see from the sun. Some of these galaxies are super-red, have no star-formation and a ton of dust, that is best seen from infra-red and radio telescopes. Today’s story takes us to the intermittent space between different galaxies inside a cluster, called the intra-cluster medium (ICM) and its emissions. ...

The Remarkable Similarity of Massive Galaxy Clusters from z~0 to z~1.9 - Michael McDonald 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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

How long do quasars shine?

Postby bystander » Fri Mar 10, 2017 5:30 pm

How long do quasars shine?
astrobites | 2017 Mar 10
Suk Sien Tie wrote:
In the deep center of every massive galaxy, extremely massive but invisible black holes reign supreme. How these supermassive black holes (SMBHs) grew to boast of their 107-109 Msun masses still eludes us today. These massive beasts are awakened when surrounding matter spirals in and falls into them, creating active galactic nuclei (AGN) as luminous as our Milky Way. In this state, they spew out radiation from the radio to the X-rays. When the accretion of matter is particularly high, the AGN becomes very luminous and is called a quasar. (Here is a handy guide on AGN taxonomy.) ...

This paper examines the episodic lifetime of quasars using singly-ionized helium (He II) as the probe. At redshift z~3, most of the Helium in the Universe is singly-ionized. The last electron in He II can be knocked free by the powerful radiation from quasars. As a quasar ionizes its surrounding He II, one can imagine a sphere of ionized He II around the quasar that expands outward with the ionizing radiation. The longer the quasar shines, the larger this sphere becomes. ...

Statistical Detection of the HeII Transverse Proximity Effect:
Evidence for Sustained Quasar Activity for >25 Million Years
- Tobias M. Schmidt 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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Honey, it’s an Intermediate Mass Black Hole this time!

Postby bystander » Tue Mar 14, 2017 3:59 pm

Honey, it’s an Intermediate Mass Black Hole this time!
astrobites | 2017 Mar 13
Bhawna Motwani wrote:
Our universe is speculated to host a plethora of black holes, and they come in varied sizes: stellar mass (SBH), intermediate-mass (IMBH), and super-massive (SMBH). Of this assortment, SBHs, that have masses of a few to tens of times the mass of our Sun, as well as the SMBH variety that can be a million- to billion-fold heavier and found in the central engines of active galactic nuclei at large redshifts, have been studied and characterized for a long time. On the other hand, what remained elusive to this point, has been the existence and properties of a novel class of long-lived black holes (IMBHs), thought to represent the evolutionary bridge between SBHs and SMBHs. ...

Very recently, Kızıltan et al. published the evidence of an IMBH residing – in line with previous theoretical predictions – at the centre of 47 Tucanae (or NGC 104), one of the most massive globular clusters known. ...

An intermediate-mass black hole in the centre of the globular cluster 47 Tucanae - Bülent Kızıltan, Holger Baumgardt, Abraham Loeb

viewtopic.php?t=36828
viewtopic.php?t=36951
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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Gemstones Askew in the Heavens

Postby bystander » Fri Mar 17, 2017 7:37 pm

Gemstones Askew in the Heavens
astrobites | 2017 Mar 14
Paddy Alton wrote:
In today’s article I want to take a closer look at gravitational lenses and open a window on some of the interesting science astronomers are using these objects for.

A gravitational lens results from a chance alignment of two galaxies, one near and one far. To understand how it works, we need to take a brief tour through Einstein’s General Theory of Relativity – but don’t panic! I’ll keep it light. In his landmark theory, now over a century old, Einstein outlined the mechanism by which gravity acts. Rather than being a fixed background against which events happen – a sort of cosmic stage – space itself can be warped and stretched by the presence of mass. The more massive the object, the stronger the distortion. The upshot is that anything following a straight path through space, such as a light ray, finds itself travelling a curved path instead when it passes near a mass – as if a force was acting directly upon it. It’s this apparent force that we call gravity. This effect was used in 1919 by Sir Arthur Eddington to confirm the predictions of General Relativity, to much excitement and confusion; during an eclipse, Eddington measured the angle through which the Sun’s gravity deflected the light of distant stars, showing that this matched the theory. In special circumstances, the same effect can focus the deflected light rays, just like a traditional lens ...

Planck's Dusty GEMS. III. A massive lensing galaxy with a
bottom-heavy stellar initial mass function at z=1.5
- R. Canameras 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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Super Star Clusters Far Far Away

Postby bystander » Fri Mar 17, 2017 7:56 pm

Super Star Clusters Far Far Away
astrobites | 2017 Mar 15
Benny Tsang wrote:...
It always amazes me to see the manifestation of gravitational lensing in deep Hubble images – light from very-far-away galaxies being magnified and stretched into arcs by the strong gravity of the quite-far-away galaxy clusters. The gravity of the galaxy clusters acts as a “natural telescope” that focuses light to reveal background galaxies, which otherwise are too faint to be seen.

Astrophysicists have been puzzling over the mystery of reionization. How did reionization occur and what sources caused it? To try to answer these questions we need to know the origins and the properties of the early, far-away galaxies that were responsible. Recently, it was found that the huge number of faint galaxies may provide enough photons to reionize the Universe. The technique of gravitational lensing comes in very handy because it allows far-away and faint objects to be observed! ...

Magnifying the early episodes of star formation:
Super-star clusters at cosmological distances
- E. Vanzella 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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

When the Neighborhood Dwarf Galaxies were Kids

Postby bystander » Fri Mar 17, 2017 8:10 pm

When the Neighborhood Dwarf Galaxies were Kids
astrobites | 2017 Mar 16
Stacy Kim wrote:
The heavens bespeak a dark and quiet night, glinting here and there with distant stars and yet more distant galaxies. But in ages past, long before the birth of our stalwart Sun, before even the supernovae that spewed the calcium in our bones and the iron in our blood into the gas that formed the Sun and the Solar System, there was darkness. The cosmic dark ages reigned for nearly a million years before the first stars blinked blearily on.

Then suddenly there came an age of light. We’re not entirely sure what exactly lit up the universe, but among the suspects are the first galaxies. Once practically invisible, they were lit aflame as the first stars began to burn hot and bright within them. They generated copious amounts of ultra-violet (UV) light, energetic enough to ionize the hydrogen in the universe. So much UV flux was generated that nearly all the hydrogen in the universe was ionized, leaving the universe clear and transparent and allowing us the majestic views of faraway galaxies that we take for granted today. ...

Local Group Ultra-Faint Dwarf Galaxies in the Reionization Era - Daniel R. Weisz, Michael Boylan-Kolchin
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: 8308
Joined: Sat May 29, 2010 5:33 am

Re: Gemstones Askew in the Heavens

Postby Ann » Tue Mar 21, 2017 1:12 am

bystander wrote:Gemstones Askew in the Heavens
astrobites | 2017 Mar 14
Paddy Alton wrote:
In today’s article I want to take a closer look at gravitational lenses and open a window on some of the interesting science astronomers are using these objects for.

A gravitational lens results from a chance alignment of two galaxies, one near and one far. To understand how it works, we need to take a brief tour through Einstein’s General Theory of Relativity – but don’t panic! I’ll keep it light. In his landmark theory, now over a century old, Einstein outlined the mechanism by which gravity acts. Rather than being a fixed background against which events happen – a sort of cosmic stage – space itself can be warped and stretched by the presence of mass. The more massive the object, the stronger the distortion. The upshot is that anything following a straight path through space, such as a light ray, finds itself travelling a curved path instead when it passes near a mass – as if a force was acting directly upon it. It’s this apparent force that we call gravity. This effect was used in 1919 by Sir Arthur Eddington to confirm the predictions of General Relativity, to much excitement and confusion; during an eclipse, Eddington measured the angle through which the Sun’s gravity deflected the light of distant stars, showing that this matched the theory. In special circumstances, the same effect can focus the deflected light rays, just like a traditional lens ...

Planck's Dusty GEMS. III. A massive lensing galaxy with a
bottom-heavy stellar initial mass function at z=1.5
- R. Canameras et al


Paddy Alton wrote:
Following this method, the authors infer that the foreground galaxy is indeed more massive than might be expected from its brightness alone, indicative of an excess of dim dwarf stars. This is consistent with results from galaxies in the nearby universe, which have undergone billions of years of additional evolution, forging a crucial link between local galaxies and their antecedents.


Indeed, we may see an excess of dim dwarf stars in the local universe, too.

Deborah Byrd of EarthSky wrote:
Astronomers have peered into eight relatively nearby elliptical galaxies and made a discovery suggesting that small, dim red dwarf stars in these sorts of galaxies might be 20 times more plentiful than in our spiral-shaped Milky Way galaxy.


It may indeed be true that elliptical galaxies contain huge numbers of dim red dwarf stars, boosting the mass of the galaxies considerably but having little impact on the galaxies' light output.

Ann
Color Commentator

User avatar
bystander
Apathetic Retiree
Posts: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Sardines in Space

Postby bystander » Fri Mar 24, 2017 4:09 pm

Sardines in Space: The Intensely Densely-Packed Planets Orbiting Kepler-11
astrobites | 2017 Mar 20
Mara Zimmerman wrote:
The dawn of the Kepler Space Telescope data has unearthed a treasure trove of new and unusual celestial objects. Among these new discoveries is the planetary system Kepler-11. The system contains six transiting planets that are packed incredibly close around the Sun-like star, much like sardines are packed very closely in cans. The first five of these planets fall within the orbit of Mercury, and the sixth one falls well within the orbit of Venus. Few systems like this have been discovered; most planetary systems have a much larger separation between the planets, yet this system has its planets arranged in an extremely packed, yet extraordinarily still stable, way. ...

A closely packed system of low-mass, low-density planets transiting Kepler-11 - JJ Lissauer et al
viewtopic.php?t=22814
viewtopic.php?t=22977
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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

One mechanism to rule all magnetic bodies

Postby bystander » Fri Mar 24, 2017 4:16 pm

One mechanism to rule all magnetic bodies
astrobites | 2017 Mar 21
Ingrid Pelisoli wrote:
If you have ever used a compass, you know the Earth has a magnetic field. That’s lucky for us, because this field protects us from highly energetic particles that could make life on Earth quite difficult, like it is on Mars (although NASA might have a solution). The Sun has a magnetic field too, which is beautifully pictured on the featured image. The explanation for these fields is a dynamo effect: in short, ionised matter circling inside the Sun and the Earth generates the field. This explanation holds for most stars in which we detect a magnetic field. White dwarf stars, the most common end-point of stellar evolution (which makes them extremely useful in understanding the history of the Galaxy and even of the Universe), seemed to be an exception. They can present unusually high magnetic fields, up to a 100 million times the field of the Sun! The explanation for such colossal fields is still an open question. The authors of today’s paper present a possible solution by cleverly making use of already well-known astrophysical mechanisms. ...

A Common Origin of Magnetism from Planets to White Dwarfs - Jordi Isern et al

viewtopic.php?t=36756#p268134
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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Hidden water in the deep atmosphere of Jupiter

Postby bystander » Fri Mar 24, 2017 4:23 pm

Hidden water in the deep atmosphere of Jupiter
astrobites | 2017 Mar 22
Shang-Min Tsai wrote:
The search for extrasolar planets has become one of the most popular topics in astronomy in the last two decades. While we are fascinated by the diversity of the extrasolar systems, the fact remains that there are still many mysteries that exist within our own Solar System. Our largest planet, Jupiter is an example of one of these mysteries, with an interior structure and the storm colors that are not yet fully understood. In today’s paper, we are taking a look at the bulk oxygen composition of Jupiter. ...

Modeling the disequilibrium species for Jupiter and Saturn:
Implications for Juno and Saturn entry probe
- Dong Wang, Jonathan Lunine, Olivier Mousis
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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

From One Satellite to Another: Finding Clusters with Gaia

Postby bystander » Fri Mar 24, 2017 4:32 pm

From One Satellite to Another: Finding Clusters with Gaia
astrobites | 2017 Mar 23
Matthew Green wrote: ...
Previous astrobiters have written about Gaia, the space telescope that will measure the position and velocity of over a billion stars. At the moment, only the first set of Gaia data has been released: it contains the brightness and positions of most of the targets, but not yet their distances, colours or velocities.

The team behind today’s paper have been using just these stellar position measurements to hunt for new galactic satellites. Towards this end, they search for small patches of the sky that have an unusually high number of stars when compared to nearby regions. Figure 2 shows the density they find. The bright yellow spots are regions of unusually high density such as clusters or dwarf galaxies. The team were surprised at how effective their algorithm was: it highlighted several incredibly faint dwarf galaxies that were only discovered in the past two years. It also found two new objects, now named Gaia 1 and Gaia 2, which they analyse in today’s paper. ...

Gaia 1 and 2. A pair of new satellites of the Galaxy - S. E. Koposov, V. Belokurov, G. Torrealba
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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

A neutron star in the Eye of Sauron?

Postby bystander » Fri Mar 24, 2017 4:45 pm

A neutron star in the Eye of Sauron?
astrobites | 2017 Mar 24
Leonardo dos Santos wrote:
When you go somewhere with relatively dark skies, you can pull up your smartphone and that handy planetarium app, look for the star Fomalhaut in the constellation of Pisces, and then point it to your friend and say: You see, there is a planet orbiting that star, and we have literally seen it with our telescopes! — But there is a catch: The little blob of light which was directly observed by Hubble is weird, and it doesn’t really look like a planet. In fact, some astronomers have proposed it could be a neutron star. Gasp! ...

A Test of the Neutron Star Hypothesis for Fomalhaut b - K. Poppenhaeger, K. Auchettl, S.J. Wolk
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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

The Life Cycles of Dust Grains

Postby bystander » Tue Mar 28, 2017 2:38 pm

The Life Cycles of Dust Grains
astrobites | 2017 Mar 27
Benny Tsang wrote:
You aren’t truly an astronomer if your work doesn’t involve dust at some point (and I don’t mean the dust on our desks!) Dust grains are literally everywhere in space. They play an important role when we take pictures of the infant Universe, in the births of stars and planets, and in modifying the light we see from far-away galaxies. Mainly composed of carbon and silicon, interstellar dust grains are believed to be created in stars and in supernova explosions. Understanding dust isn’t an easy task because of it is interwoven with astronomy on so many levels. For example, the formation and destruction of dust grains connect with the physics and chemistry of the gas – dust grains absorb UV light which would otherwise break apart gas molecules or ionize atoms, while molecular hydrogen mainly forms on the surface of dust grains. At the same time, gas and dust do not move together in space.

Today’s paper is part of an international collaboration known as the SImulating the Life Cycle of molecular Clouds (SILCC) project. The goals of this project are to provide a self-consistent picture of how molecular clouds are formed and destroyed, how stars are born within them, and how galactic outflows are driven. Since dust is important in every step of this endeavor, understanding the life cycles of dust grains is essential. ...

The turbulent life of dust grains in the supernova-driven, multi-phase interstellar medium - Thomas Peters 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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

A Cosmic Beach Getaway

Postby bystander » Wed Apr 05, 2017 7:11 pm

A Cosmic Beach Getaway
astrobites | 2017 Mar 28
Emily Sandford wrote:
Escaping from prison is hard. First, you have to convince your skeptical friend to smuggle you a rock hammer and a big poster of Rita Hayworth. Then you have to spend 20 years digging a tunnel through your cell wall by night and laundering money for your despotic warden by day. You’re not even done after you crawl half a mile through a sewer pipe to break out, because you have to hike into the cornfields in a business suit to leave an inspirational note under a rock for your friend.

Escaping from Earth, on the other hand, is easy. All you have to do is go up at 25,000 miles per hour. Admittedly, that’s challenging when you’re heavy, like an Atlas V rocket, because it takes a lot of energy to make a heavy thing go fast. But when you’re light, like a hydrogen molecule, even a little jolt of energy from a ray of sunlight can free you from Earth’s gravity.

For a planet, therefore, hanging on to an atmosphere becomes a somewhat delicate proposition. Being very massive helps, because it means that the planet’s gravity is stronger, so atmosphere molecules have to reach higher speeds to escape it. Being farther away from the star helps, too, because the starlight which reaches the planet is dimmer and less able to evaporate the atmosphere.

So what separates planets that successfully hang on to atmospheres from planets that don’t? And are the planets in our own Solar System, both “atmosphered” and not, a good guide to planets beyond? ...

The cosmic shoreline: the evidence that escape determines which planets
have atmospheres, and what this may mean for Proxima Centauri b
- Kevin J. Zahnle, David C. Catling
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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

How loud are neutron star mergers?

Postby bystander » Wed Apr 05, 2017 7:23 pm

How loud are neutron star mergers?
astrobites | 2017 Mar 29
Lisa Drummond wrote:
In September 2015, gravitational waves (GWs) were detected for the first time by LIGO (Laser Interferometer Gravitational Observatory). Gravitational waves are ripples in spacetime produced by the acceleration of massive objects. To read more about this monumental discovery and gravitational wave astronomy in general, see this astrobite. This first signal was generated in the final fraction of a second before two black holes merged into a single object. Neutron star mergers are also likely candidates for gravitational wave production and the authors of this paper are particularly interested in the emission of gravitational waves after the neutron stars have merged — they demonstrate that the first 10 ms of this post-merger phase is the most GW-“luminous” period of the neutron star binary evolution. ...

How loud are neutron star mergers? - Sebastiano Bernuzzi 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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Fast and Furious Planet Predictions

Postby bystander » Wed Apr 05, 2017 7:32 pm

Fast and Furious Planet Predictions
astrobites | 2017 Mar 30
Emily Sandford wrote:
Scientists are impatient people. Nobody has time to make an entire universe and watch it evolve for thirteen billion years to see what happens (do you have any idea how many emails you could answer in thirteen billion years?!), so instead, scientists simulate a smaller version that only takes a few months to mature.* Nobody has time to comb by hand through four years’ worth of Kepler telescope data to look for telltale planet shadows, so instead, scientists write a computer program that finds planets automatically. Nobody has time to manually rearrange the inside of a telescope to observe new stuff every five minutes, so scientists build robots to do it instead.

All of the above strategies work because computers are much faster than humans at doing small, repetitive tasks. But sometimes, even computers are too slow. For example, predicting the fate of a set of planets orbiting around a star can take a computer a couple of weeks. Nothing the computer is doing is complicated–it’s just tracking the motions of the planets and the star, subject to each others’ gravity. But it has to calculate the gravitational forces in question trillions of times, and, as former Federal Reserve Chair Alan Greenspan likes to say, trillions is lots.

Today’s authors wondered: Is there a faster way to figure out what will happen to those planets? ...

A Machine Learns to Predict the Stability of Tightly Packed Planetary Systems - Daniel Tamayo 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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Planet or Noise?

Postby bystander » Fri Apr 07, 2017 2:35 pm

Planet or Noise?
astrobites | 2017 Apr 04
Philipp Plewa wrote:
Recently, in August 2016, it was announced that a planet had been discovered in orbit around the nearest star to the Sun, Proxima Centauri, about 4 light years away from Earth. This planet, Proxima b (“Earth’s Nearest Neighbor”), is impossible to image directly with current technology, but we know it is there from the wobble of its host star. As both the planet and the star revolve around their common center of mass, the star’s radial (line-of-sight) velocity changes periodically. Generally, high-mass planets in close proximity to low-mass stars are easiest to detect. The Earth, for example, would only cause a minute change of at most 9 cm/s in the Sun’s radial velocity (RV), when observed from far away, but the configuration of the Proxima system results in a change as large as 1 m/s (see Figure 1). This effect is measurable using a stabilized, high-resolution spectrograph to track the Doppler shift of features in the stellar spectrum. ...

However, it is still a challenge to make sure that the measured signal is not spurious, but actually caused by a planet. For instance, the variability and magnetic activity of a red dwarf star like Proxima Centauri could alter its spectrum, causing apparent changes in the observed RV curve, that could be mistaken for the signature of a planet. ...

Proxima Centauri reloaded: Unravelling the stellar noise in radial velocities - M. Damasso, F. Del Sordo
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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Observing across the gravitational wave spectrum

Postby bystander » Fri Apr 07, 2017 2:56 pm

Observing across the gravitational wave spectrum
astrobites | 2017 Apr 04
Maria Charisi wrote:
A hundred years ago, Einstein published a new theory of gravity, the General Theory of Relativity. Massive objects, like the Sun, curve the geometry of the spacetime around them. The curvature of the spacetime then dictates the motion of other objects around them, e.g., the orbit of the Earth around the Sun. The theory predicts that when massive objects, like black holes (BHs) accelerate, they perturb the spacetime and produce gravitational waves, tiny ripples in spacetime that propagate outwards with the speed of light.

However, it wasn’t until only a year ago that this prediction was directly confirmed. On September 14, 2015, the Laser Interferometer Gravitational-Wave Observatory (LIGO) detected gravitational waves (GWs) from two colliding black holes (also see Abbott et al. 2016 for the discovery paper). This feat of science and engineering, decades in the making, opened a new window to observe the universe and signifies the beginning of a new exciting era in modern astronomy! ...

Prospects for Multiband Gravitational-Wave Astronomy after GW150914 - Alberto Sesana

viewtopic.php?t=35646
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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Distinguishing Populations of Hot Jupiters

Postby bystander » Fri Apr 07, 2017 3:05 pm

Samples and Statistics: Distinguishing Populations of Hot Jupiters in a Growing Dataset
astrobites | 2017 Apr 05
Jamila Pegues wrote:
The future of astronomy observations seems as bright as the night sky… and just as crowded! Over the next decade, several truly powerful telescopes are set to launch … That means we’re going to have a LOT of data on everything from black holes to galaxies, and beyond – and that’s in addition to the huge fields of data from the past decade that we’re already frolicking through now. It’s certainly far more data than any one astronomer (or even a group of astronomers) wants to analyze one-by-one – that’s why these days, astronomers turn more and more to the power of astrostatistics to characterize their data.

The author’s of today’s astrobite had that goal in mind. They explored a widely-applicable, data-driven statistical method for distinguishing different populations in a sample of data. In a sentence, they took a large sample of hot Jupiters and used this technique to try and separate out different populations of hot Jupiters, based on how the planets were formed, within their sample. Let’s break down exactly what they did, and how they did it …

Evidence for Two Hot Jupiter Formation Paths - Benjamin E. Nelson, Eric B. Ford, Frederic A. Rasio
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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

An Oscillating Heartbeat

Postby bystander » Fri Apr 07, 2017 3:15 pm

An Oscillating Heartbeat
astrobites | 2017 Apr 06
Mara Zimmerman wrote:
A heartbeat star is an unusual type of binary or two-star system. The individual stars in these systems are usually fairly large, and thus produce very strong tidal forces, which can shape the stars’ orbit. These tidal forces occur because the gravitational force exerted by one star on the other is not constant across it. The closer side of the stars are more attracted to each other than the farther sides. In heartbeat stars, these tides are so large that they can actually distort the shape of the star itself. As the two stars in the heartbeat system go through their point of closest passage, or periastron, their shape changes. The stars become more oblate, or somewhat football shaped, as they pass closely to each other, and then revert back to spherical shapes when the distance between them is big enough that the tidal forces subside. Since these dynamic tidal forces distort the shape of the stars, the light we see from the star is affected by this periodic changing shape. When we observe stars, we often keep track of the star’s brightness with respect to time in a light curve. A heartbeat star’s light curve has a small dip in its light curve when the stars change their shape at periastron; a light curve is shown in the upper section of Figure 1.

The dynamic tidal forces also can cause oscillations in the stars, which can occur throughout their orbit. Heartbeat stars are the largest known group of stars with tidally excited oscillations. In their light curve, we can see these oscillations occur as small sinusoidal dips during. The focus of this paper was a particular heartbeat star, ι Orionis, which has tidally induced pulsations and is currently the largest known heartbeat star. ...

The Most Massive Heartbeat: An In-depth Analysis of ι Orionis - Herbert Pablo 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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Preheating the IGM with Cosmic Rays

Postby bystander » Fri Apr 07, 2017 3:30 pm

Preheating the IGM with Cosmic Rays
astrobites | 2017 Apr 07
Joshua Kerrigan wrote:
Cosmic rays are those really cool high energy particles you may have heard about. They stream from beyond our solar system into our atmosphere causing cascades of even more particles. The source of these very high energy charged particles was for the longest time unknown. It wasn’t until recently in 2013 that the Fermi Gamma-ray Space Telescope was able to constrain the source of some cosmic rays to supernovae (SNe). While we can experience cosmic rays very locally in our atmosphere, they very well may have had an impact on larger cosmological scales in the form of heating the intergalactic medium (IGM). The IGM is the huge voids between galaxies that are filled mostly with some state of hydrogen.

Just like cosmic rays, the high(-ish) redshift universe still has a ton of uncertainties. In the context of the author’s work, high redshift refers to the period around the beginning of the epoch of reionization (EoR). The EoR is the point sometime between the Dark Ages and redshift z=6, when the neutral hydrogen in the universe was reionized by the UV radiation from the earliest stars and galaxies. To understand the physics going on during the EoR it’s helpful to know certain properties of the IGM. But why is knowing the initial temperature of the IGM important? Well because this period during the early stages of the EoR can also tell us a lot about how the very earliest galaxies formed, and the conditions for the beginning of reionization. ...

Do Cosmic Rays Heat the Early Intergalactic Medium? - Natacha Leite 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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Stuff Between the Stars: Gas, Dust, and … Asteroids?

Postby bystander » Fri Apr 14, 2017 5:24 pm

Stuff Between the Stars: Gas, Dust, and … Asteroids?
astrobites | 2017 Apr 10
Kerrin Hensley wrote:
In our current understanding of how planetary systems form, most of the material in the nascent protoplanetary disk is lost to interstellar space; the strong winds of young stars expel the raw material for planet formation to interstellar space, and gravitational interactions between planetesimals eject many would-be planets. In the Solar System, our best bet is that the giant planets migrated from their birthplaces to their current positions, disturbed the orbits of planetesimals—asteroids, comets, and possibly even other young planets—and launched them from the Solar System.

If giant planets in other planetary systems undergo similar migrations, interstellar space should be teeming with rogue planetesimals and debris. These wayward objects could encounter the Solar System and become entangled in the gravitational web of the Sun. In theory, their unusual trajectories or compositions would give clues as to their extrasolar origins. However, there are no confirmed discoveries of interstellar objects masquerading as members of our Solar System.

In this paper, the authors use the fact that we don’t observe interstellar objects (ISOs) to place an upper limit on the number density of these objects in the Milky Way. (Here, number density means the average number of ISOs per cubic astronomical unit.) Knowing the prevalence of ISOs is important because it can tell us more about the early stages of planet formation and our chances of finding interstellar interlopers in the Solar System. ...

An Observational Upper Limit on the Interstellar Number Density of Asteroids and Comets - Toni Engelhardt 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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Remedy to “Glitch” Size Anomaly

Postby bystander » Fri Apr 14, 2017 5:31 pm

Remedy to “Glitch” Size Anomaly
astrobites | 2017 Apr 11
Lisa Drummond wrote:
Rotating neutron stars (pulsars) can “spin-up”, or suddenly increase their rotation frequency, in an event called a glitch (see Figure 2 for a canonical example of a pulsar glitch). There is a scarcity of glitch observations, meaning that drawing statistical conclusions must be done with caution! Nevertheless, some of the observed properties of glitches are quite curious. In general, the distributions of observed glitch sizes are a power law (which would be consistent with the microscopic mechanisms believed to cause the glitches). However, the Vela pulsar, for example, typically has large glitches which occur fairly periodically, while recent analysis of the Crab pulsar indicates there is a deviation from a power law distribution for smaller glitch sizes. This paper tackles this discrepancy by showing that these deviations from power law distributions can be explained naturally, using a carefully chosen model that bridges microscopic and macroscopic scales. ...

The effect of superfluid hydrodynamics on pulsar glitch sizes and waiting times - Brynmor Haskell
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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Breaking Wind: Supernova feedback in galaxies

Postby bystander » Fri Apr 14, 2017 5:57 pm

Breaking Wind: Supernova feedback in galaxies
astrobites | 2017 Apr 12
Mia de los Reyes wrote:
Star formation in the universe peaked at a redshift of z~2 (when the universe was only ~3 billion years old), and it’s been downhill ever since. This simple observation sparked one of the biggest open questions about galaxies: why did star formation rates start dropping at z~2? What physical processes could shut off (or quench) star formation?

To make stars, you need gas—so one way to stop forming stars is to remove the gas from a galaxy. That’s exactly what galactic winds do. Galactic winds are massive outflows of gas and other material that are launched from galaxies. Simulations that include galactic winds agree well with many different observations, suggesting that galactic winds may be responsible for multiple phenomena: not just quenching star formation, but also making star formation inefficient in typical star-forming galaxies, and heating the material around galaxies.

However, despite the fact that galactic winds have been directly observed multiple times, we still don’t fully understand how they actually work. We do think that feedback (the injection of energy and momentum into the interstellar medium) from supernovae probably plays a role.

Today’s papers (yes, today you get two paper summaries for the price of one!) aim to study this in more detail. Both papers are by the same authors, who examine two different ways to simulate supernova feedback. ...

Supernova feedback in a local vertically stratified medium:
interstellar turbulence and galactic winds
- Davide Martizzi et al
How Supernovae Launch Galactic Winds - Drummond Fielding 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: 15966
Joined: Mon Aug 28, 2006 2:06 pm
Location: Oklahoma

Can we see neutrinos from the star-forming region Cygnus?

Postby bystander » Fri Apr 14, 2017 6:08 pm

Can we see neutrinos from the star-forming region Cygnus?
astrobites | 2017 Apr 13
Kelly Malone wrote:
The Cygnus X region is a particularly interesting region of the sky. Located in the Galactic plane and named because it is located in the Cygnus constellation, it is the largest star-forming region in the entire Milky Way. It contains massive clouds of molecular gas, which are important for star formation, and many young stars. Gamma rays (the most energetic form of electromagnetic radiation) have also been detected in the region by a number of other experiments, including Fermi-LAT and Milagro. In gamma rays, point sources and regions of extended emission make the area very confusing. One of the most interesting extended regions is known as the “Cygnus Cocoon“. ...

The Gamma-Ray Puzzle in Cygnus X: Implications for High-Energy Neutrinos - Tova M. Yoast-Hull 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


Return to “The Communications Center: Breaking Science News”

Who is online

Users browsing this forum: Brandwatch [Bot], CommonCrawl [Bot] and 0 guests