GW170817 Update: Surprises From First Gravitational Wave Observed Independently

“This is quite literally a physics gold mine!” said Masao Sako, with the University of Pennsylvania. For over a week now, the astronomy and astrophysics communities have been buzzing with the news of the latest gravitational wave discovery. And this discovery has been big. Four days before the Great American Solar Eclipse on August 21, […]

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New ‘Einstein Ring’ Discovered By Dark Energy Camera

The "Canarias Einstein Ring." The green-blue ring is the source galaxy, the red one in the middle is the lens galaxy. The lens galaxy has such strong gravity, that it distorts the light from the source galaxy into a ring. Because the two galaxies are aligned, the source galaxy appears almost circular. Image: This composite image is made up from several images taken with the DECam camera on the Blanco 4m telescope at the Cerro Tololo Observatory in Chile.

A rare object called an Einstein Ring has been discovered by a team in the Stellar Populations group at the Instituto de Astrofísica de Canarias (IAC) in Spain. An Einstein Ring is a specific type of gravitational lensing.

Einstein’s Theory of General Relativity predicted the phenomena of gravitational lensing. Gravitational lensing tells us that instead of travelling in a straight line, light from a source can be bent by a massive object, like a black hole or a galaxy, which itself bends space time.

Einstein’s General Relativity was published in 1915, but a few years before that, in 1912, Einstein predicted the bending of light. Russian physicist Orest Chwolson was the first to mention the ring effect in scientific literature in 1924, which is why the rings are also called Einstein-Chwolson rings.

Gravitational lensing is fairly well-known, and many gravitational lenses have been observed. Einstein rings are rarer, because the observer, source, and lens all have to be aligned. Einstein himself thought that one would never be observed at all. “Of course, there is no hope of observing this phenomenon directly,” Einstein wrote in 1936.

[embed]https://www.youtube.com/watch?v=H1bZcdE9zP0[/embed]

The team behind the recent discovery was led by PhD student Margherita Bettinelli at the University of La Laguna, and Antonio Aparicio and Sebastian Hidalgo of the Stellar Populations group at the Instituto de Astrofísica de Canarias (IAC) in Spain. Because of the rarity of these objects, and the strong scientific interest in them, this one was given a name: The Canarias Einstein Ring.

There are three components to an Einstein Ring. The first is the observer, which in this case means telescopes here on Earth. The second is the lens galaxy, a massive galaxy with enormous gravity. This gravity warps space-time so that not only are objects drawn to it, but light itself is forced to travel along a curved path. The lens lies between Earth and the third component, the source galaxy. The light from the source galaxy is bent into a ring form by the power of the lens galaxy.

When all three components are aligned precisely, which is very rare, the light from the source galaxy is formed into a circle with the lens galaxy right in the centre. The circle won’t be perfect; it will have irregularities that reflect irregularities in the gravitational force of the lens galaxy.

The objects are more than just pretty artifacts of nature. They can tell scientists things about the nature of the lens galaxy. Antonio Aparicio, one of the IAC astrophysicists involved in the research said, “Studying these phenomena gives us especially relevant information about the composition of the source galaxy, and also about the structure of the gravitational field and of the dark matter in the lens galaxy.”

Looking at these objects is like looking back in time, too. The source galaxy is 10 billion light years from Earth. Expansion of the Universe means that the light has taken 8.5 billion light years to reach us. That’s why the ring is blue; that long ago, the source galaxy was young, full of hot blue stars.

The lens itself is much closer to us, but still very distant. It’s 6 billion light years away. Star formation in that galaxy likely came to a halt, and its stellar population is now old.

The discovery of the Canarias Einstein Ring was a happy accident. Bettinelli was pouring over data from what’s known as the Dark Energy Camera (DECam) of the 4m Blanco Telescope at the Cerro Tololo Observatory, in Chile. She was studying the stellar population of the Sculptor dwarf galaxy for her PhD when the Einstein Ring caught her attention. Other members of the Stellar Population Group then used OSIRIS spectrograph on the Gran Telescopio CANARIAS (GTC) to observe and analyze it further.

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Next Time You’re Late To Work, Blame Dark Energy!

Illustration of the Big Bang Theory

Ever since Lemaitre and Hubble’s first proposed it in the 1920s, scientists and astronomers have been aware that the Universe is expanding. And from these observations, cosmological theories like the Big Bang Theory and the “Arrow of Time” emerged. Whereas the former addresses the origins and evolution of our Universe, the latter argues that the flow of time in one-direction and is linked to the expansion of space.

For many years, scientists have been trying to ascertain why this is. Why does time flow forwards, but not backwards? According to new study produced by a research team from the Yerevan Institute of Physics and Yerevan State University in Armenia, the influence of dark energy may be the reason for the forward-flow of time, which may make one-directional time a permanent feature of our universe.

Today, theories like the Arrow of Time and the expansion of the universe are considered fundamental facts about the Universe. Between measuring time with atomic clocks, observing the red shift of galaxies, and created detailed 3D maps that show the evolution of our Universe over the course of billions of years, one can see how time and the expansion of space are joined at the hip.

The question of why this is the case though is one that has continued to frustrate physicists. Certain fundamental forces, like gravity, are not governed by time. In fact, one could argue without difficulty that Newton’s Laws of Motion and quantum mechanics work the same forwards or backwards. But when it comes to things on the grand scale like the behavior of planets, stars, and entire galaxies, everything seems to come down to the Second Law of Thermodynamics.

This law, which states that the total chaos (aka. entropy) of an isolated system always increases over time, the direction in which time moves is crucial and non-negotiable, has come to be accepted as the basis for the Arrow of Time. In the past, some have ventured that if the Universe began to contract, time itself would begin to flow backwards. However, since the 1990s and the observation that the Universe has been expanding at an accelerating rate, scientists have come to doubt that this.

If, in fact, the Universe is being driven to greater rates of expansion – the predominant explanation is that “Dark Energy” is what is driving it – then the flow of time will never cease being one way. Taking this logic a step further, two Armenian researchers – Armen E. Allahverdyan of the Center for Cosmology and Astrophysics at the Yerevan Institute of Physics and Vahagn G. Gurzadyan of Yerevan State University – argue that dark energy is the reason why time always moves forward.

In their paper, titled “Time Arrow is Influenced by the Dark Energy“, they argue that dark energy accelerating the expansion of the universe supports the asymmetrical nature of time. Often referred to as the “cosmological constant” – referring to Einstein’s original theory about a force which held back gravity to achieve a static universe – dark energy is now seen as a “positive” constant, pushing the Universe forward, rather than holding it back.

To test their theory, Allahverdyan and Gurzadyan used a large scale scenario involving gravity and mass – a planet with increasing mass orbiting a star. What they found was that if dark energy had a value of 0 (which is what physicists thought before the 1990s), or if gravity were responsible for pulling space together, the planet would simply orbit the star without any indication as to whether it was moving forwards or backwards in time.

But assuming that the value of dark energy is a positive (as all the evidence we’ve seen suggests) then the planet would eventually be thrown clear of the star. Running this scenario forward, the planet is expelled because of its increasing mass; whereas when it is run backwards, the planet closes in on the star and is captured by it’s gravity.

In other words, the presence of dark energy in this scenario was the difference between having an “arrow of time” and not having one. Without dark energy, there is no time, and hence no way to tell the difference between past, present and future, or whether things are running in a forward direction or backwards.

But of course, Allahverdyan and Gurzadyan were also sure to note in their study that this is a limited test and doesn’t answer all of the burning questions. “We also note that the mechanism cannot (and should not) explain all occurrences of the thermodynamic arrow,” they said. “However, note that even when the dark energy (cosmological constant) does not dominate the mean density (early universe or today’s laboratory scale), it still exists.”

https://youtu.be/T1JknKr99_4

Limited or not, this research is representative of some exciting new steps that astrophysicists have been taking of late. This involves not only questioning the origins of dark energy and the expansion force it creates, but also questioning its implication in basic physics. In so doing, researchers may finally be able to answer the age-old question about why time exists, and whether or not it can be manipulated (i.e. time travel!)

Further Reading: Physical Review E

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An Old Glass Plate Hints at a Potential New Exoplanet Discovery

Polluted white dwarf

What’s the value to exoplanet science of sifting through old astronomical observations? Quite a lot, as a recent discovery out of the Carnegie Institution for Science demonstrates. A glass plate spectrum of a nearby solitary white dwarf known as Van Maanen’s Star shows evidence of rocky debris ringing the system, giving rise to a state only recently recognized as a ‘polluted white dwarf.’

First, let’s set the record straight. This isn’t, as many news outlets have reported, a new exoplanet discovery per se… or even an old pre-discovery of a known world. Astronomers have yet to nab a bona fide exoplanet orbiting Van Maanen’s Star. But obviously, something interesting is going on in the system that merits closer scrutiny.

The discovery: it all started when astronomer Jay Farihi of University College London requested early plate observations of the star from the Carnegie Institute. Dating from 1917, the plate shows the bar code-looking spectrum of the star. Astronomer Walter Adams captured the image from the Mount Wilson observatory, noting on the sleeve that the ‘ordinary’ looking star (Van Maanen’s Star wasn’t identified as a white dwarf until 1923) was perhaps merely a bit hotter than our own Sun.

But to Farihi’s trained eye, something was up with Van Maanen’s star. Specifically, it was the presence of the third set of absorption lines between the standard pair that showed evidence of calcium, magnesium and iron —materials that should have long since sunk down to the dense core of the degenerate star. Somehow, these heavy — remember, to an astronomer, the periodic table consists of hydrogen, helium and ‘metals’ — were being replenished from above.

“The unexpected realization that this 1917 plate from our archive contains the earliest recorded evidence of a polluted white dwarf system is just incredible,” says Carnegie Observatory director John Mulchaey in a recent press release. “And the fact that it was made by such a prominent astronomer in our history as Walter Adams enhances the excitement.”

The very fact that this crucial bit of evidence was sitting on a plate locked away in a vault for a decade is amazing. We now know that rocky rings of debris around white dwarf stars can give rise to what’s known as polluted white dwarfs. And where there’s debris, there are often planets. As newer exoplanet hunters such as TESS, JWST, WFIRST, LSST and the Gemini Planet Imager begin to scour the skies, we wouldn’t be at all surprised if Van Maanen’s Star turned out to have planets.

The Carnegie Institute maintains a collection of 250,000 glass plates taken from the Las Campanas, Mount Wilson and Palomar observatories dating back over century. These stellar spectra were painstakingly all examined by ‘Mk-1 eyeball,’ and enabled early astronomers such as Annie Jump Cannon and Henrietta Swan Leavitt to categorize stars by color and temperature and identify standard distance candles known as Cepheid variables. Both concepts are still used by astronomers today.

Finding Van Maanen’s Star

Located 14 light years distant, the high proper motion of Van Maanen’s star was first noted by Adriaan Van Maanen in 1917, the same year the plate was made. A high proper motion hints that a star is located near our solar neighborhood. Van Maanen’s Star is the third white dwarf discovered (after Sirius B and 40 Eridani B) and the third closest to our Sun (after Sirius B and Procyon B). Van Maanen’s Star also holds the distinction of being the closest solitary white dwarf to our solar system.

Located in the constellation Pisces, Van Maanen’s Star shines at magnitude +12.4. It also made our handy list of white dwarf stars for backyard telescopes.

Many false alarms of claimed exoplanet discoveries dot the history of 20th century astronomy. One of the most notorious were the claims of a planet orbiting Barnard’s Star, betrayed by supposed wobbles detected in its high proper motion. The first true modern exoplanet was actually a trio discovered orbiting the pulsar PSR B1257+12 in 1994. Ironically, though the exoplanet tally now sits at 2108 and counting, no known worlds have been identified around Barnard’s star.

What other future secrets do those old glass plates hold? “We have a ton of history sitting in our basement,” says Mulchaey in this month’s press release. “Who knows what other finds we might unearth in the future?”

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New Signal May Be Evidence of Dark Matter, Say Researchers

Dark matter is the architect of large-scale cosmic structure and the engine behind proper rotation of galaxies. It’s an indispensable part of the physics of our Universe – and yet scientists still don’t know what it’s made of. The latest data from Planck suggest that the mysterious substance comprises 26.2% of the cosmos, making it nearly five and a half times more prevalent […]

Mysterious Object “G2″ at Galactic Center is Actually Binary Star

A mysterious object swinging around the supermassive black hole in the center our galaxy has surprised astronomers by actually surviving what many thought would be a devastating encounter. And with its survival, researchers have finally been able to solve the conundrum of what the object – known as G2 — actually is. Since G2 was […]