Monthly Archives: October 2019

BLOOMINGTON, Ind. -- An astronomer renowned for her work on the black hole at the center of our galaxy will deliver a free public lecture at Indiana University.

Andrea Ghez will present the 2019 Edmondson Lecture, "The Monster at the Heart of Our Galaxy," at 7:30 p.m. Oct. 16 in Rawles Hall, Room 100, on the IU Bloomington campus, followed by a reception. Ghez is the Lauren Leichtman and Arthur Levine Chair of Astrophysics at UCLA.

The event is free and open to the public. No registration is required.

Ghez's work uses the world's most powerful telescopes and next-generation imaging technology to peer into the heart of the Milky Way. Her groundbreaking work has provided the best evidence to date for the existence of the supermassive black hole in the center of the galaxy. It also suggests that the center of most, if not all, other galaxies also harbor these massive objects in their core.

Earlier this year, Ghez's research led to the observation that our galaxy's central black hole -- named Sagittarius A -- has recently grown inexplicably "hungrier," consuming unusually large amounts of gas, dust and other interstellar debris, and flaring so brightly that astronomers briefly mistook it for a star.

During her lecture at IU, Ghez will explore the bizarre environment that surrounds this supermassive object -- which contains an estimated 4.3 million suns' worth of mass -- as well as discuss how her work tests Einstein's theory of relativity.

Ghez is a member of the National Academy of Sciences and a recipient of both the 2008 John D. and Catherine T. MacArthur Foundation Fellowship, commonly known as the "genius grant," and the 2012 Crafoord Prize from the Swedish Academy of Sciences. She holds a doctorate in astrophysics from the California Institute of Technology and a bachelor's degree in physics from MIT.

The annual F.K. Edmondson Astronomy Public Lectures were established to honor the memory of professor Frank Kelly Edmondson, a faculty member of the IU Bloomington Department of Astronomy from 1937 until his retirement in 1983, and chair of the department from 1944 until 1978. Edmondson is remembered not only for his contributions to the study of asteroids through the Indiana Asteroid Program but also for his dedication and service to IU and to the astronomical community. The Edmondson Lectures are endowed in Edmondson's honor by his family and friends.

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Famed astronomer to discuss supermassive black hole at the center of our galaxy - IU Newsroom

The team - led by Professor Joss Bland-Hawthorn from Australia - used data gathered by the Hubble Space Telescope to help understand the evolution of the galaxy. They say that a cataclysmic energy flare ripped through our galaxy some 3.5 million years ago. The massive blast of energy and radiation, known as a Sifter flare, was so powerful that its impact was felt 200,000 light-years from our galaxy.

The flare created two enormous "ionisation cones" that sliced through the Milky Way.

Mr Bland-Hawthorn, who also works at the University of Sydney said that "the flare must have been a bit like a lighthouse beam".

He added: Imagine darkness, and then someone switches on a lighthouse beacon for a brief period of time.

Professor Lisa Kewley, Director of ASTRO 3D said: A massive blast of energy and radiation came right out of the galactic centre and into the surrounding material.

This shows that the centre of the Milky Way is a much more dynamic place than we had previously thought. It is lucky were not residing there!

The discovery that the Milky Ways centre was more powerful than previously thought, is leading to new ideas on the evolution of the Milky Way.

Magma Guglielmo from the University of Sydney, said: "These results dramatically change our understanding of the Milky Way.

"We always thought about our Galaxy as an inactive galaxy, with a not so bright centre.

JUST IN'Monster' black hole 10 times size of Sun is lurking in galaxy

It is a barred spiral galaxy with a diameter between 150,000 and 200,000 light-years and is estimated to contain 100400 billion stars and more than 100 billion planets.

The oldest stars in the Milky Way are nearly as old as the Universe itself and thus probably formed shortly after the Dark Ages of the Big Bang.

Earlier this year scientists were astonished to discover that the giant blackhole at the centre of the Milky Way, Sagittarius A, had suddenly become active after years of being dormant.

The blackhole, which is 4.3 million times bigger than the Sun, has been feeding itself at an unprecedented rate, consuming huge amounts of gas, dust and anything in its vicinity.

Scientists became curious when they discovered it glowing twice as brightly as normal, with a surreal light emanating outside its point of no return beyond which no matter can escape.

Andrea Ghez, UCLA professor of physics and astronomy: "We have never seen anything like this in the 24 years we have studied the supermassive black hole.

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Space shock: Astronomers discover stunning 'lighthouse beam' with answers to start of life - Express.co.uk

In 1995, after years of effort, astronomers made an announcement: Theyd found the first planet circling a sun-like star outside our solar system. But that planet, 51 Pegasi b, was in a quite unexpected place it appeared to be just around 4.8 million miles away from its home star and able to dash around the star in just over four Earth-days. Our innermost planet, Mercury, by comparison, is 28.6 million miles away from the sun at its closest approach and orbits it every 88 days.

Whats more, 51 Pegasi b was big half the mass of Jupiter, which, like its fellow gas giant Saturn, orbits far out in our solar system. For their efforts in discovering the planet, Michel Mayor and Didier Queloz were awarded the 2019 Nobel Prize for Physics alongside James Peebles, a cosmologist. The Nobel committee cited their contributions to our understanding of the evolution of the universe and Earths place in the cosmos.

The phrase hot Jupiter came into parlance to describe planets like 51 Pegasi b as more and more were discovered in the 1990s. Now, more than two decades later, we know a total of 4,000-plus exoplanets, with many more to come, from a trove of planet-seeking telescopes in space and on the ground: the now-defunct Kepler; and current ones such as TESS, Gaia, WASP, KELT and more. Only a few more than 400 meet the rough definition of a hot Jupiter a planet with a 10-day-or-less orbit and a mass 25 percent or greater than that of our own Jupiter. While these close-in, hefty worlds represent about 10 percent of the exoplanets thus far detected, its thought they account for just 1 percent of all planets.

Still, hot Jupiters stand to tell us a lot about how planetary systems form and what kinds of conditions cause extreme outcomes. In a 2018 paper in the Annual Review of Astronomy and Astrophysics, astronomers Rebekah Dawson of the Pennsylvania State University and John Asher Johnson of Harvard University took a look at hot Jupiters and how they might have formed and what that means for the rest of the planets in the galaxy. Knowable Magazine spoke with Dawson about the past, present and future of planet-hunting, and why these enigmatic hot Jupiters remain important. This conversation has been edited for length and clarity.

What is a hot Jupiter?

A hot Jupiter is a planet thats around the mass and size of Jupiter. But instead of being far away from the sun like our own Jupiter, its very close to its star. The exact definitions vary, but for the purpose of the Annual Review article we say its a Jupiter within about 0.1 astronomical units of its star. An astronomical unit is the distance between Earth and the sun, so its about 10 times closer to its star or less than Earth is to the sun.

What does being so close to their star do to these planets?

Thats an interesting and debated question. A lot of these hot Jupiters are much larger than our own Jupiter, which is often attributed to radiation from the star heating and expanding their gas layers.

It can have some effects on what we see in the atmosphere as well. These planets are tidally locked, so that the same side always faces the star, and depending on how much the heat gets redistributed, the dayside can be much hotter than the nightside.

Some hot Jupiters have evidence of hydrogen gas escaping from their atmospheres, and some particularly hot-hot Jupiters show a thermal inversion in their atmosphere where the temperature increases with altitude. At such high temperatures, molecules like water vapor and titanium oxide and metals like sodium and potassium in the gas phase can be present in the atmosphere.

Between 2009 and 2018, NASA's Kepler space telescope discovered thousands of planets. But exoplanetsplanets outside the solar systemappeared in science fiction before they appeared in telescopes. Astronomers in the early decades of the twentieth century spent entire careers searching for planets in other stellar systems. In The Lost Planets, John Wenz offers an account of the pioneering astronomer Peter van de Kamp, who was one of the first to claim discovery of exoplanets.

What might explain how a planet ends up so close to its star?

There are three categories of models that people have come up with. One is that maybe these planets form close to their stars to begin with. Originally, people sort of dismissed this. But more recently, astronomers have been taking this theory a bit more seriously as more studies and simulations have shown the conditions under which this could happen.

Another explanation is that during the stage when the planetary system was forming out of a disk of gas and dust, the Jupiter was pulled in closer to its star.

The last explanation is that the Jupiter could have started far away from the star and then gotten onto a very elliptical orbit probably through gravitational interactions with other bodies in the system so that it passed very close to the host star. It got so close that the star could raise strong tides on the Jupiter, just like the moon raises tides on the Earth. That could shrink and circularize its orbit so that it ended up close to the star, in the position we observe.

Are there things we see in the planetary systems that have hot Jupiters that other systems dont have?

There are some trends. One is that most hot Jupiters dont have other small planets nearby, in contrast to other types of planetary systems we see. If we see a small hot planet, or if we see a gas giant thats a bit farther away from its star, it often has other planets nearby. So hot Jupiters are special in being so lonely.

The loneliness trend ties in to how hot Jupiters formed so close to their stars. In the scenario where the planet gets onto an elliptical orbit that shrinks and circularizes, that would probably wipe out any small planets in the way. That said, there are a few systems where a hot Jupiter does have a small planet nearby. With those, its not a good explanation.

Planetary systems with hot Jupiters often have other giant planets in the system farther away out beyond where the Earth is, typically. Perhaps, if hot Jupiters originated from highly eccentric orbits, those faraway planets are responsible for exciting their eccentricities to begin with. Or there could have been responsible planets that got ejected from the system in the process, so we dont necessarily have to still see them in the system.

Another big trend is that hot Jupiters tend to be around stars that are more metal-rich. Astronomers refer to metals as any element heavier than hydrogen or helium. Theres more iron and other elements in the star, and we think that this may affect the disk of gas and dust that the planets formed out of. There are more solids available, and that could facilitate forming giant planets by providing material for their cores, which would then accrete gas and become gas giants.

Having more metals in the system could enable the creation of multiple giant planets. That could cause the type of gravitational interaction that would put the hot Jupiter onto a high eccentricity orbit.

Hot Jupiters like 51 Pegasi b were the first type of planet discovered around sun-like stars. What led to their discovery?

It occurred after astronomers started using a technique called the radial velocity method to look for extrasolar planets. They expected to find analogs to our own Jupiter, because giant planets like this would produce the biggest signal. It was a very happy surprise to find hot Jupiters, which produce an even larger signal, on a shorter timescale. It was a surprising but fortuitous discovery.

Can you explain the radial velocity method?

It detects the motion of the host star due to the planet. We often think of stars sitting still and theres a planet orbiting around it. But the star is actually doing its own little orbit around the center of mass between the two objects, and thats what the radial velocity method detects. More specifically, it detects the doppler shift of the stars light as it goes in its orbit and moves towards or away from us.

One of the other common ways to find planets is the transit method, which looks for the dimming of a stars light due to a planet passing in front of it. Its easier to find hot Jupiters than smaller planets this way because they block more of the stars light. And if they are close to the star they transit more frequently in a given period of time, so were more likely to detect them.

In the 1990s, many of the exoplanets astronomers discovered were hot Jupiters. Since then, weve found more and different kinds of planets hot Jupiters are relatively rare compared with Neptune-sized worlds and super-Earths. Why is it still important to find and study them?

One big motivation is the fact that theyre out there and that they werent predicted from our theories of how planetary systems form and evolve, so there must be some major pieces missing in those theories.

Those missing ingredients probably affect many planetary systems even if the outcome isnt a hot Jupiter a hot Jupiter, we think, is probably an extreme outcome. If we dont have a theory that can make hot Jupiters at all, then were probably missing out on those important processes.

A helpful thing about hot Jupiters is that they are a lot easier to detect and characterize using transits and radial velocity, and we can look at the transit at different wavelengths to try to study the atmosphere. They are really helpful windows into planet characterization.

Hot Jupiters are still going to always be the planets we can probe in the most detail. So even though people dont necessarily get excited about the discovery of a new hot Jupiter anymore, increasing the sample lets us gather more details about their orbits, compositions, sizes or what the rest of their planetary system looks like, to try to test theories of their origins. In turn, theyre teaching us about processes that affect all sorts of planetary systems.

What questions are we going to be able to answer about hot Jupiters as the next-generation observatories come up, such as the James Webb Space Telescope and larger ground-based telescopes?

With James Webb, the hope is to be able to characterize a huge number of hot Jupiters atmospheric properties, and these might be able to help us test where they formed and what their formation conditions were like. And my understanding is that James Webb can study hot Jupiters super quickly, so it could get a really big sample of them and help statistically test some of these questions.

The Gaia mission will be really helpful for characterizing the outer part of their planetary systems and in particular can help us measure whether massive and distant planets are in the same plane as a transiting hot Jupiter; different theories predict differently on whether that should be the case. Gaia is very special in being able to give us three-dimensional information, when usually we have only a two-dimensional view of the planetary system.

TESS [the Transiting Exoplanet Survey Satellite space telescope] is going on right now and its discoveries are around really bright stars, so it becomes possible to study the whole system that has a hot Jupiter using the radial velocity method to better characterize the overall architecture of the planetary system. Knowing whats farther out will help us test some of the ideas about hot Jupiter origins.

TESS and other surveys also have more young stars in the sample. We can see what the occurrence rate and properties are of hot Jupiters closer to when they formed. That, too, will help us distinguish between different formation scenarios.

Theyre alien worlds to us, but what can hot Jupiters tell us about the origins of our own solar system? These days, many missions are concentrating on Earth-sized planets.

What were all still struggling to see is: Where does our solar system fit into a bigger picture of how planetary systems form and evolve, and what produces the diversity of planetary systems we see? We want to build a very complete blueprint that can explain everything from our solar system, to a system with hot Jupiters, to a system more typical of what [the retired space telescope] Kepler found, which are compact, flat systems of a bunch of super-Earths.

We still dont have a great explanation for why our solar system doesnt have a hot Jupiter and other solar systems do. Wed like some broad theory that can explain all types of planetary systems that weve observed. By identifying missing processes or physics in our models of planet formation that allow us to account for hot Jupiters, were developing that bigger picture.

Do you have any other thoughts?

The one thing I might add is that, as we put together all the evidence for our review, we found that none of the theories can explain everything. And that motivates us to believe that theres probably multiple ways to make a hot Jupiter so its all the more important to study them.

Knowable Magazine is an independent journalistic endeavor from Annual Reviews.

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What Astronomers Can Learn From Hot Jupiters, the Scorching Giant Planets of the Galaxy - Smithsonian

Early humans may have witnessed such an explosion over 3.5 million years ago - and it could happen again very soon according to researchers. Scientists call the cosmic gas orbs the Fermi bubbles and even though theyre a few million years old there is a mystery as to how the bubbles first formed. Researchers from the University of Sydney reconstructed a plausible explanation for the bubbles birth, putting it down to a gigantic explosion.

The Fermi bubbles were created by an epic flare of hot nuclear energy that shot out the galaxys poles roughly 3.5 million years ago.

A beam from the explosion shot into space for hundreds of thousands of light-years.

Lead study author Joss Bland-Hawthorn told Live Science, the effect would have shone out of the galaxys centre for 300,000 years.

Mr Bland-Hawthorn also noted that a similar explosion or flare could have occurred 10 million years ago and could well be heading towards Earth.

He said: It's plausible that one explosion took place 10 million years ago, and the jet is now arriving in our direction.

Speaking on the flare, the director of the Sydney Institute for Astronomy and his team calculated the blast may have been visible to early humans.

He said: It's an amazing thought that, when cave people walked the Earth, if they'd looked off in the direction of the galactic centre, they'd have seen some kind of giant ball of heated gas.

JUST IN:Building blocks of DNA could have been present in gas clouds in space

Researchers looked to the Hubble Space Telescope of the Magellanic Stream to date the explosion.

The Magellanic stream is a 600,000-light-year-wide arc of gas trailing behind two dwarf galaxies that orbit the Milky Way.

From the Earth, the Magellanic Stream spreads across half of the night sky as it surges through space some 200,000 light-years away.

It is still close enough for neighbouring galaxies to feel the heat of particularly violent eruptions from our galaxys central black hole, according to the researchers.

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While most of the hydrogen gas makes up the Magellanic Stream is very cold, recent Hubble observations have revealed at least three large regions where the gas is unusually hot.

Those regions, incidentally, align with the north and south poles of the Milky Way's galactic centre.

According to Mr Bland-Hawthorn, thats a clear sign that those hot regions were toasted by an enormous flare-up of charged particles beaming out of our galaxy and into deep space.

He said: This can only be done radiatively from the monster at the galaxy's nucleus.

The scientist and his colleagues showed how such an explosion of energy, known as a Seyfert flare, could blast out of the centre and reach all the way to the hottest regions of the Magellanic stream.

The team calculated the explosion must have occurred between 2.5 and 4.5million years ago - a time when humanitys early ancestors were already walking the Earth.

While early humans may have seen the mysterious flare overhead, Mr Bland-Hawthorn believes it is unlikely they were impacted by its energy due to the earth's protective atmosphere.

e added how it was good news for humanity as research suggests more Seyflert flares could be on their way.

The scientist stated that flares can get trapped in the immediate vicinity of the back holes that made them for millions of years.

He added: But I think the most powerful bursts from our Sun would be about the same power so, bad for satellites and space walkers, but our atmosphere protects life pretty well."

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Space discovery: Astronomers warn of colossal galaxy explosion heading towards Earth - Express.co.uk

Down on Earth around 3.5 million years ago, humanity was starting to take its earliest forms in some regions of Africa. At the same time, the sky was bursting with radiation from an explosive flare that took place in the center of the Milky Way.

An international team of astronomers recently found evidence of the explosion, the impact of which extended across 200,000 light-years and released a flash of energy that shone out into space through the two poles of our galaxy. And while humans probably couldnt see this flare, if there are any intelligent beings in the rest of the galaxy, they may have caught a glimpse.

The study, published on Sunday in The Astrophysical Journal, is based on observations made by the Hubble Space Telescope that caught the afterglow of the flare.

Gerald Cecil, Ph.D., professor of physics and astronomy at the University of North Carolina and co-author of the study, believes that the flare was caused by gas and shattered stars falling into the supermassive black hole at the center of the Milky Way.

We then see this glowing light, Cecil tells Inverse. Although we dont have a direct view of the explosion in the center, we see its reflective light.

The new study is based on a 2013 discovery of the Magellanic Stream, a stream of gas clouds that extends over the Milky Way, as shown in the video above. Light from distant quasars, massive and extremely bright cosmic objects, passed through the stream on its way to Earth. The composition of the arc, which removed some parts of the quasar light, led the team to suspect that something was heating and lighting up the gas stream.

What the team managed to observe was the fading remnant of the explosion, which was much brighter when it occurred 3.5 million years ago.

The fire is over, and were looking at the glowing coals, Cecil says. A lightbulb burning out.

The researchers estimate that the blast may have lasted for 300,000 years but is no longer active today based on mathematical models of how the heated gas de-energized.

The supermassive black hole in the Milky Way is always flickering, if an asteroid fell in instead of dust, you might get a flare that lasts for hours, Cecil says.

The new findings suggest that our galaxy is more active than we had initially thought it to be. The Milky Way is known to have some low level activity but, according to Cecil, this new research suggests that it was perhaps a million times more active only a few million years ago than what astronomers believed in the past.

Other galaxies have this behavior, Cecil says. It puts the Milky Way into the mainstream.

Considering that this event took place only a couple of million years ago, an insignificant amount of time in the life of a galaxy, means that it may be one of many such episodes that have occurred over the lifetime of the Milky Way.

If we start thinking about the cumulative effects of those radiation, we have to incorporate them in the models of whats going on in the Milky Way, Cecil says. That hasnt been done reliably.

The new study casts the Milky Way in a new, perhaps brighter, light, as well as the activity of the black hole at its center, if it is in fact the culprit behind this relatively recent explosion. The team behind the research hopes to get a better understanding of the duration of the flare, and whether it flared back up again during that period or continued to fade gradually.

Another aspect of the findings that Cecil points out is that this galactic event may have been observed by other inhabitants of the Milky Way, which he strongly believes exist, and essentially synchronized everybodys clock to a point of reference in the galaxys timescale.

Here is an event thats galaxy wide, for wherever they are in the galaxy, Cecil says. There was an event, one that everyone could see.

Abstract: There is compelling evidence for a highly energetic Seyfert explosion (105657 erg) that occurred in the Galactic Centre a few million years ago. The clearest indications are the x-ray/-ray 10 kpc bubbles identified by the Rosat and Fermi satellites. In an earlier paper, we suggested another manifestation of this nuclear activity, i.e. elevated H emission along a section of the Magellanic Stream due to a burst (or flare) of ionizing radiation from Sgr A*. We now provide further evidence for a powerful flare event: UV absorption line ratios (in particular CIV/CII, Si IV/Si II) observed by the Hubble Space Telescope reveal that some Stream clouds towards both galactic poles are highly ionized by a source capable of producing ionization energies up to at least 50 eV. We show how these are clouds caught in a beam of bipolar, radiative ionization cones from a Seyfert nucleus associated with Sgr A*. In our model, the biconic axis is tilted by about 15 from the South Galactic Pole with an opening angle of roughly 60. For the Stream at such large Galactic distances (D > 75 kpc), nuclear activity is a plausible explanation for all of the observed signatures: elevated H emission and H ionization fraction (xe > 0.5), enhanced CIV/CII and Si IV/Si II ratios, and high CIV and Si IV column densities. Wind-driven shock cones are ruled out because the Fermi bubbles lose their momentum and energy to the Galactic corona long before reaching the Stream. Our time-dependent Galactic ionization model (stellar populations, hot coronal gas, cloud-halo interaction) is too weak to explain the Streams ionization. Instead, the nuclear flare event must have had a radiative UV luminosity close to the Eddington limit (fE 0.1 1). Our time-dependent Seyfert flare models adequately explain the observations and indicate the Seyfert flare event took place To = 3.5 1 Myr ago. The timing estimates are consistent with the mechanical timescales needed to explain the x-ray/-ray bubbles in leptonic jet/wind models ( 2 8 Myr).

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Astronomer who saw Milky Way black hole flare thinks ancient aliens saw it - Inverse