Universe Today

January 9, 2008December 26, 2015 by Fraser Cain

There May Be Hundreds of Rogue Black Holes in the Milky Way

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Uh oh, this doesn’t sound good. It turns out there could be hundreds of rogue black holes, each weighing thousands of times the mass of the Sun, hurtling though the Milky Way. Oh, and they’d be almost impossible to spot.

Vanderbilt astronomer Kelly Holley-Bockelmann presented the results of a supercomputer simulation at the Winter meeting of the American Astronomical Society.

The research focused on modeling the controversial “intermediate mass” black holes. These are the theorized black holes that should form within globular star clusters, containing a few thousand times the mass of the Sun; much heavier than the stellar mass black holes, but a fraction the mass of the supermassive variety. Astronomers have been looking for them for years, and even after all that searching, they’ve only come up with a couple of tentative candidates. So maybe these black holes are all around us, kicked out of their globular clusters, free to wander the galaxy.

Scientists have been hard at work modeling what might happen as two black holes merge. This is the realm where Einstein’s theory of relativity comes into play because of the tremendous forces and masses involved.

The simulations predict that as two black holes come together to form a new, even more massive black hole, it should receive a tremendous “kick” because of the conservation of momentum. The newly formed black hole should actually get kicked right out of the globular cluster in a random direction as fast as 4,000 kilometres a second.

Since the escape velocity of a globular cluster is only about 100 km/s, that black hole won’t ever come back to its home.

Now, if this research is true, the roughly 200 globular clusters in the Milky Way might have spawned intermediate-sized black holes, and then ejected them in random directions into the galaxy. There are probably several hundred black holes wandering invisibly through our galaxy.

Now don’t get too scared, “these rogue black holes are extremely unlikely to do any damage to us in the lifetime of the Universe,” soothed Holly-Bockelmann. “Their danger zone, the Schwarzschild radius, is really tiny, only a few hundred kilometers. There are far more dangerous things in our neighborhood.”

Original Source: Vanderbilt News Release

January 9, 2008December 26, 2015 by Fraser Cain

If You Crashed Neptune and Jupiter Together…

Our early Solar System was a violent place. For hundreds of millions of years, large planetoids smashed together, forming larger and larger planets. This same process is happening in other star systems right now. In fact, astronomers have discovered a system where a Neptune-sized object and a Jupiter-sized object might have just smashed together. Ouch.

This newly discovered planet orbits a 25-Jupiter-mass brown dwarf located about 170 light-years away. Computer models show that the brown dwarf is very young, probably only 8 million years old. This means that its planetary companion should be the same age.

And here’s why they think it’s the result of a massive collision. At its current age, the planet should have cooled down to a temperature of about 1000 Kelvin. But recent observations show that it’s actually around 1600 Kelvin. So something heated it up.

That something might have been a planetary collision.

“Most, if not all, planets in our solar system were hit early in their history. A collision created Earth’s moon and knocked Uranus on its side,” explained Eric Mamajek, of the Harvard-Smithsonian Center for Astrophysics. “It’s quite likely that major collisions happen in other young planetary systems.”

An object this size should radiate its heat away over the course of 100,000 years, so this collision must have happened relatively recently.

That’s a pretty exciting possibility, but there are some more conservative possibilities as well. Other astronomers have proposed that the planetary companion is actually much smaller, only the size of Saturn. So it would have a smaller surface area radiating all the detected energy.

If this technique works out, astronomers could just take the temperature of planets in young star systems, and calculate just how long it’s been since they were impacted. “Hot, post-collision planets might be a whole new class of objects we will see with the Giant Magellan Telescope.”

Original Source: CfA News Release

January 9, 2008December 26, 2015 by Fraser Cain

Earth, Barely Habitable?

Our home planet has been often described in glowing, nurturing terms. A cradle for life, right in the goldilocks zone. But our planet is actually right on the edge of habitability. If it were any smaller, and a little less massive, plate tectonics might never have gotten started. It turns out, life needs plate tectonics.

Astronomers at the Harvard-Smithsonian Center for Astrophysics announced their research today at the Winter meeting of the American Astronomical Society. According to the team, plate tectonics only really get going when a planet gathers enough mass. And the Earth has just barely enough mass to enjoy plate tectonics.

“Plate tectonics are essential to life as we know it,” said Diana Valencia of Harvard University. “Our calculations show that bigger is better when it comes to the habitability of rocky planets.”

When a planet reaches a large enough size, huge chunks of the planet’s surface can float atop an ocean of boiling magma. These plates spread apart and crash into one another, lifting up gigantic mountain ranges like the Himalayas.

And without plate tectonics, we wouldn’t be here. The process enables complex chemistry and recycles carbon dioxide, which acts like a blanket to keep the Earth warm and hospitable for life. Carbon dioxide is locked into rocks, and then returned to the atmosphere when the rocks melt. Without this cycle, carbon dioxide would get locked away in rocks forever.

The researchers examined what would happen on different rocky planets. They looked at a range of planets, smaller than our planet, up to the so-called “super-Earths” – planets twice our size with 10 times the mass. Any bigger than that, and you start to get a gas planet.

According to their calculations, the Earth is barely habitable. If you get a planet with more mass, the plate tectonics really get rolling, and the carbon cycle becomes really active. A super-Earth could have globe-spanning rings of fire, bursting with hot springs and geysers. Life would have every opportunity to get started.

Of course, if we tried to visit a super-Earth, we’d find the gravity uncomfortable. We’d experience 3 times the gravity trying to walk around on the surface of the planet. Oh, my back.

But for native life forms, it would be paradise.

Original Source: CfA News Release

January 9, 2008December 26, 2015 by Fraser Cain

Hidden Quasars – Found!

Quasars are some of the brightest objects in the Universe. Just a single quasar can blaze more than a hundred times more brightly than our entire Milky Way galaxy. It turns out, though, that some of the brightest quasars in the Universe are hidden, cloaked behind a shroud of gas and dust. But now researchers have developed a technique to find the galaxies hiding these bright quasars. It turns out, they’re everywhere, we just couldn’t see them.

This blazing material surrounding a supermassive black hole is a quasar. The relatively tiny region around a black hole can blaze more than a hundred times as brightly as our own Milky Way galaxy. But there’s a paradox. The more powerful the quasar, the better a job it can do to hide itself within a shroud of gas and dust.

To see the hidden quasars, you can’t look in the visible spectrum. You need to use a wavelength that isn’t obscured by gas and dust, such as infrared and X-rays. However, previous surveys in these wavelengths have only revealed small portions of the sky.

Astronomers from Princeton and the Institute for Advanced Study announced today that they have developed a technique to see the telltale signs that a galaxy contains a bright quasar – without having to perform an extensive survey in these other wavelengths. By sifting through the Sloan Digital Sky Survey, looking for very special characteristics of the light coming from a galaxy, the team uncovered 887 hidden quasars; the largest number ever detected.

“We determined how common hidden quasars are, especially the most luminous ones. Perhaps more interestingly, we determined how common they are relative to normal quasars,” said team member Nadia Zakamska, a NASA Spitzer Fellow at the Institute for Advanced Study in Princeton.

“We found that hidden quasars make up at least half of the quasars in the relatively recent Universe, implying that most of the powerful black holes in our neighborhood had previously been unrecognized.”

This means that there are many hidden quasars out there. And it also means that quasars are much more efficient at converting matter into light than astronomers previously realized. In fact, most of the light released by quasars is probably absorbed by intervening gas and dust.

In other words, even though quasars are incredibly bright objects, blazing with hundreds of times the light of an entire galaxy, that’s probably just the tip of the iceberg.

They’re much much brighter.

Original Source: SDSS News Release

January 9, 2008December 26, 2015 by Fraser Cain

The Universe Held a Party, and We Missed It

It’s too bad. Life evolved here on Earth after the Universe’s big parties already ended. Sure, there’s the occasional galaxy merger, and we’ve got a few regions of furious star formation here in the Milky Way. But billions of years ago, galaxies were banging and crashing together, leading to vast eras of star formation. In fact, in the first 25% of the Universe’s history more than half of the galaxies were in the midst of one of these cosmic collisions.

This was the research unveiled by University of Texas at Austin researcher Shardha Jogee. She and her team surveyed a region of space approximately the size of the Moon using the Hubble Space Telescope. Within this region, they found thousands of bright galaxies in the process of merging with one another.

Kyle Penner, from the University of Texas at Austin explained how they saw the mergers, “with Hubble’s spectacular resolution, we could discern amazing tell-tale clues of the mergers and interactions – huge tails, warps, ripples, double nuclei – in galaxies billions of light-years away.”

They used ground-based observatories to determine the galaxies age, and then analyzed these galaxies using the Spitzer Space Telescope to track the rate of star formation in each galaxy. Normally hidden in visible light, the stellar nurseries are revealed in Spitzer’s infrared view which can peer right through the obsuring gas and dust.

If you take two nice neat spiral galaxies and smash them together, you get a mess. The galaxies are torn apart, tidal tails of stars are flung out in all directions. The stars “forget” their original orbits and circle the central point of gravity in all directions. Two beautiful spirals become an elliptical galaxy.

They found that when the Universe was only 2.1 billion years, over 40% of massive galaxies were strongly interacting and merging. And then, over each billion-year interval, only 10% of galaxies are involved in strong interactions and mergers. During these periods, the galactic interactions collapsed vast clouds of gas, creating periods of star formation.

The researchers turned up a few surprises. They found that all this galactic interaction actually only increased the rates of star formation in the host galaxies by a mere factor of 2 or 3. They also turned up a large number of “bulgeless” galaxies. These should be very rare, size a past major merger in the life of a galaxy always builds a bulge.

Just imagine what the Universe would have looked like 7 billion years ago; every where you looked galaxies would have been crashing together, spraying stars in all directions. Galaxies would have blazed with regions of active star formation.

It must have been quite the party.

Original Source: University of Texas at Austin News Release

January 9, 2008December 26, 2015 by Fraser Cain

Beautiful View of the Cygnus Loop

Let’s stop all this science talk for a second and just enjoy this amazing photograph. It’s an image of Pickering’s Triangle; a portion of the Cygnus Loop supernova remnant, located about 1,500 light-years from Earth. This is the same remnant that contains the famous Veil Nebula. Astronomers think that the supernova detonated about 5-10,000 years ago, and the nebula now stretches across more than six full Moons of width across the sky.

The image was captured by the 64-pixel NOAO Mosaic-1 imager connected to the National Science Foundation’s Mayall 4-metre telescope at Kitt Peak National Observatory, and was released at the American Astronomical Society meeting in Austin.

Of all the pictures I’ve seen at the conference so far, I’ve got to say this one’s my favourite. And it just gets better in higher resolutions. I’ve made it my desktop background… and so should you.

Here’s a link to a smaller resolution. And if you want a really big version, here’s one with 4000 x 2053 pixels.

Original Source: NOAO News Release

January 8, 2008December 26, 2015 by Fraser Cain

Massive Disk Galaxies Collapsed From a Single Cloud of Gas

Here’s the traditional thinking. The grand spiral galaxies like our own Milky Way took a long time to come together through a series of mergers between smaller galaxies. But what what if that’s totally wrong? Instead of evolving slowly over time, some of the largest galaxies came together quickly, forming all at once when enormous clouds of gas and dust collapsed directly.

That’s the thinking from researchers in Hawaii and California. Using the Hubble Space Telescope, they captured images of massive, spiraling galaxies at tremendous distances away. If the theory is true – that large galaxies were built up over time through mergers with smaller galaxies – you would expect to see the wreckage from galaxy mergers. With Hubble they looked back to a time when the Universe was very young, just a fifth of its current age.

And that’s not what they saw.

“We expected these galaxies to look similar to the football-shaped elliptical galaxies that we see at the centers of dense groups of galaxies today, where mergers are common. We were quite surprised to find that many of them appear instead to be flattened, rotating disks of ordered material,” explained Elizabeth McGrath from the University of California, Santa Cruz.

These disk galaxies are pancake-shaped, and the stars orbit around the galactic centre, just like planets orbiting a star. This kind of galaxy is more likely to form from a single massive cloud of gas and dust that collapsed under its own gravity. The galaxies that form through successive mergers would be much more chaotic looking with the disk warped through the gravitational interactions.

They observed 7 ancient galaxies, some of the first to form in the Universe. 4 of these galaxies had that nice stable, disklike shape, meaning they formed fast from a single cloud of gas.

Of course, through subsequent interactions with other galaxies, these nice clean galactic disks will get warped and twisted. In the end, all of these large galaxies will look like the jumbled elliptical galaxies we see today.

Original Source: IfA News Release

January 8, 2008December 26, 2015 by Fraser Cain

Time Lapse Animation of Galaxy Jets

The Academy Awards doesn’t have a category for “Best Galaxy Jet in a Leading Role”, and that’s too bad. If they did give such an Oscar, a series of new movies captured by the National Science Foundation’s Very Large Baseline Array would make some fine nominees. Astronomers revisited the same galaxies for 15 years, capturing images of jets blasting out from their supermassive black holes. These images were then stitched together into a series of timelapse movies.

The jet study is known as MOJAVE (Monitoring of Jets in Active galactic nuclei with VLBA Experiments). This is actually the successor to a previous study that tracked more than 200 jets from 1994 to 2002.

The new survey used the National Science Foundation’s Very Long Baseline Array (VLBA). They made images of 200 galactic jets at regular intervals, tracking their motions and studying their magnetic-field properties. For 100 of these jets, they actually produced time-lapse movies, allowing them to show the speed and direction of motion.

Where do the jets come from? They originate around the supermassive black holes that lurk at the hearts of galaxies. Even though they weigh in with hundreds of millions of times the mass of the Sun, there’s only so much material they can gobble up at any one time. The material falls into a circular accretion disk orbiting the black hole. The magnetic fields generated by the rotating black hole propels material out jets from the poles of the disk.

With long-term observations like this, the astronomers have been able to see how the jets change over time. Many have remained constant, but some have been surprisingly active. For some galaxies, the jets have brightened or dimmed over time. Others have changed course as the supermassive black hole’s magnetic field wrenched the particles into a new direction. Jets have been seen to split apart.

If you want to see what a movie of a galactic jet looks like, check out this link for some animations.

Original Source: Purdue News Release

January 8, 2008December 26, 2015 by Fraser Cain

A Powerful Blast From the Distant Past

As sure as the Sun rises, you can expect that astronomers are going to beat their records. Today, we can wave goodbye to the record for the most distant short-duration gamma ray burst. Astronomers working with NASA have announced a newly discovered explosion that occurred 7.4 billion light years away. That’s nearly double the distance to the previous record holder.

Gamma ray bursts are the most powerful explosions in the Universe, and they come in two varieties: short and long. The long variety are thought to be when an extremely massive star collapses into a black hole. The short variety are different, and probably occur when two compact objects, like neutron stars collide together.

This newly announced burst is in that second variety; a short burst. As the two neutron stars collide, they rapidly collapse into a black hole, and release a tremendous amount of energy into two counterflowing beams.

GRB 070714B was the second burst detected on July 14th, 2007 by NASA’s Swift Satellite. Its energy signature matched the short burst variety, and the burst of energy lasted a mere 3 seconds. Astronomers scrambled to perform followup observations with ground-based telescopes, and were able to track the fading afterglow. This allowed them to identify the blast’s host galaxy.

With the host galaxy known, the astronomers were able to measure its distance, and confirm that yes, this is the most distant short-duration gamma ray burst ever seen; doubling the distance of the previous record holder.

There are a few mysteries outstanding. GRB 070714B seems to have 100 times as much energy as you would expect for a short duration gamma ray burst. Perhaps this is a merger between a neutron star and a black hole, or maybe the ejected beams happened to be pointing right at the Earth. That would make it seem more energetic, like when someone shines a flashlight directly at you.

Original Source: NASA News Release

January 8, 2008January 24, 2021 by Fraser Cain

A Snapshot of NASA’s Science Plans

As you’re probably aware, NASA has a lot of robotic explorers out there in space, and even more the works here on Earth. I was actually surprised to learn that they have 53 mission already in operation, and another 41 missions in development. But with the human exploration of the Moon charging forward, the robotic exploration missions are taking a bit of a hit. NASA administrator, Mike Griffin dropped the bad news in a press conference at the American Astronomical Society today. And then Associate Administrator Alan Stern picked up the pieces in a followup town hall meeting, explaining to scientists how they plan to move forward from here.

I won’t go too deeply into Mike Griffin’s presentation. Phil and Pamela captured the essence of the presentation quite nicely. Griffin hit us with the bad news about the deep cuts coming, and begged the community to try and stick together during these tough times.

After Griffin’s presentation, NASA Associate Administrator Alan Stern presented the state of robotic exploration and how the budget cuts will play out.

In opening up his presentation, Stern admitted that the Science Mission Directorate exploration program had suffered many setbacks, most of them self-inflicted through cost overruns. Over the last 5 years, the overruns have amounted to $5.7 billion. If these projects hadn’t gone over budget, the recent budget cuts might not have been necessary at all.

Stern emphasized his focus on holding project managers accountable for their budgets. Speaking to the research scientists in attendance at the town hall meeting, Stern said, “we’re going to get the project managers to toe the line and deliver projects on time and on budget so that we don’t mortgage your future.”

Of course, it’s unrealistic to think that there won’t be cost overruns. Overbudget and project management just go hand-in-hand.

The bulk of Stern’s presentation focused on how they would recover from the budget cuts. How they plan to rearrange the schedule to keep the spacecraft launching. This will be especially difficult with the James Webb Next Generation Telescope the lion’s share of the Science Mission Directorate’s budget.

Since April, though, they were able to get 5 new missions in the pipeline. And in one dramatic slide, Stern showed how the future mission pipeline has been improved. Many missions have been brought forward to launch several years ahead of schedule. Many mission will be launching this year, and the future launch schedule looks pretty decent too.

In responding to questions from the audience, Stern said that they have to deal with the current situation, and can’t hope for budget increases from Congress, “hope is not a strategy. We can hope that the Science Mission Directorate’s budget will be increased, but that’s not a strategy.”

Perhaps one of the most significant cuts in the last few years is the cancelation of the Terrestrial Planet Finder. This future mission would have had the power to observe atmospheres on Earth-sized planets orbiting other stars. Seeing ozone in the atmosphere of a distant planet would be a strong indication that there’s life there.

Although TPF has been scrapped, Stern said that the Science Mission Directorate is still committed to the search for exoplanets. One of these missions, the SIM Planet Finder has been mandated for completion by congress. With all the recent budget cuts, the money to work on SIM has to come from somewhere. And that somewhere is going to be other science missions.

Original Source: SMD Homepage