Heavy Stellar Traffic Sends Dangerous Comets Our Way

New image of comet ISON
Comet C/2012 S1 (ISON) as imaged by TRAPPIST–South national telescope at ESO’s La Silla Observatory in 2013 (TRAPPIST/E. Jehin/ESO)

Sixty-six million years ago Earth underwent a cataclysmic change. Back then, our planet was dominated by dinosaurs, but a mass extinction event hastened the demise of these huge reptiles and paved the way for the mammalian takeover. Though there is some debate as to whether the extinction of the dinosaurs was triggered by an isolated disaster or a series of disasters, one event is clear — Earth was hit by a massive comet or asteroid and its impact had global ramifications.

The leading theory is that a massive comet slammed into our planet, creating the vast Chicxulub Crater buried under the Yucatán Peninsula in Mexico, enshrouding the atmosphere in fine debris, blotting out the sun for years.

Although there is strong evidence of comet impacts on Earth, these deep space vagabonds are notoriously hard to track, let alone predict when or how often they may appear. All we know is that they are out there, there are more than we thought, they are known to hit planets in the solar system and they can wreak damage of apocalyptic proportions.

Now, using fresh observations from the European Space Agency’s Gaia mission, astronomer Coryn Bailer-Jones, who works at the Max Planck Institute for Astronomy in Munich, Germany, has added an interesting component to our understanding of cometary behavior.

Stellar Traffic

Long-period comets are the most mysterious — and troubling — class of comet. They will often appear from nowhere, after falling from their distant gravitational perches, zoom through the inner solar system and disappear once more — often to be never seen again. Or they hit something on their way through. These icy bodies are the pristine left-overs of our solar system’s formation five billion years ago, hurled far beyond the orbits of the planets and into a region called the Oort Cloud.

In the Oort Cloud these ancient masses have remained in relative calm far from the gravitational instabilities close to the sun. But over the eons, countless close approaches by other stars in our galactic neighborhood have occurred, causing very slight gravitational nudges to the Oort Cloud. Astronomers believe that such stellar encounters are responsible for knocking comets from this region, sending them on a roller-coaster ride to the inner solar system.

The Gaia mission is a space telescope tasked with precisely mapping the distribution and motion of stars in our galaxy, so Bailer-Jones has investigated the rate of stellar encounters with our solar system. Using information in Gaia’s first data release (DR1), Bailer-Jones has published the first systematic estimate of stellar encounters — in other words, he’s estimated the flow of stellar traffic in the solar system’s neighborhood. And the traffic was found to be surprisingly heavy.

In his study, to be published in the journal Astronomy & Astrophysics, Bailer-Jones estimates that, on average, between 490 and 600 stars will come within 16.3 light-years (5 parsecs) of our sun and 19-24 of them will come within 3.26 light-years (1 parsec) every million years.

According to a press release, all of these stars will have some gravitational effect on the solar system’s Oort Cloud, though the closest encounters will have a greater influence.

This first Gaia data release is valid for five million years into the past and into the future, but astronomers hope the next data release (DR2) will be able to estimate stellar traffic up to 25 million years into the past and future. To begin studying the stellar traffic that may have been responsible for destabilizing the dinosaur-killing comet that hit Earth 66 million years ago will require a better understanding of the mass distribution of our galaxy (and how it influences the motion of stars) — a long-term goal of the Gaia project.

An Early Warning?

Spinning this idea into the future, could this project be used to act as an early warning system? Or could it be used to predict when and where a long-period comet may appear in the sky?

In short: “No,” Bailer-Jones told Astroengine via email. “Some close stellar encounters will for sure shake up the Oort cloud and fling comets into the inner solar system, but which comets on which orbits get flung in we cannot observe.”

He argues that the probability of comets being gravitationally nudged can be modeled statistically, but this would require a lot of assumptions to be made about the Oort Cloud, a region of space that we know very little about.

Also, the Oort Cloud is located well beyond the sun’s heliosphere and is thought to be between 50,000 and 200,000 AU (astronomical units, where 1 AU is the average distance between the sun and the Earth) away, so it would take a long time for comets to travel from this region, creating a long lag-time between stellar close approach and the comet making an appearance.

“Typically it takes a few million years for a comet to reach the inner solar system,” he added, also pointing out that other factors can complicate calculations, such as Jupiter’s enormous gravity that can deflect the passage of comets, or even fling them back out of the solar system again.

This is a fascinating study that goes to show that gravitational perturbations in the Oort Cloud are far from being rare events. A surprisingly strong flow of stellar traffic will constantly rattle otherwise inert comets, but how many are dislodged and sent on the long journey to the solar system’s core remains a matter for statistics and probability.

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The Sun Just Unleashed a Massive Explosion — at Mars

cme_c3_anim
NASA/ESA/SOHO

The Earth and Mars are currently on exact opposite sides of the sun — a celestial situation known as “Mars solar conjunction” — a time when we have no way of directly communicating with satellites and rovers at the Red Planet. So, when the Solar and Heliospheric Observatory (SoHO) spotted a huge (and I mean HUGE) bubble of superheated plasma expand from the solar disk earlier today (July 23), it either meant our nearest star had launched a vast coronal mass ejection directly at Earth or it had sent a CME in the exact opposite direction.

As another solar observatory — the STEREO-A spacecraft — currently has a partial view of the other side of the sun (it orbits ahead of Earth’s orbit, so it can see regions of the sun that are out of view from our perspective), we know that this CME didn’t emanate from the sun’s near side, it was actually launched away from us and Mars will be in for some choppy space weather very soon.

It appears the CME emanated from active region (AR) 2665, a region of intense magnetic activity exhibiting a large sunspot.

“If this explosion had occurred 2 weeks ago when the huge sunspot was facing Earth, we would be predicting strong geomagnetic storms in the days ahead,” writes Tony Phillips of Spaceweather.com.

CMEs are magnetic bubbles of solar plasma that are ejected at high speed into interplanetary space following a magnetic eruption in the lower corona (the sun’s lower atmosphere). From STEREO-A’s unique vantage point, it appears the CME detected by SoHO was triggered by a powerful solar flare that generated a flash of extreme-ultraviolet radiation (possibly even generating X-rays):

stereoa
Observation by STEREO-A of the flaring event that likely triggered today’s CME (NASA/STEREO)

When CMEs encounter Earth’s global magnetic field, the radiation environment surrounding our planet increases, posing a hazard for satellites and unprotected astronauts. In addition, if the conditions are right, geomagnetic storms may commence, creating bright aurorae at high latitudes. These storms can overload power grids on the ground, triggering mass blackouts. Predicting when these storms will occur is of paramount importance, so spacecraft such as SoHO, STEREO and others are constantly monitoring our star’s magnetic activity deep inside the corona and throughout the heliosphere.

Mars, however, is a very different beast to Earth in that it doesn’t have a strong global magnetosphere to shield against incoming energetic particles from the sun, which the incoming CME will be delivering very soon. As it lacks a magnetic field, this CME will continue to erode the planet’s thin atmosphere, stripping some of the gases into space. Eons of space weather erosion has removed most of the Martian atmosphere, whereas Earth’s magnetism keeps our atmospheric gases nicely contained.

When NASA and other space agencies check in with their Mars robots after Mars solar conjunction, it will be interesting to see if any recorded the space weather impacts of this particular CME.

h/t Spaceweather.com

NASA Uses Gravitational Wave Detector Prototype to Detect ‘Space Mosquito’ Splats

Artist impression of ESA LISA Pathfinder in interplanetary space (ESA)

Imagine speeding down the highway and plowing into an unfortunate swarm of mosquitoes. Now imagine that you had the ability to precisely measure the mass of each mosquito, the speed at which it was traveling and the direction it was going before it exploded over your windscreen.

Granted, the technology to accomplish that probably isn’t feasible in such an uncontrolled environment. Factors such as vibration from the car’s motor and tires on the road, plus wind and air turbulence will completely drown out any “splat” from a minuscule insect’s body, rendering any signal difficult to decipher from noise.

But move your hypothetical “car and mosquitoes” into space — as silly as that may sound — and things become a lot less noisy. And now NASA is measuring its own special kind of “mosquito splat” signal by using a rather unlikely space experiment.

The European LISA Pathfinder spacecraft is a proof of concept mission that’s currently in space, orbiting a region of gravitational stability between the Earth and the sun — called the L1 point located a million miles away. The spacecraft was launched there in late 2015 to carry out precision tests of instruments that will eventually be used in the space-based gravitational wave detector eLISA. Inside the payload is a miniaturized laser interferometer system that measures the distance between two test masses.

When launched in 2034, eLISA (which stands for Evolved Laser Interferometer Space Antenna) will see three spacecraft, orbiting the sun at the L1 point, firing ultra-precise lasers at one another as part of a space-based gravitational wave detector. Now we actually know gravitational waves exist — after the US-based Laser Interferometer Gravitational-wave Observatory (or LIGO) detected the space-time ripples created after the collisions of black holes — excitement is building that we might, one day, be able to measure other phenomena, such as the ultra-low frequency gravitational waves that were created during the Big Bang.

But the only way we can do this is to send stunningly precise interferometers into space, away from our vibration-filled atmosphere to stand a chance of detecting some of the faintest space-time rumbles in our cosmos that would otherwise be drowned out by a passing delivery truck or windy day. And LISA Pathfinder is currently out there, testing a tiny laser interferometer in a near-perfect gravitational free-fall, making the slightest of slight adjustments with its “ultra-precise micro-propulsion system.”

Although LISA Pathfinder is a test (albeit a history-making test of incredible engineering ingenuity), NASA thinks that it could actually be used as an observatory in its own right; not for hunting gravitational waves, but for detecting comet dust.

Like our mosquito-windscreen analogy, spacecraft get hit by tiny particles all the time, and LISA Pathfinder is no exception. These micrometeoroides come from eons of evaporating comets and colliding asteroids. Although measuring less than the size of a grain of sand, these tiny particles zip around interplanetary space at astonishing speeds — well over 22,000 miles per hour (that’s 22 times faster than a hyper-velocity rifle round) — and can damage spacecraft over time, slowly eroding unprotected hardware.

Therefore, it would be nice if we could create a map of regions in the solar system that contain lots of these particles so we can be better prepared to face the risk. Although models of solar system evolution help and we can estimate the distribution of these particles, they’ve only ever been measured near Earth, so it would be advantageous to find the “ground truth” and measure them directly from another, unexplored region of the solar system.

This is where LISA Pathfinder comes in.

As the spacecraft gets hit by these minuscule particles, although they are tiny, their high speed ensures they pack a measurable punch. As scientists want the test weights inside the spacecraft to be completely shielded from any external force — whether that’s radiation pressure from the sun or marauding micro-space rocks — the spacecraft has been engineered to be an ultra-precise container that carefully adjusts its orientation an exact amount to directly counter these external forces (hence the “ultra-precise micro-propulsion system”).

lisa-pathfinder
When LISA Pathfinder is struck by space dust, it compensates with its ultra-precise micro-thrusters (ESA/NASA)

This bit is pretty awesome: Whenever these tiny space particles hit the spacecraft, it compensates for the impact and that compensation is registered as a “blip” in the telemetry being beamed back to Earth. After careful analysis of the various data streams, researchers are learning a surprising amount of information about these micrometeoroides — such as their mass, speed, direction of travel and even their possible origin! — all for the ultimate goal of getting to know the tiny pieces of junk that whiz around space.

“Every time microscopic dust strikes LISA Pathfinder, its thrusters null out the small amount of momentum transferred to the spacecraft,” said Diego Janches, of NASA’s Goddard Space Flight Center in Greenbelt, Md. “We can turn that around and use the thruster firings to learn more about the impacting particles. One team’s noise becomes another team’s data.”

So, it turns out that you can precisely measure a mosquito impact on your car’s windshield — so long as that “mosquito” is a particle of space dust and your “car” is a spacecraft a million miles from Earth.

NASA put together a great video, watch it:

Aside: So it turned out that I inadvertently tested the “car-mosquito” hypothesis when driving home from Las Vegas — though some of these were a lot bigger than mosquitoes…

Mars’ Ancient Mega-Floods Are Still Etched Into the Red Planet

Around 3.5 billion years ago — when basic life was just gaining a foothold on Earth — the Tharsis region on Mars was swamped with vast floods that scar the landscape to this day.

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Rendered perspective view of Worcester Crater using Mars Express elevation data. The dramatic crater rim was carved by the flow of ancient floodwater (ESA)

Mars wears its geological history like a badge of honor — ancient craters remain unchanged for hundreds of millions of years and long-extinct volcanoes look as if they were venting only yesterday. This is the nature of Mars’ thin, cold atmosphere; erosional processes that rapidly delete Earth’s geological history are largely absent on the Red Planet, creating a smorgasbord of features that provide planetary scientists with an open book on Mars’ ancient past.

In this latest observation from the European Mars Express mission, a flood of biblical proportions has been captured in all its glory. But this flood didn’t happen recently, this flood engulfed a vast plain to the north of the famous Valles Marineris region billions of years ago.

It is believed that a series of volcanic eruptions and tectonic upheavals in the Tharsis region caused several massive groundwater releases from Echus Chasma, a collection of valleys some 100 kilometers (62 miles) long and up to 4 kilometers (2.5 miles) deep. These powerful bursts of water carved vast outflow channels into the adjacent Lunae Planum, contributing to the formation of the Kasei Valles outflow channels, releasing water into the vast Chryse Planitia plains which acted as a “sink.” Smaller “dendritic” channels can be seen throughout the plain, indicating that there were likely many episodic bursts of water flooding the region.

This context image shows a region of Mars where Kasei Vallis empties into the vast Chryse Planitia (NASA MGS MOLA Science Team)
This context image shows a region of Mars where Kasei Vallis empties into the vast Chryse Planitia (NASA MGS MOLA Science Team)

These floods happened between 3.4 to 3.6 billion years ago, less than a billion years after the most basic lifeforms started to appear on Earth (a period of time known as the Paleoarchean era).

In the middle of what was likely a powerful, vast and turbulent flows of water is Worcester Crater that was created before the Tharsis floods and, though its crater rim stands to this day and retains its shape, it was obviously affected by the flow of water, with a “tail” of sediment downstream.

ESA Mars Express observation of the mouth of Kasei Valles, as it transitions into Chryse Planitia. The large crater in the lower left is Worcester Crater. (ESA/DLR/FU Berlin)
ESA Mars Express observation of the mouth of Kasei Valles, as it transitions into Chryse Planitia. The large crater in the lower left is Worcester Crater (ESA/DLR/FU Berlin)

Also of note are smaller “fresh” craters that would have appeared long after the flooding took place, excavating the otherwise smooth outflow channels. These younger craters have tails that seem to be pointed in the opposite direction of the flow of water. These tails weren’t caused by the flow of water, but by the prevailing wind direction.

From orbital observations by our armada of Mars missions, it is well known that these channels contain clays and other minerals associated with the long-term presence of water. Although the Red Planet is now a very dry place, as these beautiful Mars Express images show, this certainly hasn’t always been the case.

Soyuz Floating On Clouds

The Soyuz TMA-03M spacecraft parachute contrasts with the cloud over Kazakhstan minutes before touchdown. Credit: Bill Ingalls/NASA
The Soyuz TMA-03M spacecraft parachute contrasts with the cloud over Kazakhstan minutes before touchdown. Credit: Bill Ingalls/NASA

In the early hours of Sunday morning (Pacific Time), a Russian cosmonaut, NASA astronaut and a European Space Agency astronaut returned to Earth after a 6-month stay on the International Space Station (ISS). Oleg Kononenko, Don Pettit and Andre Kuipers landed safely on the Kazakhstan steppes after the Soyuz TMA-03M spacecraft fired its soft landing rockets, blasting a cloud of dust into the air. But before touchdown and after the violence of reentry, NASA photographer Bill Ingalls was able to photograph this beautiful aerial view of the Soyuz and deployed parachute above the clouds. What a ride that must have been.

Read more about the successful Soyuz landing on Discovery News.

Special thanks to NASA astronaut Nicole Stott (@Astro_Nicole) for tweeting this photo!

Hubble Conquers Mystic Mountain

Where is that mystical land? (NASA/ESA/HST).
Where is this mystical land? (NASA/ESA/HST).

Sometimes, words are not enough to describe views of the universe when captured through the lens of the Hubble Space Telescope. This is one of those moments.

Kicking off its 20th anniversary (yes, that super-sized telescope has been in space that long — I would say that I remember it being launched, but I don’t, because I was nine, playing with my Star Wars toys), Hubble has published some astonishing images of deep inside the Carina Nebula, some 7,500 light-years from Earth. And, quite frankly, I’m floored.

BIG PIC: Have a look deep inside the Carina Nebula with some of my Discovery News coverage of the event.

The pillar of gas and dust looks like a gnarled tree branch, dotted with sparkling lights. The Hubble press release even describes the structure as a “Mystic Mountain,” and it’s not hard to see why. In this age of computer generated everything, this release of images show that the cosmos contains things that defy our tiny imaginations.

We are looking at a star-forming region, deep inside the nebula, where stars are being born inside the bulbous towers of gas and dust, but on the outside, young stars are battering the tower with intense stellar winds and powerful radiation. The pillar is being eroded away. However, this exterior pressure is seeding the birth of new stars inside the nebulous material.

The mindblowing clarity of this Hubble observation even brings out the fine detail in the jets of ionized gas as it is blasted from the point of the tallest finger of material. This is being generated by a young star, gorging itself on gas, forming a superheated accretion disk, blasting the energized gas out from the stellar nursery.

As Hubble’s 20th anniversary celebrations continue, I think we can expect a lot more where this came from. So brace yourself, this gem of a space telescope may be getting old, but it still has a shedload of cosmos to show us.

Now, lets stand back and get a better view of the incredible floating ‘Mystic Mountain’…

The Carina stellar nursary from afar (NASA/ESA/HST)
The Carina stellar nursary from afar (NASA/ESA/HST)

A Visor Filled With Awesomeness

The space station as reflected in John "Danny" Olivas' spacesuit visor on September 3, 2009 (NASA)
The space station as reflected in John "Danny" Olivas' spacesuit visor on September 3, 2009 (NASA)

When I came across this image in NASA’s Human Space Flight gallery, I stopped. I was looking for the “perfect” shuttle image during the STS-128 mission to the International Space Station earlier this month, but I got sucked into browsing through the hundreds of EVA photographs NASA has stockpiled in their archives.

This particular scene was taken by NASA astronaut John "Danny" Olivas when he was out on a spacewalk installing a new Ammonia Tank Assembly. The EVA was over six hours long and Olivas was able to do some digital photography in that time. This picture shows his spacesuit helmet visor, with a reflection of the camera at arms length below.

Also visible in the reflections in the visor are various components of the station and European Space Agency astronaut Christer Fuglesang, mission specialist, anchored to a Canadarm2 mobile foot restraint. —NASA

The reflection captures so much detail. The curvature of the Earth can be seen in the distance, with space station solar arrays jutting in front. Even the two docked Soyuz vehicles (TMA-14 and TMA-15) are in shot. To top it all off, ESA astronaut Fuglesang is dangling in the vacuum of space attached to a robotic arm.

Quite simply, awesome.

Geodesy and GOCE: Astrocast.TV with Bente Lilja Bye

In the first episode of A Green Space — A Green Earth at Astrocast.TV, my friend and astrophysicist Bente Lilja Bye gives a superb overview about the Gravity field and steady-state Ocean Circulation Explorer (GOCE) that was finally launched in March. It’s a captivating show, detailing the history and science behind the study of geodesy (the gravitational field, shape and rotation of the Earth).

You may not be familiar with geodesy, but it is critical to advancing our understanding of the planet we live on. For example, GOCE observations could aid prediction techniques for earthquakes, or refine GPS data; suddenly geodesy has a very real and immediate relevance to us on the ground.

Be sure to check out the video below, it’s a very slick production. Great job Bente!

Alien Worlds: Extrasolar Planets Imaged for First Time

Two of the three confirmed planets orbiting HR 8799 indicated as
Two of the three confirmed planets orbiting HR 8799 indicated as “b” and “c” on the image above. “b” is the ~7 Jupiter-mass planet orbiting at about 70 AU, “c” is the ~10 Jupiter-mass planet orbiting the star at about 40 AU. Due to the brightness of the central star, it has been blocked and appears blank in this image to increase visibility of the planets (Gemini Observatory)

The day has finally come. We now have direct, infrared and optical observations of planets orbiting other stars. Yesterday, reports from two independent sources surfaced, one from the Gemini and Keck II observatories and the second from the Hubble Space Telescope. Brace yourself for an awe-inspiring display of planets orbiting two stars…

The Gemini/Keck observations were carried out using adaptive optics technology to correct in real-time for atmospheric turbulence. The stunning images of a multiple planetary star system were then constructed from infrared emissions (the image, top, was constructed by Keck II as a follow-up to to the Gemini observations). The system in question is centred around a star called HR 8799, approximately 130 light years from Earth and in the constellation of Pegasus. The entire press release can be found at the Gemini observatory site, where they give the discovery a full run-down.

On the same day, the Hubble Space Telescope team also released images of one extrasolar planet, only this time in optical wavelengths. Although the exoplanet in Hubble’s images is less obvious than the infrared Gemini/Keck II images, incredible detail has been attained, showing a ring of dust around the star Fomalhaut (located in the constellation of Piscis Austrinus). Fomalhaut is 25 light years away and the star’s daughter planet (Fomalhaut b) is only a little under 3 Jupiter masses.

Estimated to be no more than three times Jupiter's mass, the planet, called Fomalhaut b, orbits the bright southern star Fomalhaut, located 25 light-years away in the constellation Piscis Austrinus (NASA/ESA)
Estimated to be no more than three times Jupiter’s mass, the planet, called Fomalhaut b, orbits the bright southern star Fomalhaut, located 25 light-years away in the constellation Piscis Austrinus (NASA/ESA)

For more news on these discoveries, check out the Gemini/Keck II press release and the Hubble announcement. I’ll leave the ground-breaking announcement to the guys who have spent many years working to achieve this monumental goal.

Wow.

Sources: Gemini, ESA

GOCE is Suffering Major Delays, But Should be Dominating Space by February

No, it isn't sci-fi. It's the Porche of orbital engineering (GOCE/ESA)
No, it isn't sci-fi. It's the Porche of orbital engineering (GOCE/ESA)

The European Space Agency’s Gravity field and state-steady Ocean Circulation Explorer (GOCE) should be in space by now. In fact it should have been launched back on September 10th, but it wasn’t to be. After the spacecraft (which has a striking resemblance to something a little more sci-fi… like a star destroyer) had been sealed into the payload bay of the Rockot launch vehicle at Plesetsk cosmodrome 800 km from Moscow, I assumed that was it, we wouldn’t be seeing GOCE ever again. But there was a glitch in the guidance and navigation subsystem of the Breeze KM third stage, thus postponing GOCE’s big day. GOCE was cracked open from its rocket powered cocoon to await a Rockot oil change.

Now it seems the delays are mounting up for this amazing experiment and a launch doesn’t seem possible until February at the earliest…
Continue reading “GOCE is Suffering Major Delays, But Should be Dominating Space by February”