Posted on by Matt Williams

When Galaxies Collide, Stars Suffer the Consequences

An artist's depiction of the tidal disruption event in F01004-2237. The release of gravitational energy as the debris of the star is accreted by the black hole leads to a flare in the optical light of the galaxy. Credit and copyright: Mark Garlick.

When galaxies collide, the result is nothing short of spectacular. While this type of event only takes place once every few billion years (and takes millions of years to complete), it is actually pretty common from a cosmological perspective. And interestingly enough, one of the most impressive consequences – stars being ripped apart by supermassive black holes (SMBHs) – is quite common as well.

This process is known in the scientific community as stellar cannibalism, or Tidal Disruption Events (TDEs). Until recently, astronomers believed that these sorts of events were very rare. But according to a pioneering study conducted by leading scientists from the University of Sheffield, it is actually 100 times more likely than astronomers previously suspected.

TDEs were first proposed in 1975 as an inevitable consequence of black holes being present at the center of galaxies. When a star passes close enough to be subject to the tidal forces of a SMBH it undergoes what is known as “spaghetification”, where material is slowly pulled away and forms string-like shapes around the black hole. The process causes dramatic flare ups that can be billions of times brighter than all the stars in the galaxy combined.

Since the gravitational force of black holes is so strong that even light cannot escape their surfaces (thus making them invisible to conventional instruments), TDEs can be used to locate SMBHs at the center of galaxies and study how they accrete matter. Previously, astronomers have relied on large-area surveys to determine the rate at which TDEs happen, and concluded that they occur at a rate of once every 10,000 to 100,000 years per galaxy.

However, using the William Herschel Telescope at the Roque de los Muchachos Observatory on the island of La Palma, the team of scientists – who hail from Sheffield’s Department of Physics and Astronomy – conducted a survey of 15 ultra-luminous infrared galaxies that were undergoing galactic collisions. When comparing information on one galaxy that had been observed twice over a ten year period, they noticed that a TDE was taking place.

Their findings were detailed in a study titled “A tidal disruption event in the nearby ultra-luminous infrared galaxy F01004-2237“, which appeared recently in the journal Nature: Astronomy. As Dr James Mullaney, a Lecturer in Astronomy at Sheffield and a co-author of the study, said in a University press release:

“Each of these 15 galaxies is undergoing a ‘cosmic collision’ with a neighboring galaxy. Our surprising findings show that the rate of TDEs dramatically increases when galaxies collide. This is likely due to the fact that the collisions lead to large numbers of stars being formed close to the central supermassive black holes in the two galaxies as they merge together.”

The William Herschel Telescope, part of the Isaac Newton group of telescopes, located in the Canary Islands. Credit: ing.iac.es

The Sheffield team first observed these 15 colliding galaxies in 2005 during a previous survey. However, when they observed them again in 2015, they noticed that one of the galaxies in the sample – F01004-2237 – appeared to have undergone some changes. The team them consulted data from the Hubble Space Telescope and the Catalina Sky Survey – which monitors the brightness of astronomical objects (particularly NEOs) over time.

What they found was that the brightness of F01004-2237 – which is about 1.7 billion light years from Earth – had changed dramatically. Ordinarily, such flare ups would be attributed to a supernova or matter being accreted onto an SMBH at the center (aka. an active galactic nucleus). However, the nature of this flare up (which showed unusually strong and broad helium emission lines in its post-flare spectrum) was more consistent with a TDE.

The appearance of such an event had been detected during a repeat spectroscopic observations of a sample of 15 galaxies over a period of just 10 years suggested that the rate at which TDEs happen was far higher than previously thought – and by a factor of 100 no less. As Clive Tadhunter, a Professor of Astrophysics at the University of Sheffield and lead author of the study, said:

“Based on our results for F01004-2237, we expect that TDE events will become common in our own Milky Way galaxy when it eventually merges with the neighboring Andromeda galaxy in about 5 billion years. Looking towards the center of the Milky Way at the time of the merger we’d see a flare approximately every 10 to 100 years. The flares would be visible to the naked eye and appear much brighter than any other star or planet in the night sky.”

Credit: ESA/Hubble, ESO, M. Kornmesser
Artist’s impression depicts a rapidly spinning supermassive black hole surrounded by an accretion disc. Credit: ESA/Hubble, ESO, M. Kornmesse

In the meantime, we can expect that TDEs are likely to be noticed in other galaxies within our own lifetimes. The last time such an event was witnessed directly was back in 2015, when the All-Sky Automated Survey for Supernovae (aka. ASAS-SN, or Assassin) detected a superlimunous event four billion light years away – which follow-up investigations revealed was a star being swallowed by a spinning SMBH.

Naturally, news of this was met with a fair degree of excitement from the astronomical community, since it was such a rare event. But if the results of this study are any indication, astronomers should be noticing plenty more stars being slowly ripped apart in the not-too-distant future.

With improvements in instrumentation, and next-generation instruments like the James Webb Telescope being deployed in the coming years, these rare and extremely picturesque events may prove to be a more common experience.

Further Reading: Nature: Astronomy, University of Sheffield

Posted on by Fraser Cain

Astronomy Cast Ep. 442: Destroy and Rebuild Pt. 6: Magnetic Pole Reversal

Magnetic Pole Reversal

If we look back into the geologic record of the Earth, it appears that our planet’s magnetic field flips polarity every few hundred thousand years or so. Why does this happen? When’s it supposed to happen next? Is it dangerous?

Visit the Astronomy Cast Page to subscribe to the audio podcast!

We usually record Astronomy Cast as a live Google+ Hangout on Air every Friday at 1:30 pm Pacific / 4:30 pm Eastern. You can watch here on Universe Today or from the Astronomy Cast Google+ page.

Posted on by Matt Williams

Some Active Process is Cracking Open These Faults on Mars. But What is it?

A 2008 image showing a portion of the North Polar layered deposits with lines of very small pits. Credit: NASA/JPL/University of Arizona

Mars has many characteristics that put one in mind of Earth. Consider its polar ice caps, which are quite similar to the ones in the Arctic and Antarctic circle. But upon closer examination, Mars’ icy polar regions have numerous features that hint at some unusual processes. Consider the northern polar ice cap, which consists predominantly of frozen water ice, but also a seasonal veneer of frozen carbon dioxide (“dry ice”).

Here, ice is arranged in multicolored layers that are due to seasonal change and weather patterns. And as images taken by the Mars Global Surveyor and the Mars Reconnaissance Orbiter (MRO) have shown, the region is also covered in lines of small pits that measure about 1 meter (3.28 feet) in diameter. While these features have been known to scientists for some time, the process behind them remains something of a mystery.

Layered features around found both in the northern and southern polar regions of Mars, and are the result of seasonal melting and the deposition of ice and dust (from Martian dust storms). Both polar caps also show grooves which appear to be influenced by the amount of dust deposited. The more dust there is, the darker the surface of the grooved feature, which affects the level of seasonal melting that takes place.

HiRISE image showing the layered appearance of Mars’ northern polar region. Credit: NASA/JPL/University of Arizona

These layered deposits measure around 3-kilometer thick and about 1000 kilometers across. And in many locations, erosion and melting has created scarps and troughs that expose the layering (shown above). However, as NASA’s Mars Global Surveyor revealed through a series of high-resolution images, the northern polar cap also has plenty of pits, cracks, small bumps and knobs that give it a strange, textured look.

These featured have also been imaged in detail by the High Resolution Imaging Science Experiment (HiRISE) instrument aboard the MRO. In 2008, it snapped the image shown at top, which illustrates how the layered features in the northern polar region also have lines of small pits cutting across them. Such small pits should be quickly filled in by seasonal ice and dust, so their existence has been something of a mystery.

What this process could be has been the preoccupation of researchers like Doctor Chris Okubo and Professor Alfred McEwen. In addition to being a planetary geologist from the Lunar and Planetary Laboratory (LPL) at Arizona State University, Prof. McEwen is the Principal Investigator of the High Resolution Imaging Science Experiment (HiRISE).

Dr. Chris Okubo, meanwhile, is a planetary engineer with the LPL who has spent some time examining Mars’ northern polar region, seeking to determine what geological process could account for them. Over time, he also noted that the pits appeared to be enlarging. As he explained to Universe Today via email:

“I monitored some of these pits during northern summer of Mars year 31 (2011-2012). The pits appeared to enlarge over time, starting from depressions roughly centered on the pits observed in in  2008. My interpretation is that these pits are depressions within the residual cap that formed through collapse above a fault or fracture. The pits are buried by seasonal ice in the winter, which then sublimates in the spring/summer leading to an apparent widening and exposure of the pits until they are reburied by seasonal ice in the subsequent winter.”

HiRISE being prepared before it is shipped for attachment to the spacecraft. Credit: NASA/JPL

Since the MRO reached Mars in 2006, the LPL has been responsible for processing and interpreting images sent back by its HiRISE instrument. As for these pits, the theory that they are the result of faults pulling apart the icy layers is the most currently-favored one. Naturally, it will have to be tested as more data comes, in showing how seasonal changes play out in Mars’ northern polar region.

“I  plan to re-monitor the same pits I looked at in MY31 during this upcoming northern summer to see if this pattern has changed substantially,” said Okubo. “Re-imaging these after several Mars years may also reveal changes to the size/distribution of the pits within the residual cap – if such changes are observed, then that would suggest that the underlying fractures are active.”

One thing is clear though; the layered appearance of Mars polar ice caps and its strange surface features are just another indication of the dynamic processes taking place on Mars. In addition to seasonal change, these interesting features are thought to be related to changes in Mars’ obliquity and axial tilt. Just one more way in which Mars and Earth are similar!

Further Reading: HIRISE

Posted on by Matt Williams

Volcanic Hydrogen Gives Planets a Boost for Life

Image of the Sarychev volcano (in Russia's Kuril Islands) caught during an early stage of eruption on June 12, 2009. Taken by astronauts aboard the International Space Station. Credit: NASA

Whenever the existence of an extra-solar planet is confirmed, there is reason to celebrate. With every new discovery, humanity increases the odds of finding life somewhere else in the Universe. And even if that life is not advanced enough (or particularly inclined) to build a radio antenna so we might be able to hear from them, even the possibility of life beyond our Solar System is exciting.

Unfortunately, determining whether or not a planet is habitable is difficult and subject to a lot of guesswork. While astronomers use various techniques to put constraints on the size, mass, and composition of extra-solar planets, there is no surefire way to know if these worlds are habitable. But according to a new study from a team of astronomers from Cornell University, looking for signs of volcanic activity could help.

Their study – titled “A Volcanic Hydrogen Habitable Zone” – was recently published in The Astrophysical Journal Letters. According to their findings, the key to zeroing in on life on other planets is to look for the telltale signs of volcanic eruptions – namely, hydrogen gas (H²). The reason being is that this, and the traditional greenhouse gases, could extend the habitable zones of stars considerably.

The habitable zones of three stars detected by the Kepler mission. Credit: NASA/Ames/JPL-Caltech

As Ramses Ramirez, a research associate at Cornell’s Carl Sagan Institute and the lead author of the study, said in a University press release:

“On frozen planets, any potential life would be buried under layers of ice, which would make it really hard to spot with telescopes. But if the surface is warm enough – thanks to volcanic hydrogen and atmospheric warming – you could have life on the surface, generating a slew of detectable signatures.”

Planetary scientists theorize that billions of years ago, Earth’s early atmosphere had an abundant supply of hydrogen gas (H²) due to volcanic outgassing. Interaction between hydrogen and nitrogen molecules in this atmosphere are believed to have kept the Earth warm long enough for life to develop. However, over the next few million years, this hydrogen gas escaped into space.

This is believed to be the fate of all terrestrial planets, which can only hold onto their planet-warming hydrogen for so long. But according to the new study, volcanic activity could change this. As long as they are active, and their activity is intense enough, even planets that are far from their stars could experience a greenhouse effect that would be sufficient to keep their surfaces warm.

Distant exoplanets that are not in the traditional “Goldilocks Zone” might be habitable, assuming they have enough volcanic activity. Credit: ESO.

Consider the Solar System. When accounting for the traditional greenhouse effect caused by nitrogen gas (N²), carbon dioxide and water, the outer edge of our Sun’s habitable zone extends to a distance of about 1.7 AU – just outside the orbit of Mars. Beyond this, the condensation and scattering of CO² molecules make a greenhouse effect negligible.

However, if one factors in the outgassing of sufficient levels of H², that habitable zone can extend that outer edge to about 2.4 AUs. At this distance, planets that are the same distance from the Sun as the Asteroid Belt would theoretically be able to sustain life – provided enough volcanic activity was present. This is certainly exciting news, especially in light of the recent announcement of seven exoplanets orbiting the nearby TRAPPIST-1 star.

Of these planets, three are believed to orbit within the star’s habitable zone. But as Lisa Kaltenegger – also a member of the Carl Sagan Institute and the co-author on the paper – indicated, their research could add another planet to this
“potentially-habitable” lineup:

“Finding multiple planets in the habitable zone of their host star is a great discovery because it means that there can be even more potentially habitable planets per star than we thought. Finding more rocky planets in the habitable zone – per star – increases our odds of finding life… Although uncertainties with the orbit of the outermost Trappist-1 planet ‘h’ means that we’ll have to wait and see on that one.”

Artist’s concept of the TRAPPIST-1 star system, an ultra-cool dwarf that has seven Earth-size planets orbiting it. Credits: NASA/JPL-Caltech

Another upside of this study is that the presence of volcanically-produced hydrogen gas would be easy to detect by both ground-based and space-based telescopes (which routinely conduct spectroscopic surveys on distant exoplanets). So not only would volcanic activity increase the likelihood of there being life on a planet, it would also be relatively easy to confirm.

“We just increased the width of the habitable zone by about half, adding a lot more planets to our ‘search here’ target list,” said Ramirez. “Adding hydrogen to the air of an exoplanet is a good thing if you’re an astronomer trying to observe potential life from a telescope or a space mission. It increases your signal, making it easier to spot the makeup of the atmosphere as compared to planets without hydrogen.”

Already, missions like Spitzer and the Hubble Space Telescope are used to study exoplanets for signs of hydrogen and helium – mainly to determine if they are gas giants or rocky planets. But by looking for hydrogen gas along with other biosignatures (i.e. methane and ozone), next-generation instruments like the James Webb Space Telescope or the European Extremely Large Telescope, could narrow the search for life.

It is, of course, far too soon to say if this study will help in our search for extra-solar life. But in the coming years, we may find ourselves one step closer to resolving that troublesome Fermi Paradox!

Further Reading: Astrophysical Journal Letters

Posted on by Nancy Atkinson

What the Oldest Fossil on Earth Means for Finding Life on Mars

Microscopic iron-carbonate (white) rosette with concentric layers of quartz inclusions (grey) and a core of a single quartz crystal with tiny (nanoscopic) inclusions of red hematite from the Nuvvuagittuq Supracrustal Belt in Québec, Canada. These may have formed through the oxidation of organic matter derived from microbes living around vents. Credit: Matthew Dodd/UCL.

Scientists have found evidence that life existed on Earth much earlier than previously thought and they say this discovery has implications for life springing up on other planets, particularly Mars.

Fossils of microscopic bacteria were discovered in Quebec, Canada in the Nuvvuagittuq Supracrustal Belt, a formation which contains some of the oldest sedimentary rocks in the world. Scientists estimate the fossils are at least 3.7 billion years old, and could be as old as 4.28 billion years. This is hundreds of millions of years older than previously found specimens.

“The most exciting thing about this discovery is that we know life managed to get a grip and start on Earth at such an early time in Earth’s evolution, which gives us exciting questions as to whether we are alone in the solar system or in the universe,” said PhD student Matthew Dodd from University College London (UCL), who is the first author on a new paper about the finding in the journal Nature. “If life happened so quickly on Earth then could we expect it to be a simple process and start on other planets, or was Earth really just a special case?”

Hematite tubes from the hydrothermal vent deposits that represent the oldest microfossils and evidence for life on Earth. The remains are at least 3.7 billion years old. Credit: Matthew Dodd/UCL

The tiny fossils are the remains of microorganisms that are smaller than the width of a human hair. The Nuvvuagittuq rocks are thought to have formed in an iron-rich deep-sea hydrothermal vent system that provided a habitat for Earth’s first life forms. These rocks are mostly composed of silica and hematite.

“Our discovery supports the idea that life emerged from hot, seafloor vents shortly after planet Earth formed,” Dodd said in a press release. “This speedy appearance of life on Earth fits with other evidence of recently discovered 3,700 million year old sedimentary mounds that were shaped by microorganisms.”

Prior to this discovery, the oldest microfossils reported were found in Western Australia and were dated at 3.4 billion years old, leading scientists to speculate that life probably started around 3.7 billion years ago. But the new finding suggests that life existed as early as 4.5 billion years ago, just 100 million years after Earth formed.

“The microfossils we discovered are about 300 million years older than the previously thought oldest microfossils,” said Dr. Dominic Papineau, a professor of geochemistry and astrobiology at UCL, “so they are within a few hundred million years from within the accretion of the solar system and the planet Earth and the Sun and the Moon and so on.”

The Blueberries of Mars are actually concretions of iron rich minerals from water – ground or standing pools – created over thousands of years during periodic epochs of wet climates on Mars. (Photo Credits: NASA/JPL/Cornell)

Papineau said the structures in the rocks that contained the fossils were spheroids, and since they are made of hematite, they are reminiscent of the discovery in 2004 by the Mars Exploration Rover Opportunity of beds of rounded hematite concretions, that MER scientists called “blueberries.” These rounded concretions formed on Earth when significant volumes of groundwater flowed through permeable rock, and chemical reactions triggered minerals to precipitate and start forming a layered, spherical ball.

The concretions may bear on the search for evidence of past life on Mars because bacteria on Earth can make concretions form more quickly, according to previous research.

“The origin of this structure is not fully understood even on Earth where we find them,” Papineau said. “We don’t know really how organic matter can potentially be involved in making these structures.”

Both the MER rovers, Opportunity and Spirit, as well as the Curiosity rover have all found evidence of past water on Mars. In addition, Curiosity has identified traces of elements like carbon, hydrogen, nitrogen, oxygen, and more — the basic building blocks of life. It also found sulfur compounds in different chemical forms, a possible energy source for microbes. If Mars really was warmer and wetter in the past, as the evidence seems to point, Mars would have been the perfect spot for living organisms.

While the finding of ancient fossils on Earth doesn’t necessarily mean there is past or present life on Mars, in conjunction with the Curiosity rover finding of the raw ingredients for life, it is enticing to know that the environment on early Mars was likely very similar to early Earth, where life did spring up.

You can see details and hear the researchers talk about their findings in the video below:

Source: EurekAlert

Posted on by Evan Gough

Rise of the Super Telescopes: The European Extremely Large Telescope

This artist’s rendering of the E-ELT is based on the detailed construction design for the telescope. Image: ESO/L. Calçada/ACe Consortium

We humans have an insatiable hunger to understand the Universe. As Carl Sagan said, “Understanding is Ecstasy.” But to understand the Universe, we need better and better ways to observe it. And that means one thing: big, huge, enormous telescopes.

In this series we’ll look at 6 of the world’s Super Telescopes:

The European Extremely Large Telescope

The European Extremely Large Telescope (E-ELT) is an enormous ‘scope being built by the European Southern Observatory. It’s under construction right now in the high-altitude Atacama Desert of northern Chile. The ESO, with its partners, has built some of the largest and most technically advanced telescopes in the world, like the Atacama Large Millimeter Array (ALMA) and the Very Large Telescope (VLT.) But with a 39 meter primary mirror, the E-ELT will dwarf the other telescopes in the ESO’s fleet.

As Dr Michele Cirasuolo, Programme Scientist for the ELT told Universe Today, “The Extremely Large Telescope (ELT) is the flagship project of the European Southern Observatory (ESO), and when completed in 2024 will be the largest optical/infrared telescope in the world. It represents the next step forward and it will complement the research done with the GMT (Giant Magellan Telescope) and other large telescopes being built.”

This artist’s rendering of the E-ELT shows the 39 meter segmented mirror at the heart of the scope. ESO/L. Calçada/ACe Consortium

The E-ELT is the successor to the Overwhelmingly Large Telescope (OWL), which was the ESO backed away from due to its €1.5 billion price tag. Instead, the ESO focussed on the E-ELT. The site for the E-ELT was selected in 2010, and over the next couple years the design was finalized.

Like other telescopes—including the Keck Telescope—the E-ELT’s primary mirror will be made up of individually manufactured hexagonal segments; 798 of them. The primary mirror will be fitted with edge sensors to ensure that each segment of the mirror is corrected in relation to its neighbours as the scope is aimed or moved, or as it is disturbed by temperature changes, wind, or vibrations.

The E-ELT is actually a 5 mirror system. Along with the enormous primary mirror, and the secondary mirror, there are three other mirrors. An unusual aspect of the E-ELT’s design is its tertiary mirror. This tertiary mirror will give the E-ELT better image quality over a larger field of view than a primary and secondary mirror can.

The ‘scope also has two other mirrors which provide adaptive optics and image stabilization, as well as allowing more large science instruments to be mounted to the ‘scope simultaneously.

This diagram shows the novel 5-mirror optical system of ESO’s Extremely Large Telescope (ELT). Before reaching the science instruments the light is first reflected from the telescope’s giant concave 39-metre segmented primary mirror (M1), it then bounces off two further 4-metre-class mirrors, one convex (M2) and one concave (M3). The final two mirrors (M4 and M5) form a built-in adaptive optics system to allow extremely sharp images to be formed at the final focal plane. Image By ESO – https://www.eso.org/public/images/eso1704a/, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=55268266

The Science: What Will the E-ELT Study?

The E-ELT is designed for an ambitious science agenda. One of the most exciting aspects of the E-ELT is its potential to capture images of extra-solar planets. The 39 meter mirror will not only collect more light from distant, faint objects, but will provide an increase in angular resolution. This means that the telescope will be capable of distinguishing objects that are close together.

As Dr. Cirasuolo explains, “This will allow the ELT to image exoplanets nearer to the star they are orbiting. We aim to probe planets in the so called habitable zone (where liquid water could exist on their surfaces) and take spectra to analyse the composition of their atmospheres.”

The E-ELT has other goals as well. It aims to probe the formation and evolution of planetary systems, and to detect water and organic molecules in protoplanetary disks around stars as they form. It will look at some of the most distant objects possible—the first stars, galaxies, and black holes—to try to understand the relationships between them.

The telescope is also designed to study the first galaxies, and to chart their evolution over time. As if this list of science goals isn’t impressive enough, the E-ELT holds out the hope of directly measuring the acceleration in the expansion of the Universe.

This video explains the design of the E-ELT and some of its science goals.

These are all fascinating goals, but for many of us the most compelling question we face is “Are We Alone?” Dr. Cirasuolo feels the same. As he told Universe Today, “The ultimate goal is finding signs of life. Certainly the next generation of telescopes will provide a huge leap forward in our understanding of extra solar planets and for the search for life in the Universe.”

The E-ELT won’t be working alone. Other Super Telescopes, like the Giant Magellan Telescope, the Thirty Meter Telescope, and even the Large Synoptic Survey Telescope, will all be working in conjunction to expand the frontier of knowledge.

It may be a very long time, if ever, before we find life somewhere else in the Universe. But by expanding our knowledge of exo-planets, the E-ELT is going to be a huge part of the ongoing effort. A few years ago, we weren’t even certain that we would find many planets around other stars. Now the discovery of exoplanets is almost commonplace. If the E-ELT lives up to its promise, then capturing actual images of exoplanets may become commonplace as well.

Posted on by Evan Gough

7 Questions For 7 New Planets

Artist's concept of the TRAPPIST-1 star system, an ultra-cool dwarf that has seven Earth-size planets orbiting it. We're going to keep finding more and more solar systemsl like this, but we need observatories like WFIRST, with starshades, to understand the planets better. Credits: NASA/JPL-Caltech
Artist's concept of the TRAPPIST-1 star system, an ultra-cool dwarf that has seven Earth-size planets orbiting it. We're going to keep finding more and more solar systemsl like this, but we need observatories like WFIRST, with starshades, to understand the planets better. Credits: NASA/JPL-Caltech

NASA’s announcement last week of 7 new exoplanets is still causing great excitement. Any time you discover 7 “Earth-like” planets around a distant star, with 3 of them “potentially” in the habitable zone, it’s a big deal. But now that we’re over some of our initial excitement, let’s look at some of the questions that need to be answered before we can all get excited again.

What About That Star?

The star that the planets orbit, called Trappist-1, is a Red Dwarf star, much dimmer and cooler than our Sun. The three potentially habitable planets—TRAPPIST-1e, f, and g— get about the same amount of energy as Earth and Mars do from the Sun, because they’re so close to it. Red Dwarfs are very long-lasting stars, and their lifetimes are measured in the trillions of years, rather than billions of years, like our Sun is.

But Red Dwarfs themselves can have some unusual properties that are problematic when it comes to supporting life on nearby planets.

This illustration shows TRAPPIST-1 in relation to our Sun. Image: By ESO – http://www.eso.org/public/images/eso1615e/, CC BY 4.0, https://commons.wikimedia.org/w/index.php?curid=48532941

Red Dwarfs can be covered in starspots, or what we call sunspots when they appear on our Sun. On our Sun, they don’t have much affect on the amount of energy received by the Earth. But on a Red Dwarf, they can reduce the energy output by up to 40%. And this can go on for months at a time.

Other Red Dwarfs can emit powerful flares of energy, causing the star to double in brightness in mere minutes. Some Red Dwarfs constantly emit these flares, along with powerful magnetic fields.

Part of the excitement surrounding the Trappist planets is that they show multiple rocky planets in orbit around a Red Dwarf. And Red Dwarfs are the most common type of star in the Milky Way. So, the potential for life-supporting, rocky planets just grew in a huge way.

But we don’t know yet how the starspots and flaring of Red Dwarfs will affect the potential habitability of planets orbiting them. It could very well render them uninhabitable.

Will Tidal Locking Affect the Planets’ Habitability?

The planets orbiting Trappist-1 are very likely tidally locked to their star. This means that they don’t rotate, like Earth and the rest of the planets in our Solar System. This has huge implications for the potential habitability of these planets. With one side of the planet getting all the energy from the star, and the other side in perpetual darkness, these planets would be nothing like Earth.

Tidal locking is not rare. For example, Pluto and its moon Charon (above) are tidally locked to each other, as are the Earth and the Moon. But can life appear and survive on a planet tidally locked to its star? Credit: NASA/JHUAPL/SwRI

One side would be constantly roasted by the star, while the other would be frigid. It’s possible that some of these planets could have atmospheres. Depending on the type of atmosphere, the extreme temperature effects of tidal locking could be mitigated. But we just don’t know if or what type of atmosphere any of the planets have. Yet.

So, Do They Have Atmospheres?

We just don’t know yet. But we do have some constraints on what any atmospheres might be.

Preliminary data from the Hubble Space Telescope suggests that TRAPPIST 1b and 1c don’t have extended gas envelopes. All that really tells us is that they aren’t gaseous planets. In any case, those two planets are outside of the habitable zone. What we really need to know is if TRAPPIST 1e, 1f, and 1g have atmospheres. We also need to know if they have greenhouse gases in their atmospheres. Greenhouse gases could help make tidally locked planets hospitable to life.

On a tidally locked planet, the termination line between the sunlit side and the dark side is considered the most likely place for life to develop. The presence of greenhouse gases could expand the habitable band of the termination line and make more of the dark side warmer.

We won’t know much about any greenhouse gases in the atmospheres of these planets until the James Webb Space Telescope (JWST) and the European Extremely Large Telescope (EELT) are operating. Those two ‘scopes will be able to analyze the atmospheres for greenhouse gases. They might also be able to detect biosignatures like ozone and methane in the atmospheres.

We’ll have to wait a while for that though. The JWST doesn’t launch until October 2018, and the EELT won’t see first light until 2024.

Do They Have Liquid Water?

We don’t know for sure if life requires liquid water. We only know that’s true on Earth. Until we find life somewhere else, we have to be guided by what we know of life on Earth. So we always start with liquid water.

A study published in 2016 looked at planets orbiting ultra-cool dwarfs like TRAPPIST-1. They determined that TRAPPIST 1b and 1c could have lost as much as 15 Earth oceans of water during the early hot phase of their solar system. TRAPPIST 1d might have lost as much as 1 Earth ocean of water. If they had any water initially, that is. But the study also shows that they may have retained some of that water. It’s not clear if the three habitable planets in the TRAPPIST system suffered the same loss of initial water. But if they did, they could have retained a similar amount of water.

Artist’s impression of an “eyeball” planet, a water world where the sun-facing side is able to maintain a liquid-water ocean. Credit and Copyright: eburacum45/ DeviantArt

There are still a lot of questions here. The word “habitable” only means that they are receiving enough energy from their star to keep water in liquid form. Since the planets are tidally locked, any water they did retain could be frozen on the planets’ dark side. To find out for sure, we’ll have to point other instruments at them.

Are Their Orbits Stable?

Planets require stable orbits over a biologically significant period of time in order for life to develop. Conditions that change too rapidly make it impossible for life to survive and adapt. A planet needs a stable amount of solar radiation, and a stable temperature, to support life. If the solar radiation, and the planet’s temperature, fluctuates too rapidly or too much due to orbital instability, then life would not be able to adapt to those changes.

Right now, there’s no indication that the orbits of the TRAPPIST 1 planets are unstable. But we are still in the preliminary stage of investigation. We need a longer sampling of their orbits to know for sure.

Pelted by Interlopers?

Our Solar System is a relatively placid place when it comes to meteors and asteroids. But it wasn’t always that way. Evidence from lunar rock samples show that it may have suffered through a period called the “Late Heavy Bombardment.” During this time, the inner Solar System was like a shooting gallery, with Earth, Venus, Mercury, Mars, and our Moon being struck continuously by asteroids.

The cause of this period of Bombardment, so the theory goes, was the migration of the giant planets through the solar system. Their gravity would have dislodged asteroids from the asteroid belt and the Kuiper Belt, and sent them into the path of the inner, terrestrial planets.

We know that Earth has been hit by meteorites multiple times, and that at least one of those times, a mass extinction was the result.

Computer generated simulation of an asteroid strike on the Earth. Credit: Don Davis/AFP/Getty Images

The TRAPPIST 1 system has no giant planets. But we don’t know if it has an asteroid belt, a Kuiper Belt, or any other organized, stable body of asteroids. It may be populated by asteroids and comets that are unstable. Perhaps the planets in the habitable zone are subjected to regular asteroid strikes which wipes out any life that gets started there. Admittedly, this is purely speculative, but so are a lot of other things about the TRAPPIST 1 system.

How Will We Find Out More?

We need more powerful telescopes to probe exoplanets like those in the TRAPPIST 1 system. It’s the only way to learn more about them. Sending some kind of probe to a solar system 40 light years away is something that might not happen for generations, if ever.

Luckily, more powerful telescopes are on the way. The James Webb Space Telescope should be in operation by April of 2019, and one of its objectives is to study exoplanets. It will tell us a lot more about the atmospheres of distant exoplanets, and whether or not they can support life.

Other telescopes, like the Giant Magellan Telescope (GMT) and the European Extremely Large Telescope (E-ELT), have the potential to capture images of large exoplanets, and possibly even Earth-sized exoplanets like the ones in the TRAPPIST system. These telescopes will see their first light within ten years.

This artist’s impression shows the European Extremely Large Telescope (E-ELT) in its enclosure. The E-ELT will be a 39-metre aperture optical and infrared telescope. ESO/L. Calçada

What these questions show is that we can’t get ahead of ourselves. Yes, it’s exciting that the TRAPPIST planets have been discovered. It’s exciting that there are multiple terrestrial worlds there, and that 3 of them appear to be in the habitable zone.

It’s exciting that a Red Dwarf star—the most common type of star in our neighborhood—has been found with multiple rocky planets in the habitable zone. Maybe we’ll find a bunch more of them, and the prospect of finding life somewhere else will grow.

But it’s also possible that Earth, with all of its life supporting and sustaining characteristics, is an extremely unlikely occurrence. Special, rare, and unrepeatable.

Posted on by Matt Williams

How Far is Mercury from the Sun?

Transiting
NASA's Hinode X-ray telescope captured Mercury in transit against the Sun's corona in Nov. 2006. Similar views are possible in H-alpha light. Credit: NASA

Mercury is famously known for being a scorching hot world. On the side that is facing towards the Sun, conditions can get pretty molten, reaching temperatures of up to 700 K (427 °C; 800°F) in the equatorial region. The surface is also airless, in part because any atmosphere it could generate would be blown away by solar wind. Hardly surprising, considering it is the closest planet to our Sun.

But just how close is it? On average, it’s slightly more than one-third the distance between Earth and the Sun. However, its orbital eccentricity is also the greatest of any planet in the Solar System. In addition, its orbit is subject to perturbations, ones which were not fully understood until the 20th century. Because of this, Mercury goes through some serious changes during its orbital period.

Perihelion and Aphelion:

Mercury orbits the Sun at an average distance (semi-major axis) of 0.387 AU (57,909,050 km; 35,983,015 mi). However, due to its eccentricity of 0.205 – the highest in the Solar System, with the exception of Pluto (0.248) – its distance from the Sun ranges considerably. When it is at its closest (perihelion), it is 46,001,200 km (28,583,820 mi) from the Sun; and when it is farthest away (aphelion), it is 57,909,050 km (35,983,015 mi) from the Sun.

A timelapse of Mercury transiting across the face of the Sun. Credit: NASA

Orbital Resonance:

At one time, scientists believed that Mercury was tidally-locked, meaning that it kept one side facing towards the Sun at all times. However, it has since been discovered that the planet actually has a slow rotational period of 58.646 days. Compared to its orbital period of 88 days, this means that Mercury has a spin-orbit resonance of 3:2. This means that the planet makes three completes rotations on its axis for every two orbits around the Sun.

Another consequences of its spin-orbit resonance is that there is a significance difference between the time it takes the planet to rotate once on its axis (a sidereal day) and the time it takes for the Sun to reappear in the same place in the sky (a solar day). On Mercury, it takes a 176 days for the Sun to rise, set, and return to the same place in the sky. This means, effectively, that a single day on Mercury lasts as long as two years!

It’s slow rotation also means that temperature variations are extreme. On the Sun-facing side, temperatures can reach as high as 700 K (427 °C; 800°F) in the equatorial region and 380 K (107 °C; 224 °F) near the northern polar region. On the side facing away from the Sun, temperatures reach a low of 100 K (-173 °C; -280 °F) in the equatorial region and 80 K (-193 °C; -316 °F) near the northern polar region.

Diagram of Mercury’s eccentric orbit. Credit: solarviews.com

Perihelion Precession:

In addition to its eccentricity, Mercury’s perihelion is also subject to precession. What this means is, during the course of a century, Mercury’s orbit around the Sun shifts by 42.98 arcseconds (0.0119 degrees). This means that after twelve million orbits, Mercury will have performed a full excess turn around the Sun and returned to where it started.

This is much larger than the perihelion precession of other Solar planets – which range from 8.62 arcseconds (0.0024°) per century for Venus, 3.84 (0.001°) for Earth, and 1.35 (0.00037°) for Mars. Until the early 20th century, this behavior remained a mystery to astronomers, as Newtonian mechanics could not account for it. However, Einstein’s General Theory of Relativity provided an explanation, while the precession provided a test for his theory.

You might say Mercury and the Sun are pretty cozy. They dance pretty close, and the dance is powerful and full of some pretty wide swings!

We have written many interesting articles about the distance of the planets from the Sun here at Universe Today. Here’s How Far Are the Planets from the Sun?, How Far is Venus from the Sun?, How Far is Mars from the Sun?, How Far is the Earth from the Sun?, How Far is the Moon from the Sun?, How Far is Jupiter from the Sun?, How Far is Saturn from the Sun?, How Far is Uranus  from the Sun?, How Far is Neptune from the Sun? and How Far is Pluto from the Sun?

If you’d like more info on Mercury, check out NASA’s Solar System Exploration Guide, and here’s a link to NASA’s MESSENGER Misson Page.

We’ve also recorded an entire episode of Astronomy Cast all about Mercury. Listen here, Episode 49: Mercury.

Sources:

Posted on by Ken Kremer

So it Begins, Red Dragon Delayed 2 Years to 2020

Artists concept for sending SpaceX Red Dragon spacecraft to land propulsively on Mars as early as 2020. Credit: SpaceX
Artists concept for sending SpaceX Red Dragon spacecraft to land propulsively on Mars as early as 2020. Credit: SpaceX
Artists concept for sending SpaceX Red Dragon spacecraft to land propulsively on Mars as early as 2020. Credit: SpaceX

KENNEDY SPACE CENTER, FL – With so many exciting projects competing for the finite time of SpaceX’s super talented engineers, something important had to give. And that something comes in the form of slipping the blastoff of SpaceX’s ambitious Red Dragon initiative to land the first commercial spacecraft on Mars by 2 years – to 2020. Nevertheless it will include a hefty science payload, SpaceX’s President told Universe Today.

The Red Dragon launch postponement from 2018 to 2020 was announced by SpaceX president Gwynne Shotwell during a Falcon 9 prelaunch press conference at historic pad 39A at NASA’s Kennedy Space Center in Florida.

“We were focused on 2018, but we felt like we needed to put more resources and focus more heavily on our crew program and our Falcon Heavy program, said SpaceX Gwynne Shotwell at the pad 39a briefing.

“So we’re looking more in the 2020 time frame for that.”

And whenever Red Dragon does liftoff, it will carry a significant “science payload” to the Martian surface, Shotwell told me at the pad 39A briefing.

“As much [science] payload on Dragon as we can,” Shotwell said. Science instruments would be provided by “European and commercial guys … plus our own stuff!”

SpaceX President Gwynne Shotwell meets the media at Launch Complex 39A at the Kennedy Space Center on 17 Feb 2017 ahead of launch of the CRS-10 mission on 19 Feb 2017. Credit: Julian Leek

Another factor potentially at play is yesterdays (Feb 27) announcement by SpaceX CEO Elon Musk that he has two hefty, revenue generating paying customers for a manned Moonshot around the Moon that could blastoff on a commercial crew Dragon as soon as next year atop a Falcon Heavy from pad 39A – as I reported here.

Whereas SpaceX is footing the bill for the private Red Dragon venture.

Pad 39A is the same pad from which the Red Dragon mission will eventually blastoff atop a heavy lift SpaceX Falcon Heavy rocket – and which just reopened for launch business last week on Feb. 19 after lying dormant for more than 6 years since the retirement of NASA’s Space Shuttle Program in July 2011.

So at least the high hurdle of reopening pad 39A has been checked off!

Raindrops keep falling on the lens, as inaugural SpaceX Falcon 9/Dragon disappears into the low hanging rain clouds at NASA’s Kennedy Space Center after liftoff from pad 39A on Feb. 19, 2017. Dragon CRS-10 resupply mission is delivering over 5000 pounds of science and supplies to the International Space Station (ISS) for NASA. Credit: Ken Kremer/kenkremer.com

SpaceX continues to dream big – setting its extraterrestrial sights on the Moon and Mars.

Musk founded SpaceX with the dream of transporting Humans to the Red Planet and establishing a ‘City on Mars’.

Artists concept for sending SpaceX Red Dragon spacecraft to Mars as early as 2020. Credit: SpaceX

Since launch windows to Mars are only available every two years due to the laws of physics and planetary alignments, the minimum Red Dragon launch delay automatically amounts to 2 years.

Furthermore the oft delayed Falcon Heavy has yet to launch on its maiden mission.

Shotwell said the maiden Falcon Heavy launch from pad 39A is planned to occur this summer, around mid year or so – after Pad 40 is back up and running.

And the commercial crew Dragon 2 spacecraft being built under contract to NASA to launch American astronauts to the International Space Station (ISS) has also seen its maiden launch postponed more than six months over the past calendar year.

Finishing the commercial crew Dragon is absolutely critical to NASA for launching US astronauts to the ISS from US soil – in order to end our total dependence on Russia and the Soyuz capsule at a cost in excess of $80 million per seat.

Artistic concepts of the Falcon Heavy rocket (left) and the Dragon capsule deployed on the surface of Mars (right). Credit: SpaceX

The bold Red Dragon endeavor which involved launching an uncrewed version of the firms Dragon cargo spacecraft to carry out a propulsive soft landing on Mars as soon as 2018, was initially announced with great fanfare by SpaceX less than a year ago in April 2016.

At that time, SpaceX signed a space act agreement with NASA, wherein the agency will provide technical support to SpaceX with respect to Mars landing technologies for ‘Red Dragon’ and NASA would reciprocally benefit from SpaceX technologies for Mars landing.

But given the magnitude of the work required for this extremely ambitious Mars landing mission, the two year postponement was pretty much expected from the beginning by this author.

The main goal is to propulsively land the heaviest payload ever on Mars – something 5-10 times the size of anything landed before.

“These missions will help demonstrate the technologies needed to land large payloads propulsively on Mars,” SpaceX noted last April.

Red Dragon will utilize supersonic retropropulsion to achieve a safe touchdown.

I asked Shotwell whether Red Dragon would include a science payload? Would Universities and Industry compete to submit proposals?

“Yes we had planned to fly [science] stuff in 2018, but people are also more ready to fly in 2020 than 2018,” Shotwell replied.

“Yes we are going to put as much [science] payload on Dragon as we can. By the way, just Dragon landing alone will be the largest mass ever put on the surface of Mars. Just the empty Dragon alone. That will be pretty crazy!”

“There are a bunch of folks that want to fly [science], including European customers, commercial guys.”

“Yeah there will be [science] stuff on Dragon – plus our own stuff!” Shotwell elaborated.

Whenever it does fly, SpaceX will utilize a recycled cargo Dragon from one of the space station resupply missions for NASA, said Jessica Jensen, SpaceX Dragon Mission manager at a KSC media briefing.

NASA’s still operating 1 ton Curiosity rover is the heaviest spaceship to touchdown on the Red Planet to date.

Dramatic wide angle mosaic view of butte with sandstone layers showing cross-bedding in the Murray Buttes region on lower Mount Sharp with distant view to rim of Gale crater, taken by Curiosity rover’s Mastcam high resolution cameras. This photo mosaic was assembled from Mastcam color camera raw images taken on Sol 1454, Sept. 8, 2016 and stitched by Ken Kremer and Marco Di Lorenzo, with added artificial sky. Featured at APOD on 5 Oct 2016. Credit: NASA/JPL/MSSS/Ken Kremer/kenkremer.com/Marco Di Lorenzo

NASA’s agency wide goal is to send humans on a ‘Journey to Mars’ by the 2030s utilizing the SLS rocket and Orion deep space capsule – slated for their uncrewed maiden launch in late 2018.

Although NASA has just initiated a feasibility study to alter the mission and add 2 astronauts with a revised liftoff date of 2019.

Of course it all depends on whether the new Trump Administration bolsters NASA or slashes NASA funding.

Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.

Ken Kremer

Posted on by Matt Williams

We’re Not Saying It’s Aliens Because It’s Not Aliens. But Check Out These UFO Data Visualizations

The number of UFO sightings per year, Credit: Sam Monfort
The number of UFO sightings per year, Credit: Sam Monfort

When it comes to conspiracy theories and modern preoccupations, few things are more popular than unidentified flying objects (UFOs) and alien abductions. For over half a century, there have been rumors, reports, and urban legends about aliens coming to Earth, dabbling with our genetics, and conducting weird (and often invasive) experiments on our citizens.

And while opinions on what drives this popular phenomenon tend to differ (some say hysteria, others that it is media-driven), a few things are clear. For one, sightings appear to take place far more in the United States than anywhere else in the world. And in recent years, these sightings have been on the rise!

Such are the conclusions of a series of visualizations based on the National UFO Reporting Center (NUFORC). Established in 1974 (and located in Davenport, Washington), the National UFO Reporting Center is “dedicated to the collection and dissemination of objective UFO data”. Since that time, they have been monitoring UFO sightings worldwide and have maintained careful logs about the 104,947 sightings that have taken place since 1905.

The geographic distribution of UFO sightings. Credit: sammonfort3

Using this data, Sam Monfort – a Doctoral Candidate from the department of Human Factors & Applied Cognition at George Mason University – produced a series of visuals that illustrate the history of UFO sightings. And based on the visualized trends, some rather interesting conclusions can be drawn. The most obvious is that the geographical distribution of sightings is hardly even. For starters, reports in the USA were equal to about 2500 sightings per 10 million people.

This is almost 300 times higher than the global average. Based on individual states, the concentration of sightings was also quite interesting. Apparently, more sightings happen (per 10 million people) in the West and Northwest, with the highest numbers coming from Washington and Montana. Oregon, Idaho, Arizona and New Mexico also made strong showings, while the Great Lakes and Midwestern states were all consistent with the national median.

On the opposite coast, Maine, Vermont, and New Hampshire all had a good number of sightings per capita, though the state of New York even as New York was beneath the national median. Texas actually ranked the lowest, and was followed by the Southern states of Louisiana, Mississippi, Alabama and Georgia. But as Monfort told Universe Today via email, this may be slightly skewed because of who is collecting the information:

“[I]t’s worth mentioning that the NUFORC is an American agency (“N” stands for “National”). They make an effort to record international sightings (phone banks staffed 24/7), but I’d guess that sightings in the USA are still over-represented. Honestly, I’d bet that the NUFORC being based in Seattle is the main reason we see so many more sightings in the States. A more thorough analysis might cross-reference sightings from other agencies, like MUFON.”

The geographic breakdown of annual UFO sightings (per 10 million people) in the US. Credit: sammonfort3

Canadians did not do much better, coming at second place after the United States with 1000 sightings per 10 million people. And according to a recent article by Allan Maki of The Globe and Mail, its becoming more common – with a record 1982 sightings reported in 2012. He also suggests that this could be due to a combination of growing interest in the subject and reduced stigma.

Iceland, the UK, Australia, the Virgin Islands and Cyprus all ranked a distant third, with between 250 and 500 sightings per 100 million people per year. New Zealand, Mexico, Israel and the Gulf States also produced considerable returns, as did the United Kingdom, Ireland, Portugal, Belgium, Danemark, Finland, Sweden and Norway.

From this distribution, one might make the generalization that more developed nations are more likely to report UFOs (i.e. better record-keeping and all that). And this is a possibility which Monfort explored. In another visualization, he cross-referenced the number of sightings in a respective country with amount of internet access it has (per 100 people), and a limited correlation was shown.

Nations like Israel and the Gulf States have a higher number of sightings than neighboring countries like Syria, Saudi Arabia and Iraq, while South Africa has more reported sightings than several North African and Sub-Saharan African nations surveyed. However, fast-developing nations like Russia, China and India showed a lower than average level of sightings, while Guyana and Suriname showed a higher than average level.

The number of UFO sightings per year, subdivided based on the type of object reported. Credit: sammonfort3

France, Italy and the Czech Republic also lagged behind many of their European counterparts, and Germany and Spain were only slightly higher than the average. So much like distribution by state within the US, internet access does not seem to be a consistent determining factor. Another interesting visualization was the one which broke down the sightings per decade based on the nature of the sighting.

As you can see from the table above, when UFO sightings first began in the early 20th century, they reportedly took the form of either a sphere or a cigar-shaped object. This differs from the 1920s, when “flying saucers” began to appear, and remained the dominant trend throughout World War II and the Cold War era. And ever since the 1990s – what Monfort refers to as “post-internet” era – the most common UFO sightings took the form of bright lights.

“If I had to guess, I’d say it was a combination of factors,” said Monfort. “Like I mentioned in the blog, it seems a lot more plausible that someone would see strange lights in the sky than a flying object with a concrete shape (like a saucer). Seeing a shape implies that the object is pretty close to you, “and if it’s that close why didn’t you take a video of it?”

As for other factors, Monfort considers the possibility of fireworks and (as one comment on his blog suggested) Chinese lanterns. “Those are the little paper balloons you light a candle in and let fly. Some of the bright light sightings could be those, especially since I’d bet most Chinese lanterns are released in groups, with several people going out in groups to release them together. (Often people report formations of lights.)”

Naturally, the data does not support any ironclad conclusions, and plenty can be said about its reliability and methodology. After all, while UFO sightings are documented, they are famous for being routinely debunked. Nevertheless, visuals like these are interesting in illustrated the patterns of sightings, and can allow for some insightful speculation as to why they take place.

Further Reading: Visualize This