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

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.

February 28, 2017May 2, 2017 by Evan Gough

Rise of the Super Telescopes: The Overwhelmingly Large Telescope

The 100 meter OWL telescope would have operated in the open air, and then been stored in its enclosure when not in use. Image: ESO Telescope Systems Division

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 Giant Magellan Telescope
The Overwhelmingly Large Telescope
The 30 Meter Telescope
The European Extremely Large Telescope
The Large Synoptic Survey Telescope
The James Webb Space Telescope
The Wide Field Infrared Survey Telescope

The Overwhelmingly Large Telescope

The OWL (Overwhelmingly Large Telescope) was a gargantuan telescope proposed by the European Southern Observatory (ESO). The OWL was going to be a 100 meter monstrosity, which would dwarf anything in operation at the time. Sadly, OWL was eventually cancelled.

For now, anyway.

At the time that OWL was first proposed—in the late 1990’s—scientific studies showed that huge telescopes would be necessary to advance our knowledge. OWL promised to help us unlock the mystery of dark matter, peer back in time to witness the birth of the first stars and galaxies, and to directly image the atmospheres of exoplanets. It’s easy to see why people were excited by OWL.

This image simulates the increased resolving power of the OWL compared to its contemporaries. Image: ESO Telescope Systems Division

By 2005, the OWL study was completed and reviewed by a panel of experts. At that time, the concept was validated as a cost-effective way to build an Extremely Large Telescope (ELT). However, as the wheels kept turning, and a price tag of € 1.5 billion was attached to it, the ESO backed away.

OWL’s design called for a 100 meter diameter mirror, built out of 3264 segments. It would have had unequalled light-gathering capacity, and the ability to resolve details down to a milli-arc second. (A milli-arc second is approximately the size of a dime, placed on top of the Eiffel Tower, and viewed from New York City.) That’s extremely impressive to say the least. And OWL would have operated in both visible light and infrared.

Everything about OWL’s design was modular, in an effort to keep costs down. Image: ESO Telescope Systems Division

The problem with OWL was the cost, not the design feasibility. Engineers still think the design is feasible. In fact, the construction of the mirrors was pretty well-understood, and perhaps the most challenging part of the OWL was the adaptive optics required.

It’s a fact of large telescopes that they have to be constantly adjusted to produce sharp images. This requires adaptive optics. The adaptive optics required for OWL would have pushed the state-of-the-art technology at the time.

Adaptive optics is a method of overcoming the distortions that affect light as they pass through Earth’s atmosphere. For extremely sensitive telescopes like the OWL, the atmosphere of Earth is problematic. The photons coming from the distant reaches of the Universe can be garbled by the atmosphere as they approach the telescope. Telescopes are built on mountain-tops to reduce how much atmosphere photons have to travel through, but that’s not enough.

This video explains how adaptive optics work, and how they helped the Keck telescope make new discoveries.

OWL’s mirror segments would have to be aligned to within a fraction of the wavelength (0.0005 mm for visible light) in order for the telescope to deliver good images. OWL’s adaptive optics would have achieved this by adjusting each of OWL’s 3264 segments rapidly, sometimes several times per second.

OWL’s design called for modularity, or “serial, industrialized fabrication of identical building blocks” to reduce costs. The manufacture of extremely large telescopes is expensive, but so are the transportation costs. All of the components have to be built in engineering and manufacturing centres, then shipped to, and assembled on, fairly remote mountain tops. OWL’s components were designed to be shipped in standard shipping containers, which simplified that aspect of its construction.

This graphic shows the sizes of the world’s telescopes superimposed over the OWL. By Cmglee – Own workiThe source code of this SVG is valid., CC BY-SA 3.0, https://commons.wikimedia.org/w/index.php?curid=33613161

In fact, OWL could have begun operation before all of its mirrors were in place, and would have grown in power as more mirror segments were built and integrated. (Other telescopes, like the Giant Magellan Telescope (GMT) will be in operation before all of the mirrors are installed.)

In the end, OWL’s cost became too great, and the project was cancelled. The ESO moved on to the 39.3 meter European Extremely Large Telescope. But all of the work done on the design of OWL was not lost.

Everything that we learn about telescope design trickles down to our next-generation of telescopes. That’s true whether designs like OWL get built or not. We’ll just keep building on our success, and keep building larger and more powerful telescopes.

The adaptive optics that OWL required were a challenge. But huge advances have been made on that front. And in the way of things, the manufacturing costs have likely come down as well.

OWL itself may never be built, but other ‘scopes are on the way. Telescopes like the James Webb Space Telescope, the Giant Magellan Telescope, and the European Extremely Large Telescope hold the same promise that OWL did.

And in the end, the contributions of those and other ‘scopes might surpass those promised by OWL.

February 27, 2017May 2, 2017 by Evan Gough

Rise of the Super Telescopes: The Giant Magellan Telescope

The Giant Magellan Telescope is under construction in Chile and should see first light sometime in the early 2020s. Image: Giant Magellan Telescope – GMTO Corporation

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

The Giant Magellan Telescope
The Overwhelmingly Large Telescope
The 30 Meter Telescope
The European Extremely Large Telescope
The Large Synoptic Survey Telescope
The James Webb Space Telescope
The Wide Field Infrared Survey Telescope

The Giant Magellan Telescope

The Giant Magellan Telescope (GMT) is being built in Chile, at the Las Campanas Observatory, home of the GMT’s predecessors the Magellan Telescopes. The Atacama region of Chile is an excellent location for telescopes because of its superb seeing conditions. It’s a high-altitude desert, so it’s extremely dry and cool there, with little light pollution.

The GMT is being built by the USA, Australia, South Korea, and Brazil. It started facility construction in 2015, and first light should be in the early 2020’s.

The heart of the Giant Magellan Telescope is the segmented primary mirror. Image: Giant Magellan Telescope – GMTO Corporation

Segmented mirrors are the peak of technology when it comes to super telescopes, and the GMT is built around this technology.

The GMT’s primary mirror consists of 7 separate mirrors: one central mirror surrounded by 6 other mirrors. Together they form an optical surface that is 24.5 meters (80 ft.) in diameter. That means the GMT will have a total light collecting area of 368 square meters, or almost 4,000 square feet. The GMT will outperform the Hubble Space Telescope by having a resolving power 10 times greater.

There’s a limit to the size of single mirrors that can be built, and the 8.4 meter mirrors in the GMT are at the limits of construction methods. That’s why segmented systems are in use in the GMT, and in other super telescopes being designed and built around the world.

These mirrors are modern feats of engineering. Each one is made of 20 tons of glass, and takes years to build. The first mirror was cast in 2005, and was still being polished 6 years later. In fact, the mirrors are so massive, that they need 6 months to cool when they come out of casting.

They aren’t just flat, simple mirrors. They’re described as potato chips, rather than being flat. They’re aspheric, meaning the mirrors’ faces have steeply curved surfaces. The mirror’s have to have exactly the same curvature in order to perform together, which requires leading-edge manufacturing. The mirrors’ paraboloidal shape has to be polished to an accuracy greater than 25 nanometers. That’s about 1/25th the wavelength of light itself!

In fact, if you took one of the GMT’s mirrors and spread it out from the east coast to the west coast of the USA, the height of the tallest mountain on the mirror would be only 1/2 of one inch.

The plan is for the Giant Magellan Telescope to begin operation with only four of its mirrors. The GMT will also have an extra mirror built, just for contingencies.

The construction of the GMT’s mirrors required entirely new testing methods and equipment to achieve these demanding accuracies. The entire task fell on the University of Arizona’s Richard F. Caris Mirror Lab.

But GMT is more than just its primary mirror. It also has a secondary mirror, which is also segmented. Each one of the secondary mirror’s segments must work in concert with its matching segment on the primary mirror, and the distance from secondary mirror to primary mirror has to be measured within one part in 500 million. That requires exacting engineering for the steel structure of the body of the telescope.

The engineering behind the GMT is extremely demanding, but once it’s in operation, what will it help us learn about the Universe?

“I think the really exciting things will be things that we haven’t yet though of.” -Dr. Robert Kirshner

The GMT will help us tackle multiple mysteries in the Universe, as Dr. Robert Kirshner, of the Harvard-Smithsonian Center for Astrophysics, explains in this video.

The scientific aims of the GMT are well laid out, and there aren’t really any surprises. The goals of the GMT are to increase our understanding of some fundamental aspects of our Universe:

Star, planet, and disk formation
Extrasolar planetary systems
Stellar populations and chemical evolution
Galaxy assembly and evolution
Fundamental physics
First light and reionization

The GMT will collect more light than any other telescope we have, which is why its development is so keenly followed. It will be the first ‘scope to directly image extrasolar planets, which will be enormously exciting. With the GMT, we may be able to see the color of planets, and maybe even weather systems.

We’re accustomed to seeing images of Jupiter’s storm bands, and weather phenomena on other planets in our Solar System, but to be able to see something like that on extra-solar planets will be astounding. That’s something that even the casual space-interested person will immediately be fascinated by. It’s like science fiction come to life.

Of course, we’re still a ways away from any of that happening. With first light not anticipated until the early 2020’s, we’ll have to be very patient.

February 14, 2017February 14, 2017 by Evan Gough

Chance Discovery Of A Three Hour Old Supernova

Artistic impression of a star going supernova, casting its chemically enriched contents into the universe. Credit: NASA/Swift/Skyworks Digital/Dana Berry

Supernovae are extremely energetic and dynamic events in the universe. The brightest one we’ve ever observed was discovered in 2015 and was as bright as 570 billion Suns. Their luminosity signifies their significance in the cosmos. They produce the heavy elements that make up people and planets, and their shockwaves trigger the formation of the next generation of stars.

There are about 3 supernovae every 100 hundred years in the Milky Way galaxy. Throughout human history, only a handful of supernovae have been observed. The earliest recorded supernova was observed by Chinese astronomers in 185 AD. The most famous supernova is probably SN 1054 (historic supernovae are named for the year they were observed) which created the Crab Nebula. Now, thanks to all of our telescopes and observatories, observing supernovae is fairly routine.

The supernova that produced the Crab Nebula was detected by naked-eye observers around the world in 1054 A.D. This composite image uses data from NASA’s Great Observatories, Chandra, Hubble, and Spitzer, to show that a superdense neutron star is energizing the expanding Nebula by spewing out magnetic fields and a blizzard of extremely high-energy particles. The Chandra X-ray image is shown in light blue, the Hubble Space Telescope optical images are in green and dark blue, and the Spitzer Space Telescope’s infrared image is in red. The size of the X-ray image is smaller than the others because ultrahigh-energy X-ray emitting electrons radiate away their energy more quickly than the lower-energy electrons emitting optical and infrared light. The neutron star is the bright white dot in the center of the image. — The supernova that produced the Crab Nebula was detected by naked-eye observers around the world in 1054 A.D. This composite image uses data from NASA’s Great Observatories, Chandra, Hubble, and Spitzer.

But one thing astronomers have never observed is the very early stages of a supernova. That changed in 2013 when, by chance, the automated Intermediate Palomar Transient Factory (IPTF) caught sight of a supernova only 3 hours old.

Spotting a supernovae in its first few hours is extremely important, because we can quickly point other ‘scopes at it and gather data about the SN’s progenitor star. In this case, according to a paper published at Nature Physics, follow-up observations revealed a surprise: SN 2013fs was surrounded by circumstellar material (CSM) that it ejected in the year prior to the supernova event. The CSM was ejected at a high rate of approximately 10 -³ solar masses per year. According to the paper, this kind of instability might be common among supernovae.

SN 2013fs was a red super-giant. Astronomers didn’t think that those types of stars ejected material prior to going supernova. But follow up observations with other telescopes showed the supernova explosion moving through a cloud of material previously ejected by a star. What this means for our understanding of supernovae isn’t clear yet, but it’s probably a game changer.

Catching the 3-hour-old SN 2013fs was an extremely lucky event. The IPTF is a fully-automated wide-field survey of the sky. It’s a system of 11 CCD’s installed on a telescope at the Palomar Observatory in California. It takes 60 second exposures at frequencies from 5 days apart to 90 seconds apart. This is what allowed it to capture SN 2013fs in its early stages.

The 48 inch telescope at the Palomar Observatory. The IPTF is installed on this telescope. Image: IPTF/Palomar Observatory

Our understanding of supernovae is a mixture of theory and observed data. We know a lot about how they collapse, why they collapse, and what types of supernovae there are. But this is our first data point of a SN in its early hours.

SN 2013fs is 160 million light years away in a spiral-arm galaxy called NGC7610. It’s a type II supernova, meaning that it’s at least 8 times as massive as our Sun, but not more than 50 times as massive. Type II supernovae are mostly observed in the spiral arms of galaxies.

A supernova is the end state of some of the stars in the universe. But not all stars. Only massive stars can become supernova. Our own Sun is much too small.

Stars are like dynamic balancing acts between two forces: fusion and gravity.

As hydrogen is fused into helium in the center of a star, it causes enormous outward pressure in the form of photons. That is what lights and warms our planet. But stars are, of course, enormously massive. And all that mass is subject to gravity, which pulls the star’s mass inward. So the fusion and the gravity more or less balance each other out. This is called stellar equilibrium, which is the state our Sun is in, and will be in for several billion more years.

But stars don’t last forever, or rather, their hydrogen doesn’t. And once the hydrogen runs out, the star begins to change. In the case of a massive star, it begins to fuse heavier and heavier elements, until it fuses iron and nickel in its core. The fusion of iron and nickel is a natural fusion limit in a star, and once it reaches the iron and nickel fusion stage, fusion stops. We now have a star with an inert core of iron and nickel.

Now that fusion has stopped, stellar equilibrium is broken, and the enormous gravitational pressure of the star’s mass causes a collapse. This rapid collapse causes the core to heat again, which halts the collapse and causes a massive outwards shockwave. The shockwave hits the outer stellar material and blasts it out into space. Voila, a supernova.

The extremely high temperatures of the shockwave have one more important effect. It heats the stellar material outside the core, though very briefly, which allows the fusion of elements heavier than iron. This explains why the extremely heavy elements like uranium are much rarer than lighter elements. Only large enough stars that go supernova can forge the heaviest elements.

In a nutshell, that is a type II supernova, the same type found in 2013 when it was only 3 hours old. How the discovery of the CSM ejected by SN 2013fs will grow our understanding of supernovae is not fully understood.

Supernovae are fairly well-understood events, but their are still many questions surrounding them. Whether these new observations of the very earliest stages of a supernovae will answer some of our questions, or just create more unanswered questions, remains to be seen.

February 8, 2017February 15, 2017 by Evan Gough

The Magellenic Clouds Stay Connected By A String Of Stars

This image shows the two "bridges" that connect the Large and Small Magellanic Clouds. The white line traces the bridge of stars that flows between the two dwarf galaxies, and the blue line shows the gas. Image: V. Belokurov, D. Erkal and A. Mellinger

Astronomers have finally observed something that was predicted but never seen: a stream of stars connecting the two Magellanic Clouds. In doing so, they began to unravel the mystery surrounding the Large Magellanic Cloud (LMC) and the Small Magellanic Cloud (SMC). And that required the extraordinary power of the European Space Agency’s (ESA) Gaia Observatory to do it.

The Large and Small Magellanic Clouds (LMC and SMC) are dwarf galaxies to the Milky Way. The team of astronomers, led by a group at the University of Cambridge, focused on the clouds and on one particular type of very old star: RR Lyrae. RR Lyrae stars are pulsating stars that have been around since the early days of the Clouds. The Clouds have been difficult to study because they sprawl widely, but Gaia’s unique all-sky view has made this easier.

Small and Large Magellanic Clouds over Paranal Observatory Credit: ESO/J. Colosimo

The Mystery: Mass

The Magellanic Clouds are a bit of a mystery. Astronomers want to know if our conventional theory of galaxy formation applies to them. To find out, they need to know when the Clouds first approached the Milky Way, and what their mass was at that time. The Cambridge team has uncovered some clues to help solve this mystery.

The team used Gaia to detect RR Lyrae stars, which allowed them to trace the extent of the LMC, something that has been difficult to do until Gaia came along. They found a low-luminosity halo around the LMC that stretched as far as 20 degrees. For the LMC to hold onto stars that far away means it would have to be much more massive than previously thought. In fact, the LMC might have as much as 10 percent of the mass that the Milky Way has.

The Large Magellanic Cloud. Image: Public Domain, https://commons.wikimedia.org/w/index.php?curid=57110

The Arrival of the Magellanic Clouds

That helped astronomers answer the mass question, but to really understand the LMC and SMC, they needed to know when the clouds arrived at the Milky Way. But tracking the orbit of a satellite galaxy is impossible. They move so slowly that a human lifetime is a tiny blip compared to them. This makes their orbit essentially unobservable.

But astronomers were able to find the next best thing: the often predicted but never observed stellar stream, or bridge of stars, stretching between the two clouds.

A star stream forms when a satellite galaxy feels the gravitational pull of another body. In this case, the gravitational pull of the LMC allowed individual stars to leave the SMC and be pulled toward the LMC. The stars don’t leave at once, they leave individually over time, forming a stream, or bridge, between the two bodies. This action leaves a luminous tracing of their path over time.

The astronomers behind this study think that the bridge actually has two components: stars stripped from the SMC by the LMC, and stars stripped from the LMC by the Milky Way. This bridge of RR Lyrae stars helps them understand the history of the interactions between all three bodies.

A Bridge of Stars… and Gas

The most recent interaction between the Clouds was about 200 million years ago. At that time, the Clouds passed close by each other. This action formed not one, but two bridges: one of stars and one of gas. By measuring the offset between the star bridge and the gas bridge, they hope to narrow down the density of the corona of gas surrounding the Milky Way.

Mystery #2: The Milky Way’s Corona

The density of the Milky Way’s Galactic Corona is the second mystery that astronomers hope to solve using the Gaia Observatory.

The Galactic Corona is made up of ionised gas at very low density. This makes it very difficult to observe. But astronomers have been scrutinizing it intensely because they think the corona might harbor most of the missing baryonic matter. Everybody has heard of Dark Matter, the matter that makes up 95% of the matter in the universe. Dark Matter is something other than the normal matter that makes up familiar things like stars, planets, and us.

The other 5% of matter is baryonic matter, the familiar atoms that we all learn about. But we can only account for half of the 5% of baryonic matter that we think has to exist. The rest is called the missing baryonic matter, and astronomers think it’s probably in the galactic corona, but they’ve been unable to measure it.

A part of the Small Magellanic Cloud galaxy is dazzling in this image from NASA’s Great Observatories. The Small Magellanic Cloud is about 200,000 light-years way from our own Milky Way spiral galaxy. Credit: NASA.

Understanding the density of the Galactic Corona feeds back into understanding the Magellanic Clouds and their history. That’s because the bridges of stars and gas that formed between the Small and Large Magellanic Clouds initially moved at the same speed. But as they approached the Milky Way’s corona, the corona exerted drag on the stars and the gas. Because the stars are small and dense relative to the gas, they travelled through the corona with no change in their velocity.

But the gas behaved differently. The gas was largely neutral hydrogen, and very diffuse, and its encounter with the Milky Way’s corona slowed it down considerably. This created the offset between the two streams.

Eureka?

The team compared the current locations of the streams of gas and stars. By taking into account the density of the gas, and also how long both Clouds have been in the corona, they could then estimate the density of the corona itself.

When they did so, their results showed that the missing baryonic matter could be accounted for in the corona. Or at least a significant fraction of it could. So what’s the end result of all this work?

It looks like all this work confirms that both the Large and Small Magellanic Clouds conform to our conventional theory of galaxy formation.

Mystery solved. Way to go, science.

January 31, 2017February 15, 2017 by Evan Gough

Vortex Coronagraph A Game Changer For Seeing Close In Exoplanets

The vortex coronagraph at the Keck Observatory captured this image of the protoplanetary disk surrounding the young star HD 141569. which is about 380 light years from Earth. Image: NASA/JPL-Caltech — The vortex coronagraph at the Keck Observatory captured this image of the protoplanetary disk surrounding the young star HD 141569, which is about 380 light years from Earth. Image: NASA/JPL-Caltech

The study of exoplanets has advanced a great deal in recent years, thanks in large part to the Kepler mission. But that mission has its limitations. It’s difficult for Kepler, and for other technologies, to image regions close to their stars. Now a new instrument called a vortex coronagraph, installed at Hawaii’s Keck Observatory, allows astronomers to look at protoplanetary disks that are in very close proximity to the stars they orbit.

The problem with viewing disks of dust, and even planets, close to their stars is that stars are so much brighter than objects that orbit them. Stars can be billions of times brighter than the planets near them, making it almost impossible to see them in the glare. “The power of the vortex lies in its ability to image planets very close to their star, something that we can’t do for Earth-like planets yet,” said Gene Serabyn of NASA’s Jet Propulsion Laboratory (JPL). “The vortex coronagraph may be key to taking the first images of a pale blue dot like our own.”

“The power of the vortex lies in its ability to image planets very close to their star, something that we can’t do for Earth-like planets yet.” – Gene Serabyn, JPL.

“The vortex coronagraph allows us to peer into the regions around stars where giant planets like Jupiter and Saturn supposedly form,” said Dmitri Mawet, research scientist at NASA’s Jet Propulsion Laboratory and Caltech, both in Pasadena. “Before now, we were only able to image gas giants that are born much farther out. With the vortex, we will be able to see planets orbiting as close to their stars as Jupiter is to our sun, or about two to three times closer than what was possible before.”

Rather than masking the light of stars, like other methods of viewing exoplanets, the vortex coronagraph redirects light away from the detectors by combining light waves and cancelling them out. Because there is no occulting mask, the vortex coronagraph can capture images of regions much closer to stars than other coronagraphs can. Dmitri Mawet, research scientist who invented the new coronagraph, compares it to the eye of a storm.

The vortex mask shown at left is made out of synthetic diamond. When viewed with a scanning electron microscope, right, the "vortex" microstructure of the mask is revealed. Image credit: University of Liège/Uppsala University — The vortex mask shown at left is made out of synthetic diamond. When viewed with a scanning electron microscope, right, the “vortex” microstructure of the mask is revealed. Image credit: University of Liège/Uppsala University

“The instrument is called a vortex coronagraph because the starlight is centered on an optical singularity, which creates a dark hole at the location of the image of the star,” said Mawet. “Hurricanes have a singularity at their centers where the wind speeds drop to zero — the eye of the storm. Our vortex coronagraph is basically the eye of an optical storm where we send the starlight.”

The results from the vortex coronagraph are presented in two papers (here and here) published in the January 2017 Astronomical Journal. One of the studies was led by Gene Serabyn of JPL, who is also head of the Keck vortex project. That study presented the first direct image of HIP79124 B, a brown dwarf that is 23 AU from its star, in the star-forming region called Scorpius-Centaurus.

The vortex coronagraph captured this image of the brown dwarf PIA21417. Image: NASA/JPL-Caltech

“The ability to see very close to stars also allows us to search for planets around more distant stars, where the planets and stars would appear closer together. Having the ability to survey distant stars for planets is important for catching planets still forming,” said Serabyn.

“Having the ability to survey distant stars for planets is important for catching planets still forming.” – Gene Serabyn, JPL.

The second of the two vortex studies presented images of a protoplanetary disk around the young star HD141569A. That star actually has three disks around it, and the coronagraph was able to capture an image of the innermost ring. Combining the vortex data with data from the Spitzer, WISE, and Herschel missions showed that the planet-forming material in the disk is made up pebble-size grains of olivine. Olivine is one of the most abundant silicates in Earth’s mantle.

“The three rings around this young star are nested like Russian dolls and undergoing dramatic changes reminiscent of planetary formation,” said Mawet. “We have shown that silicate grains have agglomerated into pebbles, which are the building blocks of planet embryos.”

These images and studies are just the beginning for the vortex coronagraph. It will be used to look at many more young planetary systems. In particular, it will look at planets near so-called ‘frost lines’ in other solar systems. The is the region around star systems where it’s cold enough for molecules like water, methane, and carbon dioxide to condense into solid, icy grains. Current thinking says that the frost line is the dividing line between where rocky planets and gas planets are formed. Astronomers hope that the coronagraph can answer questions about hot Jupiters and hot Neptunes.

Hot Jupiters and Neptunes are large gaseous planets that are found very close to their stars. Astronomers want to know if these planets formed close to the frost line then migrated inward towards their stars, because it’s impossible for them to form so close to their stars. The question is, what forces caused them to migrate inward? “With a bit of luck, we might catch planets in the process of migrating through the planet-forming disk, by looking at these very young objects,” Mawet said.

January 25, 2017January 26, 2017 by Ken Kremer

NASA Webb Telescope Resumes Rigorous Vibration Qualification Tests

NASA engineers and technicians position the James Webb Space Telescope (inside a large tent) onto the shaker table used for vibration testing. Credits: NASA/Chris Gunn

Engineers have resumed a series of critical and rigorous vibration qualification tests on NASA’s mammoth James Webb Space Telescope (JWST) at NASA’s Goddard Space Flight Center, in Greenbelt, Maryland to confirm its safety, integrity and readiness for the unforgiving environment of space flight, after pausing due to a testing ‘anomaly’ detected in early December 2016.

The vibration tests are conducted by the team on a shaker table at Goddard to ensure Webb’s worthiness and that it will survive the rough and rumbling ride experienced during the thunderous rocket launch to the heavens slated for late 2018.

“Testing on the ground is critical to proving a spacecraft is safe to launch,” said Lee Feinberg, an engineer and James Webb Space Telescope Optical Telescope Element Manager at Goddard, in a statement.

“The Webb telescope is the most dynamically complicated article of space hardware that we’ve ever tested.”

The 18-segment gold coated primary mirror of NASA’s James Webb Space Telescope is raised into vertical alignment in the largest clean room at the agency’s Goddard Space Flight Center in Greenbelt, Maryland, on Nov. 2, 2016. The secondary mirror mount booms are folded down into stowed for launch configuration. Credit: Ken Kremer/kenkremer.com

Testing of the gargantuan Webb Telescope had ground to a halt after a brief scare in early December when technicians initially detected “anomalous readings” that raised potential concerns about the observatories structural integrity partway through a preplanned series of vibration tests.

“On December 3, 2016, vibration testing automatically shut down early due to some sensor readings that exceeded predicted levels,” officials said.

Thereafter, engineers and technicians carried out a new batch of intensive inspections of the observatory’s structure during December.

Shortly before Christmas, NASA announced on Dec. 23 that JWST was deemed “sound” and apparently unscathed after engineers conducted both “visual and ultrasonic examinations” at NASA’s Goddard Space Flight Center in Maryland. Officials said the telescope was found to be safe at this point with “no visible signs of damage.”

As it turned out the culprit of the sensor anomaly was the many “tie-down … restraint mechanisms ” that hold the telescope in place.

“After a thorough investigation, the James Webb Space Telescope team at NASA Goddard determined that the cause was extremely small motions of the numerous tie-downs or “launch restraint mechanisms” that keep one of the telescope’s mirror wings folded-up for launch,” NASA officials explained in a statement.

Furthermore engineers revealingly discovered that “the ground vibration test itself is more severe than the launch vibration environment.”

Technicians work on the James Webb Space Telescope in the massive clean room at NASA’s Goddard Space Flight Center, Greenbelt, Maryland, on Nov. 2, 2016, as the completed golden primary mirror and observatory structure stands gloriously vertical on a work stand, reflecting incoming light from the area and observation deck. Credit: Ken Kremer/kenkremer.com

NASA reported today (Jan. 25) that the testing resumed last week at the point where it had been paused. Furthermore the testing was completed along the first of three axis.

“In-depth analysis of the test sensor data and detailed computer simulations confirmed that the input vibration was strong enough and the resonance of the telescope high enough at specific vibration frequencies to generate these tiny motions. Now that we understand how it happened, we have implemented changes to the test profile to prevent it from happening again,” explained Feinberg.

“We have learned valuable lessons that will be applied to the final pre-launch tests of Webb at the observatory level once it is fully assembled in 2018. Fortunately, by learning these lessons early, we’ve been able to add diagnostic tests that let us show how the ground vibration test itself is more severe than the launch vibration environment in a way that can give us confidence that the launch itself will be fully successful.”

The next step is to resume and complete shaking the telescope in the other two axis, or “two directions to show that it can withstand vibrations in all three dimensions.”

“This was a great team effort between the NASA Goddard team, Northrop Grumman, Orbital ATK, Ball Aerospace, the European Space Agency, and Arianespace,” Feinberg said. “We can now proceed with the rest of the planned tests of the telescope and instruments.”

NASA’s James Webb Space Telescope is the most powerful space telescope ever built and is the scientific successor to the phenomenally successful Hubble Space Telescope (HST). The mammoth 6.5 meter diameter primary mirror has enough light gathering capability to scan back over 13.5 billion years and see the formation of the first stars and galaxies in the early universe.

The Webb telescope will launch on an ESA Ariane V booster from the Guiana Space Center in Kourou, French Guiana in 2018.

But Webb and its 18 segment “golden” primary mirror have to be carefully folded up to fit inside the nosecone of the Ariane V booster.

“Due to its immense size, Webb has to be folded-up for launch and then unfolded in space. Prior generations of telescopes relied on rigid, non-moving structures for their stability. Because our mirror is larger than the rocket fairing we needed structures folded for launch and moved once we’re out of Earth’s atmosphere. Webb is the first time we’re building for both stability and mobility.” Feinberg said.

“This means that JWST testing is very unique, complex, and challenging.”

View showing actual flight structure of mirror backplane unit for NASA’s James Webb Space Telescope (JWST) that holds 18 segment primary mirror array and secondary mirror mount at front, in stowed-for-launch configuration. JWST is being assembled here by technicians inside the world’s largest cleanroom at NASA Goddard Space Flight Center, Greenbelt, Md. Credit: Ken Kremer/kenkremer.com

The environmental testing is being done at Goddard before shipping the huge structure to NASA’s Johnson Space Center in February 2017 for further ultra low temperature testing in the cryovac thermal vacuum chamber.

The 6.5 meter diameter ‘golden’ primary mirror is comprised of 18 hexagonal segments – looking honeycomb-like in appearance.

And it’s just mesmerizing to gaze at – as I had the opportunity to do on a few occasions at Goddard this past year – standing vertically in November and seated horizontally in May.

Each of the 18 hexagonal-shaped primary mirror segments measures just over 4.2 feet (1.3 meters) across and weighs approximately 88 pounds (40 kilograms). They are made of beryllium, gold coated and about the size of a coffee table.

All 18 gold coated primary mirrors of NASA’s James Webb Space Telescope are seen fully unveiled after removal of protective covers installed onto the backplane structure, as technicians work inside the massive clean room at NASA’s Goddard Space Flight Center in Greenbelt, Maryland on May 3, 2016. The secondary mirror mount booms are folded down into stowed for launch configuration. Credit: Ken Kremer/kenkremer.com

The Webb Telescope is a joint international collaborative project between NASA, the European Space Agency (ESA) and the Canadian Space Agency (CSA).

Webb is designed to look at the first light of the Universe and will be able to peer back in time to when the first stars and first galaxies were forming. It will also study the history of our universe and the formation of our solar system as well as other solar systems and exoplanets, some of which may be capable of supporting life on planets similar to Earth.

Gold coated primary mirrors newly exposed on spacecraft structure of NASA’s James Webb Space Telescope inside the massive clean room at NASA’s Goddard Space Flight Center in Greenbelt, Maryland on May 3, 2016. Aft optics subsystem stands upright at center of 18 mirror segments between stowed secondary mirror mount booms. Credit: Ken Kremer/kenkremer.com

Watch this space for my ongoing reports on JWST mirrors, science, construction and testing.

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

Ken Kremer

James Webb Space Telescope. Image credit: NASA/JPL

December 31, 2016January 5, 2017 by Fraser Cain

Our Free Book: 101 Astronomical Events in 2017

Let’s forget all about 2016, and instead look forward to the amazing 2017 we all know we’re going to have. And to help you celebrate this amazing year in space, we’re pleased to publish an entire book on what you can observe in the upcoming year: 101 Astronomical Events in 2017.

This totally free ebook was written by our own David Dickinson and contains all the predictable events coming up: the occultations, the eclipses, the meteor showers, the equinoxes, the super-moons and mini-moons. Every significant event coming up in 2017.

In addition, a few amateur astronomers like Cory Schmitz from PhotographingSpace and the Upside Down Astronomer Paul Stewart provided some of the beautiful photographs to inspire you to get outside.

Once again, this book is totally free. There’s no cost to purchase it, there are no advertisements in it. All we ask is that you get out there, enjoy the night sky with your friends and family, and take amazing pictures to share with us and the rest of astronomy community.

Well, it would also really help if you shared the book with your friends, family, astronomy club, and forums.

This is an experiment. Will you download and actually use it? If so, then expect us to release a new edition every year. If not, then, we’ll go back to the regular blog post version.

Thanks again to David for putting in an enormous amount of work 6 months ago to think through an entire year of observing, and to the readers and photographers who helped doublecheck the math to make sure it’s accurate.

Click here to download a copy in PDF format, or click here to download a copy in EPUB format.

Also, here’s a great Google Calendar link to all 101 events courtesy of Christopher Becke (@BeckePhysics)… thanks Chris!

Fraser Cain
Publisher, Universe Today

November 11, 2016 by Evan Gough

Princeton Team Directly Observes Planets Around Nearby Stars

The Subaru Telescope atop Mauna Kea. CHARIS works in conjunction with Subaru. Image: Dr. Hideaki Fujiwara - Subaru Telescope, NAOJ.

The revelation that there are thousands of planets out there, orbiting other stars, is mostly due to the success of the Kepler mission. But now that we know these exoplanets are there, we want to know all about them. We want to know their mass, their temperature, how old they are, and pretty much everything else about them.

Now, a new instrument called the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS) has captured the light from one of those exoplanets. This has the researchers excited about what they can see.

“We couldn’t have been more pleased by the results.” – N. Jeremy Kasdin

CHARIS allows astronomers to isolate light reflecting from planets. That’s difficult to do, since they are so much dimmer than the stars they orbit. CHARIS is able to isolate the reflective light from planets larger than Jupiter. Then astronomers can analyze that light to learn about the planet’s age, atmospheric composition, and its size.

“By analyzing the spectrum of a planet, we can really understand a lot about the planet. You can see specific features that can allow you to understand the mass, the temperature, the age of the planet.” – team member Tyler Groff

This image from the CHARIS instrument shows planets located around a star in the planetary system HR8799. Image: N. Jeremy Kasdin and team.

CHARIS was designed and built by a team led by N. Jeremy Kasdin, a professor of mechanical and aerospace engineering at Princeton University. It took them five years to build CHARIS.

The spectrograph sits inside a 500 lb case that measures 30x30x12. Inside that case, it’s kept at -223.15 Celsius (50 Kelvin, -369 F.) The CHARIS instrument has nine mirrors, five filters, two prism assemblies and a microlens array. The microlens array is a special optical device with an array of tiny lenses etched into its surface.

During a CHARIS field test, researchers captured images of celestial objects, including vapor clouds moving across a section of the planet Neptune. (Images courtesy of N. Jeremy Kasdin and the research team)

CHARIS works in conjunction with the Subaru Telescope in Hawaii. It’s part of a long-time collaboration between Princeton, the University of Tokyo and the National Astronomical Observatory of Japan, which operates the Subaru Telescope at Mauna Kea, Hawaii. And these first results are generating a lot of interest.

According to Tyler Groff, a team member from Princeton who now works for NASA, the preliminary result from CHARIS have generated a lot of interest from the astronomy community. The CHARIS team is now reviewing research proposals.

“There is a lot of excitement,” Groff said. “Charis is going to open for science in February to everyone.”

CHARIS is designed to capture the light from distant exoplanets, so its field of view is tiny. It’s only 2 arc-seconds, which is a tiny patch of sky. For reference, the full Moon is about 1,800 arc-seconds. But it can take images across a wide band of light wavelengths. The fact that it captures such a wide band of light is what allows such detailed analysis of anything it’s pointed at.

“We tested CHARIS on Neptune, but the entire planet doesn’t even fit on our detector.” -Tyler Groff

CHARIS is located behind a coronagraph. The coronagraph channels light from the Subaru Telescope and divides the light coming directly from a star from the light that is reflecting off planets orbiting that star. The team says it’s like picking out the light reflecting from a speck of tinsel floating in front of a spotlight that’s hundreds of miles away.

November 2, 2016November 2, 2016 by Evan Gough

NASA’s New Asteroid Alert System Gives 5 Whole Days of Warning

An asteroid strike that could wreak some serious havoc against Earth may be statistically unlikely. But it's not like there's no precedent for one. Artist's Image: . Credit: NASA

Everyone knows it was a large asteroid striking Earth that led to the demise of the dinosaurs. But how many near misses were there? Modern humans have been around for about 225,000 years, so we must have come close to death by asteroid more than once in our time. We would have had no clue.

Of course, it’s the actual strikes that are cause for concern, not near misses. Efforts to predict asteroid strikes, and to catalogue asteroids that come close to Earth, have reached new levels. NASA’s newest tool in the fight against asteroids is called Scout. Scout is designed to detect asteroids approaching Earth, and it just passed an important test. Scout was able to give us 5 days notice of an approaching asteroid.

Here’s how Scout works. A telescope in Hawaii, the Panoramic Survey Telescope & Rapid Response System (Pan-STARRS) detected the asteroid, called 2016 UR36, and then alerted other ‘scopes. Three other telescopes confirmed 2016 UR36 and were able to narrow down its trajectory. They also learned its size, about 5 to 25 meters across.

The Pan STARRS telescope in Hawaii. Image: Institute for Astronomy, University of Hawaii.

After several hours, we knew that UR 36 would come close to us, but was not a threat to impact Earth. UR 36 would pass Earth at a distance of about 498,000 km. That’s about 1.3 times further away than the Moon.

The key part of this is that we had 5 days notice. And five days notice is a lot more than the few hours that we usually have. The approach of 2016 UR36 was the first test for the Scout system, and it passed the test.

Asteroids that come close to Earth are called Near Earth Objects (NEOs) and finding them and tracking them has become a growing concern for NASA. In fact NASA has about 15,000 NEOs catalogued, and they’re still finding about 5 more every night.

NASA is getting much better at discovering and detecting NEOs. Image: NASA/NEO Program.

Not only does NASA have the Scout system, whose primary role is to speed up the confirmation process for approaching asteroids, but they also have the Sentry program. Sentry’s role is a little different.

Sentry’s job is to focus on asteroids that are large enough to wipe out a city and cause widespread destruction. That means NEOs that are larger than about 140 metres. Sentry has over 600 large NEOs catalogued, and astronomers think there are a lot more of them out there.

NASA also has the Planetary Defense Coordination Office (PDCO), which has got to be the greatest name for an office ever. (Can you imagine having that on your business card?) Anyway, the PDCO has the over-arching role of preparing for asteroid impacts. The Office is there to make emergency plans to deal with the impact aftermath.

5 days notice for a small asteroid striking Earth is a huge step for preparedness. Resources can be mobilized, critical infrastructure can be protected, maybe things like atomic power plants can be shut down if necessary. And, of course, people can be evacuated.

We haven’t always had any notice for approaching asteroids. Look at the Chelyabinsk meteor from 2013. It was a 10,000 ton meteor that exploded over the Chelyabinsk Oblast, injuring 1500 people and damaging an estimated 3,000 building in 6 cities. If it had been a little bigger, and reached the surface of the Earth, the damage would have been widespread. 5 days notice would likely have saved a lot of lives.

Smaller asteroids may be too small to detect when they’re very far away. But larger ones can be detected when they’re still 10, 20, even 30 years away. That’s enough time to figure out how to stop them. And if you can reach them when they’re that far away, you only need to nudge them a little to deflect them away from Earth, and maybe to the Sun to be destroyed.

Large asteroids with the potential to cause widespread destruction are the attention-getters. Hollywood loves them. But it may be more likely that we face numerous impacts from smaller asteroids, and that they could cause more damage overall. Scout’s ability to detect these smaller asteroids, and give us several days notice of their approach, could be a life-saver.