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Deep Time: Exoplanet Atmospheres in Perspective

by Paul Gilster | Mar 31, 2020 | Exoplanetary Science | 16 Comments

As we improve our instrumentation, the search for worlds where life can flourish will generate more and more Earth-sized targets for extended investigation. Here time plays an interesting role, for our own planet seen two billion years ago would present a different aspect than the Earth of today. Atmospheres evolve, a fact that Lisa Kaltenegger has studied in a series of papers in recent years, working with colleagues at Cornell's Carl Sagan Institute, where she is director. The result is a series of spectral templates applicable to Earth-like planets at various stages of evolution. We have only one known example of a living planet to work with, so Kaltenegger's atmospheric models are designed to match the Earth at different stages of development. The prebiotic Earth of 3.9 billion years ago is saturated with carbon dioxide, while what the paper refers to as Epoch 2, some 3.5 billion years ago, is a world without oxygen. Three more epochs can be defined covering the rise of...

Introducing the Q-Drive: A concept that offers the possibility of interstellar flight

by Paul Gilster | Mar 27, 2020 | Advanced Rocketry | 48 Comments

If Breakthrough Starshot is tackling the question of velocities at a substantial percentage of lightspeed, what do we do about the payload question? A chip-sized spacecraft is challenging in terms of instrumentation and communications, not to mention power. Enter Jeff Greason's Q-Drive, with an entirely different take on high velocity missions within the Solar System and beyond it. Drawing its energies from the medium to deploy an inert propellant, the Q-Drive ups the payload enormously. But can it be engineered? Alex Tolley has been doing a deep dive on the concept and talking to Dr. Greason about the possibilities, out of which today's essay has emerged. A Centauri Dreams regular, Alex has a history of innovative propulsion work, and with Brian McConnell is co-author of A Design for a Reusable Water-Based Spacecraft Known as the Spacecoach (Springer, 2016), by Alex Tolley Technical University of Munich for Project Icarus. Credit: Adrian Mann. The interstellar probe coasted at 4% c...

Voyager 2: Digging Deeper into the Data from Uranus

by Paul Gilster | Mar 26, 2020 | Outer Solar System | 8 Comments

Voyager 2’s flyby of Uranus and its moons occurred on January 24, 1986, returning images that for many of us will always be associated with the outpouring of grief over the loss of Challenger, which occurred a scant four days later. But Voyager’s data were voluminous, its images striking, as we examined the ice giant and its unusual moons up close. The spacecraft closed to 81,500 kilometers of the cloud tops, examining the ring system and discovering 11 new moons. Image: The planet Uranus, in an image taken by the spacecraft Voyager 2 in 1986. The Voyager project is managed for NASA by the Jet Propulsion Laboratory. Credit: NASA/JPL-Caltech. Uranus was already known from early analysis of the Voyager data to have an odd magnetosphere, created where solar wind plasma interacts with the planet’s magnetic field. The planet spins on its side, and its magnetic field axis is tilted 60 degrees away from its spin axis, producing a magnetosphere that wobbles in ways that researchers liken to...

The 1000 AU Target

by Paul Gilster | Mar 24, 2020 | Missions | 32 Comments

One reason I wanted to run yesterday's article about the Opher et al. paper on the heliosphere, aside from its innate scientific interest (and it is a very solid, well crafted piece of work) is to illustrate how much we still have to learn about the balloon-like bubble carved out by the solar wind. The entire Solar System fits within it easily, but we observe only from inside and have little knowledge of its structure. None of the paper's authors would argue that we have the definitive answer on the shape of the heliosphere. That will take a good deal more data, as the paper notes: Future remote-sensing and in situ measurements will be able to test the reality of a rounder heliosphere. In Fig. 6, we show our prediction for the interstellar magnetic field ahead of the heliosphere at V2. In addition, future missions such as the Interstellar Mapping and Acceleration Probe will return ENA [energetic neutral atom] maps at higher energies than present missions and so will be able to...

A New Shape for the Heliosphere

by Paul Gilster | Mar 23, 2020 | Missions | 4 Comments

We have all too little information about the heliosphere, the only data from beyond it being what we have collected from the two Voyagers. Altogether, only five spacecraft -- Pioneer 10 and 11, the Voyagers and New Horizons -- have escaped the gravity of the Sun enroute to interstellar space. To understand how the heliosphere operates, and the interactions between the solar wind of charged particles and magnetic fields with what lies beyond, we’d really like to be able to look back at our system in its entirety. The Interstellar Probe concept being pondered at Johns Hopkins Applied Physics Laboratory and elsewhere is one possible way to do this. I’ll have more to say about Interstellar Probe in coming days, though I do want to give a nod to its history, which can be traced as far back as 1958 and a report from the National Academy of Sciences. APL’s Ralph McNutt has been studying interstellar concepts for decades, and was a major source as I worked on my original Centauri Dreams...

Ryugu’s Clues to the Early Solar System

by Paul Gilster | Mar 20, 2020 | Asteroid and Comet Deflection | 3 Comments

Asteroid 162173 Ryugu, recently explored in depth by the Hayabusa2 spacecraft, is a C-type asteroid, rich in carbon. About a kilometer in diameter, it is evidently composed of highly porous material, and seems to have been formed by the agglomeration of fragments from a larger parent body that was broken apart by impacts. We learn this from a new paper in Nature that examines the object's high porosity and the significantly low mechanical strength of its rock fragments, which affect how it would act if hitting an atmosphere. Matthias Grott, of the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt; DLR) is the principal investigator for MARA, the DLR-built radiometer that flew on board Hayabusa2 and landed aboard the Mobile Asteroid Surface Scout (MASCOT). Says Grott: "The published results are a confirmation of the results from the studies by the DLR radiometer MARA… It has now been shown that the rock analysed by MARA is typical for the entire surface of the...

Extending the Hunt for Trans-Neptunian Objects

by Paul Gilster | Mar 18, 2020 | Outer Solar System | 4 Comments

316 Trans-Neptunian Objects (TNOs) have turned up in a new analysis of data from the Dark Energy Survey, 139 of these being new objects that have not been previously published in the literature. With roughly 3,000 TNOs known, the catalog from this work represents a healthy 10 percent of the total, but more significantly, extends and fine-tunes our methods for tracking such objects. Trans-Neptunian Objects, of which Pluto/Charon represents the best known, orbit beyond Neptune, with Kuiper Belt Objects being a sub-category existing between 30 and 55 AU from the Sun. Here the population is thought to be in the tens of thousands when restricting the definition by size to objects at least 100 kilometers across. But to these Kuiper Belt objects we can add the population of so-called Scattered Disk Objects, which exist in eccentric and inclined orbits, the more extreme of these with semi-major axes between 150 and 250 AU (and then there's Sedna, with aphelion now estimated at more than 900...

An Unusual Look at Mercury

by Paul Gilster | Mar 17, 2020 | Missions | 13 Comments

Centauri Dreams rarely looks at Mercury, the operative method being generally to focus on the outer Solar System and beyond. But a new paper out of the Planetary Science Institute in Tucson (AZ) raises the eyebrows in suggesting that parts of Mercury may once have been able to shelter prebiotic chemistry and perhaps, according to the authors, even primitive life forms. Such a finding might thus extend our ideas of ‘habitable zones’ much closer to parent stars than previously assumed. It seems a long shot, given surface temperatures reaching 430? in the daytime and -180? at night, but the PSI work turns up interesting possibilities in some subsurface regions of Mercury. The heart of this research is found in the datasets returned by the MESSENGER (MErcury Surface Space ENvironment GEochemistry and Ranging) spacecraft. The Mercury orbiter identified numerous volatile-bearing surfaces on Mercury, with high abundances of sulfur, chlorine and potassium, and polar ice in permanently...

Exoplanet Climatology: Surprising Find from ESPRESSO

by Paul Gilster | Mar 16, 2020 | Exoplanetary Science | 10 Comments

Learning about the climate on exoplanets is not something that the designers of ESPRESSO had in mind. Installed at the European Southern Observatory's Very Large Telescope at Paranal (Chile), the Echelle SPectrograph for Rocky Exoplanet and Stable Spectroscopic Observations combines the light of the four VLT telescopes, making it a powerful instrument indeed. We have what is in effect a 16-meter telescope that really ramps up the capability of radial velocity methods. But climate? The case in point is WASP-76b, some 390 light years away in Pisces. So much of the excitement surrounding ESPRESSO has been its ability to drill down to detect small, rocky exoplanets, but this world is somewhere near Jupiter mass, considerably larger in radius, and hellishly close to its star, an F7-class object about 1.5 times as massive as the Sun. The planet orbits the star every 1.8 days at an orbital distance of 0.03 AU and appears to be tidally locked. The result: Temperatures in the area of...

A Rare Brown Dwarf Eclipsing Binary

by Paul Gilster | Mar 11, 2020 | Deep Sky Astronomy & Telescopes | 7 Comments

The SPECULOOS-South Observatory at Cerro Paranal, Chile houses four 1-meter robotic telescopes, now deployed in the service of identifying rocky planets transiting low-mass stars and brown dwarfs. Acronym untanglement: SPECULOOS stands for Search for habitable Planets EClipsing ULtra-cOOl Stars. An early success here is the just reported discovery of a triple brown dwarf system, with an inner binary that is eclipsing and a widely separated brown dwarf companion. The inner binary is what is known as a double-lined system, meaning that spectral lines from both eclipsing stars are visible in the data. Data from the W. M. Keck Observatoy (Maunakea) and the 8-meter Very Large Telescope (VLT), each equipped with sensitive spectrometers, were used to confirm the discovery. Yesterday we saw how the analysis of a young exoplanet, DS Tuc Ab, could offer insights into how 'hot Neptunes' form. In a similar way, the brown dwarf triple system 2M1510A fills a needed gap in our data. A member of a...

Where Do ‘Hot Neptunes’ Come From?

by Paul Gilster | Mar 10, 2020 | Uncategorized | 3 Comments

Learning about the orbital tilt of a distant exoplanet may help us understand how young planets evolve, and especially how they interact with both their star and other nearby planets. Thus the question of ‘hot Neptunes’ and the mechanisms that put them in place.The issue has been under study since 2004. Are we looking at planets laden with frozen ices that have somehow migrated to the inner system, or are these worlds that formed in place, so that their heavy elements are highly refractory materials that can withstand high disk temperatures? Among the exoplanets that can give us guidance here is DS Tuc Ab, discovered in 2019 in data from the TESS mission (Transiting Exoplanet Survey Satellite). Here we have a young world whose host is conveniently part of the 45 million year old Tucana-Horologium moving group (allowing us to establish its age), a planet within a binary system in the constellation Tucana. The binary stars are a G-class and K-class star, with DS Tuc Ab orbiting the...

WFIRST: Ready for Construction

by Paul Gilster | Mar 9, 2020 | Missions | 15 Comments

With the James Webb Space Telescope now declared 'a fully assembled observatory' by NASA, environmental tests loom for the instrument, which is now slated for launch in March of 2021. Within that context, we need to place WFIRST (Wide-Field Infrared Space Telescope), whose development was delayed for several years because of cost overruns on JWST. Recall that WFIRST was the top priority for a flagship mission in the last astrophysics Decadal Survey. The good news is that NASA has just announced that WFIRST has passed what it is calling 'a critical programmatic and technical milestone,' which opens the path to hardware development and testing. With a viewing area 100 times larger than the Hubble instrument, WFIRST will be able to investigate dark energy and dark matter while at the same time examining exoplanets by using microlensing techniques applied to the inner Milky Way. Its exoplanet capabilities could be significantly extended if additional budgeting for a coronagraph -- which...

Cosmic Expansion: A Close Look at a ‘Standard Candle’

by Paul Gilster | Mar 6, 2020 | Deep Sky Astronomy & Telescopes | 38 Comments

Astronomy relies on so-called 'standard candles' to make crucial measurements about distance. Cepheid variables, for example, perhaps the most famous stars in this category, were examined by Henrietta Swan Leavitt in 1908 as part of her study of variable stars in the Magellanic clouds, revealing the relationship between this type of star's period and luminosity. Edwin Hubble would use distance calculations based on this relationship to estimate how far what was then called the 'Andromeda Nebula' was from our galaxy, revealing the true nature of the 'nebula.' In recent times, astronomers have used type Ia supernovae in much the same way, for comparing a source's intrinsic brightness with what is observed in the sky likewise determines distance. The most commonly described type Ia supernovae model occurs in binary systems where one of the stars is a white dwarf, and the assumption among astronomers has been that this category of supernova produces a consistent peak luminosity that can...

Voyager and the Deep Space Network Upgrade

by Paul Gilster | Mar 5, 2020 | Missions | 13 Comments

The fault protection routines programmed into Voyager 1 and 2 were designed to protect the spacecraft in the event of unforeseen circumstances. Such an event occurred in late January, when a rotation maneuver planned to calibrate Voyager 2's onboard magnetic field instrument failed to occur because an unexpected delay in its execution left two systems consuming high levels of power (in Voyager terms) at the same time, overdrawing the available power supply. We looked at this event not long after it happened, and noted that within a couple of days, the Voyager team was able to turn off one of the systems and turn the science instruments back on. Normal operations aboard Voyager 2 were announced on March 3, with five operating science instruments that had been turned off once again returning their data. Such autonomous operation is reassuring because Voyager 2 is now going to lose the ability to receive commands from Earth, owing to upgrades to the Deep Space Network in Australia. This...

Calculating Life’s Possibilities on Titan

by Paul Gilster | Mar 4, 2020 | Outer Solar System | 25 Comments

With surface temperatures around -180° C, Titan presents problems for astrobiology, even if its seasonal rainfall, lakes and seas, and nitrogen-rich atmosphere bear similarities to Earth. Specifically, what kind of cell membrane can form and function in an environment this cold? Five years ago, researchers at Cornell used molecular simulations to screen for the possibilities, suggesting a membrane the scientists called an azotosome, which would be made out of the nitrogen, carbon and hydrogen molecules known to exist in Titan's seas. The azotosome was a useful construct because the phospholipid bilayer membranes giving rise to liposomes on Earth need an analog that can survive Titan's conditions, a methane-based membrane that can form in cryogenic temperatures. And the Cornell work suggested that azotosomes would create a similar flexibility to cell membranes found on Earth. Titan's seas of methane and ethane, then, might offer us the chance for a novel form of life to emerge....

On Freeman Dyson

by Paul Gilster | Mar 2, 2020 | Culture and Society | 12 Comments

Freeman Dyson's response to the perplexity of our existence was not purely scientific. A polymath by nature, he responded deeply to art and literature and often framed life's dilemmas through their lens. Always thinking of himself as a mathematician first, he unified quantum electrodynamics and saw the Nobel Prize go to the three who had formulated, in different ways, its structure, but he would cast himself as the Ben Jonson to Richard Feynman's Shakespeare, a fact noted by Gregory Benford in his review of Phillip F. Schewe's recent biography. That would be a typical allusion for a man whose restless intellect chafed at smug over-specialization, something neither he nor Feynman could ever be accused of. Feynman, Julian Schwinger and Shinichiro Tomonaga each came up with ways to describe how electrons and photons interrelate, but it was Dyson, on one of his long cross-continental bus trips, who worked out the equivalence of their theories, giving us QED. He would publish the unifying...

Charter

In Centauri Dreams, Paul Gilster looks at peer-reviewed research on deep space exploration, with an eye toward interstellar possibilities. For many years this site coordinated its efforts with the Tau Zero Foundation. It now serves as an independent forum for deep space news and ideas. In the logo above, the leftmost star is Alpha Centauri, a triple system closer than any other star, and a primary target for early interstellar probes. To its right is Beta Centauri (not a part of the Alpha Centauri system), with Beta, Gamma, Delta and Epsilon Crucis, stars in the Southern Cross, visible at the far right (image courtesy of Marco Lorenzi).

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