A ring of cyclones swirls around Jupiter's south pole. Credit: NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles
Since it established orbit around Jupiter in July of 2016, the Juno mission has been sending back vital information about the gas giant’s atmosphere, magnetic field and weather patterns. With every passing orbit – known as perijoves, which take place every 53 days – the probe has revealed more interesting things about Jupiter, which scientists will rely on to learn more about its formation and evolution.
During its latest pass, the probe managed to provide the most detailed look to date of the planet’s interior. In so doing, it learned that Jupiter’s powerful magnetic field is askew, with different patterns in it’s northern and southern hemispheres. These findings were shared on Wednesday. Oct. 18th, at the 48th Meeting of the American Astronomical Society’s Division of Planetary Sciencejs in Provo, Utah.
Ever since astronomers began observing Jupiter with powerful telescopes, they have been aware of its swirling, banded appearance. These colorful stripes of orange, brown and white are the result of Jupiter’s atmospheric composition, which is largely made up of hydrogen and helium but also contains ammonia crystals and compounds that change color when exposed to sunlight (aka. chromofores).
Illustration of NASA’s Juno spacecraft firing its main engine to slow down and go into orbit around Jupiter. Credit: NASA/Lockheed Martin
Until now, researchers have been unclear as to whether or not these bands are confined to a shallow layer of the atmosphere or reach deep into the interior of the planet. Answering this question is one of the main goals of the Juno mission, which has been studying Jupiter’s magnetic field to see how it’s interior atmosphere works. Based on the latest results, the Juno team has concluded that hydrogen-rich gas is flowing asymmetrically deep in the planet.
Another interesting find was that Jupiter’s gravity field varies with depth, which indicated that material is flowing as far down as 3,000 km (1,864 mi). Combined with information obtained during previous perijoves, this latest data suggests that Jupiter’s core is small and poorly defined. This flies in the face of previous models of Jupiter, which held that the outer layers are gaseous while the interior ones are made up of metallic hydrogen and a rocky core.
As Tristan Guillot – a planetary scientist at the Observatory of the Côte d’Azur in Nice, France, and a co-author on the study – indicated during the meeting, “This is something that was not expected. We were not sure at all whether we would be able to see that… It’s clear that giant planets have a lot of secrets.”
This artist’s illustration shows Juno’s Microwave Radiometer observing deep into Jupiter’s atmosphere. The image shows real data from the 6 MWR channels, arranged by wavelength. Credit: NASA/SwRI/JPL
But of course, more passes and data are needed in order to pinpoint how strong the flow of gases are at various depths, which could resolve the question of how Jupiter’s interior is structured. In the meantime, the Juno scientists are pouring over the probe’s gravity data hoping to see what else it can teach them. For instance, they also want to know how far the Great Red Spot extends into the amotpshere.
This anticyclonic storm, which was first spotted in the 17th century, is Jupiter’s most famous feature. In addition to being large enough to swallow Earth whole – measuring some 16,000 kilometers (10,000 miles) in diameter – wind speeds can reach up to 120 meters per second (432 km/h; 286 mph) at its edges. Already the JunoCam has snapped some very impressive pictures of this storm, and other data has indicated that the storm could run deep.
In fact, on July 10th, 2017, the Juno probe passed withing 9,000 km (5,600 mi) of the Great Red Spot, which took place during its sixth orbit (perijove six) of Jupiter. With it’s suite of eight scientific instruments directed at the storm, the probe obtained readings that indicated that the Great Red Spot could also extend hundreds of kilometers into the interior, or possibly even deeper.
As David Stevenson, a planetary scientist at the California Institute of Technology and a co-author on the study, said during the meeting, “It’s not yet clear that it is so deep it will show up in gravity data. But we’re trying”.
Jupiter’s Great Red Spot, as imaged by the Juno spacecraft’s JunoCam at a distance of just 9,000 km (5,600 mi) from the atmosphere. Credit : NASA/SwRI/MSSS/TSmith
Other big surprises which Juno has revealed since it entered orbit around Jupiter include the clusters of cyclones located at each pole. These were visible to the probe’s instruments in both the visible and infrared wavelengths as it made its first maneuver around the planet, passing from pole to pole. Since Juno is the first space probe in history to orbit the planet this way, these storms were previously unknown to scientists.
In total, Juno spotted eight cyclonic storms around the north pole and five around the south pole. Scientists were especially surprised to see these, since computer modelling suggests that such small storms would not be stable around the poles due to the planet’s swirling polar winds. The answer to this, as indicated during the presentation, may have to do with a concept known as vortex crystals.
As Fachreddin Tabataba-Vakili – a planetary scientist at NASA’s Jet Propulsion Laboratory and a co-author on the study – explained, such crystals are created when small vortices form and persist as the material in which they are embedded continues to flow. This phenomenon has been seen on Earth in the form of rotating superfluids, and Jupiter’s swirling poles may possess similar dynamics.
In the short time that Juno has been operating around Jupiter, it has revealed much about the planet’s atmosphere, interior, magnetic field and internal dynamics. Long after the mission is complete – which will take place in February of 2018 when the probe is crashed into Jupiter’s atmosphere – scientists are likely to be sifting through all the data it obtained, hoping to solve any remaining mysteries from the Solar System’s largest and most massive planet.
This is the first optical image ever to show an event initially detected as a Gravitational Wave (GW), designated GW170817, shown left. Afterglow, designated as SSS17a, is left over from the explosion of two neutron stars that collided in galaxy NGC 4993 (shown centre). Only 10.9 hours after triggering the largest astronomical search in history, GW170817’s afterglow was discovered by the Swope 1-m telescope at the Las Campanas Observatory, in Chile. Four days later, image on right shows afterglow dimming in brightness and changing from blue to red. CREDIT: Las Campanas Observatory, Carnegie Institution of Washington (Swope + Magellan)
“This is quite literally a physics gold mine!” said Masao Sako, with the University of Pennsylvania.
Four days before the Great American Solar Eclipse on August 21, a newly discovered gravitational wave caused more astronomers (8,223+), using more telescopes (70), to publish more papers (100 — see the list below) in less time than for any other astronomical event in history. The sixth gravitational wave (GW) to be discovered by the Laser Interferometer Gravitational-wave Observatory (LIGO) and Virgo GW observatories, which occurred on August 17, 2017 at 12:41:04 UTC, was surprising in two ways already reported.
GW event six, designated GW170817, did not result from the collision and subsequent explosion of two black holes. All previous GW events, including the first ever discovered in 2015, had involved the collision of black holes with typically 40 times the mass of the Sun between them. Here however, the GW was evidently triggered by the collision and explosion of two neutron stars, having only 3 times the Sun’s mass in total.
Afterglow of GW170817 is shown in close-ups captured by the NASA Hubble Space Telescope, showing it dimming in brightness over days and weeks. CREDIT: NASA and ESA: A. Levan (U. Warwick), N. Tanvir (U. Leicester), and A. Fruchter and O. Fox (STScI)
Crucially, GW170817 occurred ten times closer to Earth than all earlier GW events. Earlier GWs involved black hole collisions at more than 1.3 billion light-years (400 million parsecs or Mpc). GW170817, in comparison, was known within hours of its discovery to lie within only 130 million light-years (40 Mpc). That vastly improved astronomer’s odds of detecting the event independently, because in cosmological terms, it occurred within less than 1% of the universe’s Hubble length of 14 billion light-years (4,300 Mpc).
Not widely reported is that our current astronomical theory regarding GW170817 still depends significantly on observations yet to be made. In brief, astronomers currently believe that GW170817 was triggered by the merger of two neutron stars, which triggered the explosion of a Short Gamma-Ray Burst (SGRB), which emitted only a fraction of the gamma-ray energy in our direction normally associated with SGRBs, because it was the first SGRB observed at such a large angle away from the direction of its focused jets of gamma-rays. The SGRB associated with GW170817 emitted its jet at roughly 30 degrees away from our line-of-sight. All other SGRBs have been observed at only a few degrees from alignment with their jets. The exact angle of the newly discovered SGRB’s jet is important in understanding how its afterglow compares with other SGRB afterglows. Significant properties reported for the GW, including its distance, depend on the angle at which the two neutron stars collided relative to Earth.
The collision angle determined roughly based on the GW itself is probably OK. Only radio maps of the SGRB region at 100 days however, will provide astronomers with the most precise measurements of the resulting explosion’s velocities and directions over time to date. Only then will astronomers learn more about the exact angle of the SGRB’s jet, providing potentially a more accurate estimate of the angle at which the neutron stars collided. More surprises could be in store as a result, including refinements of the properties reported.
ANIMATION (you may have to click image for animation in some browsers): This time-lapse image of the afterglow of GW170817 shows it continuing to increase in radio wavelength brightness over the first month, and was provided by the National Radio Astronomy Observatory Very Large Array radio telescope. CREDIT: NRAO/VLA
Unlike previous events, GW170817 was close enough that within 1.74 seconds of its initial detection by LIGO, it’s gamma radiation was detected by the Fermi Gamma-Ray space telescope. The INTEGRAL Gamma-Ray space observatory detected it too, and it was later designated SGRB 170817A. As an SGRB alone, the event would have triggered alerts to observatories worldwide and aloft, each aiming to detect the explosion’s faint optical afterglow. SGRB optical afterglows have been used to pinpoint the exact positions of SGRBs, not only on the sky, but also in terms of their distance from Earth.
Astronomers in this case had the first GW ever to coincide with, and be independently corroborated by, any observable counterpart, and alerts became a call to astronomical arms. Even though its exact position on the sky was uncertain by many degrees, GW170817 was so close that astronomers were able to quickly narrow down its exact location.
“With a previously-compiled list of nearby galaxies having positions and distances culled from the massive on-line archive of the NASA/IPAC Extragalactic Database (NED), our team rapidly zeroed in on the host galaxy of the event,” said Barry Madore, of Carnegie Observatories.
Precisely because GW170817 occurred at only 130 million light-years, the number of candidate galaxies to observe was only several dozen. In contrast, for previous GW discoveries occurring at billions of light-years, thousands of galaxies would have to be observed. Within 11 hours of the explosion, its afterglow was discovered in the lenticular galaxy NGC 4993, by the Swope 1-m telescope in Chile. They obtained the first-ever visual image of an event associated with a GW.
“Where observation is concerned, chance favors only the prepared mind,” added Madore, quoting Louis Pasteur from 150 years ago. Madore is also a researcher with the Swope team and a co-author on six papers reporting Swope’s discovery of the afterglow and some of its implications. “When alerts were sent out to the LIGO/VIRGO gravity wave detection consortium on the night of August 17, 2017, our team of astronomers was indeed prepared.”
New images of the afterglow of GW170817, aka SGRB 170817A, initially designated as Swope Supernova Survey SSS17a, revealed a bright blue astronomical transient, later designated as AT2017gfo by the International Astronomical Union (IAU).
“There will be more such events, no doubt; but this image taken at the Henrietta Swope 1m telescope at the Las Campanas Observatory in Chile was the first in history, and it truly ushered in the Era of Multi-Messenger Astronomy,” said Madore.
Radio observatories joined the hunt, including the Karl G. Jansky Very Large Array (VLA), the Australia Telescope Compact Array (ATCA) and the Giant Metrewave Radio Telescope (GMRT). So did the Swift ultraviolet and Chandra X-ray space observatory satellites. By day one after the explosion, all frequencies of the electromagnetic spectrum were being observed in the direction of NGC 4993. On multiple wavelengths, multiple “messengers” of GW170817’s existence began to reveal more than the sum of their parts.
Change in brightness of GW170817’s afterglow over time since explosion (merger), is shown in these light-curves. Brightness in 14 different optical wavelengths is shown, including invisible ultraviolet, and visible blue, green, and yellow, and invisible infrared wavelengths in orange and red. Afterglow fades quickly in all wavelengths, except infrared. In infrared, afterglow continues to brighten until ~3 days after explosion, before beginning to fade. CREDIT: Las Campanas Observatory, Carnegie Institution of Washington (Swope + Magellan)
AT2017gfo brightened over the next few days after explosion, in near infrared observations continued by Swope. Their light-curves show the changes in the afterglow’s brightness over time. At three days post explosion, the near-infrared afterglow stops brightening and begins to fade. As with other SGRB afterglows, AT2017gfo faded completely from visual observation over the course of days to weeks, but observations in X-rays and radio continue. Radio observations at 100 days post explosion, which will not occur until November 25, are crucial as said. Although a month away, planned radio observations will determine more than just the long-term evolution of the afterglow over 3 months. Indeed, our astronomical theory accounting for the event’s first three weeks, as already observed, analyzed, and reported, still depends to a surprising degree on an exact number of degrees. The number of degrees relative to Earth for this SGRB based on radio data however, will not be known for at least a month.
“With GW170817 we have for the first time truly independent verification of a gravitational wave source,” said Robert Quimby, of the Kavli Institute for the Physics and Mathematics of the Universe at the University of Tokyo, and coauthor of a paper regarding the event’s implications. “The electromagnetic signature of this event can be uniquely matched to the predictions of binary neutron star mergers, and it is actually quite amazing how well the theory matches the data considering how few observational constraints were available to guide the model.”
“With GW170817, we can learn about nuclear physics, relativity, stellar evolution, and cosmology all in one shot,” added Sako, who is also a co-author on ten papers regarding the event. “Plus we now know how all of the heaviest elements in the Universe are created.”
Afterglow faded from optical observations over days to weeks. Here, however, as observed at radio frequencies by the Very Large Array radio telescope, the electromagnetic counterpart to GW170817 is seen brightening over the first month since explosion. CREDIT: Courtesy of Gregg Hallinan, California Institute of Technology, and the National Radio Astronomy Observatory Very Large Array radio telescope
EVENT CHRONOLOGY
T = 0 sec.: GW170817 detected by LIGO/VIRGO [1, 82]
T = 1.74 sec.: SGRB 170817A detected by Fermi Gamma-Ray Burst Monitor satellite immediately after GW170817 [52]
T = 28 min.: Gamma-ray Coordinates Network (GCN) Notice [53]
T = 40 min.: GCN Circular [53]
T = 5.63 hr.: First sky map locating GW170817 to within several degrees [53]
T = 10.9 hr.: Swope 1-m observatory discovers explosion’s afterglow, AT 2017gfo, in galaxy NGC 4993 [18, 24, 64, 75, 77]
T = 11.09 hr.: PROMPT 0.4m observatory detects AT 2017gfo [88]
T = 11.3 hr.: Hubble Space Telescope images AT 2017gfo [20]
T = 12-24 hr.: Magellan; Las Campanas Observatory; W. M. Keck Observatory; Blanco 4-m Cerro Tololo Inter-American Observatory; Gemini South; European Southern Observatory VISTA; Subaru among 6 Japanese telescopes; Pan-STARRS1; Very Large Telescope; 14 Australian telescopes; and Antarctic Survey Telescope optical observatories, and VLA, VLITE, ATCA, GMRT, and ALMA radio observatories, as well as Swift and NuSTAR ultraviolet satellite observatories
PROPERTIES
Position: Right Ascension 13h09m48.085s ± 0.018s; Declination -23d22m53.343s ± 0.218s (J2000 equinox); 10.6s or 7,000 light-years (2.0 kiloparsecs or kpc) from the nucleus of lenticular galaxy NGC 4993 [18]
Distance: 140 ± 40 million light-years (41 ± 13 Mpc), with 30% scatter based on 3 GW-based estimates [1, 25, 82], and 131 ± 9 million light-years (39.3 ± 2.7 Mpc), with 7% scatter based on 3 distance indicators, including GW-based as well as new Fundamental Plane relation-based distances for NGC 4993 [41, 43], and Tully-Fisher relation-based distances for galaxies in the group of galaxies including NGC 4993 from the NASA/IPAC Extragalactic Database (NED)
Mass: Neutron stars total 2.82 +0.47 -0.09 Sun’s mass [82]; mass ejected in elements heavier than iron is 0.03 ± 0.01 Sun’s mass or 10,000 Earth masses, based on 4 estimates [24, 59, 82, 93], including gold amounting to 150 ± 50 Earth masses [60]
Luminosity: Peaks at 0.5 days after explosion, at ~1042 erg/s, equivalent to 260 million Suns [24]
SGRB jet angle: 31 ± 3 degrees away from line-of-sight to Earth, based on 9 estimates [2, 25, 34, 35, 36, 44, 58, 62, 82]
SGRB jet speed: 30% speed of light, based on 4 estimates [20, 42, 59, 75]
Names: GW170817, SGRB 170817A, AT 2017gfo = IAU designation for SGRB afterglow, aka SSS17a, DLT17ck, J-GEM17btc, and MASTER OTJ130948.10-232253.3
IMPLICATIONS
Astronomy (1): Confirms binary neutron star collisions as a source for GW and SGRB events [1, 82]
Astronomy (2): GWs provide a new way of measuring neutron star diameters [8]
Astronomy (3): Gives universal expansion rate, or Hubble constant, as H0 = 71 ± 10 km -1 Mpc-1, with 14% accuracy, based on 6 GW-based estimates for GW170817 ranging from 69 to 74 km -1 Mpc-1, bridging current estimates [1, 22, 36, 60, 74, 82]; accuracy will improve to 4% with future similar events [74]
General Relativity (1): Confirms GW velocity equals speed of light to within 1 part per 1,000,000,000,000,000 or 1/1015 [7, 21, 70, 91]
General Relativity (2): Confirms equivalence of gravitational energy and inertial energy, or Weak Equivalence Principle, to within 1 part per 1,000,000,000 or 1/109 [7, 11, 91, 92]
Physics: Confirms binary neutron star collisions are significant production sites for elements heavier than iron, including gold, platinum, and uranium [17, 69]
Life on Earth: Indicates a higher deadly rate of gamma-rays for extraterrestrial life [15]
GW170817 (1): Predicted one binary neutron star collision per year similar to GW170817 within a distance from Earth of 130 million light-years [40 Mpc] [24]
GW170817 (2): Predicted to produce a 10 Giga-Hertz afterglow that peaks at ~100 days with a radio magnitude of ~10 milli-Janskys [24]
GW170817 (3): Predicted to remain visible in radio for 5-10 years, and for decades with next-generation radio observatories [2]
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Artist's concept of the Project Blue space telescope, which the organization hopes to use to spot exoplanets in Alpha Centauri beginning in 2020. Credit: projectblue.org
In the past few decades, thousands of exoplanets have been discovered in neighboring star systems. In fact, as of October 1st, 2017, some 3,671 exoplanets have been confirmed in 2,751 systems, with 616 systems having more than one planet. Unfortunately, the vast majority of these have been detected using indirect means, ranging from Gravitational Microlensing to Transit Photometry and the Radial Velocity Method.
What’s more, we have been unable to study these planets up close because the necessary instruments do not yet exist. Project Blue, a consortium of scientists, universities and institutions, is looking to change that. Recently, they launched a crowdfunding campaign through Indiegogo to finance the development of a space telescope that will start looking for exoplanets in the Alpha Centauri system by 2021.
Artist’s impression of a planet orbiting the star Alpha Centauri B, a member of the triple star system that is the closest to Earth. Credit: ESO
To accomplish their goal of directly studying exoplanets, Project Blue is seeking to leverage recent changes in space exploration, which include improved instruments and methodology, the rate at which exoplanet have been discovered in recent years, and increased collaboration between the private and public sector. As SETI Institute President and CEO Bill Diamond explained in a recent SETI press statement:
“Project Blue builds on recent research in seeking to show that Earth is not alone in the cosmos as a planet capable of supporting life, and wouldn’t it be amazing to see such a planet in our nearest neighboring star system? This is the fundamental reason we search.”
As noted, virtually all exoplanet discoveries that have been made in the past few decades were done using indirect methods – the most popular of which is Transit Photometery. This method is what the Kepler and K2 missions relied on to detect a total of 5,017 exoplanet candidates and confirm the existence of 2,470 exoplanets (30 of which were found to orbit within their star’s habitable zone).
This method consists of astronomers monitoring distant stars for periodic dips in brightness, which are caused by a planet transiting in front of the star. By measuring these dips, scientists are able to determine the size of planets in that system. Another popular technique is the Radial Velocity (or Doppler) Method, which measures changes in a star’s position relative to the observer to determine how massive its system of planets are.
Project Blue’s mission concept, showing the telescope, its launch and deployment. Credit: projectblue.org
These and other methods (alone or in combination) have allowed for the many discoveries that have been made to take place. But so far, no exoplanets have been directly imaged, which is due to the cancelling effect stars have on optical instruments. Basically, astronomers have been unable to spot the light being reflected off of an exoplanet’s atmosphere because the light coming from the star is up to ten billion times brighter.
The challenge has thus become how to go about blocking this light so that the planets themselves can become visible. One proposed solution to this problem is NASA’s Starshade concept, a giant space structure that would be deployed into orbit alongside a space telescope (most likely, the James Webb Space Telescope). Once in orbit, this structure would deploy its flower-shaped foils to block the glare of distant stars, thus allowing the JWST and other instruments to image exoplanets directly.
But since Alpha Centauri is a binary system (or trinary, if you count Proxima Centauri), being able to directly image any planets around them is even more complicated. To address this, Project Blue has developed plans for a telescope that will be able to suppress light from both Alpha Centauri A and B, while simultaneously taking images of any planets that orbit them. It’s specialized starlight suppression system consists of three components.
First, there is the coronagraph, an instrument which will rely on multiple techniques to block starlight. Second, there’s the deformable mirror, low-order wavefront sensors, and software control algorithms that will manipulate incoming light. Last, there is the post-processing method known as Orbital Differntial Imaging (ODI), which will allow the Project Blue scientist to enhance the contrast of the images taken.
Project Blue’s mission timeline, which woudl commence at the end of the decade and run for six years. Credit: projectblue.org
Given its proximity to Earth, the Alpha Centauri system is the natural choice for conducting such a project. Back in 2012, an exoplanet candidate – Alpha Centauri Bb – was announced. However, in 2015, further analysis indicated that the signal detected was an artefact in the data. In March of 2015, a second possible exoplanet (Alpha Centauri Bc) was announced, but its existence has also come to be questioned.
With an instrument capable of directly imaging this system, the existence of any exoplanets could finally be confirmed (or ruled out). As Franck Marchis – the Senior Planetary Astronomer at the SETI Institute and Project Blue Science Operation Lead – said of the Project:
“Project Blue is an ambitious space mission, designed to answer to a fundamental question, but surprisingly the technology to collect an image of a “Pale Blue Dot” around Alpha Centauri stars is there. The technology that we will use to reach to detect a planet 1 to 10 billion times fainter than its star has been tested extensively in lab, and we are now ready to design a space-telescope with this instrument.”
If Project Blue meets its crowdfunding goals, the organization intends to deploy the telescope into Near-Earth Orbit (NEO) by 2021. The telescope will then spend the next two years observing the Alpha Centauri system with its corongraphic camera. All told, between the development of the instrument and the end of its observation campaign, the mission will last six years, a relatively short run for an astronomical mission.
Project Starshot, an initiative sponsored by the Breakthrough Foundation, is intended to be humanity’s first interstellar voyage. Credit: breakthroughinitiatives.org
However, the potential payoff for this mission would be incredibly profound. By directly imaging another planet in the closest star system to our own, Project Blue could gather vital data that would indicate if any planets there are habitable. For years, astronomers have attempted to learn more about the potential habitability of exoplanets by examining the spectral data produced by light passing through their atmospheres.
However, this process has been limited to massive gas giants that orbit close to their parent stars (i.e. “Super-Jupiters”). While various models have been proposed to place constraints on the atmospheres of rocky planets that orbit within a star’s habitable zone, none have been studied directly. Therefore, if it should prove to be successful, Project Blue would allow for some of the greatest scientific finds in history.
What’s more, it would provide information that could a long way towards informing a future mission to Alpha Centauri, such as Breakthrough Starshot. This proposed mission calls for the use of a large laser array to propel a lightsail-driven nanocraft up to relativistic speeds (20% the speed of light). At this rate, the craft would reach Alpha Centauri within 20 years time and be able to transmit data back using a series of tiny cameras, sensors and antennae.
As the name would suggest, Project Blue hopes to capture the first images of a “Pale Blue Dot” that orbits another star. This is a reference to the photograph of Earth that was taken by the Voyager 1 probe on February 19th, 1990, after the probe concluded its primary mission and was getting ready to leave the Solar System. The photos were taken at the request of famed astronomer and science communicator Carl Sagan.
The “Pale Blue Dot” photograph taken by the Voyager 1 probe. Credit: NASA/JPL
When looking at the photographs, Sagan famously said: “Look again at that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives.” Thereafter, the name “Pale Blue Dot” came to be synonymous with Earth and capture the sense of awe and wonder that the Voyage 1 photographs evoked.
More recently, other “Pale Blue Dot” photographs have been snapped by missions like the Cassini orbiter. While photographing Saturn and its system of rings in the summer of 2013, Cassini managed to capture images that showed Earth in the background. Given the distance, Earth once again appeared as a small point of light against the darkness of space.
Beyond relying on crowdfunding and the participation of multiple non-profit organizations, this low-cost mission also seeks to capitalize on a growing trend in space exploration, – which is open participation and collaborations between scientific institutions and citizen scientists. This is one of the primary purposes behind Project Blue, which is to engage the public and educate them about the importance of space exploration.
As Jon Morse, the CEO of the BoldlyGo Institute, explained:
“The future of space exploration holds boundless potential for answering profound questions about our existence and destiny. Space-based science is a cornerstone for investigating such questions. Project Blue seeks to engage a global community in a mission to search for habitable planets and life beyond Earth.”
As of the penning of this article, Project Blue has managed to raise $125,561 USD of their goal of $175,000. For those interesting in backing this project, Project Blue’s Indiegogo campaign will remain open for another 11 days. And be sure to check out their promotional video as well:
Astronomers from the Minor Planet Center sent out an announcement today, hoping for astronomers to do followup observations on the comet C/2017 U1 PANSTARRS. That’s because this strange comet seems to be on a trajectory that originated outside our Solar System. Not just from the Oort Cloud, but from another star.
Is this the first insterstellar comet ever found? Orbital path of C 2017/U1 PANSTARRS
Comets are broken up into two broad categories. There are the short-period comets, the ones that started out in the Kuiper Belt and follow a regular, predictable orbit that brings them close to the Sun on a regular basis. Halley’s Comet is a great example, brightening in the skies every 7 decades or so.
The long-period comets started in the Oort Cloud, a vast collection of comets extending hundreds of astronomical units from the Sun – even out to a light-year away. These comets can take hundreds of thousands or even millions of years to make the long journey down to the inner Solar System, jostled out of their holding pattern by the interaction with a nearby star.
Astronomers make several observations of a comet’s path through the Solar System and then use this to calculate its orbital eccentricity. Zero eccentricity would orbiting the Sun in a circle, while an eccentricity of 1 would be a parabolic trajectory. Halley’s Comet, for example, has an eccentricity of 0.967; somewhere between a circle and a parabola.
From the initial observations, C/2017 U1 has an eccentricity of 1.2, which makes it a hyperbolic trajectory. This means it’s on a trajectory that came from outside the Solar System itself.
Further observations of this object are very much desired. Unless there are serious problems with much of the astrometry listed below, strongly hyperbolic orbits are the only viable solutions. Although it is probably not too sensible to compute meaningful original and future barycentric orbits, given the very short arc of observations, the orbit below has e ~ 1.2 for both values. If further observations confirm the unusual nature of this orbit, this object may be the first clear case of an interstellar comet.
In a tweet, astronomer Tony Dunn included a simulation he’d made showing the trajectory of C/2017 U1 compared to other comets discovered this year.
Is comet #C2017U1 a visitor from another solar system? Here's a simulation of its current nominal orbit. This simulation will run in your browser. https://t.co/M1O5an87qk Watch how fast it moves compared to a few other 2017 comet discoveries. pic.twitter.com/cq7U5eYKOu
How could a comet like this have gotten to the Solar System? When other stars pass within a few light-years of the Sun, they stir up our Oort Cloud with their gravity. Presumably the Sun does the same to other stars system cometary clouds. Three-body interactions between the comet, planets and the star could kick a comet out into an escape orbit from its star system. Actually, astronomers are arguing about the possible source in the Minor Planet Mailing List group.
Again, Tony Dunn simulated its current trajectory, showing how the comet would have been flying towards us from the Constellation Lyrae, which contains the bright star Vega. Did it come from Vega? We’ll probably never know.
Did it come from Vega?
Here are 2 more simulations of #C2017U1. They will run in your browser.
C/2017 U1 was first discovered on October 18, 2017 from the Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) located at the Haleakala Observatory in Hawaii. The purpose of this automated telescope is to scan the sky night after night, searching for moving and variable objects. It’s one of the most prolific comet hunters in the world, which is why you probably see so many comets named after it.
The comet was about 30 million kilometers (19 million miles) from Earth, and only 6 days of observations have been made. It was traveling at a velocity of 26 km/s, much faster than the escape velocity of the Solar System.
We now know that it passed its closest point to the Sun on September 9, 2017, and is well on its way back out of the Solar System.
Will this turn out to be the first interstellar comet? It’s already as dim as magnitude 21, so astronomers will need to work quickly to gather more observations before it fades from sight entirely.
Artist's impression of a hypothetical Earth-like moon around a Saturn-like exoplanet. Credit: Wikipedia Commons/
Frizaven
Finding planets beyond our Solar System is already tough, laborious work. But when it comes to confirmed exoplanets, an even more challenging task is determining whether or not these worlds have their own satellites – aka. “exomoons”. Nevertheless, much like the study of exoplanets themselves, the study of exomoons presents some incredible opportunities to learn more about our Universe.
Of all possible candidates, the most recent (and arguably, most likely) one was announced back in July 2017. This moon, known as Kepler-1625 b-i, orbits a gas giant roughly 4,000 light years from Earth. But according to a new study, this exomoon may actually be a Neptune-sized gas giant itself. If true, this will constitute the first instance where a gas giant has been found orbiting another gas giant.
An artist’s conception of a habitable exomoon orbiting a gas giant. Credit: NASA
Within the Solar System, moons tell us much about their host planet’s formation and evolution. In the same way, the study of exomoons is likely to provide insight into extra-solar planetary systems. As Dr. Heller explained to Universe Today via email, these studies could also shed light on whether or not these systems have habitable planets:
“Moons have proven to be extremely helpful to study the formation and evolution of the planets in the solar system. The Earth’s Moon, for example, was key to set the initial astrophysical conditions, such as the total mass of the Earth and the Earth’s primordial spin state, for what has become our habitable environment. As another example, the Galilean moons around Jupiter have been used to study the conditions of the primordial accretion disk around Jupiter from which the planet pulled its mass 4.5 billion years ago. This accretion disk has long gone, but the moons that formed within the disk are still there. And so we can use the moons, in particular their contemporary composition and water contents, to study planet formation in the far past.”
When it comes to the Kepler-1625 star system, previous studies were able to produce estimates of the radii of both Kepler-1625 b and its possible moon, based on three observed transits it made in front of its star. The light curves produced by these three observed transits are what led to the theory that Kepler-1625 had a Neptune-size exomoon orbiting it, and at a distance of about 20 times the planet’s radius.
But as Dr. Heller indicated in his study, radial velocity measurements of the host star (Kepler-1625) were not considered, which would have produced mass estimates for both bodies. To address this, Dr. Heller considered various mass regimes in addition to the planet and moon’s apparent sizes based on their observed signatures. Beyond that, he also attempted to place the planet and moon into the context of moon formation in the Solar System.
Artist’s impression of an exomoon orbiting a gas giant (left) and a Neptune-sized exoplanet (right). Credit: NASA/JPL-Caltech
The first step, accroding to Dr. Heller, was to conduct estimates of the possible mass of the exomoon candidate and its host planet based on the properties that were shown in the transit lightcurves observed by Kepler.
“A dynamical interpretation of the data suggests that the host planet is a roughly Jupiter-sized (“size” in terms of radius) brown dwarf with a mass of almost 18 Jupiter masses,” he said. “The uncertainties, however, are very large mostly due to the noisiness of the Kepler data and due to the low number of transits (three). In fact, the host object could be a Jupiter-like planet or even be a moderate-sized brown dwarf of up to 37 Jupiter masses. The mass of the moon candidate ranges somewhere between a super-Earth of a few Earth masses and Neptune’s mass.”
Next, Dr. Heller compared the relative mass of the exomoon candidate and Kepler-1625 b and compared this value to various planets and moons of the Solar System. This step was necessary because the moons of the Solar System show two distinct populations, based the mass of the planets compared to their moon-to-planet mass ratios. These comparisons indicate that a moon’s mass is closely related to how it formed.
For instance, moons that formed through impacts – such as Earth’s Moon, and Pluto’s moon Charon – are relatively heavy, whereas moons that formed from a planet’s accretion disk are relatively light. While Jupiter’s moon Ganymede is the most massive moon in the Solar System, it is rather diminutive and tiny compared to Jupiter itself – the largest and most massive body in the Solar System.
Artist’s impression of the view from a hypothetical moon around a exoplanet orbiting a triple star system. Credit: NASA
In the end, the results Dr. Heller obtained proved to be rather interesting. Basically, they indicated that Kepler-1625 b-i cannot be definitively placed in either of these families (heavy, impact moons vs. lighter, accretion moons). As Dr. Heller explained:
“[T]]he most reasonable scenarios suggest that the moon candidate is more of the heavy kind, which suggests it should have formed through an impact. However, this exomoon, if real, is most likely gaseous. The solar system moons are all rocky/icy bodies without a significant gas envelope (Titan has a thick atmosphere but its mass is negligible). So how would a gas giant moon have formed through an impact? I don’t know. I don’t know if anybody knows.
“Alternatively, in a third scenario, Kepler-1625 b-i could have formed through capture, but this implies a very unlikely progenitor planetary binary system, from which it was pulled into a bound orbit around Kepler-1625 b, while its former planetary companion was ejected from the system.”
What was equally interesting were the mass estimates for Keple-1625 b, which Dr. Heller averaged to be 19 Jupiter masses, but could be as high as 112 Jupiter Masses. This means that the host planet could be anything from a gas giant that is just slightly larger than Saturn to a Brown Dwarf or even a Very-Low-Mass-Star (VLMS). So rather than a gas giant moon orbiting a gas giant, we could be dealing with a gas giant moon orbiting a small star, which together orbit a larger star!
An artist’s conception of a T-type brown dwarf. Credit: Tyrogthekreeper/Wikimedia Commons.
It’s the stuff science fiction is made of! And while this study cannot provide exact mass constraints on Keplder-1625 b and its possible moon, its significance cannot be denied. Beyond providing astrophysicists with the first possible example of a gas giant moon, this study is of immense significance as far as the study of exoplanet systems is concerned. If and when Kepler-1625 b-i is confirmed, it will tell us much about the conditions under which its host formed.
In the meantime, more observations are needed to confirm or rule out the existence of this moon. Fortunately, these observations will be taking place in the very near future. When Kepler-1625 b makes it next transit – on October 29th, 2017 – the Hubble Space Telescope will be watching! Based on the light curves it observes coming from the star, scientist should be able to get a better idea of whether or not this mysterious moon is real and what it looks like.
“If the moon turns out to be a ghost in the data, then most of this study would not be applicable to the Kepler-1625 system,” said Dr. Heller. “The paper would nevertheless present an example study of how to classify future exomoons and how to put them into the context of the solar system. Alternatively, if Kepler-1625 b-i turns out to be a genuine exomoon, then my study suggests that we have found a new kind of moon that has a very different formation history than the moons we know as of today. Certainly an exquisite riddle for astrophysicists to solve.”
The study of exoplanet systems is like pealing an onion, albeit in a dark room with the lights turned off. With every successive layer scientists peel back, the more mysteries they find. And with the deployment of next-generation telescopes in the near future, we are bound to learn a great deal more!
Artist's depiction of a waterworld. A new study suggests that Earth is in a minority when it comes to planets, and that most habitable planets may be greater than 90% ocean. Credit: David A. Aguilar (CfA)
When hunting for potentially habitable exoplanets, one of the most important things astronomers look for is whether or not exoplanet candidates orbit within their star’s habitable zone. This is necessary for liquid water to exist on a planet’s surface, which in turn is a prerequisite for life as we know it. However, in the course of discovering new exoplanets, scientists have become aware of an extreme case known as “water worlds“.
Water worlds are essentially planets that are up to 50% water in mass, resulting in surface oceans that could be hundreds of kilometers deep. According to a new study by a team of astrophysicists from Princeton, the University of Michigan and Harvard, water worlds may not be able to hang on to their water for very long. These findings could be of immense significance when it comes to the hunt for habitable planets in our neck of the cosmos.
This most recent study, titled “The Dehydration of Water Worlds via Atmospheric Losses“, recently appeared in The Astrophysical Journal Letters. Led by Chuanfei Dong from the Department of Astrophysical Sciences at Princeton University, the team conducted computer simulations that took into account what kind of conditions water worlds would be subject to.
Artist’s impression of the planet orbiting a red dwarf star. Credit: ESO/M. Kornmesser
This study was motivated largely by the number of exoplanet discoveries have been made around low-mass, M-type (red dwarf) star systems in recent years. These planets have been found to be comparable in size to Earth – which indicated that they were likely terrestrial (i.e. rocky). In addition, many of these planets – such as Proxima b and three planets within the TRAPPIST-1 system – were found to be orbiting within the stars habitable zones.
However, subsequent studies indicated that Proxima b and other rocky planets orbiting red dwarf stars could in fact be water worlds. This was based on mass estimates obtained by astronomical surveys, and the built-in assumptions that such planets were rocky in nature and did not have massive atmospheres. At the same time, numerous studies have been produced that have cast doubt on whether or not these planets would be able to hold onto their water.
Basically, it all comes down to the type of star and the orbital parameters of the planets. While long-lived, red dwarf stars are known for being variable and unstable compared to our Sun, which results in periodic flares up that would strip a planet’s atmosphere over time. On top of that, planets orbiting within a red dwarf’s habitable zone would likely be tidally-locked, meaning one side of the planet would be constantly exposed to the star’s radiation.
Because of this, scientists are focused on determining just how well exoplanets in different types of star systems could hold onto their atmospheres. As Dr. Dong told Universe Today via email:
“It is fair to say that the presence of an atmosphere is perceived as one of the requirements for the habitability of a planet. Having said that, the concept of habitability is a complex one with myriad factors involved. Thus, an atmosphere by itself will not suffice to guarantee habitability, but it can be regarded as an important ingredient for a planet to be habitable.”
Illustration showing the possible surface of TRAPPIST-1f, one of the newly discovered planets in the TRAPPIST-1 system. Credits: NASA/JPL-Caltech
To test whether or not a water world would be able to hold onto its atmosphere, the team conducted computer simulations that took into account a variety of possible scenarios. These included the effects of stellar magnetic fields, coronal mass ejections, and atmospheric ionization and ejection for various types of stars – including G-type stars (like our Sun) and M-type stars (like Proxima Centauri and TRAPPIST-1).
With these effects accounted for, Dr. Dong and his colleagues derived a comprehensive model that simulated how long exoplanet atmospheres would last. As he explained it:
“We developed a new multi-fluid magnetohydrodynamic model. The model simulated both the ionosphere and magnetosphere as a whole. Due to the existence of the dipole magnetic field, the stellar wind cannot sweep away the atmosphere directly (like Mars due to the absence of a global dipole magnetic field), instead, the atmospheric ion loss was caused by the polar wind.
“The electrons are less massive than their parent ions, and as a result, are more easily accelerated up to and beyond the escape velocity of the planet. This charge separation between the escaping, low-mass electrons and significantly heavier, positively-charged ions sets up a polarization electric field. That electric field, in turn, acts to pull the positively charged ions along behind the escaping electrons, out of the atmosphere in the polar caps.”
Artist’s impression of the view from the most distant exoplanet discovered around the red dwarf star TRAPPIST-1. Credit: ESO/M. Kornmesser.
What they found was that their computer simulations were consistent with the current Earth-Sun system. However, in some extreme possibilities – such as exoplanets around M-type stars – the situation is very different and the escape rates could be one thousand times greater or more. The result means that even a water world, if it orbits an red dwarf star, could lose its atmosphere after about a gigayear (Gyr), one billion years.
Considering that life as we know it took around 4.5 billion years to evolve, one billion years is a relatively brief window. In fact, as Dr. Dong explained, these results indicate that planets that orbit M-type stars would be hard pressed to develop life:
“Our results indicate that the ocean planets (orbiting a Sun-like star) will retain their atmospheres much longer than the Gyr timescale as the ion escape rates are far too low, therefore, it allows a longer duration for life to originate on these planets and evolve in terms of complexity. In contrast, for exoplanets orbiting M-dwarfs, they could have their oceans depleted over the Gyr timescale due to the more intense particle and radiation environments that exoplanets experience in close-in habitable zones. If the atmosphere were to be depleted over the timescale less than Gyr, this could prove to be problematic for the origin of life (abiogenesis) on the planet.”
Once again, these results cast doubt on the potential habitability of red dwarf star systems. In the past, researchers have indicated that the longevity of red dwarf stars, which can remain in their main sequence for up to 10 trillion years or longer, make them the best candidate for finding habitable exoplanets. However, the stability of these stars and the way in which they are likely to strip planets of their atmospheres seems to indicate otherwise.
An artist’s depiction of planets transiting a red dwarf star in the TRAPPIST-1 System. Credit: NASA/ESA/STScl
Studies such as this one are therefore highly significant in that they help to address just how long a potentially habitable planet around a red dwarf star could remain potentially habitable. As Dr. Dong indicated:
“Given the importance of atmospheric loss on planetary habitability, there has been a great deal of interest in using telescopes such as the upcoming James Webb Space Telescope (JWST) to determine whether these planets have atmospheres and, if so, what their composition are like. It is expected that the JWST should be capable of characterizing these atmospheres (if present), but quantifying the escape rates accurately requires a much higher degree of precision and may not be feasible in the near-future.”
The study is also significant as far as our understanding of the Solar System and its evolution is concerned. At one time, scientists have ventured that both Earth and Venus may have been water worlds. How they made the transition from being very watery to what they are today – in the case of Venus, dry and hellish; and in the case of Earth, having multiple continents – is an all-important question.
In the future, more detailed surveys are anticipated that could help shed light on these competing theories. When the James Webb Space Telescope (JWST) is deployed in Spring of 2018, it will use its powerful infrared capabilities to study planets around nearby red dwarfs, Proxima b being one of them. What we learn about this and other distant exoplanets will go a long way towards informing our understanding of how our own Solar System evolved as well.
We’re all familiar with the idea of solar sails to explore the Solar System, using the light pressure from the Sun. But there’s another propulsion system that could harness the power of the Sun, electric sails, and it’s a pretty exciting idea.
A few weeks ago, I tackled a question someone had about my favorite exotic propulsion systems, and I rattled off a few ideas that I find exciting: solar sails, nuclear rockets, ion engines, etc. But there’s another propulsion system that keeps coming up, and I totally forgot to mention, but it’s one of the best ideas I’ve heard in awhile: electric sails. Artist concept of a solar sail demonstration mission that will use lasers for navigation. Credit: NASA.
As you probably know, a solar sail works by harnessing the photons of light streaming from the Sun. Although photons are massless, they do have momentum, and can transfer it when they bounce off a reflective surface.
In addition to light, the Sun is also blowing off a steady stream of charged particles – the solar wind. A team of engineers from Finland, led by Dr. Pekka Janhunen, has proposed building an electric sail that will use these particles to carry spacecraft out into the Solar System.
To understand how this works, I’ll need to jam a few concepts into your brain.
First, the Sun. That deadly ball of radiation in the sky. As you probably know, there’s a steady stream of charged particles, mainly electrons and protons, zipping away from the Sun in all directions. Visualization of the solar wind encountering Earth’s magnetic “defenses” known as the magnetosphere. Clouds of southward-pointing plasma are able to peel back layers of the Sun-facing bubble and stack them into layers on the planet’s nightside (center, right). The layers can be squeezed tightly enough to reconnect and deliver solar electrons (yellow sparkles) directly into the upper atmosphere to create the aurora. Credit: JPL
Astronomers aren’t entirely sure how, but some mechanism in the Sun’s corona, its upper atmosphere, accelerates these particles on an escape velocity. Their speed varies from 250 to 750 km/s.
The solar wind travels away from the Sun, and out into space. We see its effects on comets, giving them their characteristic tails, and it forms a bubble around the Solar System known as the heliosphere. This is where the solar wind from the Sun meets the collective solar winds from the other stars in the Milky Way.
The solar wind does cause a direct pressure, like an actual wind, but it’s incredibly weak, a fraction of the light pressure a solar sail experiences. This artist’s concept shows the Voyager 1 spacecraft entering the space between stars. Interstellar space is dominated by plasma, ionized gas (illustrated here as brownish haze), that was thrown off by giant stars millions of years ago.Credit: NASA.
But the solar wind contains a stream of positively charged protons and electrons, and this is the key.
An electric sail works by reeling out an incredibly thin wire, just 25 microns thick, but 20 kilometers long. The spacecraft is equipped with solar panels and an electron gun which takes just a few hundred watts to run.
By shooting electrons off into space, the spacecraft maintains a highly positive charged state. Since the protons from the Sun are also positively charged, when they encounter the positively charged tether, they “see” it a huge obstacle 100 meters across, and crash into it.
By imparting their momentum into the tether and spacecraft, the ions accelerate it away from the Sun.
The amount of acceleration is very weak, but it’s constant pressure from the Sun and can add up over a long period of time. For example, if a 1000 kg spacecraft had 100 of these wires extending out in all directions, it could receive an acceleration of 1 mm per second per second.
In the first second it travels 1 mm, and then 2 mm in the next second, etc. Over the course of a year, this spacecraft could be going 30 km/s. Just for comparison, the fastest spacecraft out there, NASA’s Voyager 1, is merely going about 17 km/s. So, much faster, definitely on an escape velocity from the Solar System.
One of the downsides of the method, actually, is that it won’t work within the Earth’s magnetosphere. So an electric sail-powered spacecraft would need to be carried by a traditional rocket away from the Earth before it could unfurl its sail and head out into deep space.
I’m sure you’re wondering if this is a one-way trip to get away from the Sun, but it’s actually not. Just like with solar sails, a electric sail can be pivoted. Depending on which side of the sail the solar wind hits, it either raises or lowers the spacecraft’s orbit from the Sun.
Strike the sail on one side and you raise its orbit to travel to the outer Solar System. But you could also strike the other side and lower its orbit, allowing it to journey down into the inner Solar System. It’s an incredibly versatile propulsion system, and the Sun does all the work.
Although this sounds like science fiction, there are actually some tests in the works. An Estonian prototype satellite was launched back in 2013, but its motor failed to reel out the tether. The Finnish Aalto-1 satellite was launched in June 2017, and one of its experiments is to test out an electric sail.
We should find out if the technique is viable later this year.
It’s not just the Finns who are considering this propulsion system. In 2015, NASA announced that they had awarded a Phase II Innovative Advanced Concepts grant to Dr. Pekka Janhunen and his team to explore how this technology could be used to reach the outer Solar System in less time than other methods.
The Heliopause Electrostatic Rapid Transit System, or HERTS spacecraft would extend 20 of these electric tethers outward from the center, forming a huge circular electric sail to catch the solar wind. By slowly rotating the spacecraft, the centrifugal forces will stretch the tethers out into this circular shape. Artist’s illustration of NASA’s Heliopause Electrostatic Rapid Transit System. Credit: NASA
With its positive charge, each tether acts like a huge barrier to the solar wind, giving the spacecraft an effective surface area of 600 square kilometers once it launches from the Earth. As it gets farther, from Earth, though, its effective area increases to the equivalent of 1,200 square km by the time it reaches Jupiter.
When a solar sail starts to lose power, an electric sail just keeps accelerating. In fact, it would keep accelerating out past the orbit of Uranus.
If the technology works out, the HERTS mission could reach the heliopause in just 10 years. It took Voyager 1 35 years to reach this distance, 121 astronomical units from the Sun.
But what about steering? By changing the voltage on each wire as the spacecraft rotates, you could have the whole sail interact differently on one side or the other to the solar wind. You could steer the whole spacecraft like the sails on a boat.
In September 2017, a team of researchers with the Finnish Meteorological Institute announced a pretty radical idea for how they might be able to use electric sails to comprehensively explore the asteroid belt.
Instead of a single spacecraft, they proposed building a fleet of 50 separate 5-kg satellites. Each one would reel out its own 20 km-long tether and catch the Sun’s solar wind. Over the course of a 3-year mission, the spacecraft would travel out to the asteroid belt, and visit several different space rocks. The full fleet would probably be able to explore 300 separate objects. This image depicts the two areas where most of the asteroids in the Solar System are found: the asteroid belt between Mars and Jupiter, and the trojans, two groups of asteroids moving ahead of and following Jupiter in its orbit around the Sun.
Each spacecraft would be equipped with a small telescope with only a 40 mm aperture. That’s about the size of a spotting scope, or half a pair of binoculars, but it would be enough to resolve features on the surface of an asteroid as small as 100 meters across. They’d also have an infrared spectrometer to be able to determine what minerals each asteroid is made of.
That’s a great way to find that $10 trillion asteroid made of solid platinum.
Because the spacecraft would be too small to communicate all the way back to Earth, they’d need to store the data on board, and then transmit everything once they came past our planet 3 years later.
The planetary scientists I’ve talked to love the idea of being able to survey this many different objects at the same time, and the electric sail idea is one of the most efficient methods to do it.
According to the researchers, they could do the mission for about $70 million, bringing the cost to analyze each asteroid down to about $240,000. That would be cheap compared to any other method proposed of studying asteroids.
Space exploration uses traditional chemical rockets because they’re known and reliable. Sure they have their shortcomings, but they’ve taken us across the Solar System, to billions of kilometers away from Earth.
But there are other forms of propulsion in the works, like the electric sail. And over the coming decades, we’re going to see more and more of these ideas put to the test. A fuel free propulsion system that can carry a spacecraft into the outer reaches of the Solar System? Yes please.
I’ll keep you posted when more electric sails are tested.
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John B. Charles, Ph.D., is the Chief Scientist of NASA’s Human Research Program (HRP), responsible for the scientific direction of human research and technology development enabling astronauts to go beyond low Earth orbit and eventually to Mars.
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Google Maps now lets users explore the Solar System. Credit: NASA/Google
Chances are, at one time or another, we’ve all used Google Maps to find the shortest route from point A to point B. But if you are like some people, you’ve used this mapping tool to have a look at geographical features or places you hope to visit someday. In an age where digital technology is allowing for telecommuting and even telepresence, it’s nice to take virtual tours of the places we may never get to see in person.
But now, Google Maps is using its technology to enable the virtual exploration of something far grander: the Solar System! Thanks to images provided by the Cassini orbiter of the planets and moons it studied during its 20 year mission, Google is now allowing users to explore places like Venus, Mercury, Mars, Europa, Ganymede, Titan, and other far-off destinations that are impossible for us to visit right now.
Similar to how Google Earth uses satellite imagery to create 3D representations of our planet, this new Google Maps tool relies on the more than 500,000 images taken by Cassini as it made its way across the Solar System. This probe recently concluded its 20 year mission, 13 of which were spent orbiting Saturn and studying its system of moons, by crashing into the atmosphere of Saturn.
Artist rendition of the Cassini spacecraft over Saturn. Credit: NASA/JPL-Caltech/SSI/Kevin M. Gill.
After launching from Earth on October 15th, 1997, Cassini conducted a flyby of Venus in order to pick up a gravity-assist. It then flew by Earth, obtaining a second gravity-assist, while making its way towards the Asteroid Belt. Before reaching the Saturn System, where it would begin studying the gas giant and its moons, Cassini also conducted a flyby of Jupiter – snapping pictures of its moons, rings, and Great Red Spot.
When it reached Saturn in July of 2004, Cassini went to work studying the planet and its larger moons – particularly Titan and Enceladus. During the next 13 years and 76 days, the probe would provide breathtaking images and sensor data on Saturn’s rings, atmosphere and polar storms and reveal things about Titan’s surface that were never before seen (such as its methane lakes, hydrological cycle, and surface features).
It’s flybys of Enceladus also revealed some startling things about this icy moon. Aside from detecting a tenuous atmosphere of ionized water vapor and Enceladus’ mysterious “Tiger Stripes“, the probe also detected jets of water and organic molecules erupting from the moon’s southern polar region. These jets, it was later determined, were indicative of a warm water ocean deep in the moon’s interior, and possibly even life!
Interestingly enough, the original Cassini mission was only planned to last for four years once it reached Saturn – from June 2004 to May 2008. But by the end of this run, the mission was extended with the Cassini Equinox Mission, which was intended to run until September of 2010. It was extended a second time with the Cassini Solstice Mission, which lasted until September 15th, 2017, when the probe was crashed into Saturn’s atmosphere.
Artist’s impression of the Cassini orbiter entering Saturn’s atmosphere. Credit: NASA/JPL
Thanks to all the images taken by this long-lived mission, Google Maps is now able to offer exploratory tours of 16 celestial bodies in the Solar System – 12 of which are new to the site. These include Earth, the Moon, Mercury, Venus, Mars, Pluto, Ceres, Io, Europa, Ganymede, Mimas, Enceladus, Dione, Rhea, Titan, Iapetus and (available as of July 2017) the International Space Station.
This latest development also builds on several extensions Google has released over the years. These include Google Moon, which was released on July 20th, 2005, to coincide with the 36th anniversary of the Apollo 11 Moon Landing. Then there was Google Sky (introduced in 2007), which used photographs taken by the Hubble Space Telescope to create a virtual map of the visible universe.
Then there was Google Mars, the result of a collaborative effort between Google and NASA scientists at the Mars Space Flight Facility released in 2011, one year before the Curiosity rover landed on the Red Planet. This tool relied on data collected by the Mars Global Surveyor and the Mars Odyssey missions to create high-resolution 3D terrain maps that included elevations.
In an age of high-speed internet and telecommunications, using the internet to virtually explore the many planets and bodies of the Solar System just makes sense. Especially when you consider that even the most ambitious plans to conduct tourism to Mars or the Moon (looking at you, Elon Musk and Richard Branson!) are not likely to bear fruit for many years, and cost an arm and a leg to boot!
In the future, similar technology could lead to all kinds of virtual exploration. This concept, which is often referred to as “telexploration”, would involve robotic missions traveling to other planets and even star systems. The information they gather would then be sent back to Earth to create virtual experiences, which would allow scientists and space-exploration enthusiasts to feel like they were seeing it firsthand.
In truth, this mapping tool is just the latest gift to be bestowed by the late Cassini mission. NASA scientists expect to be sifting through the volumes of data collected by the orbiter for years to come. Thanks to improvements made in software applications and the realms of virtual and augmented reality, this data (and that of present and future missions) is likely to be put to good use, enabling breathtaking and educational tours of our Universe!
