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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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!
Have you noticed that weather forecasting has gotten much better in the last few years? Thanks to weather satellites, weather stations, and better forecasting techniques. How do scientists predict the weather with any kind of accuracy days or even weeks in the future.
If you would like to join the Weekly Space Hangout Crew, visit their site here and sign up. They’re a great team who can help you join our online discussions!
Covert NROL-52 spy satellite for the National Reconnaissance Office fades into cloudy nighttime skies shrouded in secrecy after liftoff on a United Launch Alliance (ULA) Atlas V rocket at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com
Covert NROL-52 spy satellite for the National Reconnaissance Office fades into cloudy nighttime skies shrouded in secrecy after liftoff on a United Launch Alliance (ULA) Atlas V rocket at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com
CAPE CANAVERAL AIR FORCE STATION, FL — As one Atlas rocket carrying a covert spy satellite for the U.S. National Reconnaissance Office (NRO) to monitor Earth for national security purposes faded into cloudy nighttime skies over the Cape in the dead of night shrouded in liftoff secrecy, rocket builder United Launch Alliance (ULA) won another significant Atlas launch contract for NASA’s Landsat 9 satellite to monitor the health of Earth’s environment.
Capping two launches from two different rocket companies in four days by ULA and SpaceX followed by the arrival back in port of SpaceX’s ocean landed recovered booster, last week provided all the proof that’s needed to demonstrate that the revitalization of Florida’s Spaceport is well underway and America’s rocket makers are capturing lucrative launch contracts ensuring an upswing nationwide in rocket and spacecraft manufacturing – for critical military surveillance, government, civilian and science needs.
Check out the exciting gallery of Atlas launch imagery and videos including the thrilling droneship return of SpaceX’s 156 foot tall first stage booster back into Port Canaveral less than 4 hours after ULA delivered the classified NROL-52 surveillance satellite to a secret orbit – from this author and several space media colleagues. And check back here as the gallery grows!
A ULA Atlas V launch carrying the covert NROL-52 mission in support of U.S. national security blasted off overnight Sunday, Oct. 15 at 3:28 a.m. EDT (0728 GMT) from seaside Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida.
“Congratulations to the team who helped make #NROL52 a success! United Launch Alliance, 45th Space Wing at Patrick Air Force Base, Fla., Air Force Space Command, and the Space and Missile Systems Center,” the NRO announced post launch on social media.
It was a case of ‘Going, Going, Gone’ as seemingly endless stormy weather plagued the space coast and the Atlas soon disappeared behind clouds from many but not all vantage points, as the two stage rocket was finally cleared to launch on its fifth try. Postponed three times by poor weather and once due to a technical glitch to fix a faulty second stage transmitter.
Reflecting in a pond a United Launch Alliance (ULA) Atlas V rocket blasts off with the covert NROL-52 spy satellite for the National Reconnaissance Office at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com
“We’ve had an incredible month,” said Brig. Gen. Wayne R. Monteith, Commander, 45th Space Wing.
“Not only did we restore our base to full mission capable status just a few hours after Hurricane Irma impacted our coast, but we’ve successfully launched two rockets in less than four days just weeks later.”
Covert NROL-52 spy satellite for the National Reconnaissance Office fades into cloudy nighttime skies shrouded in secrecy after liftoff on a United Launch Alliance (ULA) Atlas V rocket at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com
“The 45th Space Wing supported ULA’s Atlas V launch of the NROL-52 mission for the National Reconnaissance Office early morning on Oct. 15!”
“The men and women of the 45th Space Wing continue to make the impossible possible.”
Reflecting in a pond a United Launch Alliance (ULA) Atlas V rocket blasts off with the covert NROL-52 spy satellite for the National Reconnaissance Office at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com
More than a quarter of all the world’s rocket launches take place from Florida’s burgeoning spaceports.
Covert NROL-52 spy satellite for the National Reconnaissance Office fades into cloudy nighttime skies shrouded in secrecy after liftoff on a United Launch Alliance (ULA) Atlas V rocket at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com
“Our team’s resiliency and tireless efforts in launching over 25% of all world-wide launches this year proves why we are the ‘World’s Premier Gateway to Space,’” Montieth gushed in pride.
Meanwhile, NASA selected ULA to provide launch services for the Landsat 9 mission with another Atlas V rocket as soon as late 2020.
“The mission is currently targeted for a contract launch date of June 2021, while protecting for the ability to launch as early as December 2020, on an Atlas V 401 rocket from Space Launch Complex 3E at Vandenberg Air Force Base in California,” said NASA.
The Landsat 9 launch contract is worth $153.8 million.
Landsat 9 is a joint mission between NASA and the U.S. Geological Survey (USGS).
“Landsat 9 will continue the Landsat program’s critical role in monitoring, understanding, and managing the land resources needed to sustain human life.”
“We are honored that NASA has entrusted ULA with launching this critical land imaging satellite,” said Tory Bruno, ULA’s president and chief executive, in a statement.
“ULA’s world-leading performance and reliability, paired with the tremendous heritage of 74 consecutive successful Atlas V launches, provides the optimal value for our customer. We look forward to working together again with our mission partners at NASA’s Launch Services Program, Goddard Space Flight Center and the U.S. Geological Survey in the integration and launch of this significant mission, contributing to the international strategy for examining the health and state of the Earth.”
ULA Atlas V rocket streaks to orbit in this long duration exposure carrying covert NROL-52 payload for the NRO after lift off from Space Launch Complex-41 on Oct. 15, 2017 at 3:28 a.m. EDT at Cape Canaveral Air Force Station in Florida. Credit: Jeff Seibert
NROL-52 is the fourth of five launches slated for the NRO in 2017 by both ULA and SpaceX.
“Never before has innovation been more important for keeping us ahead of the game. As the eagle soars, so will the advanced capabilities this payload provides to our national security,” said Colonel Matthew Skeen, USAF, Director, NRO Office of Space Launch, in a statement. “Kudos to the entire team for a job well done.”
Check out this exciting video compilation from remote cameras circling the Atlas pad 41.
Video Caption: Launch of the NROL-52 satellite on an Atlas 5 booster from Pad 41. A United Launch Alliance Atlas 5 421 rocket launches the NROL-52 payload on Oct. 15, 2017 at 328 a.m. EDT on the 5th launch attempt. Previous launch attempts were halted by weather issues 3 times, and a faulty telemetry radio that needed to be replaced after the rocket was rolled back to the Pad 41 Vertical Integration Facility. Credit Jeff Seibert
The venerable two stage Atlas V stands 194 feet tall and sports a 100% success record. The first stage generates approx. 1.6 million pounds of liftoff thrust.
This Atlas Evolved Expendable Launch Vehicle (EELV) mission launched in the 421 configuration vehicle, which includes a 4-meter payload fairing (PLF) encapsulating the payload and two strap on solid rocket first stage boosters.
The Atlas first stage booster for this mission was powered by the Russian-built RD AMROSS RD-180 engine, and the Centaur upper stage was powered by the Aerojet Rocketdyne RL10C-1 engine.
The dual chamber, dual-nozzle RD-180 is fueled by a mixture of RP-1 kerosene and LOX (liquid oxygen).
The ULA Atlas V first stage powers NROL-52 spy satellite to orbit for the NRO firing the dual chamber, dual-nozzle RD-180 engines after blastoff at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com
The next NRO launch is scheduled on a ULA Delta IV in December from Vandenberg Air Force Base, California.
Reflecting in a pond a United Launch Alliance (ULA) Atlas V rocket blasts off with the covert NROL-52 spy satellite for the National Reconnaissance Office at 3:28 a.m. EDT on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.com
Watch for Ken’s continuing onsite NROL-52, SpaceX SES-11 and NASA and space mission reports direct from the Kennedy Space Center and Cape Canaveral Air Force Station, Florida.
Stay tuned here for Ken’s continuing Earth and Planetary science and human spaceflight news.
Liftoff of ULA Atlas V rocket carrying classified NROL-52 payload for the NRO on Oct. 15, 2017 from Cape Canaveral Air Force Station in Florida. Credit: Julian LeekUnited Launch Alliance (ULA) Atlas V rocket streaks to orbit in this long duration exposure carrying covert NROL-52 payload for the National Reconnaissance Office after lift off from Space Launch Complex-41 on Oct. 15, 2017 at 3:28 a.m. EDT at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.comReflecting in a pond a ULA Atlas V rocket stands poised for launch with the NROL-52 surveillance satellite for the National Reconnaissance Office prior to blastoff on Oct. 15, 2017 from Space Launch Complex-41 at Cape Canaveral Air Force Station in Florida. Credit: Ken Kremer/kenkremer.comReflown SpaceX Falcon 9 first stage booster arrives at sunrise atop OCISLY droneship being towed into the mouth of Port Canaveral, FL on Oct. 15, 2017 after successfully launch SES-11 UHDTV comsat to orbit on Oct. 11, 2017. Credit: Ken Kremer/Kenkremer.comULA Atlas V rocket blasts off carrying covert NROL-52 payload for the NRO from Space Launch Complex-41 on Oct. 15, 2017 at 3:28 a.m. EDT at Cape Canaveral Air Force Station in Florida. Credit: Jeff Seibert
An artist's impression of a Nearth-Earth Asteroid (NEA) breaking up. Credit: NASA/JPL-Caltech
Beyond Earth’s orbit, there are innumerable comets and asteroids that are collectively known as Near-Earth Objects. On occasion, some of these objects will cross Earth’s orbit; and every so often, one will pass too close to Earth and impact on its surface. While most of these objects have been too small to cause serious damage, some have been large enough to trigger Extinction Level Events (ELEs).
For this reason, NASA and other space agencies have spent decades cataloging and monitoring the larger NEAs in order to determine if they might collide with Earth at some point in the future. The only question has been, how many remain to be found? According to a recent analysis performed by Alan W. Harris of MoreData! – a California-based research company – only a handful of NEAs haven’t been catalogued yet.
These findings were the subject of a presentation made this week at the 49th annual meeting of the American Astronomical Society’s Division for Planetary Sciences in Provo, Utah. As Harris indicated during the presentation, titled “The Population of Near-Earth Asteroids Revisited”, previous estimates of the remaining NEAs have been plagued by a consequential round-off error that have skewed the results.
Artist’s concept of the Wide-field Infrared Survey Explorer as its orbit around Earth. Credit: NASA/JPL
The source of this error has to do with how organizations that monitor NEOs determine “size-frequency distribution”. Basically, estimates are given in terms of number versus brightness, since most discovery surveys were conducted in the visible spectrum. This is not a reliable way of determining size though, since asteroids don’t all have the same albedo (aka. reflectivity).
As such, NEA brightness is expressed in units of absolute magnitude (H), where lower numbers indicate brighter objects. The IAU Minor Planet Center – which is responsible for maintaining information on asteroid and other small-body measurements – rounds off the reported values of H to the nearest 0.1 magnitude. As Harris explained during the course of his presentation:
“So, for example, a bin from H of 17.5 to 18.0 is really from 17.55 to 18.05, or 17.45 to 17.95, depending on which side of the bin you take “less than or equal to” rather than ‘less than’.”
While this has not caused much in the way of problems in the past, it has become significant as far as assessments of how many larger objects remain to be found are concerned. Harris first became aware of the potential for problems this past year after Dr. Pasqual Tricario – a Senior Scientist at the Planetary Science Institute – conducted a study that produced estimates different from those obtained by Harris and Italian astronomer Germano D’Abramo two years before.
This graphic shows asteroids and comets observed by NASA’s Near-Earth Object Wide-field Survey Explorer (NEOWISE) mission. Credit: NASA/JPL-Caltech/UCLA/JHU
The 2015 study conducted by Harris and D’Abramo – which appeared in Icarus under the title “The population of near-Earth asteroids” – yielded an estimate of 990 NEAs that were larger than 1 km in diameter. However, Tricario’s study (“The near-Earth asteroid population from two decades of observations“, also published in Icarus), which was based on the opposite “less than or equal to” assumption, produced estimates that were 10% lower.
As Harris explained, this prompted D’Adramo and him to considered a different approach. “We corrected the problem for the current analysis by choosing bin boundaries at .05 magnitudes, e.g. 17.25 to 17.75, so the 0.1 round-off thresholds naturally put objects in the right bin,” he said. “When Tricarico and I each made these corrections, our population estimates fell into almost perfect agreement.”
After applying the correction, Harris and D’Abramo’s overall estimate of undiscovered NEAs dropped from 990 to 921 ± 20. Beyond allowing for consistency between different studies, these corrected estimates also reduced the total number of undiscovered objects that remain undiscovered. According to the latest tallies from NASA’s Jet Propulsion Laboratory, 884 NEAs that are about 1 km in diameter have been discovered so far.
Based on the previous population estimate of 990 objects, this implied that the current surveys are 89% complete and 106 were yet to be found. When the corrections were applied to these numbers, JPL’s surveys now appears to be 96% complete, and only 37 objects remain to be found (almost three times less). Naturally, these new estimates depends on their own sets of assumptions, and different results can be obtained based on different criteria.
NASA is getting much better at discovering and detecting NEOs. Credit: NASA/NEO Program.
Still, a reduced estimate of undiscovered asteroids is definitely encouraging news. Especially when one considers how hazardous large asteroids are to the safety and well-being of life here on Earth. As of October 3rd, 2017, NASA’s Center for Near-Earth Object Studies (CNEOS) announced that there are a total of 157 potentially hazardous asteroids out there. Knowing that only a few more need to be found is bound to help some of us sleep at night!
Future studies are also expected to benefit from the deployment of next-generation missions. Thanks to the efforts of NASA’s Near-Earth-Object WISE (NEOWISE) mission, which looks for NEOs in the infrared band (rather than visible light), that number of known NEOs has increased substantially. With the deployment of the James Webb Space Telescope, those numbers are expected to reach even higher.
Between improvements in technology and methodology, a day may yet come when all Near-Earth Objects – be they big or small, potentially hazardous or harmless – are accounted for. Combined with asteroid defenses, like directed-energy beams or robots spacecraft capable of attaching themselves to asteroids and redirecting them, Extinction Level Events might very well become a thing of the past.
