JPL’s venerable Ed Stone, the Project Scientist for the Voyager spacecraft for over 40 years, made an appearance on the Colbert Report last night, bantering easily with the no-holds-barred host and discussing the significance of the Voyager mission, from the two launches in 1977 to Voyager 1’s recent celebrated arrival in interstellar space.
Colbert also was tasked by NASA to present Stone with NASA’s Distinguished Public Service Medal for a lifetime of scientific achievement. See below:
Another blow was dealt to deep space exploration this past weekend. The announcement comes from Jim Green, NASA’s Planetary Science Division Director. The statement outlines some key changes in NASA’s radioisotope program, and will have implications for the future exploration of the outer solar system.
An Advanced Stirling Converter prototype in the laboratory. (Credit: NASA).
While it’s true that there’s no air to carry sound in space, starship explosions would be strangely silent and no one can hear you scream, this latest Science @ NASA video reminds us that “space can make music, if you know how to listen.”
And the “how” in this case is with the Plasma Wave Science Experiment aboard the Voyager 1 spacecraft, which is now playing the sounds of interstellar space — with a little help from University of Iowa physics professor and experiment principal investigator Don Gurnett. Watch the video above for a front-row seat (and read more about Voyager’s historic crossing of the heliosphere here.)
Neptune's system of moons and rings visualized. Credit: SETI
“That’s no moon…”
-B. Kenobi
But in this case, it is… a lost moon of Neptune not seen since its discovery in the late 1980’s.
A new announcement from the 45th Meeting of the Division for Planetary Sciences of the American Astronomical Society being held this week in Denver, Colorado revealed the recovery of a moon of Neptune that was only briefly glimpsed during the 1989 flyby of Voyager 2.
The re-discovery Naiad, the innermost moon of Neptune, was done by applying new processing techniques to archival Hubble images and was announced today by Mark Showalter of the SETI institute.
Collaborators on the project included Robert French, also from the SETI Institute, Dr. Imke de Pater of UC Berkeley, and Dr. Jack Lissauer of the NASA Ames Research Center.
The findings were a tour-de-force of new techniques applied to old imagery, and combined the ground-based 10 meter Keck telescope in Hawaii as well as Hubble imagery stretching back to December 2004.
The chief difficulty in recovering the diminutive moon was its relative faintness and proximity to the “dazzling” disk of Neptune. At roughly 100 kilometres in diameter and an apparent magnitude of +23.9, Naiad is over a million times fainter than +8th magnitude Neptune. It’s also the innermost of Neptune’s 14 known moons, and orbits once every 7 hours just 23,500 kilometres above the planet’s cloud tops. Neptune itself is about 49,000 kilometres in diameter, and only appears 2.3” in size from Earth. From our Earthly vantage point, Naiad only strays about arc second from the disk of Neptune, a tiny separation.
“Naiad has been an elusive target ever since Voyager left the Neptune system,” Showalter said in a recent SETI Institute press release. Voyager 2 has, to date, been the only mission to explore Uranus and Neptune.
To catch sight of the elusive inner moon, Showalter and team applied new analyzing techniques which filtered for glare and image artifacts that tend to “spill over” from behind the artificially occulted disk of Neptune.
Other moons, such as Galatea and Thalassa — which were also discovered during the 1989 Voyager 2 flyby — are also seen in the new images. In fact, the technique was also used to uncover the as of yet unnamed moon of Neptune, S/2004 N1 which was revealed earlier this year.
Naiad is named after the band of nymphs in Greek mythology who inhabited freshwater streams and ponds. The Naiads differed from the saltwater-loving Nereids of mythology fame, after which another moon of Neptune discovered by Gerard Kuiper in 1949 was named.
It’s also intriguing to note that Naiad was discovered in a significantly different position in its orbit than expected. Clearly, its motion is complex due to its interactions with Neptune’s other moons.
“We don’t quite have enough observations to establish a refined orbit,” Mr. Showalter told Universe Today, noting that there may still be some tantalizing clues waiting to be uncovered from the data.
I know the burning question you have, and we had as well during the initial announcement today. Is it REALLY Naiad, or another unknown moon? Showalter notes that this possibility is unlikely, as both objects seen in the Hubble and Voyager data are the same brightness and moving in the same orbit. To invoke Occam’s razor, the simplest solution— that both sightings are one in the same object —is the most likely.
“Naiad is well inside Neptune’s Roche Limit, like many moons in the solar system,” Mr. Showalter also told Universe Today. Naiad is also well below synchronous orbit, and is likely subject to tidal deceleration and may one day become a shiny new ring about the planet.
The labeled ring arcs of Neptune as seen in newly processed data. The image spans 26 exposures combined into an equivalent 95 minute exposure. The ring trace and an image of the occulted planet Neptune is added for reference. (Credit: M. Showalter/SETI Institute).
And speaking of which, the tenuous rings of Neptune have also evolved noticeably since the 1989 Voyager flyby. First discovered from the ESO La Silla Observatory in 1984, data using the new techniques show that the knotted ring segments named the Adams and Le Verrier have been fading noticeably.
“In a decade or two, we may see an ‘arc-less’ ring,” Showalter noted during today’s Division for Planetary Sciences press conference. The two ring segments observed are named after Urbain Le Verrier and John Couch Adams, who both calculated the position of Neptune due to orbital perturbations of the position of Uranus. Le Verrier beat Adams to the punch, and Neptune was first sighted from the Berlin Observatory on the night of September 23rd, 1846. Observers of the day were lucky that both planets had undergone a close passage just decades prior, or Neptune may have gone unnoticed for considerably longer.
The rings of Neptune as seen from Voyager 2 during the 1989 flyby. (Credit: NASA/JPL).
Neptune has completed just over one 164.8 year orbit since its discovery. It also just passed opposition this summer, and is currently a fine telescopic object in the constellation Aquarius.
Unfortunately, there aren’t any plans for a dedicated Neptune mission in the future. New Horizons will cross the orbit of Neptune in August 2014, though it’s headed in the direction of Pluto, which is currently in northern Sagittarius. New Horizons was launched in early 2006, which gives you some idea of just how long a “Neptune Orbiter” would take to reach the outermost ice giant, given today’s technology.
This represents the first time that Naiad has been imaged from the vicinity of Earth, and demonstrates a new processing technique capable of revealing new objects in old Hubble data.
“We keep discovering new ways to push the limit of what information can be gleaned from Hubble’s vast collection of planetary images,” Showalter said in the SETI press release.
Congrats to Showalter and team on the exciting recovery… what other moons, both old and new, lurk in the archives waiting to be uncovered?
– Read today’s SETI Institute press release on the recovery of Naiad.
-Be sure to follow all the action at the 45th DPS conference in Denver this week!
Artist's concept of NASA's Voyager spacecraft. Image credit: NASA/JPL-Caltech
Our favorite astro-poet, Stuart Atkinson, has written a wonderful ode to Voyager 1 in commemoration of the spacecraft reaching interstellar space. Stu has a knack for turning science into poetry!
The First Starship
I needed no nacelles to push me onwards;
No dilithium crystals crackled in my heart.
Yet I have left Sol so far behind me she is
Just a star now, a golden spark in a salt grain sea,
And I can feel her gentle breath on my cheek
No more.
In my ears now the whalesong of the universe
Drowns out the sounds of distant, troubled Earth.
Oh, the blissful peace!
Out here all I can hear
Is the fabled music of the spheres.
Each trembling tone rolling under me,
Every mellow note washing over me
Was sung somewhere Out There.
Melodies ripped from ravenous black holes’ throats,
Screamed from the broken hearts of dying stars
Swirl around me, multi-wavelength whispers
In the dark and endless night.
My head is full of memories…
Skimming Titan’s marmalade-haze atmosphere;
My first sight of Jove’s great bloodshot eye,
Staring back at me, into me, as I flew by;
Earth as Pale Blue Dot, a Sagan sequin
Dancing in a sunbeam…
Ahead now – the solar system’s Barrier Reef.
Terra will whip around Sol 300 times before
I reach the Oort’s icy inner harbour wall
And tens of thousands of times more before
I finally leave port, sailing on in serene silence
For forty millennia more before I venture anywhere
Near another star…
And in ten million years, when Earth’s proud citadels
And cities have crumbled and whatever evolves
In their dust to take Mankind’s place
Stares out into space with curious, alien eyes,
I will still be flying through the stars.
Your legacy. Proof that once you dared to dream
Noble, Camelot dreams
And reached out, through me, to explore eternity.
(c) Stuart Atkinson Sept 13th 2013
Written to commemorate and celebrate the Sept 12, 2013 announcement that Voyager 1 had entered interstellar space.
On the Voyager spacecraft are the famous Voyager Golden Records, which send messages from planet Earth to … whatever or whoever may find it in the future. In celebration of Voyager 1 making it into interstellar space (read all the details here) a few friends put together a video to congratulate the spacecraft and the team. Neil deGrasse Tyson, Wil Wheaton, Carl Sagan’s son and others shared their messages to the Voyager 1 spacecraft.
Feel free to leave your message to Voyager in the (new and improved) comment section.
This artist's concept shows the general locations of NASA's two Voyager spacecraft. Voyager 1 (top) has sailed beyond our solar bubble into interstellar space, the space between stars. Its environment still feels the solar influence. Voyager 2 (bottom) is still exploring the outer layer of the solar bubble. Image credit: NASA/JPL-Caltech
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.
In a cosmically historic announcement, NASA says the most distant human made object — the Voyager 1 spacecraft — is in interstellar space, the space between the stars. It actually made the transition about a year ago.
“We made it!” said a smiling Dr. Ed Stone, Voyager’s Project Scientist for over 40 years, speaking at a briefing today. “And we did it while we still had enough power to send back data from this new region of space.”
While there is a bit of an argument on the semantics of whether Voyager 1 is still inside or outside of our Solar System (it is not farther out than the Oort Cloud — it will take 300 more years reach the Oort cloud and the spacecraft is closer to our Sun than any other star) the plasma environment Voyager 1 now travels through has definitely changed from what comes from our Sun to the plasma that is present in the space between stars.
But Stone now says the evidence in clear: Voyager 1 has made the transition.
“This conclusion is possible from the space craft’s plasma wave instrument,” Stone said. “The 36-year old probe is now sailing through uncharted waters of a new cosmic sea and it has brought us along for the journey.”
Voyager 1’s 36-year, 13 billion mile journey began in 1977.
Scientists thought that when the spacecraft had crossed over into interstellar space, the magnetic field direction would change. However, it turned out that didn’t happen, and scientists determined they needed to look at the properties of the plasma instead.
The Sun’s heliosphere is filled with ionized plasma from the Sun. Outside that bubble, the plasma comes from the explosions of other stars millions of years ago. The main tell-tail difference is the interstellar plasma is denser.
Unfortunately, the real instrument that was designed to make the measurements on the plasma quit working in the 1980’s, so scientists needed a different way to measure the spacecraft’s plasma environment to make a definitive determination of its location.
Instead they used the plasma wave instrument, located on the 10-meter long antennas on Voyager 1 and an unexpected “gift” from the Sun, a massive Coronal Mass Ejection.
The antennas have radio receivers at the ends – “like the rabbit ears on old television sets,” said Don Gurnett, who led the plasma wave science team at the University of Iowa. The CME erupted from the Sun in March 2012, and eventually arrived at Voyager 1’s location 13 months later, in April 2013. Because of the CME, the plasma around the spacecraft began to vibrate like a violin string.
The pitch of the oscillations helped scientists determine the density of the plasma. Stone said the particular oscillations meant the spacecraft was bathed in plasma more than 40 times denser than what they had encountered in the outer layer of the heliosphere.
“Now that we have new, key data, we believe this is mankind’s historic leap into interstellar space,” said Stone, “The Voyager team needed time to analyze those observations and make sense of them. But we can now answer the question we’ve all been asking — ‘Are we there yet?’ Yes, we are.”
Artist’s impression of Voyager 1’s position on the sky when observed by the Very Long Baseline Array (VLBA) on February 21, 2013, at which point — according to NASA’s Jet Propulsion Laboratory — Voyager was already outside of our Solar System. The actual image from the data (enlarged section) is 0.5 arcseconds across. The radio signal as shown is a mere 1 milliarcsecond across. Credit: Alexandra Angelich, NRAO/AUI/NSF.
The plasma wave science team reviewed its data and found an earlier, fainter set of oscillations in October and November 2012 from other CMEs. Through extrapolation of measured plasma densities from both events, the team determined Voyager 1 first entered interstellar space in August 2012.
“We literally jumped out of our seats when we saw these oscillations in our data — they showed us the spacecraft was in an entirely new region, comparable to what was expected in interstellar space, and totally different than in the solar bubble,” Gurnett said. “Clearly we had passed through the heliopause, which is the long-hypothesized boundary between the solar plasma and the interstellar plasma.”
At that time, Stone said, “We are certainly in a new region at the edge of the solar system where things are changing rapidly. But we are not yet able to say that Voyager 1 has entered interstellar space,” adding that the data are changing in ways that the team didn’t expect, “but Voyager has always surprised us with new discoveries.”
Now, after further review, the Voyager team generally accepts the August 2012 date as the date of interstellar arrival. The charged particle and plasma changes were what would have been expected during a crossing of the heliopause. This reinforces that definitive science results don’t always come fast.
“The team’s hard work to build durable spacecraft and carefully manage the Voyager spacecraft’s limited resources paid off in another first for NASA and humanity,” said Suzanne Dodd, Voyager project manager, based at NASA’s Jet Propulsion Laboratory, Pasadena, Calif. “We expect the fields and particles science instruments on Voyager will continue to send back data through at least 2020. We can’t wait to see what the Voyager instruments show us next about deep space.”
There has been some back and forth about whether Voyager 1 was in or out of the Solar System. As we said, it was first questioned in August of 2012, with more speculation in December 2012, then in March of 2013 a paper by William Webber and F.B. McDonald claimed Voyager 1 had exited the Solar System the previous December, but Stone insisted the data wasn’t positive yet. Then about a month ago a paper came out by Marc Swisdak from the University of Maryland saying Voyager 1 was out of the solar system, but at that point Ed Stone and the Voyager team put out a statement saying they were still making that determination.
Today, Gurnett revealed that the timing of all scientists being in “official” agreement was off due to the timing of the review process for scientific papers. “Our paper was submitted a month before theirs, they just got through the review cycle before ours,” he said. “But theirs was basically a theory paper.”
Voyager 1 and its twin, Voyager 2, were launched 16 days apart in 1977. A fortuitous planetary alignment that only happens every 176 years enabled the two spacecraft to join together to reach all the outer planets in a 12 year time period. Both spacecraft flew by Jupiter and Saturn. Voyager 2 also flew by Uranus and Neptune. Voyager 2, launched before Voyager 1, is the longest continuously operated spacecraft. It is about 9.5 billion miles (15 billion kilometers) away from our Sun.
Voyager mission controllers still talk to or receive data from Voyager 1 and Voyager 2 every day, though the emitted signals are currently very dim, at about 23 watts — the power of a refrigerator light bulb. By the time the signals get to Earth, they are a fraction of a billion-billionth of a watt. Data from Voyager 1’s instruments are transmitted to Earth typically at 160 bits per second, and captured by 34- and 70-meter NASA Deep Space Network stations. Traveling at the speed of light, a signal from Voyager 1 takes about 17 hours to travel to Earth. After the data are transmitted to JPL and processed by the science teams, Voyager data are made publicly available.
“Voyager has boldly gone where no probe has gone before, marking one of the most significant technological achievements in the annals of the history of science, and adding a new chapter in human scientific dreams and endeavors,” said John Grunsfeld, NASA’s associate administrator for science in Washington. “Perhaps some future deep space explorers will catch up with Voyager, our first interstellar envoy, and reflect on how this intrepid spacecraft helped enable their journey.”
Scientists do not know when Voyager 1 will reach the undisturbed part of interstellar space where there is no influence from our Sun. They also are not certain when Voyager 2 is expected to cross into interstellar space, but they believe it is not very far behind.
“In a sense this is only really the beginning. We’re now going into a completely alien environment and what Voyager is going to discover truly unknown,” said Gary Zank, from the Department of Space Sciences at the University of Alabama, Huntsville, speaking at today’s press conference.
While Voyager 1 will keep going, we will not always be able to communicate with it, as we do now. In 2025 all instruments will be turned off, and the science team will be able to operate the spacecraft for about 10 years after that to just get engineering data. Voyager 1 is aiming toward the constellation Ophiuchus. In the year 40,272 AD, Voyager 1 will come within 1.7 light years of an obscure star in the constellation Ursa Minor (the Little Bear or Little Dipper) called AC+79 3888. It will swing around the star and orbit about the center of the Milky Way, likely for millions of years.
Has Voyager 1 actually left the Solar System? Some researchers are saying yes. (Image: NASA/JPL-Caltech)
Nearly 18.7 billion kilometers from Earth — about 17 light-hours away — NASA’s Voyager 1 spacecraft is just about on the verge of entering interstellar space, a wild and unexplored territory of high-energy cosmic particles into which no human-made object has ever ventured. Launched in September 1977, Voyager 1 will soon become the first spacecraft to officially leave the Solar System.
Or has it already left?
I won’t pretend I haven’t heard it before: Voyager 1 has left the Solar System! Usually followed soon after by: um, no it hasn’t. And while it might all seem like an awful lot of flip-flopping by supposedly-respectable scientists, the reality is there’s not a clear boundary that defines the outer limits of our Solar System. It’s not as simple as Voyager rolling over a certain mileage, cruising past a planetary orbit, or breaking through some kind of discernible forcefield with a satisfying “pop.” (Although that would be cool.)
The outer edge of the heliosphere has been found to contain many different regions, which Voyager 1 has been passing through since 2004. (NASA/JPL-Caltech)
Rather, scientists look at Voyager’s data for evidence of a shift in the type of particles detected. Within the transitionary zone that the spacecraft has most recently been traveling through, low-energy particles from the Sun are outnumbered by higher-energy particles zipping through interstellar space, also called the local interstellar medium (LISM). Voyager’s instruments have been detecting dramatic shifts in the concentrations of each for over a year now, unmistakably trending toward the high-energy end — or at least showing a severe drop-off in solar particles — and researchers from the University of Maryland are claiming that this, along with their model of a porous solar magnetic field, indicates Voyager has broken on through to the other side.
“It’s a somewhat controversial view, but we think Voyager has finally left the Solar System, and is truly beginning its travels through the Milky Way,” said Marc Swisdak, UMD research scientist and lead author of a new paper published this week in The Astrophysical Journal Letters.
According to Swisdak, fellow UMD plasma physicist James F. Drake, and Merav Opher of Boston University, their model of the outer edge of the Solar System fits recent Voyager 1 observations — both expected and unexpected. In fact, the UMD-led team says that Voyager passed the outer boundary of the Sun’s magnetic influence, aka the heliopause… last year.
But, like some of last year’s claims, these conclusions aren’t shared by mission scientists at NASA.
“Details of a new model have just been published that lead the scientists who created the model to argue that NASA’s Voyager 1 spacecraft data can be consistent with entering interstellar space in 2012,” said Ed Stone, Voyager project scientist at Caltech, in a press release issued today. “In describing on a fine scale how magnetic field lines from the sun and magnetic field lines from interstellar space can connect to each other, they conclude Voyager 1 has been detecting the interstellar magnetic field since July 27, 2012. Their model would mean that the interstellar magnetic field direction is the same as that which originates from our sun.
The famous “Golden Record” carried aboard both Voyager 1 and 2 contains images, sounds and greetings from Earth. (NASA)
“Other models envision the interstellar magnetic field draped around our solar bubble and predict that the direction of the interstellar magnetic field is different from the solar magnetic field inside. By that interpretation, Voyager 1 would still be inside our solar bubble.”
Stone says that further discussion and investigation will be needed to “reconcile what may be happening on a fine scale with what happens on a larger scale.”
Whether still within the Solar System — however it’s defined — or outside of it, the bottom line is that the venerable Voyager spacecraft are still conducting groundbreaking research of our cosmic neighborhood, 36 years after their respective launches and long after their last views of the planets. And that’s something nobody can argue about.
“The Voyager 1 spacecraft is exploring a region no spacecraft has ever been to before. We will continue to look for any further developments over the coming months and years as Voyager explores an uncharted frontier.”
– Ed Stone, Voyager project scientist
Built by JPL and launched in 1977, both Voyagers are still capable of returning scientific data from a full range of instruments, with adequate power and propellant to remain operating until 2020.
Note: The definition of “Solar System” used in this article is in reference to the Sun’s magnetic influence, the heliosphere, and all that falls within its outermost boundary, the heliopause (wherever that is.) Objects farther out are still gravitationally held by the Sun, such as distant KBOs and Oort Cloud comets, but orbit within the interstellar medium.
Fly along with NASA's Voyager spacecraft as the twin probes head towards interstellar space. In this artist's concept, a regularly updated gauge using data from the two spacecraft will indicate the levels of particles that originate from far outside our solar system and those that originate from inside our solar bubble. Those are two of the three signs scientists expect to see in interstellar space. The other sign is a change in the direction of the magnetic field. Image credit: NASA/JPL-Caltech
Far away, deep in the dark, near the edge of interstellar space, Voyager 1 and 2 are hurtling near the tenuous edge of the magnetic bubble surrounding the Sun known as the heliosphere and NASA wants you to ride along.
The Voyager website sports a new feature showing cosmic ray data. NASA’s Eyes on the Solar System, a popular Web-based interactive tool, contains a new Voyager module, that not only lets you ride along for the Voyagers’ journeys but also shows important scientific data flowing from the spacecraft.
[Warning:Play with this tool at your own risk. Interacting with this online feature can seriously impact your time; in an educational way, of course!]
As Voyager 1 explores the outer limits of the heliosphere, where the breath from our Sun is just a whisper, scientists are looking for three key signs that the spacecraft has left our solar system and entered interstellar space, or the space between stars. Voyager 1 began heading for the outer Solar System after zipping through the Saturn system in 1980.
The new module contains three gauges, updated every six hours from real data from Voyager 1 and 2, that indicate the level of fast-moving particles, slower-moving particles and the direction of the magnetic field. Fast-moving charged particles, mainly protons, come from distant stars and originate from outside the heliosphere. Slower-moving particles, also mainly protons, come from within the heliosphere. Scientists are looking for the levels of outside particles to jump dramatically while inside particles dip. If these levels hold steady, it means the Voyager spacecraft no longer feel the wind from our Sun and the gulf between stars awaits.
Over the past couple of years, data from Voyager 1, the most distant man-made object, show a steady increase of high-powered cosmic radiation indicating the edge is near, scientists say. Voyager 1 appears to have reached the last region before interstellar space. Scientists dubbed the region the “magnetic highway.” Particles from outside are streaming in while particles from inside are streaming out. Voyager 2’s instruments detect slight drops in inside particles but scientists don’t think the probe has entered the area yet.
Scientists also expect a change in the direction of the magnetic field. While particle data is updated every six hours, analyses of the magnetic field data usually takes a few months to prepare.
A snapshot riding along with Voyager 1’s looking back at the Sun and inner solar system. The positions of Voyager 2 and Pioneers 10 and 11 show within the viewport as well.
Although launched first, Voyager 2 lags behind its twin Voyager 1 by more than 20 times the distance between the Earth and the Sun. Voyager 2 blasted off August 20, 1977 aboard a Titan-Centaur rocket from Cape Canaveral, Florida. The nuclear-powered craft visited Jupiter and Saturn with an additional mission, called the Grand Tour, to study Uranus and Neptune. Voyager 1 launched two weeks later on September 5, 1977. With a faster flight path, Voyager 1 arrived at Jupiter four months before its sister craft. Voyager 1 went on to study Saturn before using the ringed planet’s gravity field to slingshot it up and out of the plane of the solar system toward the constellation Ophiuchus, the Serpent Bearer.
NASA’s Eyes on the Solar System allows viewers to hitch a ride with any of NASA’s spacecraft as they explore the solar system. Time can be slowed for a near approach of a moon or asteroid or sped up to coast between the planets. Watch close at just the right moment and you can witness one of the spacecrafts roll maneuvers. All spacecraft movements are based on actual spacecraft navigation data.
