Is there or isn’t there a Planet 9? Is there a planet way out on the outskirts of our Solar System, with sufficient mass to explain the movements of distant objects? Or is a disc of icy material responsible? There’s no direct evidence yet of an actual Planet 9, but something with sufficient mass is affecting the orbits of distant Solar System objects.
A new study suggests that a disc of icy material causes the strange movements of outer Solar System objects, and that we don’t need to invent another planet to explain those movements. The study comes from Professor Jihad Touma, from the American University of Beirut, and Antranik Sefilian, a PhD student in Cambridge’s Department of Applied Mathematics and Theoretical Physics. Their results are published in the Astronomical Journal.
In July of 2015, NASA’s New Horizons mission made history when it became the first spacecraft to conduct a flyby of Pluto. Since that time, the spacecraft’s mission was extended so it could make its way farther into the outer Solar System and become the first spacecraft to explore some Kuiper Belt Objects (KBOs). It’s first objective will be the KBO known as 2014 MU69, which was recently given the nickname “Ultima Thule” (“ultima thoo-lee”).
In July of 2015, NASA’s New Horizons mission made history when it became the first spacecraft to conduct a flyby of Pluto. Since that time, the spacecraft’s mission was extended so it could make its way farther into the outer Solar System and explore some Kuiper Belt Objects (KBOs). Another historic first, the spacecraft will study these ancient objects in the hopes of learning more about the formation and evolution of the Solar System.
By Jan. 1st, 2019, it will have arrived at its first destination, the KBO known as 2014 MU69. And with the help of the public, this object recently received the nickname “Ultima Thule” (“ultima thoo-lee”). This object, which orbits our Sun at a distance of about 1.6 billion km (1 billion miles) beyond Pluto, will be the most primitive object ever observed by a spacecraft. It will also be the farthest encounter ever achieved in the history of space exploration.
In 2015, MU69 was identified as one of two potential destinations for the New Horizons mission and was recommended to NASA by the mission science team. It was selected because of the immense opportunities for research it presented. As Alan Stern, the Principle Investigator (PI) for the New Horizons mission at the Southwest Research Institute (SwRI), indicated at the time:
“2014 MU69 is a great choice because it is just the kind of ancient KBO, formed where it orbits now, that the Decadal Survey desired us to fly by. Moreover, this KBO costs less fuel to reach [than other candidate targets], leaving more fuel for the flyby, for ancillary science, and greater fuel reserves to protect against the unforeseen.”
Originally, the KBO was thought to be a spherical chunk of ice and rock. However, in August of 2017, new occultation observations made by telescopes in Argentina led the team to conclude that MU69 could actually be a large object with a chunk taken out of it (an “extreme prolate spheroid”). Alternately, they suspected that it might be two objects orbiting very closely together or touching – aka. a close or contact binary.
Given the significance of New Horizons‘ impending encounter with this object, its only proper that it receive a an actual name. In medieval literature and cartography, Thule was a mythical, far-northern island. Ultima Thule means “beyond Thule”, which essentially means that which lies beyond the borders of the known world. This name is highly appropriate, since the exploration of a KBO is something that has never been done before.
As Alan Stern, the principal investigator of the New Horizons mission at the Southwest Research Institute, said in a recent NASA press release:
“MU69 is humanity’s next Ultima Thule. Our spacecraft is heading beyond the limits of the known worlds, to what will be this mission’s next achievement. Since this will be the farthest exploration of any object in space in history, I like to call our flyby target Ultima, for short, symbolizing this ultimate exploration by NASA and our team.”
The campaign to name this object was launched by NASA and the New Horizons team in early November, and was hosted by the SETI Institute and led by Mark Showalter – an institute fellow and member of the New Horizons science team. The campaign involved 115,000 participants from around the world who nominated 34,000 names – 37 of which were selected for a final ballot based on their popularity.
These included eight names suggested by the New Horizons team and 29 nominated by the public. The team then narrowed its selection to the 29 publicly-nominated names and gave preference to names near the top of the polls. Along with Ultima Thule, other names that were considered included Abeona, Pharos, Pangu, Rubicon, Olympus, Pinnacle and Tiramisu.
After a five-day extension was granted to accommodate more voting, the campaign wrapped up on Dec. 6th, 2017. Ultima Thule received about 40 nominations from the public and was among those that got the most votes. “We are grateful to those who proposed such an interesting and inspirational nickname,” Showalter said. “They deserve credit for capturing the true spirit of exploration that New Horizons embodies.”
This name, however, is not a permanent one, but a working one which reflects the fact that MU69 is beyond Pluto – once held to be the most distant planet of the Solar System. Once the flyby is complete, NASA and the New Horizons team will submit a formal name to the International Astronomical Union (IAU). The name will depend on whether or not MU69 is a single body, a binary pair, or multiple objects.
Since that time, New Horizons has carried on to the Kuiper Belt for the sake of conducting more historic encounters. In preparation for these, the probe also established new records when it used its Long Range Reconnaissance Imager (LORRI) to take a series of long-distance pictures. These images, which have since been released to the public, have set the new record for the most distant images ever taken.
At present, the New Horizons probe is at a distance of 6.12 billion km (3.79 billion mi) from Earth. This means that images taken at this point are at a distance of 40.9 Astronomical Units (AUs), or the equivalent of about 41 times the distance between Earth and the Sun. This it slightly farther than the “Pale Blue Dot” image of Earth, which was snapped by the Voyager 1 mission when it was at a distance of 6.06 billion km (3.75 billion mi; 40.5 AU) from Earth.
This historic picture was taken on February 14th, 1990 (Valentine’s Day) at the behest of famed astronomer Carl Sagan. At the time, Sagan was a member of the Voyager imaging team, and he recommended that Voyager 1 take the opportunity to look back at Earth one more time before making its way to the very edge of the Solar System. For more than 27 years, this long-distance record remained unchallenged.
However, in December of 2017, the New Horizons team began conducting a routine calibration test of the LORRI instrument. This consisted of snapping pictures of the “Wishing Well” cluster (aka. the “Football Cluster” or NGC 3532), an open galactic star cluster that is located about 1321 light years from Earth in the direction of the southern constellation of Carina.
This image (shown above) was rather significant, given that this star cluster was the first target ever observed by the Hubble Space Telescope (on May 20th, 1990). While this image broke the long-distance record established by Voyager 1, the probe then turned its LORRI instrument towards objects in its flight path. As part of the probes mission to rendezvous with a KBO, the team was searching for forward-scattering rings or dust.
As a result, just two hours after it had taken the record-breaking image of the “Wishing Well” star cluster, the probe snapped pictures of the Kuiper Belt Objects (KBOs) known as 2012 HZ84 and 2012 HE85 (seen below, left and right). These images once again broke the record for being the most distant images taken from Earth (again), but also set a new record for the closest-ever images ever taken of KBOs.
“New Horizons has long been a mission of firsts — first to explore Pluto, first to explore the Kuiper Belt, fastest spacecraft ever launched. And now, we’ve been able to make images farther from Earth than any spacecraft in history.”
As one of only five spacecraft to travel beyond the Outer Planets, New Horizons has set a number of other distance records as well. These include the most-distant course-correction maneuver, which took place on Dec. 9th, 2017, and guided the spacecraft towards its planned flyby with the KBO 2014 MU69. This event, which will happen on Jan. 1st, 2019, will be the farthest planetary encounter in history.
In the course of its extended mission in the Kuiper Belt, the New Horizons team seeks to observe at least two-dozen other KBOs, dwarf planets and “Centaurs” – i.e. former KBOs that have unstable orbits that cause them to cross the orbit of the gas giants. At present, the New Horizons spacecraft is in hibernation and will be brought back online on June 4th, – when it will begin a series of checks to make sure it is ready for its planned encounter with MU69.
The spacecraft is also conducting nearly continuous measurements of the Kuiper Belt itself to learn more about its plasma, dust and neutral-gas environment. These efforts could reveal much about the formation and evolution of the Solar System, and are setting records that are not likely to be broken for many more decades!
Discovered in 1930 by Clyde Tombaugh, Pluto was once thought to be the ninth and outermost planet of the Solar System. However, due to the formal definition adopted in 2006 at the 26th General Assembly of the International Astronomical Union (IAU), Pluto ceased being the ninth planet of the Solar System and has become alternately known as a “Dwarf Planet”, “Plutiod”, Trans-Neptunian Object (TNO) and Kuiper Belt Object (KBO).
Despite this change of designation, Pluto remains one of the most fascinating celestial bodies known to astronomers. In addition to having a very distant orbit around the Sun (and hence a very long orbital period) it also has the most eccentric orbit of any planet or minor planet in the Solar System. This makes for a rather long year on Pluto, which lasts the equivalent of 248 Earth years!
With an extreme eccentricity of 0.2488, Pluto’s distance from the Sun ranges from 4,436,820,000 km (2,756,912,133 mi) at perihelion to 7,375,930,000 km (4,583,190,418 mi) at aphelion. Meanwhile, it’s average distance (semi-major axis) from the Sun is 5,906,380,000 km (3,670,054,382 mi). Another way to look at it would be to say that it orbits the Sun at an average distance of 39.48 AU, ranging from 29.658 to 49.305 AU.
At its closest, Pluto actually crosses Neptune’s orbit and gets closer to the Sun. This orbital pattern takes place once every 500 years, after which the two objects then return to their initial positions and the cycle repeats. Their orbits also place them in a 2:3 mean-motion resonance, which means that for every two orbits Pluto makes around the Sun, Neptune makes three.
The 2:3 resonance between the two bodies is highly stable, and is preserved over millions of years. The last time this cycle took place was between 1979 to 1999, when Neptune was farther from the Sun than Pluto. Pluto reached perihelion in this cycle – i.e. its closest point to the Sun – on September 5th, 1989. Since 1999, Pluto returned to a position beyond that of Neptune, where it will remain for the following 228 years – i.e. until the year 2227.
Sidereal and Solar Day:
Much like the other bodies in our Solar System, Pluto also rotates on its axis. The time it takes for it to complete a single rotation on its axis is known as a “Sidereal Day”, while the amount of time it takes for the Sun to reach the same point in the sky is known as a “Solar Day”. But due to Pluto’s very long orbital period, a sidereal day and a solar day on Pluto are about the same – 6.4 Earth days (or 6 days, 9 hours, and 36 minutes).
It is also worth noting that Pluto and Charon (its largest moon) are actually more akin to a binary system rather than a planet-moon system. This means that the two worlds orbit each other, and that Charon is tidally locked around Pluto. In other words, Charon takes 6 days and 9 hours to orbit around Pluto – the same amount of time it takes for a day on Pluto. This also means that Charon is always in the same place in the sky when seen from Pluto.
In short, a single day on Pluto lasts the equivalent of about six and a half Earth days. A year on Pluto, meanwhile, lasts the equivalent of 248 Earth years, or 90,560 Earth days! And for the entire year, the moon is hanging overhead and looming large in the sky. But factor in Pluto’s axial tilt, and you will come to see just how odd an average year on Pluto is.
It has been estimated that for someone standing on the surface of Pluto, the Sun would appear about 1,000 times dimmer than it appears from Earth. So while the Sun would still be the brightest object in the sky, it would look more like a very bright star that a big yellow disk. But despite being very far from the Sun at any given time, Pluto’s eccentric orbit still results in some considerable seasonal variations.
On the whole, the surface temperature of Pluto does not change much. It’s surface temperatures are estimated to range from a low of 33 K (-240 °C; -400 °F ) to a high of 55 K (-218 °C; -360°F) – averaging at around 44 K (-229 °C; -380 °F). However, the amount of sunlight each side receives during the course of a year is vastly different.
Compared to most of the planets and their moons, the Pluto-Charon system is oriented perpendicular to its orbit. Much like Uranus, Pluto’s very high axial tilt (122 degrees) essentially means that it is orbiting on its side relative to its orbital plane. This means that at a solstice, one-quarter of Pluto’s surface experiences continuous daylight while the other experiences continuous darkness.
This is similar to what happens in the Arctic Circle, where the summer solstice is characterized by perpetual sunlight (i.e. the “Midnight Sun”) and the winter solstice by perpetual night (“Arctic Darkness”). But on Pluto, these phenomena affect nearly the entire planet, and the seasons last for close to a century.
Even if it is no longer considered a planet (though this could still change) Pluto still has some very fascinating quarks, all of which are just as worthy of study as those of the other eight planets. And the time it takes to complete a full year on Pluto, and all the seasonal changes it goes through, certainly rank among the top ten!
The science team leading NASA’s New Horizons mission that unveiled the true nature of Pluto’s long hidden looks during the history making maiden close encounter last July, have published a fresh global map that offers the sharpest and most spectacular glimpse yet of the mysterious, icy world.
The newly updated global Pluto map is comprised of all the highest resolution images transmitted back to Earth thus far and provides the best perspective to date.
Click on the lead image above to enjoy Pluto revealed at its finest thus far. Click on this link to view the highest resolution version.
Prior to the our first ever flyby of the Pluto planetary system barely 8 months ago, the planet was nothing more than a fuzzy blob with very little in the way of identifiable surface features – even in the most powerful telescopic views lovingly obtained from the Hubble Space Telescope (HST).
Dead center in the new map is the mesmerizing heart shaped region informally known as Tombaugh Regio, unveiled in all its glory and dominating the diminutive world.
The panchromatic (black-and-white) global map of Pluto published by the team includes the latest images received as of less than one week ago on April 25.
The images were captured by New Horizons’ high resolution Long Range Reconnaissance Imager (LORRI).
The science team is working on assembling an updated color map.
During its closest approach at approximately 7:49 a.m. EDT (11:49 UTC) on July 14, 2015, the New Horizons spacecraft swoop to within about 12,500 kilometers (nearly 7,750 miles) of Pluto’s surface and about 17,900 miles (28,800 kilometers) from Charon, the largest moon.
The map includes all resolved images of Pluto’s surface acquired in the final week of the approach period ahead of the flyby starting on July 7, and continuing through to the day of closest approach on July 14, 2015 – and transmitted back so far.
The pixel resolutions are easily seen to vary widely across the map as you scan the global map from left to right – depending on which Plutonian hemisphere was closest to the spacecraft during the period of close flyby.
They range from the highest resolution of 770 feet (235 meters), at center, to 18 miles (30 kilometers) at the far left and right edges.
The Charon-facing hemisphere (left and right edges of the map) had a pixel resolution of 18 miles (30 kilometers).
“This non-encounter hemisphere was seen from much greater range and is, therefore, in far less detail,” noted the team.
However the hemisphere facing New Horizons during the spacecraft’s closest approach on July 14, 2015 (map center) had a far higher pixel resolution reaching to 770 feet (235 meters).
Coincidentally and fortuitously the spectacularly diverse terrain of Tombaugh Regio and the Sputnik Planum area of the hearts left ventricle with ice flows and volcanoes, mountains and river channels was in the region facing the camera and sports the highest resolution imagery.
See below a newly released shaded relief map of Sputnik Planum.
“Sputnik Planum – shows that the vast expanse of the icy surface is on average 2 miles (3 kilometers) lower than the surrounding terrain. Angular blocks of water ice along the western edge of Sputnik Planum can be seen “floating” in the bright deposits of softer, denser solid nitrogen,” according to the team.
Even more stunning images and groundbreaking data will continue streaming back from New Horizons until early fall, across over 3 billion miles of interplanetary space.
Thus the global map of Pluto will be periodically updated.
Its taking over a year to receive the full complement of some 50 gigabits of data due to the limited bandwidth available from the transmitter on the piano-shaped probe as it hurtled past Pluto, its largest moon Charon and four smaller moons.
Pluto is the last planet in our solar system to be visited in the initial reconnaissance of planets by spacecraft from Earth since the dawn of the Space Age.
New Horizons remains on target to fly by a second Kuiper Belt Object (KBO) on Jan. 1, 2019 – tentatively named PT1, for Potential Target 1. It is much smaller than Pluto and was recently selected based on images taken by NASA’s Hubble Space Telescope.
Stay tuned here for Ken’s continuing Earth and planetary science and human spaceflight news.
Finding a ninth planet in our Solar System this late in the game would be fascinating. It would also be somewhat of a surprise, considering our observational capabilities. But new evidence, in the form of small perturbations in the orbit of the Cassini probe, points to the existence of an as-yet undetected planet in our solar system.
Back in January, Konstantin Batygin and Mike Brown, two planetary scientists from the California Institute of Technology, presented evidence supporting the existence of a ninth planet. Their paper showed that some Kuiper Belt Objects (KBOs) display unexpected behaviour. It appears that 6 KBOs are affected by their relationship to a large object, but the KBOs in question are too distant from the known gas giants for them to be responsible. They think that a large, distant planet, in the distant reaches of our Solar System, could be responsible for the unexpected orbital clustering of these KBOs.
Now, the Ninth Planet idea is gaining steam, and another team of researchers have presented evidence that small perturbations in the orbit of the Cassini spacecraft are caused by the new planet. Agnès Fienga at the Côte d’Azur Observatory in France, and her colleagues, have been working on a detailed model of the Solar System for over a decade. They plugged the hypothetical orbit and size of Planet Nine into their model, to see if it fit.
Planet Nine is calculated to be about 4 times as large as Earth, and 10 times as massive. It’s orbit takes between 10,000 and 20,000 years. A planet that large can only be hiding in so many places, and those places are a long way from Earth. Fienga found a potential home for Planet Nine, some 600 astronomical units (AU) from here. That much mass at that location could account for the perturbations in Cassini’s orbit.
There’s more good news when it comes to Planet Nine. By happy accident, it’s predicted location in the sky is towards the constellation Cetus, in the southern hemisphere. This means that it is in the view of the Dark Energy Survey, a southern hemisphere project that is studying the acceleration of the universe. The Dark Energy Survey is not designed to search for planetary objects, but it has successfully found at least one icy object.
There are other ways that the existence of Planet Nine could be confirmed. If it’s as large as thought, then it will radiate enough internal heat to be detected by instruments designed to study the Cosmic Microwave Background (CMB). There is also an enormous amount of data from multiple experiments and observations done over the years that might contain an inadvertent clue. But looking through it is an enormous task.
As for Brown and Batygin, who initially proposed the existence of Planet Nine based on the behaviour of KBOs, they are already proposing a more specific hunt for the elusive planet. They have asked for a substantial amount of observing time at the Subaru Telescope on Mauna Kea in Hawaii, in order to examine closely the location that Fienga’s solar system model predicts Planet Nine to be at.
For a more detailed look at Batygin’s and Brown’s work analyzing KBOs, read Matt Williams’ article here.
Neptune is a truly fascinating world. But as it is, there is much that people don’t know about it. Perhaps it is because Neptune is the most distant planet from our Sun, or because so few exploratory missions have ventured that far out into our Solar System. But regardless of the reason, Neptune is a gas (and ice) giant that is full of wonder!
Below, we have compiled a list of 10 interesting facts about this planet. Some of them, you might already know. But others are sure to surprise and maybe even astound you. Enjoy!
The New Horizons spacecraft is already 209,437,000 km (130,138,000 miles) past Pluto (as of Dec. 4, 2015), making it 5,226,950,000 km (3,247,880,000 miles) from Earth. So, yes, it’s way out there. Recently, it took the closest images ever of a distant Kuiper Belt object, setting a record by a factor of at least 15, according to NASA. The team says this image demonstrates the spacecraft’s ability to observe numerous similar bodies over the next several years. Continue reading “New Horizons Takes Closest Image Ever of a Kuiper Belt Object”
In the outer reaches of the Solar System, beyond the orbit of Neptune, lies a region permeated by celestial objects and minor planets. This region is known as the “Kuiper Belt“, and is named in honor of the 20th century astronomer who speculated about the existence of such a disc decades before it was observed. This disc, he reasoned, was the source of the Solar Systems many comets, and the reason there were no large planets beyond Neptune.
Gerard Kuiper is also regarded by many as being the “father of planetary science”. During the 1960s and 70s, he played a crucial role in the development of infrared airborne astronomy, a technology which led to many pivotal discoveries that would have been impossible using ground-based observatories. At the same time, he helped catalog asteroids, surveyed the Moon, Mars and the outer Solar System, and discovered new moons.