Precise measurements of Cassini’s final trajectory have now allowed scientists to make the first accurate estimate of the amount of material in the planet’s rings, weighing them based on the strength of their gravitational pull.
That estimate about 40 percent of the mass of Saturn’s moon Mimas, which itself is 2,000 times smaller than Earth’s moon tells them that the rings are relatively recent, having originated less than 100 million years ago and perhaps as recently as 10 million years ago.
Their young age puts to rest a long-running argument among planetary scientists.
Some thought that the rings formed along with the planet 4.5 billion years ago from icy debris remaining in orbit after the formation of the solar system.
Others thought the rings were very young and that Saturn had, at some point, captured an object from the Kuiper belt or a comet and gradually reduced it to orbiting rubble.
The new mass estimate is based on a measurement of how much the flight path of Cassini was deflected by the gravity of the rings when the spacecraft flew between the planet and the rings on its final set of orbits in September 2017.
Initially, however, the deflection did not match predictions based on models of the planet and rings.
Only when the team accounted for very deep flowing winds in atmosphere on Saturn, something impossible to observe from space, did the measurements make sense, allowing them to calculate the mass of the rings.
They also calculated that the surface clouds at Saturn’s equator rotate 4 percent faster than the layer 9,000 kilometers (about 6,000 miles) deep.
That deeper layer takes 9 minutes longer to rotate than do the cloud tops at the equator, which go around the planet once every 10 hours, 33 minutes.
Militzer also was able to calculate that the rocky core of the planet must be between 15 and 18 times the mass of Earth, which is similar to earlier estimates.
The team, led by Luciano Iess at the Sapienza University of Rome, Italy, reported their results today in the journal Science.
NASA’s New Horizons’ team released the first close-up images from Ultima Thule on Wednesday afternoon.
Even at the speed of light, signals from the outer solar system take a long time to reach Earth; however, the pictures were well worth the wait.
They reveal Ultima Thule is actually two objects stuck together. That’s prompted them to dub the big lobe “Ultima” and the small one “Thule.”
And while the first images may still be a bit disappointing, the best pictures will be arriving in the days and weeks ahead.
“We have far less than one percent of the data that’s stored on [New Horizons],” spacecraft lead Alan Stern of the Southwest Research Institute said at a press conference Wednesday.
New Year’s flyby
As billions of people across the world ushered in the new year, the New Horizons spacecraft whizzed by a far-flung space rock named Ultima Thule, making it the most distant object ever visited by humanity.
Traveling at a speed of nearly 9 miles (14.5 kilometers) per second, New Horizons’ didn’t take long to zip past Ultima Thule, which is only about 20 miles (30 km) long and 10 miles (15 km) wide.
During its closest approach at 12:33 a.m. EST on January 1, New Horizons passed within just 2,200 miles (3,500 km) of the mysterious bowling-pin-shaped rock, collecting data all the while.
Within just 10 hours, at 10:28 a.m. EST, the spacecraft successfully “phoned home,” confirming to NASA scientists that it had survived its close encounter with the distant object.
Since New Horizons sent its first post-flyby message, the mission team slowly but surely has been receiving a trickle of data on Ultima Thule (pronounced TOOL-ee, a Latin phrase meaning “a place beyond the known world”), which is located a staggering 4.1 billion miles (6.6 billion km) from Earth.
What we know so far
Ultima Thule is tiny, icy body known as a Kuiper Belt Object (KBO). KBOs are a distinct class of solar system objects that lie far beyond the orbits of Neptune and Pluto.
Although over a thousand KBOs already have been discovered Ultima Thule wasn’t found until 2014.
Because Ultima Thule is so small and distant, it’s very hard for researchers to tease out many of its attributes, even with the most advanced telescopes available today.
But from early on, astronomers figured the small body was likely made of dirty ice and rock.
Early observations of Ultima Thule taken by New Horizons suggested that the rock is rather elongated and shaped somewhat like a bowling pin.
Today’s imagery reveal that the world is actually two objects which were stuck together in a slow cosmic collision.
This might not be one of the most pressing questions in astronomy, but it has been intriguing solar physicists for a while.
We’ve sent many probes to study the Sun at a wide range of latitudes but never actually from above or below, so there’s a gap in our knowledge of our star, which we may now be able to start filling in.
Using data from the Proba-2 (PRoject for OnBoard Autonomy 2) observatory, the European Space Agency (ESA) has managed to create an image of how the north pole of the Sun is likely to look.
So, without directly photographing it, how did they do it?
Proba-2 focuses mainly on the lower latitudes of the Sun but it captures everything in its line of sight, including solar atmospheric effects at high latitudes, which can indirectly help us understand the polar regions.
The team took observations of the Sun, blocking out the solar disk, and leaving only the northernmost part (and a bit on the sides) – as demonstrated by this handy comic strip-style illustration below.
These were converted into information about the atmospheric situation at the time the image was taken.
The process was then repeated several times at later times until there was enough data to cover roughly half of a solar rotation. And from that, they were able to reconstruct the image above.
Such a reconstruction is not certainly a true image – some imprecisions are evident, such as the big line across the middle, which is due to changes to the solar atmosphere as the observations were taking place – but it is the best we can hope for, for now.
Dark and light patches are seen on the surface, indicating that the complexity of our star extends to all latitudes. The dark patch in the middle is a polar coronal hole, the source of a fast solar wind.
The image is from extreme ultraviolet light, so it tracks the energetic processes that give rise to the solar wind, the particles that stream from the Sun out into the Solar System.
The network of structure seen here could alter the solar wind speed.
The NASA/ESA Ulysses mission back in 1994/1995 was the only probe we’ve sent to study the polar regions of the Sun, but It won’t be the last. ESA is planning to send a new mission in 2020.
The Solar Orbiter will study the Sun at high enough latitudes that it will be capable of exploring its polar regions.
This knowledge will be very important in understanding several processes happening on the Sun’s surface and how they impact the space environment around Earth.
In late 2017, scientists with the Event Horizon Telescope – an international collaboration that’s created a virtual Earth-sized telescope, with the goal of capturing the first direct image of a black hole – reported on a the long-awaited shipment of hard disk drives from the South Pole.
They said they were busily analyzing the data on these drives, which is expected to be a key component in giving us the first-ever direct image of a black hole sometime in 2019.
As most of us know, black holes are truly black. That is, they are regions containing so much mass squeezed into so little space – regions of such powerful gravity – that no information or light or anything can escape, even if moving at the fastest speed known to exist in our universe, the speed of light.
Astronomers with the Event Horizon Telescope aren’t aiming to capture the black nothingness of a black hole itself (that’s not possible), but instead a black hole’s event horizon, the sphere-like point-of-no-return surrounding a black hole.
Which black hole then? Naturally, they’ll want to image the black hole that appears biggest from Earth.
The first logical choice is Sagittarius A* – pronounced Sagittarius A-star – a 4-million-solar-mass black hole located at the center of our home galaxy, the Milky Way.
This supermassive black hole is about 27,000 light-years from Earth.
The secondary target of the Event Horizon Telescope is much, much farther away, some 50-60 million light-years from Earth.
It’s the supermassive black hole at the center of M87: the largest galaxy in our home galaxy cluster, the Virgo cluster.
How can it appear big to us, at such a great distance away? It contains over 6 billion solar masses. This black hole is so big it could swallow our solar system whole.
It’s official: astronomers found a new dwarf planet in our solar system — and it’s the most distant object ever observed in our solar system.
“I said ‘far out!’ when I discovered it, and it’s a very far out object,” said astronomer Scott Shepard from the Carnegie Institution for Science.
The tiny planet is called 2018 VG18 — later nicknamed “Farout” by the team that discovered it — and it’s about 3.5 as far away as Pluto, some 18 billion kilometers (11.2 billion miles) away.
That’s more than 100 times the distance between the Earth and the Sun — and about the same distance as Voyager 2, the NASA probe that launched in 1977 and reached interstellar space this month.
Farout was spotted by the Japanese Subaru telescope in Hawaii on November 10 by Shepard and several colleagues, according to a statement on Carnegie Institution for Science’s website.
So far, Farout is still deeply mysterious. But one aspect already attracting scientific interest is its unusual orbit. Farout orbits at an unusual angle, along with other so-called “trans-Neptunian objects.”
There’s been a lot of speculation in recent years about what might be causing those astronomical bodies’ unusual trajectory.
One of the most popular explanations is the possible existence of a ninth planet, or Planet X. In fact, the astronomers discovered Farout while searching for the existence of a ninth planet, according to the statement.
Most recent data suggests it could also be a group of objects within the same gravitational field.
Slow and Pinkish
But we can glean at least some details about Farout. Farout is estimated to be 500 km in diameter, and to take more than 1,000 years to orbit the Sun. It also has a pinkish hue, according to the researchers.
“With new wide-field digital cameras on some of the world’s largest telescopes, we are finally exploring our Solar System’s fringes, far beyond Pluto,” said Chad Trujillo, astronomer from Northern Arizona University.
The discovery shows that even though researchers are now routinely finding planets orbiting other stars, there are still planet-sized undiscovered objects in our own solar system.
It really goes to show how much there still is to learn about our relatively small corner of the galaxy.
The head of Harvard’s department of astronomy thinks that there’s a possibility that a strange object that visited our Solar System from interstellar space may be an alien probe sent from a distant civilization.
He and a colleague outlined their idea in a paper published this week analyzing what the mysterious space object might be, setting off a media frenzy.
But let’s take a breath before we jubilantly cry “aliens.” A single idea about what this object could be doesn’t make it the only explanation, and many scientists still argue that a natural explanation is more plausible.
To add a bit of context, one of the scientists making this “exotic” claim is currently working on an initiative to look for extraterrestrial life in deep space, by sending probes from Earth to other star systems.
The paper that captured everyone’s attention is written by Harvard astrophysicists Avi Loeb and Shmuel Bialy, who tried to describe some weird behavior exhibited by a space rock called `Oumuamua.
Spotted last October, `Oumuamua is a mysterious object that is passing through our Solar System, coming from some unknown deep-space origin.
Objects like this one are thought to pass through our Solar System all the time, but this is the first exo-comet — or a comet from outside our cosmic neighborhood — that we’ve ever detected.
In addition to being a rare find, `Oumuamua is a bit bizarre. Astronomers expected a visitor of this kind to be an icy comet, surrounded by a trail of gas and dust as it passed close to the Sun.
But `Oumuamua seems to lack this kind of cloud, making it look more like an asteroid, which is mostly made of rock and metal. So no one was quite sure what this thing was — a comet, an asteroid, or something totally new.
Then after analyzing `Oumuamua’s orbit, scientists from the European Space Agency noticed that the object was accelerating, more so than it should be if it was just interacting with the gravity of the planets and Sun in our Solar System.
They concluded that `Oumuamua must be a comet; the Sun is likely heating up ice within the object, creating gas that provides an extra boost of speed.
However, Loeb and Bialy are skeptical about this “outgassing” claim, mostly because no one was able to observe gas and dust coming from `Oumuamua.
They also point to recent research from another lab, which is still under review by other scientists, that indicates that if gas were coming from this object, it would change how the rock is rotating — something that hasn’t been observed.
“This rules out the possibility that it’s a comet,” Loeb said.
Of course, the possibility exists. But aliens are a very bold claim to make when natural explanations are still on the table.
“I can understand the excitement, and as a scientist, I can’t sit here and say I have 100 percent evidence this was a natural object,” Fitzsimmons says. “It’s just that all the observations can be matched with a natural object.”
And that could be a problem when we actually do find signs of alien life one day.
Astronomers are finding new planets outside our Solar System all the time, and we’re working on more sophisticated technology to peer into the atmospheres of these worlds.
One day, we may find solid evidence that life exists in deep space, but it may be hard for the public to swallow if they think aliens have already been discovered.
“I don’t want people to think we already saw that when it actually happens,” says Mack. “I want people not to be super cynical about claims about aliens by the time we actually have something that is really solid evidence.”
The most prolific planet-hunting machine in history has signed off.
NASA’s Kepler space telescope, which has discovered 70 percent of the 3,800 confirmed alien worlds to date, has run out of fuel, agency officials announced last October 30.
Kepler can no longer reorient itself to study cosmic objects or beam its data home to Earth, so the legendary instrument’s in-space work is done after nearly a decade.
And that work has been transformative.
“Kepler has taught us that planets are ubiquitous and incredibly diverse,” Kepler project scientist Jessie Dotson, who’s based at NASA’s Ames Research Center in Moffett Field, California said.
“It’s changed how we look at the night sky.”
The announcement was not unexpected. Kepler has been running low on fuel for months, and mission managers put the spacecraft to sleep several times recently to extend its operational life as much as possible.
But the end couldn’t be forestalled forever; Kepler’s tank finally went dry two weeks ago, mission team members said during a telecon with reporters today.
“This marks the end of spacecraft operations for Kepler, and the end of the collection of science data,” Paul Hertz, head of NASA’s Astrophysics Division, said during the telecon.
Not done yet
Even though Kepler has closed its eyes, discoveries from the mission should keep rolling in for years to come.
About 2,900 “candidate” exoplanets detected by the spacecraft still need to be vetted, and most of those should end up being the real deal, Kepler team members have said.
A lot of other data still needs to be analyzed as well, Dotson stressed.
And Kepler will continue to live on in the exoplanet revolution it helped spark.
For example, in April, NASA launched a new spacecraft called the Transiting Exoplanet Survey Satellite (TESS), which is hunting for alien worlds circling stars that lie relatively close to the sun (using the transit method, just like Kepler).
Kepler’s death “is not the end of an era,” Kepler system engineer Charlie Sobeck, also of NASA Ames said. “It’s an occasion to mark, but it’s not an end.”
Anything that comes close to the earth from outer space is known as a near-earth object (NEO).
These include asteroids and comets that may have been pushed out of their normal direction and then begin to head to earth.
While both comets and asteroids are included in this group, there are things that make them quite alike as well as different.
They are believed to be left over material from the beginning of our solar system, over 4 billion years ago.
In the early years of earth’s creation, many hit the earth and if you look at the moon you can still see the craters that are left by the impacts.
Both asteroids and comets played a major role in building our solar system, as we believe that in hitting the planets, they actually became part of the planets.
The difference between them is mainly what they are made of. Comets are made of rock, ice and organic compounds. They are sometimes called ‘dirty snowballs’.
Although they are thought to have originally been made in the farthest sections of the solar system, they travel specific paths due to both planetary and the sun’s gravitational pull.
As a comet nears the heat source of the sun, the ice melts and creates a gas. When traveling, the gas is reflected by the sun and we can sometimes see it from the earth.
The gaseous ‘tail’ can be as long as thousands of miles. Scientists believe that when the earth was first forming, the water that is contained in the comets hit the earth and contributed to developing our oceans.
It’s also believed that this affected the climate and possibly deposited carbon-based molecules that may have helped to start life on the planet.
In ancient times, people thought that seeing a comet could be considered a ‘sign’. Some considered it bad, while other cultures thought it was good.
Asteroids are either made up of rock or rock and some metals, like nickel and iron.
Some asteroids look like one big piece while others are actually clusters of smaller pieces that are being held together with the gravity from the whole asteroid.
There are a small amount of asteroids that are actually burned out comets who lost all of their ice long ago and drift in space.
Almost all of the asteroids originate in the asteroid belt that is between Jupiter and Mars. Jupiter’s massive gravity acts like a kind of guardian, keeping most of the asteroids away from earth.
Asteroids bang and knock into each other in the asteroid belt, and occasionally the force is strong enough to send one spinning into the solar system.
This puts all of the planets at risk from being hit. Some of the smaller asteroids have come close to the earth and break up in the atmosphere. We call these ‘shooting stars’.
There are, however, a lot of larger asteroids in the solar system that could hit earth and do a lot of damage. Thankfully, we have Jupiter to help keep them away.
Want to get away? Want to get far, far away? Voyager 2 has you beat: The spacecraft, launched in 1977, is approaching the edge of the solar system, according to a NASA statement released today (Oct. 5).
That announcement is based on two different instruments on board, which in late August began noticing a small uptick in how many cosmic rays — superfast particles pummeling the solar system from outer space — were hitting the spacecraft.
That matches pretty well with what Voyager 1 began experiencing about three months before its own grand departure in 2012, but scientists can’t be sure of the milestone until after it has been passed.
“We’re seeing a change in the environment around Voyager 2, there’s no doubt about that,” Voyager Project Scientist Ed Stone, a physicist at Caltech, said in the statement.
“We’re going to learn a lot in the coming months, but we still don’t know when we’ll reach the heliopause. We’re not there yet — that’s one thing I can say with confidence.”
The team behind Voyager 2 knows that the spacecraft is currently almost 11 billion miles (17.7 billion kilometers) away from Earth.
But it’s hard to predict when the spacecraft will actually leave the solar system by passing through what scientists call the heliopause.
The heliopause is the bubble around our solar system formed by the solar wind, the rush of charged particles that constantly streams off our sun.
But that solar wind ebbs and flows over the course of the sun’s 11-year cycle, which means that the bubble of our solar system itself expands and contracts.
And because Voyager 2 isn’t following precisely in its predecessor’s steps, scientists aren’t positive that its cosmic exit will result in identical changes to the data that the spacecraft reports.
So until Voyager 2 passes through the heliopause, there’s no way to be sure precisely where it is with regard to the heliopause.
Whenever it does successfully flee the solar system, Voyager 2 will become just the second human-made object to do so.