This time space fans we’re looking at the Juno mission to Jupiter, failed supernovas and a wobbly moon!
The New Jupiter
“We knew, going in, that Jupiter would throw us some curves, But now that we are here we are finding that Jupiter can throw the heat, as well as knuckleballs and sliders. There is so much going on here that we didn’t expect that we have had to take a step back and begin to rethink of this as a whole new Jupiter.”
Those words, said by Scott Bolton at the Southwest Research Institute in San Antonio, sum up much of what we’re already hearing about the Juno mission to explore Jupiter. Bolton is the Juno principal investigator, and one of the first people to see incoming data. That data tells the story of a gas giant that’s more complex, more turbulent, and well, lumpier than we’d imagined.
The three instruments turning in many of the unexpected new findings are Juno’s imaging camera, JunoCam, the Microwave Radiometer, or MWR, and the mission’s Magnetometer, which measures the planet’s magnetic field.
JunoCam: Imaging the Skies
The JunoCam is a public-facing instrument; the camera/telescope was primarily intended as a means to maintain public interest. That hasn’t stopped the camera’s 58-degree eye from capturing unexpected images of both of the planet’s poles, where storms the size of the Earth cluster tightly together, swirling and churning against one another.
Mission scientists are currently unsure how these storm groupings formed, or why the two formations aren’t more similar, or even how stable the arrangement is. According to Bolton, “We’re questioning whether this is a dynamic system, and are we seeing just one stage, and over the next year, we’re going to watch it disappear, or is this a stable configuration and these storms are circulating around one another?”
MWR: A Deeper Look
Juno’s MWR is capable of looking deep into the atmosphere, peering hundreds of kilometers through the clouds of ammonia by sampling thermal microwave radiation. And the results it’s returning are already intriguing.
Jupiter’s clouds organize themselves into bands, or belts. These are easily visible, even from Earth—with a telescope, of course! But now the MWR is revealing that the different cloud belts have decidedly different structures. Jupitor’s equatorial belt extends down as far as the instrunent can see, but others shift and turn into a number of different structures, NASA hasn’t detailed what those structures are yet, but more information is expected with the formal publication of data this week.
MAG-LITE
Jupiter has the most powerful magnetic field in the entire solar system. We’ve known that for a while now. Juno’s on-board magnetometer (MAG) is widening some eyes with just how strong that magnetic field is. Computer modeling had predicted a field of roughly 7.766 Gauss, about ten times stronger than any naturally-occuring magnetic field here on Earth. The Juno data, however, indicates that Jupiter’s magnetosphere is far more power than even those models had expected.
The strength of the field isn’t the only surprise, though. Jack Connerney, Juno deputy principal investigator and the lead for the mission’s magnetic field investigation at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, explained, “Already we see that the magnetic field looks lumpy: it is stronger in some places and weaker in others. This uneven distribution suggests that the field might be generated by dynamo action closer to the surface, above the layer of metallic hydrogen. Every flyby we execute gets us closer to determining where and how Jupiter’s dynamo works.”
The MAG observations also seem to indicate that Jupiter’s auroras may work differently than those on Earth, though the specifics still have not yet been released. Auroras—the northern and southern lights—are caused by energetic particles impacting molecules in a planet’s upper atmosphere. On Earth, these charged particles usually come from the Solar Wind. We’ll have to wait to see what Juno’s picking up out there beyond the Asteroid Belt, though.
Running Through The Hose
While the MAG investigation collects data constantly, almost all of the JunoCam and MWR data is collected during a two-hour transit every 53 days. Juno’s polar orbit swings the spacecraft in past Jupiter from north to south, and then back out again to allow data transmission, diagnostics, and of course, gravitational acceleration for the next pass. Downloading the six megabytes of data from each transit can take up to 36 hours. Bolton described the transits as “Every 53 days, we go screaming by Jupiter, get doused by a fire hose of Jovian science, and there is always something new.”
He went on to give a glimpse into what’s up next, a sure crowd-pleaser: “On our next flyby on July 11, we will fly directly over one of the most iconic features in the entire solar system — one that every school kid knows — Jupiter’s Great Red Spot. If anybody is going to get to the bottom of what is going on below those mammoth swirling crimson cloud tops, it’s Juno and her cloud-piercing science instruments.”
Juno launched on Aug. 5, 2011, and entering Jupiter’s orbit on July 4, 2016. The findings from the first data-collection pass, which flew within about 2,600 miles (4,200 kilometers) of Jupiter’s swirling cloud tops on Aug. 27, are being published this week in two papers in the journal Science, as well as 44 papers in Geophysical Research Letters. – NASA
Follow the mission on Facebook and Twitter at: http://www.facebook.com/NASAJuno
ENCELADUS ROLLED OVER?
Cassini is still making discoveries, even in its last days as it finds that Saturn’s intriguing moon Enceladus may have tipped over at some point in the past. Mission scientists have found evidence that the moon’s axial spin, has been altered, possibly due to an impact with a comet or an asteroid.
By looking at the features on the moon, scientists have shown that Enceladus appears to have tipped over from its original axis by about 55 degrees, essentially it has fallen on its side.
“We found a chain of low areas, or basins, that trace a belt across the moon’s surface that we believe are the fossil remnants of an earlier, previous equator and poles,” said Radwan Tajeddine, a Cassini imaging team associate at Cornell University, Ithaca, New York, and lead author of the paper.
Enceladus’ south pole is a geologically active region where the famous tiger stripes are located. Tajeddine and colleagues are thinking that an asteroid may have struck the region in the past when it was closer to the equator.
“The geological activity in this terrain is unlikely to have been initiated by internal processes,” he said. “We think that, in order to drive such a large reorientation of the moon, it’s possible that an impact was behind the formation of this anomalous terrain.”
It was Cassini that discovered the plumes of water vapor and icy particles spraying from the tiger stripe fractures, showing strong evidence evidence of a subsurface ocean which is venting directly into space from this geologically active area.
Its still unknown as to whether an impact is responsible for this geological activity, or when indeed it could have happened, Tajeddine and colleagues think the disruption and formation of the tiger-stripe terrain caused mass to be redistributed, resulting in the moon’s rotation becoming unsteady and wobbly. This would eventually have settled down over time of course in a process known as polar wander.
The polar wander idea helps to explain why Enceladus’ north and south poles today are so contrasting. The south is geologically active active as well as young, while the north has many impact craters and appears much older. Originally the poles would have been far more similar in appearance.
OUT WITH A WHIMPER
A huge star at the end of its life has been caught in its death throes, on its way to becoming a black hole. Several large telescopes, including the Large Binocular Telescope (LBT), and NASA’s Hubble and Spitzer Space Telescopes were then employed to go look for its corpse and found nothing. It had just vanished. Star as large as this one, 25 times the mass of the Sun are supposed to explode in a very visible fashion as supernovas. This one just quietly shuffled off its mortal coil leaving behind a black hole.
A team of astronomers at The Ohio State University watched a star disappear and possibly become a black hole. Instead of becoming a black hole through the expected process of a supernova, the black hole candidate formed through a “failed supernova.”
Credits: NASA’s Goddard Space Flight Center/Katrina Jackson
“Massive fails like this one in a nearby galaxy could explain why astronomers rarely see supernovae from the most massive stars”, said Christopher Kochanek, professor of astronomy at The Ohio State University and the Ohio Eminent Scholar in Observational Cosmology. The percentage of stars who collapse into a black hole without the need for a supernova could be as high as 30%
“The typical view is that a star can form a black hole only after it goes supernova,” Kochanek explained. “If a star can fall short of a supernova and still make a black hole, that would help to explain why we don’t see supernovae from the most massive stars.” Kochanek’s team published their latest results in the Monthly Notices of the Royal Astronomical Society.
Other galaxies on their watch list is NGC 6946, another is the spiral galaxy nicknamed the “Fireworks Galaxy” as it is full of feisty exploding stars, one of which SN 2017eaw, newly discovered on May 14th, is approaching its most luminous. Another star N6946-BH1, seemed to be on the path to going supernova…then vanished. Astronomers did of course check to see if a dust cloud had got in the way so they used the Spitzer telescope. Spitzer operates in the near infrared, and will see through any dust, but nothing was found. As a result, scientists have concluded that the star collapsed into a black hole.
“N6946-BH1 is the only likely failed supernova that we found in the first seven years of our survey. During this period, six normal supernovae have occurred within the galaxies we’ve been monitoring, suggesting that 10 to 30 percent of massive stars die as failed supernovae,” said Scott Adams, who earned his PhD on the project. “This is just the fraction that would explain the very problem that motivated us to start the survey, that is, that there are fewer observed supernovae than should be occurring if all massive stars die that way.”
To study co-author Krzysztof Stanek, the really interesting part of the discovery is the implications it holds for the origins of very massive black holes — the kind that the LIGO experiment detected via gravitational waves. (LIGO is the Laser Interferometer Gravitational-Wave Observatory.)
It doesn’t necessarily make sense, said Stanek, professor of astronomy at Ohio State, that a massive star could undergo a supernova — a process which entails blowing off much of its outer layers — and still have enough mass left over to form a massive black hole on the scale of those that LIGO detected.
“I suspect it’s much easier to make a very massive black hole if there is no supernova,” he concluded.
That’s it for this time space fans, see you soon!
Header image shows Jupiter’s south pole, as seen by NASA’s Juno spacecraft from an altitude of 32,000 miles (52,000 kilometers). The oval features are cyclones, up to 600 miles (1,000 kilometers) in diameter. Multiple images taken with the JunoCam instrument on three separate orbits were combined to show all areas in daylight, enhanced color, and stereographic projection.
Credits: NASA/JPL-Caltech/SwRI/MSSS/Betsy Asher Hall/Gervasio Robles
