The Parker Solar Probe is no stranger to the sun. On January 17, the NASA spacecraft will make its seventh close pass of our star, coming within 14 million kilometers of its scorching surface.
And this time, Parker will have plenty of company. A lucky celestial lineup means that dozens of other observatories will be trained on the sun at the same time. Together, these telescopes will provide unprecedented views of the sun, helping to solve some of the most enduring mysteries of our star.
“This next orbit is really an amazing one,” says mission project scientist Nour Raouafi of the Johns Hopkins Applied Physics Laboratory in Laurel, Md.
Chief among the spacecraft that will join the watch party is newcomer Solar Orbiter, which the European Space Agency launched in February 2020 (SN: 2/9/20). As Parker swings by our star this month, Solar Orbiter will be watching from the other side of the sun.

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“This is partially luck,” solar physicist Timothy Horbury of Imperial College London said  December 10 at a news briefing at the virtual meeting of the American Geophysical Union. “Nobody planned to have Parker Solar Probe and Solar Orbiter operating together; it’s just come out that way.”
Working together, the sungazers will tackle long-standing puzzles: how the sun creates and controls the solar wind, why solar activity changes over time and how to predict powerful solar outbursts.
“I think it genuinely is going to be a revolution,” Horbury said. “We’re all incredibly lucky to be doing this at this moment in time.”
Working in tandem
The Parker Solar Probe launched in 2018 and has already had six close encounters with the sun (SN: 7/5/18). During its nearly seven-year mission, the probe will eventually swing within 6 million kilometers of the sun — less than one-seventh the distance of Mercury from the sun — giving Parker’s heavily shielded instruments a better taste of the plasma and charged particles of the sun’s outer atmosphere, the corona (SN: 7/31/18).
Because Parker gets so close, its cameras cannot take direct pictures of the solar surface. Solar Orbiter, though, will get no closer than 42 million kilometers, letting it take the highest-resolution images of the sun ever. The mission’s official science phase won’t begin until November 2021, but the spacecraft has already snapped images revealing tiny “campfire” flares that might help heat the corona (SN: 7/16/20).
During Parker’s seventh close encounter, which runs January 12–23, Solar Orbiter will observe the sun from a vantage point almost opposite to Parker’s view. Half a dozen other observers will be watching as well, such as ESA’s BepiColombo spacecraft that is on its way to Mercury and NASA’s veteran sunwatcher STEREO-A. Both will flank Parker on either side of the sun. And telescopes on Earth will be watching from a vantage point about 135 million kilometers behind Parker, making a straight line from Earth to the spacecraft to the sun.
When the Parker Solar Probe makes its next close pass of the sun (shown in the black arc in the center of this diagram), a host of other spacecraft and telescopes on Earth will be watching too. This diagram shows the relative positions during the flyby of the sun, Earth, Parker, Solar Orbiter and two other spacecraft, BepiColombo and STEREO-A.JHU-APL
When the Parker Solar Probe makes its next close pass of the sun (shown in the black arc in the center of this diagram), a host of other spacecraft and telescopes on Earth will be watching too. This diagram shows the relative positions during the flyby of the sun, Earth, Parker, Solar Orbiter and two other spacecraft, BepiColombo and STEREO-A.JHU-APL
The situation is similar to Parker’s fourth flyby in January 2020, when nearly 50 observatories watched the sun in tandem with the probe, Raouafi says. Those observations led to a special issue of Astronomy & Astrophysics with more than 40 articles. One of the results was confirming that there is a region around the sun that is free of dust, which was predicted in 1929. “That was amazing,” Raouafi says. “We want to do a campaign that is that good or even better for this run.”
In the wind
At the AGU meeting, researchers presented new results from Parker’s second year of observations. The results deepen the mystery of magnetic kinks called “switchbacks” that Parker observed in the solar wind, a constant stream of charged particles flowing away from the sun (SN: 12/4/19), Raouafi says.
Some observations support the idea that the kinks originate at the base of the corona and are carried past Parker and beyond, like a wave traveling along a jump rope. Others suggest the switchbacks are created by turbulence within the solar wind itself.
Figuring out which idea is correct could help pinpoint how the sun produces the solar wind in the first place. “These [switchbacks] could be the key to explaining how the solar wind is heated and accelerated,” Raouafi said in a talk recorded for AGU.
Meanwhile, Solar Orbiter’s zoomed-in images plus simultaneous measurements of the solar wind may allow scientists to trace the wind’s energetic particles back to their birthplaces on the sun’s surface. Campfire flares — the “nanoflares” spotted by Solar Orbiter — might even explain the switchbacks, Horbury says.
“The goal is to connect tiny transient events like nanoflares to changes in the solar wind,” Horbury said in the news briefing.
Waking up with the sun
Parker and Solar Orbiter couldn’t have arrived at a better time. “The sun has been very quiet, in a deep solar minimum for the last several years,” Horbury said. “But the sun is just beginning to wake up now.”
Both spacecraft have seen solar activity building over the last year. During its sleepy period, the sun displays fewer sunspots and outbursts such as flares and coronal mass ejections, or CMEs. But as it wakes up, those signs of increasing magnetic activity become more common and more energetic.
On November 29, Parker observed the most powerful flare it had seen in the last three years, followed by a CME that ripped past the spacecraft at 1,400 kilometers per second.“We got so much data from that,” Raouafi says. More CMEs should pass Parker when it’s even closer to the sun, which will tell scientists about how these outbursts are launched.
Solar Orbiter caught an outburst too. On April 19, a CME passed the spacecraft about 20 hours before its effects arrived at Earth. With existing spacecraft, observers on Earth get only about 40 minutes warning before a CME arrives.
Solar Orbiter detected a big burst of plasma called a coronal mass ejection in April, almost a day before signs of the eruption reached Earth. Observers on Earth typically get just 40 minutes of warning before such an eruption arrives.ESA
Solar Orbiter detected a big burst of plasma called a coronal mass ejection in April, almost a day before signs of the eruption reached Earth. Observers on Earth typically get just 40 minutes of warning before such an eruption arrives.ESA
“We can see how that CME evolves as it travels away from the sun in a way we’ve never been able to do before,” Horbury said.
Strong CMEs can knock out satellites and power grids, so having as much forewarning as possible is important. A future spacecraft at Solar Orbiter’s distance from the sun could help give that warning.
Looking forward
This orbit is the first time that Parker Solar Probe and Solar Orbiter will watch the sun in tandem, but not the last. “There will be plenty of opportunities like this one,” Raouafi says.
He’s looking forward to one opportunity in particular: the solar eclipse of 2024. On April 8, 2024, a total eclipse will cross North America from Mexico to Newfoundland. Solar scientists plan to make observations from all along the path of totality, similar to how they watched the total eclipse of 2017.
During the eclipse, the Parker Solar Probe will be on its second-closest orbit, between 7 million and 8 million kilometers from the sun. Parker and Solar Orbiter will be “almost on top of each other,” Raouafi says — both spacecraft will be together off to one side of the sun as seen from Earth. Whatever prominences and other shapes in the corona are visible to observers on Earth will be headed right at the spacecraft.
“They will be flying through the structure we will see from Earth during the solar eclipse,” Raouafi says. The combined observations will tell scientists how features on the sun evolve with time.
“I think it is a new era,” Horbury said. “The next few years is going to be a step change in the way we see the sun.” More

The sun’s wispy upper atmosphere, called the corona, is an ever-changing jungle of sizzling plasma. But mapping the strength of the magnetic fields that largely control that behavior has proved elusive. The fields are weak and the brightness of the sun outshines its corona.
Now though, observations taken using a specialized instrument called a coronagraph to block out the sun’s bright disk have allowed solar physicists to measure the speed and intensity of waves rippling through coronal plasma (SN: 3/19/09). “This is the first time we’ve mapped the coronal magnetic field on a large scale,” says Steven Tomczyk, a solar physicist at the High Altitude Observatory in Boulder, Colo., who designed the coronagraph.
In 2017, Tomczyk had been part of a team that took advantage of a total solar eclipse crisscrossing North America to take measurements of the corona’s magnetic field (SN: 8/16/17). He trekked to a mountaintop in Wyoming with a special camera to snap polarized pictures of the corona just as the moon blocked the sun.  (I was there with them, reporting on the team’s efforts to help explain why the corona is so much hotter than the sun’s surface (SN: 8/21/17).) The team observed a tiny slice of the corona to test whether a particular wavelength of light could carry signatures of the corona’s magnetic field. It can (SN: 8/21/18).
But it’s the observations from the coronagraph, made in 2016, that allowed researchers to look at the whole corona all at once. Theorists had shown decades ago that coronal waves’ velocities can be used to infer the strength of the magnetic field. Such waves might also help carry heat from the sun’s surface into the corona (SN: 11/14/19). But no one had measured them across the whole corona before.

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The corona’s magnetic field strength is mostly between 1 and 4 gauss, a few times the strength of the Earth’s magnetic field at the planet’s surface, the researchers report in the Aug. 7 Science.
Making a map is a big step, the team says. But what solar physicists would really like to do is track the corona’s magnetic field continuously, at least once a day.
“The solar magnetic field is evolving all the time,” says solar physicist Zihao Yang of Peking University in Beijing. Sometimes the sun releases magnetic energy explosively, sending bursts of plasma can shooting out into space (SN: 3/7/19). Those ejections can wreak havoc on satellites or power grids when they strike Earth. Continuously monitoring coronal magnetism can help predict those outbursts. “Our work demonstrated that we can use this technique to map the global distribution of coronal magnetic field, but we only showed one map from a single dataset,” Yang says.
Measuring the strength of the corona’s magnetic field is “a really big deal,” says solar physicist Jenna Samra of the Smithsonian Astrophysical Observatory in Cambridge, Mass. “Making global maps of the coronal magnetic field strength … is what’s going to allow us to eventually get better predictions of space weather events,” she says. “This is a really nice step in that direction.”
Tomczyk and colleagues are working on an upgraded version of the coronagraph, called COSMO, for Coronal Solar Magnetism Observatory, that would use the same technique repeatedly with the ultimate goal of predicting the sun’s behavior.
“It’s a milestone to do it,” Tomczyk says. “The goal is to do it regularly, do it all the time.” More

Dark matter just got even more puzzling.
This unidentified stuff, which makes up most of the mass in the cosmos, is invisible but detectable by the way it gravitationally tugs on objects like stars. (SN: 11/25/19). Dark matter’s gravity can also bend light traveling from distant galaxies to Earth — but now some of this mysterious substance appears to be bending light more than it’s supposed to. A surprising number of dark matter clumps in distant clusters of galaxies severely warp background light from other objects, researchers report in the Sept. 11 Science.
This finding suggests that these clumps of dark matter, in which individual galaxies are embedded, are denser than expected. And that could mean one of two things: Either the computer simulations that researchers use to predict galaxy cluster behavior are wrong, or cosmologists’ understanding of dark matter is.
Very high concentrations of dark matter can act like a lens to bend light and drastically alter the appearance of background galaxies as seen from Earth — stretching them into arcs or splitting them into multiple images of the same object on the sky. “It’s totally cool. It’s like a fun house mirror,” says astrophysicist Priyamvada Natarajan of Yale University.

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Judging by computer simulations of galaxy clusters, clumps of dark matter around individual galaxies that are dense enough to cause such dramatic gravitational lensing effects should be rare (SN: 10/4/15). Based on cluster simulations run by Natarajan and colleagues, “we would expect to see 1 [strong lensing] event in every 10 clusters or so,” says study coauthor Massimo Meneghetti, an astrophysicist at the Astrophysics and Space Science Observatory of Bologna in Italy.
But telescope images told a different story. The researchers used observations from the Hubble Space Telescope and the Very Large Telescope in Chile to investigate 11 galaxy clusters from about 2.8 billion to 5.6 billion light-years away. In that set, the team identified 13 cases of severe gravitational lensing by dark matter clumps around individual galaxies. These observations indicate there are more high-density dark matter clumps in real galaxy clusters than in simulated ones, Meneghetti says.
The simulations could be missing some physics that leads dark matter in galaxy clusters to glom tightly together, Natarajan says. “Or … there’s something fundamentally off about our assumptions about the nature of dark matter,” she says, like the notion that gravity is the only attractive force that dark matter feels.
Richard Ellis, a cosmologist at the University College London who was not involved in the work, thinks the crux of the problem is more likely in the computer simulations than in the nature of dark matter. “A cluster of galaxies is a very dangerous place. It’s like the Manhattan of the universe,” he says — busy with galaxies whizzing past one another, colliding and getting torn up. “There’s awful physics that goes into predicting how many of these little lensed things they should find,” Ellis says, so the new result “is intriguing, but my suspicion is that there’s something in the simulations … that isn’t quite right.”
Future observations with the upcoming Euclid space telescope (SN: 11/14/17), the Nancy Grace Roman Space Telescope and Vera C. Rubin Observatory (SN: 1/10/20) could help clear matters up, says Bhuvnesh Jain, an astrophysicist at the University of Pennsylvania who was not involved in the work. “These three telescopes are going to produce extremely large samples of galaxy clusters,” he says. That may lead to a new understanding of the physics in these turbulent environments, and help determine whether unrealistic simulations are to blame for this dark matter mystery. More

The first black hole ever discovered still has a few surprises in store.
New observations of the black hole–star pair called Cygnus X-1 indicate that the black hole weighs about 21 times as much as the sun — nearly 1.5 times heavier than past estimates. The updated mass has astronomers rethinking how some black hole–forming stars evolve. For a star-sized, or stellar, black hole that massive to exist in the Milky Way, its parent star must have shed less mass through stellar winds than expected, researchers report online February 18 in Science.
Knowing how much mass stars lose through stellar winds over their lifetimes is important for understanding how these stars enrich their surroundings with heavy elements. It’s also key to understanding the masses and compositions of those stars when they explode and leave behind black holes.
The updated mass measurement of Cygnus X-1 is “a big change to an old favorite,” says Tana Joseph, an astronomer at the University of Amsterdam not involved in the work. Stephen Hawking famously bet physicist Kip Thorne that the Cygnus X-1 system, discovered in 1964, did not include a black hole — and conceded the wager in 1990, when scientists had broadly accepted that Cygnus X-1 contained the first known black hole in the universe (SN: 4/10/19).

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Astronomers got a new look at Cygnus X-1 using the Very Long Baseline Array, or VLBA. This network of 10 radio dishes stretches across the United States, from Hawaii to the Virgin Islands, collectively forming a continent-sized radio dish. In 2016, the VLBA tracked radio-bright jets of material spewing out of Cygnus X-1’s black hole for six days (the time it took for the black hole and its companion star to orbit each other once). Those observations offered a clear view of how the black hole’s position in space shifted over the course of its orbit. That, in turn, helped researchers refine the estimated distance to Cygnus X-1.
The new observations suggest that Cygnus X-1 is about 7,200 light-years from Earth, rather than the previous estimate of about 6,000 light-years. This implies that the star in Cygnus X-1 is even brighter, and therefore bigger, than astronomers thought. The star weighs about 40.6 suns, the researchers estimate. The black hole must also be more massive in order to explain its gravitational tug on such a massive star. The black hole weighs about 21.2 suns — much heftier than its previously estimated 14.8 solar masses, the scientists say. 
The new mass measurement for Cygnus X-1’s black hole is so big that it challenges astronomers’ understanding of the massive stars that collapse to form black holes, says study coauthor Ilya Mandel, an astrophysicist at Monash University in Melbourne, Australia.
“Sometimes stars are born with quite high masses — there are observations of stars being born with masses of well over 100 solar masses,” Mandel says. But such enormous stars are thought to shed much of their weight through stellar winds before turning into black holes. The bigger the star and the more heavy elements it contains, the stronger its stellar winds. So in heavy element–rich galaxies such as the Milky Way, big stars — no matter their starting mass — are supposed to shrink down to about 15 solar masses before collapsing into black holes.
Cygnus X-1’s 21-solar-mass black hole undermines that idea.
The LIGO and Virgo gravitational wave detectors have discovered black holes weighing tens of solar masses in other galaxies (SN: 1/21/21). But that is probably because LIGO peers at distant galaxies that existed earlier in the universe, Joseph says. Back then, fewer heavy elements existed, so stellar winds were weaker. With the new Cygnus X-1 measurement, “now we have to say, hang on, we’re in a [heavy element]–rich environment compared to the early universe … but we still managed to make this really massive black hole,” she says, “so maybe we’re not losing as much mass through stellar winds as we initially thought.” More

For the first time in almost half a century, scientists are going to get their hands on new moon rocks.
The Chinese space agency’s Chang’e-5 spacecraft, which landed on the moon around 10:15 a.m. EST December 1, will scoop up lunar soil from a never-before-visited region and bring it back to Earth a few weeks later. Those samples could provide details about an era of lunar history not touched upon by previous moon missions.
“We’ve been talking since the Apollo era about going back and collecting more samples from a different region,” says planetary scientist Jessica Barnes of the University of Arizona in Tucson, who works with lunar samples from the American and Soviet Union missions of the 1960s and 1970s. “It’s finally happening.”
Chang’e-5, the latest in a series of missions named for the Chinese moon goddess (SN: 11/11/18), took off from the China National Space Administration’s launch site in the South China Sea on November 23 and landed in volcanic flatlands on the northwest region of the moon’s nearside.

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The lander, equipped with a scoop and a drill, will collect about two kilograms of soil and small rocks, possibly from as deep as two meters below the moon’s surface, says planetary scientist Long Xiao of China University of Geosciences in Wuhan.
The spacecraft has to work fast. With no internal heating mechanism, it has no defenses against the extremely cold lunar night, which can reach –170° Celsius. The entire mission has to fit within one lunar day, about 14 Earth days.
After the lander collects the sample, a small rocket will bring the lander and the sample back to the orbiter perhaps as early as December 3, although the Chinese space agency has not released the official schedule.
Once in orbit, the moon material will be packaged into a return capsule and sent back to Earth. The capsule is expected to land in the Inner Mongolia region by December 17.
The last time new lunar samples were sent back to Earth was 1976, with the end of the Soviet Union’s Luna program. Between those missions and NASA’s Apollo missions, scientists on Earth have about 380 kilograms of moon material to study (SN: 7/15/19). “Perhaps for a long time people thought, been there, done that, when it comes to the moon,” Barnes says.
Two kilograms of new stuff might not sound like much next to what’s already in hand. But Chang’e-5 is returning samples from an entirely unexplored region. The landing site is in the Mons Rümker region in the northwest region of the nearside of the moon. Like the Apollo and Luna landing sites, Rümker is flat. “The engineering consideration is first, to be safe,” Xiao says.

All the Apollo and Luna missions visited ancient volcanic plains, where the rocks are between 3 billion and 4 billion years old. Rümker’s volcanic rocks are much younger, around 1.3 billion to 1.4 billion years old. In the ‘60s, scientists didn’t think the moon was still volcanically active that late. More recent studies from lunar orbit and from telescopes have suggested a more complicated volcanic past.
“With these new samples, we potentially add another pinpoint in our geologic history of the moon,” says Barnes. “We’ll get an idea of, what was the volcanic history like on the moon a billion years ago? That’s something we don’t have access to in the returned samples we already have.”
The Rümker region is also rich in potassium, rare-Earth elements and phosphorous, often called KREEP elements. Those elements were some of the last to crystalize out of the magma ocean that covered the young moon and can help reveal details of how that process happened. It’s an “exotic flavor” of material, says Barnes. “It’s a really different area, geochemically, to the rest of the moon.”
One of the biggest challenges for the mission will be drilling that material. The drill can’t change direction once it’s deployed, so it has to attempt to drill through anything directly below it. If the drill hits a large rock, it could fail. So the Chang’e-5 team is hoping for fine, loose soil, Long says.
Once the sample is back on Earth, it will be stored and cataloged at a curation center in Beijing. Then it will be distributed for scientists to do research.
“You can’t breathe easy on these types of missions until the samples are back and are safe in the curation place where they’re going to be held,” Barnes says.
The Chinese space agency plans to share samples with international scientists. A 2011 congressional rule makes it difficult for U.S. scientists to collaborate directly with China, so it’s unclear who will get to work with the rocks. But the discoveries that the new samples will enable go beyond international borders.
“It doesn’t matter who’s doing it,” says Barnes. “The whole world should be behind this mission and this endeavor. It’s a piece of history.” More