This Week in Space: Shock Waves and Solar Flares

Welcome to This Week in Space for the second week of October. We’ve got exciting new discoveries from the JWST, ripples in the heliopause, a new solar observatory from China, and an absolutely-guaranteed-100-percent-can’t-possibly-miss launch date for NASA’s SLS Artemis 1 launch. Plus, this week NASA confirmed that its DART asteroid redirection test was, quite literally, a smashing success.

NASA Now Targeting November for Artemis 1 launch

After several setbacks, NASA is targeting a new launch window for the Artemis 1 inaugural flight. If all goes well, the rocket will launch at 12:07 AM on Nov. 14.

In a blog post, the agency said, “Inspections and analyses over the previous week have confirmed minimal work is required to prepare the rocket and spacecraft to roll out to Launch Pad 39B at Kennedy Space Center in Florida following the roll-back due to Hurricane Ian.” Once the Artemis team puts the rocket’s fuel tank insulation to rights, the agency will roll the SLS and Orion back to the launchpad, while pursuing flight clearance for the launch window.

JWST Spies Concentric Rings

This week, a team of astronomers published some stunning images from the James Webb Space Telescope that solve a 16-year-old mystery.

At its heart lies an ultra-rare celestial entity, a pair of stars known as a colliding wind binary. One is a Wolf-Rayet star named WR-140. Wolf-Rayet stars are a type of extra-intense star burning very hot and very bright at the end of its very long life. The other is a blue O-type supergiant, itself a rarity. The two stars whip around one another in an elliptical, eight-year orbit.

The pair lies about 5,600 light-years away from Earth. From the ground, it falls within the constellation of Cygnus.

A ‘Ferocious Radiation Field’

Webb’s IR observations of this binary pair explain sixteen years of visible-spectrum observations from the Keck Observatory atop Mauna Loa. Astronomers have seen this kind of structure before — enough to know that normally, these would be concentric spherical shells. But in the vacuum of space, starlight is enough to sculpt its surroundings. Because photons can impart momentum, a star’s radiative pressure is enough to shove things around nearby. In fact, this is the idea behind solar sails. Astronomers observing this binary pair found that the stellar wind from each star in the binary pair sweeps out a spiraling path. Where the stars’ heliopauses meet, the luminous shock wave is enough to carve these concentric shells out of the dust and debris. The research appeared this week in Nature Astronomy.

“It’s hard to see starlight causing acceleration because the force fades with distance, and other forces quickly take over,” said first author Yinuo Han. “To witness acceleration at the level that it becomes measurable, the material needs to be reasonably close to the star or the source of the radiation pressure needs to be extra strong. WR140 is a binary star whose ferocious radiation field supercharges these effects, placing them within reach of our high-precision data.” When the team accounted for radiative pressure, their models produced the shape we see.

TESS Spacecraft in Safe Mode

If it isn’t one thing, it’s another. The corollary of “it’s five o’clock somewhere” appears to be “it’s always Monday in space.” This week’s spacecraft malfunction is NASA’s Transiting Exoplanet Survey Satellite (TESS). TESS entered into safe mode on Monday, Oct. 10. As of now, the agency says, the spacecraft is in a “stable configuration” that suspends science observations for troubleshooting. Preliminary investigation showed that the TESS flight computer experienced a reset.

TESS hunts exoplanets by watching stars for the telltale dimming of a transiting planet. So far, the satellite has found or confirmed hundreds of exoplanets, with thousands of candidates on its shortlist. Happily, the TESS operations team reported that science data not yet sent to the ground appears to be safely stored on the satellite.

NASA Confirms DART Impact Literally a Smashing Success

It’s official: For the first time, humanity has intentionally altered the motion of a celestial body. NASA’s Double Asteroid Redirection Test ( DART) investigation team announced Tuesday that the spacecraft’s mission was literally a smashing success. DART hit its target at fourteen thousand miles an hour, and when it did, it adjusted Dimorphos’ orbital period by more than half an hour.

Telescopes around the world and in orbit were watching as DART hit Dimorphos, creating a comet-like plume of debris that stretches for tens of thousands of kilometers. The above image came from Hubble, which has been watching how the asteroid’s orbit evolves. Originally Dimorphos orbited Didymos every 11 hours and 55 minutes. Now, NASA confirms, the asteroid’s orbit is shorter by 32 minutes. That’s more than 25 times their original expectation. So, it’s time to put all that data to work.

One key issue is calculating the asteroid’s mass and density. A denser asteroid, more like a rock covered in ice, would carry more embodied kinetic energy into a collision than would a pile of snowballs of the same volume. The DART impact kicked up a ton of debris, which suggests Dimorphos really was more like a “rubble pile” or a “pile of snowballs.”

Next Up: Hera

“DART has given us some fascinating data about both asteroid properties and the effectiveness of a kinetic impactor as a planetary defense technology,” said Nancy Chabot, the DART coordination lead. “The DART team is continuing to work on this rich dataset to fully understand this first planetary defense test of asteroid deflection.” Chabot hails from the Johns Hopkins Applied Physics Laboratory (APL), where DART was built.

In about four years, give or take, we’ll get a chance to check our work. Once it’s close enough, the European Space Agency’s Hera probe will conduct detailed surveys of Dimorphos and Didymos, paying particular attention to DART’s impact crater.

Crew-4 Return on SpaceX Ship Delayed by Florida Weather

Crew-4 has spent almost six months in space — but they’ll still need to wait a little longer before they come home. Storms and high winds off the Florida coast interfered with Crew-4’s Thursday departure. NASA and SpaceX now are targeting no earlier than 11:35 a.m. EDT Friday, Oct. 14, for the agency’s Crew-4 undocking from the International Space Station. Splashdown will be several hours later, just before 5 p.m. EDT.

NASA’s IBEX Spacecraft Detects Ripples in Heliopause

It took several years of confusing telemetry for Voyager project scientists to decide that Voyager 1 had hit termination shock, crossing through the heliopause into interstellar space. One problem: the probe saw the heliopause in a different place than we’d expected to find it. These readings, along with more recent studies, suggest that instead of an “ideal” ellipse, the sun’s bubble of cosmic influence might stretch out behind it like a comet’s tail, wobble like a falling raindrop, or even waver and undulate like a flame in the wind. Now, readings from NASA’s Interstellar Boundary Explorer, IBEX, provide further evidence for these ideas.

A team of astronomers has found huge ripples and undulations in the heliopause, on a scale of tens of astronomical units (AU; 1 AU is the average distance between the Earth and the Sun). Examining data from Voyager 1 and 2, they also found that when the probes went through termination shock, they sent an electromagnetic shock wave right through the heliopause that ended up bouncing off the outside edge, back toward the spacecraft.

China Launches Its Most Advanced Solar Observatory

This week, China’s Academy of Science celebrated the successful launch of the aptly titled Advanced Solar Observatory, or ASO-S for short. Project scientists affectionately call the orbiter by another name, an homage to a figure from Chinese mythology: Kuafu, the probe’s namesake, was a giant who sought to tame the sun. And like its namesake, Kuafu will chase the sun across the sky, face forever turned toward its light.

While China has launched simple solar probes before, Kuafu outdoes them all. The probe launched with a suite of three scientific instruments, including a Lyman-Alpha spectrometer and a coronagraph. Their imaging capabilities will allow us to study the sun’s middle corona, a region we haven’t yet examined in the ultraviolet. Concurrent X-ray observations should also help scientists uncover the deep secrets of solar flares. Solar flares are bursts of intense radiation, and coronal mass ejections (CMEs) are streams of high-energy particles flung into space as the sun’s magnetic field realigns itself. They’re related, but we don’t have a precise enough explanation of how… yet.

China is giving scientists worldwide access to the telescope, and sharing observations ASO-S will make during its expected four-year mission. The satellite will also compare its readings with other solar observatories on the ground and in space, including NASA’s SDO and the Parker Solar Probe.

Speaking of solar probes: ESA’s Solar Orbiter arrived at its most recent close approach to the Sun on Oct. 12 at 19:12 UTC (21:12 CEST). In this short but striking video, you can see what the probe saw on its way in.

These observations are actually taken in the ultraviolet, at 17 nanometers. Light at this wavelength comes from gases of about one million degrees Celsius. Since the ultraviolet band is invisible to the human eye, researchers colorized it according to intensity.

Scientists Discover Warning Signals From Stars About to Explode

We spend a lot of effort studying the physics of the extreme, and the inside of a star about to go supernova sits at the top of that remarkable list. Antares and Betelgeuse are familiar red supergiants; Betelgeuse is a young, brilliant runaway star that we can see with the naked eye as one of Orion’s shoulders.

At just 10 million years old, Betelgeuse is an infant in cosmic terms. The star has fluctuated in brightness over the past several years, for reasons scientists are still working to identify. One explanation is that titanic starquakes on the star’s surface disturbed it enough to create gargantuan “sunspots.” Another is a cloud of dust, drifting just so between us and the star. Regardless, scientists expect that Betelgeuse will explode in a supernova within a hundred thousand years or so. Now, a team of astronomers reports a new way to know in advance when a red supergiant star is about to explode.

The astronomers found that many red supergiants suddenly “blink out” before they collapse in a supernova. Poring over an enormous volume of telescope data, they realized that these dying stars frequently fade to just a few percent of their normal brightness, just before they explode. Most of the time, once a star goes dark, it’s due to explode within just an Earth year or so.

The astronomers found that this rapid dimming happens because the stars suddenly accrete a “cocoon” of dust and debris. But the cocoon appears to envelop these stars within just an Earth year, which is very fast indeed. Further observations will help explain all this, but for now, the team’s report appears in Monthly Notices of the Royal Astronomical Society.

Skywatchers Corner

Space weather has been downright violent of late. We’ve had two different X-class solar flares within two weeks. While flares of this magnitude can knock out satellite services like telecommunications and GPS, they also make for jaw-dropping auroras if you’re close enough to the poles.

As the nights get longer in the Northern Hemisphere, familiar “winter constellations” like Orion come into view well above the horizon. Indeed, Orion shows up with some impressive fanfare. All throughout October and November, the Orionids will scatter shooting stars across the night sky. Their radiant, the point from which they appear to originate, is just over Orion’s shoulder.

There’s a lot going on around Orion right now. This month, Mars is moving eastward in the sky. However, the planet’s arcing path will make it appear to move backward (in “retrograde”), starting just in time for Halloween. Mars traces out the path you see here because Earth, moving faster than the Red Planet, passes it in its orbit.

Meanwhile, Jupiter and Saturn continue to shine brightly in the evening sky. To find them, look to the southeast, shortly after dark.

PSA: Sky Map Apps Exist and They’re Cool

Binoculars or a telescope are useful if you’re stargazing, but you don’t necessarily need them. You can also get a whole portable planetarium: an app on your phone or tablet that shows a richly featured map of the night sky. Then, you can hold your rectangle up to the sky, and see the name of planets, stars, constellations, and more. Whether you prefer iOS or Android, you’ve got options — and some of them are even free.

Stellarium and SkySafari are both available for iOS and Android. Additionally, the iOS app store recently featured a planetarium app called Night Sky, which wfoojjaec can confirm looks really cool on an iPad. All three apps are free, with various $10-or-less paid “plus” or “pro” subscription features for power users.

Keep your eyes on the sky, and we’ll see you here next week.

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