If lost space rocks warranted missing persons’ reports, the entry for 1995 SN55 would read something like this: “First seen 20 September 1995, gliding across the stars. Last seen a few weeks later. Never recovered.”

It was just
 lost. We know, based on how it moved over a tiny fraction of its orbit, that it probably follows a path taking it closer than Saturn to the sun, then swings out as far as Pluto. We know this orbit lasts about a hundred years.

Based on its brightness, we know that it’s big – maybe 300 kilometres across. That would make 1995 SN55 among the largest, or maybe even the largest, of a class of objects called centaurs. These are intriguing bodies that orbit in an unstable zone of the solar system, where they are tugged on by the monstrous gravity of the gas giant planets.

But we don’t really know anything more about this missing world, first spotted by Nichole Danzl and Arianna Gleason through the Spacewatch telescope on Arizona’s Kitt Peak. This is because the Spacewatch team lost track of it in their survey images after the end of October 1995 – and nobody has found it since.

Given the rigour of modern astronomy, this might seem shocking. An object that could be the biggest of its kind, and we can’t find it? But the truth is that solar system objects are lost all the time.

Lost and found

Let’s rewind a few hundred years. In 1612 and 1613, Galileo saw what he thought was a star. It wasn’t – it was Neptune, which was formally discovered on 24 September 1846, after flickering in and out of human attention for more than two centuries.

Or consider the case of Comet 41P/Tuttle-Giacobini-Kresak, which swings around the sun every 5.4 years. It was first discovered in 1858, then lost but found again in 1907, and then lost again and found a final time in 1951. Today, its name credits each of its three “discoverers”.

The issue is still widespread now, says Spacewatch team member at the University of Arizona in Tucson. In modern terms, “lost” means that astronomers have a better chance of stumbling across these objects in an unrelated survey than of tracking them down from what we know of their orbital paths, she says.

Right now, there are hundreds of lost objects in the Kuiper belt – the frozen wastes of the outer solar system.

More alarmingly, at this very moment there are 135 lost asteroids hanging out near Earth that also fall into the category of “virtual impactors”. This means that based on what we do know of their orbits, there is some – extremely small but not zero – chance that they will hit Earth.

Closing the case file

As for 1995 SN55, one of two things probably happened, says at the Southwest Research Institute in San Antonio, Texas. It could be that noise in some of the Spacewatch images gave a misleading idea of how it was moving, leading future searchers to look in the wrong place.

Or this huge cosmic object might never have existed at all. Something smaller might have brightened temporarily because it erupted or fell apart; or two smaller things could have collided, flashing bright before dimming – and tricking planetary scientists into chasing a ghost.

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Redirecting the flow

On Monday 21 August, the shadow of a solar eclipse will drape itself across the US. If the weather cooperates, scientists and civilians alike, including your Astrophile author, will stand in the darkness and stare up at what remains of the sun: a wispy ring of plasma and arcing magnetic fields called the corona.

And doing so will take us back home.

Symbolically, I mean. For millennia, we’ve been looking up at eclipses and seeing a sliver of plasma. But in recent decades, scientists have started thinking of this halo less as out there in space and more as just here.

That fuzzy ring of seething particles around the sun? We’re in it. It wafts outward, roils, thins, sloughs off as the solar wind and eventually envelops the planets.

“Without this even being hyperbole, we actually live in the outer atmosphere of the sun,” says , a solar physicist at NASA.

Crowning glory

For almost all of human history, glimpses of the corona came only during eclipses.  Among other accounts, the Greek philosopher Plutarch described a hazy light around the rim of a darkened sun as early as AD 71, and Johannes Kepler noticed something similar in 1605.

But it took until the eclipses of 1868 and 1869, when the spectral signatures of atoms in the corona were first discovered, for us to start understanding it as an actual astrophysical place instead of just a shining mirage.

Countless ground and space-based observations later, we know it is made up of hydrogen, helium and a smattering of other elements. Even though the layer underneath it is only a few thousand degrees, parts of the corona simmer at a million degrees or higher.

Magnetic field lines, erupting from a dynamo inside the sun, sculpt the corona into a menagerie of shapes with different names: loops, streamers, empty holes and mass ejections that burp outwards.

In the 1970s, an even bigger picture started to emerge. The space station Skylab found that the ever-changing corona bleeds off into the solar wind, a flow of charged particles that reaches out to Earth and beyond.

Down to Earth

Once here, the particles interact with our planet’s comparatively tiny magnetic field and our atmosphere to make auroras –­ and to disrupt communications satellites.

Trying to grasp this space weather without understanding the corona is like predicting hurricanes without factoring in the ocean, Guhathakurta says.

And at the root of all this tangled physics is the place where the corona starts, right above the sun’s surface – the faint ring made visible during an eclipse.

While space-based observatories can now peer into the sun whenever they want, an eclipse is still the best time to observe the corona to try and figure out how dense and hot it is and what it is made of.

Guhathakurta is lead scientist for this particular eclipse at NASA, and she is a major figure in the modern effort to link the sun, its corona, space weather and Earth. She has been on nine eclipse expeditions already.

Six were successful. “Each of them is glorious,” she says. Three failed. In Mongolia it snowed, South Africa was cloudy and it rained in Indonesia. But an eclipse occurs somewhere in the world every 18 months, so she’s got plenty more chances.

This is my first one. But provided I get to see that sliver of plasma around the sun, I know what I’ll be thinking: This is the corona’s solar system – we’re just living in it.

Screaming bright

Regular readers may have the same expectations of this column as they would a safari: something huge has to show up.

Greedy black holes. Giant lava lakes. Stars too big to exist.  Even the comparatively small stuff in outer space, like asteroids or geologic features on a world’s surface, would effortlessly dwarf you if stood in front of them in a space suit.

But on scale far below the cosmic megafauna is a different world, one of tiny carbon molecules mixing and changing in the void. Its poster child is the charming buckyball, a curious round agglomeration of carbon atoms.

This chemical ecosystem can be a nuisance for astronomers, because the little molecules block out parts of the light we see from stars and galaxies. But it’s also important on its own.

Recent discoveries have shown that the chemical reactions between stars can build the constituents of biological molecules like amino acids and sugars. These substances, raining from space, may have contributed to the origin of life on Earth.

But these reactions are intricate and hard to track, leaving us searching for beacons – a molecule we understand that could help us navigate through the fog. This is where the small stuff becomes a big deal. Hang on as we zoom down.

Spacefaring buckyballs

To envision a buckyball bouncing around in outer space, picture it like a little football: 60 atoms of carbon arranged in a rough sphere.

In the mid 20th century, architect Buckminster Fuller (also known as “Bucky”) and others had figured out that a network of pentagons and hexagons would fold into a stable geodesic structure. As it turned out, nature had already come to the same realisation. In 1985, cooked a disc of graphite, a carbon mineral, in a plasma chamber to recreate the conditions around a red giant star.  To their surprise, they discovered they had made weird new forms of carbon – buckyballs and other examples of even larger molecules that looked like carbon cages.

They chose to nod to Fuller by calling them fullerenes – thankfully – after first considering names like ballene, spherene, soccerene, and carbosoccer.

But, even after astronomers began to look for fullerenes in space, they took two and a half decades to find. It wasn’t until 2010 that a team led by at the University of Western Ontario in Canada found their spectral signatures in the colorful gas around a dying star.

Since then, traces of fullerenes have popped up again and again in many different environments. that their presence in the Milky Way may even explain weird spectral features of interstellar space – certain wavelengths of light from distant stars that are being mysteriously absorbed on the way to us. These features have been unexplained for over a century.

Chemistry in the void

That’s not to say we understand where the fullerenes are coming from.

There is plenty of carbon in space, and a heated carbon-rich gas will produce buckyballs and similar molecules because their closed cages are incredibly stable and resilient. But colder regions of space should instead make flat, soda-ring structures of carbon, with hydrogen atoms around the outside. To get those structures to fold into a cage, you would need to get rid of the hydrogen. This could happen either because there were no hydrogens around to begin with, or if the molecules were exposed to ultraviolet light that can bake the hydrogens away.

How these processes interact to explain the full spread of interstellar fullerenes is unclear, Cami said at . “I’ve been scratching my head about this for a long time.”

Tiny tracers

Solving the mystery of this little molecule could have a big payoff. Most of our spectral measurements of carbon molecules floating around in space are a garbled mess. Too many different kinds of other molecules are overlapping, making it hard to understand what’s going on.

Enter fullerenes, with their clear and unique signals, showing us at least one part of the rhythms and reactions of interstellar carbon. Eventually, perhaps, we can use them as tracers to understand how prebiotic molecules form in space, giving us hints about our own existence.

Like soil bacteria in the savannah, buckyballs might not be as eye catching as the astronomical titans that tower over them. But try taking them and their relatives away and we might not be here to appreciate the cosmos in the first place.

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Blobs faster than light?

One among many

SOME things that go bump in the night can only be seen with heat vision. SPRITEs, a new class of astronomical explosion, may be showing us never-before-seen phases in the lives and deaths of stars.

SPRITEs, short for “eSPecially Red Intermediate-luminosity Transient Events”, are undetectable in visible light. They were spotted only when at the California Institute of Technology in Pasadena and her team began monitoring 190 nearby galaxies with the infrared .

In the first year, there were 14 odd flashes brighter than novae but fainter than supernovae. Strangely, these events were invisible to optical observatories like the Hubble or Keck telescopes.

“The question is, what the heck did we just find?” Kasliwal says. There could be more than one answer to that.

The event we know the most about is called 14ajc. Its source appears to be a glowing cloud of warm molecular hydrogen, in the spiral galaxy Messier 83.

This might be what a star-forming nebula looks like after two young stars, each of about 10 solar masses, brush past each other or collide. That interaction would set off a shock wave through nearby interstellar gas, heating the nebula to produce the infrared glow (The Astrophysical Journal, ).

But many of the SPRITEs have brightened and then faded more quickly than 14ajc. “I do believe that other events are not the same beast, because they just look different,” Kasliwal says.

Another possible source ofSPRITEs could be failed supernovae, says . In these events, a massive star collapses on to its hardened core, but there is no shock wave reverberating outwards and tearing the star apart, as in a supernova. Instead, the core crumples into a black hole and the explosion fizzles, leaving only a small outburst at the star’s outer layers.

It may take some time to differentiate between all the options, given that there are just a few observations with the Spitzer telescope. “They have found something interesting, but the available data is so sparse that it is difficult to come up with great hypotheses,” says Chris Kochanek at the Ohio State University in Columbus.

That’s something Kasliwal hopes to address. “How do we make this into an industry, from a cottage industry?” she says.

Since Kasliwal started looking in 2014, Spitzer has uncovered a total of 59 SPRITEs. Kasliwal has shared data about the most interesting ones online in real time, and is organising a workshop in September to study them further. She is also working on a new infrared detector to look for more. The James Webb Space Telescope should also help find answers when it launches in 2018.

“The observers are way ahead of us theorists,” Woosely says. “They are discovering things much faster than we can model or explain them.”

This article appeared in print under the headline “Infrared flare-ups reveal new events in stars’ lives”

A leaky moon

Lingering mysteries