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Astronomers Have Discovered an Alien Planet With Three Suns

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To us humans, a single Sun feels completely normal, but our Solar System is actually a weird outlier. Most stars in the Milky Way galaxy have at least one companion star. Now, in a system 1,800 light-years away, astronomers have finally confirmed a gas giant planet orbiting a star in a triple star system.

 

This system, called KOI-5, is located in the constellation of Cygnus, and the exoplanet therein has been confirmed more than a decade after it was first detected by the Kepler planet-hunting space telescope.

In fact, the planet – now known as KOI-5Ab – was the second candidate exoplanet detection made by Kepler when it commenced operations back in 2009. But it fell by the wayside.

“KOI-5Ab got abandoned because it was complicated, and we had thousands of candidates,” said astronomer David Ciardi of NASA’s Exoplanet Science Institute.

“There were easier pickings than KOI-5Ab, and we were learning something new from Kepler every day, so that KOI-5 was mostly forgotten.”

Exoplanet hunters tend to avoid the complexities of multi-star systems; of the over 4,300 exoplanets confirmed to date, fewer than 10 percent belong to multi-star systems, even though such systems dominate the galaxy. As a result, very little is known about the properties of exoplanets in multi-star systems, compared to those that orbit a lone star.

Following Kepler’s detection, Ciardi and other astronomers had used ground-based telescopes such as the Palomar Observatory, the WM Keck Observatory and the Gemini North telescope to study the system. By 2014, they had identified two companion stars, KOI-5B and KOI-5C.

 

This made it extremely difficult to figure out if the dip in starlight observed by Kepler was caused by an exoplanet or something else. The project was popped into the too-hard basket.

In 2018, Kepler’s successor TESS picked up the job. And when TESS looked at Cygnus, it, too, pinged a candidate exoplanet orbiting KOI-5A.

“I thought to myself, ‘I remember this target’,” Ciardi said. “But we still couldn’t determine definitively if the planet was real or if the blip in the data came from another star in the system – it could have been a fourth star.”

He and his team got to work, reanalysing all previous data. In an excellent testament to the abilities of our planet-hunting telescopes, the researchers found that yes, there is indeed an exoplanet in orbit around KOI-5A, at a skewed angle to at least one of the stars in the triple system.

“We don’t know of many planets that exist in triple-star systems, and this one is extra special because its orbit is skewed,” Ciardi said.

What the scientists were able to ascertain is that the planet, KOI-5Ab, is probably a gas giant about half the mass of Saturn and 7 times the size of Earth, on a very close five-day orbit around KOI-5A. KOI-5A and KOI-5B, both around the same mass as the Sun, form a relatively close binary, with an orbital period of about 30 years.

The third star, KOI-5C, orbits the binary at a much larger distance, with a period of about 400 years – a bit larger than Pluto’s 248-year orbit.

koi 5 diagram(Caltech/R. Hurt (IPAC))

So, if you were able to stand on KOI-5Ab, KOI-5A would dominate the sky. KOI-5B would look a lot like the Sun would look from Saturn (Saturn’s on a 29-year solar orbit). And KOI-5C would look like a very bright star.

And the orbit of KOI-5Ab is misaligned with KOI-5B, which is interesting. If all objects had formed from the same swirling disc of material, they should be aligned more or less on the same plane, like the planets of the Solar System around the Sun’s equator. The researchers think that KOI-5B could have gravitationally perturbed the exoplanet’s orbit, kicking it out of alignment while the planet was forming.

 

We’ve seen other evidence that suggests this can happen. A triple star system was revealed last year with a majorly wonky protoplanetary disc. Any planets that form therein will likely end up on pretty weird orbits.

So, while we haven’t confirmed many exoplanets in triple star systems, finding more will help astronomers model these processes and figure out the wild dynamics involved.

“We still have a lot of questions about how and when planets can form in multiple-star systems and how their properties compare to planets in single-star systems,” Ciardi said.

“By studying this system in greater detail, perhaps we can gain insight into how the Universe makes planets.”

The discovery was announced at the 237th meeting of the American Astronomical Society.

 



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Astronomers Have Identified Another Important Aspect of Planets That Could Host Life

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We are, by now, pretty familiar with the concept of the Goldilocks zone. Also known as the habitable zone, it’s the distance from a star at which liquid water can be present on the surface on a planet – not so hot as to be vaporised, nor so cold as to be frozen.

 

These conditions matter because we count liquid water as a vital ingredient for life. But it’s not the only criterion that can help us to assess a planet’s potential habitability; according to new research based on decades of data, there are also Goldilocks stars.

Not all stars, you see, are built alike. Some are extremely hot and bright – such as the very young, blazing blue OB stars. Some are quite low in temperature, like red M-type dwarfs. These could perhaps be a good temperature, but the Goldilocks zone would be very close to the star, and red dwarfs tend to be turbulent, lashing their surrounding space with violent flares.

Our Sun sits between these two extremes, what is known as a yellow dwarf – a G-type main-sequence star. But, although we know life has emerged in the Solar System (we are, after all, living it), not even the Sun is a Goldilocks star.

Nope. According to astronomers at Villanova University, the best stars for life are one step along the Hertzsprung-Russell chart of star types – that is, K-type stars, which are orange stars a little cooler than the Sun, and a little warmer than a red dwarf.

 

“K-dwarf stars are in the ‘sweet spot,’ with properties intermediate between the rarer, more luminous, but shorter-lived solar-type stars (G stars) and the more numerous red dwarf stars (M stars),” explained Villanova astronomer and astrophysicist Edward Guinan.

“The K stars, especially the warmer ones, have the best of all worlds. If you are looking for planets with habitability, the abundance of K stars pump up your chances of finding life.”

Together with a colleague, astronomer Scott Engle of Villanova University, they presented their research at the 235th meeting of the American Astronomical Society back in January 2020.

Let’s be clear here: astronomers are not looking for habitable planets to find a back-up Earth. Even if we did find Earth 2.0, we just don’t have the technology to get us there.

Our quest for Goldilocks planets has more to do with finding out if there is other life out there in the Universe – and, one step further, if there is intelligent life. Is life normal, or is Earth a giant freak? Narrowing down where life is likely to spring up can help us in that search.

 

Guinan, Engle and others have been monitoring a number of stars F to G-type stars in ultraviolet and X-rays over the last 30 years as part of their Sun in Time program, and M-type red dwarfs for 10 years for the Living with a Red Dwarf program.

Both these programs have been helping to assess the impact of X-ray and ultraviolet radiation of the stars in question on the potential habitability of their planets.

Recently, they expanded their research to include similar data collection on K-type stars – what they have called Living with Goldilocks K-dwarfs. And, indeed, these stars do seem to be the most promising for life-supporting conditions.

goldilocks stars(NASA/ESA/Z. Levy/STScI)

Although the habitable zone of K-type stars is smaller, they are much more common than G-type stars, with around 1,000 of them within just 100 light-years of the Solar System. And they have much longer main-sequence lifetimes.

The Sun is around 4.6 billion years old, with a main-sequence lifetime of around 10 billion years. Complex life only emerged on Earth around 500 million years ago, and scientists think that, in another billion years, the planet will become uninhabitable as the Sun begins to expand, pushing the Solar System’s habitable zone outwards.

 

Red dwarfs are more common, but they’re feisty, subjecting the space around them to intense radiation and flare activity that could strip any close planets of their atmospheres and liquid water.

By contrast, K-type stars have lifetimes between 25 and 80 billion years, offering a much bigger window in which life can emerge than G-type stars; according to the team’s data, they are much calmer than red dwarfs, too.

And there are already K-type stars around which planets have been located – namely Kepler-442, Tau Ceti and Epsilon Eridani

“Kepler-442 is noteworthy in that this star (spectral classification, K5) hosts what is considered one of the best Goldilocks planets, Kepler-442b, a rocky planet that is a little more than twice Earth’s mass,” Guinan said

“So the Kepler-442 system is a Goldilocks planet hosted by a Goldilocks star!”

The search for life could, of course, be much more complicated even than this – for example, if the planet has a highly elliptical orbit, it could produce temperature extremes that would render an otherwise Goldilocks planet uninhabitable.

The location of other planets in the system could make a difference too; and there’s a possibility that the entire galaxy has its own habitable zone (if it does, we know we’re in it, so looking nearby is a good start).

But this research could represent a piece of the puzzle that could make the life needle in the space haystack just a little bit easier to find.

The research was presented at the 235th meeting of the American Astronomical Society in Hawaii.

A version of this article was first published in January 2020.

 



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Our Solar System Is Going to Totally Disintegrate Sooner Than We Thought

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Although the ground beneath our feet feels solid and reassuring (most of the time), nothing in this Universe lasts forever.

One day, our Sun will die, ejecting a large proportion of its mass before its core shrinks down into a white dwarf, gradually leaking heat until it’s nothing more than a cold, dark, dead lump of rock, a thousand trillion years later.

 

But the rest of the Solar System will be long gone by then. According to new simulations, it will take just 100 billion years for any remaining planets to skedaddle off across the galaxy, leaving the dying Sun far behind.

Astronomers and physicists have been trying to puzzle out the ultimate fate of the Solar System for at least hundreds of years.

“Understanding the long-term dynamical stability of the solar system constitutes one of the oldest pursuits of astrophysics, tracing back to Newton himself, who speculated that mutual interactions between planets would eventually drive the system unstable,” wrote astronomers Jon Zink of the University of California, Los Angeles, Konstantin Batygin of Caltech and Fred Adams of the University of Michigan in their new paper.

But that’s a lot trickier than it might seem. The greater the number of bodies that are involved in a dynamical system, interacting with each other, the more complicated that system grows and the harder it is to predict. This is called the N-body problem.

Because of this complexity, it’s impossible to make deterministic predictions of the orbits of Solar System objects past certain timescales. Beyond about five to 10 million years, certainty flies right out the window.

 

But, if we can figure out what’s going to happen to our Solar System, that will tell us something about how the Universe might evolve, on timescales far longer than its current age of 13.8 billion years.

In 1999, astronomers predicted that the Solar System would slowly fall apart over a period of at least a billion billion – that’s 10^18, or a quintillion – years. That’s how long it would take, they calculated, for orbital resonances from Jupiter and Saturn to decouple Uranus.

According to Zink’s team, though, this calculation left out some important influences that could disrupt the Solar System sooner.

Firstly, there’s the Sun.

In about 5 billion years, as it dies, the Sun will swell up into a red giant, engulfing Mercury, Venus and Earth. Then it will eject nearly half its mass, blown away into space on stellar winds; the remaining white dwarf will be around just 54 percent of the current solar mass.

This mass loss will loosen the Sun’s gravitational grip on the remaining planets, Mars and the outer gas and ice giants, Jupiter, Saturn, Uranus, and Neptune.

 

Secondly, as the Solar System orbits the galactic centre, other stars ought to come close enough to perturb the planets’ orbits, around once every 23 million years.

“By accounting for stellar mass loss and the inflation of the outer planet orbits, these encounters will become more influential,” the researchers wrote.

“Given enough time, some of these flybys will come close enough to disassociate – or destabilise – the remaining planets.”

With these additional influences accounted for in their calculations, the team ran 10 N-body simulations for the outer planets (leaving out Mars to save on computation costs, since its influence should be negligible), using the powerful Shared Hoffman2 Cluster. These simulations were split into two phases: up to the end of the Sun’s mass loss, and the phase that comes after.

Although 10 simulations isn’t a strong statistical sample, the team found that a similar scenario played out each time.

After the Sun completes its evolution into a white dwarf, the outer planets have a larger orbit, but still remain relatively stable. Jupiter and Saturn, however, become captured in a stable 5:2 resonance – for every five times Jupiter orbits the Sun, Saturn orbits twice (that eventual resonance has been proposed many times, not least by Isaac Newton himself).

 

These expanded orbits, as well as characteristics of the planetary resonance, makes the system more susceptible to perturbations by passing stars.

After 30 billion years, such stellar perturbations jangle those stable orbits into chaotic ones, resulting in rapid planet loss. All but one planet escape their orbits, fleeing off into the galaxy as rogue planets.

That last, lonely planet sticks around for another 50 billion years, but its fate is sealed. Eventually, it, too, is knocked loose by the gravitational influence of passing stars. Ultimately, by 100 billion years after the Sun turns into a white dwarf, the Solar System is no more.

That’s a significantly shorter timeframe than that proposed in 1999. And, the researchers carefully note, it’s contingent on current observations of the local galactic environment, and stellar flyby estimates, both of which may change. So it’s by no means engraved in stone.

Even if estimates of the timeline of the Solar System’s demise do change, however, it’s still many billions of years away. The likelihood of humanity surviving long enough to see it is slim.

Sleep tight!

The research has been published in The Astronomical Journal.

 



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What You Need to Know About That Controversial New Climate ‘Tipping Point’ Study

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Even if humanity stopped emitting greenhouse gases tomorrow, Earth will warm for centuries to come and oceans will rise by metres, according to a controversial modelling study published Thursday.

 

Natural drivers of global warming – more heat-trapping clouds, thawing permafrost, and shrinking sea ice – already set in motion by carbon pollution will take on their own momentum, researchers from Norway reported in the Nature journal Scientific Reports.

“According to our models, humanity is beyond the point-of-no-return when it comes to halting the melting of permafrost using greenhouse gas cuts as the single tool,” lead author Jorgen Randers, a professor emeritus of climate strategy at the BI Norwegian Business School, told AFP.

“If we want to stop this melting process we must do something in addition – for example, suck CO2 out of the atmosphere and store it underground, and make Earth’s surface brighter.”

Using a stripped-down climate model, Randers and colleague Ulrich Goluke projected changes out to the year 2500 under two scenarios: the instant cessation of emissions, and the gradual reduction of planet warming gases to zero by 2100.

In an imaginary world where carbon pollution stops with a flip of the switch, the planet warms over the next 50 years to about 2.3 degrees Celsius above pre-industrial levels – roughly half-a-degree above the target set in the 2015 Paris Agreement – and cools slightly after that.

 

Earth’s surface today is 1.2C hotter than it was in the mid-19th century, when temperatures began to rise.

But starting in 2150, the model has the planet beginning to gradually warm again, with average temperatures climbing another degree over the following 350 years, and sea levels going up by at least three metres.

Under the second scenario, Earth heats up to levels that would tear at the fabric of civilisation far more quickly, but ends up at roughly the same point by 2500.

Tipping points

The core finding – contested by leading climate scientists – is that several thresholds, or “tipping points”, in Earth’s climate system have already been crossed, triggering a self-perpetuating process of warming, as has happened millions of years in the past.

One of these drivers is the rapid retreat of sea ice in the Arctic.

Since the late 20th century, millions of square kilometres of snow and ice – which reflects about 80 percent of the Sun’s radiative force back into space – have been replaced in summer by open ocean, which absorbs the same percentage instead.

 

Another source is the thawing of permafrost, which holds twice as much carbon as there is in the atmosphere. The third is increasing amounts of water vapour, which also has a warming effect.

Reactions from half-a-dozen leading climate scientists to the study – which the authors acknowledge is schematic – varied sharply, with some saying the findings merit follow-up research, and others rejecting it out of hand.

“The model used here is .. not shown to be a credible representation of the real climate system,” said Richard Betts, head of climate impacts research at the University of Exeter.

“In fact, it is directly contradicted by more established and extensively evaluated climate models.”

Mark Maslin, a professor of climatology at University College London, also pointed to shortcomings in the model, known as ESCIMO, describing the study as a “thought experiment.”

“What the study does draw attention to is that reducing global carbon emissions to zero by 2050” – a goal championed by the UN and embraced by a growing number of countries – “is just the start of our actions to deal with climate change.”

Even the more sophisticated models used in the projections of the UN’s scientific advisory body, the IPCC, show that the Paris climate pact temperature goals cannot be reached unless massive amounts of CO2 are removed from the atmosphere.

One way to do that is planting billions of trees. Experimental technologies have shown that sucking CO2 out of the air can be done mechanically, but so far not at the scale required.

© Agence France-Presse

 





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Ancient Meteorite Hints Mars Had Water Before There Was Life on Earth

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We know that Mars was once much wetter than it is now, but the questions of when water formed and evaporated away are much more difficult to answer.

A new study now suggests that water was present on the Red Planet some 4.4 billion years ago, much earlier than previously thought.

 

That’s based on an analysis of a meteorite named NWA 7533, picked up in the Sahara Desert and thought to have originated on Mars billions of years ago. The oxidation of certain minerals inside the meteorite hints at the presence of water.

The findings could push back the estimated date of water formation on Mars some 700 million years, from the 3.7-billion-years-ago timeframe that has been the general consensus up until now. The research could also offer up some insights into how planets form in the first place.

“I study minerals in Martian meteorites to understand how Mars formed and its crust and mantle evolved,” says planetary scientist Takashi Mikouchi from the University of Tokyo in Japan.

“This is the first time I have investigated this particular meteorite, nicknamed ‘Black Beauty’ for its dark colour. Our samples of NWA 7533 were subjected to four different kinds of spectroscopic analysis, ways of detecting chemical fingerprints. The results led our team to draw some exciting conclusions.”

Planetary scientists are keenly interested in the story of water on planets and on moons. One of the big unknowns is whether water gets added to a planetary body after it forms, through the impacts of asteroids and comets, or whether it occurs naturally during the planet formation process.

 

Ancient rocks like NWA 7533 can help scientists peer back in time and find out, as they record impact events on the planet they come from, and capture some of the mineral and chemical composition of the surface when they are formed.

In this case, it’s the oxidation that’s the tell-tale sign of water. With certain fragments inside NWA 7533 dated to 4.4 billion years ago, it’s the oldest record we’ve got of Mars (which may be why a single gram of this meteorite can fetch as much as US$10,000).

“Igneous clasts, or fragmented rock, in the meteorite are formed from magma and are commonly caused by impacts and oxidation,” says Mikouchi. “This oxidation could have occurred if there was water present on or in the Martian crust 4.4 billion years ago during an impact that melted part of the crust.”

Such an early appearance suggests that water actually was around when Mars formed and that in turn plays into research into planetary formation in general. With water comes life, which is one reason scientists are so eager to track it down around the Universe. For comparison, we know that the earliest traces of life on Earth date to at least 3.5 billion years ago.

The close study of Mars continues as experts try and figure out when water was present and what form it might have taken. One recent study put forward the idea that both liquid water and surface ice could have existed on the Red Planet at the same time.

The team’s findings also suggest that the chemical make-up of the Martian atmosphere at this time – including high levels of hydrogen – could have made the planet warm enough for water to melt and life to exist, even though the Sun would have been younger and fainter during this period.

“Our analysis also suggests such an impact would have released a lot of hydrogen, which would have contributed to planetary warming at a time when Mars already had a thick insulating atmosphere of carbon dioxide,” says Mikouchi.

The research has been published in Science Advances.

 



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An Asteroid Trailing After Mars Could Actually Be The Stolen Twin of Our Moon

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A distant asteroid trailing in the gravitational wake of Mars has been observed in greater detail than ever before, and the close-up reveals a surprising resemblance – one that raises some interesting questions about the object’s ancient origins.

 

The asteroid in question, called (101429) 1998 VF31, is part of a group of trojan asteroids sharing the orbit of Mars.

Trojans are celestial bodies that fall into gravitationally balanced regions of space in the vicinity of other planets, located 60 degrees in front of and behind the planet.

Most of the trojan asteroids we know about share Jupiter’s orbit, but other planets have them too, including Mars and Earth too.

What makes (101429) 1998 VF31 (hereafter ‘101429’) interesting is that among the Red Planet’s trailing trojans (the ones that follow behind Mars as it orbits the Sun), 101429 appears to be unique.

010 moon asteroid 2Depiction of Mars and trojans; 101429 is the blue point circling L5. (AOP)

The rest of the group, called the L5 Martian Trojans, all belong to what’s known as the Eureka family, consisting of 5261 Eureka – the first Mars trojan discovered – and a bunch of small fragments believed to have come loose from their parent space rock.

101429 is different, though, and in a new study led by astronomers from the Armagh Observatory and Planetarium (AOP) in Northern Ireland, researchers wanted to examine why.

 

Using a spectrograph called X-SHOOTER on the European Southern Observatory’s 8-m Very Large Telescope (VLT) in Chile, the team examined how sunlight reflects off 101429 and its L5 kin in the Eureka family. Only, it looks like 101429 and the Eureka clan aren’t kin after all, with the analysis revealing 101429 shows a spectral match for a satellite much closer to home.

“The spectrum of this particular asteroid seems to be almost a dead-ringer for parts of the Moon where there is exposed bedrock such as crater interiors and mountains,” explains AOP astrochemist Galin Borisov.

While we can’t be sure yet why that is, the researchers say it’s plausible that this Martian trojan’s origins began somewhere far removed from the Red Planet, with 101429 representing a “relic fragment of the Moon’s original solid crust”.

If that’s true, how did the Moon’s long-lost twin end up as a trojan bound together with Mars?

010 moon asteroid 2Spectral comparison of 101429 and the Moon’s surface. (AOP)

“The early Solar System was very different from the place we see today,” explains lead author of the study, AOP astronomer Apostolos Christou.

“The space between the newly-formed planets was full of debris and collisions were commonplace. Large asteroids [planetesimals] were constantly hitting the Moon and the other planets. A shard from such a collision could have reached the orbit of Mars when the planet was still forming and was trapped in its Trojan clouds.”

 

It’s a captivating idea, but the researchers say it’s not the only explanation for 101429’s past. It’s also possible, and perhaps more likely, that the trojan instead represents a fragment of Mars chipped off by a similar kind of incident impacting the Red Planet; or it might just be a commonplace asteroid that, through the weathering processes of solar radiation, ended up looking just like the Moon.

Further observations with even more powerful spectrographs might be able to shed more light on this question of space parentage, as could a future spacecraft visit, the team says, “which could, en route to the Trojans, obtain spectra at Mars or the Moon for direct comparison with the asteroid data”.

The findings are reported in Icarus.

 



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Astronomers Confirm a Rogue Earth-Sized Planet Careening Through Our Galaxy

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Earth orbits the sun like a ship sailing in circles around its anchor. But what if someone – or something – cut that ship loose?

Unbound from any star or solar system, what would become of a tiny world flying helplessly and heedlessly through interstellar space? What happens when a planet goes rogue?

 

Scientists suspect that billions of free-floating or “rogue” planets may exist in the Milky Way, but so far only a handful of candidates have turned up among the 4,000-or-so worlds discovered beyond our Solar System.

Most of these potential rogue planets appear to be enormous, measuring anywhere from two to 40 times the mass of Jupiter (one Jupiter is equivalent to about 300 Earths). But now, astronomers believe they’ve detected a rogue world like no other: a tiny, free-floating planet, roughly the mass of Earth, gallivanting through the gut of the Milky Way.

This discovery, reported on October 29 in the Astrophysical Journal Letters, may mark the smallest rogue planet ever detected, and it could help prove a long-standing cosmic theory.

According to the study authors, this little world could be the first real evidence that free-floating, Earth-sized planets may be some of the most common objects in the galaxy.

“The odds of detecting such a low-mass object are extremely low,” lead study author Przemek Mroz, a postdoctoral scholar at the California Institute of Technology, told Live Science in an email.

 

“Either we were very lucky, or such objects are very common in the Milky Way. They may be as common as stars.”

Einstein’s magnifying glass

Most exoplanets in our galaxy are visible only because of their host stars. In a literal sense, stars provide the light that allows astronomers to directly observe alien worlds.

When a planet is too small or too distant to be seen directly, scientists can still detect it from the slight gravitational pull it exerts on its host star (called the radial velocity method) or by the flickering that occurs when a planet passes in front of the star’s Earth-facing side (the transit method).

Rogue planets, by definition, have no star to light their way – or to light a telescope’s way to them. Instead, detecting rogue planets involves a facet of Einstein’s theory of general relativity known as gravitational lensing.

Through this phenomenon, a planet (or even more massive object) acts as a cosmic magnifying glass that temporarily bends the light of objects behind it from Earth’s perspective.

“If a massive object passes between an Earth-based observer and a distant source star, its gravity may deflect and focus light from the source,” Mroz explained in a statement. “The observer will measure a short brightening of the source star.”

 

The smaller that light-bending object is, the briefer the star’s perceived brightening will be. While a planet several times the mass of Jupiter might create a brightening effect that lasts a few days, a measly planet the mass of Earth will brighten the source star for only a few hours, or less, the researchers said. This exceptionally rare occurrence is called “microlensing.”

“Chances of observing microlensing are extremely slim,” Mroz added in the statement. “If we observed only one source star, we would have to wait almost a million years to see the source being microlensed.”

Fortunately, Mroz and his colleagues weren’t observing just one star for their study – they were watching hundreds of millions of them. Using observations from the Optical Gravitational Lensing Experiment (OGLE), a star survey based at the University of Warsaw in Poland that has turned up at least 17 exoplanets since 1992, the team stared into the center of the Milky Way, looking for any signs of microlensing.

In June 2016, they witnessed the shortest microlensing event ever seen. The star in question, located roughly 27,000 light-years away in the densest part of the galaxy, brightened for just 42 minutes.

 

Calculations showed that the offending object was not bound to any star within 8 astronomical units (AU, or eight times the average distance from Earth to the Sun), suggesting it was almost certainly a tiny planet on the run, ejected from its home solar system after a brush with a much more massive object.

Depending on how far away the planet is from the source star (it’s impossible to tell with current technology), the rogue world is likely between one-half and one Earth mass. In either case, this roaming world would be the lowest-mass rogue planet ever detected. According to Mroz, that’s a “huge milestone” for the science of planet formation.

“Theories of planet formation have predicted that the majority of free-floating planets should be of Earth mass or smaller, but this is the first time that we could find such a low-mass planet,” Mroz said.

“It’s really amazing that Einstein’s theory allows us to detect a tiny piece of rock floating in the galaxy.”

Many more tiny pieces of rock may soon follow, study co-author Radek Poleski of the University of Warsaw told Live Science.

Future planet-hunting telescopes, like NASA’s Nancy Grace Roman Space Telescope (slated to launch in the mid-2020s), will be much more sensitive to the galaxy’s teensiest microlensing events than the nearly 30-year-old OGLE experiment is, Poleski said. If orphan planets of roughly Earth’s mass are indeed some of the most common denizens of the galaxy, it shouldn’t be long before many more of them turn up.

This article was originally published by Live Science. Read the original article here.

 



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Giant Asteroid Survivor of Failed Planet Discovered to Be Slowly Rusting in Space

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Roughly two to three times Earth’s distance from the Sun, in the Asteroid Belt that lies between Mars and Jupiter, 16 Psyche makes its home. This giant metal asteroid is one of the most massive objects in the Asteroid Belt, categorised as a minor planet.

 

Astronomers think that 16 Psyche is the exposed core of a full planet that didn’t make it all the way, and we’re itching to know more about it. NASA will be sending a probe to check it out in the next few years, and in the meantime, scientists are working to glean what they can from Earth.

Now, for the first time, 16 Psyche has been studied in ultraviolet wavelengths using the Hubble Space Telescope, revealing that, just as we thought, the dense chunk of space rock is remarkably metallic.

“We’ve seen meteorites that are mostly metal, but Psyche could be unique in that it might be an asteroid that is totally made of iron and nickel,” said planetary scientist Tracy Becker of the Southwest Research Institute.

“Earth has a metal core, a mantle and crust. It’s possible that as a Psyche protoplanet was forming, it was struck by another object in our Solar System and lost its mantle and crust.”

16 Psyche is a pretty fascinating chunk of rock. It’s about 226 kilometres (140 miles) across, and just a little less dense than Earth. Its composition seems to consist of somewhere between 30 to 60 percent metal, and the rest low-iron silicate.

 

If 16 Psyche is a protoplanetary core, it’s possible such impacts stripped it of its accumulating material. Planets are thought to form when their stars are very young – possibly even in tandem – and are surrounded by a thick cloud of dust and gas. Material in this cloud starts to stick together, first electrostatically, then gravitationally as the object grows more massive.

As these bodies grow, they become hot and a bit molten, allowing material to move around. Core differentiation is the process whereby denser material sinks inwards towards the centre of the object, and less dense material rises outwards. For 16 Psyche to be a differentiated core, the protoplanet would once have had to have been much bigger than it is now.

Exactly when, and how, its outer mantle was stripped away is a bit of a head-scratcher. But Becker’s team’s research could be the breadcrumbs that put us on the trail to figuring it out.

“We were able to identify for the first time on any asteroid what we think are iron oxide ultraviolet absorption bands,” she said. “This is an indication that oxidation is happening on the asteroid, which could be a result of the solar wind hitting the surface.”

 

In other words, 16 Psyche is rusting. And we might be able to work out how old its surface is based on how much oxidation has occurred – which in turn could give us a timeline of when the asteroid was stripped of its outer material.

The asteroid’s high reflectivity at ultraviolet wavelengths suggests that it’s been a long time; usually, ultraviolet brightness is linked with space weathering. But we won’t know for sure until NASA’s Psyche probe reaches the asteroid sometime around 2026.

Scientists are also keen to get a closer look at 16 Psyche’s composition. There’s a lot of wiggle room between 30 and 60 percent metal that has made it hard to track down smaller pieces of rock that may have resulted from the impact fragmentation of the 16 Psyche’s mantle.

It was once thought that the relatively metallic mesosiderite meteorites were remnants of 16 Psyche, but more recent research has found the connection weak.

The work of Becker and her team revealed a spectrum that is consistent with pure iron, but that may be misleading – as little as 10 percent iron on the surface could dominate the ultraviolet spectrum. There are also very few analogous observations of planetary surfaces in ultraviolet against which to compare the new views of 16 Psyche.

So, we obviously just have to go and check it out with an actual orbiting probe, which in turn will indicate how well we’ve done trying to figure out this strange object from hundreds of millions of kilometres away. Whatever we learn, it’s going to be like looking at a Solar System time capsule. 

“What makes Psyche and the other asteroids so interesting is that they’re considered to be the building blocks of the Solar System,” Becker said.

“To understand what really makes up a planet and to potentially see the inside of a planet is fascinating. Once we get to Psyche, we’re really going to understand if that’s the case, even if it doesn’t turn out as we expect. Any time there’s a surprise, it’s always exciting.”

The research has been published in The Planetary Science Journal.

 



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Astronomers Peer Into The Atmosphere of a Rare Exoplanet That ‘Shouldn’t Exist’

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The discovery of the extraordinary exoplanet LTT 9779b was first announced a month ago. Just 260 light-years away, the planet was immediately pegged as an excellent candidate for follow-up study of its curious atmosphere. But it turns out we didn’t even have to wait too long to learn more.

 

LTT 9779b is a little bigger than Neptune, orbiting a Sun-like star – fairly normal so far. But two things are really peculiar. It’s so close to its star, the planet orbits once every 19 hours; and, in spite of the scorching heat it must be subjected to at that proximity, LTT 9779b still has a substantial atmosphere.

Infrared observations collected by the now-retired Spitzer Space Telescope included the planet’s host star, and astronomers have now analysed those data, publishing their results in a couple of studies.

In the first paper, a team led by astronomer Ian Crossfield of the University of Kansas has described LTT 9779b’s temperature profile.

In the second paper, a team led by astronomer Diana Dragomir of the University of New Mexico has characterised the exoplanet’s atmosphere.

“For the first time, we measured the light coming from this planet that shouldn’t exist,” Crossfield said.

“This planet is so intensely irradiated by its star that its temperature is over 3,000 degrees Fahrenheit [1,650 degrees Celsius] and its atmosphere could have evaporated entirely. Yet, our Spitzer observations show us its atmosphere via the infrared light the planet emits.”

phase curveAn exoplanet phase curve. (ESA)

He and his team studied the exoplanet’s phase curve in infrared light. Here’s what that means: Because thermal energy is emitted as infrared radiation, light in this wavelength can tell us the temperature of cosmic objects many light-years away.

The system is oriented in such a way that the planet passes between us and the star, giving us clear broadside views of both the planet’s night and day sides. Thus, to calculate the exoplanet’s temperature, astronomers can use the changing light of the overall system as LTT 9779b orbits.

 

Interestingly, the hottest time of day for LTT 9779b is just about bang on noon, when its sun is directly overhead. On Earth, the hottest time of day is actually a few hours after noon, because heat enters Earth’s atmosphere faster than it is radiated back out into space.

In turn, this allows for some educated guesses about the atmosphere of LTT 9779b.

“The planet is much cooler than we expected, which suggests that it is reflecting away much of the incident starlight that hits it, presumably due to dayside clouds,” said astronomer Nicolas Cowan of the Institute for Research on Exoplanets (iREx) and McGill University in Canada.

“The planet also doesn’t transport much heat to its nightside, but we think we understand that: The starlight that is absorbed is likely absorbed high in the atmosphere, from whence the energy is quickly radiated back to space.”

To further probe the atmosphere of LTT 9779b, Dragomir and her colleagues focused on secondary eclipses, when the planet passes behind the star. This results in a fainter dimming of the system’s light than when the planet passes in front of the star – known as a transit – but that fainter dimming can help us understand the thermal structure of an exoplanet’s atmosphere.

 

“Hot Neptunes are rare, and one in such an extreme environment as this one is difficult to explain because its mass isn’t large enough to hold on to an atmosphere for very long,” Dragomir said.

“So how did it manage? LTT 9779b had us scratching our heads, but the fact that it has an atmosphere gives us a rare way to investigate this type of planet, so we decided to probe it with another telescope.”

The researchers combined Spitzer secondary eclipse data with data from NASA’s exoplanet-hunting space telescope TESS. This allowed them to obtain an emission spectrum from LTT 9779b’s atmosphere; that is, the wavelengths of light absorbed and amplified by elements therein. They found that some wavelengths were being absorbed by molecules – probably carbon monoxide.

This is not unexpected for such a hot planet. Carbon monoxide has been detected in hot Jupiters – gas giants that also orbit their stars at scorchingly close proximity. But gas giants are more massive than hot Neptunes, and use their much higher gravity to retain their atmospheres. It was thought that Neptune-sized planets should not be massive enough to do so.

 

Finding carbon monoxide in the atmosphere of a hot Neptune could help us understand how this planet formed, and why it still has its atmosphere.

So, while we know more about LTT 9779b than we did, there’s still work to be done. Future observations could help us answer these questions and others, such as what else is the atmosphere made of, and did the exoplanet start off much larger, and is currently in the process of rapidly shrinking.

Research like this will give us an excellent toolkit and experience for probing the atmospheres of potentially habitable worlds, too.

“If anyone is going to believe what astronomers say about finding signs of life or oxygen on other worlds, we’re going to have to show we can actually do it right on the easy stuff first,” Crossfield said.

“In that sense these bigger, hotter planets like LTT 9779b act like training wheels and show that we actually know what we’re doing and can get everything right.”

The two papers have been published in The Astrophysical Journal Letters, here and here.

 



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The BepiColombo Probe Just Took a Ridiculously Close Video of Venus as It Flew By

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Two years after it left Earth, Mercury probe BepiColombo has completed the first of its first flybys of Venus. The manoeuvre is designed to give the spacecraft a boost on its journey – but it’s also too good an opportunity to pass up for a little science.

 

As it swung around the planet on a curved trajectory, BepiColombo gave its instruments a workout, testing their functionality for a taste of what the spacecraft will do in Mercury orbit and collecting some data on Venus – recently in the news for the discovery of phosphine gas in its atmosphere.

And the joint European Space Agency (ESA) and Japan Aerospace Exploration Agency (JAXA) probe took a whole lot of images, which the ESA compiled into a video of the flyby.

“This sequence of 64 images was captured by Monitoring Camera 2 onboard the Mercury Transfer Module from 40 minutes before until 15 minutes after closest approach of 10,720 kilometres (6,661 miles) from Venus,” wrote the ESA in a blog post. “The images were taken every 52 seconds.”

The images had to be slightly processed – Venus was so bright that the images are quite saturated, even with the shortest exposure times. But the shape of the terminator line, which marks the boundary between night and day, changes as BepiColombo moves around the planet in a curved trajectory.

venus flyby body 700(ESA/BepiColombo/MTM)

Gravity assist manoeuvres are a very common tool for moving spacecraft around the Solar System. They’re also the work of very careful planning, with a route painstakingly mapped out in advance, with forward projection of where planets and moons are going to be when the spacecraft reaches them, in order to make the most of the encounters a voyaging spacecraft is going to have.

Basically, gravity assists use the gravity of a planet to aid the spacecraft in its journey, altering its trajectory and speed – either giving it a slingshot forwards, or helping it slow down. BepiColombo’s journey involves nine gravity assists. The first involved Earth on April 10, earlier this year.

Venus was the second, taking place on October 15, using the planet’s gravity to slow the spacecraft down without expending fuel. The third will also be Venus, in August 2021; the remaining six gravity assist flybys will be of Mercury itself, further slowing BepiColombo down so that it can finally arrive in a stable orbit in December 2025.

Both Venus flybys will be used to test BepiColombo instruments and collect Venus data. In this first flyby, scientists with the German Aerospace Center (DLR) and the University of Münster in Germany fired up the MErcury Radiometer and Thermal Infrared Spectrometer (MERTIS) instrument to take almost 100,000 images as BepiColombo approached the planet.

“During the Earth flyby, we studied the Moon, characterising MERTIS in flight for the first time under real experimental conditions. We achieved good results,” said MERTIS project manager Gisbert Peter of the DLR Institute of Optical Sensor Systems.

 

“Now we are pointing MERTIS towards a planet for the first time. This will allow us to make comparisons with measurements taken prior to the launch of BepiColombo, to optimise operation and data processing, and to gain experience for the design of future experiments.”

Venus and Mercury are quite different from one another – Mercury’s a naked ball of dense rock and metal, and Venus is shrouded in a thick, toxic atmosphere that keeps the planet’s surface temperature at scorching levels. MERTIS was designed to collect data on the rock composition of Venus, but its infrared capabilities can also penetrate Venus’ clouds to a certain depth.

MERTIS won’t be able to detect the phosphine that so intrigued the world. But one theory about the phosphine was that it was created by volcanic activity. And recent evidence suggests that volcanic activity may be ongoing on Venus; this is something MERTIS can investigate.

“These [volcanoes] would be detected, for example, through the sulphur dioxide that they emit,” said planetary scientist Jörn Helbert from the DLR Institute of Planetary Research.

 

“Following the first measurements made in the 1960s and 1970s, about ten years ago, ESA’s Venus Express mission recorded a massive reduction, by more than half, of sulphur dioxide concentrations. Venus literally ‘smells’ of active volcanoes! MERTIS could now provide us with new information.”

We won’t have that information for a little while yet. The newly collected data will have to make its way down the processing and analysis pipeline. But it’s so exciting, being on the cusp of a new era of Solar System science. And, although it’s not BepiColombo’s main mission, it’s really exciting having a different, newer set of tools to poke into Venus’ mysteries.

“We are already expecting some very interesting findings, with more to follow in 2021, when we will be much closer to Venus,” said planetary scientist Harald Hiesinger of the University of Münster.

 



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