Category: Discoveries (page 3 of 4)

A Solar System Found Crowded With Seven Earth-Sized Exoplanets

Seven Earth-sized rocked planets have been detected around the red dwarf star TRAPPIST-1. The system is 40 light years away, but is considered to be an easy system to study — as explanet research goes. (NASA)

Seven planets orbiting one star.  All of them roughly the size of Earth.  A record three in what is considered the habitable zone, the distance from the host star where liquid water could exist on the surface.  The system a mere 40 light-years away.

The latest impressive additions to the world of exoplanets orbit the dwarf star known as TRAPPIST-1, named after a European Southern Observatory telescope in Chile.

Previously a team of astronomers based in Belgium discovered three  planets around this dim star, but now that number has increased to include the largest number of Earth-sized planets found to date, as well as the largest number in one solar system in the habitable zone.

This is a very different kind of sun-and-exoplanet system than has generally been studied.  The broad quest for an Earth-sized planet in a habitable zone has focused on stars of the size and power of our sun.  But this one is 8 percent the mass of our sun —  not that much larger than Jupiter — and with a luminosity (or energy) but 0.05 percent of that put out by our sun.

The TRAPPIST-1 findings underscore one of the recurring and intriguing aspects of the exoplanet discoveries of the past two decades — the solar systems out there are a menagerie of very different shapes and sizes, with exoplanets of a wild range of sizes orbiting an equally wide range of types and sizes of stars.

Michaël Gillon of the STAR Institute at the University of Liège in Belgium, and lead author of the discovery reported in the journal Nature, put it this way: “This is an amazing planetary system — not only because we have found so many planets, but because they are all surprisingly similar in size to the Earth.”

At a NASA press conference, he also said that “small stars like this are much more frequent than stars like ours.  Now we have seven Earth-sized planets to study, three in the habitable or ‘Goldilocks’ zone, and that’s quite promising for search for life beyond Earth.”

He said that the planets are so close to each other than if a person was on the surface of one, the others would provide a wonderful close-up view, rather like our view of the moon.… Read more

Proxima b Is Surely Not "Earth-like." But It’s A Research Magnet And Just May Be Habitable.

Simulated comparison of a sunset on Earth and Proxima b. The red-dwarf star Proxima Centauri appears almost three times bigger than the Sun in a redder and darker sky. Red-dwarf stars appear bigger in the sky than sun-like stars, even though they are smaller. This is because they are cooler and the planets have to be closer to them to maintain temperate conditions. The original photo of the beach was taken at Playa Puerto Nuevo in Vega Baja, Puerto Rico. Credit: PHL @ UPR Arecibo.

A simulated comparison of a sunset on Earth and Proxima b. The images sets out to show that the red-dwarf star Proxima Centauri appears almost three times bigger than our sun in a redder and darker sky. There is value in illustrating how conditions in different solar systems would change physical conditions on the planets, but there is a real danger that the message conveyed becomes the similarities between planets such as Earth and Proxima b.  At this point, there is no evidence that Proxima b is “Earth-like” at all. The original photo of the beach was taken at Playa Puerto Nuevo in Vega Baja, Puerto Rico. (PHL @ UPR Arecibo))

It is often discussed within the community of exoplanet scientists that a danger lies in the description of intriguing exoplanets as “Earth-like.”

Nothing discovered so far warrants the designation, which is pretty nebulous anyway.  Size and the planet’s distance from a host star are usually what earn it the title “Earth-like,” with its inescapable expectation of inherent habitability. But residing in a habitable zone is just the beginning; factors ranging from the make-up of the planet’s host star to the presence and content of an atmosphere and whether it has a magnetic field can be equally important.

The recent announcement of the detection of a planet orbiting Proxima Centauri, the closest star to our own, set off another round of excitement about an “Earth-like” planet.  It was generally not scientists who used that phrase — or if they did, it was in the context of certain “Earth-like” conditions.  But the term nonetheless became a kind of shorthand for signalling a major discovery that just might some day even yield a finding of extraterrestrial life.

Consider, however, what is actually known about Proxima b:

  • The planet, which has a minimum mass of 1.3 Earths and a maximum of many Earths, orbits a red dwarf star.  These are the most common class of star in the galaxy, and they put out considerably less luminosity than a star like our sun — about one-tenth of one percent of the power.
  • These less powerful red dwarf stars often have planets orbiting much closer to them than what’s found in solar systems like our own.   Proxima b, for instance, circles the star in 11.3 days.
  • A consequence of this proximity is that the planet is most likely tidally locked by the gravitational forces of the star — meaning that the planet does not rotate like Earth does but rather has a daytime and nighttime side like our moon. 
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Found: Our Nearest Exoplanet Neighbor

This artist ’ s impression shows a view of the surface of the planet Proxima b orbiting t he red dwarf star Proxima Centauri, the closest star to the Solar System. The double star A lpha Centauri AB also appears in the image to the upper-right of Proxima itself. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, wh ere the temperature is suitable for liquid water to exist on its surface. Credit: ESO/M. Kornmesser

An artist impression of the surface of the candidate planet Proxima b orbiting the red
dwarf star Proxima Centauri, the closest star to the Solar System. The double star Alpha Centauri AB also appears in the image. Proxima b is a little more massive than the Earth and orbits in the habitable zone around Proxima Centauri, where the temperature is suitable for liquid water to exist on its surface.
(ESO/M. Kornmesser)

No exoplanet can possibly be closer to us than the one just detected around our nearest stellar neighbor, Proxima Centauri.

The long-sought and long-imagined planet is larger than Earth, but small enough to be rocky as opposed to a gas or ice giant.  Making things even more exciting, the planet was detected inside the habitable zone of Proxima, suggesting that the planet could potentially have temperatures that allow for pooling liquid water.

Innumerable questions remain to be answered before we know if it actually is habitable (as opposed to residing in a habitable zone), and far more before we know if it might actually be inhabited.

But the very exciting news is that an exoplanet has almost definitively been found only 4 light-years from our solar system.  There’s every reason to believe it will become the focus of intense and sustained scientific scrutiny.

The detection is the culmination of a “Pale Red Dot” observing campaign that began in earnest early this year to search the regions close to Proxima for exoplanets.  Guillem Anglada-Escudé  of Queen Mary University, London, was a leader that campaign, as well as earlier efforts to dig deeper into decade-old Proxima Centauri data from other teams that hinted at a planet but were far from definitive.

“The signal that a planet orbits Proxima every 11 days is strong, so we have little doubt that it’s there,” AngladaEscude´ said.  “And because this is the closest possible planet outside our solar system, there’s a sense of finding something special, even inspirational.”

His hope is that the detection will become a global “driver,”  a discovery that is significant enough to change how people think about our world, as well as about the possibility that some day humans will explore up close a planet outside our system.

Said Anglada-Escude´:  “The search for life on Proxima b comes next….”

 

Caption: This picture combines a view of the southern skies over the ESO 3.6-metre telescope at the La Silla Observatory in Chile with images of the stars Proxima Centauri (lowe r-right) and the double star Alpha Centauri AB (lower-left) from the NASA/ESA Hubble Space Telescope. Proxima Centauri is the closest star to the Solar System and is orbited by the planet Proxima b, which was discovered using the HARPS instrument on the ESO 3.6-metre telescope. Credit: Y. Beletsky (LCO)/ESO/ESA/NASA/M. Zamani

This picture combines a view of the southern skies over the European Southern Observatory’s 3.6-metre telescope at the La Silla Observatory in Chile with images of the stars Proxima Centauri (lower right) and the double star Alpha Centauri AB (lower-left) from the NASA/ESA Hubble Space Telescope.

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Rocky, Close and Potentially Habitable Planets Around a Dwarf Star

This artist’s impression shows an imagined view from the surface one of the three planets orbiting an ultracool dwarf star just 40 light-years from Earth that were discovered using the TRAPPIST telescope at ESO’s La Silla Observatory. (M. Kornmesser/ESO)

This artist’s impression shows an imagined view from the surface one of the three planets orbiting an ultracool dwarf star just 40 light-years from Earth that were discovered using the TRAPPIST telescope at ESO’s La Silla Observatory. (M. Kornmesser/ESO)

Forty light-years away is no small distance. But an announcement of the discovery of two planets at that separation that have been determined to be rocky and Earth-sized adds a significant new twist to the ever-growing collection of relatively close-by exoplanets that just might be habitable.

The two planets in the TRAPPIST-1 system orbit what is known as a red dwarf star, a type of star that is typically much cooler than the sun, emitting radiation in the infrared rather than the visible spectrum.  While there has been much debate about whether an exoplanet around a dwarf can be deemed habitable, especially since they are all believed to be tidally locked and so only one side faces the star, a consensus appears to be growing that dwarf stars could host habitable planets.

The two new rocky exoplanets were detected using the Hubble Space Telescope and were deemed most likely rocky by the compact sizes of their atmospheres — which were not large and diffuse hydrogen/helium envelopes (like that of the Jupiter) but instead more tightly packed, more like the atmospheres of Earth, Venus, and Mars.  It was the first time scientists have been able to search for and at least partially characterize of atmospheres around a temperate, Earth-sized planet.

Having determined that the planets are rocky, principal investigator Julien de Wit of M.I.T’s Department of Earth, Atmospheric and Planetary Sciences, said the goal now is to characterize their atmospheres.

“Now the question is, what kind of atmosphere do they have?” de Wit said. “The plausible scenarios include something like Venus, where the atmosphere is dominated by carbon dioxide, or an Earth-like atmosphere with heavy clouds, or even something like Mars with a depleted atmosphere. The next step is tomtry to disentangle all these possible scenarios that exist for these terrestrial planets.”

Artist's impression of the two planets in the Trappist-1 solar system. These worlds have sizes, temperatures and potentially atmospheres similar to those of Venus and Earth. Some believe they may be the best targets found so far for the search for life outside the solar system. They are the first planets ever discovered around such a tiny and dim star. (Nasa/ESA/STScI)

Artist’s impression of the two planets in the Trappist-1 solar system. These worlds have sizes, temperatures and potentially atmospheres similar to those of Venus and Earth. Some believe they may be the best targets found so far for the search for life outside the solar system. They are the first planets ever discovered around such a tiny and dim star. (Nasa/ESA/STScI)

 

Host stars with exoplanets that are (very relatively) close to us are highly valued because they are potentially easier to observe and characterize.… Read more

Three Star Ballet, With Exoplanet

This artist's impression shows a view of the triple-star system HD 131399 from close to the giant planet orbiting in the system. The planet is known as HD 131399Ab and appears at the lower-left of the picture. Located about 320 light-years from Earth in the constellation of Centaurus (The Centaur), HD 131399Ab is about 16 million years old, making it also one of the youngest exoplanets discovered to date, and one of very few directly imaged planets. With a temperature of around 580 degrees Celsius and an estimated mass of four Jupiter masses, it is also one of the coldest and least massive directly-imaged exoplanets.

An artist’s impression of the triple-star system HD 131399 from close to the giant planet orbiting in the system. The planet is known as HD 131399Ab and appears at the lower-left of the picture. Located about 320 light-years from Earth in the constellation of Centaurus (The Centaur), HD 131399Ab is about 16 million years old, making it also one of the youngest exoplanets discovered to date, and one of very few directly imaged planets. (ESO/Luis Calcada)

It hardly seems possible, but researchers have detected a planet in apparently stable orbit within a three star system — a configuration now known as a trinary.

The ubiquity of binary stars has been understood for some time, and the presence of exoplanets orbiting around and within them is no longer a surprise.  But this newest planet detected — four times the mass of Jupiter — is most unusual because trinary systems are not known to be particularly conducive to keeping planets in orbit, and especially not a planet in an extremely wide (i.e., 550 year) orbit.

Yet this planet has found the sweet spot between the stars where it balances the gravitational pulls of the three.  The system is a relative toddler at 16 million years old, and so the researchers involved in its detection say it may later be ejected from the system.  But for now, it is the only known planet of its kind.

The discovery, reported in the journal Science, was made using the European Southern Observatory’s Very Large Telescope (VLT) in Chile’s Atacama desert.  The team was from the University of Arizona in Tucson and was led by Daniel Apai, an assistant professor of Astronomy and Planetary Sciences who leads a planet finding and observing group.  That team includes research doctoral student Kevin Wagner, the first author on the paper.

“It is not clear how this planet ended up on its wide orbit in this extreme system — and we can’t say yet what this means for our broader understanding of the types of planetary systems — but it shows that there is more variety out there than many would have deemed possible,” Wagner said.

This new planet is a gas giant and definitely not habitable, but the possible universe of exoplanets that just might meet some of the basic criteria for habitability may well have grown.

“What we do know is that planets in multi-star systems have been studied far less often, but are potentially just as numerous as planets in single-star systems,” Wagner said.… Read more

A Flood of Newly Confirmed Exoplanets

Artist renderings of exoplanets previously detected by the Kepler Space Telescope (NASA)

Artist renderings of exoplanets previously detected by the Kepler Space Telescope (NASA)

In the biggest haul ever of new exoplanets, scientists with NASA’s Kepler mission announced the confirmation of 1,284 additional planets outside our solar system — including nine that are relatively small and within the habitable zones of their host stars.  That almost doubles the number of these treasured rocky planets that orbit their stars at distances that could potentially support liquid water and potentially life.

Prior to today’s announcement, scientists using Kepler and all other exoplanet detection approaches had confirmed some 2,100 planets in 1,300 planetary systems.  So this is a major addition to the exoplanets known to exist and that are now available for further study by scientists.

These detections comes via the Kepler Space Telescope, which collected data on tiny decreases in the output of light from distant stars during its observing period between 2009 and 2013.  Those dips in light were determined by the Kepler team to be planets crossing in front of the stars rather than impostors to a 99 percent-plus probability.

As Ellen Stofan, chief scientist at NASA Headquarters put it,  “This gives us hope that somewhere out there, around a star much like ours, we can eventually discover another Earth.”

he histogram shows the number of planet discoveries by year for more than the past two decades of the exoplanet search. The blue bar shows previous non-Kepler planet discoveries, the light blue bar shows previous Kepler planet discoveries, the orange bar displays the 1,284 new validated planets. (NASA Ames/W. Stenzel; Princeton University/T. Morton)

The histogram shows the number of planet discoveries by year for more than the past two decades of the exoplanet search. The blue bar shows previous non-Kepler planet discoveries, the light blue bar shows previous Kepler planet discoveries, the orange bar displays the 1,284 new validated planets.
(NASA Ames/W. Stenzel; Princeton University/T. Morton)

The primary goals of the Kepler mission are to determine the demographics of exoplanets in the galaxy, and more specifically to determine the population of small, rocky planets (less than 1.6 times the size of Earth) in the habitable zones of their stars.  While orbiting in such a zone by no means assures that life is, or was, ever present, it is considered to be one of the most important criteria.

The final Kepler accounting of how likely it is for a star to host such an exoplanet in its habitable zone won’t come out until next year.  But by all estimations, Kepler has already jump-started the process and given a pretty clear sense of just how ubiquitous exoplanets, and even potentially habitable exoplanets, appear to be.

“They say not to count our chickens before they’re hatched, but that’s exactly what these results allow us to do based on probabilities that each egg (candidate) will hatch into a chick (bona fide planet),” said Natalie Batalha, co-author of the paper in the Astrophysical Journal and the Kepler mission scientist at NASA’s Ames Research Center.… Read more

A Dwarf Star, Trappist-1, Produces a Major Discovery

his artist's illustration depicts an imagined view from the surface of one of the three newfound TRAPPIST-1 alien planets. The planets have sizes and temperatures similar to those of Venus and Earth, making them the best targets yet for life beyond our solar system, scientists say. Credit: ESO/M. Kornmesser

An imagined view from the surface of one of the three newfound TRAPPIST-1 exoplanets. The planets have sizes and temperatures similar to those of Venus and Earth, making them attractive scientific targets in the search for potentially habitable planets beyond our solar system.
(ESO/M. Kornmesser)

The detection of potentially habitable exoplanets is not the big news it once was — there have been so many identified already that the novelty has faded a bit.  But that hardly means surprising and potentially breakthrough discoveries aren’t being made.  They are, and one of them was just announced Monday.

This is how the European Southern Observatory, which hosts the telescope used to make the discoveries, introduced them:

Astronomers using the TRAPPIST telescope at ESO’s La Silla Observatory have discovered three planets orbiting an ultra-cool dwarf star just 40 light-years from Earth. These worlds have sizes and temperatures similar to those of Venus and Earth and are the best targets found so far for the search for life outside the Solar System. They are the first planets ever discovered around such a tiny and dim star.

A team of astronomers led by Michaël Gillon, of the Institut d’Astrophysique et Géophysique at the University of Liège in Belgium, have used the Belgian TRAPPIST telescope to observe the star, now known as TRAPPIST-1. They found that this dim and cool star faded slightly at regular intervals, indicating that several objects were passing between the star and the Earth. Detailed analysis showed that three planets with similar sizes to the Earth were present.

The discovery has much going for it — the relative closeness of the star system, the rocky nature of the planets, that they might be in habitable zones.  But of special importance is that the host star is so physically small and puts out a sufficiently small amount of radiation that the planets — which orbit the star in only days — could potentially be habitable even though they’re so close.  The luminosity (or power) of Trappist-1 is but 0.05 percent of what’s put out by our sun.

This is a very different kind of sun-and-exoplanet system than has generally been studied.  The broad quest for an Earth-sized planet in a habitable zone has focused on stars of the size and power of our sun.  But this one is 8 percent the mass of our sun —  not that much larger than Jupiter.

“This really is a paradigm shift with regards to the planet population and the path towards finding life in the universe,” study co-author Emmanuël Jehin, an astronomer at the University of Liège, said in a statement.… Read more

Storming the One-Meter-Per-Second Barrier

Kitt Peak National Observatory mountain top at Dusk looking north. Visible in the picture are the NOAO 4-meter Mayall, the Steward Observatory 90-inch, the University of Arizona Lunar and Planetary Laboratory Spacewatch Telescopes, LOTIS, 0.4-meter Visitor Center Telescope, Case Western Reserve University Observatory and the SARA Observatory. Credit: P. Marenfeld (NOAO/AURA/NSF)

The Kitt Peak National Observatory, on the Tohono O’odham reservation outside Tucson, will be home to a next-generation spectrometer and related system which will allow astronomers to detect much smaller exoplanets through the radial velocity method.  P. Marenfeld (NOAO/AURA/NSF)

When the first exoplanet was identified via the radial velocity method, the Swiss team was able to detect a wobble in the star 51 Pegasi at a rate of 50 meters per second.   The wobble is the star’s movement back and forth caused by the gravitational pull of the planet, and in that first case it was dramatic — the effects of a giant Jupiter-sized planet orbiting extremely close to the star.

Many of the early exoplanet discoveries were of similarly large planets close to their host stars, but it wasn’t because there are so many of them in the cosmos.  Rather, it was a function of the capabilities of the spectrographs and other instruments used to view the star.  They were pioneering breakthroughs, but they didn’t have the precision needed to measure wobbles other than the large, dramatic ones caused by a close-in, huge planet.

That was the mid 1990s, and radial velocity astronomers have worked tirelessly since to “beat down” that 50 meters per second number.  And twenty years later, radial velocity astronomers using far more precise instruments and more refined techniques have succeeded substantially:  1 meter per second of wobble is now achieved for the quietest stars.  That has vastly improved their ability to find smaller exoplanets further from their stars and is a major achievement.  But it has nonetheless been a major frustration for astronomers because to detect terrestrial exoplanets in the Earth-sized range, they have to get much more precise  — in the range of tens of centimeters per second.

A number of efforts to build systems that can get that low are underway, most notably the ESPRESSO spectrograph scheduled to begin work on the High Accuracy Radial Vlocity Planet Searcher (HARPS) in Chile next year. Then earlier this month an ambitious NASA-National Science Foundation project was awarded to Penn State University to join the race.  The next-generation spectrograph is scheduled to be finished in 2019 and installed at the Kitt Peak National Observatory in Arizona, and its stated goal is to reach the 20 to 30 centimeters per second range.

Suvrath Mahadevan, an assistant professor at Penn State, is principal investigator for the project.  It is called NEID, which means ‘to see’ in the language of the Tohono O’odham, on whose land the Kitt Peak observatory is located.… Read more

Hunting for Exoplanets Via TESS

 

The TESS satellite, which will launch in 2017, will use four cameras to search for exoplanets around bright nearby stars. MIT

The TESS satellite, which will launch in 2017, will use four cameras to search for exoplanets around bright nearby stars. MIT initially proposed the mission, and it was approved in 2013.  (MIT)

Seven years ago this month the Kepler spacecraft launched into space – the first NASA mission dedicated to searching for planets around distant stars. The goal was to conduct a census of these exoplanets, to learn whether planets are common or rare. And in particular, to understand whether planets like Earth are common or rare.

With the discovery and confirmation of over 1,000 exoplanets (and thousands more exoplanet candidates that have not yet been confirmed), Kepler has taught us that planets are indeed common, and scientists have been able to make new inferences about how planetary systems form and evolve. But the planets found by Kepler are almost exclusively around distant, faint stars, and the observations needed to further study and characterize these planets are challenging. Enter TESS.

The Transiting Exoplanet Survey Satellite (TESS) is a NASA Explorer mission designed to search for new exoplanets around bright, nearby stars. The method that TESS will use is identical to that used by Kepler – it looks for planets that transit in front of their host star. Imagine that you’re looking at a star, and that star has planets around it.

If the orbit of the planet is aligned correctly, then once per “year” of the planet (i.e. once per orbit), the planet will pass in front of the star. As the planet moves in front of the star, it blocks a small fraction of the light, so the star appears to get slightly fainter. As the planet moves out of transit, the star returns to normal brightness. We can see an example of this in our own solar system on May 9, 2016, as Mercury passes in front of the Sun.

Tranit

A small dip in the amount of light emanating from a star tells astronomers that a planet may well be crossing in front of it.

We can learn a lot from observing the transits of a planet. First, we can learn the size of a planet – the bigger the planet, the more light it will block, and the larger the “dip” in the brightness of the host star. Second, we can learn how long the planet’s year is – since it only passes in front of the star once per orbit, the time between transits is the planet’s year.… Read more

Shredding Exoplanets, And The Mysteries They May Unravel

In this artist’s conception, a tiny rocky object vaporizes as it orbits a white dwarf star. Astronomers have detected the first planetary object transiting a white dwarf using data from the K2 mission. Slowly the object will disintegrate, leaving a dusting of metals on the surface of the star. (NASA)

In this artist’s conception, a small planet or planetesimal vaporizes as it orbits close to a white dwarf star. The detection of several of these disintegrating planets around a variety of stars has led some astronomers to propose intensive study of their ensuing dust clouds as a surprising new way to learn about the interiors of  exoplanet.  (NASA)

One of the seemingly quixotic goals of exoplanet scientists is to understand the chemical and geo-chemical compositions of the interiors of the distant planets they are finding.   Learning whether a planet is largely made up of silicon or magnesium or iron-based compounds is essential to some day determining how and where specific exoplanets were formed in their solar systems, which ones might have the compounds and minerals believed to be necessary for  life, and ultimately which might actually be hosting life.

Studying exoplanet interiors is a daunting challenge for sure, maybe even more difficult in principle than understanding the compositions of exoplanet atmospheres.  After all, there’s still a lot we don’t know about the make-up of planet interiors in our own solar system.

An intriguing pathway, however, has been proposed based on the recent discovery of exoplanets in the process of being shredded.  Generally orbiting very close to their suns, they appear to be disintegrating due to intense radiation and the forces of gravity.

And the result of their coming apart is that their interiors, or at least the dust clouds from their crusts and mantles, may well be on display and potentially measurable.

“We know very little for sure about these disintegrating planets, but they certainly seem to offer a real opportunity,” said Jason Wright, an astrophysicist at Pennsylvania State University with a specialty in stellar astrophysics.  No intensive study of the dusty innards of a distant, falling-apart exoplanet has been done so far,  he said, but in theory at least it seems to be possible.

Artist’s impression of disintegrating exoplanet KIC 12255 (C.U Keller, Leiden University)

Artist’s impression of disintegrating exoplanet KIC 12557548, the first of its kind ever detected. (C.U Keller, Leiden University)

And if successful, the approach could prove broadly useful since astronomers have already found at least four of disintegrating planets and predict that there are many more out there.  The prediction is based on, among other things, the relative speed with which the planets fall apart.  Since the disintegration has been determined to take only tens of thousands to a million years (a very short time in astronomical terms) then scientists conclude that the shreddings must be pretty common  –based on the number already caught in the act.… Read more

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