Tag: exoplanets

For the first time astronomers measure the rotation of exoplanets

10:10 am

The uncertainty of science: Using the Keck Telescope in Hawaii astronomers for the first time have measured the rotation of several exoplanets orbiting the star HR8799, about 129 light years away.

Using the state-of-the-art Keck Planet Imager and Characterizer (KPIC) on the Keck II telescope atop Hawaiʻi Island’s Maunakea, astronomers found that the minimum rotation speeds of HR 8799 planets d and e clocked in at 10.1 km/s and 15 km/s, respectively. This translates to a length of day that could be as short as three hours or could be up to 24 hours such as on Earth depending on the axial tilts of the HR 8799 planets, which are currently undetermined. For context, one day on Jupiter lasts nearly 10 hours; its rotation speed is about 12.7 km/s.

As for the other two planets, the team was able to constrain the spin of HR 8799 c to an upper limit of less than 14 km/s; planet b’s rotation measurement was inconclusive.

These results are somewhat uncertain, as are any conclusions theorists try to draw from them. Even if confirmed, the sample is so small it doesn’t tell us anything yet about overall trends in planet formation or the expected spin rate of planets as they form.

Nonetheless, the detection appears valid and thus a scientific triumph. Astronomers have been telling me for years that figuring out ways to find out more about exoplanets is going to become the next hot subject in astronomy. This result illustrates this.

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Astronomers detect for the first time an accretion disk around an exoplanet

8:43 am

The exoplanet and its accretion disk
Click for full image.

Using the Atacama Large Millimetre/submillimeter Array (ALMA) in Chile, astronomers have made the first confirmed images of a moon-forming accretion disk around another a very young exoplanet.

The photo to the right shows this, with the top image the wide view showing the exoplanet in its orbit around the star, in an area inside the star’s own accretion disk (the larger ring) that the planet has apparently cleared of debris as it gathered itself. The bottom image zooms into the planet to show its own disk of material.

From the press release:

The disc in question, called a circumplanetary disc, surrounds the exoplanet PDS 70c, one of two giant, Jupiter-like planets orbiting a star nearly 400 light-years away. Astronomers had found hints of a “moon-forming” disc around this exoplanet before but, since they could not clearly tell the disc apart from its surrounding environment, they could not confirm its detection — until now.

In addition, with the help of ALMA, Benisty and her team found that the disc has about the same diameter as the distance from our Sun to the Earth and enough mass to form up to three satellites the size of the Moon.

The exoplanet’s disk is thus very large compared to our solar system, but that isn’t surprising considering the difficulty of observing it at such distances. Disks comparable in size to our solar system and the Earth-Moon system are simply too small for any telescope to yet image in this way.

The new data also found this interesting fact: The other known Jupiter-like exoplanet in this system does not have its own accretion disk or any visible debris orbiting it. Why one planet still has such debris and the other does not is a mystery related to the formation of solar systems that is at present not understood.

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2,000 nearby stars found that see the Earth cross in front of the Sun

9:47 am

Astronomers have identified 2,134 nearby stars that at some point in the past, present, or future are properly positioned along the solar system’s ecliptic so that the Earth can be seen transiting in front of the Sun.

From their paper’s abstract:

[W]e report that 1,715 stars within 100 parsecs from the Sun are in the right position to have spotted life on a transiting Earth since early human civilization (about 5,000 years ago), with an additional 319 stars entering this special vantage point in the next 5,000 years. Among these stars are seven known exoplanet hosts, including Ross-128, which saw Earth transit the Sun in the past, and Teegarden’s Star and Trappist-1, which will start to see it in 29 and 1,642 years, respectively. We found that human-made radio waves have already swept over 75 of the closest stars on our list. [emphasis mine]

I like the detail highlighted. Of the stars that could definitely identify the Earth by transits, 75 are also now close enough to have also heard our radio broadcasts. Should any of those stars also have a sufficiently advanced alien civilization, they could know of our existence. These same stars in turn make for very good targets of study for us to see if there is alien life there.

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Possible exoplanet detected in habitable zone around Alpha Centauri A?

10:47 am

The uncertainty of science: Scientists have detected faint evidence that suggests the existence of a Neptune-sized exoplanet circling the sunlike star Alpha Centauri A.

After analyzing 100 hours of data gathered by NEAR in May and June of 2019, the scientists detected a thermal fingerprint in the habitable zone of Alpha Centauri A. The signal potentially corresponds to a roughly Neptune-size world orbiting between 1 and 2 astronomical units (AU) from the star, study team members said. (One AU, the average Earth-sun distance, is about 93 million miles, or 150 million kilometers.)

But that planet has not yet been confirmed, so it remains a candidate for now.

This result is very uncertain at this moment, so we should constrain our enthusiasm. If true, however, it would signal the possibility of more exoplanets circling the stars of the nearest stellar system. Alpha Centauri is actually three stars, a binary of two sunlike stars circled at great distance by the red dwarf Proxima Centauri. Scientists already think there are exoplanets circling Proxima, with one about the size of Earth.

What makes this particular interesting, if true, is that the exoplanet was detected not by the slight wobble its gravity caused in the star, or by a transit across the face of the star, but by its own light. If the detection is real, this would be I think the first time that an exoplanet has been seen directly, even if that detection comprises a few tiny pixels of light.

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Astronomers detect radio signal from an exoplanet’s magnetic field

5:10 pm

The uncertainty of science: Astronomers using a Netherlands telescope have detected a radio signal coming from an exoplanet 51 light years away that likely comes from the planet’s magnetic field.

The new research actually began at Jupiter; the researchers had previously studied that planet’s radio emissions and then tweaked those measurements to reflect the effect they expected closeness to the host star and distance from Earth would have had on their observations of an exoplanet.

Then, the scientists consulted observations made in 2016 and 2017 by the Low Frequency Array (LOFAR) in the Netherlands. In addition to the potential signal from Tau Boötes b, the researchers also report that they may have picked up a signal from the star Upsilon Andromedae or its planet, but that detection was even fainter than the one from Tau Boötes b.

Obviously, there are many uncertainties with this data. However, if scientists can begin to measure and characterize the magnetic field of exoplanets it will give them an important new data point for studying them.

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Two dozen exoplanets superior to Earth for life?

8:45 am

The uncertainty of science: A team of scientists have now identified 24 exoplanets from the Kepler telescope archive that they propse might actually be better for life than Earth itself.

All the exoplanets are rocky and terrestrial, like the Earth. All are in the habitable zone, meaning that they orbit their star at a distance that makes their general temperature comparable to Earth.

What makes them superior, according to these scientists, are three factors. First, their stars are not G-type stars, like the Sun, but K-types. K-types have much longer lifespans, 70 billion years compared to the Sun’s 8 to 10 billion, allowing more time for life to develop.

Second, the planets have a slightly greater mass than Earth.

Part of the reason the Earth is habitable is because it’s large enough to be geologically active, giving it a protective magnetic field, and has enough gravity to retain an atmosphere. According to the team, if a planet was 10 percent larger, it would have more surface area to live on. If it was 1.5 times as massive as the Earth, its interior would retain more heat from radioactive decay, would remain active longer, and hold onto its atmosphere for a longer time.

Finally, the orbits of these two dozen exoplanets makes them just slighter warmer than Earth, which is thought to be beneficial to life.

This is interesting, but it is pure guesswork. These factors might make our Earth life happier, but these scientists have no idea if such conditions are beneficial or harmful to the creation of life. At present we have zero data on what the ideal conditions would be.

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Astronomers detect the first exoplanet orbiting a white dwarf

3:33 pm

Astronomers announced today that they have detected the first exoplanet orbiting a white dwarf, meaning that it somehow survived the star’s expansion into a red giant.

The way a white dwarf is created destroys nearby objects either by incineration or gravitational destruction. White dwarfs form when stars like the Sun near the end of their life cycles. They swell up, expand to hundreds and even thousands of times their regular size, forming a red giant. Eventually, that outer, expanded layer is ejected from the star and only a hot, dense white dwarf core remains.

So how did a planet, known as WD 1856 b, that is Jupiter-like get into such a close proximity that it completes an orbit of the white dwarf (that is only 18,000 km / 11,000 miles across) every 34 hours?

“WD 1856 b somehow got very close to its white dwarf and managed to stay in one piece,” said Andrew Vanderburg, an assistant professor of astronomy at the University of Wisconsin-Madison. “The white dwarf creation process destroys nearby planets, and anything that later gets too close is usually torn apart by the star’s immense gravity. We still have many questions about how WD 1856 b arrived at its current location without meeting one of those fates.”

Here we go again: This news story, as well as all of the press releases for this announcement (here, here, here, and here) — in their effort to hype this release — all conveniently forget to mention that the very first exoplanets ever discovered back in 1992 actually orbited a pulsar, the remains of a star that had not only died but had died in a cataclysmic supernova explosion. Moreover, that discovery was not of one exoplanet, but three, forming a solar system of three rocky terrestrial exoplanets all orbiting the pulsar at distances less than 43 million miles, which would put them inside the orbit of Venus.

How those terrestrial planets survived a supernova was a mystery. Today’s discovery only heightens that same puzzle, as this Jupiter-sized exoplanet orbits much closer to its white dwarf.

Regardless, the press releases from these universities and NASA should have made these facts clear. Instead, they pump up this discovery as if it is the very first ever. Today’s discovery might have unique components (the first hot Jupiter exoplanet orbiting a white dwarf) but it isn’t the first of this kind, not by a long shot.

Expect the press by tomorrow to compound this failure. Modern reporters seem completely uneducated about the subjects they write about, and also seem all-to-willing to accept on faith whatever public relations departments tell them.

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TESS completes primary mission

9:33 am

Having now imaged 75% of the entire night sky and completing its primary mission, scientists have now begun the extended mission for the Transiting Exoplanet Survey Satellite (TESS), designed to look for transiting exoplanets.

TESS monitors 24-by-96-degree strips of the sky called sectors for about a month using its four cameras. The mission spent its first year observing 13 sectors comprising the southern sky and then spent another year imaging the northern sky.

Now in its extended mission, TESS has turned around to resume surveying the south. In addition, the TESS team has introduced improvements to the way the satellite collects and processes data. Its cameras now capture a full image every 10 minutes, three times faster than during the primary mission. A new fast mode allows the brightness of thousands of stars to be measured every 20 seconds, along with the previous method of collecting these observations from tens of thousands of stars every two minutes. The faster measurements will allow TESS to better resolve brightness changes caused by stellar oscillations and to capture explosive flares from active stars in greater detail.

These changes will remain in place for the duration of the extended mission, which will be completed in September 2022. After spending a year imaging the southern sky, TESS will take another 15 months to collect additional observations in the north and to survey areas along the ecliptic – the plane of Earth’s orbit around the Sun – that the satellite has not yet imaged.

So far the telescope has spotted more than 2,100 exoplanet candidates, with 66 confirmed.

All told, TESS has divided the sky into 26 sectors, 13 in the north and 13 in the south. It can only look at one at a time for a month, and scientists use that one month data, collected more than once, to see if there are any changes. Because of the gaps in TESS’s view of each sector, however, it is guaranteed to miss some exoplanets (the majority) whose transits occur when it is not looking.

Imagine if we had 25 more of these space telescopes in orbit, so that each sector could be watched continually. This is totally doable now, and would make it possible to soon create a census of transiting exoplanets across the entire sky.

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Astronomers use Hubble to detect ozone on Earth

8:57 am

Using the Hubble Space Telescope, scientists have shown that it will be possible to detect ozone in the atmospheres of exoplanets, using larger telescopes while observing transits of those exoplanets across the face of their star.

What the scientists did was aim Hubble at the Moon during a lunar eclipse. Moreover, they timed the observations so that the sunlight hitting the Moon and reflecting back to Earth (and Hubble) had also traveled through the Earth’s atmosphere on its way to the Moon.

They then looked at the spectrum of that light, and were able to glean from it the spectral signal of ozone in the Earth’s atmosphere. When giant ground-based telescopes under construction now come on line in the coming decades they will have the ability to do this with transiting exoplanets.

The measurements detected the strong spectral fingerprint of ozone, a key prerequisite for the presence – and possible evolution – of life as we know it in an exo-Earth. Although some ozone signatures had been detected in previous ground-based observations during lunar eclipses, Hubble’s study represents the strongest detection of the molecule to date because it can look at the ultraviolet light, which is absorbed by our atmosphere and does not reach the ground. On Earth, photosynthesis over billions of years is responsible for our planet’s high oxygen levels and thick ozone layer. Only 600 million years ago Earth’s atmosphere had built up enough ozone to shield life from the Sun’s lethal ultraviolet radiation. That made it safe for the first land-based life to migrate out of our oceans.

“Finding ozone in the spectrum of an exo-Earth would be significant because it is a photochemical byproduct of molecular oxygen, which is a byproduct of life,” explained Allison Youngblood of the Laboratory for Atmospheric and Space Physics in Colorado, USA, lead researcher of Hubble’s observations.

Ozone does not guarantee the presence of life on an exoplanet, but combined with other detections, such as oxygen and methane, would raise the odds significantly.

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First image of multi-exoplanets around young sunlike star

10:00 am

Two exoplanets in one image

Worlds without end: Using the Very Large Telescope (VLT) in Chile, astronomers have taken the first image that captures two different exoplanets circling a young sunlike star.

The star’s light is partly blocked in the upper left of the photo to the right, cropped slightly to post here.

You can read the paper here [pdf]. The star itself, though similar in mass to the Sun, is thought to be only seventeen million years old.

But the system, dubbed TYC 8998-760-1, is nothing like our solar system. One of the star’s companions straddles the line that defines planets, with a mass 14 times Jupiter’s; the other has a mass of six Jupiters. Both orbit far from the star, about 160 and 320 times the average distance between Earth and the Sun. That puts them more than four times farther out than Pluto is from the Sun.

The size and distance of these giant planets were why they could be imaged from the ground.

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Two super-Earths found orbiting nearby red dwarf star

2:40 pm

Worlds without end: Astronomers have detected evidence of two super-Earths orbiting Gliese 887, only 11 light years away and the brightest red dwarf star in the night sky.

They used a technique known as “Doppler wobble”, which enables them to measure the tiny back and forth wobbles of the star caused by the gravitational pull of the planets. The regular signals correspond to orbits of just 9.3 and 21.8 days, indicating two super-Earths – Gliese 887b and Gliese 887c – both larger than the Earth yet moving rapidly, much faster even than Mercury. Scientists estimate the temperature of Gliese 887c to be around 70oC.

Because Gliese 887 is a very constant star, not very active, and with relatively few strong flares, they think these planets have a chance of retaining their atmospheres.

Be aware that these are like most exoplanets only candidate exoplanets. Until their existence is confirmed by other researchers, it is possible the detection is a false one.

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A host of new solar systems

11:20 am

A gallery of baby solar systems

Worlds without end: Astronomers this month released a large collection of images taken during the past four years by the Gemini South Telescope in Chile of young stars that also have debris disks and are likely solar systems in the process of forming.

The image to the right, reduced slightly to post here, is only a sampling of the 26 disk systems found out of 104 young stars photographed. Go to the link to see some higher resolution examples.

Of the 26 images of debris disks obtained by the Gemini Planet Imager (GPI), 25 had “holes” around the central star that likely were created by planets sweeping up rocks and dust. Seven of the 26 were previously unknown; earlier images of the other 19 were not as sharp as those from GPI and often didn’t have the resolution to detect an inner hole. The survey doubles the number of debris disks imaged at such high resolution.

“One of the things we found is that these so-called disks are really rings with inner clearings,” said Esposito, who is also a researcher at the SETI Institute in Mountain View, California. “GPI had a clear view of the inner regions close to the star, whereas in the past, observations by the Hubble Space Telescope and older instruments from the ground couldn’t see close enough to the star to see the hole around it.”

The data strongly confirms most theories about planet formation in these debris disks, as one of the youngest stars did not have any gaps in its disk, suggesting no larger bodies had yet formed to clear out a region.

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Astronomers claim discovery of six exomoons

9:03 am

The uncertainty of science: Astronomers are now claiming they have detected evidence of the existence of six exomoons orbiting different stars with transiting exoplanets.

“These exomoon candidates are so small that they can’t be seen from their own transits. Rather, their presence is given away by their gravitational influence on their parent planet,” Wiegert said.

If an exoplanet orbits its star undisturbed, the transits it produces occur precisely at fixed intervals.

But for some exoplanets, the timing of the transits is variable, sometimes occurring several minutes early or late. Such transit timing variations – known as TTVs – indicate the gravity of another body. That could mean an exomoon or another planet in the system is? affecting the transiting planet.

What they have basically done is applied the technique used to identify exoplanet candidates when the planet does NOT transit the star (the wobble caused by gravity and indicated by spectral changes), and looked to see if they can see the same variations in these exoplanets.

This is fun stuff, but it is so uncertain as to be almost laughable. If you read the press release closely, you will discover that their work has been submitted for publication, but has not yet been even peer reviewed.

Their concept is good, but I would not pay much attention to these “results.”

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Exoplanet in Earth-like orbit circling Sun-type star

9:54 am

Worlds without end: Astronomers have found evidence suggesting the existence of an exoplanet about twice as massive as the Earth and orbiting a solar-twin star in an orbit almost the same as the Earth’s.

The star, Kepler-160, is about 3,000 light years away, and had previously discovered to have two exoplanets.

“Our analysis suggests that Kepler-160 is orbited not by two but by a total of four planets,” Heller summarizes the new study. One of the two planets that Heller and his colleagues found is Kepler-160d, the previously suspected planet responsible for the distorted orbit of Kepler-160c. Kepler-160d does not show any transits in the light curve of the star and so it has been confirmed indirectly. The other planet, formally a planet candidate, is KOI-456.04, probably a transiting planet with a radius of 1.9 Earth radii and an orbital period of 378 days. Given its Sun-like host star, the very Earth-like orbital period results in a very Earth-like insolation from the star – both in terms of the amount of the light received and in terms of the light color. Light from Kepler-160 is visible light very much like sunlight. All things considered, KOI-456.04 sits in a region of the stellar habitable zone – the distance range around a star admitting liquid surface water on an Earth-like planet – that is comparable to the Earth’s position around the Sun.

“KOI-456.01 is relatively large compared to many other planets that are considered potentially habitable. But it’s the combination of this less-than-double the size of the Earth planet and its solar type host star that make it so special and familiar,” Heller clarifies. As a consequence, the surface conditions on KOI-456.04 could be similar to those known on Earth, provided its atmosphere is not too massive and non-Earth-like. The amount of light received from its host star is about 93 percent of the sunlight received on Earth. If KOI-456.04 has a mostly inert atmosphere with a mild Earth-like greenhouse effect, then its surface temperature would be +5 degrees Celsius on average, which is about ten degrees lower than the Earth’s mean global temperature.

These results have many uncertainties, so we should not be surprised if further research produces significant revisions in these conclusions. Nonetheless, the number of Earth-like planets orbiting Sun-like stars in orbits like the Earth’s continues to rise.

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Second exoplanet confirmed orbiting Proxima Centauri

12:51 pm

Worlds without end: Using archived Hubble data, astronomers have now independently confirmed the existence of a second exoplanet orbiting the nearest star, Proxima Centauri.

Dubbed Proxima c, this is not the same Earth-sized exoplanet confirmed to orbit the star last week. That planet, Proxima b, orbits close to the star every 11.2 days. The new planet is much farther out.

Benedict found a planet with an orbital period of about 1,907 days buried in the 25-year-old Hubble data. This was an independent confirmation of the existence of Proxima Centauri c.

Shortly afterward, a team led by Raffaele Gratton of INAF published images of the planet at several points along its orbit that they had made with the SPHERE instrument on the Very Large Telescope in Chile.

Benedict then combined the findings of all three studies: his own Hubble astrometry, Damasso’s radial velocity studies, and Gratton’s images to greatly refine the mass of Proxima Centauri c. He found that the planet is about 7 times as massive as Earth.

Though I am unaware of any hints of additional planets orbiting Proxima Centauri, the presence of two strongly implies the likelihood of more.

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New observations confirm Earth-like planet orbiting nearest star

9:44 am

Worlds without end: New observations have confirmed the existence of an Earth-sized planet orbiting the nearest star to our Sun, Proxima Centauri, only 4.2 light years away..

The planet, Proxima b, is estimated to have a mass 1.17 of Earth’s, and orbit the star every 11.2 days. Based on that orbit, the planet is also in the star’s habitable zone. Whether there is life there however remains unknown.

Although Proxima b is about 20 times closer to its star than the Earth is to the Sun, it receives comparable energy, so that its surface temperature could mean that water (if there is any) is in liquid form in places and might, therefore, harbour life.

Having said that, although Proxima b is an ideal candidate for biomarker research, there is still a long way to go before we can suggest that life has been able to develop on its surface. In fact, the Proxima star is an active red dwarf that bombards its planet with X rays, receiving about 400 times more than the Earth. “Is there an atmosphere that protects the planet from these deadly rays?” asks Christophe Lovis, a researcher in UNIGE’s Astronomy Department and responsible for ESPRESSO’s scientific performance and data processing. “And if this atmosphere exists, does it contain the chemical elements that promote the development of life (oxygen, for example)? How long have these favourable conditions existed? We’re going to tackle all these questions.

The research data also suggests there might be another planet in orbit around Proxima Centauri, though this conclusion is very preliminary.

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First exoplanet imaged was nothing more than a debris cloud

2:41 pm

The uncertainty of science: What had originally been thought to be the first image ever taken of an exoplanet has now turned out to be only the fading and expanding cloud of debris, left over from a collusion.

The object, called Fomalhaut b, was first announced in 2008, based on data taken in 2004 and 2006. It was clearly visible in several years of Hubble observations that revealed it was a moving dot. Until then, evidence for exoplanets had mostly been inferred through indirect detection methods, such as subtle back-and-forth stellar wobbles, and shadows from planets passing in front of their stars.

Unlike other directly imaged exoplanets, however, nagging puzzles arose with Fomalhaut b early on. The object was unusually bright in visible light, but did not have any detectable infrared heat signature. Astronomers conjectured that the added brightness came from a huge shell or ring of dust encircling the planet that may possibly have been collision-related. The orbit of Fomalhaut b also appeared unusual, possibly very eccentric. “Our study, which analyzed all available archival Hubble data on Fomalhaut revealed several characteristics that together paint a picture that the planet-sized object may never have existed in the first place,” said Gáspár.

The team emphasizes that the final nail in the coffin came when their data analysis of Hubble images taken in 2014 showed the object had vanished, to their disbelief. Adding to the mystery, earlier images showed the object to continuously fade over time, they say. “Clearly, Fomalhaut b was doing things a bona fide planet should not be doing,” said Gáspár.

The interpretation is that Fomalhaut b is slowly expanding from the smashup that blasted a dissipating dust cloud into space. Taking into account all available data, Gáspár and Rieke think the collision occurred not too long prior to the first observations taken in 2004. By now the debris cloud, consisting of dust particles around 1 micron (1/50th the diameter of a human hair), is below Hubble’s detection limit. The dust cloud is estimated to have expanded by now to a size larger than the orbit of Earth around our Sun.

This is not the first exoplanet that astronauts thought they had imaged, only to find out later that it was no such thing.

Remember this when next you hear or read some scientist telling you they are certain about their results, or that the science is “settled.” Unless you can get close enough to get a real picture in high resolution, or have tons of data from many different sources over a considerable period of time, and conclusions must always be subject to skepticism

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Earth-sized exoplanet in habitable zone found in old Kepler data

10:25 am

A review of the data produced by the space telescope Kepler, now retired, has discovered an exoplanet about the same size as Earth and also located in the habitable zone that had been missed previously by software.

Scientists discovered this planet, called Kepler-1649c, when looking through old observations from Kepler, which the agency retired in 2018. While previous searches with a computer algorithm misidentified it, researchers reviewing Kepler data took a second look at the signature and recognized it as a planet. Out of all the exoplanets found by Kepler, this distant world – located 300 light-years from Earth – is most similar to Earth in size and estimated temperature.

This newly revealed world is only 1.06 times larger than our own planet. Also, the amount of starlight it receives from its host star is 75% of the amount of light Earth receives from our Sun – meaning the exoplanet’s temperature may be similar to our planet’s as well. But unlike Earth, it orbits a red dwarf. Though none have been observed in this system, this type of star is known for stellar flare-ups that may make a planet’s environment challenging for any potential life.

A number of Earth-like planets have been found around red dwarf stars. Whether life could evolve in such places is entirely unknown. Red dwarfs are small, and would have likely formed in a nebula cloud with a dearth of many elements and materials needed for life. Moreover, because they are also so dim, the habitable zone is very near the star, meaning that, as the article mentions, strong flares are more dangerous.

At the same time, red dwarfs are the most common star, and the most long-lived, capable of burning for tens of billions of years. With enough time and numbers anything is still possible.

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An exoplanet where it rains iron

10:12 am

Astronomers have discovered an exoplanet 640 light years away hot enough for iron to be vapor in the atmosphere and to condense out as rain.

The high-resolution spectrum reveals lots of iron vapor within the sliver of atmosphere undergoing the transition from day to night. However, this iron vapor signature is missing from the sliver of atmosphere transitioning from night to day. The astronomers think this happens because strong winds push iron vapor to the nightside, where it cools and condenses into clouds.

“This planet has a twilight zone at a temperature close to the iron condensation temperature,” Ehrenreich explains, “so the change in atmospheric composition (with iron vs. without iron) is occurring right where we are able to observe.”

Because the planet is a gas giant, there’s no surface onto which the droplets can fall, says coauthor Nuno Santos (University of Porto, Portugal). But the planet’s gravity likely pulls the clouds downward, enveloping the nightside in iron fog. The global winds then push the clouds and fog onto the dayside, where the vaporization-condensation cycle repeats again.

Very exotic, and alien, and I guarantee it is probably far more alien than we so far can guess.

You can find out more in this second more detailed article.

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Review of Kepler data uncovers seventeen more possible exoplanets

11:08 am

Worlds without end: In reviewing the entire Kepler database of 200,000 stars, scientists have found seventeen more candidate exoplanets, including one only 1.5 times the mass of the Earth that is also in the habitable zone.

From the paper’s abstract:

We present the results of an independent search of all ~200,000 stars observed over the four year Kepler mission (Q1–Q17) for multiplanet systems, using a three-transit minimum detection criterion to search orbital periods up to hundreds of days. We incorporate both automated and manual triage, and provide estimates of the completeness and reliability of our vetting pipeline. Our search returned 17 planet candidates (PCs) in addition to thousands of known Kepler Objects of Interest (KOIs), with a 98.8% recovery rate of already confirmed planets. We highlight the discovery of one candidate, KIC-7340288 b, that is both rocky (radius $\leqslant 1.6{R}_{\oplus }$) and in the Habitable Zone (insolation between 0.25 and 2.2 times the Earth’s insolation). Another candidate is an addition to the already known KOI-4509 system.

I must emphasize that these are candidate exoplanets, meaning their existence has not been confirmed by other observations, and could very well turn out to be false positives.

Still, that this independent review matched the previous list of Kepler candidates within 98.8% means that the list of exoplanet candidates from Kepler is solid and worth further study. With thousands of candidates, however, that further study is likely going to take a very long time. And the backlog will be growing significantly with the many thousands of additional exoplanet candidates expected to be found by TESS.

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Successful first light for CHEOPS space telescope

12:02 pm

The science team for Europe’s exoplanet-hunting CHEOPS space telescope announced today that the telescope has successfully obtained its first pictures, and that all appears to be working correctly.

Preliminary analysis has shown that the images from CHEOPS are even better than expected. However, better for CHEOPS does not mean sharper as the telescope has been deliberately defocused. This is because spreading the light over many pixels ensures that the spacecraft’s jitter and the pixel-to-pixel variations are smoothed out, allowing for better photometric precision. “The good news is that the actual blurred images received are smoother and more symmetrical than what we expected from measurements performed in the laboratory,” says Benz. High precision is necessary for CHEOPS to observe small changes in the brightness of stars outside our solar system caused by the transit of an exoplanet in front of the star. Since these changes in brightness are proportional to the surface of the transit planet, CHEOPS will be able to measure the size of the planets. “These initial promising analyses are a great relief and also a boost for the team,” continues Benz.

I suspect the planned fuzziness of their images is why the press release did not include them.

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A second exoplanet orbiting Proxima Centauri?

9:32 am

Worlds without end: Astronomers think they have found evidence of a second exoplanet orbiting the nearest star, Proxima Centauri.

The planet, a super-Earth called Proxima Centauri c (Proxima c for short), has at least six times more mass than Earth and orbits its star every 5.2 years.

…“Stars like Proxima Centauri are rather restless and continuously present eruptions and spots on their surface, which make the detection of a planetary-induced oscillation very complicated,” says coauthor Fabio Del Sordo (University of Crete and Foundation for Research and Technology-Hellas in Heraklion, Greece). Because the observations span almost two decades, the scientists have confidently ruled out those sources of noise, but they caution that follow-up observations are needed to confirm that the signal comes from a planet.

There is a lot of uncertainty here, requiring an independent confirmation of this result. It would not be surprising if this exoplanet vanished when others took a look, finding it a creation not of a periodic gravitation wobble but of the random fluctuations of the star itself.

If it does exist, it will not likely be a place where life exists. Too far from this very dim red dwarf star to get enough energy. However, as a super-Earth it might someday in the far future be a great mining world.

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More superEarth exoplanets found circling nearby stars

9:41 am

Worlds without end: Among a new bunch of thirteen exoplanets, astronomers have discovered two more superEarth-sized exoplanets circling nearby red dwarf stars.

The two potentially habitable planets are orbiting GJ180 and GJ229A, which are among the nearest stars to our own Sun, making them prime targets for observations by next-generation space- and land-based telescopes. They are both super-Earths with at least 7.5 and 7.9 times our planet’s mass and orbital periods of 106 and 122 days respectively.

The Neptune-mass planet—found orbiting GJ433 at a distance at which surface water is likely to be frozen—is probably the first of its kind that is a realistic candidate for future direct imaging. “GJ 433 d is the nearest, widest, and coldest Neptune-like planet ever detected,” Feng added.

For a lot of reasons it is likely that life as we know it probably does not exist on these planets. Nonetheless, their close proximity makes it possible to study them, and since we have no such planets in our own solar system they can teach us a lot about planetary formation and evolution.

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TESS finds its first Earth

10:02 pm

Worlds without end: TESS has discovered its first Earth-sized planet, orbiting a M dwarf star within the habitable zone.

TOI 700 is a small, cool M dwarf star located just over 100 light-years away in the southern constellation Dorado. It’s roughly 40% of the Sun’s mass and size and about half its surface temperature. The star appears in 11 of the 13 sectors TESS observed during the mission’s first year, and scientists caught multiple transits by its three planets.

The star was originally misclassified in the TESS database as being more similar to our Sun, which meant the planets appeared larger and hotter than they really are. Several researchers, including Alton Spencer, a high school student working with members of the TESS team, identified the error.

“When we corrected the star’s parameters, the sizes of its planets dropped, and we realized the outermost one was about the size of Earth and in the habitable zone,” said Emily Gilbert, a graduate student at the University of Chicago. “Additionally, in 11 months of data we saw no flares from the star, which improves the chances TOI 700 d is habitable and makes it easier to model its atmospheric and surface conditions.”

We could also give this story the subhead “the uncertainty of science.” Note how a revision of the star’s mass changed the planet’s. Though I am sure they have improved their estimate of the star, this error illustrates how easy it is to get a final astronomical conclusion wrong. There are always a lot of assumptions long the way, any one of which could have a margin of error significant enough to change the final result.

In other TESS news, the space telescope has also found an exoplanet orbiting a stellar binary system of two stars.

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TESS completes 1st survey of southern sky

1:19 pm

The TESS science team today released its first full panorama of the southern sky, revealing everything the space telescope has imaged since launch in one image.

The glow of the Milky Way — our galaxy seen edgewise — arcs across a sea of stars in a new mosaic of the southern sky produced from a year of observations by NASA’s Transiting Exoplanet Survey Satellite (TESS). Constructed from 208 TESS images taken during the mission’s first year of science operations, completed on July 18, the southern panorama reveals both the beauty of the cosmic landscape and the reach of TESS’s cameras. “Analysis of TESS data focuses on individual stars and planets one at a time, but I wanted to step back and highlight everything at once, really emphasizing the spectacular view TESS gives us of the entire sky,” said Ethan Kruse, a NASA Postdoctoral Program Fellow who assembled the mosaic at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

Within this scene, TESS has discovered 29 exoplanets, or worlds beyond our solar system, and more than 1,000 candidate planets astronomers are now investigating.

A reduced version of this image wouldn’t show anyone its beauty or significance. I have embedded below the fold the short video at the link which shows it quite nicely. The video also summarized the mission quite well.
» Read more

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A big planet circling a small star

10:03 am

The uncertainty of science: In contradiction of every existing stellar and planetary formation model, astronomers have found a half-sized Jupiter exoplanet orbiting a tiny red dwarf star.

The red dwarf GJ 3512 is located 30 light-years from us. Although the star is only about a tenth of the mass of the Sun, it possesses a giant planet – an unexpected observation. “Around such stars there should only be planets the size of the Earth or somewhat more massive Super-Earths,” says Christoph Mordasini, professor at the University of Bern and member of the National Centre of Competence in Research (NCCR) PlanetS: “GJ 3512b, however, is a giant planet with a mass about half as big as the one of Jupiter, and thus at least one order of magnitude more massive than the planets predicted by theoretical models for such small stars.”

It appears the universe does not care what this and other scientists think “should” happen. The universe will do what the universe wants to do.

This discovery only underlines how little we understand of the formation of stars and their solar system. Be prepared for many more like surprises in the coming decades and centuries.

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New theory says evaporating exomoon explains Tabby’s Star

9:47 am

Astronomers have proposed a new theory for the random and inexplicable light variations that Tabby’s Star undergoes, a melting and evaporating exomoon.

The Columbia team suggests that Tabby’s Star abducted an exomoon from a now long-gone, nearby planet and pulled it into orbit around itself, where it has been getting torn apart by stronger stellar radiation than existed in its former orbit. Chunks of the exomoon’s dusty outer layers of ice, gas, and carbonaceous rock have been able to withstand the radiation blow-out pressure that ejects smaller-grain dust clouds, and the volatile, large-grain material has inherited the exomoon’s new orbit around Tabby’s Star, where it forms a disk that persistently blocks the star’s light. The opaqueness of the disk can change slowly, as smaller-grain clouds pass through and larger particles stuck in orbit move from the disk toward Tabby’s Star, eventually getting so hot that they melt and fall onto the star’s surface.

Ultimately, after millions of years, the exomoon orbiting Tabby’s Star will completely evaporate, the researchers suggest.

The article does not explain why the theory requires this exoplanet to have once been a moon to another exoplanet, now gone. It seems to me that this is adding unnecessary complexity to the solution, but I have not read the paper itself, so their might be reasons.

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Water found on exoplanet in habitable zone

10:00 am

The uncertainty of science: Astronomers now believe they have detected water in the atmosphere of an exoplanet that is also in habitable zone.

A new study by Professor Björn Benneke of the Institute for Research on Exoplanets at the Université de Montréal, his doctoral student Caroline Piaulet and several of their collaborators reports the detection of water vapour and perhaps even liquid water clouds in the atmosphere of the planet K2-18b.

…This exoplanet is about nine times more massive than our Earth and is found in the habitable zone of the star it orbits. This M-type star is smaller and cooler than our Sun, but due to K2-18b’s close proximity to its star, the planet receives almost the same total amount of energy from its star as our Earth receives from the Sun.

The size and mass of the this exoplanet means life as we know it probably does not exist there, either on its surface or in its atmosphere. Nonetheless, with water and the right amount of energy, anything is still possible.

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Astronomers find Jupiter-sized exoplanet with comet-like orbit

10:46 am

Worlds without end: Astronomers have discovered a Jupiter-sized exoplanet with an extremely eccentric and comet-like orbit circling a star about 103 light years away.

Astronomers have discovered a planet three times the mass of Jupiter that travels on a long, egg-shaped path around its star. If this planet were somehow placed into our own solar system, it would swing from within our asteroid belt to out beyond Neptune. Other giant planets with highly elliptical orbits have been found around other stars, but none of those worlds were located at the very outer reaches of their star systems like this one.

This discovery, like so many others, illustrates again our lack of knowledge about the make-up and formation of solar systems. According to modern formation theories, you shouldn’t get such a large exoplanet in such an eccentric orbit. But here we are.

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Data suggests Earth-sized exoplanet has no atmosphere and resembles Mercury

9:11 am

Using archive data from the Spitze Space Telescope astronomers believe that an Earth-sized exoplanet about 49 light years away probably has no atmosphere and is likely similar to Mercury.

Discovered in 2018 by NASA’s Transiting Exoplanet Satellite Survey (TESS) mission, planet LHS 3844b is located 48.6 light-years from Earth and has a radius 1.3 times that of Earth. It orbits a small, cool type of star called an M dwarf – especially noteworthy because, as the most common and long-lived type of star in the Milky Way galaxy, M dwarfs may host a high percentage of the total number of planets in the galaxy.

…The Spitzer observations rule out an atmosphere with more than 10 times the pressure of Earth’s. (Measured in units called bars, Earth’s atmospheric pressure at sea level is about 1 bar.) An atmosphere between 1 and 10 bars on LHS 3844b has been almost entirely ruled out as well, although the authors note there’s a slim chance it could exist if the stellar and planetary properties were to meet some very specific and unlikely criteria. They also argue that with the planet so close to a star, a thin atmosphere would be stripped away by the star’s intense radiation and outflow of material (often called stellar winds).

For a planet to be in the habitable zone of a M dwarf it must orbit very close to the star. This research suggests that conditions that close to the star might still preclude the possibility of life.

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