Tag: Proxima Centauri

Earthlike exoplanet in habitable zone detected orbiting nearest star

9:21 am

The uncertainty of science: Astronomers think they have detected an Earthlike exoplanet, in habitable zone, orbiting Proxima Centauri, the nearest star to our solar system.

Astronomer João Faria and his collaborators detected Proxima Centauri d by measuring tiny shifts in the spectrum of the star’s light as the planet’s gravity pulled it during orbit. The team used a state-of-the art spectrograph called ESPRESSO at the Very Large Telescope, a system of four 8.2-metre telescopes at the European Southern Observatory in Cerro Paranal, Chile. The results were published on 10 February in Astronomy & Astrophysics.

This ‘wobble’ technique looks for changes in the star’s motion along the line of sight from Earth, and ESPRESSO can detect variations of just 10 centimeters per second. The total effect of the planet’s orbit, which lasts only five days, is about 40 cm/s, says Faria. “I knew that ESPRESSO could do this, but it was still surprised to see it showing up,” says Faria, who is at the Institute of Astrophysics and Space Sciences in Porto, Portugal.

Though the scientists are very confident about their results, the detection is at present only a candidate planet, as its existence has not been confirmed by an second independent method. Also, the method of detection cannot pin down the exoplanet’s mass very precisely, though it suggests the exoplanet has rocky planet mass, not too different than Earth’s.

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Astronomers detect largest flare ever, on Proxima Centauri

10:43 am

In May 2019 astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have detected the largest flare ever seen from any star, including our Sun, on the nearest star, the red dwarf Proxima Centauri.

The detection was 100 times stronger than the Sun’s typical flares.

In May 2019, Proxima Centauri ejected a violent flare that lasted just seven seconds, but generated a surge in both ultraviolet and millimeter wavelengths. The flare was characterized by a strong, impulsive spike never before seen at these wavelengths. The event was recorded by five of the nine telescopes involved in the study, including the Hubble Space Telescope (HST) in ultraviolet, and ALMA in millimeter wavelengths. “The star went from normal to 14,000 times brighter when seen in ultraviolet wavelengths over the span of a few seconds,” said MacGregor, adding that similar behavior was captured in millimeter wavelengths by ALMA at the same time.

Red dwarfs are known to issue very powerful flares, a high solar activity that would likely make life as we know it impossible on any Earth-sized planet in its habitable zone, since the star’s small size and dimness requires that zone to be so close to the star. This powerful flare only cements this reality. The exoplanets that have been found circling Proxima Century will therefore not be great places for life, though building the first interplanetary colony there might make sense.

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Mysterious signal detected possibly coming from Proxima Centauri

9:05 am

The uncertainty of science: Breakthough Listen, the project funded to the tune of $100 million by billionaire Yuri Milner with the goal of listening for alien radio signals, in 2019 detected a single radio tone that appeared to be coming from the nearest star, Proxima Centauri.

A team had been using the Parkes radio telescope in Australia to study Proxima Centauri for signs of flares coming from the red dwarf star, in part to understand how such flares might affect Proxima’s planets. The system hosts at least two worlds. The first, dubbed Proxima b upon its discovery in 2016, is about 1.2 times the size of Earth and in an 11-day orbit. Proxima b resides in the star’s “habitable zone,” a hazily defined sector in which liquid water could exist upon a rocky planet’s surface—provided, that is, Proxima Centauri’s intense stellar flares have not sputtered away a world’s atmosphere. Another planet, the roughly seven-Earth-mass Proxima c, was discovered in 2019 in a frigid 5.2-year orbit.

Using Parkes, the astronomers had observed the star for 26 hours as part of their stellar-flare study, but, as is routine within the Breakthrough Listen project, they also flagged the resulting data for a later look to seek out any candidate SETI signals. The task fell to a young intern in Siemion’s SETI program at Berkeley, Shane Smith, who is also a teaching assistant at Hillsdale College in Michigan. Smith began sifting through the data in June of this year, but it was not until late October that he stumbled upon the curious narrowband emission, needle-sharp at 982.002 megahertz, hidden in plain view in the Proxima Centauri observations. From there, things happened fast—with good reason. “It’s the most exciting signal that we’ve found in the Breakthrough Listen project, because we haven’t had a signal jump through this many of our filters before,” says Sofia Sheikh from Penn State University, who helmed the subsequent analysis of the signal for Breakthrough Listen and is the lead author on an upcoming paper detailing that work, which will be published in early 2021. Soon, the team began calling the signal by a more formal name: BLC1, for “Breakthrough Listen Candidate 1.”

The data so far does not suggest this signal was produced by an alien technology. Instead, it likely is a spurious signal from some natural or human source, picked up by accident, as was the SETI “Wow” signal that for years puzzled astronomers until they traced it to a comet.

However, as they do not yet have an explanation, it is a mystery of some importance.

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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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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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The search for exoplanets at Alpha Centauri

8:56 am

The search for new exoplanets orbiting the three stars of the Alpha Centauri star system is intensifying, despite significant viewing challenges and solar activity that precludes life around one star.

The system’s two sunlike stars, Alpha Centauri A and B, orbit each other closely while Proxima Centauri, a tempestuous red dwarf, hangs onto the system tenuously in a much more distant orbit. In 2016, astronomers discovered an Earth-mass planet around Proxima Centauri, but the planet, blasted by radiation and fierce stellar winds, seems unlikely to be habitable. Astrobiologists think the other two stars are more likely to host temperate, Earth-like planets.

Maksym Lisogorskyi, an astronomer at the University of Hertfordshire in Hatfield, U.K., tried to find them with an instrument on the European Southern Observatory’s (ESO’s) 3.6-meter telescope in Chile. He and his colleagues looked for Doppler shifts in the spectral lines of the stars’ light that would be caused if a planet tugged them back and forth. But Lisogorskyi told the meeting that the stars’ surfaces are turbulent, and prone to flares that also jiggle the spectral lines, masking the subtle signals from any Earth-size planets. “The lines do all kinds of things,” he says. Although Alpha Centauri has been a primary target for the planet-finding instrument since it was inaugurated in 2005, it has seen nothing so far.

Also hampering observations are the current positions of the two stars. As viewed from Earth, they are very close together, making them harder to study individually, Lily Zhao of Yale University told the meeting. More precise observations should become possible as their 80-year orbit carries them farther apart. In the meantime, Zhao and her colleagues have succeeded in ruling out the presence of giant planets around either star, based on a decade’s worth of data from three instruments on different telescopes. “There are no Jupiters in the system, but there may be plenty of Earth-sized planets still to discover,” she said.

I am skeptical of the conclusions of the astrobiologists who think there may be habitable Earth-like planets in orbit around the close binary. Binary formation makes planetary formation difficult, and even if they are there the stars’ orbits would make stable orbits unlikely. Nonetheless, the research is good, as the techniques learned will be applicable elsewhere.

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Astronomers find Kuiper Belt-like ring around Proxima Centauri

3:32 pm

Worlds without end: Astronomers have found a dusty ring 1 to 4 astronomical units from the nearest star, Proxima Centauri.

Because Proxima Centauri is a smaller, dimmer star, its system is more compact. Proxima b [the star’s known exoplanet] circles the star at 0.05 astronomical units (a.u., the average distance between Earth and the Sun) — for reference, Mercury orbits the Sun at 0.39 a.u. The dusty ring lies well beyond that, extending from 1 to 4 a.u.

The Proxima ring is similar in some ways to the Kuiper Belt, a cold, dusty belt in the far reaches of our solar system (beyond 40 a.u.) that contains a fraction of Earth’s mass. While the Kuiper belt is well known for larger members such as Pluto and Eris, it also contains fine grains, ground down through collisions over billions of years. The dust ALMA observed around Proxima Centauri is composed of similar small grains. The average temperature and total mass of the Proxima ring is also about the same as our Kuiper Belt.

Because the ring here much closer to the star than our Kuiper Belt, the material is much more densely packed. Moreover, the presence of both a ring and an exoplanet suggests more planets might remain undiscovered there, increasing the chances that this star could have a solar system very worthwhile exploring.

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Plotting the interstellar path to Proxima Centauri

8:40 am

Scientists have calculated the slingshot route that Breakthrough Starshot’s tiny interstellar spacecraft should take in order to reach Proxima Centauri while also gathering the maximum scientific data while zipping past the binary stars of Alpha Centauri.

The solution is for the probe’s sail to be redeployed upon arrival so that the spacecraft would be optimally decelerated by the incoming radiation from the stars in the Alpha Centauri system. René Heller, an astrophysicist working on preparations for the upcoming Exoplanet mission PLATO, found a congenial spirit in IT specialist Michael Hippke, who set up the computer simulations. The two scientists based their calculations on a space probe weighing less than 100 grams in total, which is mounted to a 100,000-square-metre sail, equivalent to the area of 14 soccer fields. During the approach to Alpha Centauri, the braking force would increase. The stronger the braking force, the more effectively the spacecraft’s speed can be reduced upon arrival. Vice versa, the same physics could be used to accelerate the sail at departure from the solar system, using the sun as a photon cannon.

The tiny spacecraft would first need to approach the star Alpha Centauri A as close as around four million kilometres, corresponding to five stellar radii, at a maximum speed of 13,800 kilometres per second (4.6 per cent of the speed of light). At even higher speeds, the probe would simply overshoot the star.

While most of this is hardly revolutionary, this is still the first time anyone has done the hard math based upon a real mission concept.

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More details about Proxima Centauri’s Earthlike exoplanet

8:50 am

Link here. Lots of background into the discovery itself, but I think these paragraphs really sum things up:

“The search for life starts now,” says Guillem Anglada-Escudé, an astronomer at Queen Mary University of London and leader of the team that made the discovery.

Humanity’s first chance to explore this nearby world may come from the recently announced Breakthrough Starshot initiative, which plans to build fleets of tiny laser-propelled interstellar probes in the coming decades. Travelling at 20% of the speed of light, they would take about 20 years to cover the 1.3 parsecs from Earth to Proxima Centauri.

Proxima’s planet is at least 1.3 times the mass of Earth. The planet orbits its red-dwarf star — much smaller and dimmer than the Sun — every 11.2 days. “If you tried to pick the type of planet you’d most want around the type of star you’d most want, it would be this,” says David Kipping, an astronomer at Columbia University in New York City. “It’s thrilling.”

The human race now has a real interstellar target to aim for. Don’t be surprised if we get there sooner than anyone predicts.

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Earthlike exoplanet discovered orbiting the nearest star

10:54 am

Worlds without end: An Earthlike exoplanet has been discovered in the habitable zone and orbiting Proxima Centauri, the nearest star to the Sun.

The CBC/AP story above doesn’t give many details, mainly because this story is breaking the Thursday embargo, when the actual science paper will be released. Expect a lot more news stories then about this, which probably ranks as one of the biggest science discoveries in history.

Since the embargo is broken, here are some facts from one of the press releases:

The planet, called Proxima b, orbits its parent star every 11 days and has a temperature suitable for liquid water to exist on its surface. This rocky world is a little more massive than the Earth, and is the closest planet outside our solar system. Planets around other stars are commonly referred to as exoplanets.

…Although Proxima b orbits much closer to its star than Mercury does to the Sun in the solar system, the star itself is far fainter than the sun. As a result Proxima b lies well within the habitable zone around the star and has an estimated surface temperature that would allow the presence of liquid water. Despite the temperate orbit of Proxima b, the conditions on the surface may be strongly affected by the ultraviolet and X-ray flares from the star — these would be far more intense than those the Earth experiences from the Sun.

They first had a hint of the planet’s existence in 2013 (which explains the unsourced rumors I’ve heard periodcally in the past few years about a exoplanet around Proxima Centauri) and spent the past two-plus years making absolutely sure they understood their data.

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