Category Archives: Exoplanets

Misc: Space visionaries, Satellite imagery in journalism, and Kepler retires

Some miscellaneous items of interest:

** The Return of the Space Visionaries – Rand Simberg/The New Atlantis – An excellent overview of the history and status of US human spaceflight and how commercial companies such as Elon Musk’s SpaceX and Jeff Bezos’s Blue Origin are taking the lead in the move to settle the solar system:

Musk talks about humanity being a multi-planet species, in part as an insurance policy against earthly disasters, whether natural or manmade; he is particularly concerned about the potential danger to humanity posed by artificial intelligence. But he seems to consider two — Earth and Mars — to be a sufficient number for “multi.” Musk could in fact be accused of an extension of what Carl Sagan called “planetary chauvinism” — the belief that life can thrive only on planets. But many analysts, I included, don’t understand the motivation, once having finally escaped the deep gravity well that has confined us to the planet on which we evolved, to dive down into another, albeit a shallower one.

By contrast, Bezos, as noted, aims for a massive human expansion, and not only to many other planets but to inhabitance of space itself. Wealthier than Musk — on some days he is the world’s richest person — Bezos is also more willing to spend his own money. Last November he sold a billion dollars’ worth of Amazon stock and claims to intend to do the same every year to provide the rocket company with its annual stipend, and he recently built a large facility at NASA’s Kennedy Space Center in Florida to begin the manufacture of his large orbital rockets. Musk, on the other hand, always prefers, if he can find a way, to fund his dreams using OPM — Other Peoples’ Money. In the case of Tesla and its subsidiary SolarCity, which sells solar panels for home and commercial use, he’s done it with loans from Washington (which he has since paid off), various government subsidies for the production of electric cars, and tax credits offered to people buying electric cars or installing solar panels. In the case of SpaceX, extra funding has come, albeit in this case in exchange for providing a direct service, from NASA and U.S. Air Force contracts.

Over a decade and a half since both men launched their space companies, they have made significant progress in reducing the cost of getting to suborbital and orbital space. If their plans for large reusable launch systems come to fruition in the next few years, with SpaceX’s BFR and possibly Blue Origin’s New Armstrong offering larger payload capacities than NASA’s non-reusable Space Launch System, they may well render it obsolete before the full Block 2 version flies. (The planned first flight of the initial Block 1 configuration of SLS has slipped to the end of 2019.) Before its second flight — probably no sooner than a year after its first — it may well be canceled for good, not to be resurrected, perhaps finally putting a stake through the heart of Apolloism.

** Satellite imagery for journalism: Why a picture is worth a thousand words – Geospatial World – A nice overview of how journalists are learning to use images taken by by satellites to investigate war crimes, environmental destruction, illegal fishing and many other

In July 2018, a disturbing video began circulating on social media. It shows two women and two young children being led at gunpoint away from a village by a group of soldiers. The victims are blindfolded before they are shot point blank 22 times. The social media posts claimed them to be from Cameroon but the government of Cameroon initially dismissed the video as “fake news”.

The video showed a terrain that could be from anywhere in the world, and the people could be anywhere from Africa. But BBC Africa Eye did a thorough investigation through forensic analysis of the footage. Among other things, they poured through satellite imagery of many years trying to match them with the landmarks in the video to prove exactly where and when this incident took place and who were responsible. The Cameroon government was forced to issue a statement clarifying their earlier stand and announced that a number of soldiers have been arrested and are under investigation now.

Satellite imagery has become an indispensable tool in journalism. Be it fact-finding or gauging the impact of a particular situation, reporting on climate events or conflict zones, because of the unbiased insights they provide, they are being extensively used by professional journalists today.

** The Kepler space telescope has retired from exoplanet finding after running out of station-keeping fuel. Here Robert Picardo pays tribute to a very successful mission: Farewell, Kepler – The Planetary Post with Robert Picardo

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Telescopes and Binoculars at Amazon

Hubble: Observations indicate a Neptune-sized moon orbiting Jupiter-sized exoplanet

Researchers using the Hubble telescope appear to have observed a gas-giant sized Moon orbiting an even larger planet in another star system:

Hubble finds compelling evidence for a moon outside the Solar System
Neptune-sized moon orbits Jupiter-sized planet

This artist’s impression depicts the exomoon candidate Kepler-1625b-i, the planet it is orbiting and the star in the centre of the star system. Kepler-1625b-i is the first exomoon candidate and, if confirmed, the first moon to be found outside the Solar System. Like many exoplanets, Kepler-1625b-i was discovered using the transit method. Exomoons are difficult to find because they are smaller than their companion planets, so their transit signal is weak, and their position in the system changes with each transit because of their orbit. This requires extensive modelling and data analysis. [Higher-res images]
Using the NASA/ESA Hubble Space Telescope and older data from the Kepler Space Telescope two astronomers have found the first compelling evidence for a moon outside our own Solar System. The data indicate an exomoon the size of Neptune, in a stellar system 8000 light-years from Earth. The new results are presented in the journal Science Advances.

The hunt for exoplanets — planets outside our own Solar System — provided its first results only 30 years ago. While astronomers now find these planets on a regular basis, the search for moons orbiting exoplanets wasn’t successful — until today.

This animation demonstrates how the measured light curve from the star Kepler-1625b led to the conclusion that the system may consist of not only a planet, but also at least one moon.

When the planet moves in front of its parent star a tiny portion of its light is blocked by the disc of the planet, so we observe a dimming of the light from the star. Right after the exoplanet has finished its transit the starlight is seen to dim slightly again, suggesting the presence of a moon trailing the planet. Credit: ESA/Hubble, L. Calçada

In 2017 NASA’s Kepler Space Telescope detected hints of an exomoon orbiting the planet Kepler-1625b. Now, two scientists from Columbia University in New York (USA) have used the incomparable capabilities of the NASA/ESA Hubble Space Telescope to study the star Kepler-1625, 8000 light-years away, and its planet in more detail. The new observations made with Hubble show compelling evidence for a large exomoon orbiting the only known planet of Kepler-1625. If confirmed, this would be the first discovery of a moon outside our Solar System.

The candidate moon, with the designation Kepler-1625b-i, is unusual because of its large size; it is comparable in diameter to the planet Neptune. Such gargantuan moons are unknown in our own Solar System.

“This may yield new insights into the development of planetary systems and may cause astronomers to revisit theories of how moons form,”

Alex Teachey, a graduate student who led the study, explained excitedly [1].

Like its moon, Kepler-1625b is also bigger than its counterparts in the Solar System. The exoplanet is a gas giant, several times more massive than Jupiter [2]. It orbits its parent star at a distance similar to the distance between the Sun and Earth, which puts it — and its candidate moon — at the inner edge of the habitable zone of the star system [3].

To find evidence for the existence of the exomoon, the team observed the planet while it was in transit in front of its parent star, causing a dimming of the starlight.

“We saw little deviations and wobbles in the light curve that caught our attention,”

David Kipping, second author of the study, said.

The planet was observed by Hubble before and during its 19-hour-long transit. After the transit ended, Hubble detected a second and much smaller decrease in the star’s brightness approximately 3.5 hours later, consistent with the effect of a moon trailing the planet.

“It was definitely a shocking moment to see that light curve — my heart started beating a little faster and I just kept looking at that signature,”

David Kipping described his feelings. Unfortunately, the scheduled Hubble observations ended before the complete transit of the moon could be captured.

In addition to this second dip in the light curve, Hubble provided compelling supporting evidence for the moon hypothesis by detecting the planet’s transit more than an hour earlier than predicted. This is consistent with a model of the system in which the planet and its moon orbit a common centre of gravity, causing the planet to wobble away from its predicted location [4].

In principle this anomaly could also be caused by the gravitational pull of a hypothetical second planet in the system, but the Kepler Space Telescope found no evidence for additional planets around the star during its four year mission. Still, further observations by Hubble are needed to fully confirm the existence of Kepler-1625b-i.

“If confirmed, Kepler-1625b-i will certainly provide an interesting puzzle for theorists to solve,” said Kipping. Teachey concluded: “It is an exciting reminder of how little we really know about distant planetary systems and the great spirit of discovery exoplanetary science embodies.”

Notes

[1] The moons of Jupiter and Saturn likely formed through the agglomeration into a disc of material orbiting the planets, so it is possible that this exomoon also formed in a circumplanetary disc. Another possibility is that a passing object was captured by the planet’s gravity. Tidal forces between the two objects would rob momentum from the less massive companion and eventually pull it into a permanent orbit. There are no indications of tidal capture among our Solar System’s moons. In the case of the Earth–Moon system, an early collision with a larger body is hypothesised to have blasted off material that later coalesced into a moon. However, Kepler-1625b and its candidate moon are gaseous, not rocky, so such a collision would not have led to the condensation of a satellite.

[2] Despite its size, the mass of the candidate moon is estimated to be only 1.5 percent of the mass of its companion planet. This value is close to the mass ratio between Earth and the Moon.

[3] While both the planet and its candidate moon are within the habitable zone, where moderate temperatures allow for the existence of liquid water, both bodies are considered to be gaseous and therefore unsuitable for life as we know it.

[4] A distant observer watching the Earth and Moon transit the Sun would note similar anomalies in the timing of Earth’s transit.

More information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

The results were presented in the paper Evidence for a large exomoon orbiting Kepler-1625b in the journal Science Advances.

The team of astronomers in this study consists of Alex Teachey and David M. Kipping (Columbia University, New York, USA).

Image credit: NASA, ESA

ESO: VLT captures first confirmed image of a planet forming

A new report from ESO (European Southern Observatory):

First Confirmed Image of Newborn Planet Caught with ESO’s VLT
Spectrum reveals cloudy atmosphere

This spectacular image from the SPHERE instrument on ESO’s Very Large Telescope is the first clear image of a planet caught in the very act of formation around the dwarf star PDS 70. The planet stands clearly out, visible as a bright point to the right of the centre of the image, which is blacked out by the coronagraph mask used to block the blinding light of the central star. [Higher-res images]
SPHERE, a planet-hunting instrument on ESO’s Very Large Telescope, has captured the first confirmed image of a planet caught in the act of forming in the dusty disc surrounding a young star. The young planet is carving a path through the primordial disc of gas and dust around the very young star PDS 70. The data suggest that the planet’s atmosphere is cloudy.

Astronomers led by a group at the Max Planck Institute for Astronomy in Heidelberg, Germany have captured a spectacular snapshot of planetary formation around the young dwarf star PDS 70. By using the SPHERE instrument on ESO’s Very Large Telescope (VLT) — one of the most powerful planet-hunting instruments in existence — the international team has made the first robust detection of a young planet, named PDS 70b, cleaving a path through the planet-forming material surrounding the young star [1].

The SPHERE instrument also enabled the team to measure the brightness of the planet at different wavelengths, which allowed properties of its atmosphere to be deduced.

The planet stands out very clearly in the new observations, visible as a bright point to the right of the blackened centre of the image. It is located roughly three billion kilometres from the central star, roughly equivalent to the distance between Uranus and the Sun. The analysis shows that PDS 70b is a giant gas planet with a mass a few times that of Jupiter. The planet’s surface has a temperature of around 1000°C, making it much hotter than any planet in our own Solar System.

This colourful image shows the sky around the faint orange dwarf star PDS 70 (in the middle of the image). The bright blue star to the right is χ Centauri. [Larger images]
The dark region at the centre of the image is due to a coronagraph, a mask which blocks the blinding light of the central star and allows astronomers to detect its much fainter disc and planetary companion. Without this mask, the faint light from the planet would be utterly overwhelmed by the intense brightness of PDS 70.

“These discs around young stars are the birthplaces of planets, but so far only a handful of observations have detected hints of baby planets in them,” explains Miriam Keppler, who lead the team behind the discovery of PDS 70’s still-forming planet. “The problem is that until now, most of these planet candidates could just have been features in the disc.”

The discovery of PDS 70’s young companion is an exciting scientific result that has already merited further investigation. A second team, involving many of the same astronomers as the discovery team, including Keppler, has in the past months followed up the initial observations to investigate PDS 70’s fledgling planetary companion in more detail. They not only made the spectacularly clear image of the planet shown here, but were even able to obtain a spectrum of the planet. Analysis of this spectrum indicated that its atmosphere is cloudy.

PDS 70’s planetary companion has sculpted a transition disc — a protoplanetary disc with a giant “hole” in the centre. These inner gaps have been known about for decades and it has been speculated that they were produced by disc-planet interaction. Now we can see the planet for the first time.

Keppler’s results give us a new window onto the complex and poorly-understood early stages of planetary evolution,” comments André Müller, leader of the second team to investigate the young planet. “We needed to observe a planet in a young star’s disc to really understand the processes behind planet formation.

By determining the planet’s atmospheric and physical properties, the astronomers are able to test theoretical models of planet formation.

This glimpse of the dust-shrouded birth of a planet was only possible thanks to the impressive technological capabilities of ESO’s SPHERE instrument, which studies exoplanets and discs around nearby stars using a technique known as high-contrast imaging — a challenging feat. Even when blocking the light from a star with a coronagraph, SPHERE still has to use cleverly devised observing strategies and data processing techniques to filter out the signal of the faint planetary companions around bright young stars [2] at multiple wavelengths and epochs.

Thomas Henning, director at the Max Planck Institute for Astronomy and leader of the teams, summarises the scientific adventure:

After more than a decade of enormous efforts to build this high-tech machine, now SPHERE enables us to reap the harvest with the discovery of baby planets!

Notes
[1] The disc and planet images and the planet’s spectrum have been captured in the course of the two survey programmes called SHINE (SpHere INfrared survey for Exoplanets) and DISK (sphere survey for circumstellar DISK). SHINE aims to image 600 young nearby stars in the near-infrared using SPHERE’s high contrast and high angular resolution to discover and characterise new exoplanets and planetary systems. DISK explores known, young planetary systems and their circumstellar discs to study the initial conditions of planetary formation and the evolution of planetary architectures.

[2] In order to tease out the weak signal of the planet next to the bright star, astronomers use a sophisticated method that benefits from the Earth’s rotation. In this observing mode, SPHERE continuously takes images of the star over a period of several hours, while keeping the instrument as stable as possible. As a consequence, the planet appears to slowly rotate, changing its location on the image with respect to the stellar halo. Using elaborate numerical algorithms, the individual images are then combined in such a way that all parts of the image that appear not to move during the observation, such as the signal from the star itself, are filtered. This leaves only those that do apparently move — making the planet visible.

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TESS: First test image released from new exoplanet orbital observatory

The new exoplanet finder TESS tries out its camera and gets a shot of a whole lot of stars:

NASA’s New Planet Hunter Snaps Initial Test Image, Swings by Moon

This test image from one of the four cameras aboard the Transiting Exoplanet Survey Satellite (TESS) captures a swath of the southern sky along the plane of our galaxy. TESS is expected to cover more than 400 times the amount of sky shown in this image when using all four of its cameras during science operations. Credits: NASA/MIT/TESS

NASA’s next planet hunter, the Transiting Exoplanet Survey Satellite (TESS), is one step closer to searching for new worlds after successfully completing a lunar flyby on May 17. The spacecraft passed about 5,000 miles from the Moon, which provided a gravity assist that helped TESS sail toward its final working orbit.

As part of camera commissioning, the science team snapped a two-second test exposure using one of the four TESS cameras. The image, centered on the southern constellation Centaurus, reveals more than 200,000 stars. The edge of the Coalsack Nebula is in the right upper corner and the bright star Beta Centauri is visible at the lower left edge. TESS is expected to cover more than 400 times as much sky as shown in this image with its four cameras during its initial two-year search for exoplanets. A science-quality image, also referred to as a “first light” image, is expected to be released in June.

TESS will undergo one final thruster burn on May 30 to enter its science orbit around Earth. This highly elliptical orbit will maximize the amount of sky the spacecraft can image, allowing it to continuously monitor large swaths of the sky. TESS is expected to begin science operations in mid-June after reaching this orbit and completing camera calibrations.

Launched from Cape Canaveral Air Force Station in Florida on April 18, TESS is the next step in NASA’s search for planets outside our solar system, known as exoplanets. The mission will observe nearly the entire sky to monitor nearby, bright stars in search of transits — periodic dips in a star’s brightness caused by a planet passing in front of the star. TESS is expected to find thousands of exoplanets. NASA’s upcoming James Webb Space Telescope, scheduled for launch in 2020, will provide important follow-up observations of some of the most promising TESS-discovered exoplanets, allowing scientists to study their atmospheres.

TESS is a NASA Astrophysics Explorer mission led and operated by MIT in Cambridge, Massachusetts, and managed by NASA’s Goddard Space Flight Center in Greenbelt, Maryland. Dr. George Ricker of MIT’s Kavli Institute for Astrophysics and Space Research serves as principal investigator for the mission. Additional partners include Orbital ATK, based in Dulles, Virginia; NASA’s Ames Research Center in California’s Silicon Valley; the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts; and the Space Telescope Science Institute in Baltimore. The TESS science instruments were jointly developed by MIT’s Kavli Institute for Astrophysics and Space Research and MIT’s Lincoln Laboratory. More than a dozen universities, research institutes and observatories worldwide are participants in the mission.

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Hubble makes first observation of helium in the atmosphere of an exoplanet

Observations of planets around other stars continue to produce a steady stream of “firsts”:

Hubble Detects Helium in the Atmosphere of an Exoplanet for the First Time

Exoplanet WASP-107b is one of the lowest density planets known. While the planet is about the same size as Jupiter, it has only 12 percent of Jupiter’s mass. The exoplanet is about 200 light-years from Earth and takes less than six days to orbit its host star. Using infrared spectroscopy, scientists using NASA’s Hubble Space Telescope were able to find helium in the escaping atmosphere of the planet — the first detection of this element in the atmosphere of an exoplanet. [Artist’s rendering of WASP-107b transiting its star.]
Astronomers using NASA’s Hubble Space Telescope have detected helium in the atmosphere of the exoplanet WASP-107b. This is the first time this element has been detected in the atmosphere of a planet outside the solar system. The discovery demonstrates the ability to use infrared spectra to study exoplanet extended atmospheres.

The international team of astronomers, led by Jessica Spake, a PhD student at the University of Exeter in the UK, used Hubble’s Wide Field Camera 3 to discover helium in the atmosphere of the exoplanet WASP-107b. This is the first detection of its kind.

Spake explained the importance of the discovery:

“Helium is the second-most common element in the universe after hydrogen. It is also one of the main constituents of the planets Jupiter and Saturn in our solar system. However, up until now helium had not been detected on exoplanets — despite searches for it.”

The team made the detection by analyzing the infrared spectrum of the atmosphere of WASP-107b. Previous detections of extended exoplanet atmospheres have been made by studying the spectrum at ultraviolet and optical wavelengths; this detection therefore demonstrates that exoplanet atmospheres can also be studied at longer wavelengths.

The measurement of an exoplanet’s atmosphere is performed when the planet passes in front of its host star. A tiny portion of the star’s light passes through the exoplanet’s atmosphere, leaving detectable fingerprints in the spectrum of the star. The larger the amount of an element present in the atmosphere, the easier the detection becomes.

“The strong signal from helium we measured demonstrates a new technique to study upper layers of exoplanet atmospheres in a wider range of planets,” said Spake. “Current methods, which use ultraviolet light, are limited to the closest exoplanets. We know there is helium in the Earth’s upper atmosphere and this new technique may help us to detect atmospheres around Earth-sized exoplanets — which is very difficult with current technology.”

WASP-107b is one of the lowest density planets known: While the planet is about the same size as Jupiter, it has only 12 percent of Jupiter’s mass. The exoplanet is about 200 light-years from Earth and takes less than six days to orbit its host star.

The amount of helium detected in the atmosphere of WASP-107b is so large that its upper atmosphere must extend tens of thousands of miles out into space. This also makes it the first time that an extended atmosphere has been discovered at infrared wavelengths.

Since its atmosphere is so extended, the planet is losing a significant amount of its atmospheric gases into space — between about 0.1 percent to 4 percent of its atmosphere’s total mass every billion years.

Stellar radiation has a significant effect on the rate at which a planet’s atmosphere escapes. The star WASP-107 is highly active, supporting the atmospheric loss. As the atmosphere absorbs radiation it heats up, so the gas rapidly expands and escapes more quickly into space.

As far back as the year 2000, it was predicted that helium would be one of the most readily-detectable gases on giant exoplanets, but until now, searches were unsuccessful.

David Sing, co-author of the study also from the University of Exeter, concluded:

“Our new method, along with future telescopes such as NASA’s James Webb Space Telescope, will allow us to analyze atmospheres of exoplanets in far greater detail than ever before.”

The team’s study appears on May 2, 2018, in the online issue of science journal Nature.