NASA JPL presents a preview of highlights in the night sky in the coming month: What’s Up: April 2019 Skywatching from NASA | Solar System Exploration: NASA Science
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Category Archives: Astronomy
ESO: Optical interferometry reveals details of the atmosphere of an exoplanet
The latest report from ESO (European Southern Observatory):
GRAVITY instrument breaks new ground in exoplanet imaging
Cutting-edge VLTI instrument reveals details of a storm-wracked exoplanet
using optical interferometry
The GRAVITY instrument on ESO’s Very Large Telescope Interferometer (VLTI) has made the first direct observation of an exoplanet using optical interferometry. This method revealed a complex exoplanetary atmosphere with clouds of iron and silicates swirling in a planet-wide storm. The technique presents unique possibilities for characterising many of the exoplanets known today.
This result was announced today in a letter in the journal Astronomy and Astrophysics by the GRAVITY Collaboration [1], in which they present observations of the exoplanet HR8799e using optical interferometry. The exoplanet was discovered in 2010 orbiting the young main-sequence star HR8799, which lies around 129 light-years from Earth in the constellation of Pegasus.
Today’s result, which reveals new characteristics of HR8799e, required an instrument with very high resolution and sensitivity. GRAVITY can use ESO’s VLT’s four unit telescopes to work together to mimic a single larger telescope using a technique known as interferometry [2]. This creates a super-telescope — the VLTI — that collects and precisely disentangles the light from HR8799e’s atmosphere and the light from its parent star [3].
The HR 8799 system harbors four super-Jupiters orbiting with periods that range from decades to centuries. HR 8799e is the innermost planet in this video. This footage consists of 7 images of HR 8799 taken with the Keck Telescope over 7 years. The video was made by Jason Wang, data was reduced by Christian Marois, and the orbits were fit by Quinn Konopacky. Bruce Macintosh, Travis Barman, and Ben Zuckerman assisted in the observations.
HR8799e is a ‘super-Jupiter’, a world unlike any found in our Solar System, that is both more massive and much younger than any planet orbiting the Sun. At only 30 million years old, this baby exoplanet is young enough to give scientists a window onto the formation of planets and planetary systems. The exoplanet is thoroughly inhospitable — leftover energy from its formation and a powerful greenhouse effect heat HR8799e to a hostile temperature of roughly 1000 °C.
This is the first time that optical interferometry has been used to reveal details of an exoplanet, and the new technique furnished an exquisitely detailed spectrum of unprecedented quality — ten times more detailed than earlier observations. The team’s measurements were able to reveal the composition of HR8799e’s atmosphere — which contained some surprises.
“Our analysis showed that HR8799e has an atmosphere containing far more carbon monoxide than methane — something not expected from equilibrium chemistry,” explains team leader Sylvestre Lacour researcher CNRS at the Observatoire de Paris – PSL and the Max Planck Institute for Extraterrestrial Physics. “We can best explain this surprising result with high vertical winds within the atmosphere preventing the carbon monoxide from reacting with hydrogen to form methane.”
The team found that the atmosphere also contains clouds of iron and silicate dust. When combined with the excess of carbon monoxide, this suggests that HR8799e’s atmosphere is engaged in an enormous and violent storm.
“Our observations suggest a ball of gas illuminated from the interior, with rays of warm light swirling through stormy patches of dark clouds,” elaborates Lacour. “Convection moves around the clouds of silicate and iron particles, which disaggregate and rain down into the interior. This paints a picture of a dynamic atmosphere of a giant exoplanet at birth, undergoing complex physical and chemical processes.”
This result builds on GRAVITY’s string of impressive discoveries, which have included breakthroughs such as last year’s observation of gas swirling at 30% of the speed of light just outside the event horizon of the massive Black Hole in the Galactic Centre. It also adds a new way of observing exoplanets to the already extensive arsenal of methods available to ESO’s telescopes and instruments — paving the way to many more impressive discoveries [4].
Notes
[1] GRAVITY was developed by a collaboration consisting of the Max Planck Institute for Extraterrestrial Physics (Germany), LESIA of Paris Observatory–PSL / CNRS / Sorbonne Université / Univ. Paris Diderot and IPAG of Université Grenoble Alpes / CNRS (France), the Max Planck Institute for Astronomy (Germany), the University of Cologne (Germany), the CENTRA–Centro de Astrofisica e Gravitação (Portugal) and ESO.
[2] Interferometry is a technique that allows astronomers to create a super-telescope by combining several smaller telescopes. ESO’s VLTI is an interferometric telescope created by combining two or more of the Unit Telescopes (UTs) of the Very Large Telescope or all four of the smaller Auxiliary Telescopes. While each UT has an impressive 8.2-m primary mirror, combining them creates a telescope with 25 times more resolving power than a single UT observing in isolation.
[3] Exoplanets can be observed using many different methods. Some are indirect, such as the radial velocity method used by ESO’s exoplanet-hunting HARPS instrument, which measures the pull a planet’s gravity has on its parent star. Direct methods, like the technique pioneered for this result, involve observing the planet itself instead of its effect on its parent star.
[4] Recent exoplanet discoveries made using ESO telescopes include last year’s successful detection of a super-Earth orbiting Barnard’s Star, the closest single star to our Sun, and ALMA’s discovery of young planets orbiting an infant star, which used another novel technique for planet detection.
Links
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Video: “The Golden Age of Exoplanet Exploration”
At a public seminar at NASA JPL, Jessie Christiansen and Karl Stapelfeldt of Caltech and NASA talked about the exoplanets discoveries made thus far and those to be made by new observatories:
Since the discovery of the first exoplanet orbiting a sun-like star in 1995, several thousand more have been discovered. We’ve peered into the atmospheres of some, and we’ve found whole families of planets orbiting strange stars — many in configurations starkly different from our own. We’ve learned a lot from NASA’s Kepler mission, which launched 10 years ago and ceased operations in November 2018. A new NASA planet-hunting spacecraft called TESS, which began science operations as Kepler was winding down, will give us thousands of new discoveries in the coming years. And the Spitzer Space Telescope has provided us valuable insights into what these worlds might be like. This show will look at the state of exoplanet science and give us a view of what future discoveries may be around the corner.
This National Geo video gives a brief overview of exoplanets and how they are found and studied:
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Chasing New Horizons: Inside the Epic First Mission to Pluto
ESO: The Cosmic Bat of the Orion constellation
The latest ESO (European Southern Observatory) report:
A Cosmic Bat in Flight
ESO’s Cosmic Gems Programme captures the Cosmic Bat’s dusty clouds
Hidden in one of the darkest corners of the Orion constellation, this Cosmic Bat is spreading its hazy wings through interstellar space two thousand light-years away. It is illuminated by the young stars nestled in its core — despite being shrouded by opaque clouds of dust, their bright rays still illuminate the nebula. Too dim to be discerned by the naked eye, NGC 1788 reveals its soft colours to ESO’s Very Large Telescope in this image — the most detailed to date.
ESOcast 195 Light: A Cosmic Bat in Flight | ESO
ESO’s Very Large Telescope (VLT) has caught a glimpse of an ethereal nebula hidden away in the darkest corners of the constellation of Orion (The Hunter) — NGC 1788, nicknamed the Cosmic Bat. This bat-shaped reflection nebula doesn’t emit light — instead it is illuminated by a cluster of young stars in its core, only dimly visible through the clouds of dust. Scientific instruments have come a long way since NGC 1788 was first described, and this image taken by the VLT is the most detailed portrait of this nebula ever taken.
Even though this ghostly nebula in Orion appears to be isolated from other cosmic objects, astronomers believe that it was shaped by powerful stellar winds from the massive stars beyond it. These streams of scorching plasma are thrown from a star’s upper atmosphere at incredible speeds, shaping the clouds secluding the Cosmic Bat’s nascent stars.
NGC 1788 was first described by the German–British astronomer William Herschel, who included it in a catalogue that later served as the basis for one of the most significant collections of deep-sky objects, the New General Catalogue (NGC) [1]. A nice image of this small and dim nebula had already been captured by the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory, but this newly observed scene leaves it in the proverbial dust. Frozen in flight, the minute details of this Cosmic Bat’s dusty wings were imaged for the twentieth anniversary of one of ESO’s most versatile instruments, the FOcal Reducer and low dispersion Spectrograph 2 (FORS2).
FORS2 is an instrument mounted on Antu, one of the VLT’s 8.2-metre Unit Telescopes at the Paranal Observatory, and its ability to image large areas of the sky in exceptional detail has made it a coveted member of ESO’s fleet of cutting-edge scientific instruments. Since its first light 20 years ago, FORS2 has become known as “the Swiss army knife of instruments”. This moniker originates from its uniquely broad set of functions [2]. FORS2’s versatility extends beyond purely scientific uses — its ability to capture beautiful high-quality images like this makes it a particularly useful tool for public outreach.
This image was taken as part of ESO’s Cosmic Gems programme, an outreach initiative that uses ESO telescopes to produce images of interesting, intriguing or visually attractive objects for the purposes of education and public outreach. The programme makes use of telescope time that cannot be used for science observations, and — with the help of FORS2 — produces breathtaking images of some of the most striking objects in the night sky, such as this intricate reflection nebula. In case the data collected could be useful for future scientific purposes, these observations are saved and made available to astronomers through the ESO Science Archive.
Notes
[1] In 1864 John Herschel published the General Catalogue of Nebulae and Clusters, which built on extensive catalogues and contained entries for more than five thousand intriguing deep-sky objects. Twenty-four years later, this catalogue was expanded by John Louis Emil Dreyer and published as the New General Catalogue of Nebulae and Clusters of Stars (NGC), a comprehensive collection of stunning deep-sky objects.
[2] In addition to being able to image large areas of the sky with precision, FORS2 can also measure the spectra of multiple objects in the night sky and analyse the polarisation of their light. Data from FORS2 are the basis of over 100 scientific studies published every year.
More information
ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It has 16 Member States: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile and with Australia as a Strategic Partner. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its world-leading Very Large Telescope Interferometer as well as two survey telescopes, VISTA working in the infrared and the visible-light VLT Survey Telescope. Also at Paranal ESO will host and operate the Cherenkov Telescope Array South, the world’s largest and most sensitive gamma-ray observatory. ESO is also a major partner in two facilities on Chajnantor, APEX and ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre Extremely Large Telescope, the ELT, which will become “the world’s biggest eye on the sky”.
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Video: Night sky highlights for March 2019
Here is a preview of the night sky for March from NASA JPL: What’s Up: March 2019 Skywatching –
What can you see in the March sky? Jupiter and other planets in the morning, a change of seasons and an open star cluster called the Beehive.
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