Category Archives: Astronomy

Astronomy

NASA/ESA Hubble: The awakened force of a star

NASA/ESA Hubble Space Telescope study finds a feature in the cosmos that comes at the right time:

The awakened force of a star

Perfectly timed for the release of “Star Wars Episode VII: The Force Awakens“, the NASA/ESA Hubble Space Telescope has imaged a cosmic double-bladed lightsabre. In the centre of the image, partially obscured by a dark Jedi-like cloak of dust, an adolescent star shoots twin jets out into space, demonstrating the fearsome forces of the Universe

The two lightsabre-like streams crossing the image are jets of energised gas, ejected from the poles of a young star. If the jets collide with the surrounding gas and dust they can clear vast spaces, and create curved shock waves, seen as knotted clumps called Herbig-Haro objects.
A cosmic light-sabre. The two lightsabre-like streams crossing the image are jets of energised gas, ejected from the poles of a young star. If the jets collide with the surrounding gas and dust they can clear vast spaces, and create curved shock waves, seen as knotted clumps called Herbig-Haro objects.

This celestial lightsabre lies not in a galaxy far, far away, but within our home galaxy, the Milky Way. More precisely, it resides within a turbulent patch of space known as the Orion B molecular cloud complex, which is located just over 1350 light-years away in the constellation of Orion (The Hunter).

Bearing a striking resemblance to Darth Maul’s double-bladed lightsabre in Star Wars Episode One, the spectacular twin jets of material slicing across this incredible image are spewing out from a newly formed star that is obscured from view, cloaked by swirling dust and gas.

Zooming on HH 24: This video begins with a ground-based view of the night sky, before zooming on the knotted clumps of gas that make up the Herbig–Haro object 24, as the NASA/ESA Hubble Space Telescope sees it. Credit: ESA/Hubble, NASA, Digitized Sky Survey, N. Risinger (skysurvey.org). Music: Johan B Monell

When stars form within giant, gaseous clouds, some of the surrounding material collapses down to form a rotating, flattened disc encircling the nascent stars, which are known as protostars. This disc is where a potential planetary system might form. However, at this early stage, the star is mostly concerned with feeding its Jabba-like appetite. Gas from the disc rains down onto the protostar and, once nourished, the star awakens and jets of energised gas from its poles whirl out in opposite directions.

This image shows the Herbig–Haro object 24 and the surrounding sky as it is seen from the ground.
HH 24 (Ground-based view). This image shows the Herbig–Haro object 24 and the surrounding sky as it is seen from the ground.

The Force is strong with these twin jets; their effect on their environment demonstrates the true power of the Dark Side with a blast stronger than one from a fully armed and operational Death Star battle station. As they stream away from one another at high speeds, supersonic shock fronts develop along the jets and heat the surrounding gas to thousands of degrees.

Furthermore, as the jets collide with the surrounding gas and dust and clear vast spaces, they create curved shock waves. These shockwaves are the hallmarks of Herbig-Haro (HH) objects — tangled, knotted clumps of nebulosity. The prominent Herbig-Haro object shown in this image is HH 24.

Just to the right of the cloaked star, a couple of bright points of light can be seen. These are young stars peeking through and showing off their own faint lightsabres. One hidden, cloaked source, only detectable in the radio part of the spectrum, has blasted a tunnel through the dark cloud in the upper left of the image with a wider outflow resembling “force lightning”.

Panning across HH 24: This video pans over NASA/ESA Hubble Space Telescope observations of the Herbig-Haro object 24. The two energetic jets as well as the dozens of knots of clumped gas are clearly visible. Credit: ESA/Hubble Music: Johan B Monell

All these jets make HH 24 the densest concentration of HH jets known in such a small region. Half of the HH jets have been spotted in this region in visible light, and about the same number in the infrared. Hubble’s observations for this image were performed in infrared light, which enabled the telescope to pierce through the gas and dust cocooning the newly-forming stars and capture a clear view of the HH objects that astronomers are looking for.

The stellar jets of HH 24 in 3D: This movie envisions a three-dimensional perspective on the Herbig-Haro object as it is seen by the NASA/ESA Hubble Space Telescope.

The sequence starts with a wide-field view covering the vast dark cloud of the Orion B molecular cloud complex and a scattering of stars. As the virtual camera flies into the dark nebula, the stars pass off-screen and the details of the forming stars and their red jets are revealed.

While the central star is hidden, its lightsabre-like jets peak out of the gas and dust. These jets have carved an hourglass-shaped cavity in the near side of the nebula.

The jet from another stellar newborn in this region has created a cylindrical tunnel through the gas extending to the left. Careful study of the Hubble data reveals a few other jets heating and displacing the gas and dust around them.

Astronomy

ESO: ALMA antennas find signs of new planets in discs around young stars

A new report from ESO (European Southern Observatory):

ALMA Reveals Planetary Construction Sites
New evidence for young planets in discs around young stars

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found the clearest indications yet that planets with masses several times that of Jupiter have recently formed in the discs of gas and dust around four young stars. Measurements of the gas around the stars also provide additional clues about the properties of those planets.

Artist’s impression of a transitional disc around a young star. Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found telltale differences between the gaps in the gas and the dust in discs around four young stars. These new observations are the clearest indications yet that planets with masses several times that of Jupiter have recently formed in these discs.
Artist’s impression of a transitional disc around a young star. Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found telltale differences between the gaps in the gas and the dust in discs around four young stars. These new observations are the clearest indications yet that planets with masses several times that of Jupiter have recently formed in these discs. Credit: ALMA (ESO/NAOJ/NRAO)/M. Kornmesser

Planets are found around nearly every star, but astronomers still do not fully understand how — and under what conditions — they form. To answer such questions, they study the rotating discs of gas and dust present around young stars from which planets are built. But these discs are small and far from Earth, and the power of ALMA was needed for them to reveal their secrets.

Schematic view of a transitional disc around a young star. Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found telltale differences between the gaps in the gas and the dust in discs around four young stars. These new observations are the clearest indications yet that planets with masses several times that of Jupiter have recently formed in these discs. This schematic diagram shows how the dust (brown) and gas (blue) is distributed around the star, and how a young planet is clearing the central gap.
Schematic view of a transitional disc around a young star. Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found telltale differences between the gaps in the gas and the dust in discs around four young stars. These new observations are the clearest indications yet that planets with masses several times that of Jupiter have recently formed in these discs. This schematic diagram shows how the dust (brown) and gas (blue) is distributed around the star, and how a young planet is clearing the central gap.

A special class of discs, called transitional discs, have a surprising absence of dust in their centres, in the region around the star. Two main ideas have been put forward to explain these mysterious gaps. Firstly, the strong stellar winds and intense radiation could have blown away or destroyed the encircling material [1]. Alternatively, massive young planets in the process of formation could have cleared the material as they orbit the star [2].

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found telltale differences between the gaps in the gas and the dust in discs around four young stars. These new observations are the clearest indications yet that planets with masses several times that of Jupiter have recently formed in these discs. Credit: ALMA (ESO/NAOJ/NRAO)/M. Kornmesser

The unparalleled sensitivity and image sharpness of ALMA have now allowed the team of astronomers, led by Nienke van der Marel from the Leiden Observatory in the Netherlands to map the distribution of gas and dust in four of these transitional discs better than ever before [3]. This in turn has allowed them to choose between the two options as the cause of the gaps for the first time.

ALMA imaging of the transitional disc HD 135344B. This ALMA image combines a view of the dust around the young star HD 135344B (orange) with a view of the gaseous material (blue). The smaller hole in the inner gas is a telltale sign of the presence of a young planet clearing the disc. The bar at the bottom of the image indicates the diameter of the orbit of Neptune in the Solar System (60 AU).
ALMA imaging of the transitional disc HD 135344B. This ALMA image combines a view of the dust around the young star HD 135344B (orange) with a view of the gaseous material (blue). The smaller hole in the inner gas is a telltale sign of the presence of a young planet clearing the disc. The bar at the bottom of the image indicates the diameter of the orbit of Neptune in the Solar System (60 AU).

The new images show that there are significant amounts of gas within the dust gaps [4]. But to the team’s surprise, the gas also possessed a gap, up to three times smaller than that of the dust.

Astronomers using the Atacama Large Millimeter/submillimeter Array (ALMA) have found telltale differences between the gaps in the gas and the dust in discs around four young stars. These new observations are the clearest indications yet that planets with masses several times that of Jupiter have recently formed in these discs. Credit: ALMA (ESO/NAOJ/NRAO)/M. Kornmesser

This could only be explained by the scenario in which newly formed massive planets have cleared the gas as they travelled around their orbits, but trapped the dust particles further out [5].

“Previous observations already hinted at the presence of gas inside the dust gaps,” explains Nienke van der Marel. “But as ALMA can image the material in the entire disc in much greater detail than other facilities, we could rule out the alternative scenario. The deep gap points clearly to the presence of planets with several times the mass of Jupiter, creating these caverns as they sweep through the disc.”

Remarkably, these observations were conducted utilising just one tenth of the current resolving power of ALMA, as they were performed whilst half of the array was still under construction on the Chajnantor Plateau in northern Chile.

ALMA imaging of the transitional disc DoAr 44. This ALMA image combines a view of the dust around the young star DoAr 44 (orange) with a view of the gaseous material (blue). The smaller hole in the inner gas is a telltale sign of the presence of a young planet clearing the disc. The bar at the bottom of the image indicates the diameter of the orbit of Neptune in the Solar System (60 AU).
ALMA imaging of the transitional disc DoAr 44. This ALMA image combines a view of the dust around the young star DoAr 44 (orange) with a view of the gaseous material (blue). The smaller hole in the inner gas is a telltale sign of the presence of a young planet clearing the disc. The bar at the bottom of the image indicates the diameter of the orbit of Neptune in the Solar System (60 AU).

Further studies are now needed to determine whether more transitional discs also point towards this planet-clearing scenario, although ALMA’s observations have, in the meantime, provided astronomers with a valuable new insight into the complex process of planetary formation.

“All the transitional discs studied so far that have large dust cavities also have gas cavities. So, with ALMA, we can now find out where and when giant planets are being born in these discs, and compare these results with planet formation models,” says Ewine van Dishoeck, also of Leiden University and the Max Planck Institute for Extraterrestrial Physics in Garching [6]. “Direct planetary detection is just within reach of current instruments, and the next generation telescopes currently under construction, such as the European Extremely Large Telescope, will be able to go much further. ALMA is pointing out where they will need to look.”

Notes

[1] This process, which clears the dust and gas from the inside out, is known as photoevaporation.

[2] Such planets are difficult to observe directly (eso1310) and previous studies at millimetre wavelengths (eso1325) have failed to achieve a sharp view of their inner, planet-forming zones where these different explanations could be put to the test. Other studies (eso0827) could not measure the bulk of the gas in these discs.

[3] The four targets of these investigations were SR 21, HD 135344B (also known as SAO 206462), DoAr 44 and Oph IRS 48.

[4] The gas present in transitional discs consists primarily of hydrogen, and is traced through observations of the carbon monoxide — or CO — molecule.

[5] The process of dust trapping is explained in an earlier release (eso1325).

[6] Other examples include the HD 142527 (eso1301 and here) and J1604-2130 transitional discs.

Astronomy, Exoplanets

ESA/Hubble: Study of 10 exo-Jupiter planets finds where the water is hiding

A report from the ESA/Hubble team:

Hubble reveals diversity of exoplanet atmospheres
Largest ever comparative study solves missing water mystery

Astronomers have used the NASA/ESA Hubble Space Telescope and the NASA Spitzer Space Telescope to study the atmospheres of ten hot, Jupiter-sized exoplanets in detail, the largest number of such planets ever studied. The team was able to discover why some of these worlds seem to have less water than expected — a long-standing mystery. The results are published in “Nature”.

This image shows an artist’s impression of the ten hot Jupiter exoplanets studied by David Sing and his colleagues. From top left to to lower left these planets are WASP-12b, WASP-6b, WASP-31b, WASP-39b, HD 189733b, HAT-P-12b, WASP-17b, WASP-19b, HAT-P-1b and HD 209458b. The images are to scale with each other. HAT-P-12b, the smallest of them, is approximately the size of Jupiter, while WASP-17b, the largest planet in the sample, is almost twice the size. The planets are also depicted with a variety of different cloud properties. There is almost no information about the colours of the planets available, with the exception of HD 189733b, which became known as the blue planet (heic1312). The hottest planets within the sample are portrayed with a glowing night side. This effect is strongest on WASP-12b, the hottest exoplanet in the sample, but also visible on WASP-19b and WASP-17b. It is also known that several of the planets exhibit strong Rayleigh scattering. This effect causes the blue hue of the daytime sky and the reddening of the Sun at sunset on Earth. It is also visible as a blue edge on the planets WASP-6b, HD 189733b, HAT-P-12b, and HD 209458b. The wind patterns shown on these ten planets, which resemble the visible structures on Jupiter, are based on theoretical models.
This image shows an artist’s impression of the ten hot Jupiter exoplanets studied by David Sing and his colleagues. From top left to to lower left these planets are WASP-12b, WASP-6b, WASP-31b, WASP-39b, HD 189733b, HAT-P-12b, WASP-17b, WASP-19b, HAT-P-1b and HD 209458b. The images are to scale with each other. HAT-P-12b, the smallest of them, is approximately the size of Jupiter, while WASP-17b, the largest planet in the sample, is almost twice the size. The planets are also depicted with a variety of different cloud properties. There is almost no information about the colours of the planets available, with the exception of HD 189733b, which became known as the blue planet (heic1312). The hottest planets within the sample are portrayed with a glowing night side. This effect is strongest on WASP-12b, the hottest exoplanet in the sample, but also visible on WASP-19b and WASP-17b. It is also known that several of the planets exhibit strong Rayleigh scattering. This effect causes the blue hue of the daytime sky and the reddening of the Sun at sunset on Earth. It is also visible as a blue edge on the planets WASP-6b, HD 189733b, HAT-P-12b, and HD 209458b. The wind patterns shown on these ten planets, which resemble the visible structures on Jupiter, are based on theoretical models. [Annotated image]
To date, astronomers have discovered nearly 2000 planets orbiting other stars. Some of these planets are known as hot Jupiters — hot, gaseous planets with characteristics similar to those of Jupiter. They orbit very close to their stars, making their surface hot, and the planets tricky to study in detail without being overwhelmed by bright starlight.

Due to this difficulty, Hubble has only explored a handful of hot Jupiters in the past, across a limited wavelength range. These initial studies have found several planets to hold less water than expected (opo1436a, opo1354a).

This video shows an artist’s impression of the ten hot Jupiter exoplanets studied by David Sing and his colleagues. From top left to to lower left these planets are WASP-12b, WASP-6b, WASP-31b, WASP-39b, HD 189733b, HAT-P-12b, WASP-17b, WASP-19b, HAT-P-1b and HD 209458b…

Now, an international team of astronomers has tackled the problem by making the largest ever study of hot Jupiters, exploring and comparing ten such planets in a bid to understand their atmospheres [1]. Only three of these planetary atmospheres had previously been studied in detail; this new sample forms the largest ever spectroscopic catalogue of exoplanet atmospheres.

The team used multiple observations from both the NASA/ESA Hubble Space Telescope and NASA’s Spitzer Space Telescope. Using the power of both telescopes allowed the team to study the planets, which are of various masses, sizes, and temperatures, across an unprecedented range of wavelengths [2].

“I’m really excited to finally ‘see’ this wide group of planets together, as this is the first time we’ve had sufficient wavelength coverage to be able to compare multiple features from one planet to another,” says David Sing of the University of Exeter, UK, lead author of the new paper. “We found the planetary atmospheres to be much more diverse than we expected.”

All of the planets have a favourable orbit that brings them between their parent star and Earth. As the exoplanet passes in front of its host star, as seen from Earth, some of this starlight travels through the planet’s outer atmosphere. “The atmosphere leaves its unique fingerprint on the starlight, which we can study when the light reaches us,” explains co-author Hannah Wakeford, now at NASA Goddard Space Flight Center, USA.

These fingerprints allowed the team to extract the signatures from various elements and molecules — including water — and to distinguish between cloudy and cloud-free exoplanets, a property that could explain the missing water mystery.

The team’s models revealed that, while apparently cloud-free exoplanets showed strong signs of water, the atmospheres of those hot Jupiters with faint water signals also contained clouds and haze — both of which are known to hide water from view. Mystery solved!

“The alternative to this is that planets form in an environment deprived of water — but this would require us to completely rethink our current theories of how planets are born,” explained co-author Jonathan Fortney of the University of California, Santa Cruz, USA. “Our results have ruled out the dry scenario, and strongly suggest that it’s simply clouds hiding the water from prying eyes.”

The study of exoplanetary atmospheres is currently in its infancy, with only a handful of observations taken so far. Hubble’s successor, the James Webb Space Telescope, will open a new infrared window on the study of exoplanets and their atmospheres.

Notes

[1] To date, studies of exoplanet atmospheres have been dominated by a small number of well-studied planets. The team used Hubble and Spitzer observations of two such planets, HD 209458b (heic0303, opo0707b) and HD 189733b (heic1312, heic0720a), and used Hubble to observe eight other exoplanets — WASP-6b, WASP-12b, WASP-17b, WASP-19b, WASP-31b, WASP-39b, HAT-P-1b, HAT-P-12b. These planets have a broad range of physical parameters.

[2] The observations spanned from the ultraviolet (0.3 μm) to the mid-infrared (4.5 μm).

Astronomy

ESO: A young dwarf galaxy emerges from the debris of a cosmic collision

The latest report from the ESO (European Southern Observatory):

VLT Revisits a Curious Cosmic Collision

The spectacular aftermath of a 360 million year old cosmic collision is revealed in great detail in new images from ESO’s Very Large Telescope at the Paranal Observatory. Among the debris is a rare and mysterious young dwarf galaxy. This galaxy is providing astronomers with an excellent opportunity to learn more about similar galaxies that are expected to be common in the early Universe, but are normally too faint and distant to be observed by current telescopes.

The spectacular aftermath of a 360 million year old cosmic collision is revealed in great detail in this image from ESO’s Very Large Telescope at the Paranal Observatory. Among the debris surrounding the elliptical galaxy NGC 5291 at the centre is a rare and mysterious young dwarf galaxy, which appears as a bright clump towards the right of the image. This object is providing astronomers with an excellent opportunity to learn more about similar galaxies that are expected to be common in the early Universe, but are normally too faint and distant to be observed by current telescopes.
The spectacular aftermath of a 360 million year old cosmic collision is revealed in great detail in this image from ESO’s Very Large Telescope at the Paranal Observatory. Among the debris surrounding the elliptical galaxy NGC 5291 at the centre is a rare and mysterious young dwarf galaxy, which appears as a bright clump towards the right of the image. This object is providing astronomers with an excellent opportunity to learn more about similar galaxies that are expected to be common in the early Universe, but are normally too faint and distant to be observed by current telescopes.

NGC 5291, the hazy, golden oval dominating the centre of this image, is an elliptical galaxy located nearly 200 million light-years away in the constellation of Centaurus (The Centaur). Over 360 million years ago, NGC 5291 was involved in a dramatic and violent collision as another galaxy travelling at immense speeds barrelled into its core. The cosmic crash ejected huge streams of gas into nearby space, which later coalesced into a ring formation around NGC 5291 [1].

The spectacular aftermath of a 360 million year old cosmic collision is revealed in great detail in this image from ESO’s Very Large Telescope at the Paranal Observatory. Among the debris surrounding the elliptical galaxy NGC 5291 at the centre is a rare and mysterious young dwarf galaxy known as NGC 5291N. It is providing astronomers with an excellent opportunity to learn more about similar galaxies that are expected to be common in the early Universe, but are normally too faint and distant to be observed by current telescopes.
The spectacular aftermath of a 360 million year old cosmic collision is revealed in great detail in this image from ESO’s Very Large Telescope at the Paranal Observatory. Among the debris surrounding the elliptical galaxy NGC 5291 at the centre is a rare and mysterious young dwarf galaxy known as NGC 5291N. It is providing astronomers with an excellent opportunity to learn more about similar galaxies that are expected to be common in the early Universe, but are normally too faint and distant to be observed by current telescopes.

Over time, material in this ring gathered and collapsed into dozens of star-forming regions and several dwarf galaxies, revealed as pale blue and white regions scattered around NGC 5291 in this new image from the FORS instrument, mounted on the VLT. The most massive and luminous clump of material, to the right of NGC 5291, is one of these dwarf galaxies and is known as NGC 5291N.

This chart shows the location of the interacting galaxy system NGC 5291 in the bright southern constellation of Centaurus. Most of the stars visible with the naked eye on a dark clear moonless night are shown and the location of the galaxy is marked with a red circle. NGC 5291 can be seen as a faint fuzzy spot through larger amateur telescopes.
This chart shows the location of the interacting galaxy system NGC 5291 in the bright southern constellation of Centaurus. Most of the stars visible with the naked eye on a dark clear moonless night are shown and the location of the galaxy is marked with a red circle. NGC 5291 can be seen as a faint fuzzy spot through larger amateur telescopes. Credit ESO, IAU, Sky & Telescope

The Milky Way, like all large galaxies, is believed to have formed through the build-up of smaller dwarf galaxies in the early years of the Universe. These small galaxies, if they have survived on their own up to the present day, now normally contain many extremely old stars.

Yet NGC 5291N appears to contain no old stars. Detailed observations with the MUSE spectrograph [2] also found that the outer parts of the galaxy had properties typically associated with the formation of new stars, but what was observed is not predicted by current theoretical models. Astronomers suspect that these unusual aspects may be the result of massive collisions of gas in the region.

This video takes us from a broad view of the southern Milky Way deep into the large constellation of Centaurus. The sequence ends with a close-up view from ESO’s Very Large Telescope of an interacting galaxy called NGC 5291, about 200 million light-years from Earth. Credit: ESO/Digitized Sky Survey 2/N. Risinger (skysurvey.org)

NGC 5291N doesn’t look like a typical dwarf galaxy, but instead it shares a striking number of similarities with the clumpy structures present within many of the star-forming galaxies in the distant Universe. This makes it a unique system in our local Universe and an important laboratory for the study of early gas-rich galaxies, which are normally much too distant to be observed in detail by current telescopes.

This close-up pan video shows the spectacular aftermath of a 360 million year old cosmic collision, as revealed in great detail in an image from ESO’s Very Large Telescope at the Paranal Observatory. Among the debris surrounding the elliptical galaxy NGC 5291 is a rare and mysterious young dwarf galaxy. It is providing astronomers with an excellent opportunity to learn more about similar galaxies that are expected to be common in the early Universe, but are normally too faint and distant to be observed by current telescopes. Credit: ESO/Digitized Sky Survey 2/N. Risinger (skysurvey.org)

This unusual system has previously been observed by a wide range of ground-based facilities, including ESO’s 3.6-metre telescope at the La Silla Observatory [3]. However, the capabilities of MUSE, FORS and the Very Large Telescope have only now allowed some of the history and properties of NGC 5291N to be determined.

This wide-field view shows the sky around the galaxy NGC 5291. This system has interacted with other galaxies and is surrounded with debris from earlier encounters. Some of this material is now forming dwarf galaxies rich in young stars. This picture was created from images forming part of the Digitized Sky Survey 2. Many other galaxies are also visible.
This wide-field view shows the sky around the galaxy NGC 5291. This system has interacted with other galaxies and is surrounded with debris from earlier encounters. Some of this material is now forming dwarf galaxies rich in young stars. This picture was created from images forming part of the Digitized Sky Survey 2. Many other galaxies are also visible. Credit: ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin

Future observations, including those by ESO’s European Extremely Large Telescope (E-ELT), may allow astronomers to further unravel this dwarf galaxy’s remaining mysteries.

Notes

[1] NGC 5291 is currently also interacting more gently with MCG-05-33-005 — or the Seashell Galaxy — the unusual comma-shaped galaxy appearing to leech off NGC 5291’s luminous core.

[2] NGC 5291N was observed using integral field spectrography during MUSE’s first Science Verification run. Integral field spectrography collects a spectrum at every point on the sky, providing a powerful three-dimensional view of the target. The MUSE observations revealed unexpected oxygen and hydrogen emission lines in the outskirts of NGC 5291N.

[3] NGC 5291 was studied by astronomers using ESO’s 3.6-metre telescope at the La Silla Observatory back in 1978. These observations revealed large amounts of material in the intergalactic space around the galaxy, which we now know to be the star-forming regions and several dwarf galaxies created from the collapse of the galaxy’s gaseous ring.

Astronomy, Education, Multiple media

Video: “In the land of Enchantment: The Epic Story of the Cassini Mission to Saturn”

The Silicon Valley Astronomy Lectures are sponsored by Foothill College, “in the heart of California’s Silicon Valley”. The “speakers over the years have included a wide range of noted scientists, explaining astronomical developments in everyday language”. More than 40 of the lectures are available on line in the archive at SVAstronomyLectures – YouTube.

In the most recent lecture, Dr. Carolyn Porco, the Imaging Team Leader for the Cassini mission to Saturn, showed

many of the magnificent mission images and explain the findings from both the main orbiter and the probe that landed on Titan, Saturn’s biggest moon. She also discusses the geysers on the moon Enceladus and what we have learned about the plumes that erupt.