Category Archives: Astronomy

Asteroids & Comets, Astronomy

ESO: “Exiled Asteroid Discovered in Outer Reaches of Solar System”

The latest news from ESO (European Southern Observatory):

Exiled Asteroid Discovered in Outer Reaches of Solar System

This artist’s impression shows the exiled asteroid 2004 EW95, the first carbon-rich asteroid confirmed to exist in the Kuiper Belt and a relic of the primordial Solar System. This curious object likely formed in the asteroid belt between Mars and Jupiter and must have been transported billions of kilometres from its origin to its current home in the Kuiper Belt. [Larger images]
An international team of astronomers has used ESO telescopes to investigate a relic of the primordial Solar System. The team found that the unusual Kuiper Belt Object 2004 EW95 is a carbon-rich asteroid, the first of its kind to be confirmed in the cold outer reaches of the Solar System. This curious object likely formed in the asteroid belt between Mars and Jupiter and has been flung billions of kilometres from its origin to its current home in the Kuiper Belt.

The early days of our Solar System were a tempestuous time. Theoretical models of this period predict that after the gas giants formed they rampaged through the Solar System, ejecting small rocky bodies from the inner Solar System to far-flung orbits at great distances from the Sun [1]. In particular, these models suggest that the Kuiper Belt — a cold region beyond the orbit of Neptune — should contain a small fraction of rocky bodies from the inner Solar System, such as carbon-rich asteroids, referred to as carbonaceous asteroids [2].

Now, a recent paper has presented evidence for the first reliably-observed carbonaceous asteroid in the Kuiper Belt, providing strong support for these theoretical models of our Solar System’s troubled youth. After painstaking measurements from multiple instruments at ESO’s Very Large Telescope (VLT), a small team of astronomers led by Tom Seccull of Queen’s University Belfast in the UK was able to measure the composition of the anomalous Kuiper Belt Object 2004 EW95, and thus determine that it is a carbonaceous asteroid. This suggests that it originally formed in the inner Solar System and must have since migrated outwards [3].

An international team of astronomers has used ESO telescopes to investigate a relic of the primordial Solar System. The team found that the unusual Kuiper Belt Object 2004 EW95 is a carbon-rich asteroid, the first of its kind to be confirmed in the cold outer reaches of the Solar System. The red line in this image shows the orbit of 2004 EW95, with the orbits of other Solar System bodies shown in green for comparison. [Larger images]
The peculiar nature of 2004 EW95 first came to light during routine observations with the NASA/ESA Hubble Space Telescope by Wesley Fraser, an astronomer from Queen’s University Belfast who was also a member of the team behind this discovery. The asteroid’s reflectance spectrum — the specific pattern of wavelengths of light reflected from an object — was different to that of similar small Kuiper Belt Objects (KBOs), which typically have uninteresting, featureless spectra that reveal little information about their composition.

“The reflectance spectrum of 2004 EW95 was clearly distinct from the other observed outer Solar System objects,” explains lead author Seccull. “It looked enough of a weirdo for us to take a closer look.”

The team observed 2004 EW95 with the X-Shooter and FORS2 instruments on the VLT. The sensitivity of these spectrographs allowed the team to obtain more detailed measurements of the pattern of light reflected from the asteroid and thus infer its composition.

However, even with the impressive light-collecting power of the VLT, 2004 EW95 was still difficult to observe. Though the object is 300 kilometres across, it is currently a colossal four billion kilometres from Earth, making gathering data from its dark, carbon-rich surface a demanding scientific challenge.

“It’s like observing a giant mountain of coal against the pitch-black canvas of the night sky,”

says co-author Thomas Puzia from the Pontificia Universidad Católica de Chile.

“Not only is 2004 EW95 moving, it’s also very faint,” adds Seccull. “We had to use a pretty advanced data processing technique to get as much out of the data as possible.”

Two features of the object’s spectra were particularly eye-catching and corresponded to the presence of ferric oxides and phyllosilicates. The presence of these materials had never before been confirmed in a KBO, and they strongly suggest that 2004 EW95 formed in the inner Solar System.

Seccull concludes:

“Given 2004 EW95’s  present-day abode in the icy outer reaches of the Solar System, this implies that it has been flung out into its present orbit by a migratory planet in the early days of the Solar System.”

[ Olivier Hainaut, an ESO astronomer who was not part of the team, comments, ]

“While there have been previous reports of other ‘atypical’ Kuiper Belt Object spectra, none were confirmed to this level of quality,” … “The discovery of a carbonaceous asteroid in the Kuiper Belt is a key verification of one of the fundamental predictions of dynamical models of the early Solar System.”

Notes

[1] Current dynamical models of the evolution of the early Solar System, such as the grand tack hypothesis and the Nice model, predict that the giant planets migrated first inward and then outward, disrupting and scattering objects from the inner Solar System. As a consequence, a small percentage of rocky asteroids are expected to have been ejected into orbits in the Oort Cloud and Kuiper belt.

[2] Carbonaceous asteroids are those containing the element carbon or its various compounds. Carbonaceous — or C-type — asteroids can be identified by their dark surfaces, caused by the presence of carbon molecules.

[3] Other inner Solar System objects have previously been detected in the outer reaches of the Solar System, but this is the first carbonaceous asteroid to be found far from home in the Kuiper Belt.

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Asteroids & Comets, Astronomy, Education

Video: Rubble Piles in the Sky – The Science, Exploration, and Danger of Near-Earth Asteroids

Dr. Michael Busch of the SETI Institute recently gave the following talk in the Silicon Valley Astronomy Lecture Series sponsored by the Astronomical Society of the Pacific:  Rubble Piles in the Sky: The Science, Exploration, and Danger of Near-Earth Asteroids –

Near-Earth asteroids are a population of small bodies whose orbits around the Sun cross or come near our planet’s orbit. They turn out to be unusual physical environments: essentially rubble piles. They represent a natural hazard we ignore at our peril, because some of these bodies have the potential to impact Earth. Dr. Busch reviews the near-Earth population, programs to track and characterize near-Earth asteroids, and current efforts to address the danger of asteroid impacts.

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Astronomy, Exoplanets

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.

Astronomy

Videos: Night sky highlights for May 2018

NASA JPL provides a list of the top sights in the night sky for May:

See also the Hubble Space Telescope Institute‘s May 2018 night sky preview:

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Asteroids & Comets, Astronomy, Space Science

New animation of Rosetta images shows a wild time on Comet 67P

In 2014 the European Space Agency’s Rosetta probe went into orbit around  Comet 67P/Churyumov–Gerasimenko and spent a couple of years studying it.  Jacint Roger Perez combined a series of 33 images made during a 25 minute period as the probe flew about 13 kilometers from the comet and the resulting time lapse creates the dramatic scene below:

Gif animation created by Jacint Roger Perez from Rosetta images of Comet 67P.

Although it looks like a blizzard, the white dots and streaks are a mix of stars in the dark background plus dust and ice particles,  as well as radiation going through the imager. The comet’s surface at the time was stirred up from the heat of the sun.

More about the animation and the Rossetta mission:

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