Watching the Wavemaker

NASA & ESA - Cassini-Huygens Mission to Saturn & Titan patch.

Dec. 13, 2016

Saturn's moon Daphnis raises waves wherever it goes. In fact, such waves are one way that scientists search for undiscovered moons in the ring gaps. But they can tell researchers a lot of other things, as well.

The waves that Daphnis (5 miles or 8 kilometers across) raises on the edges of the Keeler Gap can also be used to deduce the moon's mass and even some of its orbital behavior. Since the moon moves in and out of the ring-plane, and closer to and farther from the rings' edges as it orbits, the waves it makes change over time. Cassini has been observing these changes during its extended study of the Saturn system to help understand this interaction.

For more about the effects of the vertical motion of Daphnis, see PIA11656 (link bellow).

This view looks toward the sunlit side of the rings from about 35 degrees above the ring plane. The image was taken in visible light with the Cassini spacecraft narrow-angle camera on Oct. 10, 2016.

Daphnis has been brightened by a factor of two in this image to increase its visibility.

The view was obtained at a distance of approximately 810,000 miles (1.3 million kilometers) from Daphnis and at a Sun-Daphnis-spacecraft, or phase, angle of 96 degrees. Image scale is 5 miles (8 kilometers) per pixel.

The Cassini mission is a cooperative project of NASA, ESA (the European Space Agency) and the Italian Space Agency. The Jet Propulsion Laboratory, a division of the California Institute of Technology in Pasadena, manages the mission for NASA's Science Mission Directorate, Washington. The Cassini orbiter and its two onboard cameras were designed, developed and assembled at JPL. The imaging operations center is based at the Space Science Institute in Boulder, Colorado.

Related link:

PIA11656: http://photojournal.jpl.nasa.gov/catalog/PIA11656

For more information about the Cassini-Huygens mission visit http://saturn.jpl.nasa.gov and http://www.nasa.gov/cassini. The Cassini imaging team homepage is at http://ciclops.org and ESA's website http://www.esa.int/Our_Activities/Space_Science/Cassini-Huygens

Image, Text, Credits: NASA/JPL-Caltech/Space Science Institute/Tony Greicius.

Greetings, Orbiter.ch

Two Astronauts Capture Japanese “White Stork”

JAXA -  H-IIB Launch Vehicle No. 6 & (HTV-6) KOUNOTORI-6 Mission patch.

December 13, 2016

Image above: Japan’s HTV-6 cargo craft is pictured in the grip of the Canadarm2 shortly after it was captured Tuesday morning. Image Credit: NASA TV.

Using the International Space Station’s robotic arm, Canadarm2, Expedition 50 Commander Shane Kimbrough of NASA and Flight Engineer Thomas Pesquet of ESA (European Space Agency) successfully captured the Japan Aerospace Exploration Agency’s Kounotori H-II Transfer Vehicle (HTV-6). At the time of capture, the space station and cargo spacecraft were flying 250 miles over southern Chile. Robotic ground controllers now will install it on the Earth-facing side of the Harmony module.

NASA TV coverage of the berthing currently is scheduled to begin about 7:45 a.m. at http://www.nasa.gov/nasatv.

The Japanese cargo ship, whose name means “white stork,” is delivering more than 4.5 tons of supplies, water, spare parts and experiment hardware for the six-person station crew.

Japanese Cargo Ship Arrives at the International Space Station

The re-supply vehicle is delivering six new lithium-ion batteries and adapter plates that will replace the nickel-hydrogen batteries currently used on the station to store electrical energy generated by the station’s solar arrays. These will be installed during a series of robotic operations and spacewalks between late December and mid-January.

The spacecraft also is bringing the Technology Education (TechEdSat-5) nanosatellite, which includes the Exo-Brake technology demonstration mission. The Exo-Brake technology is a tension-based, flexible braking device that could help bring small payloads back through Earth’s atmosphere unharmed, accurately de-orbiting through a series of adjustments to modulate drag. Exo-Brake deployment is targeted for early 2017.

Follow the conversation on Twitter via @Space_Station. To learn more about all the ways to connect and collaborate with NASA, visit: http://www.nasa.gov/connect

For more information on previous HTV missions from JAXA to the space station visit:

    https://www.nasa.gov/feature/kounotori-htv-launches-arrivals-and-departures
    https://www.flickr.com/photos/nasa2explore/albums/72157657507783606

Related article:

Launch success of the H-IIB Launch Vehicle No. 6 (H-IIB F6) HTV-6
http://orbiterchspacenews.blogspot.ch/2016/12/launch-success-of-h-iib-launch-vehicle.html

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

Image (mentioned), Video (NASA TV), Text, Credits: NASA/Mark Garcia.

Best regards, Orbiter.ch

LISA Pathfinder's pioneering mission continues

ESA - LISA Pathfinder Mission patch.

13 December 2016

On 7 December, LISA Pathfinder started the extended phase of its mission, an additional six months during which scientists and engineers will push the experiment to its limits in preparation for ESA's future space observatory of gravitational waves.

LISA Pathfinder, a demonstration mission to validate important technologies to observe gravitational waves – fluctuations in the fabric of spacetime – from space, was launched just over a year ago, on 3 December 2015.

LISA Pathfinder operations. Image Credits: ESA/C. Carreau.

After a six-week-long journey, the spacecraft reached its operational orbit around the first Sun-Earth Lagrange point, L1 – 1.5 million km away from Earth towards the Sun – at the end of January. There, following commissioning of the on board instrumentation, LISA Pathfinder started its science mission on 1 March.

Much to the team's surprise, it did not take as long as expected to achieve the mission's goal: demonstrating that two test masses – a pair of identical gold-platinum cubes – can be placed in the most precise freefall ever performed. In fact, the desired level of precision was already obtained within the first day of LISA Pathfinder's scientific operations.

Over the following months, scientists and engineers kept improving the performance of the experiment. They described these first results, including an analysis of the residual sources of disturbance on the cubes' almost perfect freefall motion, in a paper published at the beginning of June in Physical Review Letters.

Then, on 25 June, the first operations phase, using the LISA Technology Package (LTP), was completed. The LTP is a European payload consisting of the test masses, inertial sensors, and laser interferometer, and uses a series of cold-gas micronewton thrusters to move the satellite and keep it centred on the cubes, in response to external and internal forces battering them around.

Image above: LISA Pathfinder performance. Image Credits: spacecraft: ESA/ATG medialab; data: ESA/LISA Pathfinder Collaboration.

Operations continued with NASA's Disturbance Reduction System (DRS), an additional experiment which receives measurement input from the inertial sensors of the LTP but employs its own micronewton thrusters based on colloidal technology.

Following completion of the DRS operations, the extended mission of LISA Pathfinder began on 7 December 2016, at 09:00 CET (08:00 UTC). It will last until 31 May 2017, making use of both the LTP and DRS payloads.

"So far, we've been busy demonstrating the performance of LISA Pathfinder, which has been steadily improving as time went by," says Paul McNamara, LISA Pathfinder Project Scientist at ESA, "but now we can spend the next six months learning everything we need to know to build and operate a gravitational-wave observatory in space."

Last October, ESA issued a call inviting European scientists to propose concepts for the third large mission (L3) in its Cosmic Vision plan, which will be a space observatory to study the gravitational Universe. The selection is expected to take place in the first half of 2017, with a preliminary internal study phase planned for later in the year.

The future observatory will detect gravitational waves with frequencies from 1 Hz down to 0.1 mHz. These are about a hundred to a million times lower than the frequencies of waves that can be measured with ground-based experiments like the Laser Interferometer Gravitational-Wave Observatory (LIGO), which obtained the first direct detection of gravitational waves in September 2015.

Image above: Artist's impression of a pair of merging black holes, releasing gravitational waves. Image Credits: ESA–C.Carreau.

During the extended mission of LISA Pathfinder, the team will run a series of long duration experiments to better characterise the mission performance especially at the lowest frequencies that will be probed by the future observatory.

"We are thrilled to be pushing the limits of LISA Pathfinder, a unique physics laboratory in space giving us confidence that we can definitely build a space-borne observatory of gravitational waves", says Oliver Jennrich, LISA Pathfinder deputy mission scientist and L3 study scientist at ESA.

One of the operations that will be attempted in the coming weeks concerns the station-keeping manoeuvres that mission operators have been regularly conducting to keep the satellite on its operational orbit.

LISA Pathfinder orbits around L1, but if left unattended, it would slowly drift away from the Lagrangian point under the gravitational pull of Earth. To avoid that, it is sufficient to fire the micro-newton thrusters once every one to two weeks.

Between 25 December and 14 January, however, the team decided to apply no correction manoeuvres. This will allow the scientists to run uninterrupted experiments for almost three weeks, exploring what happens in the range of very low frequencies that are of interest to detect gravitational wave from space.



Image above: The LISA Technology Package core assembly at the heart of LISA Pathfinder. Image Credits: ESA/ATG medialab.

Another experiment concerns slightly higher frequencies, around 1–60 mHz. At these frequencies, the main source of disturbance seems to be gas molecules that are present in the test mass enclosures and bouncing off the two cubes – an effect that has been reducing as more molecules are being vented into space.

The team is now curious to see whether additional sources of noise are lurking underneath, something that will be important for the future L3 mission. One possible way of testing this entails simply waiting until most molecules are vented into space, but there is an alternative: to switch off many of the heaters on board, reducing the temperature by ten degrees, and thereby reducing the pressure inside the enclosure. The team will run this experiment in late January.

These are some examples of the range of experiments that will be conducted during LISA Pathfinder's extended mission. Eventually, at the end of the mission, the spacecraft will be gently pushed towards a heliocentric orbit.

Notes for Editors:

LISA Pathfinder is an ESA mission with important contributions from its member states and NASA.

The LISA Technology Package payload has been delivered by several national funding agencies and ESA, in particular: Italy (ASI); Germany (DLR); the United Kingdom (UKSA); France (CNES); Spain (CDTI); Switzerland (SSO); and the Netherlands (SRON). LISA Pathfinder also carries the Disturbance Reduction System payload, provided by NASA.

Related Publication:

Armano, M., et al.: http://sci.esa.int/lisa-pathfinder/57912-armano-et-al/

Related article:

Next step towards a gravitational-wave observatory in space
http://orbiterchspacenews.blogspot.ch/2016/10/next-step-towards-gravitational-wave.html

Related links:

ESA - LISA Pathfinder: http://sci.esa.int/lisa-pathfinder/

What is gravity?: http://www.esa.int/Our_Activities/Space_Science/What_is_gravity

Images (mentioned), Text, Credits: ESA/Paul McNamara/Oliver Jennrich.

Best regards, Orbiter.ch

The Coolest Landscape on Mars (or Earth)

NASA - Mars Reconnaissance Orbiter (MRO) patch.

Dec. 12, 2016

Many Martian landscapes contain features that are familiar to ones we find on Earth, like river valleys, cliffs, glaciers and volcanos.

However, Mars has an exotic side too, with landscapes that are alien to Earthlings. This image shows one of these exotic locales at the South Pole. The polar cap is made from carbon dioxide (dry ice), which does not occur naturally on the Earth. The circular pits are holes in this dry ice layer that expand by a few meters each Martian year.

New dry ice is constantly being added to this landscape by freezing directly out of the carbon dioxide atmosphere or falling as snow. Freezing out the atmosphere like this limits how cold the surface can get to the frost point at -130 degrees Celsius (-200 F). Nowhere on Mars can ever get any colder this, making this this coolest landscape on Earth and Mars combined.

This is a stereo pair with ESP_047237_0930: http://www.uahirise.org/ESP_047237_0930

The University of Arizona, Tucson, operates HiRISE, which was built by Ball Aerospace & Technologies Corp., Boulder, Colo. NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, manages the Mars Reconnaissance Orbiter Project for NASA's Science Mission Directorate, Washington.

More information: http://www.jpl.nasa.gov/spaceimages/details.php?id=PIA21216

Mars Reconnaissance Orbiter (MRO): http://www.nasa.gov/mission_pages/MRO/main/index.html

Image, Text, Credits: NASA/Tony Greicius/JPL-Caltech/Univ. of Arizona.

Greetings, Orbiter.ch

NASA Mission to Search for Rare Asteroids

NASA - OSIRIS-REx Mission patch.

Dec. 12, 2016

NASA’s first mission to return a sample of an asteroid to Earth will be multitasking during its two-year outbound cruise to the asteroid Bennu. On Feb. 9-20, the OSIRIS-REx (Origins, Spectral Interpretation, Resource Identification, and Security– Regolith Explorer) spacecraft will activate its onboard camera suite and commence a search for elusive “Trojan” asteroids.

Trojans are asteroids that are constant companions to planets in our solar system as they orbit the sun, remaining near a stable point 60 degrees in front of or behind the planet. Because they constantly lead or follow in the same orbit, they will never collide with their companion planet.

Image above: In February 2017, the OSIRIS-REx spacecraft will undertake a search for Earth-Trojan asteroids while on its outbound journey to the asteroid Bennu. Earth Trojans are asteroids that share an orbit with Earth while remaining near a stable point 60 degrees in front of or behind the planet. Image Credits: University of Arizona/Heather Roper.

There are six planets in our solar system with known Trojan asteroids—Jupiter, Neptune, Mars, Venus, Uranus and, yes, even Earth. The Earth Trojan is elusive; to date, scientists have only discovered one Earth trojan asteroid -- 2010 TK7  -- found by NASA’s NEOWISE project in 2010. Yet there are more than 6,000 known Trojans that are co-orbiting the sun with the gas giant Jupiter.

Scientists predict that there should be more Trojans sharing Earth’s orbit, but these asteroids are difficult to detect from Earth because they appear close to the sun from Earth's point of view. In mid-February 2017, however, the OSIRIS-REx spacecraft will be positioned in an ideal spot to undertake a survey.

Over 12 days, the OSIRIS-REx Earth-Trojan asteroid search will employ the spacecraft’s MapCam imager to methodically scan the space where Earth Trojans are expected to exist.  Many of these observations will closely resemble MapCam’s planned activities during its upcoming search for satellites of asteroid Bennu, so the Trojan asteroid search serves as an early rehearsal for the mission's primary science operations.

Image above: In February 2017, the OSIRIS-REx spacecraft will undertake a search for Earth-Trojan asteroids while on its outbound journey to the asteroid Bennu. Earth Trojans are asteroids that share an orbit with Earth while remaining near a stable point 60 degrees in front of or behind the planet (horizontal view). Image Credits: University of Arizona/Heather Roper.

“The Earth-Trojan asteroid search provides a substantial advantage to the OSIRIS-REx mission,” said OSIRIS-REx Principal Investigator Dante Lauretta of the University of Arizona, Tucson. “Not only do we have the opportunity to discover new members of an asteroid class, but more importantly, we are practicing critical mission operations in advance of our arrival at Bennu, which ultimately reduces mission risk.”

The OSIRIS-REx spacecraft is currently on a seven-year journey to rendezvous with, study, and bring a sample of Bennu to Earth. This sample of a primitive asteroid will help scientists understand the formation of our solar system more than 4.5 billion years ago.

Artist's view of OSIRIS-REx spacecraft over Bennu. Image Credit: NASA

NASA’s Goddard Space Flight Center provides overall mission management, systems engineering and the safety and mission assurance for OSIRIS-REx. Dante Lauretta of the University of Arizona, Tucson, is the principal investigator, and the University of Arizona also leads the science team and the mission’s science observation planning and data processing. Lockheed Martin Space Systems in Denver built the spacecraft and is providing flight operations. Goddard and KinetX Aerospace are responsible for navigating the OSIRIS-REx spacecraft. OSIRIS-REx is the third mission in NASA’s New Frontiers Program. NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the agency’s New Frontiers Program for its Science Mission Directorate in Washington.

OSIRIS-REx (Origins Spectral Interpretation Resource Identification Security Regolith Explorer): http://www.nasa.gov/mission_pages/osiris-rex/index.html

Images (mentioned), Text, Credits: NASA's Goddard Space Flight Center/Nancy Neal Jones/Karl Hille.

Greetings, Orbiter.ch

Space Station Experiment Marks Five Years Probing Cosmic Ray Mysteries

NASA - AMS-02 Mission patch.

Dec. 12, 2016

Image above: The Alpha Magnetic Spectrometer (AMS). Image Credit: NASA.

We have a lot left to learn from cosmic rays, and what we have learned is often surprising. That’s the persistent message as NASA and the U.S. Department of Energy mark five years of studying cosmic ray particles with the Alpha Magnetic Spectrometer experiment, or AMS-02, attached to the International Space Station.

On May 19, 2011, astronauts used a remote-controlled robotic arm to attach the nearly 17,000-pound payload, an international experiment sponsored by DOE and NASA.

AMS was designed to detect cosmic rays, highly energetic particles and nuclei that bombard the Earth from space. Since its installation, AMS has collected data from more than 90 billion cosmic ray events, experiment lead Sam Ting reported Dec. 8 in a colloquium at the experiment’s headquarters, CERN European research center.

Ting, a Nobel laureate and Thomas Dudley Cabot Professor of Physics at the Massachusetts Institute of Technology, shared a mix of new and recent results during his talk.

For one, cosmic rays could tell us about the imbalance between matter and antimatter in the universe.

Because matter and antimatter particles are created in pairs, scientists think the Big Bang should have produced half of each. But those evenly matched partners would have annihilated one another, and we would not exist.

The generally accepted theory is that this imbalance came about thanks to processes in the very young universe that favor matter over antimatter. But an alternative idea is that a large amount of antimatter is still out there; it just hasn’t had a chance to collide with our matter-filled universe.

One clue that this is the case would be finding heavier antimatter nuclei in the wild.

With the negligible amount of antimatter that exists in our universe, “it’s almost impossible to make anything bigger than a proton,” says AMS Deputy Principal Investigator Mike Capell of MIT. “Getting the antimatter together to collide into an antihelium or anticarbon nucleus is not very probable.”

AMS scientists do not claim to have detected antihelium, but they did announce that they have not ruled out “a few” candidate events.

“Given the success of the standard cosmological model and the absence of gamma rays from hypothetical matter-antimatter interfaces, I think it’s very implausible that there’d be whole galaxies made of antimatter,” says theoretical astrophysicist Roger Blandford of the Kavli Institute for Particle Astrophysics and Cosmology, a joint institute of Stanford University and SLAC National Accelerator Laboratory. “But it’s the sort of investigation that could still give us a surprising discovery.”

Cosmic rays could also tell us something about dark matter, which has never been detected directly.

Cosmic rays can consist of a variety of particles, such as electrons or their antimatter counterparts, positrons. In previous measurements, AMS detected a surprising number of positrons on the higher end of its energy range. It is possible that collisions between dark matter particles created this excess of antimatter particles.

An updated analysis—this one using almost double the number of electrons and positrons—continues to show this excess. But dark matter isn’t the only possible cause, Blandford says.

“One interpretation is that one is seeing the annihilation of dark matter particles,” he says. “But there might be equally reasonable explanations associated with traditional astrophysics that could make the same sort of signal.”

Pulsars are a particularly difficult alternative source to rule out. But AMS scientists anticipate that they will collect enough data to better discriminate between models by 2024, Ting said in his presentation.

Cosmic rays could tell us about their history.

Image above: The Alpha Magnetic Spectrometer (AMS) is a particle-physics detector that looks for dark matter, antimatter and missing matter from a module attached to the outside of the International Space Station (ISS). Image Credits: NASA/CERN.

As particles in cosmic rays approach light speed, time effectively slows down for them, as Albert Einstein predicted in his theory of relativity. We can see evidence of time dilation in the extended lifetimes of particles traveling near light speed.

In a forthcoming AMS result, scientists look at just how much the lifetimes of isotopes of beryllium stretch as they travel in cosmic rays. Based on that measurement, they estimate the cosmic rays we see in our galaxy are about 12 million years old.

Cosmic rays could tell us about what they go through on their trip to Earth.

Both observation and theory have a ways to go in this area, Blandford says. “They are both works in progress and, despite great advances, we still do not understand how cosmic rays propagate from their sources – mainly supernova remnants – to Earth.”

When cosmic rays get into collisions, they can produce secondary cosmic rays, which are made up of different ingredients. In a recently published result studying the ratio of boron (found only in secondary cosmic rays) to carbon (found in primary cosmic rays) at different energies, AMS scientists found possible evidence of turbulence in the cosmic rays’ path to our planet—but nothing that would explain the positron excess.

Finally, cosmic rays could tell us that we don’t know what we think we know.

In an unpublished analysis, AMS scientists found that their measurements of the spectra and ratios of different nuclei—protons, lithium and helium—did not fit well with predictions. This could mean that scientists’ assumptions about cosmic rays need to be reexamined.

AMS scientists want to help with that. They plan to collect data from hundreds of billions of primary cosmic rays through 2024 as their experiment continues its orbit about 240 miles above the Earth.

Another space station experiment focused on cosmic ray particles and what they could reveal about dark matter is the CALorimetric Electron Telescope (CALET) investigation. The instrument launched aboard the Japan Aerospace Exploration Agency (JAXA) H-II Transfer Vehicle “Kounotori” in August 2015 and was placed on the International Space Station’s Japanese Experiment Module - Exposed Facility just days after its arrival.

>The Cosmic Ray Energetics and Mass investigation known as CREAM, is targeted for launch to the space station in mid-2017 on a SpaceX cargo resupply mission. CREAM's instruments measure the charges of cosmic rays ranging from hydrogen up through iron nuclei, over a broad energy range.

Both CALET and CREAM complement the AMS cosmic ray particle science.

PSO is updating the toolbox to make the investigation available public.

Related links:

International Space Station (ISS): https://www.nasa.gov/mission_pages/station/main/index.html

Space Station Research and Technology: https://www.nasa.gov/mission_pages/station/research/index.html

AMS - CERN: https://home.cern/about/experiments/ams

AMS Collaboration - CERN: http://ams.cern.ch/

For more information about European Organization for Nuclear Research (CERN), Visit: http://home.cern/

Images (mentioned), Text, Credits: NASA/Kathryn Jepsen/Mark Garcia.

Best regards, Orbiter.ch

Spinning black hole swallowing star explains superluminous event

ESA - Hubble Space Telescope logo.

12 December 2016

Close-up of star near a supermassive black hole (artist’s impression)

An extraordinarily brilliant point of light seen in a distant galaxy, and dubbed ASASSN-15lh, was thought to be the brightest supernova ever seen. But new observations from several observatories, including the NASA/ESA Hubble Space Telescope, have now cast doubt on this classification. Instead, a group of astronomers propose that the source was an even more extreme and rare event — a rapidly spinning black hole ripping apart a passing star that came too close.

In 2015, the All Sky Automated Survey for SuperNovae (ASAS-SN) detected an event, named ASASSN-15lh, that was recorded as the brightest supernova ever — and categorised as a superluminous supernova, the explosion of an extremely massive star at the end of its life. It was twice as bright as the previous record holder, and at its peak was 20 times brighter than the total light output of the entire Milky Way.

An international team, led by Giorgos Leloudas at the Weizmann Institute of Science, Israel, and the Dark Cosmology Centre, Denmark, has now made additional observations of the distant galaxy, about 4 billion light-years from Earth, where the explosion took place and they have proposed a new explanation for this extraordinary event.

Supermassive black hole with torn-apart star (artist’s impression)

“We observed the source for 10 months following the event and have concluded that the explanation is unlikely to lie with an extraordinary bright supernova. Our results indicate that the event was probably caused by a rapidly spinning supermassive black hole as it destroyed a low-mass star,” explains Leloudas.

In this scenario, the extreme gravitational forces of a supermassive black hole, located in the centre of the host galaxy, ripped apart a Sun-like star that wandered too close — a so-called tidal disruption event, something so far only observed about 10 times. In the process, the star was “spaghettified” and shocks in the colliding debris as well as heat generated in accretion led to a burst of light. This gave the event the appearance of a very bright supernova explosion, even though the star would not have become a supernova on its own as it did not have enough mass.

The team based their new conclusions on observations from a selection of telescopes, both on the ground and in space. Among them was the NASA/ESA Hubble Space Telescope, the Very Large Telescope at ESO’s Paranal Observatory and the New Technology Telescope at ESO’s La Silla Observatory [1].

Spinning supermassive black hole rips star apart (artist’s impression)

“There are several independent aspects to the observations that suggest that this event was indeed a tidal disruption and not a superluminous supernova,” explains coauthor Morgan Fraser from the University of Cambridge, UK (now at University College Dublin, Ireland).

In particular, the data revealed that the event went through three distinct phases over the 10 months of follow-up observations. These data overall more closely resemble what is expected for a tidal disruption than a superluminous supernova. An observed re-brightening in ultraviolet light as well as a temperature increase further reduce the likelihood of a supernova event. Furthermore, the location of the event — a red, massive and passive galaxy — is not the usual home for a superluminous supernova explosion, which normally occur in blue, star-forming dwarf galaxies.

Although the team say a supernova source is therefore very unlikely, they accept that a classical tidal disruption event would not be an adequate explanation for the event either. Team member Nicholas Stone from Columbia University, USA, elaborates: “The tidal disruption event we propose cannot be explained with a non-spinning supermassive black hole. We argue that ASASSN-15lh was a tidal disruption event arising from a very particular kind of black hole.”

Supermassive black hole rips star apart (simulation)

The mass of the host galaxy implies that the supermassive black hole at its centre has a mass of at least 100 million times that of the Sun. A black hole of this mass would normally be unable to disrupt stars outside of its event horizon — the boundary within which nothing is able to escape its gravitational pull. However, if the black hole is a particular kind that happens to be rapidly spinning — a so-called Kerr black hole — the situation changes and this limit no longer applies.

“Even with all the collected data we cannot say with 100% certainty that the ASASSN-15lh event was a tidal disruption event,” concludes Leloudas. “But it is by far the most likely explanation.”

Notes:

[1] As well as the data from ESO’s Very Large Telescope, the New Technology Telescope and the NASA/ESA Hubble Space Telescope the team used observations from NASA’s Swift telescope, the Las Cumbres Observatory Global Telescope (LCOGT), the Australia Telescope Compact Array, ESA’s XMM-Newton, the Wide-Field Spectrograph (WiFeS) and the Magellan Telescope.

More information:

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

This research was presented in a paper entitled “The Superluminous Transient ASASSN-15lh as a Tidal Disruption Event from a Kerr Black Hole”, by G. Leloudas et al. to appear in the new Nature Astronomy magazine.

The team is composed of G. Leloudas (Weizmann Institute of Science, Rehovot, Israel; Niels Bohr Institute, Copenhagen, Denmark), M. Fraser (University of Cambridge, Cambridge, UK), N. C. Stone (Columbia University, New York, USA), S. van Velzen (The Johns Hopkins University, Baltimore, USA), P. G. Jonker (Netherlands Institute for Space Research, Utrecht, the Netherlands; Radboud University Nijmegen, Nijmegen, the Netherlands), I. Arcavi (Las Cumbres Observatory Global Telescope Network, Goleta, USA; University of California, Santa Barbara, USA), C. Fremling (Stockholm University, Stockholm, Sweden), J. R. Maund (University of Sheffield, Sheffield, UK), S. J. Smartt (Queen’s University Belfast, Belfast, UK), T. Krühler (Max-Planck-Institut für extraterrestrische Physik, Garching b. München, Germany), J. C. A. Miller-Jones (ICRAR - Curtin University, Perth, Australia), P. M. Vreeswijk (Weizmann Institute of Science, Rehovot, Israel), A. Gal-Yam (Weizmann Institute of Science, Rehovot, Israel), P. A. Mazzali (Liverpool John Moores University, Liverpool, UK; Max-Planck-Institut für Astrophysik, Garching b. München, Germany), A. De Cia (European Southern Observatory, Garching b. München, Germany), D. A. Howell (Las Cumbres Observatory Global Telescope Network, Goleta, USA; University of California Santa Barbara, Santa Barbara, USA), C. Inserra (Queen’s University Belfast, Belfast, UK), F. Patat (European Southern Observatory, Garching b. München, Germany), A. de Ugarte Postigo (Instituto de Astrofisica de Andalucia, Granada, Spain; Niels Bohr Institute, Copenhagen, Denmark), O. Yaron (Weizmann Institute of Science, Rehovot, Israel), C. Ashall (Liverpool John Moores University, Liverpool, UK), I. Bar (Weizmann Institute of Science, Rehovot, Israel), H. Campbell (University of Cambridge, Cambridge, UK; University of Surrey, Guildford, UK), T.-W. Chen (Max-Planck-Institut für extraterrestrische Physik, Garching b. München, Germany), M. Childress (University of Southampton, Southampton, UK), N. Elias-Rosa (Osservatoria Astronomico di Padova, Padova, Italy), J. Harmanen (University of Turku, Piikkiö, Finland), G. Hosseinzadeh (Las Cumbres Observatory Global Telescope Network, Goleta, USA; University of California Santa Barbara, Santa Barbara, USA), J. Johansson (Weizmann Institute of Science, Rehovot, Israel), T. Kangas (University of Turku, Piikkiö, Finland), E. Kankare (Queen’s University Belfast, Belfast, UK), S. Kim (Pontificia Universidad Católica de Chile, Santiago, Chile), H. Kuncarayakti (Millennium Institute of Astrophysics, Santiago, Chile; Universidad de Chile, Santiago, Chile), J. Lyman (University of Warwick, Coventry, UK), M. R. Magee (Queen’s University Belfast, Belfast, UK), K. Maguire (Queen’s University Belfast, Belfast, UK), D. Malesani (University of Copenhagen, Copenhagen, Denmark; DTU Space, Denmark), S. Mattila (University of Turku, Piikkiö, Finland; Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Piikkiö, Finland; University of Cambridge, Cambridge, UK), C. V. McCully (Las Cumbres Observatory Global Telescope Network, Goleta, USA; University of California Santa Barbara, Santa Barbara, USA), M. Nicholl (Harvard-Smithsonian Center for Astrophysics, Cambridge, Massachusetts, USA), S. Prentice (Liverpool John Moores University, Liverpool, UK), C. Romero-Cañizales (Pontificia Universidad Católica de Chile, Santiago, Chile; Millennium Institute of Astrophysics, Santiago, Chile), S. Schulze (Pontificia Universidad Católica de Chile, Santiago, Chile; Millennium Institute of Astrophysics, Santiago, Chile), K. W. Smith (Queen’s University Belfast, Belfast, UK), J. Sollerman (Stockholm University, Stockholm, Sweden), M. Sullivan (University of Southampton, Southampton, UK), B. E. Tucker (Australian National University, Canberra, Australia; ARC Centre of Excellence for All-sky Astrophysics (CAASTRO), Australia), S. Valenti (University of California, Davis, USA), J. C. Wheeler (University of Texas at Austin, Austin, USA), and D. R. Young (Queen’s University Belfast, Belfast, UK).

For images and more information about Hubble Space Telescope, visit:

http://hubblesite.org/
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http://www.spacetelescope.org/

Related Links:

Research paper: http://www.spacetelescope.org/static/archives/releases/science_papers/heic1622/heic1622a.pdf

ESO press release: http://www.eso.org/public/news/eso1644/

LGTO press release: https://lco.global/news/star-ripped-apart-black-hole/

SRON press release: https://sron.nl/news/4662-grootste-hypernova-ooit-blijkt-roterend-zwart-gat-dat-ster-uiteenscheurt

NASA’s Swift telescope: http://swift.gsfc.nasa.gov/

Las Cumbres Observatory Global Telescope (LCOGT): https://lco.global/observatory/

Australia Telescope Compact Array: https://www.narrabri.atnf.csiro.au/

ESA’s XMM-Newton: http://www.cosmos.esa.int/web/xmm-newton

Wide-Field Spectrograph (WiFeS): http://rsaa.anu.edu.au/observatories/instruments/wide-field-spectrograph-wifes

Magellan Telescope: http://obs.carnegiescience.edu/magellan

Very Large Telescope (VLT): http://www.eso.org/public/usa/teles-instr/paranal/

New Technology Telescope: http://www.eso.org/public/usa/teles-instr/lasilla/ntt/

Weizmann Institute of Science: http://www.weizmann.ac.il/pages/

Dark Cosmology Centre: http://dark.nbi.ku.dk/

All Sky Automated Survey for SuperNovae (ASAS-SN): http://www.astronomy.ohio-state.edu/~assassin/index.shtml

Images, Videos, Text, Credits: ESA/Hubble/ESO/M. Kornmesser/N. Stone/K. Hayasaki.

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