Tuesday, October 17, 2017

Earth Quasi Satellite (469219) 2016 HO3 an asteroid, not Space Junk

At the 49th Annual Division for Planetary Sciences Meeting in Provo, Utah, astronomers led by Vishnu Reddy at the University of Arizona confirm true nature of one of Earth's companions on its journey around the sun.  

Was it a burned-out rocket booster, tumbling along a peculiar near-earth orbit around the sun, and only occasionally getting close enough to be studied with even the largest telescopes?

Not at all, as it turns out. While, based on previous observations, most astronomers had strongly suspected that object (469219) 2016 HO3 was an ordinary asteroid and not space junk, it took a team of astronomers led by Vishnu Reddy, assistant professor at the Lunar and Planetary Laboratory, University of Arizona, working with one of the world’s largest telescopes, the Large Binocular Telescope (LBT), on Mt. Graham in Southeastern Arizona, to learn the true nature of this near-Earth object.

2016 HO3 is a small near-Earth object (NEO) measuring no more than 100 meters (330 feet) across that, while orbiting the Sun, also appears to circle around the Earth as a "quasi-satellite." Only five quasi-satellites have been discovered so far, but 2016 HO3 is the most stable of them. The provenance of this object is unknown. On timescales of a few centuries, 2016 HO3 remains within 38-100 lunar distances from us.

2016 HO3 is seen at the top left corner of this animation made of ten 2mn long exposures in I band using MODS1 on the left side of LBT - The telescope is tracking the moving asteroid, so background stars (and even a couple of galaxies) are trailed.  Credit LBTO

“While HO3 is close to the Earth, its small size – possibly not larger than 100 feet – makes it challenging target to study, said Reddy. “Our observations show that the HO3 rotates once every 28 minutes and is made of materials similar to asteroids." 

Soon after its discovery in 2016, astronomers were not sure where this object came from, but in a recent presentation at the annual Division for Planetary Sciences Conference of the American Astronomical Society in Provo, Utah, Reddy and his colleagues show that Earth’s new traveling buddy is an asteroid and not space junk. The new observations confirm that 2016 HO3 is a natural object of similar provenance to other small NEOs that zip by the Earth each month. 

"In an effort to constrain its rotation period and surface composition, we observed 2016 HO3 on April 14 and 18 with the Large Binocular Telescope and the Discovery Channel Telescope," Reddy said. "The derived rotation period and the spectrum of emitted light are not uncommon amongst small NEOs, suggesting that 2016 HO3 is a natural object of similar provenance to other small NEOs."

Light curve of 2016 HO3 showing the 28m rotation period of the asteroid
(MODS on LBT on Apr 14, and LMI on DCT on Apr 18)

In their presentation, "Ground-based Characterization of Earth Quasi Satellite (469219) 2016 HO3," Reddy and his co-authors, Olga Kuhn, Audrey Thirouin, Al Conrad, Renu Malhotra, Juan Sanchez, and Christian Veillet, point out that the light reflected off the surface of 2016 HO3 is similar to meteorites we have on Earth. 

One way to visualize HO3's orbit is by picturing a hula hoop dancer – the sun in this analogy – twirling two hoops around the hips at the same time, ever so slightly out of sync. While it orbits the sun, the object makes yearly loops (link to https://www.youtube.com/watch?v=zMJc7gmychk ) around the Earth. As a result, the object appears to orbit the Earth, but it is not gravitationally bound to our planet.

"Of the near-Earth objects we know of, these types of objects would be the easiest to reach, so they could potentially make suitable targets for exploration," said Veillet, director of the LBT Observatory. "With its binocular arrangement of two 8.4-meter mirrors, coupled with a very efficient pair of imagers and spectrographs like MODS, LBT is ideally suited to the characterization of these Earth's companions." 

NASA Near-Earth Object Observations Program Grant NNX17AJ19G (PI: Reddy) funded parts of this work. 

# # #
PIO Contact: Daniel W. Stolte +1 520-621-4402 stolte@email.arizona.edu
Science Contact at LPL: Vishnu Reddy reddy@lpl.arizona.edu
Science contact at LBTO: Christian Veillet cveillet@lbto.org

"Ground-based Characterization of Earth Quasi Satellite (469219) 2016 HO3," Vishnu Reddy, Olga Kuhn, Audrey Thirouin, Al Conrad, Renu Malhotra, Juan A. Sanchez, Christian Veillet. 49th Annual Division for Planetary Sciences Meeting - Tuesday, October 17th, 2017. 204.07.

Thursday, October 12, 2017

The LBT gets polarized: First light for the PEPSI polarimeters

Thanks to a cleverly designed "two-in-one" instrument attached to the world's most powerful telescope, astronomers can extract more clues about the properties of distant stars or exoplanets than previously possible. 

Developed at the Leibniz-Institute for Astrophysics in Potsdam, Germany, the Potsdam Echelle Polarimetric and Spectroscopic Instrument (PEPSI) saw first light on April 1, 2015, after being successfully installed at the Large Binocular Telescope Observatory (LBTO) in Arizona, USA. 

Once both of PEPSI's polarimeters were mounted in the focus points of each of the LBT's two 8.4-meter mirrors  in early September 2017, the telescope was pointed to the star gamma Equ and polarized light was received. From these spectra astronomers can, for example, deduce the geometry and strength of magnetic fields on the surfaces of distant stars, or study the reflected light from the atmospheres of potentially habitable exoplanets.

The DX (right side) polarimeter on LBT
A polarimeter separates starlight according to its oscillation planes. It is complementary to a spectrograph that, like a prism, separates light according to its oscillation frequencies (or color). The two combined, polarimeter and spectrograph, added to a powerful telescope, enable astronomers to obtain spectra in polarized light. This in turn allows the characterization of the full wave-front of the incoming stellar light and extract details of its radiation physics that otherwise remain hidden. 

A series of integrations in circularly and linearly polarized light was obtained when the telescope was pointed to the magnetic reference star Gamma Equulei, or gamma Equ, a double star located about 118 light-years from Earth. These spectra have a spectral resolution of R=120,000, that means they can resolve two wavelengths only five hundredths of a hydrogen atom’s diameter apart. They cover two large wavelength regions in the visible light simultaneously, and have an unprecedented signal-to-noise ratio. Because the two polarimeters for each of LBT's "eyes" are identical and modular in design, circular and linear polarizations were obtained simultaneously. 

 First polarimetric spectrum from PEPSI. The target is the bright magnetic A9VpSrCrEu star gamma Equ. The black line is the PEPSI spectrum and the red line is, for comparison, the HARPS-Pol  spectrum. From top to bottom: the magnetic null spectrum enlarged by a factor five, the normalized linear Stokes component U/Ic enlarged by a factor 5, the normalized linear Stokes component Q/Ic  enlarged by a factor 5, the normalized circular Stokes component V/Ic, and the normalized integral light I/Ic. Because the two polarimeters for each of LBT's "eyes" are identical and modular in design, circular and linear polarizations were obtained simultaneously. 

The gamma Equ test also included a so-called null spectrum, which is obtained by swapping the observation sequence in the two fibers. Ideally, it would give zero polarization and be independent of wavelength. Any residual polarization would be due to instrumental effects.  

“The null spectrum for PEPSI shows an extraordinary low degree of polarization noise caused by the instrument,"  says its principal investigator, Prof. Dr. Klaus Strassmeier, Research Branch Director at AIP  and a professor of astronomy at the University of Potsdam. "Compared with the best spectropolarimeters currently available at other telescopes, it's probably better by a factor of ten." 

“Eventually, the PEPSI polarimeters will enable stellar magnetic field measurements with extremely high precision," adds PEPSI’s project scientist Dr. Ilya Ilyin. 

The SX (left side) polarimeter on LBT
For Dr. Christian Veillet, LBTO Director, “In the 8-10m class telescope select club, PEPSI was already a unique instrument, thanks to its resolution coupled to two 8.4-m mirrors simultaneously available. The addition of a polarimeter on each of LBT’s eyes gives LBTO yet another unique capability. It comes as a precious complement to interferometry, which gives LBT's two eyes the imaging resolution of a 23-m telescope."

The PEPSI instrument is available to all LBT partners.

The press release at AIP is here.

More information about PEPSI here.

Science contacts:
Prof. Dr. Klaus G. Strassmeier (Principal Investigator), +49 331-7499 223, kstrassmeier@aip.de
Dr. Ilya Ilyin (project scientist), +49 331-7499 269, ilyin@aip.de

Media contacts:
Katrin Albaum (AIP), +49 331-7499 803, presse@aip.de
Christian Veillet (Large Binocular Telescope Observatory),+1 520-349-4576, cveillet@lbto.org

The key areas of research at the Leibniz Institute for Astrophysics Potsdam (AIP) are cosmic magnetic fields and extragalactic astrophysics. A considerable part of the institute's efforts aim at the development of research technology in the fields of spectroscopy, robotic telescopes, and e-science. The AIP is the successor of the Berlin Observatory founded in 1700 and of the Astrophysical Observatory of Potsdam founded in 1874. The latter was the world's first observatory to emphasize explicitly the research area of astrophysics. The AIP has been a member of the Leibniz Association since 1992.

The LBT is an international collaboration among institutions in the United States, Italy and Germany. LBT Corporation partners are: The University of Arizona on behalf of the Arizona Board of Regents; Istituto Nazionale di Astrofisica, Italy; LBT Beteiligungsgesellschaft, Germany, representing the Max-Planck Society, The Leibniz Institute for Astrophysics Potsdam, and Heidelberg University; The Ohio State University, and The Research Corporation, on behalf of The University of Notre Dame, University of Minnesota and University of Virginia.

Friday, September 8, 2017

LBT snags first glimpse of OSIRIS-REx since launch

OSIRIS-REx is  a NASA spacecraft traveling to a near-Earth asteroid called Bennu to bring a small sample back to Earth for study. The mission launched Sept. 8, 2016, from Cape Canaveral Air Force Station. As planned, the spacecraft will reach Bennu in 2018 and return a sample to Earth in 2023.

The spacecraft is currently approaching Earth for its gravity assist maneuver, which will change its trajectory and set it on course to rendez-vous Bennu. Its closest approach to Earth is scheduled for 12:52 p.m. EDT on Friday, Sept. 22.

The Large Binocular Telescope Observatory (LBTO) used the LBCs (Large Binocular Cameras), a pair of wide-field cameras at the prime focus of each of its two 8.4m mirrors, to image the field around the predicted position of the spacecraft on the night of September 1.

The animation above (three images - LBCB - 300s exp. time - V filter) centered on OSIRIS-REx (red square).  2017 September 2 at around 11:00 UTC. The spacecraft was 11-million kilometers away from Earth at the time of the observation. The spacecraft was  28% illuminated with a magnitude V~25.

On that night, LBTO was back on sky after a long period of shutdown which started on June 15 due to the Frye fire, followed by its seasonal monsoon shutdown (Jul 10 - Aug 31). OSIRIS-REx was an excellent target of opportunity at the beginning of a 12-night period dedicated to a full restart of the facility. A good way to come back to observing after 2.5 months of closed dome!

Thanks go to V. Reddy and A. Conrad for proposing the target, B. Rothberg, O. Kuhn, J. Hill and S. Allanson for observing, C. Veillet and C. Hergenrother for the data reduction, and the whole LBTO staff for a great shutdown work!

Monday, July 10, 2017

From the Frye Fire to monsoon shutdown

Monday July 10

The night of July 9 was the last observing night scheduled in the 17A semester. On the morning of Monday July 10, the observatory entered officially its 2017 summer shutdown. On this last night, rain came over Mt Graham, a blessing as it is bringing the Frye Fire closer to extinction.

With more rain expected in the coming days/weeks comes the danger of flood, erosion and silting damage, as well as rock and mud slides, trees blowing down, stumps breaking loose and rolling down hillsides, etc. Sludge was already on the road this morning, as seen in the picture below.

Sludge from the severe burns above 
the road around mile 133 on Swift Trail (LBTO/P. Hartley)

Rain on the SW side of  Mt Graham
(LBTO - roofcam)

While closed to observing, LBTO managed to have much work done in two areas: tuning of the AO system, mostly on the DX side, and servicing mission of LUCI1 (W. Seifert, Landsternwarte, Heidelberg). LUCI1 went back to the telescope warm today, on schedule, after passing all its tests!

In addition, the overall maintenance of the observatory was performed by LBTO staff in spite of access issues and skeleton crews at times. An inflatable bladder was installed to secure the gap between the shutter doors and the central plenum of the enclosure to prevent leaks in case of a weather event bringing hail followed by heavy rains.

The inflatable bladder installed on the roof (red tube) between the shutter doors and the central plenum (LBTO/J. Riedl)

Animation of the Frye Fire evolution from June 13 to July 9
(NIROPS - Google Earth - LBTO)

The Frye Fire

The Frye Fire started on June 7 in the Frye Canyon 4km NNE of the observatory. It started impacting observations on the night of June 14, where we had to close at 1am for smoke and ash. The following night was lost to more smoke and the fire coming closer to the site. LBTO did not open since then, ending with 25 nights in a row lost to the fire.

June 16
Only essential staff allowed to stay on the mountain. Three stay at LBTO (mountain manager, telescope operator and instrument specialist) and two for MGIO. Back burns are lit close to the observatory (north side).

Back burns north of the observatory (LBTO/S. Allanson)

June 17:
Telescope operator and instrument specialist leave the observatory. The fire comes closer...


June 18:

A fire storm gets close to LBTO and within feet of the VATT. A walk around all of the buildings shows that they have taken some heat, but none appear to have been damaged. Power remains on...

Toward VATT...
(LBTO/K. Newton)
Through the kitchen window
(LBTO/K. Newton)
A DC10 dumping retardant
(LBTO/K. Newton) 

June 19

We are able to relieve the mountain manager (Kevin down, Pat up).

A pink SMT and a still standing VATT on the morning after the fire storm (LBTO/P. Hartley)

Still burning not too far from the site (LBTO/roofcam)

June 20

Now, we have a skeleton crew of 2 people...


June 21

Down to a crew of 1.

10mn of rain give a short-lived hope that real rain will come... (LBTO/J. Riedl)

June 22

MGIO water truck deliveries have been shut down after one delivery. Site running on generator.

Still burning west of MGIO, though the observatories are safe (LBTO/roofcam)

June 23

No traffic authorized...

Wind revives close-by smoldering areas and ashes are flying. No harm done as winds calm down as the night progresses. (LBTO/roofcam)

June 26

On swift trail... (LBTO/J. Riedl)
Winds are in the right direction, blowing the smoke away.
We can open the vent door to cool down the chamber! (LBTO)

June 27

A short visit by VATT staff of their telescope shows no damage on the telescope. A big relief!

VATT is unscathed! (VATT)

June 30

Crew shift change and a crew of 4 at LBTO. Still waiting for a fuel delivery as the site continues to run on generator.

Morning smoke on a nice clear sky... (LBTO)

July 1

Swift Trail is cut by the fire in a few places. We move to low power consumption mode, but still keeping LUCI2 cold for the coming commissioning run. Unexpectedly, an escorted convoy with the fuel truck and a crew swap is organized at night, departing base camp at around 8pm! We end up with a fresh crew of 2 (mountain manager and telescope operator).

On the way up (unpaved section of
Swift Trail) (LBTO/M Wagner)

Meanwhile, view from the LBTO roof... (LBTO/roofcam)

July 2

 No traffic (!)

The following morning (LBTO/M. Wagner)

July 3

Early departure from base camp (5:30am) with W. Seifert and LBTO staff. LUCI1 servicing mission will be able to start with only a one-day delay.
On the way up (LBTO/J. Riedl)

July 4:

Seven people are at LBTO!

Clouds and smoke... Still hoping for rain to be able to open before the end of the semester (5 nights left)

July 5

More staff swap happening, including iLocater visitors to run measurements and tests in closed dome. Twelve people and much is accomplished, though no on-sky work.

Still burning SW of the observatory... (LBTO)

July 08

Smoke is still present and clouds are rolling in. We will be closed tonight.  With more clouds and thunderstorms to come, the chance to open before the beginning of the shutdown is very slim! (LBTO)

July 10

First day of shutdown... Crew swap with the iLocater team leaving (happy with what they achieved) and the LUCI Aux Cryostat team coming up.

Tuesday, July 4, 2017

Missed the 2017 Users' Meeting?

More than seventy scientists gathered in Florence for the second LBTO Users' Meeting, held at the Convitto della Calza June 20-23, 2017. All LBTO partners were represented, from Arizona to the local Osservatorio Astrofisico di Arcetri

With the LBT facility instruments commissioned in pairs, LBTI routinely used by all partners in incoherent or coherent mode, LINC-NIRVANA en route for Lean-MCAO observing, and the ultra-high resolution of the PEPSI spectrograph available, the meeting focused on enabling LBT to realize its full potential in the best possible way as both a pair of 8.4m telescope and, thanks to its interferometric capabilities, a forerunner of the ELTs. 

The final program (44 oral presentations and 20 posters) boasted a healthy dose of scientific presentations, from our Solar System to the high-redshift universe, with a good complement of user-oriented talks on instruments (in operation or in development), observatory environment, data processing pipelines and observing tools. The program also featured a workshop on recently developed observation preparation tools.

For the attendees, the meeting was an opportunity to share their scientific results, projects, and aspirations for the future of the observatory, to discuss new observing modes and new services with the observatory staff, and to prepare the use of the new instruments to come at the 2018-2019 horizon, which will all use the unique performance of LBT’s upgraded AO.

Most of the presentations (slides) and posters are available online on the meeting web site  lbto2017um.weebly.com, where you will also find a photo gallery.

Credit: LBTO/B. Rothberg

Tuesday, June 27, 2017

Observatory status in the aftermath of the Frye Fire

Shortly after sunrise - 2017 06 29 - 05:18 MST
Heliograph Peak barely emerging above the smoke  (Credit: LBTO)
2017 June 29 - 17:30 MST

Last night was a mix of AO work and LUCI-AO testing in closed dome. Actually, LBTO has no dome, strictly speaking. It should be referred to as "the enclosure", which is, I guess, better than "the box" (though it really looks like a box!)  

Today was very similar to yesterday: Nice weather, no fire close-by, but smoke from the south further away for most of the day.

Here is our daily excerpt from Eric Buckley's report:

Today remains a no travel day.  There is no plan for aerial firing, hand firing and mop up with snags along the road or threatening any of the structures continue.  Anticipated humidity levels down lower 10-15%, higher 20-25%.  Levels have been increased around Turkey Flat with the anticipated burn.  Yesterday the heavy air tankers dropped 180,000 gallons.  Winds are expected to ground the aircraft again this afternoon.  There are still several places with active fire from going west and south.  Contingency plans are being made ahead of the fires movement.  Dozer lines are being made.  So far, the use of our power line corridor as a dozer line is still shown as a proposal.  Use of SR 266 to the south, Taylor Pass on the west.   

Until the fire crews cease setting back burns that have potential to harm the power line infrastructure, the commercial power will remain off. So, we are still running on generator and continue to maintain the facility in low power consumption mode, which excludes running the telescope. We are still waiting for a truck to bring fuel and start replenishing the generator tank. Hopefully for a better ending than "En attendant Godot". 

Tonight will be more AO and LUCI-AO work (in closed dome, I mean enclosure!)

For a change, below is a panorama from the roof toward the west, with a somewhat pink SMT and a mostly white VATT and its shiny dome. No fire, no smoke ;)

Panorama from the roof toward the west - 2017 06 29 - 06:47 MST (Credit: LBTO/P. Hartley)

2017 June 28 - 20:00 MST

Panorama from the roof toward SSE - 2017 06 28 - 11:00 MST (Credit: LBTO/P. Hartley)
Today was a smoky day at the observatory, though very quiet fire-wise at the site itself. The wind changed direction in the late morning, bringing smoke to MGIO.

IR map - 2017 06 28 ~0000 MST
You can see a  Video of the Frye Fire progress - June 12 to June 28, made at LBTO showing the IR maps made available by NIROPS (one image a day taken around midnight). Remember that the fire started on June 7, but was imaged by NIROPS starting only on the night of June 12. 

Here is an excerpt from today's report on the Frye Fire from Eric Buckley, MGIO Director:

The fire is at 39,051 acres with 825 people assigned. It is 43% contained. It has now been three weeks since lightning ignited this fire.
Today is a no-travel day as the fire fighters are actively setting back fires to suppress the advances toward the Turkey Flat cabins and to some extent Angles Orchard. 
Fire is still active in the Riggs Lake and Snow Flat areas of the mountain. 
Heliograph Peak is not under any threat at this time.
Yesterday’s weather was relatively calm but winds did kick up last night until around 2:45 am. This activity drove the fire further toward the Turkey Flat area. 
SR 366 is going to be very busy today and most likely tomorrow with fire fighters as they try to keep the fire from jumping over this road.

A crew of 4 made it to the mountain this morning, leaving base camp at 03:30  and relieving Bruce and Jay.  In addition to Pat, Rick H., and Jared , Geno (telescope operator) is also on site in case we can resume night time operation,.

We are still running on generator. The fuel truck could not make it up today (too short a time window). It is ready to go as soon as there is an opportunity with 2000 gallons of fuel. Meanwhile, if we continue in low consumption mode, we should be good up to early next week. Tonight will be closed-dome AO work (if possible without activating the telescope hydrostatic bearing, which we don't want to switch on as they are consuming too much power...) for part of the night, followed by work on active flexure compensation for LUCI-AO commissioning. 

The Forest Service held a public meeting this evening in Safford. You can find a video here:

Note that the USFS will be using MGIO as one of their contingency safe zones.

At sunset... The enclosure had to be moved to allow for the crane inspection work going on during the day.
The camera is still looking SSE. (credit: LBTO)

2017 June 27 - 17:50 MST

IR map - 2017 June 26 - 20:21MST (Credit: NIROPS)
These past two days have been quiet at the LBT site. Though the observatory did not suffer any damage from the Frye Fire, thanks to the great work of the fire crews, we are not back to operation due to not enough staffing, lack of commercial power, warm telescope and instrumentation, and a hazy and smoky environment.

Here is an excerpt from today's report on the Frye Fire from Eric Buckley, MGIO Director:

The fire is at 38,500 acres with 813 people assigned. It is 43% contained. The site remains secure at this time. Crews will continue to patrol for spot fires as they spring up all over the mountain. Normal for a fire of this size and complexity.
The fire continues to burn south and east of the telescope site. It is affecting travel on SR 366 from the forest boundary up to the Noon Creek area and again from the Snow Flat area up to Fort Grant Vista point. This burning is causing sudden roll-aways of burning material to break loose and run down the steep slopes ending up in the roadway. This is one of the reasons they want to restrict travel.
They are preparing to light back burns in the Turkey Flat area to suppress that portion of the fires advance toward the cabins. Any time the Forest Service lights back burns, they automatically restrict non-fire personnel movement for safety reasons. 
View from the roof toward SSE - 2017 June 27 - 17:22 MST (Credti: LBTO)

The observatory still runs on generator power, with enough fuel left in our tank for 4 to 5 days. We hope for a fuel delivery toward the end of the week. A water was able to come to the site to deliver 5000 gallons of water. We have a skeleton crew of 2 (Bruce and Jay). A crew change should happen tomorrow (starting from base camp at 3:30 am to be out of the mountain by 6:30 am to be out of the way of the controlled burns at Turkey Flat), bringing hopefully a somewhat larger crew (4).

The vent doors were left open in the very early morning for a few hours to cool the enclosure, which has been at more than 20C for some time as we did not open it for the past 10 nights... The DX Adaptive Secondary Mirror has been restarted and looks happy. 

The weather forecast calls for higher winds and dry conditions.

James and Mike W. left the mountain yesterday morning. Below are a few pictures taken by James on the way back to base camp. (Credit: LBTO/J. Riedl)

Around the observatory (June 26)


On Swift Trail (Route 366- June 26)

Thursday, May 25, 2017

The big star that couldn’t become a supernova

One star's "massive fail" could solve a mystery

OSU - For the first time in history, astronomers have been able to watch as a dying star was reborn as a black hole.

It went out with a whimper instead of a bang.

The star, which was 25 times as massive as our sun, should have exploded in a very bright supernova. Instead, it fizzled out—and then left behind a black hole.

“Massive fails” like this one in a nearby galaxy could explain why astronomers rarely see supernovae from the most massive stars, said Christopher Kochanek, professor of astronomy at The Ohio State University and the Ohio Eminent Scholar in Observational Cosmology.

As many as 30 percent of such stars, it seems, may quietly collapse into black holes—no supernova required.

“The typical view is that a star can form a black hole only after it goes supernova,” Kochanek explained. “If a star can fall short of a supernova and still make a black hole, that would help to explain why we don’t see supernovae from the most massive stars.”

He leads a team of astronomers who have been using the Large Binocular Telescope (LBT) to look for failed supernovae in other galaxies. They published their latest results in the Monthly Notices of the Royal Astronomical Society.

Among the galaxies they’ve been watching is NGC 6946, a spiral galaxy 22 million light-years away that is nicknamed the “Fireworks Galaxy” because supernovae frequently happen there. Starting in 2009, one particular star, named N6946-BH1, began to brighten weakly. By 2015, it appeared to have winked out of existence.

It’s too early in the project to know for sure how often stars experience massive fails, but Scott Adams, a former Ohio State student who recently earned his Ph.D. doing this work, was able to make a preliminary estimate.

“N6946-BH1 is the only likely failed supernova that we found in the first seven years of our survey. During this period, six normal supernovae have occurred within the galaxies we’ve been monitoring, suggesting that 10 to 30 percent of massive stars die as failed supernovae,” he said.

He leads a team of astronomers who have been using the Large Binocular Telescope (LBT) to look for failed supernovae in other galaxies. They published their latest results in the Monthly Notices of the Royal Astronomical Society.

Among the galaxies they’ve been watching is NGC 6946, a spiral galaxy 22 million light-years away that is nicknamed the “Fireworks Galaxy” because supernovae frequently happen there. Starting in 2009, one particular star, named N6946-BH1, began to brighten weakly. By 2015, it appeared to have winked out of existence.

The astronomers aimed the Hubble Space Telescope at the star’s location to see if it was still there but merely dimmed. They also used the Spitzer Space Telescope to search for any infrared radiation emanating from the spot. That would have been a sign that the star was still present, but perhaps just hidden behind a dust cloud.

All the tests came up negative. The star was no longer there. By a careful process of elimination, the researchers eventually concluded that the star must have become a black hole.

It’s too early in the project to know for sure how often stars experience massive fails, but Scott Adams, a former Ohio State student who recently earned his Ph.D. doing this work, was able to make a preliminary estimate.

“N6946-BH1 is the only likely failed supernova that we found in the first seven years of our survey. During this period, six normal supernovae have occurred within the galaxies we’ve been monitoring, suggesting that 10 to 30 percent of massive stars die as failed supernovae,” he said.

"This is just the fraction that would explain the very problem that motivated us to start the survey.”

This illustration shows the final stages in the life of a supermassive star that fails to explode as a supernova but instead implodes under gravity to form a black hole. From left to right: the massive star has evolved to a red supergiant, the envelope of the star is ejected and expands, producing a cold, red transient source surrounding the newly formed black hole. Some residual material may fall onto the black hole, as illustrated by the stream and the disk, potentially powering some optical and infrared emissions years after the collapse.
Credits: NASA, ESA, and P. Jeffries (STScI)
To study co-author Krzystof Stanek, the really interesting part of the discovery is the implications it holds for the origins of very massive black holes—the kind that the LIGO experiment detected via gravitational waves. (LIGO is the Laser Interferometer Gravitational-Wave Observatory.)

It doesn’t necessarily make sense, said Stanek, professor of astronomy at Ohio State, that a massive star could undergo a supernova—a process which entails blowing off much of its outer layers—and still have enough mass left over to form a massive black hole on the scale of those that LIGO detected.

“I suspect it’s much easier to make a very massive black hole if there is no supernova,” he concluded.

Adams is now an astrophysicist at Caltech. Other co-authors were Ohio State doctoral student Jill Gerke and University of Oklahoma astronomer Xinyu Dai. Their research was supported by the National Science Foundation.

More information: S. M. Adams et al. The search for failed supernovae with the Large Binocular Telescope: confirmation of a disappearing star, Monthly Notices of the Royal Astronomical Society (2017). doi.org/10.1093/mnras/stx816.  On rxiv: https://arxiv.org/abs/1609.01283

The Ohio State University release is here.  The STScI news release (with additional pictures) is here.

- Christopher Kochanek, 614-292-5954; Kochanek.1@osu.edu
- Krzysztof Stanek, 614-292-3433; Stanek.32@osu.edu
- Scott Adams, 626-395-8676; smadams@caltech.edu

Written by Pam Frost Gorder, 614-292-9475; Gorder.1@osu.edu

Sunday, May 14, 2017

The LBTO 2017 Users' Meeting preliminary program is out!


The preliminary program of the LBTO 2017 Users' Meeting is available here.

The list of the contributions (with their abstracts) sent so far can be found here.

More information on the Users' Meeting is available on its website.

Don't forget to register if you want to attend the meeting (and even more if you are presenting a talk or a poster!)