Wednesday, March 29, 2017

A Trojan in retreat

For at least a million years, an asteroid orbiting the “wrong” way around the sun has been playing a cosmic game of chicken with giant Jupiter and about 6,000 other asteroids sharing the giant planet’s space, says a report published in the latest issue of Nature.

The asteroid is the only one in the solar system known to have an opposite, or retrograde, orbit around the sun while at the same time sharing a planet's orbital space, says researcher and co-author Paul Wiegert of University of Western Ontario’s Department of Physics and Astronomy.


video

Jupiter shares its orbit with more than 6,000 Trojan asteroids (white), which travel in the same direction as the planet. But one of the planet’s companions is an outlier, traveling in the opposite direction. Planets and asteroids  have been enlarged to make them visible. 
All but fewer than 100 of the million or so known asteroids in our solar system travel around the sun in the same direction as Earth and the other planets (prograde motion). But asteroid 2015 BZ509 (“BZ” for short) circles the other way around – moving against the flow of all other asteroids in the giant planet’s orbital entourage (retrograde motion).

Put another way, it’s as if Jupiter were a monster truck on a track circling the sun, and the asteroids in Jupiter’s orbit are sub-compact cars all whizzing along in the same direction. BZ is the rogue — driving around the track in the wrong direction — and it does so every single lap, and has done so for thousands of laps for a million years or more.

So how does it avoid colliding with Jupiter? Jupiter’s gravity actually deflects the asteroid’s path at each pass so as to allow both to continue safely on their way, Wiegert says. Co-author Martin Connors of Athabasca University, adds: “Passes relatively near Jupiter take place twice on each body's orbit around the sun, but one is inside Jupiter's orbit, the other outside, so the disturbing effects of Jupiter, remarkably, cancel out.“

Little is known about the asteroid, which was discovered in January, 2015. It has a diameter of about three kilometers and may have originated from the same place as Halley's comet, which also has a retrograde orbit. The team hasn’t been able to determine yet if BZ is an icy comet or a rocky asteroid.

Images of 2015 BZ509 obtained at the Large Binocular Telescope Observatory (LBTO) that established its retrograde co-orbital nature. The LBTO has two 8.4 meter-wide main mirrors side-by-side, hence the two images taken in different color filters. The bright stars and the asteroid (circled in yellow) appear black and the sky white in this negative image. What are those weird white dots, spots and stripes? They are imaging artifacts in these raw images.
But their analysis – based on complex calculations and on observations through the Large Binocular Camera on the Large Binocular Telescope (LBT) on Mt. Graham, Arizona, during a span of 300 days — show BZ is somehow able to maintain a stable orbit even as an outlier. For co-author Christian Veillet of the LBT Observatory, this is a new step in a 15-year-long collaboration among the three co-authors, which until now, has been devoted to prograde asteroids sharing Earth’s orbit.


The calculations conducted by the team show the orbit has been stable for at least a million years and will be stable for at least a million more. Learning more about the asteroid provides another intriguing glimpse into previously unknown and unmapped features of our solar system, says Wiegert, adding that “the detective work has just begun.”

More information and video clips are available here. The Letter in Nature can be found here.



Monday, January 9, 2017

2nd LBTO Users' Meeting - June 20,23 - Florence, Italy. Save the date!

The LBTO 2017 Users' Meeting will take place at the Convitto della Calza, Florence, Italy, from Tuesday evening, June 20 to Friday, June 23.


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 2nd Users’ Meeting will focus on enabling LBT to realize its full potential as both a pair of 8.4m telescopes and, thanks to its interferometric capabilities, a forerunner of the ELTs. 

For current or prospective LBT users, the meeting will be an opportunity to share their scientific results, projects, and aspiration for the future of the observatory, foster boundary-crossing multi-partner collaborations, discuss new observing modes and new services with the observatory staff, and prepare for the next generation of instruments on the horizon for 2018-2019, all of which exploit the unique performance of the LBT's upgraded AO system.    


Please mark the date! You will find a first set of practical information (meeting place, links to hotel reservation, talk/poster submission) by visiting the Users' Meeting website here. For further questions on the meeting, contact either the Scientific Organizing Committee (soc-um @ lbto.org) or the Local Organizing Committee (loc-um @ lbto.org).


A high-resolution picture of the  poster is available here.


LUCI1-AO Shared-Risk Science Release


Diffraction limited imaging with LUCI1 is offered in a shared-risk mode. Presently, the instrument is available for reference stars in the magnitude range 3.5 to 9.8 with degraded performance, and at design performance for fainter reference stars (down to ~16).  


It is expected that full AO performance with LUCI1, and diffraction limited imaging and spectroscopy with LUCI2, will become available in the course of 2017A. 

Observers new to AO are encouraged to consult the following references:
- Natural guide star adaptive optics systems at LBT: FLAO commissioning and science operations status, Esposito, et al., SPIE (2012)
- Field Guide to Adaptive Optics, Tyson & Frazier, SPIE Press (2012)
- Adaptive Optics and its Applications, C. Max, (click here)

A Notice to Users is available here.



Monday, September 26, 2016

The first issue of the LBTO Users' Gazette is out!


The September 2016 issue of The LBTO Users' Gazette is now available. You will find it here.


This is the first issue of the Gazette, which is aimed first and foremost at informing the LBT users about the status of the observatory at a time when PIs prepare their proposals for the next semester. There are many links for web-based information or direct contacts with the LBTO staff. 

There will be at least two issues of the Gazette every year (September and March) following the observing proposal cycle. Additional issues will appear when there will be important news to share with the LBTO users. 

Thursday, September 22, 2016

LINC-NIRVANA settles in its new home at LBT


LINC-NIRVANA ready to
leave the clean room
 

LINC-NIRVANA (LN) is a near infrared imaging instrument for the Large Binocular Telescope (LBT) designed to offer both multi-conjugate adaptive optics (MCAO) and interferometric beam combination for ultra high spatial resolution. LN is a collaboration between the German and Italian partners. Its Principal Investigator is Tom Herbst (MPIA  - Max Planck Institute for Astronomy, Heidelberg).

The LN bench, without all its opto-mechanical components, was briefly introduced to its new home in November 2015 (see here). 

Following 8 months of assembly, integration, and verification in the mountain clean room, on 19-Sep-2016 the instrument was rolled out of the summit clean room in preparation for the “big lift” planned for the following day. On the morning of 20-Sep-2016 the LBT staff, working in close cooperation with the LN team, carefully flew the 10-ton instrument over the instrument gallery to its designated position at the rear bent Gregorian focal station of LBT. Then on the following day, 21-Sep-2016, the instrument cover and upper instrument access platform (UIAP) were installed. 

On-sky commissioning of the instrument should start in January 2017, following a short glimpse at the sky currently scheduled for late November 2016. 

You will find a few pictures below and videos in the LBTO video gallery.


LN has been carefully moved with the crane to the rear portion of the instrument gallery, as the telescope is gradually raised in elevation to clear the path.  All team members must work in close harmony to achieve this careful choreography.


With the telescope safely locked at the zenith position, LN is lowered the last few meters onto the instrument platform.


A last look at the interior of LINC-NIRVANA before the cover is installed.  
- The two large cylindrical structures with cable chains seen at the front of the instrument (top in this view) are the Ground Layer Wave Front Sensors, one of the first optical systems to receive light from the telescope.  
- The two rectangular black structures at the rear of the instrument (just below the center of the image) are the High Layer Wave Front Sensors. 
- The silver and yellow railing at the bottom center are the rails used to install and remove the cryostat. 
- The surrounding white cabinets contain the computers, networking gear, motor controllers, detector readout electronics, and other services required to operate LN.

Traveling back in time, here is a sketch of LN on the telescope as shown in the first SPIE paper on the instrument (2003).



Tuesday, August 9, 2016

DDO 68: Among Galaxies, a Flea, but a Voracious One

Even a dwarf galaxy with very low mass is capable of accreting smaller nearby galaxies, according to an international team of astronomers led by Francesca Annibali of INAF, the Italian National Institute for Astrophysics. This result has been achieved thanks to observations of the region surrounding the dwarf galaxy DDO 68, which has a total stellar mass of only 100 million solar masses, roughly one thousandth of our Milky Way. 




In the new study, Annibali and collaborators took advantage of  the sensitivity and the large field of view of the LBT. The team discovered that DDO 68, a dwarf galaxy located in an isolated region of space defined as a "void," is actually surrounded by a number of smaller satellite galaxies, and is accreting them. 

Follow this link to know more about this discovery!


Thursday, March 24, 2016

First AO light on LUCI1

Exciting times for LUCI1!   After receiving its first light corrected by the Ground Layer Adaptive Optics ARGOS system (see our previous post), LUCI1 was again on the spot for a few nights of commissioning in Adaptive Optics (AO) mode, this time with a full AO correction not limited to low atmospheric layers of the atmosphere.

Much work was done by the LUCI team to reach this important step. LUCI1 was retrofitted with a new detector (the same as in LUCI2) in the Fall of 2015. A new camera (N30) was also installed, designed to provide the image quality and sampling required to exploit the exquisite resolution delivered by the LBT adaptive secondary mirrors. LUCI1 looks much alike LUCI2, though its N30 camera is made of glass mirrors instead of metal mirrors for the LUCI2 N30 camera.

The LBT adaptive secondaries were unavailable for most of the last semester and came back on the telescope late in 2015 (left side - SX) and in early February (right side - DX). Thanks to the combined efforts of LBTO staff and the Arcetri AO team, the SX secondary was back in service and a first set of LUCI1 NCPA (non common path aberrations) measurements was determined just before the LUCI1-AO commissioning run. The commissioning was therefore a mix of AO checkout and LUCI1-AO observations.

Composite image of the planetary nebula NGC 6543 composed of Ks (2.75min), Brγ (16min) and H2 (8min) observations. The Ks-image has been line-subtracted with the Brγ image. Field of view is 30”x30” (0.015”/pixel). The data were taken on March 20 and 21.




The image of M5 above was taken with LUCI1 and FLAO in Ks-band on March 21 2016. Integration time is 11min. The brightest star in the field, with an R+I magnitude of 10.4, was used as reference star for the AO correction. The AO correction was obtained with 153 modes. Ambient seeing was around 0.9”. The images close to the reference star have a FWHM of around 66mas.


Interestingly enough, as seen in the above graph, the image quality is pretty constant over a ~17" radius from the AO reference star.

The next LUCI1 commissioning run is scheduled for April 2016. Stay tuned...

The following step will be to return to LUCI2, which saw first AO light in early 2015 (see here),  for commissioning of its AO spectroscopic mode.

With the addition of AO and ARGOS modes, coupled with routine binocular observations, we expect that the LUCIs will be heavily in use by early 2017, and will be a major contributor  to the scientific productivity of the Observatory.

Congratulations go to the LUCI team for an excellent work in the midst of the adaptive secondaries struggles of these past months, and to the LBTO and Arcetri AO teams for their support!