A team of astronomers has unveiled a striking new image of the Orion Molecular Cloud (OMC) – a bustling stellar nursery teeming with bright, young stars and dazzling regions of hot, glowing gas.
The researchers used the National Science Foundation’s (NSF) Green Bank Telescope (GBT) in West Virginia to study a 50 light-year long filament of star-forming gas that is wending its way through the northern portion of the OMC known as Orion A.
The GBT rendered this image by detecting the faint radio signals naturally emitted by molecules of ammonia that suffuse interstellar clouds. Scientists study these molecules to trace the motion and temperature of vast swaths of star-forming gas.
These observations are part of the first data release from a large campaign known as the Green Bank Ammonia Survey. Its purpose is to map all the star-forming ammonia and other key tracer molecules in a massive structure known as the Gould Belt.
The Gould Belt is an extended ribbon of bright, massive stars stretching about 3,000 light-years in an arc across the sky. This first release covers four distinct Gould Belt clouds, one located in Taurus, one in Perseus, one in Ophiuchus, and Orion A North in Orion.
“We hope to use these data to understand better how large clouds of gas in our galaxy collapse to form new stars,” said Rachel Friesen, one of the collaboration’s co-principal investigators and, until 31 May 2017, a Dunlap Fellow at the Dunlap Institute for Astronomy and Astrophysics at the University of Toronto in Canada. “The new data are critical to assessing whether certain gas clouds and filaments are stable and enduring features or if they are undergoing collapse and forming new stars.”
Prior ammonia observations by many of the survey’s co-authors have targeted smaller portions of similar star-forming clouds. In these individual studies, the researchers identified sharp transitions in the amount of turbulence between the larger cloud and the smaller-scale star-forming cores, studied the stability against gravitational collapse of the gas within a young protocluster, and investigated how mass builds up along gas filaments and flows into stellar cluster-forming regions.
“These data provide a unique view of the cold dense gas involved in forming stars like our sun,” said Jaime E. Pineda, the collaboration’s other co-principal investigator, with the Max-Planck Institute for Extraterrestrial Physics in Garching, Germany. “We hope they can also help us determine how much rotation is present in the regions that will form stars; this is crucial to understand how protoplanetary disks are formed.”
The new GBT image is combined with an infrared one taken with NASA’s Wide-field Infrared Survey Explorer (WISE) telescope. The composite image illustrates how star-forming gas in this region relates to the bright stars and dark, dusty regions of the nebula.
The 100-meter GBT, which is located in the National Radio Quiet Zone, is exquisitely sensitive and uniquely able to study the molecular composition of star forming clouds and other objects in the cosmos. Future observations of the Gould Belt will provide greater insights into the conditions that give rise to stars like our sun and planets like Earth.
The Green Bank Observatory (GBO) is a facility of the National Science Foundation operated under a cooperative agreement by Associated Universities, Inc.
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This research is presented in a paper titled “The Green Bank Ammonia Survey (GAS): First results of NH3 mapping the Gould Belt,” R. Friesen and J. Pineda et al. appearing in the Astrophysical Journal Supplements [http://apj.aas.org].
Contact: Mike Holstine
The information below can be used to submit a helpdesk ticket, or find staff members that can answer your questions.
- Observer’s Helpdesk: Portal for requesting help with any aspect of using the GBT.
- Scientific support staff
- Request a computing account
- Scientific staff helpdesk tool (internal staff tool)
The tools below include GBO and third-party software packages for analyzing GBT data.
- GBTIDL: IDL suite for analysis of spectral line data.
- GBT Pipeline: Python-based routine for processing large spectral line and continuum data sets and making maps.
- CASA: Common Astronomical Software Applications (NRAO-supported tool)
- PRESTO: A third-party suite of pulsar data analysis tools.
- PSRCHIVE: Another third-party suite of pulsar data analysis tools that is particularly useful for GUPPI and VEGAS data in the PSRFITS format.
- DSPSR: Yet another third-party tool for analyzing pulsar data that is particularly useful for processing baseband voltage data.
- Data Archive: The Archive Access Tool (AAT) provided by NRAO is currently not working. The AAT can be used to search for the availability of data, but not for data retrieval. Submit a helpdesk ticket for access to archival GBT data.
- Public GBO data reduction computers: Public linux machines for data processing.
Data Archive Policy
All scientific data from NRAO and GBO telescopes are stored in an archive (with the current exception of some pulsar data taken with the GBT’s GUPPI backend). The archive contains the raw data: GBT files in FITS binary table format, export files from the VLA, and FITS-IDI files from the VLBA, including correlated data from any non-VLBA telescopes that have been used in conjunction with the VLBA. These data are reserved for the exclusive use of the observing team for a fixed period after the last observing session of a project has been completed. This proprietary period is 12 months following the last observation.
In certain circumstances (e.g. multi-epoch monitoring projects or projects that require several VLA configurations) the default proprietary period may be lengthened by the NRAO Time Allocation Commitee. Additonally, some Rapid Response Science proposals, in particular “Exploratory Time” and “Target of Opportunity”, have shorter proprietary periods. All data, taken as part of instrument calibration, engineering or software testing are immediately public with no proprietary period.
Thank you for your interest in observing with the Green Bank Telescope (GBT). Information on all aspects of proposing and observing with the GBT can be found below.(more…)
Documentation for getting started with the FastX remote access software.
FastX Remote Access Software
FastX is a commercial product that provides remote access to Linux systems by giving you a full graphical interface within your browser. No software is required on your machine except the browser. This service is available from anywhere that has a reasonable internet connection.
A note of caution however. You should avoid accessing this service from public machines such as at hotels or conferences as these machines are highly likely to be compromised and will record your login credentials.
Accessing The Software
Point your browser at https://ssh.gb.nrao.edu:3443/. You will be prompted for a username and password. This should be your NRAO/GBO/LBO username and your UNIX password.
Once you have logged in you will be presented with a screen that looks like this:
For your convenience shortcut connections to our different computing machines are provided in the left-hand panel. Pick ariel or titania if you’re actually observing and euclid, fourier, maxwell, newton, planck, thales if you want to reduce data. If your system supports it, you might see a page that allows you the choice between running the FastX session in the browser or via an app on your computer. For the latter to work, you are required to download and install the app.
While in a FastX session there is a small drop down menu in the top part of the window that appears when you hover over it and allows some control over the session:
From left to right: The first icon brings you back to the FastX starting page. The second icon (keyboard) allows you to set the keyboard. The third icon controls the sharing of the session (more later) and the forth icon allows to open files to the clipboard.
The fifths and last icon allows you to change other settings, such as the window size. Tinkering with these settings should not generally be required but on a very slow link lowering refresh rates and picture quality may help.
Ending A Session
When you are finished, click the home button in the control menu (see above) and close the browser tab that contains the session you were working in. In the FastX starting page you will see a session in the center (Disconnected Sessions). This will expire automatically after 7 days, but if you don’t need it anymore, please terminate the session to help save ressources for your fellow observers.
You can reconnect to a disconnected session by clicking the “play” button.
Be aware that if a host is rebooted the session will also disappear. If you do decide to make use of this feature please ensure that you have set your screensaver to the blank screen option so as not to waste CPU cycles and have a password set.
Please also bear in mind that due to licensing only a limited number of concurrent sessions are possible.
Is This Secure?
Short answer: yes. Access to this service is only available over the HTTPS protocol and as such all traffic between your browser and the server is encrypted. You can safely access all GBO/LBO/NRAO internal services such as ETK.
What Can’t I Do?
You cannot fire up a browser in a session and access the FastX service. This kind of recursion is not permitted. As usual the Computer Use Policy applies to all use of this service.
Sharing a Session
This software makes it possible to share a session in a similar manner to VNC but the sharing is accomplished through a web link containing a session key rather than sharing a VNC password. Sharing of sessions should only occur where there is a genuine need to do so, for instance when a member of staff is assisting an observer with actual observations or data reduction.
Sharing a session is accomplished by using the sharing icon on the session control drop down. This will open a second menu in the top-right corner of the browser window.
Click the first icon in the top left (human figure with a plus sign), which will open yet another box.
Click on Public link and switch the options from Restricted to Public.
You can copy the link and share with e.g. the staff member. This must be done in a secure manner such as encrypted IM or through Green Banks talk and draw system. Email is not a secure method. As the dialogue states, anyone with this link can connect to the session.
Once a session has been shared it must be terminated after use and not left running to connect to later.
If you already have a copy of Firefox running on another Linux machine you will not be able to start Firefox until you have killed the copy running elsewhere or taken other steps to allow it.
If your UNIX account is not based in Green Bank then start up of this service may be quite slow and performance non optimal.