Pan-STARRS

Pan-STARRS logo

The Panoramic Survey Telescope and Rapid Response System (Pan-STARRS) is a planned array of astronomical cameras and telescopes and computing facility that will survey the sky on a continual basis, including accurate astrometry and photometry of detected objects. By detecting any differences from previous observations of the same areas of the sky, it is expected to discover a very large number of new asteroids, comets, variable stars and other celestial objects. Its primary mission is to detect near-Earth objects that threaten impact events and is expected to create a database of all objects visible from Hawaii (three-quarters of the entire sky) down to apparent magnitude 24. Pan-STARRS is funded in large part by the U.S. Air Force through their Research Labs.

The first Pan-STARRS telescope, PS1, is located at the summit of Haleakala on Maui, Hawaii, and went online on December 6, 2008, under the administration of the University of Hawaii.^[1][2] PS1 began full time science observations on May 13, 2010,^[3] and the PS1 Science Mission is underway, with operations funded by The PS1 Science Consortium or PS1SC, a consortium including the Max Planck Society in Germany, National Central University in Taiwan, Edinburgh, Durham and Queen's Belfast Universities in the UK, and Johns Hopkins and Harvard Universities in the United States and the Las Cumbres Observatory Global Telescope Network.

The Pan-STARRS Project is a collaboration between the University of Hawaii Institute for Astronomy, MIT Lincoln Laboratory, Maui High Performance Computing Center and Science Applications International Corporation. Telescope construction is funded by the United States Air Force. Having completed PS1, the Pan-STARRS Project is now focusing on building PS2, and then the full array of four telescopes, sometimes called PS4. Completing the array of four telescopes is estimated at a total cost of US$100 million for the entire array.^[1]

Instruments

Pan-STARRS will use four 1.8 m telescopes that will be located either at Mauna Kea or Haleakala in Hawaii. All four telescopes in the final PS4 system will point in the same direction: data will be compared to remove CCD artifacts due to chip defects and bad pixels and cosmic rays, and then the light input will be summed to give the equivalent of a single 3.6 m telescope. Funding has been obtained to construct all four telescopes.

A prototype telescope PS1 has been constructed, and saw first light using a low-resolution camera in June 2006. The telescope has a 3° field of view, which is extremely large for telescopes of this size, and is equipped with the largest digital camera ever built, recording almost 1.4 billion pixels per image. The focal plane has 60 separately mounted close packed CCDs arranged in an 8 × 8 array. The corner positions are not populated, because the optics do not illuminate the corners. Each CCD device, called an Orthogonal Transfer Array (OTA), has 4800 × 4800 pixels, separated into 64 cells, each of 600 × 600 pixels. This gigapixel camera or 'GPC' saw first light on August 22, 2007, imaging the Andromeda Galaxy.

After initial technical difficulties that were later solved, PS1 began full operation on May 13, 2010.^[4] Nick Kaiser, principal investigator of the Pan-STARRS project, summed it up saying “PS1 has been taking science-quality data for six months, but now we are doing it dusk-to-dawn every night.” (quote: June 15, 2010).

Each image requires about 2 gigabytes of storage and exposure times will be 30 to 60 seconds (good enough to record objects down to apparent magnitude 24), with an additional minute or so used for computer processing. Since images will be taken on a continuous basis, it is expected that 10 Terabytes of data will be acquired by PS4 every night. Because of this very large volume of data, the computer processing will record the positions and magnitudes of all objects in the image after which the image itself will be discarded. Comparing against a database of known unvarying objects compiled from earlier observations will yield objects of interest: anything that has changed brightness and/or position for any reason. As of June 30/10 University of Hawaii in Honolulu received an $8.4 million contract modification under the PanSTARRS multi-year program to develop and deploy a telescope data management system for the project. At this time, all funds have been committed (FA9451-06-2-0338; P00008)

The very large field of view of the telescopes and the short exposure times will enable approximately 6000 square degrees of sky to be imaged every night. The entire sky is 4π steradians, or 4π × (180/π)² ≈ 41,253.0 square degrees, of which about 30,000 square degrees are visible from Hawaii, which means that the entire sky can be imaged in a period of 40 hours (or about 10 hours per night on four days). Given the need to avoid times when the Moon is bright, this means that an area equivalent to the entire sky will be surveyed four times a month, which is entirely unprecedented.

The project is believed to be achievable with existing technology, although on a larger scale than anything previously attempted.

Science

Systematically surveying the entire sky on a continuous basis is an unprecedented project and is expected to produce a dramatically larger number of discoveries of various types of celestial objects. For instance, the current leading asteroid discovery survey, the Mount Lemmon Survey,^[5][6] goes down to apparent magnitude 21.5 V and concentrates its searches mostly near the ecliptic;^[7] Pan-STARRS will go 3 magnitudes fainter and cover the entire sky visible from Hawaii. The ongoing survey will also complement the efforts to map the infrared sky by the NASA WISE orbital telescope, with the results of one survey complementing and extending the other.

Military limitations

According to Defense Industry Daily^[8] there will be some significant limitations put on the PS1 survey to avoid recording sensitive objects "The new 1400-megapixel PS1 camera is expected to uncover 100,000 new asteroids. As a condition of funding, however, the USAF requires that Pan-STARRS software automatically black out the trajectories of passing satellites. In 2009, that restriction apparently meant usable images from 68% of the total sky at any given time, forcing additional observation sessions for blacked-out areas at more suitable times. As of March 2010, however, improvements in image processing have reportedly boosted the figure to 76% viewing field availability"

Solar system

In addition to the large number of expected discoveries in the main asteroid belt, Pan-STARRS is expected to detect at least 100,000 Jupiter Trojan asteroids (compared to 2900 known as of end-2008); at least 20,000 Kuiper belt objects (compared to 800 known as of mid-2005); thousands of Trojan asteroids of Saturn, Uranus and Neptune (currently six Neptune Trojans are known,^[9] and none for Saturn and Uranus); and large numbers of Centaurs and comets.

Apart from drastically adding to the number of known solar system objects, Pan-STARRS will remove or mitigate the observational bias inherent in many current surveys. For instance, among currently known objects there is a bias favoring low orbital inclination, and thus an object such as Makemake escaped detection until recently despite its bright apparent magnitude of 17, which is not much fainter than Pluto. Also, among currently known comets there is a bias favoring those with short perihelion distances. Reducing the effects of this observational bias will enable a more complete picture of solar system dynamics. For instance it is expected that the number of Jupiter Trojans larger than 1 km may in fact roughly match the number of main asteroid belt objects, although the currently known population of the latter is several orders of magnitude larger. Pan-STARRS data will elegantly complement the WISE (infrared) survey. WISE infrared images will permit an estimate of size for Asteroids and Trojan objects tracked over longer periods of time by Pan-STARRS.

Pan-STARRS may detect "interstellar debris" or "interstellar interlopers" flying through the solar system. During the formation of a planetary system it is thought that a very large number of objects are ejected due to gravitational interactions with planets (as many as 10¹³ such objects in the case of our solar system). Objects ejected by planetary systems around other stars might plausibly be flying throughout the galaxy and some may pass through our solar system.

Pan-STARRS may detect collisions involving small asteroids. These are quite rare and none have yet been observed, but with the drastically larger number of asteroids that will be discovered it is expected from statistical considerations that some collision events may be observed.

Pan-STARRS will also likely detect a number of Kuiper belt objects the size of Pluto or larger, similar to Eris.^{[citation needed][dubious – discuss]}

Beyond the solar system

It is expected that Pan-STARRS will discover an extremely large number of variable stars, including such stars in other nearby galaxies; in fact, this may lead to the discovery of hitherto unknown dwarf galaxies. In discovering a large number of Cepheid variables and eclipsing binary stars, it will help determine distances to nearby galaxies with greater precision. It is expected to discover a large number of Type Ia supernovae in other galaxies, which are important in studying the effects of dark energy, and also optical afterglows of gamma ray bursts.

Because very young stars (such as T Tauri stars) are usually variable, Pan-STARRS should discover a large number of these and improve our understanding of them. It is also expected that Pan-STARRS may discover a large number of extrasolar planets by observing their transits across their parent stars, as well as gravitational microlensing events.

Pan-STARRS will also measure proper motion and parallax and should thereby discover a large number of brown dwarfs and white dwarfs and other nearby faint objects, and it should be able to conduct a complete census of all stars within 100 parsecs of the Sun. Prior proper motion and parallax surveys often did not detect faint objects such as the recently-discovered Teegarden's star, which are too faint for projects such as Hipparcos.

Also, by identifying stars with large parallax but very small proper motion for followup radial velocity measurements, Pan-STARRS may even be able to permit the detection of hypothetical Nemesis-type objects if these actually exist.

Discoveries

• Pan-STARRS Telescope Finds New Distant Comet: Astronomers at the University of Hawaii at Manoa have discovered a new comet that they expect will be visible to the naked eye in early 2013. The comet is now about 700 million miles (1.2 billion km) from the sun, placing it beyond the orbit of Jupiter. It is currently too faint to be seen without a telescope with a sensitive electronic detector.

The comet is expected to be brightest in February or March 2013, when it makes its closest approach to the sun. At that time, the comet is expected to be visible low in the western sky after sunset, but the bright twilight sky may make it difficult to view. The comet is named C/2011 L4 (PANSTARRS). It most likely originated in the Oort cloud, a cloud of cometlike objects located in the distant outer solar system. It was probably gravitationally disturbed by a distant passing star, sending it on a long journey toward the sun. ^[10]

• SN 2008id (type 1a supernova), confirmed by Keck observatory via redshift.^[11]
• 2010 ST₃: This NEA, which has a very slight possibility of colliding with Earth in 2098, was discovered by Pan-STARRS on 16 September 2010. This is the first NEA to be discovered by the Pan-STARRS program. The object is 30-65 meters across^[12][13] and if it entered Earth's atmosphere would probably explode and potentially devastate an area of several hundred square miles at the surface. It was expected to pass within about 4 million miles of Earth in mid-October 2010.^[14]
• P/2010 T2: First reported on 16 October 2010, this faint ~20th-magnitude object is the first comet to be discovered by the Pan-STARRS program. Even at perihelion in the summer of 2011 at 3.73 AU it will only be magnitude 19.5. It has an orbital period of 13.2 years and is a member of the short-period Jupiter family of comets.^[15][16]
• C/2011 L4 (PANSTARRS), a comet discovered on the night of June 5 and 6, 2011. It will make its closest approach to the Sun in February or March 2013.^[17]

See also

• Large Synoptic Survey Telescope

References

1. ^ ^{a b} "Watching and waiting". The Economist. 2008-12-04. http://www.economist.com/science/displaystory.cfm?story_id=12719347. Retrieved 2008-12-06.  From the print edition
2. ^ Robert Lemos (2008-11-24). "Giant Camera Tracks Asteroids". Technology Review (MIT). http://www.technologyreview.com/computing/21705/page1/. Retrieved 2008-12-06. 
3. ^ Pan-STARRS 1 Telescope Begins Science Mission
4. ^ Handwerk, Brian (June 22, 2010). "World's Largest Digital Camera to Watch for Killer Asteroids". National Geographic News. http://news.nationalgeographic.com/news/2010/06/100622-science-space-digital-camera-asteroid-telescope. Retrieved 26 June 2010. 
5. ^ Mt. Lemmon Survey (G96) is a part of Catalina Sky Survey, another two parts are Siding Spring Survey (E12) and Catalina Sky Survey (703) itself.
6. ^ Summary of PHA and NEA Discoveries by Discoverers
7. ^ "Sky Coverage Plots". IAU Minor Planet Center. http://scully.cfa.harvard.edu/~cgi/SkyCoverage.html. 
8. ^ http://www.defenseindustrydaily.com/8M-for-Astronomy-Asteroid-Assessment-04828/
9. ^ List Of Neptune Trojans
10. ^ [1]
11. ^ Pan-STARRS' first supernova
12. ^ 2010 ST3 at JPL Small Body Database
13. ^ Conversion of Absolute Magnitude to Diameter
14. ^ "Maui scope spots asteroid that could hit Earth in 2098". Honolulu Star-Advertiser. 28 September 2010. http://www.staradvertiser.com/news/20100928_Maui_scope_spots_asteroid_that_could_hit_Earth_in_2098.html. Retrieved 28 September 2010. 
15. ^ "Recent Discoveries – Oct 12 to 18". The Transient Sky – Comets, Asteroids, Meteors. https://transientsky.wordpress.com/2010/10/19/recent-discoveries-oct-12-to-18/. 
16. ^ MPEC 2010-U07
17. ^ SPACE.com Staff. "Newfound Comet Will Swing By Earth in 2013". http://www.space.com/11996-comet-earth-2013-flyby-c2011l4-pan-starrs.html. Retrieved 18 June 2011. 

External links

• Pan-STARRS web site
• PS1 Science Consortium web site
• PROJECT PAN-STARRS AND THE OUTER SOLAR SYSTEM
• New telescope will hunt dangerous asteroids
• World's biggest digital camera to join asteroid search
• Is there a Planet X?
• Early warning of dangerous asteroids and comets