Nav: Home

Zwicky Transient Facility nabs several supernovae a night

February 07, 2019

The results are rolling in from Caltech's newest state-of-the-art sky-surveying camera, which began operations at the Palomar Observatory in March 2018. Called the Zwicky Transient Facility, or ZTF, the new instrument has so far discovered 50 small near-Earth asteroids and more than 1,100 supernovae, and it has observed more than 1 billion stars in the Milky Way galaxy. One of the near-Earth asteroids discovered by ZTF, called 2019 AQ3, has an orbital period of just 165 days, the shortest known "year" for any asteroid.

"It's a cornucopia of results," says Shri Kulkarni, the principal investigator of ZTF and the George Ellery Hale Professor of Astronomy and Planetary Science at Caltech. Recently, several new papers about early results and technical specifications for ZTF were accepted for publication in the journal Publications of the Astronomical Society of the Pacific. "We are up and running and delivering data to the astronomical community. Astronomers are energized."

ZTF uses the 48-inch Samuel Oschin Telescope at Palomar to survey the northern skies for anything that explodes, moves, or changes in brightness. Because the ZTF camera covers 240 times the size of the full moon in a single night-sky image, it is discovering the most fleeting, or short-lived, of cosmic events, which were impossible to catch before now.

"ZTF is surveying the whole northern sky every three nights," says Kulkarni. "It's already discovering a few supernovae a night, and we expect that rate to go up."

The cost to develop and run ZTF is about $24 million, with about $11 million of the funding coming from the U.S. government via the National Science Foundation (NSF) and the rest coming from an international collaboration of partners. Additional support comes from the Heising-Simons Foundation, along with Caltech itself.

"The start of routine operations of ZTF marks a new era in our ability to capture the nightly and hourly changes transpiring in the universe," says Anne Kinney, NSF assistant director for mathematical and physical sciences. "They are now recording real-time events from distant supernovae to nearby asteroids and are poised to discover the violent mergers and explosions generating gravitational-wave events."

Because nearly half of ZTF is paid for by the U.S. government, nearly half of its observations are shared publicly in near-real-time with the astronomy community. When varying, or transient, objects are detected, an automated alert system is activated, sending notices out to astronomers, who then quickly follow up on notable objects of interest using other telescopes, including the 60-inch and 200-inch Hale telescopes at Palomar. An NSF-funded program called GROWTH, with 18 international observatories in the Northern Hemisphere, also follows up on the ZTF alerts.

All data from the ZTF camera are sent via a microwave network managed by UC San Diego to IPAC, an astronomy center at Caltech that processes and archives up to 4 terabytes of data each night. "This is the first time IPAC has generated real-time alerts from a survey and the first time a survey has made public up to hundreds of thousands of alerts per night," says George Helou, ZTF co-investigator and executive director of IPAC. Ultimately, the detailed data are also made available to astronomers around the world through IPAC.

"It takes only 10 to 20 minutes from the time a transient observation is made to the time the alert goes out," says Matthew Graham, the ZTF project scientist at Caltech. Graham specializes in "big data," and specifically how to handle and process large streams of astronomical data. "It's like running a major newsroom. We've never operated at this scale before, and handling all the data is quite a feat," he says.

Discoveries from ZTF so far include not only new supernovae, binary stars, and asteroids but two black holes caught shredding stars. As stars wander too close to black holes, they can be "tidally disrupted" by the gravity of the black hole and stretched into oblivion. Graham says that he and the team working on the tidal disruption data, led by Suvi Gezari of the University of Maryland, got fed up with referring to the technical names for the objects, consisting of long strings of numbers. "We decided to nickname them Ned Stark and Jon Snow, after Game of Thrones characters," he says.

ZTF also caught two near-Earth asteroids, 2018 NX and 2018 NW, that zipped by Earth at distances of only 72,000 miles and 76,000 miles away, respectively, or approximately a third of the distance between Earth and the moon. These discoveries were enabled by the NSF-funded GROWTH program.

On January 4, 2019, ZTF caught the near-Earth asteroid 2019 AQ3. "This is one of the largest asteroids with an orbit entirely within the orbit of Earth--a very rare species," says Quanzhi Ye, a postdoctoral scholar at IPAC who first spotted the asteroid in the ZTF data.

Tom Prince, one of the co-investigators of ZTF and the Ira S. Bowen Professor of Physics at Caltech, says that the instrument is particularly adept at identifying new gravitational-wave sources--in particular, pairs of compact stars like white dwarfs--that will be observed with future space-based gravitational-wave detectors.

"Because we cover so much sky so often, we can find these rare exotic binary systems that contain two white dwarf stars, each about the size of Earth but about half the mass of our sun. Their orbits are predicted to become smaller and smaller because of the loss of energy due to gravitational waves."

ZTF is also laying the groundwork for the future NSF-funded Large Synoptic Survey Telescope (LSST), which will, in every exposure, scan a volume of sky 13 times larger than that scanned by ZTF. LSST is scheduled to begin operations in 2022.

"The same alert techniques that ZTF is developing for international networks of observatories to follow up on its findings will be applied to LSST when it joins the search," says Kinney.
The newest ZTF papers are: "The Zwicky Transient Facility: System Overview, Performance, and First Results," led by Eric Bellm of the University of Washington; "The Zwicky Transient Facility: Science Objectives," led by Graham; "The Zwicky Transient Facility: Data Processing, Products, and Archive," led by Frank Masci of IPAC; "Machine Learning for the ZTF," led by Ashish Mahabal of Caltech; "The Zwicky Transient Facility Alert Distribution System," led by Maria Patterson of the University of Washington; "The GROWTH Marshal: A Dynamic Science Portal for Time-domain Astronomy," led by Mansi Kasliwal of Caltech; and "A Morphological Classification Model to Identify Unresolved PanSTARRS Sources: Application in the ZTF Real-Time Pipeline," led by Yutaro Tachibana of Tokyo Institute of Technology and Caltech and Adam Miller of Northwestern University and the Adler Planetarium.

California Institute of Technology

Related Black Hole Articles:

Scientists make waves with black hole research
Scientists at the University of Nottingham have made a significant leap forward in understanding the workings of one of the mysteries of the universe.
Collapsing star gives birth to a black hole
Astronomers have watched as a massive, dying star was likely reborn as a black hole.
When helium behaves like a black hole
A team of scientists has discovered that a law controlling the bizarre behavior of black holes out in space -- is also true for cold helium atoms that can be studied in laboratories.
Star in closest orbit ever seen around black hole
Astronomers have found evidence of a star that whips around a likely black hole twice an hour.
Tail of stray black hole hiding in the Milky Way
By analyzing the gas motion of an extraordinarily fast-moving cosmic cloud in a corner of the Milky Way, Astronomers found hints of a wandering black hole hidden in the cloud.
Hubble gazes into a black hole of puzzling lightness
The beautiful spiral galaxy visible in the center of the image is known as RX J1140.1+0307, a galaxy in the Virgo constellation imaged by the NASA/ESA Hubble Space Telescope, and it presents an interesting puzzle.
Clandestine black hole may represent new population
Astronomers have combined data from NASA's Chandra X-ray Observatory, the Hubble Space Telescope and the National Science Foundation's Karl G.
When will a neutron star collapse to a black hole?
Astrophysicists from Goethe-University Frankfurt have found a simple formula for the maximum mass of a rotating neutron star and hence answered a question that had been open for decades.
Behemoth black hole found in an unlikely place
Astronomers have uncovered a near-record breaking supermassive black hole, weighing 17 billion suns, in an unlikely place: in the center of a galaxy in a sparsely populated area of the universe.
Behemoth black hole found in an unlikely place
Astronomers have uncovered one of the biggest supermassive black holes, with the mass of 17 billion Suns, in an unlikely place: the centre of a galaxy that lies in a quiet backwater of the Universe.

Related Black Hole Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Digital Manipulation
Technology has reshaped our lives in amazing ways. But at what cost? This hour, TED speakers reveal how what we see, read, believe — even how we vote — can be manipulated by the technology we use. Guests include journalist Carole Cadwalladr, consumer advocate Finn Myrstad, writer and marketing professor Scott Galloway, behavioral designer Nir Eyal, and computer graphics researcher Doug Roble.
Now Playing: Science for the People

#530 Why Aren't We Dead Yet?
We only notice our immune systems when they aren't working properly, or when they're under attack. How does our immune system understand what bits of us are us, and what bits are invading germs and viruses? How different are human immune systems from the immune systems of other creatures? And is the immune system so often the target of sketchy medical advice? Those questions and more, this week in our conversation with author Idan Ben-Barak about his book "Why Aren't We Dead Yet?: The Survivor’s Guide to the Immune System".