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Very Large Array

Very Large Array is a astronomy topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Very Large Array rather than just read about it. In short: The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory in the southwestern United States built in the 1970s.

Very Large Array — main illustration
Very Large Array — illustration

Key takeaways

  • Very Large Array belongs to astronomy; place it in that map before memorising details.
  • Learn the definition first, then one example that makes the definition concrete.
  • Connect Very Large Array to a quantity you can measure, compute or draw — that is where exam questions come from.
  • Reproduce the core statement of Very Large Array from memory before moving on to harder problems.

Reference excerpt

The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory in the southwestern United States built in the 1970s. It lies in central New Mexico on the Plains of San Agustin, between the towns of Magdalena and Datil, approximately 50 miles (80 km) west of Socorro. The VLA comprises 28 25-meter (82 ft) radio telescopes (27 of which are operational while one is always rotating through maintenance) deployed in a Y-shaped array and all the equipment, instrumentation, and computing power to function as an interferometer. Each of the massive telescopes is mounted on double parallel railroad tracks, so the radius and density of the array can be transformed to adjust the balance between its angular resolution and its surface brightness sensitivity. Astronomers using the VLA have made key observations of black holes and protoplanetary disks around young stars, discovered magnetic filaments and traced complex gas motions at the Milky Way's center, probed the Universe's cosmological parameters, and provided new knowledge about the physical mechanisms that produce radio emission. The VLA stands at an elevation of 6,970 feet (2,120 m) above sea level. It is a component of the National Radio Astronomy Observatory (NRAO). The NRAO is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Characteristics The radio telescope comprises 27 independent antennas in use at a given time plus one spare, each of which has a dish diameter of 25 meters (82 feet) and weighs 209 metric tons (230 short tons). The antennas are distributed along the three arms of a track, shaped in a wye (or Y-shaped) configuration, each of arm measuring 21 kilometers (13 mi) long. Using the rail tracks that follow each of these arms—and that, at one point, intersect with U.S. Route 60 at a level crossing—and a specially designed lifting locomotive ("Hein's Trein"), the antennas can be physically relocated to a number of prepared positions, allowing aperture synthesis interferometry with up to 351 independent baselines: in essence, the array acts as a single antenna with a variable diameter. The angular resolution that can be reached is between 0.2 and 0.04 arcseconds. There are four commonly used configurations, designated A (the largest) through D (the tightest, when all the dishes are within 600 meters (2,000 ft) of the center point). The observatory normally cycles through all the various possible configurations (including several hybrids) every 16 months; the antennas are moved every three to four months. Moves to smaller configurations are done in two stages, first shortening the east and west arms and later shortening the north arm. This allows for a short period of improved imaging of extremely northerly or southerly sources. The frequency coverage is 74 MHz to 50 GHz (400 to 0.7 cm). The Pete V. Domenici Science Operations Center (DSOC) for the VLA is located on the campus of the New Mexico Institute of Mining and Technology in Socorro, New Mexico. The DSOC also serves as the control center for the Very Long Baseline Array (VLBA), a VLBI array of ten 25-meter (82 ft) dishes located from Hawaii in the west to the U.S. Virgin Islands in the east that constitutes the world's largest dedicated, full-time astronomical instrument.

Key science The VLA is a multi-purpose instrument designed to allow investigations of many astronomical objects, including radio galaxies, quasars, pulsars, supernova remnants, gamma-ray bursts, radio-emitting stars, the sun and planets, astrophysical masers, black holes, and the hydrogen gas that constitutes a large portion of the Milky Way galaxy as well as external galaxies. In 1989 the VLA was used to receive radio communications from the Voyager 2 spacecraft as it flew by Neptune. A search of the galaxies M31 and M32 was conducted in December 2014 through January 2015 with the intent of quickly searching trillions of systems for extremely powerful signals from advanced civilizations. It has been used to carry out several large surveys of radio sources, including the NRAO VLA Sky Survey and Faint Images of the Radio Sky at Twenty-Centimeters. In September 2017 the VLA Sky Survey (VLASS) began. This survey will cover the entire sky visible to the VLA (80% of the Earth's sky) in three full scans. Astronomers expect to find about 10 million new objects with the survey – four times more than what is presently known.

History The driving force for the development of the VLA was David S. Heeschen. He is noted as having "sustained and guided the development of the best radio astronomy observatory in the world for sixteen years." Congressional approval for the VLA project was given in August 1972, and construction began some six months later. The first antenna was put into place in September 1975 and the complex was formally inaugurated in 1980, after a total investment of $78.5 million (equivalent to $250 million in 2024). It was the largest configuration of radio telescopes in the world. In 1997 the VLA was featured in Contact, the film adaptation of the 1985 book by the same name written by Carl Sagan. With a view to upgrading the venerable 1970s technology with which the VLA was built, the VLA has evolved into the Expanded Very Large Array (EVLA). Beginning in 2001, the upgrade has enhanced the instrument's sensitivity, frequency range, and resolution with the installation of new hardware at the San Agustin site. The project was completed on time and on budget in 2012. A second phase of this upgrade may add up to eight additional antennae in other parts of the state of New Mexico, up to 190 miles (300 km) away, if funded. The decade-long EVLA upgrade project resulted in the VLA expanding its technical capacities by factors of up to 8,000. The 1970s-era electronics were replaced with state-of-the-art equipment. To reflect this increased capacity, VLA officials asked for input from both the scientific community and the public in coming up with a new name for the array, and near the completion of the EVLA project in January 2012 it was announced that the array would be renamed the "Karl G. Jansky Very Large Array". On March 31, 2012, the VLA was officially renamed in a ceremony inside the Antenna Assembly Building.

ngVLA upgrade

… excerpt ends here. Continue reading the full article.

Illustrations

Very Large Array illustration
Very Large Array: One of the 28 radio telescopes, seen here undergoing maintenance in "The Barn"[1]
One of the 28 radio telescopes, seen here undergoing maintenance in "The Barn"[1]
Very Large Array: The ngVLA prototype antenna during the handover ceremony, with the older antennae in the background.
The ngVLA prototype antenna during the handover ceremony, with the older antennae in the background.
Very Large Array: The Bracewell Radio Sundial on the VLA walking tour, seen from the south. Named for Ronald N. Bracewell, this sundial marks on the ground positions of the shadow of the central sphere (the gnomon) at different times of day and times of year. The shadow on Dec 22, 2017 falls very near the winter solstice line and the 1:00 PM (solar time) mark. The other two lines of markers north of the gnomon are for the equinoxes and the summer solstice. Additional lines of markers south of the gnomon mark positions of "shadows" of the radio sources Cygnus A and Cassiopeia A. The posts at the back of the sundial were recovered from Bracewell's radio telescope array at Stanford University, abandoned in 1980, where they had been signed by visitors with chisels at his invitation.
The Bracewell Radio Sundial on the VLA walking tour, seen from the south. Named for Ronald N. Bracewell, this sundial marks on the ground positions of the shadow of the central sphere (the gnomon) at different times of day and times of year. The shadow on Dec 22, 2017 falls very near the winter solstice line and the 1:00 PM (solar time) mark. The other two lines of markers north of the gnomon are for the equinoxes and the summer solstice. Additional lines of markers south of the gnomon mark positions of "shadows" of the radio sources Cygnus A and Cassiopeia A. The posts at the back of the sundial were recovered from Bracewell's radio telescope array at Stanford University, abandoned in 1980, where they had been signed by visitors with chisels at his invitation.
Very Large Array illustration

Worked examples

Example 1 — a first encounter with Very Large Array

Start with the simplest possible case. Write down what Very Large Array claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In astronomy, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Very Large Array before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Very Large Array ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Very Large Array

In research
Very Large Array appears in astronomy research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry
Engineering practice reuses Very Large Array in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom
Very Large Array is common in secondary-school and first-year university syllabi. It links to neighbouring topics 1980 establishments in New Mexico, Astronomical observatories in New Mexico, Buildings and structures in Socorro County, New Mexico, so understanding it makes those chapters shorter.
In everyday life
Look for Very Large Array outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.
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How to study Very Large Array in 20 minutes

  1. Read the reference excerpt below once, without taking notes.
  2. Close the page and write down what Very Large Array means in your own words.
  3. Compare your version with the excerpt and mark what you missed.
  4. Work through the three examples above with pen and paper.
  5. Explain Very Large Array out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Very Large Array in simple terms?

The Karl G. Jansky Very Large Array (VLA) is a centimeter-wavelength radio astronomy observatory in the southwestern United States built in the 1970s.

Why does Very Large Array matter?

Because it connects several astronomy ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Very Large Array?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Very Large Array.

Tags

  • 1980 establishments in New Mexico
  • Astronomical observatories in New Mexico
  • Buildings and structures in Socorro County, New Mexico
  • Interferometric telescopes
  • Museums in Socorro County, New Mexico
  • Radio telescopes
  • Science museums in New Mexico

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