# Arecibo’s Continuing Revelations

By Larry Klaes

2008 marks the 45th year of operation for the Arecibo Observatory, the largest single radio telescope on Earth. Maintained and operated by Cornell University since its opening in 1963, Arecibo has definitely made its share of contributions to our knowledge of the cosmos.

To cite but a few examples, astronomers beamed powerful radar signals from the one thousand foot wide radio telescope onto the planet Mercury in 1965 to determine its rotation rate and again in 2007 to demonstrate that the world’s core is molten. Arecibo confirmed the existence of neutron stars, the remains of massive suns that had become supernovae, in 1968; in 1990 it found the first known exoplanets around a type of rapidly rotating neutron star called a pulsar. The first deliberate electromagnetic message aimed to any technological alien intelligences in the Milky Way was broadcast from Arecibo in 1974. In 1989, the observatory’s radar returned the first images of a passing planetoid, revealing its shape and dimensions to scientists.

For six months in 2007, workers gave the giant radio telescope’s platform and focal-point structure, which hangs high above the Puerto Rican jungle where Arecibo resides, its first serious paint job in four decades. This project was designed to keep Arecibo operating efficiently for many years to come, even as its near-term future is being threatened by a loss of funding from the National Science Foundation (NSF), which operates the observatory in a cooperative agreement with Cornell University.

Arecibo’s first assignment after its makeover was to examine the space object known as 3200 Phaethon, named after the son of the Greek Sun god Helios – an appropriate designation, as this relatively small celestial object comes closer to our yellow star than any other known member of the Solar System.

Image: Arecibo’s ongoing work not only teaches us about the cosmos but provides critical planetary defense by identifying Earth-crossing asteroids. Credit: NAIC/Arecibo Observatory, a facility of the NSF.

The first planetoid to be discovered by a spacecraft (the InfraRed Astronomical Satellite, IRAS, in 1983), Phaethon may actually be an extinct comet, as debris from this body is also the source of the Geminids meteor shower, which appears in Earth’s sky every mid-December.

A team of scientists working with and at Arecibo, which include Cornell University assistant professor of astronomy Jean-Luc Margot, bounced radar beams off Phaethon last December. The team wants to know more about how solar energy affects planetoids that travel near the Sun, which can have their orbits and rotation rates gradually changed over time through long exposure to sunlight. What the scientists learn from these observations will help in our understanding of the many small space bodies that continually cross Earth’s orbit, some of which may one day be on a collision course with our planet and threaten all life upon it.

Arecibo’s impressive capabilities were also in evidence at the American Astronomical Society’s (AAS) 211st meeting in Austin, Texas, last month, when astronomers announced the discovery of methanimine and hydrogen cyanide, two types of molecules which form the amino acid glycine when combined with water. Amino acids are the building blocks of proteins, which are large organic compounds that perform many important functions in the cells of every living being on Earth.

These molecules were found in a galaxy named Arp 220 located some 250 million light years from our Milky Way galaxy. The starlight emitted from Arp 220 currently being witnessed by astronomers on Earth took 250 million years traveling at the speed of light (186,000 miles per second) to reach our planet across intergalactic space. When that light left the far-off island of stars all those ages ago, dinosaurs had yet to appear on Earth.

“The fact that we can observe these substances at such a vast distance means that there are huge amounts of them in Arp 220,” said Emmanuel Momjian, one of the Arecibo astronomers who made the find. “It is indeed very intriguing to find that the ingredients of life appear in large quantities where new stars and planets are born.”

The Arecibo astronomers utilized the telescope’s main spectrometer to make the discovery of these molecules (a spectrometer is a device that measures light properties at specific frequencies of the electromagnetic spectrum). Team member Tapasi Ghosh noted that they were not searching for any particular molecule in that active galaxy, so their finding was “incredibly exciting.”

Another astronomical find involving Arecibo announced at the same AAS meeting in Texas regards a new determination about neutron stars and black holes, two types of aging massive suns that collapse and crush themselves into incredible densities. Arecibo Observatory astronomer Paulo Freire and his team studied the binary pulsar M5 B in the globular star cluster Messier 5, located in the constellation of Serpens the Snake, where the galaxy Arp 220 also resides. Using the facility’s spectrometer from 2001 to 2007 to measure the rotating beams of powerful radiation emitted from the neutron star’s poles, Freire was able to determine the mass of this dense stellar remnant accurately.

Freire discovered that this particular neutron star remained in its current state at 1.9 times the mass of our Sun. Astronomers previously thought neutron stars would collapse into black holes at less massive states.

“[This find] means that to form a black hole, more mass is needed than previously thought,” Freire told the Cornell Chronicle. “Thus, in our Universe, black holes might be more rare and neutron stars slightly more abundant.”

The above stories represent just some of the dozens of astronomical projects currently being conducted at the observatory. No doubt even more amazing things will be learned about our cosmos in coming years, thanks to that giant dish sitting on a distant island in the Caribbean Sea.

Comments on this entry are closed.

• dad2059 February 13, 2008, 9:52

The Arecibo scope has always been a very valuable tool to explore the Cosmos. I hope it will always be funded by somebody with foresight and vision.

It would be a shame to let it die an ignoble death. Carl Sagan must be spinning in his grave.

• ljk February 14, 2008, 10:25

Arecibo Observatory astronomers discover first
near-Earth triple asteroid just 7 million miles away

Feb. 13, 2008

Once considered just your average single asteroid, 2001
SN263 has now been revealed as the first near-Earth triple
asteroid ever found. The asteroid — with three bodies
orbiting each other — was discovered this week by
astronomers at the radar telescope at the National Science
Foundation’s (NSF) Arecibo Observatory in Puerto Rico.

Cornell and Arecibo astronomer Michael C. Nolan said he
and his colleagues made the discovery when they obtained
radar images Feb. 11. The group subsequently took more
images to learn that the three objects — about 7 million
miles from Earth — are rotating around each other.

• george scaglione February 14, 2008, 15:00

ljk,with more excitement growing over the subject of possible visits to near earth asteroids this could not come at a better time! i mean look at it logically,7 million miles,not as close as the moon ,not as far as mars,a perfect way to go one step further out into space! an intermediate step if you will. perfect. thank you your friend george

• James M. Essig February 14, 2008, 18:27

Hi George and ljk;

I could imagine that traveling to an asteriod 7 million miles away could be done using a CEV based platform much more readily that a manned mission to Mars. I think the shorter flight time of the CEV based vehicle to the asteroid and the much easier slow down afforded by closing in on a body with a very small gravity well and no atmosphere would be a much lower cost mission that could galvanize public interest in manned space-flight again like nothing else previously during the past 30 years. Afterward, we could reach for Mars and then eventually beyond.

Thanks;

• ljk February 22, 2008, 13:29

EuroNews looks at comets and asteroids

22 February 2008

The menacing mass of a rolling asteroid flying past
Earth at more than 10 km/s is tracked by the giant
telescope of Arecibo in Puerto Rico as well as the
powerful radar of Wachtberg in Germany. At ESA,
these celestial bodies are studied with passion, in
preparation for a possible, hazardous impact.

http://www.esa.int/esaCP/SEMBUG3CXCF_index_0.html

• ljk April 1, 2008, 15:04

NASA SCIENTISTS IDENTIFY SMALLEST KNOWN BLACK HOLE

GREENBELT, Md. – Using a new technique, two NASA scientists have identified the lightest known black hole. With a mass only about 3.8 times greater than our Sun and a diameter of only 15 miles, the black hole lies very close to the minimum size predicted for black holes that originate from dying stars.

“This black hole is really pushing the limits. For many years astronomers have wanted to know the smallest possible size of a black hole, and this little guy is a big step toward answering that question,” says lead author Nikolai Shaposhnikov of NASA’s Goddard Space Flight Center in Greenbelt, Md.

Shaposhnikov and his Goddard colleague Lev Titarchuk are presenting their results on Monday, March 31, at the American Astronomical Society High-Energy Astrophysics Division meeting in Los Angeles, Calif. Titarchuk also works at George Mason University in Fairfax, Va., and the U.S. Naval Research Laboratory in Washington, D.C. They will describe their results in more detail in a media telecon on April 1 at 1:30 p.m. EDT.

The tiny black hole resides in a Milky Way Galaxy binary system known as XTE J1650-500, named for its sky coordinates in the southern constellation Ara. NASA’s Rossi X-ray Timing Explorer (RXTE) satellite discovered the system in 2001. Astronomers realized soon after J1650’s discovery that it harbors a normal star and a relatively lightweight black hole. But the black hole’s mass had never been measured to high precision.

The method used by Shaposhnikov and Titarchuk has been described in several papers in the Astrophysical Journal. It uses a relationship between black holes and the inner part of their surrounding disks, where gas spirals inward before making the fatal plunge. When the feeding frenzy reaches a moderate rate, hot gas piles up near the black hole and radiates a torrent of X-rays. The X-ray intensity varies in a pattern that repeats itself over a nearly regular interval. This signal is called a quasi-periodic oscillation, or QPO.

Astronomers have long suspected that a QPO’s frequency depends on the black hole’s mass. In 1998, Titarchuk realized that the congestion zone lies close in for small black holes, so the QPO clock ticks quickly. As black holes increase in mass, the congestion zone is pushed farther out, so the QPO clock ticks slower and slower. To measure the black hole masses, Shaposhnikov and Titarchuk use archival data from RXTE, which has made exquisitely precise measurements of QPO frequencies in at least 15 black holes.

Last year, Shaposhnikov and Titarchuk applied their QPO method to three black holes whose masses had been measured by other techniques. In their new paper, they extend their result to seven other black holes, three of which have well-determined masses. “In every case, our measurement agrees with the other methods,” says Titarchuk. “We know our technique works because it has passed every test with flying colors.”

When Shaposhnikov and Titarchuk applied their method to XTE J1650-500, they calculated a mass of 3.8 Suns, with a margin of uncertainty of only half a Sun. This value is well below the previous black hole record holder with a reliable mass measurement, GRO 1655-40, which tips the scales at about 6.3 Suns.

Below some unknown critical threshold, a dying star should produce a neutron star instead of a black hole. Astronomers think the boundary between black holes and neutron stars lies somewhere between 1.7 and 2.7 solar masses. Knowing this dividing line is important for fundamental physics, because it will tell scientists about the behavior of matter when it is scrunched into conditions of extraordinarily high density.

Despite the diminutive size of this new record holder, future space travelers had better beware. Smaller black holes like the one in J1650 exert stronger tidal forces than the much larger black holes found in the centers of galaxies, which make the little guys more dangerous to approach. “If you ventured too close to J1650’s black hole, its gravity would tidally stretch your body into a strand of spaghetti,” says Shaposhnikov.

Shaposhnikov adds that RXTE is the only instrument that can make the high-precision timing observations necessary for this line of research. “RXTE is absolutely crucial for these black hole mass measurements,” he says.

For related images to this story, please visit on the Web:

http://www.nasa.gov/centers/goddard/news/topstory/2008/smallest_blackhole.html

• ljk May 12, 2008, 14:03

The Arecibo Arp 220 Spectral Census I: Discovery of the Pre-Biotic Molecule Methanimine and New Cm-wavelength Transitions of Other Molecules
Authors: C. J. Salter, T. Ghosh, B. Catinella, M. Lebron, M. S. Lerner, R. Minchin, E. Momjian

(Submitted on 8 May 2008)

Abstract: An on-going Arecibo line search between 1.1 and 10 GHz of the prototypical starburst/megamaser galaxy, Arp 220, has revealed a spectrum rich in molecular transitions. These include the “pre-biotic” molecules: methanimine (CH$_{2}$NH) in emission, three $v_{2}=1$ direct l-type absorption lines of HCN, and an absorption feature likely to be from either $^{18}$OH or formic acid (HCOOH). In addition, we report the detection of two, possibly three, transitions of $\lambda$4-cm excited OH not previously detected in Arp~220 which are seen in absorption, and a possible absorption feature from the 6.668-GHz line of methanol.

This marks the first distant extragalactic detection of methanimine, a pre-biotic molecule. Also, if confirmed, the possible methanol absorption line presented here would represent the first extragalactic detection of methanol at a distance further than 10 Mpc. In addition, the strong, previously undetected, cm-wave HCN $v_{2}=1$ direct l-type lines will aid the study of dense molecular gas and active star-forming regions in this starburst galaxy.

Comments: 25 pages, 10 figures. Accepted for publication in AJ

Subjects: Astrophysics (astro-ph)

Cite as: arXiv:0805.1205v1 [astro-ph]

Submission history

From: Emmanuel Momjian [view email]

[v1] Thu, 8 May 2008 17:31:57 GMT (46kb)

http://arxiv.org/abs/0805.1205

• ljk January 2, 2009, 15:48

China Exclusive: China starts building world’s largest radio telescope

http://english.china.com/zh_cn/news/society/11020309/20081226/15255407.html

China Exclusive: China starts building world’s largest radio telescope

2008-12-26 18:54:55

GUIYANG, Dec. 26 (Xinhua) — China officially started construction of
a Five-hundred-meter Aperture Spherical Telescope (FAST), the largest
in the world, in a remote southwest region on Friday.

Preparation and research for the project took some 14 years.

The dish-like telescope, as large as 30 football fields, will stand in
a region of typical Karst depressions in Guizhou Province when it’s
done in 2013.

Karst depressions are usually located in regions plentiful in
limestone and dolomite, where groundwater has enlarged openings to
form a subsurface drainage system.

The facility will greatly improve China’s capacity for astronomical
observation, according to the National Astronomical Observatory (NAO),
the major developer of the program.

FAST’s main spherical reflector will be composed of 4,600 panels. Its
observation sensitivity will be 10 times more powerful than the 100-m
aperture steerable radio telescope in Germany. Its overall capacity
will be 10 times larger than what is now the world’s largest (300 m)
Arecibo radio telescope developed by the United States, according to
Nan Rendong, the chief scientist of the project and an NAO researcher.

The project, costing more than 700 million yuan (102.3 million U.S.
dollars), will allow international astronomers and scientists to
discover more of the secrets of the universe based on cutting-edge
technologies, said Zhang Haiyan, an NAO official in charge of
construction.

Scientists have so far observed only 1,760 pulsars, which are strongly
magnetized spinning cores of dead stars. With the help of FAST, they
could find as many as 7,000 to 10,000 within a year, Nan said.

Pulsars have allowed scientists to make several major discoveries,
such as confirmation of the existence of gravitational radiation as
predicted by the theory of general relativity.

FAST could also be a highly sensitive passive radar to monitor
satellites and space debris, which would be greatly helpful for
China’s ambitious space program.

The telescope could also help to look for other civilizations by
detecting and studying communication signals in the universe.

Chinese scientists and officials selected Dawodang, Pingtang County as
the site, where a Karst valley will match the shape of the huge bowl-
like astronomical instrument.

The sparsely populated, underdeveloped region will provide a quiet
environment to ensure the electromagnetic waves, the crucial
requirement of operation, are not interrupted by human activities.

Construction of a new residential area about 60 km away also began on
Friday to relocate 12 households. By 2013, when the telescope is to be
in operation, all 61 farmers will move to their new houses in Kedu
town, with farmland allocated by the government.

“The project is beyond my imagination. I’m glad to see that an
ordinary old guy like me could contribute to the country’s science
program,” said Yang Chaoli, 68.

The project was approved by the National Development and Reform
Commission, the country’s top planning body, the Ministry of Science
and Technology, the Chinese Academy of Sciences and its subordinating
NAO, Guizhou Province and other departments.