The greatest triumphs of the Arecibo Observatory



Yesterday brought the tragic news that the famous 304.80m parable of the Arecibo Observatory in Puerto Rico will have to be demolished after two support cables have been broken. It’s the end of an era, but a good excuse to revisit some of the most important scientific contributions made possible by the famous structure.

Strategically built within a sinkhole, the Arecibo Observatory has been at the center of all sorts of scientific discoveries over the past 57 years. The radio parable has made an invaluable contribution to planetary and stellar science, the study of small-bodied objects such as asteroids, cosmology and even the search for extraterrestrial intelligence.

Here are some highlights from Arecibo’s illustrious career. RIP OFF.

A revised year on Mercury

NASA's Mariner 10 spacecraft captured this photo of Mercury in 1974. (Image: NASA / JLP) NASA’s Mariner 10 spacecraft captured this photo of Mercury in 1974. (Image: NASA / JLP)

Arecibo’s first major discovery occurred in 1967, when data collected by the radio telescope showed that a year on Mercury lasts 59 days, not 88 days as previously assumed.

Sending a message to the aliens

Visual demonstration of the message, with the addition of color to distinguish the various sections.  (Illustration: Wikimedia) Visual demonstration of the message, with the addition of color to distinguish the various sections. (Illustration: Wikimedia)

An interesting thing about the Arecibo Observatory is that, in addition to receiving radio signals, it can also transmit them. This capability was put to the test in 1974, when the structure transmitted a transmission, known as the Arecibo message, to the globular star cluster M13. This region of space is about 25,000 light-years away, so we’ll have to be patient for an answer.

Written in binary, the message was short and featured things like DNA, the human form, and even a digital representation of the Arecibo Observatory itself. In case you’re wondering, here’s what the broadcast looks like:

00000010101010000000000001010000010100000001001000100010001001011001010101010101010100100100000000000000000000000000000000000001100000000000000000001101000000000000000000011010000000000000000001010100000000000000000011111000000000000000000000000000000001100001110001100001100010000000000000110010000110100011000110000110101111101111101111101111100000000000000000000000000100000000000000000100000000000000000000000000001000000000000000001111110000000000000111110000000000000000000000011000011000011100011000100000001000000000100001101000011000111001101011111011111011111011111000000000000000000000000001000000110000000001000000000001100000000000000010000011000000000011111100000110000001111100000000001100000000000001000000001000000001000001000000110000000100000001100001100000010000000000110001000011000000000000000110011000000000000011000100001100000000011000011000000100000001000000100000000100000100000001100000000100010000000011000000001000100000000010000000100000100000001000000010000000100000000000011000000000110000000011000000000100011101011000000000001000000010000000000000010000011111000000000000100001011101001011011000000100111001001111111011100001110000011011100000000010100000111011001000000101000001111110010000001010000011000000100000110110000000000000000000000000000000000011100000100000000000000111010100010101010101001110000000001010101000000000000000010100000000000000111110000000000000000111111111000000000000111000000011100000000011000000000001100000001101000000000101100000110011000000011001100001000101000001010001000010001001000100100010000000010001010001000000000000100001000010000000000001000000000100000000000000100101000000000001111001111101001111000

You can find a full explanation of the Arecibo message here.

The first detection of Binary Pulsar

Artist's impression of a binary pulsar.  (Image: Jodrell Bank Observatory, University of Manchester / Wikimedia) Artist’s impression of a binary pulsar. (Image: Jodrell Bank Observatory, University of Manchester / Wikimedia)

Pulsars – rapidly rotating stars that emit beams of electromagnetic radiation from their highly magnetic poles – were first discovered in 1967. Researchers who used the Arecibo Observatory in 1974 did better by discovering the first binary pulsar. in which a pulsar orbits another star. The discovery earned Joseph Taylor and Russell Hulse the 1993 Nobel Prize in Physics.

The first radar maps of Venus

Radar map of Venus.  (Image: NAIC) Radar map of Venus. (Image: NAIC)

In 1981, Arecibo provided the first radar maps of Venus, a planet perpetually covered in clouds. The dish would have provided even more details of Venus in later years.

Identification of asteroids

Asteroid 2001 GQ2, as imaged by Arecibo in April 2001 (Image: NAIC) Asteroid 2001 GQ2, as imaged by Arecibo in April 2001 (Image: NAIC)

Arecibo identified its first asteroid in 1989, an object called 4769 Castalia. The observatory would go on to find many more and collect important data on potentially dangerous objects near Earth. One of the most deplorable aspects of the plate having to be closed is that Arecibo will no longer scour the skies for potential threats.

Finding the ice at the poles of Mercury

Arecibo radar image showing ice at the north pole of Mercury.  (Image: NAIC) Arecibo radar image showing ice at the north pole of Mercury. (Image: NAIC)

The planet closest to the Sun, Mercury, has ice at both the north and south poles, which we learned in 1992 from observations made by Arecibo. The deposits are presumably frozen water, evidence of volatile materials on the surface of Mercury. This ice “persists in shadowed craters despite the high temperatures, 800 ° F, on the surface,” according to the National Astronomy and Ionosphere Center, which is the official name of the Arecibo Observatory.

The first exoplanets ever discovered

Artist's impression of the first ever discovered exoplanet, which appears to be orbiting a pulsar.  (Illustration: NASA / JPL-Caltech) Artist’s impression of the first ever discovered exoplanet, which appears to be orbiting a pulsar. (Illustration: NASA / JPL-Caltech)

In 1992, astronomer Aleksander Wolszczan used the Arecibo telescope to locate three exoplanets around a pulsar named PSR B1257 + 12. These were the first planets ever discovered outside our solar system and a big step forward in ours. understanding of the cosmos.

Refine our understanding of gravitational waves

Artist's impression of gravitational waves generated by binary neutron stars.  (Image: R. Hurt / Caltech-JPL) Artist’s impression of gravitational waves generated by binary neutron stars. (Image: R. Hurt / Caltech-JPL)

Gravitational waves – ripples in the fabric of spacetime caused by tremendous events such as the collision of black holes or supernovae – were finally confirmed by scientists in 2016, after being predicted by Albert Einstein a century ago. This monumental discovery, made by the Laser Interferometer Gravitational-wave Observatory (LIGO), may not have been possible had it not been for Arecibo, as NAIC explains:

Indeed, the earliest evidence for the existence of gravitational waves came from Arecibo’s long-term observations of a pulsar in a decaying orbit with another neutron star, where the rate of orbital shrinkage corresponded to the rate expected from the loss of energy carried away by the gravitational force emitted. waves.

Repeated first fast radio burst

Artist's impression of a powerful burst of X-rays erupting from a magnetar, a known source of fast radio bursts.  (Image: NASA's Goddard Space Flight Center / Chris Smith (USRA) Artist’s impression of a powerful burst of X-rays erupting from a magnetar, a known source of fast radio bursts. (Image: NASA’s Goddard Space Flight Center / Chris Smith (USRA)

Scientists first detected fast radio bursts (FRBs) in 2007, but two main factors prevented them from fully understanding these enigmatic millisecond pulses. The first is that all of them (until recently) originated in galaxies far, far away. The second is that the FRBs were fleeting and one-off events. That changed in 2016 when scientists working at the Arecibo Observatory spotted the first repeat FRB. Since that time, we have detected other repeaters and even FRBs from our own galaxy. Recent evidence suggests that these pulses come from highly magnetic neutron stars known as magnetars.

The Curious Case of Vanish Pulsars

Artist's impression of a pulsar.  (Illustration: NASA) Artist’s impression of a pulsar. (Illustration: NASA)

In one of the most unexpected astronomical discoveries, scientists used the facility to detect two rather strange pulsars that stopped flashing for intermittent periods. The discovery, made in 2017, suggests that pulsars do not always blink and have an “active” and an “off” state. Furthermore, this research suggests that there may be more intermittent pulsars than “normal” pulsars.

Hunting for aliens

A view of the Milky Way.  (Image: NASA) A view of the Milky Way. (Image: NASA)

Despite these amazing discoveries, Arecibo is probably most famous for its use in SETI – the search for extraterrestrial intelligence. The observatory was used by groups such as [email protected], the SETI team of the University of California, Berkeley, and the SETI Institute’s Phoenix Project. The dish was also featured in the 1997 film Contact. No radio signal from aliens has ever been detected by Arecibo (nor by any other observatory, for that matter), which is, in itself, an interesting observation, which forces us to ask ourselves: where is everyone?


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