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More than a hundred years have passed since Einstein formalized his theory of General Relativity (GR), the geometric theory of gravitation that revolutionized our understanding of the Universe. And yet, astronomers are still subjecting it to rigorous tests, hoping to find deviations from this established theory. The reason is simple: any indication of physics beyond GR would open new windows onto the Universe and help resolve some of the deepest mysteries about the cosmos.

One of the most rigorous tests ever was recently conducted by an international team of astronomers led by Michael Kramer of the Max Planck Institute for Radio Astronomy (MPIfR) in Bonn, Germany. Using seven radio telescopes from across the world, Kramer and his colleagues observed a unique pair of pulsars for 16 years. In the process, they observed effects predicted by GR for the first time, and with an accuracy of at least 99.99%!

In addition to researchers from the MPIfR, Kramer and his associates were joined by researchers from institutions in ten different countries – including the Jodrell Bank Centre for Astrophysics (UK), the ARC Centre of Excellence for Gravitational Wave Discovery (Australia), the Perimeter Institute for Theoretical Physics (Canada), the Observatoire de Paris (France), the Osservatorio Astronomico di Cagliari (Italy), the South African Radio Astronomy Observatory (SARAO), the Netherlands Institute for Radio Astronomy (ASTRON), and the Arecibo Observatory.

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Pulsars are fast-spinning neutron stars that emit narrow, sweeping beams of radio waves. A new study identifies the origin of those radio waves. NASA’s Goddard Space Flight Center

“Radio pulsars” are a special class of rapidly rotating, highly magnetized neutron stars. These super-dense objects emit powerful radio beams from their poles that (when combined with their rapid rotation) create a strobing effect that resembles a lighthouse. Astronomers are fascinated by pulsars because they provide a wealth of information on the physics governing ultra-compact objects, magnetic fields, the interstellar medium (ISM), planetary physics, and even cosmology.

In addition, the extreme gravitational forces involved allow astronomers to test predictions made by gravitational theories like GR and Modified Newtonian Dynamics (MOND) under some of the most extreme conditions imaginable. For the sake of their study, Kramer and his team examined PSR J0737-3039 A/B, the “Double Pulsar” system located 2,400 light-years from Earth in the constellation Puppis.

This system is the only radio pulsar binary ever observed and was discovered in 2003 by members of the research team. The two pulsars that make up this system have rapid rotations – 44 times a second (A), once every 2.8 seconds (B) – and orbit each other with a period of just 147 minutes. While they are about 30% more massive than the Sun, they measure only about 24 km (15 mi) in diameter. Hence, their extreme gravitational pull and intense magnetic fields.

In addition to these properties, the rapid orbital period of this system makes it a near-perfect laboratory for testing theories of gravitation. As Prof. Kramer said in a recent MPIfR press release:

“We studied a system of compact stars that is an unrivalled laboratory to test gravity theories in the presence of very strong gravitational fields. To our delight we were able to test a cornerstone of Einstein’s theory, the energy carried by gravitational waves, with a precision that is 25 times better than with the Nobel-Prize winning Hulse-Taylor pulsar, and 1000 times better than currently possible with gravitational wave detectors.”

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Frontier Adventure

Jupiter’s “Stripes” Change Color. Now We Might Know Why

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June 4, 2023

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While Jupiter’s Great Red Spot is one of the most well-known spectacles in the solar system, Jupiter’s clouds and stripes that are responsible for the planet’s weather patterns are highly regarded, as well. Though not nearly as visible in an amateur astronomy telescope, Jupiter’s multicolored, rotating, and swirling cloud stripes are a sight to behold for any astronomy fan when seen in up-close images. And, what makes these stripes unique is they have been observed to change color from time to time, but the question of what causes this color change to occur has remained elusive.

This is what a recent study published in Nature Astronomy hopes to address as an international team of researchers examine how Jupiter’s massive magnetic field could be responsible for Jupiter’s changing stripe colors. This study was led by Dr. Kumiko Hori of Kobe University and Dr. Chris Jones of the University of Leeds and holds the potential to help scientists better understand how a planet’s magnetic field could influence a planet’s weather patterns. In this case, Jupiter’s massive magnetic field influencing its massive, swirling clouds.

“If you look at Jupiter through a telescope, you see the stripes, which go round the equator along lines of latitude,” explains Dr. Jones. “There are dark and light belts that occur, and if you look a little bit more closely, you can see clouds zipping around carried by extraordinarily strong easterly and westerly winds. Near the equator, the wind blows eastward but as you change latitude a bit, either north or south, it goes westward. And then if you move a little bit further away it goes eastward again. This alternating pattern of eastward and westward winds is quite different from weather on Earth.”

While previous studies have demonstrated that Jupiter’s appearance is somehow altered by infrared fluctuations approximately 50 km (31 mi) below the gas cloud surface, this most recent study demonstrates the infrared fluctuations could be caused by Jupiter’s magnetic field, the source of which, like Earth, is far deeper inside the planet.

“Every four or five years, things change,” said Dr. Jones. “The colors of the belts can change and sometimes you see global upheavals when the whole weather pattern goes slightly crazy for a bit, and it has been a mystery as to why that happens.”

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Infrared images of Jupiter obtained by a ground-based telescope displaying changes in the color of Jupiter’s clouds between 2001 and 2011 (dashed blue lines). (Credit: Arrate Antuñano/NASA/IRTF/NSFCam/SpeX)

For the study, the researchers analyzed data collected over several years from NASA’s Juno spacecraft to both observe and measure variations in Jupiter’s magnetic field, more commonly known as oscillations. Despite Jupiter’s massive radiation belt which can cause immense harm to any spacecraft, Juno has been orbiting the solar system’s largest planet since 2016 and is frequently lauded for it still being active despite the constant bombardment from the radiation.

From the data, the team was able to monitor the magnetic field’s waves and oscillations. They focused on a specific area of the magnetic field dubbed the Great Blue Spot, which is invisible to the naked eye and located near Jupiter’s equator. While this spot has been observed to be traveling eastwards on Jupiter, the data from this study indicates the spot is slowing down, which the team interprets as the start of an oscillation within the magnetic field, meaning the spot could eventually slow enough to where it reverses direction and starts traveling westwards.

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Still image taken from a video animation featuring Jupiter’s massive magnetic field at one instant in time, specifically its Great Blue Spot located near
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CRS-28 Mission

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June 3, 2023

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SpaceX is targeting Saturday, June 3 for Falcon 9’s launch of Dragon’s 28th Commercial Resupply Services (CRS-28) mission to the International Space Station from Launch Complex 39A (LC-39A) at NASA’s Kennedy Space Center in Florida. The instantaneous launch window is at 12:35 p.m. ET (16:35 UTC) and a backup launch opportunity is available on Sunday, June 4 at 12:12 p.m. ET (16:12 UTC).

This is the fifth flight of the first stage booster supporting this mission, which previously launched Crew-5, GPS III Space Vehicle 06, Inmarsat I-6 F2, and one Starlink mission. Following stage separation, Falcon 9 will land on the A Shortfall of Gravitas droneship in the Atlantic Ocean.

CRS-28 is the fourth flight for this Dragon spacecraft, which previously flew CRS-21, CRS-23, and CRS-25 to the space station. After an approximate 41-hour flight, Dragon will autonomously dock with the orbiting laboratory on Monday, June 5 at approximately 5:38 a.m. ET (9:38 UTC).

A live webcast of this mission will begin about 20 minutes prior to liftoff.

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You Can Detect Tsunamis as They Push the Atmosphere Around

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3 days ago

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June 2, 2023

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Anyone who’s ever lived along a coastline or been at sea knows the effects of tsunamis. And, they appreciate all the early warning they can get if one’s on the way. Now, NASA’s GNSS Upper Atmospheric Real-time Disaster and Alert Network (GUARDIAN) is using global navigation systems to measure the effect these ocean disturbances have on our atmosphere. The system’s measurements could provide a very effective early warning tool for people to get to higher ground in the path of a tsunami.

Earthquakes and undersea volcanic eruptions often trigger tsunamis. Essentially, those tectonic events displace huge amounts of ocean water. During the resulting tsunami, huge areas of the ocean’s surface rise and fall. As they do, the ocean movement displaces the overlying column of air. That sets off ripples in the atmosphere. Think of it as if the air is responding by creating its own tsunami. It actually does that in response to fast-moving storms and their squall lines. Meteorologists call those reactions “meteotsunamis.” They can push water around into dangerous waves, which then cause flooding and other damage. That’s very similar to tsunamis generated by earthquakes.

What NASA’s Doing to Predict Tsunamis

Weather forecasters can generally predict bad weather leading to meteotsunamis, but that’s not the case for earthquakes and underwater volcanoes and the tsunamis they trigger. So, the NASA project aims to provide advance notice after a temblor or a volcanic eruption.

The GUARDIAN system taps into a constant data stream emitted by clusters of global positioning satellites and other wayfinding stations orbiting Earth. They give real-time information about changes in water heights in the ocean and surface measurements of land masses. Those data-rich radio signals get collected by ground stations and sent to NASA Jet Propulsion Laboratory. There, it gets analyzed by the Global Differential network, which constantly improves the real-time positional accuracy of features on the planet.

So, when a tectonic event happens, the system is alerted to look for changes in the air masses over the oceans. Displaced ripples in the air move out in all directions as low-frequency sound and gravity waves. Those vibrations rush to the top of the atmosphere within just a few minutes. There, they crash into the charged particles of the ionosphere. That distorts signals from the GPS satellites, and those distorted signals tell the system that something’s going on down below.

This animation shows how waves of energy from the Tohoku-Oki earthquake and tsunami of March 11, 2011, pierced Earth’s ionosphere in the vicinity of Japan, disturbing the density of electrons. These disturbances were monitored by tracking GPS signals between satellites and ground receivers.
Credits: NASA/JPL-Caltech

Normally navigational systems would correct for the distorted signals because they aren’t useful to their users, according to Léo Martire, who works on the GUARDIAN project. “Instead of correcting for this as an error, we use it as data to find natural hazards,” he said.

Early Warning is the Key

The most active tectonic region on our planet is the area known as the Ring of Fire. It’s basically a large ring of volcanically and tectonically active regions in the Pacific Ocean basin. About 78 percent of tsunamis between 1900 and 2015 occurred there.

Most of us remember the tsunami that hit Japan after a magnitude 9.0 earthquake hit just off the coast in 2011. That event devastated 70 kilometers of coastline, destroyed towns and villages, killed hundreds of people, and shut down the Fukushima nuclear power plant.

Damaged village in Japan in the wake of the tsunami onf 2011. Photo: Katherine Mueller, IFRC
Damaged village in Japan in the wake of the tsunami onf 2011. Photo: Katherine Mueller, IFRC

One of the most damaging tsunamis occurred on the Big Island of Hawai’i on April 1st, 1946. An earthquake off the Aleutian Islands triggered the tsunami that crushed a small village in Alaska and struck California. It also reached out and touched the Hawaiian coast near Hilo. 50-foot waves crashed into the island, taking out buildings, and
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