Connect with us

Gravitational waves are notoriously difficult to detect. Although modern optical astronomy has been around for centuries, gravitational wave astronomy has only been around since 2015. Even now our ability to detect gravitational waves is limited. Observatories such as LIGO and Virgo can only detect powerful events such as the mergers of stellar black holes or neutron stars. And they can only detect waves with a narrow range of frequencies from tens of Hertz to a few hundred Hertz. Many gravitational waves are produced at much lower frequencies, but right now we can’t observe them. Imagine raising a telescope to the night sky and only being able to see light that is a few shades of purple.

Naturally, astronomers would like to observe a wider range of gravitational “colors,” and several methods have been proposed. Space-based gravitational-wave telescopes such as the proposed LISA observatory should be able to detect millihertz waves, for example. There are also projects trying to detect extremely slow nanohertz gravitational waves such as NANOGrav which studies radio signals from fast-rotating pulsars. Both of these frequency ranges will have much to teach us about the universe.

But what’s missing is the ability to detect microhertz frequencies. These are gravitational waves that take several weeks to make a complete oscillation. It is a range that could prove crucial to our understanding of the big bang. According to the standard model of cosmology, in the early moments of the big bang, the universe experienced a brief moment of super-rapid expansion known as early cosmic inflation. The inflation theory is needed to solve several of the problems with the big bang, but we haven’t been able to prove it. Microhertz gravitational waves could be the solution. According to the theory, early cosmic inflation should have created microhertz gravitational waves across the cosmos. The universe should still be ringing with them, like the fading echo of a bell. Now a team of astronomers thinks they know how microhertz waves could be detected.

orbit 1
Gravitational waves could shift the Moon’s orbit. Credit: D. Blas and A. C. Jenkins

If there really are gravitational waves from early inflation, then everything is being jostled by them. Stars, asteroids, even the Earth and Moon. And therein lies the key. As these gravitational waves pass through the Earth-Moon system, they should shift the orbit of the Moon very slightly. This effect would be most dramatic at a frequency equal to the Moon’s orbital period, which is about 28 days. Right in the microhertz frequency range.

The catch is you’d need to be able to track the Moon’s position with extreme precision. But we can already do that. Thanks to the Apollo missions, we have reflectors placed on the Moon, and by shining lasers at them, we can measure the Moon’s position to within a centimeter. The team proposes making a series of measurements over time to specifically search for shifts from gravitational waves. They also propose a project similar to NANOGrav. Pulsars orbiting a companion with a period of several weeks would also be sensitive to microhertz gravitational waves, and measuring the signals from these binary pulsars might detect microhertz waves.

Right now it’s just an idea, but it’s a good one. And most of the tools we need already exist. Perhaps in the near future, a careful look at the Moon could allow us to solve one of the largest mysteries in cosmology.

Reference: Blas, Diego, and Alexander C. Jenkins. “Bridging the microHz Gap in the Gravitational-Wave Landscape with Binary Resonances.” Physical Review Letters 128.10 (2022): 101103.

The post Astronomers Could Detect Gravitational Waves by Tracking the Moon’s Orbit Around the Earth appeared first on Universe Today.

Did you miss our previous article…
https://www.mansbrand.com/lunar-rovers-could-be-dropped-into-lava-tubes-to-explore-their-depths/

Total
0
Shares
Share 0
Tweet 0
Pin it 0
Share 0
Related Topics:
Click to comment

You must be logged in to post a comment Login

Leave a Reply

Frontier Adventure

Not Getting Enough Data From Mars? Set Up A Solar System Pony Express

image

Getting data in from deep space can be difficult. Almost all of our missions that have flown into deep space use the Deep Space Network, a system of transmitters and receivers that already imposes constraints on the amount of data we can transfer from the far reaches of space. So a team led by Joshua Vander Hook, then at NASA’s Jet Propulsion Laboratory and now at a start-up called Outrider.ai, came up with a way to dramatically enhance the throughput of the DSN. In so doing, they gave it a very catchy name – the Solar System Pony Express.

Dr. Vander Hook was initially supported by a NASA Institute for Advanced Concepts (NIAC) grant in 2021. The basic concept utilizes what is known as a “cycler” orbit, where a spacecraft repeatedly orbits between two bodies in the solar system using their gravity wells to swing around in sync with when their orbits pass each other. 

In this case, the spacecraft would consist of a communications relay module that would collect high-throughput data from an observer module parked in orbit around the other body. The observer module would consistently download data from the missions operating in its local area and then, when a relay module gets close, would rapidly send all of that data to the cycling spacecraft. The cycler then returns to Earth, where another rapid download process begins, and the cycle repeats itself.

Fraser discusses some of the problems of communicating with deep space probes – especially those going to other stars.

That sounds like the Pony Express – a system in the 1800s whereby mail carriers would ride physical ponies (or horses) to deliver mail occasionally to remote outposts in the American West. In another homage to that mail carrier heritage, the team named the cycling relay satellites “data mules.”

Those data mules would have a long trip between Earth and their target destination. It might come as no surprise that in much of the literature surrounding the idea that the target destination was Mars. Buzz Aldrin, the most famous proponent of cycler orbits, suggested that cycler “castles” could effectively shuttle people and goods between Mars and Earth. But in this new configuration, instead of physical things, it would be more beneficial to ship data.

image 1
Another Depiction of how the observer / data mule interaction would go.
Credit – Marc Sanchez-Net et al.

Calculations described in a paper released last year estimate that with as little as six data mules, the network could provide a bandwidth of 1 petabyte a year from the surface of Mars while only requiring a minor allocation of time on the DSN. That would potentially allow some real-time high-definition video from the red planet, which would undoubtedly be attractive to many of the inhabitants of its nearest neighbor.

However, such high data rates come at a cost. In the case of the Solar System Pony Express, that cost is latency. The high throughput data transfer possible between the observer and a data mule, and then again from the data mule back to a receiving station on Earth, is only possible if they are in physical proximity to each other, as the network would use a type of high-throughput optical communications network. And since cycler orbits can take years, it would be years after the data was collected on the red planet that anyone could use it.

That is not a show stopper – indeed, many people would be okay with waiting for over a year for a high-definition video from Mars if that is the only way for them to see it. But it makes funding such a mission more difficult given the immediate feedback culture prevalent in many of today’s media. Give the authors credit, though – they recognize this limitation and, as all good scientists do, mention that it would be a good topic for further study.

For right now, that further study seems to be on hold. Dr. Vander Hook has moved on to other non-space-related efforts. While there has been some interest from researchers elsewhere, such as a paper from the University of Illinois, there’s currently no clear path forward for the project. But, there will always be a desire for more data transfer from farther out in the solar system. If the Pony Express is the most cost-effective way to get it at the beginning of our explorations, then don’t be surprised if this concept is resurrected sometime in the future.

Learn More:
Pascarella et al – Low-thrust trajectory optimization for the solar system pony
Did you miss our previous article…
https://mansbrand.com/a-protoplanetary-disc-has-been-found-in-another-galaxy/

Continue Reading

Frontier Adventure

A Protoplanetary Disc Has Been Found… in Another Galaxy!

eso1903a jpg

Astronomers have imaged dozens of protoplanetary discs around Milky Way stars, seeing them at all stages of formation. Now, one of these discs has been found for the first time — excitingly — in another galaxy. The discovery was made using the Atacama Large Millimeter/Submillimeter Array (ALMA) in Chile along with the , which detected the telltale signature of a spinning disc around a massive star in the Large Magellanic Cloud, located 160,000 light-years away.

“When I first saw evidence for a rotating structure in the ALMA data I could not believe that we had detected the first extragalactic accretion disc, it was a special moment,” said Anna McLeod, an associate professor at Durham University in the UK and lead author of the study published in Nature. “We know discs are vital to forming stars and planets in our galaxy, and here, for the first time, we’re seeing direct evidence for this in another galaxy.”

McLeod and her fellow researchers were doing a follow-up study on a system named HH 1177, which was located deep inside a gas cloud in the Large Magellanic Cloud LMC). In 2019, the researchers reported that in using the Very Large Telescope, they observed a jet emitted by a fledgling but massive star with a mass 12 times greater than our Sun. This was the first time such a jet has been observed in visible light outside the Milky Way, as they are usually obscured by their dusty surroundings. However, the relatively dust-free environment of the LMC allowed for HH 1177 to be observed at visible wavelengths. At nearly 33 light-years in length, it is one of the longest such jets ever observed.

eso1903a 1 jpg
This dazzling region of newly-forming stars in the Large Magellanic Cloud (LMC) was captured by the Multi Unit Spectroscopic Explorer instrument on ESO’s Very Large Telescope. The relatively small amount of dust in the LMC and MUSE’s acute vision allowed intricate details of the region to be picked out in visible light. Credit: ESO, A McLeod et al.

“We discovered a jet being launched from this young massive star, and its presence is a signpost for ongoing disc accretion,” McLeod said in an ESO press release. But to confirm that such a disc was indeed present, the team needed to measure the movement of the dense gas around the star.

The gas motion indicated that there is a radial flow of material falling onto a central disk-like structure. In their new observations, the team found that the disk exhibits signs of Keplerian rotation – which is a disk of material that obey’s Kepler’s laws of motion due to the dominance of a massive body at its center. Their observations revealed that “the rotating toroid [was] feeding an accretion disk and thus the growth of the central star,” the McLeod and team wrote in their paper. “The system is in almost all aspects comparable to Milky Way high-mass YSOs (young stellar objects) accreting gas from a Keplerian disk.

As matter is pulled towards a growing star, it cannot fall directly onto it; instead, it flattens into a spinning disc around the star. Closer to the center, the disc rotates faster, and this difference in speed is the clear evidence to show astronomers an accretion disc is present.

“The frequency of light changes depending on how fast the gas emitting the light is moving towards or away from us,” said Jonathan Henshaw, a research fellow at Liverpool John Moores University in the UK, and co-author of the study, in the ESO press release. “This is precisely the same phenomenon that occurs when the pitch of an ambulance siren changes as it passes you and the frequency of the sound goes from higher to lower.”

Massive stars like HH 1177 live fast and die hard. In the Milky Way, stars like this are challenging to observe because they are often clouded from view by the dusty material from which they form — which also obscures the disc that might be shaping around them.

“They form in heavily embedded regions full of gas and dust, such that the accretion phase typically occurs before the star has time to become exposed due to stellar feedback, whether internal or external,” the team wrote in their paper. “The primary reason for the lack of observations of extragalactic accretion disks around forming stars has been the limited spatial resolution of both ground- and space-based observatories.”

But the Large Magellanic Cloud is fundamentally different from because the stars that form there have a lower dust content than in the Milky
Did you miss our previous article…
https://mansbrand.com/a-gamma-ray-burst-disturbed-the-earths-ionosphere/

Continue Reading

Frontier Adventure

A Gamma-ray Burst Disturbed the Earth’s Ionosphere

Gamma ray burst illustration article 580x326 1 jpg

You’d think that something happening billions of light-years away wouldn’t affect Earth, right? Well, in 2002, a burst of gamma rays lasting 800 seconds actually impacted our planet. They came from a powerful and very distant supernova explosion. Its gamma-ray bombardment disturbed our planet’s ionosphere and activated lightning detectors in India.

This particular gamma-ray burst (GRB) occurred in a galaxy almost 2 billion light-years away (and took two billion years to reach us). Not only did ground-based detectors record the bombardment, but satellites sensitive to high-energy outbursts “saw” it, too. That included the European Space Agency’s International Gamma-Ray Astrophysics Laboratory (INTEGRAL) mission. It typically records gamma-ray bursts on a daily basis, but this one—named GRB 221009A—outshone all the rest.

GRBs this strong happen (on average) about once every 10,000 years, so this was one that caught everyone’s attention. “It was probably the brightest gamma-ray burst we have ever detected,” says Mirko Piersanti, University of L’Aquila, Italy, and lead author of a paper analyzing the event.

How The Gamma-ray Burst Affected the Ionosphere

Most of the time, radiation from the Sun bombards our planet. That’s often strong enough to affect the ionosphere. That’s an atmospheric layer that bristles with electrically charged gases called plasma. It stretches from around 50 km to 950 km in altitude above the surface. There’s a “top-side ionosphere” (which lies above 350 km) and a “bottom-side ionosphere”) which lies below that. Scientists are pretty familiar with how the Sun treats this region of the atmosphere, particularly during periods of heavy solar activity.

GRB 221009A: looking back through time at a gamma-ray-burst. Courtesy ESA
GRB 221009A: looking back through time at a gamma-ray-burst. Courtesy ESA

This GRB blast triggered instruments generally reserved for studying the immense explosions in the Sun’s atmosphere known as solar flares. “Notably, this disturbance impacted the very lowest layers of Earth’s ionosphere, situated just tens of kilometers above our planet’s surface, leaving an imprint comparable to that of a major solar flare,” says Laura Hayes, research fellow and solar physicist at ESA. That imprint basically was an increase in ionization in the bottom-side ionosphere. It left an imprint in low-frequency radio signals that move between Earth’s surface and the lowest levels of the ionosphere. “Essentially, we can say that the ionosphere ‘moved’ down to lower altitudes, and we detected this in how the radio waves bounce along the ionosphere,” explained Laura.

Gamma Ray Bursts in the Data

Past GRBs bothered the bottom-side ionosphere but didn’t always disturb the topside. Scientists just assumed that by the time it reached Earth, the blast from a GRB didn’t have the “oomph” to change that part of the ionosphere. GRB 221009A proved that idea wrong. Thanks to data from the orbiting China Seismo-Electromagnetic Satellite (CSES), scientists saw a strong disturbance in the upper ionosphere. It created a strong electric field variation and was the first time scientists saw this connected to a GRB. The result is the first-ever top-side ionospheric measurement of electric field variations triggered by a gamma-ray outburst at cosmic distances.

INTEGRAL and other spacecraft continually record GRBs from around the Universe. Have they all affected our ionosphere in some way? Is there a way to find out? Now that scientists know what ionospheric effects to look for, they can search the data to find answers. Data from INTEGRAL, and CSES will be particularly useful. They should be able to correlate it with other GRBs seen since 2018. That’s when CSES was launched.

Evidence of ionospheric disturbances from GRBs goes back as far as 1988. That’s when the effects of a 1983 gamma-ray burst were first reported. Scientists now have an array of ground-based and space-based detectors—such as Swift, Fermi, MAXI, AGILE, INTEGRAL, and CSES—gave strong detections of the emissions from GRB221009A.

Implications for Future GRB Effects on Earth

This kind of disturbance
Did you miss our previous article…
https://mansbrand.com/should-we-send-humans-to-venus/

Continue Reading

Trending