Astronomers may be getting closer to discovering as-yet hidden cosmic secrets, such as the nature of dark matter and the presence of widespread distortions in space-time, researchers reported at the 237th American Astronomical Society meeting, held virtually this week.
The existence of dark matter, an the invisible substance thought to make up more than four-fifths of all matter in the universe, may help explain a variety of cosmic puzzles, such as how galaxies can spin as fast as they do without getting ripped apart. However, much about the nature of dark matter — and even whether it exists at all — remains unknown.
To help pinpoint dark matter’s properties, researchers sought to directly measure the gravitational effects that dark matter should have on the speed at which stars are moving in the Milky Way. They focused on galactic lighthouses known as pulsars, or spinning neutron stars that emit twin beams of radio waves from their magnetic poles as they rotate. (Neutron stars are the remains of large stars that perished in catastrophic explosions known as supernovas.)
“It is a very, very small number we are trying to measure,” study lead author Sukanya Chakrabarti, an astrophysicist at the Rochester Institute of Technology in New York, said during a news conference held on Monday (Jan. 11). “In terms of change in velocity, it’s just a few centimeters per second, or roughly the speed of a crawling baby, and not a very fast baby at that.”
Pulsars spin at very steady rates, so they can serve as precise clocks. By monitoring tiny variations in the spin of 14 pulsars, the researchers could estimate the speeds at which these pulsars are moving and thus deduce the gravitational force that dark matter is exerting on them.
The scientists found that across the galaxy, the average amount of dark matter may be slightly lower than previous estimates. The researchers also calculated the amount of dark matter contained within the volume of the Earth is just 1.63 lbs. (740 grams), Chakrabarti said. These findings in turn can help current experiments seeking to directly detect dark matter “try and understand the nature of dark matter particles,” she added. For instance, this might affect how often one might expect such particles to interact with detectors.
In addition, scientists are now analyzing an unusually high number of gamma rays from the center of the Milky Way to see if they might come from annihilating dark matter particles. Previous research suggested dark matter could be made of new kinds of particle, ones that annihilate when they come in contact with each other, generating high-energy gamma rays.
Based on 11 years of data from NASA’s Fermi Gamma-Ray Space Telescope, “we can say what are good candidates for dark matter,” study lead author Mattia di Mauro, an astrophysicist at the National Institute for Nuclear Physics in Torino, Italy, said during the same news conference. These include weakly interacting massive particles, or WIMPS, hypothetical elementary particles that only barely interact with ordinary matter except through their gravitational pull.
“In the future, the Large Hadron Collider or other particle physics detectors could test these specific candidates,” he added.
The gravitational background
Researchers at the premiere astronomy conference also reported finding the first possible hints of a mysterious new kind of gravitational wave, cosmic ripples that warp the fabric of space and time itself.
Scientists reported the first-ever direct detection of gravitational waves in 2016 using the Laser Interferometer Gravitational-Wave Observatory (LIGO), a discovery that earned the 2017 Nobel Prize in Physics. The space-time distortions those researchers saw were created when two black holes collided with each other about 130 million light-years from Earth. Since then, LIGO has observed dozens more such signals.
But the gravitational waves that LIGO are best at detecting are the most powerful ones, loud outbursts released when extraordinarily massive objects collide with one another. Researchers now also want to detect gravitational waves that are more like the background noise of small talk at a crowded party.
In theory, merging galaxies and other cosmic events should generate such a “gravitational wave background.” Detecting this steady hum could shed light on mysteries such as how galaxies have grown over time.
However, these waves are huge, posing a major challenge for detecting this gravitational wave background. Whereas existing gravitational-wave observatories on Earth are designed to search for gravitational waves on the order of seconds long, ripples from the gravitational wave background are years or even decades long.
Now researchers say they may have detected a strong signal of the gravitational wave background using a U.S. and Canadian project called the North American Nanohertz Observatory for Gravitational Waves (NANOGrav).
“We’re seeing incredibly significant evidence for this signal,” study lead author Joseph Simon, an astrophysicist at the University of Colorado Boulder, said during the AAS press conference. “Unfortunately, we can’t quite say what it is yet.”
NANOGrav uses telescopes on the ground to monitor dozens of pulsars. Gravitational waves can alter the steady blinking pattern of light from pulsars, squeezing and expanding the distances these rays travel through space.
“As these waves pass us, the Earth gets pushed around very slightly,” Simon said. “As Earth is pushed closer to pulsars in one part of the sky, those pulsars’ pulses will appear a little bit sooner than expected, and pulses from pulsars in the other part of the sky appear to come a bit later.”
Analyzing this pulsar light could therefore help scientists detect signs of the gravitational wave background.
“By monitoring signals from a large number of these pulsars, we created a galaxy-size gravitational-wave detector within our own Milky Way,” Simon said.
To find these subtle hints, NANOGrav scientists have attempted to observe as many pulsars as they can for as long as possible. So far, they have observed 45 pulsars for at least three years, and in some cases, for more than a dozen years.
“These pulsars are spinning about as fast as your kitchen blender,” Simon said in a statement. “And we’re looking at deviations in their timing of just a few hundred nanoseconds.”
Now the researchers said they have detected potential evidence of a common process distorting the light from many of the pulsars. As of yet, they cannot verify whether this signal is evidence for the gravitational wave background, “but we also don’t have evidence against it,” Simon said.
The scientists caution they still need to look at more pulsars and monitor them for longer time periods to confirm whether the gravitational background is the cause.
If the researchers can verify they have detected the gravitational wave background, they next want to pinpoint what causes these waves and what such signals can tell scientists about the universe.
The scientists detailed their findings Jan. 11 at an online meeting of the American Astronomical Society. Chakrabarti and her colleagues detailed their findings in a study accepted in the journal Astrophysical Journal Letters. Simon and his colleagues detailed their NANOGrav findings online Dec. 24 in the journal The Astrophysical Journal Letters.
TEL AVIV, Israel (AP) — A rare Bronze-Era jar accidentally smashed by a 4-year-old visiting a museum was back on display Wednesday after restoration experts were able to carefully piece the artifact back together.
Last month, a family from northern Israel was visiting the museum when their youngest son tipped over the jar, which smashed into pieces.
Alex Geller, the boy’s father, said his son — the youngest of three — is exceptionally curious, and that the moment he heard the crash, “please let that not be my child” was the first thought that raced through his head.
The jar has been on display at the Hecht Museum in Haifa for 35 years. It was one of the only containers of its size and from that period still complete when it was discovered.
The Bronze Age jar is one of many artifacts exhibited out in the open, part of the Hecht Museum’s vision of letting visitors explore history without glass barriers, said Inbal Rivlin, the director of the museum, which is associated with Haifa University in northern Israel.
It was likely used to hold wine or oil, and dates back to between 2200 and 1500 B.C.
Rivlin and the museum decided to turn the moment, which captured international attention, into a teaching moment, inviting the Geller family back for a special visit and hands-on activity to illustrate the restoration process.
Rivlin added that the incident provided a welcome distraction from the ongoing war in Gaza. “Well, he’s just a kid. So I think that somehow it touches the heart of the people in Israel and around the world,“ said Rivlin.
Roee Shafir, a restoration expert at the museum, said the repairs would be fairly simple, as the pieces were from a single, complete jar. Archaeologists often face the more daunting task of sifting through piles of shards from multiple objects and trying to piece them together.
Experts used 3D technology, hi-resolution videos, and special glue to painstakingly reconstruct the large jar.
Less than two weeks after it broke, the jar went back on display at the museum. The gluing process left small hairline cracks, and a few pieces are missing, but the jar’s impressive size remains.
The only noticeable difference in the exhibit was a new sign reading “please don’t touch.”
VICTORIA – The British Columbia government is partnering with a bear welfare group to reduce the number of bears being euthanized in the province.
Nicholas Scapillati, executive director of Grizzly Bear Foundation, said Monday that it comes after months-long discussions with the province on how to protect bears, with the goal to give the animals a “better and second chance at life in the wild.”
Scapillati said what’s exciting about the project is that the government is open to working with outside experts and the public.
“So, they’ll be working through Indigenous knowledge and scientific understanding, bringing in the latest techniques and training expertise from leading experts,” he said in an interview.
B.C. government data show conservation officers destroyed 603 black bears and 23 grizzly bears in 2023, while 154 black bears were killed by officers in the first six months of this year.
Scapillati said the group will publish a report with recommendations by next spring, while an independent oversight committee will be set up to review all bear encounters with conservation officers to provide advice to the government.
Environment Minister George Heyman said in a statement that they are looking for new ways to ensure conservation officers “have the trust of the communities they serve,” and the panel will make recommendations to enhance officer training and improve policies.
Lesley Fox, with the wildlife protection group The Fur-Bearers, said they’ve been calling for such a committee for decades.
“This move demonstrates the government is listening,” said Fox. “I suspect, because of the impending election, their listening skills are potentially a little sharper than they normally are.”
Fox said the partnership came from “a place of long frustration” as provincial conservation officers kill more than 500 black bears every year on average, and the public is “no longer tolerating this kind of approach.”
“I think that the conservation officer service and the B.C. government are aware they need to change, and certainly the public has been asking for it,” said Fox.
Fox said there’s a lot of optimism about the new partnership, but, as with any government, there will likely be a lot of red tape to get through.
“I think speed is going to be important, whether or not the committee has the ability to make change and make change relatively quickly without having to study an issue to death, ” said Fox.
This report by The Canadian Press was first published Sept. 9, 2024.
The European Space Agency is fast-tracking a new mission called Ramses, which will fly to near-Earth asteroid 99942 Apophis and join the space rock in 2029 when it comes very close to our planet — closer even than the region where geosynchronous satellites sit.
Ramses is short for Rapid Apophis Mission for Space Safety and, as its name suggests, is the next phase in humanity’s efforts to learn more about near-Earth asteroids (NEOs) and how we might deflect them should one ever be discovered on a collision course with planet Earth.
In order to launch in time to rendezvous with Apophis in February 2029, scientists at the European Space Agency have been given permission to start planning Ramses even before the multinational space agency officially adopts the mission. The sanctioning and appropriation of funding for the Ramses mission will hopefully take place at ESA’s Ministerial Council meeting (involving representatives from each of ESA’s member states) in November of 2025. To arrive at Apophis in February 2029, launch would have to take place in April 2028, the agency says.
This is a big deal because large asteroids don’t come this close to Earth very often. It is thus scientifically precious that, on April 13, 2029, Apophis will pass within 19,794 miles (31,860 kilometers) of Earth. For comparison, geosynchronous orbit is 22,236 miles (35,786 km) above Earth’s surface. Such close fly-bys by asteroids hundreds of meters across (Apophis is about 1,230 feet, or 375 meters, across) only occur on average once every 5,000 to 10,000 years. Miss this one, and we’ve got a long time to wait for the next.
When Apophis was discovered in 2004, it was for a short time the most dangerous asteroid known, being classified as having the potential to impact with Earth possibly in 2029, 2036, or 2068. Should an asteroid of its size strike Earth, it could gouge out a crater several kilometers across and devastate a country with shock waves, flash heating and earth tremors. If it crashed down in the ocean, it could send a towering tsunami to devastate coastlines in multiple countries.
Over time, as our knowledge of Apophis’ orbit became more refined, however, the risk of impact greatly went down. Radar observations of the asteroid in March of 2021 reduced the uncertainty in Apophis’ orbit from hundreds of kilometers to just a few kilometers, finally removing any lingering worries about an impact — at least for the next 100 years. (Beyond 100 years, asteroid orbits can become too unpredictable to plot with any accuracy, but there’s currently no suggestion that an impact will occur after 100 years.) So, Earth is expected to be perfectly safe in 2029 when Apophis comes through. Still, scientists want to see how Apophis responds by coming so close to Earth and entering our planet’s gravitational field.
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“There is still so much we have yet to learn about asteroids but, until now, we have had to travel deep into the solar system to study them and perform experiments ourselves to interact with their surface,” said Patrick Michel, who is the Director of Research at CNRS at Observatoire de la Côte d’Azur in Nice, France, in a statement. “Nature is bringing one to us and conducting the experiment itself. All we need to do is watch as Apophis is stretched and squeezed by strong tidal forces that may trigger landslides and other disturbances and reveal new material from beneath the surface.”
The Goldstone radar’s imagery of asteroid 99942 Apophis as it made its closest approach to Earth, in March 2021. (Image credit: NASA/JPL–Caltech/NSF/AUI/GBO)
By arriving at Apophis before the asteroid’s close encounter with Earth, and sticking with it throughout the flyby and beyond, Ramses will be in prime position to conduct before-and-after surveys to see how Apophis reacts to Earth. By looking for disturbances Earth’s gravitational tidal forces trigger on the asteroid’s surface, Ramses will be able to learn about Apophis’ internal structure, density, porosity and composition, all of which are characteristics that we would need to first understand before considering how best to deflect a similar asteroid were one ever found to be on a collision course with our world.
Besides assisting in protecting Earth, learning about Apophis will give scientists further insights into how similar asteroids formed in the early solar system, and, in the process, how planets (including Earth) formed out of the same material.
One way we already know Earth will affect Apophis is by changing its orbit. Currently, Apophis is categorized as an Aten-type asteroid, which is what we call the class of near-Earth objects that have a shorter orbit around the sun than Earth does. Apophis currently gets as far as 0.92 astronomical units (137.6 million km, or 85.5 million miles) from the sun. However, our planet will give Apophis a gravitational nudge that will enlarge its orbit to 1.1 astronomical units (164.6 million km, or 102 million miles), such that its orbital period becomes longer than Earth’s.
It will then be classed as an Apollo-type asteroid.
Ramses won’t be alone in tracking Apophis. NASA has repurposed their OSIRIS-REx mission, which returned a sample from another near-Earth asteroid, 101955 Bennu, in 2023. However, the spacecraft, renamed OSIRIS-APEX (Apophis Explorer), won’t arrive at the asteroid until April 23, 2029, ten days after the close encounter with Earth. OSIRIS-APEX will initially perform a flyby of Apophis at a distance of about 2,500 miles (4,000 km) from the object, then return in June that year to settle into orbit around Apophis for an 18-month mission.
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Furthermore, the European Space Agency still plans on launching its Hera spacecraft in October 2024 to follow-up on the DART mission to the double asteroid Didymos and Dimorphos. DART impacted the latter in a test of kinetic impactor capabilities for potentially changing a hazardous asteroid’s orbit around our planet. Hera will survey the binary asteroid system and observe the crater made by DART’s sacrifice to gain a better understanding of Dimorphos’ structure and composition post-impact, so that we can place the results in context.
The more near-Earth asteroids like Dimorphos and Apophis that we study, the greater that context becomes. Perhaps, one day, the understanding that we have gained from these missions will indeed save our planet.
