The U.S. military plans to launch satellites to learn more about how radio signals behave in part of the Earth's atmosphere.

The Defense Advanced Research Projects Agency (DARPA) has set up a new program, called Ouija, which will use sensors on "low-orbiting satellites" to track high-frequency radio waves in the ionosphere. DARPA has a solicitation for proposals available now for one part of the proposal and plans to release a second solicitation at another date.

The ionosphere is best known as the atmospheric zone where auroras roam, depending upon solar activity and the Earth's magnetic field. The Ouija program will focus on a region of the ionosphere roughly 125 miles to 185 miles (300 to 400 kilometers) in altitude — well below the orbit of the International Space Station, which zooms around our planet at an average height of 250 miles (400 km).

Characterizing how radio waves behave in this space will be crucial to help future warfighters work effectively, DARPA officials said in an April 22 statement. Signal propagation in the ionosphere is notoriously unpredictable, due to the high density of charged particles (mainly electrons) that can alter the path of radio signals.

The solar system's current planetary orbits seem stable, but that's only because the planets have settled into them over billions of years. The early solar system was a much different place than that seen today, and for almost 20 years, scientists thought they had a good handle on how it got that way. But more recently, data had started pointing to some flaws in that understanding - especially about how the giant planets in the outer solar system got where they are today. Now an international team of astrophysicists thinks they have a better understanding of that process, and they believe it could help solve a long-standing argument about the early solar system.

Currently, the best model scientists have for the formation of the solar system is known as the Nice model, after the town in France, where it was first developed in 2005. As part of this model, the gas giants that currently reside in the outer fringes of this solar system originally orbited what became the sun much more closely with more circular orbits. However, something caused instability in the system that kicked those planets out into the much more unevenly spaced and oblong orbits we see them in today.

What exactly caused that anomaly has thus far been a mystery. However, a team comprised of researchers from Michigan State University, Zhejiang University, and the University of Bordeaux think they have an answer. It's as simple as dust in the (solar) wind.

CBET 5112 & MPEC 2022-G82, issued on 2022, April 06, announce the discovery of a comet (magnitude ~18.5) on CCD images taken on Mar. 30.3 UT with a 0.5-m f/2 Wright-Schmidt reflector at Rio Hurtado, Chile, in the course of the "Asteroid Terrestrial-Impact Last Alert System" (ATLAS) search program. The new comet has been designated C/2022 F1 (ATLAS).

Stacking of 20 unfiltered exposures, 90 seconds each, obtained remotely on 2022, April 2.4 from X02 (Telescope Live, Chile) through a 0.61-m f/6.5 astrograph + CCD, shows that this object is a comet with a compact coma about 9" arcsecond in diameter (Observers E. Bryssinck, M. Rocchetto, E. Guido, M. Fulle, G. Milani, G. Savini, A. Valvasori).

Our confirmation image (click on the images for a bigger version)

An international group of astronomers has uncovered new clues about a mysterious stellar explosion that was discovered eight years ago, but is continuing to evolve even as scientists watch.

The results help astronomers better understand the process of how massive stars — giants far larger than our own sun — live and die.

The study was published in The Astrophysical Journal by a group led by the University of Texas at Austin and including scientists with the University of Chicago.

The lives of 2014C

In 2014, astronomers saw a sudden bright spot in the sky — a sure sign that a star had exploded out in space.

When an exploding star is first detected, astronomers around the world begin to follow it with telescopes as the light it gives off changes rapidly over time. By watching how it evolves, using telescopes that can see visible light and also X-rays, radio waves, and infrared light, scientists can deduce the physical characteristics of the system.

By doing this many times, scientists have grouped these exploding stars into categories. 2014C, as this particular event was named, looked like what's called a Type Ib supernova. They are what happen when the largest known stars in the universe die.

Oxford researchers are reportedly concerned that the US agency's effort to communicate with extraterrestrials could be dangerous.

Scientists at the UK's Oxford University have reportedly sounded an alarm over plans by NASA to broadcast location data and other information into space, warning that the effort could have dangerous unintended consequences, including triggering an alien invasion.

At issue is the planned "Beacon in the Galaxy" (BITG), a broadcast of data by a NASA-led team of researchers with the aim of greeting "extraterrestrial intelligences." The US space agency wants to beam the signal from the SETI Institute's Allen Telescope array in California and China's Five-hundred-meter Aperture Spherical Radio Telescope (FAST). It would include such information as the biochemical composition of life on Earth, the Solar System's time-stamped position in the Milky Way, digitized images of humans and an invitation for extraterrestrials to respond.

A celestial event mentioned in an ancient Chinese text turns out to be the oldest known reference to a candidate aurora, predating the next oldest one by some three centuries.

A celestial event mentioned in an ancient Chinese text turns out to be the oldest known reference to a candidate aurora, predating the next oldest one by some three centuries, according to a recent study by Marinus Anthony van der Sluijs, an independent researcher based in Canada, and Hisashi Hayakawa from Nagoya University. This finding was recently published in the journal Advances in Space Research.

The Bamboo Annals, or Zhushu Jinian in Mandarin, chronicle the history of China from the earliest legendary time to the time of their probable composition, in the 4th century BCE. Historical events aside, unusual observations in the sky make an occasional appearance in the text. Although this chronicle has been known to scholars for a long time, a fresh look at such old texts sometimes yields surprising new insights. In this case, the authors examined the mention of a "five-coloured light" seen in the northern part of the sky on a night towards the end of the reign of king Zhao of the Zhou dynasty. While the exact year is uncertain, they used up-to-date reconstructions of Chinese chronology to settle on 977 and 957 BCE as the two most likely years, depending on how Zhao's reign is dated. They found the record of the "five-coloured light" to be consistent with a large geomagnetic storm. When the mid-latitude aurora is sufficiently bright, it can present a spectacle of multiple colours. The researchers cite several examples of this from historical records much closer to our time. The earth's north magnetic pole is known to have been inclined to the Eurasian side in the mid-10th century BCE, about 15° closer to central China than at present. Therefore, the auroral oval could have been visible to observers in central China at times of significant magnetic disturbance. The study estimates that the equatorward boundary of the auroral oval would have been located at a magnetic latitude of 40° or less on the occasion.

In some districts of Maharashtra, including Chandrapur, Yavatmal, Nagpur, Buldhana, Washim, Akola, Wardha, and Bhandara many people were stunned to see objects like electric bulbs leaving blazing marks in the sky during the nighttime on Saturday.

On the same night, people of a village in Sindewahi tehsil of district Chandrapur also reported a metal ring falling on an open plot. In another village of the same tehsil, on the same night, all the people also saw a ball which had fallen in a pond.

According to meteorologist and physicist Professor Kiran Kumar Johre, the three phenomena are also completely unrelated.

The inner nebula of the much-studied supernova Cassiopeia A is not moving smoothly outward. This has been discovered by astronomers from the University of Amsterdam and Harvard. The astronomers suspect that the remains have collided with something. Their finding have been accepted for publication in The Astrophysical Journal.

Cassiopeia A is the remnant of an exploded star in the Cassiopeia constellation, about 11,000 light years away from us. Light from the explosion should have reached Earth for the first time around 1670. However, there was too much gas and dust around the star for the explosion to be seen with the naked eye or with the then very basic telescopes. The Cassiopeia A explosion nebula is expanding at an average rate of 4,000 to 6,000 kilometers per second and has a temperature of about 30 million degrees Celsius. The expansion is most likely occurring in gas that was blown out by the star long before the explosion. Cassiopeia A is now about 16 light years across.

Short clip with English explanation of the discovery that the inner remnants of Cassiopeia A do not expand evenly. Note that the west is on the right. Credit: J. Vink

With the H.E.S.S. observatory and the Fermi satellite, researchers track the eruption of RS Ophiuchi.

For the first time, it has been possible to observe the outburst of a nova in very high-energy gamma light and to follow the glow and subsequent fading over a period of one month. The researchers combined the data from the H.E.S.S. observatory with those from the Fermi satellite and gained insights into the processes underlying the emission of gamma rays. The scientists were surprised to find that the nova apparently accelerates particles to the theoretical limit.

In the constellation of Ophiuchus (the Serpent Bearer) there is a double star system called "RS Ophiuchi", about 7500 light years away, consisting of a white dwarf and a red giant. Their separation is only about one and a half times the distance between the Earth and the Sun, close enough for the white dwarf to continuously pull matter from the atmosphere of its companion.

Episodically, enough material is accumulated on the white dwarf's surface for the strong gravity to ignite a thermonuclear explosion. Between 1898 and 2006, astronomers have previously observed eight such nova outbursts of RS Ophiuchi. On the of August 8, 2021, another outburst occurred that was visible even to the naked eye.

Starting the following night, H.E.S.S. set its sights on the star and was indeed able to detect it. "This is the very first observation of a nova in very-high-energy gamma radiation," says Alison Mitchell of the Friedrich-Alexander-Universität Erlangen-Nürnberg and principal investigator of the H.E.S.S Nova programme. For an unprecedented period of one month - with a brief period of interruption around full moon - H.E.S.S. was able to track the evolving luminosity of the nova.

Complementing the H.E.S.S. observations were lower-energy gamma-ray measurements by the Fermi satellite. Combining data from the two instruments revealed unique insights into the processes underlying the gamma-ray emission and their evolution. In both energy ranges, the rate of gamma-rays received by the instruments displays a period of steady increase before decaying at the same rate.

Astronomers have a thing for big explosions and collisions, and it always seems like they are trying to one-up themselves in finding a bigger, brighter one. There's a new entrant to that category - an event so big it created a burst of particles over 1 billion years ago that is still visible today and is 60 times bigger than the entire Milky Way.

That shockwave was created by the merger of two galaxy clusters to create a supercluster known as Abell 3667. This was one of the most energetic events in the universe since the Big Bang, according to calculations by Professor Francesco de Gasperin and his time from the University of Hamburg and INAF. When it happened over 200 million years ago, it shot out a wave of electrons, similar to how a particle accelerator would. All these years later, those particles are still traveling at Mach 2.5 (1500 km / s), and when they pass through magnetic fields, they emit radio waves.