Amid fears of a Russian invasion of Ukraine, tensions have also soared in the country's east, where Ukrainian forces are locked in a long conflict with Russia-backed separatists.

More than 14,000 people have been killed in nearly eight years of fighting, and a sharp increase in skirmishes last week raised concern that Moscow could use the situation as a pretext for an incursion.

Here is a look at the state of affairs in the rebel-controlled territories in eastern Ukraine:

SEPARATIST REBELLION

When Ukraine's Moscow-friendly president was driven from office by mass protests in February 2014, Russia responded by annexing Ukraine's Crimean Peninsula.

It then threw its weight behind an insurgency in the mostly Russian-speaking east, known as Donbas.

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In April 2014, Russia-backed rebels seized government buildings in the Donetsk and Luhansk regions, proclaimed the creation of "people's republics" and battled Ukrainian troops and volunteer battalions.

The following month, the separatist regions held a popular vote to declare independence and make a bid to become part of Russia.

Moscow hasn't accepted the motion, in the hope of using the regions as a tool to keep Ukraine in its orbit and prevent it from joining NATO.

Ukraine and the West accused Russia of backing the rebels with troops and weapons.

Moscow denied that, saying any Russians who fought in the east were volunteers.

Amid ferocious battles involving tanks, heavy artillery and warplanes, Malaysia Airlines Flight 17 was shot down over eastern Ukraine on July 17, 2014, killing all 298 people aboard.

An international probe concluded that the passenger jet was downed by a Russia-supplied missile from the rebel-controlled territory, but Moscow denied any involvement.

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PEACE AGREEMENTS

After a massive defeat of Ukrainian troops in the battle of Ilovaisk in August 2014, envoys from Kyiv, the rebels and the Organisation for Security and Cooperation in Europe signed a truce in the Belarusian capital of Minsk in September 2014.

The document envisaged an OSCE-observed cease-fire, a pullback of all foreign fighters, an exchange of prisoners and hostages, an amnesty for the rebels and a promise that separatist regions could have a degree of self-rule.

The deal quickly collapsed and large-scale fighting resumed, leading to another major defeat for Ukrainian forces at Debaltseve in January-February of 2015.

France and Germany brokered another peace agreement, which was signed in Minsk in February 2015 by representatives of Ukraine, Russia and the rebels.

It envisaged a new cease-fire, a pullback of heavy weapons and a series of moves toward a political settlement.

A declaration in support of the deal was signed by the leaders of Russia, Ukraine, France and Germany.

FROZEN CONFLICT

The 2015 peace deal was a major diplomatic coup for the Kremlin, obliging Ukraine to grant special status to the separatist regions, allowing them to create their own police force and have a say in appointing local prosecutors and judges.

It also envisaged that Ukraine could only regain control over the roughly 200-kilometre border with Russia in rebel regions after they get self-rule and hold OSCE-monitored local elections — balloting that would almost certainly keep pro-Moscow rebels in power there.

Many Ukrainians see it as a betrayal of national interests and its implementation has stalled.

The Minsk document helped end full-scale fighting, but the situation has remained tense and regular skirmishes have continued along the tense line of contact.

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With the Minsk deal effectively stalled, Moscow's hope to use rebel regions to directly influence Ukraine's politics has failed, but the frozen conflict has drained Kyiv's resources and effectively stymied its goal of joining NATO — which is enshrined in the Ukrainian constitution.

Moscow also has worked to secure its hold on the rebel regions by handing out more than 720,000 Russian passports to roughly one-fifth of their population of about 3.6 million.

It has provided economic and financial assistance to the separatist territories, but the aid has been insufficient to alleviate the massive damage from fighting and shore up the economy.

The Donbas region accounted for about 16 per cent of Ukraine's Gross Domestic Product before the conflict.

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EFFORTS TO REVIVE PEACE DEAL

Amid soaring tensions over the Russian troop concentration near Ukraine, France and Germany have undertaken renewed efforts to encourage compliance with the 2015 deal, in the hope that it could help defuse the standoff.

Facing calls from Berlin and Paris for its implementation, Ukrainian officials have strengthened criticism of the Minsk deal and warned that it could lead to the country's demise.

Two rounds of talks in Paris and Berlin between presidential envoys from Russia, Ukraine, France and Germany have yielded no progress.

Amid the deadlock in talks, the lower house of Russian parliament this week urged Russian President Vladimir Putin to recognise the independence of Donetsk and Luhansk.

Putin signalled, however, that he wasn't inclined to make the move that would effectively shatter the Minsk deal.

ESCALATION OF HOSTILITIES

Ukraine and the rebels accused each other last Thursday of intensive shelling along the line of contact in Donetsk and Luhansk.

Separatist authorities claimed that Ukraine mounted a "large-scale provocation" and said they returned fire.

Ukraine denied opening fire and said the separatists were shelling government-controlled areas with heavy artillery and mortars.

The Ukrainian military command charged that some shells hit a kindergarten in Stanytsia Luhanska, wounding two civilians, and cut power supply to half of the town.

Yasar Halit Cevik, head of the OSCE monitoring mission, said it reported 500 explosions along the contact line between Wednesday evening and 11:20 am Thursday.

Cevik told the United Nations Security Council that the tension appeared to be easing after that with about 30 explosions reported, adding "it is critically important to de-escalate immediately."

With Associated Press

A striking and unprecedented image of a solar eruption has been captured by NASA and the European Space Agency's Solar Orbiter spacecraft.

It's the largest solar prominence ever observed in a single image together with the full disc of the sun, ESA said in a statement released Friday.

The solar eruption took place on February 15 and extended millions of miles into space. The image was taken by the Full Sun Imager of the Extreme Ultraviolet Imager onboard the Solar Orbiter.

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The Full Sun Imager is designed to capture the full solar disc even during close passages of the sun.

"Right now, there is still a lot of 'viewing margin' around the disc, enabling stunning detail to be captured by FSI out to about 3.5 million kilometres, equivalent to five times the radius of the Sun," ESA said.

"At closest approach on 26 March, which will see the spacecraft pass within about 0.3 times the Sun-Earth distance, the Sun will fill a much larger portion of the telescope's field of view."

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ESA described solar prominences as "large structures of tangled magnetic field lines that keep dense concentrations of solar plasma suspended above the Sun's surface, sometimes taking the form of arching loops."

Solar prominences are often associated with coronal mass ejections, a hugely energetic explosion of light, solar material and energy from the Sun. If these ejections are directed toward Earth, they can disrupt technology reliant on satellites. The ejections also cause the northern lights.

However, in this instance, the coronal mass ejection was traveling away from us.

The ESA said the imagery would allow space experts to understand for the first time how events like these connect to the solar disc.

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https://twitter.com/ESASolarOrbiter/status/1494592228571951125?ref_src=twsrc%5Etfw

The sun is getting more active. It started a new 11-year cycle in 2019, and that period's solar maximum – when activity peaks – is predicted to happen about halfway through 2025.

It's important to understand the solar cycle because space weather caused by the sun – eruptions like solar flares and coronal mass ejection events – can impact the power grid, satellites, GPS, airlines, rockets and astronauts in space.

Other space telescopes, such as the ESA/NASA SOHO satellite, frequently capture solar activity but are unable to produce detailed images of the sun's corona or outer most layer, which is regarded as very difficult to study.

Next week, the Solar Orbiter and NASA's Parker Solar Probe will conduct joint observations as Parker makes its next close pass by the sun.

Last year, the Parker spacecraft became the first to "touch the sun."

It successfully flew through the sun's corona, or upper atmosphere, to sample particles and our star's magnetic fields.

The weather on this piping hot exoplanet is truly out of this world.

A massive gas giant orbiting a star about 855 light-years from Earth, WASP-121b may have metal clouds and rain made of liquid gems, according to new research.

A study showing how water atmospherically cycles between the planet's two sides was published Monday in the journal Nature Astronomy.

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The planet, first discovered in 2015, is considered to be an ultrahot Jupiter-like planet because it's hotter and has a greater mass and diameter than the largest planet in our solar system.

Since then, researchers have made discoveries that show WASP-121b only gets stranger the more they learn.

The exoplanet has a glowing water vapour atmosphere and is being deformed into the shape of a football due to the intense gravitational pull of the star it orbits.

Every 30 hours, WASP-121b completes one orbit and is tidally locked, much like the moon is to Earth. That means one side of the planet, the day side, always faces the star. The other side experiences a permanent night that faces space.

"Hot Jupiters are famous for having very bright day sides, but the night side is a different beast. WASP-121b's night side is about 10 times fainter than its day side," said study co-author Dr Tansu Daylan, postdoctoral research fellow in astrophysics at the Massachusetts Institute of Technology, in a statement.

Now, astronomers have studied both sides of the planet to better understand its atmosphere and alien weather using the Hubble Space Telescope.

Extreme water cycle

On Earth, water evaporates and its vapour condenses into clouds, which then release rain. On WASP-121b, water goes through a more vicious cycle.

The water atoms are ripped apart by the blazing hot temperatures experienced by the planet on the day side. These atoms are carried over to the nightside by winds that reach more than 17,703 kilometres per hour). There, the molecules come together once more to form water before being shoved over to the day side again.

"These winds are much faster than our jet stream, and can probably move clouds across the entire planet in about 20 hours," Dr Daylan said. He previously studied the planet using data from NASA's Transiting Exoplanet Survey Satellite mission.

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The temperature differences between the two sides of the planet also mean the night side is cool enough for metal clouds made of iron and corundum to form. Corundum is a mineral found in rubies and sapphires.

Much like water vapour that gets cycled around on WASP-121b, these metal clouds may get shoved over to the day side where the metals vaporise into gases. But before the clouds leave the nightside, they could release rain made of liquid gems.

"With this observation, we're really getting a global view of an exoplanet's meteorology," said lead study author Thomas Mikal-Evans, research group leader at the Max Planck Institute for Astronomy in Germany.

"Despite the discovery of thousands of exoplanets, we've only been able to study the atmospheres of a small fraction due to the challenging nature of the observations," he said.

"We're now moving beyond taking isolated snapshots of specific regions of exoplanet atmospheres, to study them as the 3D systems they truly are."

Dr Mikal-Evans led the study while he was a postdoctoral student at the Massachusetts Institute of Technology's Kavli Institute for Astrophysics and Space Research.

Extraterrestrial weather

The findings also reveal the dramatic differences in temperature between day and night on the planet, which the team determined by tracking the water cycle on WASP-121b.

On the day side, temperatures begin at 2227 degrees Celsius at the deepest layer of the atmosphere and reach 3,227 degrees Celsius at the top layer.

On the night side, things are cooler and reversed, with the warmest temperature being 1527 degrees Celsius and dropping to 1,227 degrees Celsius in the upper atmosphere.

The astronomers will observe WASP-121b later this year using the James Webb Space Telescope.

"It's exciting to study planets like WASP-121 b that are very different to those in our solar system, because they allow us to see how atmospheres behave under extreme conditions," said study co-author Joanna Barstow, research fellow at The Open University in the United Kingdom, in a statement.