Our sun is known for its occasional outburst of energy called a solar flare, which can trigger space weather capable of disrupting communications and power infrastructure here on Earth.

But we should really be grateful that we doesn’t exist around a star that erupts with so-called “superflares” that can be 100 to 10,000 times more energetic than even the most powerful solar flares. A superflare emerging from the sun could potentially be catastrophic for the Earth, delivering serious damage to our planet’s atmosphere and to the lifeforms that depend upon it. Fortunately, superflares are seen around stars so far away that they are mere points of light in the sky from our perspective. 

These energetic flares appear to astronomers as a sudden and extreme brightening of those distant specks, and this has led scientists to play stellar detective on a quest to discover why some stars erupt so violently. 

Editor’s note: This article was first published in 2020 and has been updated.

When we stargaze, we bask in photons that have traveled for many millennia before reaching our eyes. To us, the stars appear fixed on a so-called celestial sphere that encapsulates our entire earthly existence.

The truth, of course, is that no such sphere exists. Instead, stars and galaxies are scattered through the cosmos at distances so great they’re incomprehensible to us.

But not all celestial phenomena exist so far away. Every day, shooting stars fail to recognize a boundary between space and Earth, dropping rocks from above — and often with dramatic results.

Our planet is vast, so meteorites typically don’t concern us. But every once in a while, these objects actually strike humans and our property.

“I do strongly suspect that stats on ‘death by asteroid’ have been severely undercounted through human history,” NASA Planetary Defense Officer Lindley Johnson told Astronomy via email. “It’s only been in the last half century or so that we’ve even realized that such a thing could happen.”

However, researchers still have not found a single confirmed case of death by space rock. But that’s not to say we haven’t come close. Modern history is full of near misses. On many occasions, space rocks have exploded over populated areas and sent thousands of meteorites raining down.

One of the most recent and well-known examples occurred in Chelyabinsk, Russia, in 2013, when a house-sized asteroid exploded over the city and injured some 1,200 people. Further back, on Jan. 30, 1868, a meteor exploded outside a town called Pultusk, near Warsaw, Poland, creating a literal meteor shower: More than 100,000 stones fell from the sky. The biggest recovered meteorite (a fragment of a space rock that makes it to the ground) weighed 20 pounds (9 kilograms). It’s the largest meteorite fall on record.

“The citizens of Warsaw gazed, petrified with fear, on the rapid approach of an immense ball of fire, which burst over their heads with a noise and shock such as never before had been seen or heard on the surface of the Earth,” mineral expert Lewis Feuchtfanger reported at a scientific conference in 1868. If someone flew over a populated area, dropping hundreds of thousands of stones from the sky, you might expect at least one person to get hurt. Yet there are no reports of injuries from Poland on that day.

However, if ancient scholars can be trusted, humans haven’t always been so lucky. Researchers mining ancient texts in recent decades have discovered that historical records are surprisingly rich with accounts of apparent deaths due to falling space rocks. In most cases, there’s no physical evidence to confirm these stories. Yet their presence in official histories and similarities to modern accounts lead some scientists to believe at least some of the events must have really occurred.

Chinese histories in particular are rich with accounts from government scholars and astronomers that document times when “a star fell.” These records were kept consistently across many provinces and passed from dynasty to dynasty, chronicling significant events spanning thousands of years. If these documents accurately portray meteor fireballs, then somewhere between hundreds to tens of thousands of people have been killed by falling space rocks.

Here, we’ve compiled a list of some of the most compelling accounts.

Around 1700 B.C.: meteor explosion may have destroyed Sodom and Gomorrah

Roughly 3,700 years ago, a meteor may have exploded over the Dead Sea city of Tall el-Hammam. Located in what is now Jordan, some scientists believe Tall el-Hammam was the biblical city of Sodom. And when the blast occurred, it caused massive devastation, according to a group of Christian scientists who’ve studied the site for more than a decade. Their research was presented in 2017 at an annual meeting of The Meteoritical Society.

Archaeologists say the explosion instantly devastated hundreds of square miles north of the Dead Sea, destroying 100 percent of nearby cities and towns. The blast also may have stripped away once-fertile soils and coated agricultural lands with superheated brine ejected from the Dead Sea. Evidence of agricultural activity doesn’t return to the landscape for at least 600 years.

In its heyday, the city had enormous fortification walls and was a thriving metropolis, but its structures all appear to have crumbled due to one dramatic event. The team says they’ve found a variety of clues about what happened in Tall el-Hammam, including the instant heating of pottery shards and rocks to over 14,000 degrees Fahrenheit (7760 degrees Celsius).

In the past, scientists have suggested Tall el-Hammam was destroyed by earthquakes or petrochemical fires, but those scenarios can’t fully explain the high heat, vast quantities of ash, or why the structures all collapsed in one direction. Only an exploding space rock could’ve caused that kind of momentary heat pulse.

If it truly was an air blast, the effect would have been like setting off an atomic bomb over the ancient city, likely killing huge numbers of people and rendering it incapable of supporting life for centuries. And, just perhaps, that scenario could explain the destruction of the biblical cities of Sodom and Gomorrah.

Jan. 14, A.D. 616: 10 rebels killed in wall collapse

According to ancient official Chinese records, a large “shooting star” fell on the rebel Lu Ming-yueh’s camp in January 616, killing 10 people. An account of the event was recorded in the Book of Sui, a history of the Sui dynasty commissioned by the emperor and composed by eminent scholars of the time.

The document claims this shooting star knocked out a wall-attacking tower, or siege tower, resulting in 10 deaths. Scientists examining the account in 1994 suggested that a meteorite would need to be relatively large to have caused that kind of damage, weighing dozens or even hundreds of pounds.

The official account and a description of the fireball lend credibility to the story. However, the team also suggests the incident could have been tied to a military campaign. If so, the story we’re left with is simply a form of ancient propaganda.

Around 1341: ‘Iron Rain’ Over Yunnan Province Kills People and Animals 

A group of vivid descriptions found in ancient Chinese historical documents record an “iron rain” that fell over Yunnan Province roughly 700 years ago. The accounts carry a number of different dates, ranging from 1321 to 1361, possibly as a result of copying errors in recent centuries. But researchers who studied earlier documents found that, before modern transcription, they all agreed on a date of 1341.

The descriptions of what happened come from cities and towns spread over hundreds of square miles of Yunnan Province. The local histories also carry similar language, suggesting the many witness testimonies all describe the same dramatic event. Because the fireball was seen across such a vast area, it would’ve had to have been a very large meteoroid to begin with.

“Houses and hilltops were all with bore-holes,” as a result of the iron rain, the accounts say. Astronomers think those word choices sound similar to accounts of more recent iron meteorite falls, where fragments of the parent body left tiny craters across landscapes. The documents also describe damaged crops and people’s homes left half in ruins. The histories don’t give an exact number of people who purportedly died from being hit by meteorites, but instead say “most of the people and animals struck by them were killed.”

April 4, 1490: 10,000 people killed in Chinese city of Ch’ing-yang

According to numerous Chinese historical records kept by central and local governments, as well as other sources, on April 4, 1490, somewhere between 10,000 and tens of thousands of people were killed in an event that may have been caused by an asteroid exploding over the city of Ch’ing-yang (or Qingyang).

It sounds so horrific it’s hard to believe, but some of the specifics match up with other well-documented events in more recent history. The records say the stones were all different sizes, with some as big as goose eggs and weighing about 3 pounds. Others were as small as water chestnuts.

This small range of meteorite sizes doesn’t seem likely for an impact event that killed so many people, where you might expect larger stones to be the bringers of death. However, some astronomers wonder if these accounts describe a Tunguska-style airburst that leveled a city.

Whatever the cause, the accounts say the surviving residents of Ch’ing-yang all fled in the aftermath.

In a weird coincidence, Chinese, Japanese and Korean astronomers also discovered a bright comet in 1490. This comet was seen to break apart in the night sky a century later. Astronomers now know this cometary fragmentation created the annual Quadrantid meteor shower, as well as the near-Earth asteroid 2003 EH1. There’s no evidence the meteorite deaths are connected, but it’s clear Asian astronomers of the day were well aware of celestial happenings.

1648: Two sailors killed on the Dutch ship Malacca

In 1648, two sailors were killed while at sea when a large rock crashed down from the heavens and landed on the ship’s deck, according to Capt. Olof E. Willman. The captain wrote down his account of the event nearly 20 years later, and it was eventually included in Alexander von Humboldt’s book Kosmos.

Willman claimed their ship, the Malacca, was traveling along the prominent spice trade route between Holland and the Dutch East Indies when an 8-pound rock fell from the sky. Two of his men were struck and died as a result of the impact.

Historians consider Willman’s account reliable, but in 1994 a Swedish scientist showed that there were also at least 20 hazardous and active volcanoes along their route. So it’s also possible that one of those launched a “volcanic bomb” that struck the ship.

Aug. 10, 1888: Ottoman Empire records suggest meteorite death

At around 8:30 p.m. on the night of Aug. 10, 1888, a bright fireball carried a trail of smoke as it passed over villages in Iraq before exploding and raining stones on a “pyramid-shaped” hill. As a result, a man who lived in the area was killed, while another was paralyzed.

Researchers found this historical account in the former Ottoman Empire’s digitized official records. They published their findings in 2020 in the journal Meteoritics & Planetary Science.

Ozan Unsalan, a planetary scientist at Ege University in Turkey, worked with a team to search for keywords like “meteorite,” “fireball” and “stones from the sky.” They found 10 documents that matched their search, including three tied to a single fireball event. They also found evidence of several additional large meteor explosions in the Ottoman Empire’s centuries’ worth of records.

The documents say rocks from the impact were sent back to the central government, but so far the team hasn’t been able to locate them in museums or archives.

However, based on historical accounts, death from above seems to be nothing new.

Well over 5,000 planets have been found orbiting other star systems. One of the satellites hunting for them is TESS, the Transiting Exoplanet Survey Satellite. Astronomers using TESS think they are made a rather surprising discovery; their first free-floating – or rogue – planet. The planet was discovered using gravitational microlensing where the planet passed in front of a star, distorting its light and revealing its presence.

We are all familiar with the eight planets in our Solar System and perhaps becoming familiar with the concept of exoplanets. But there is another category of planet, the rogue planets. These mysterious objects travel through space without being gravitationally bound to any star. Their origin has been cause for much debate but popular theory suggests they were ejected from their host star system during formation, or perhaps later due to gravitational interaction. 

Simulations have suggested that these ‘free-floating planets’ or FFPs should be abundant in the Galaxy yet until now, not many have been detected. The popular theory of ejection from star systems may not be the full story though. It is now thought that different formation mechanisms will be responsible for different FFP masses. Those FFPs that are high mass may form in isolation from the collapse of gas whilst those at the low mass end (comparable to Earth) are likely to have been subjected to gravitational ejection from the system. A paper published in 2023 even suggests that those FFPs are likely to outnumber those bound planets across the Galaxy!

Detecting such wandering objects among the stars is rather more of a challenge than you might expect. Their limited emission (or reflection) of electromagnetic radiation makes them pretty much impossible to observe. Enter gravitational microlensing, a technique that relies upon an FFP passing in front of a star, it’s gravity then focussing light from the distant star resulting in a brief brightness change as the planet moves along its line of sight. To date, only three FFPs have been detected from Earth using this technique. 

A team of astronomers have been using TESS to search for such microlensing events. TESS was launched in April 2018 and whilst in orbit, scans large chunks of sky to monitor the brightness of tens of thousands of stars. The detection of light changes may reveal the passage of an FFP as it drifts silently in front of the star. It’s not an easy hunt though as asteroids in our Solar System, exoplanets bound to stars and even stellar flares can all give false indications but thankfully the team led by Michelle Kunimoto have algorithms that will help to identify potential targets. 

The team published their findings recently in the Astrophysical Journal and reported one FFP candidate event associated with the star TIC-107150013 which is 3.2 parsec away. The event lasted 0.074 days +/- 0,002 and revealed a light curve with features expected of a FFP. This marks the first FFP discovered by TESS, an exciting step along the way to start to unravel the mysteries surrounding these strange alien worlds.

Source : Searching for Free-Floating Planets with TESS: I. Discovery of a First Terrestrial-Mass Candidate

Let’s be honest — many of us hate dusting. 

But at least even as thick the dust coating might be around the house, with one fell swoop of duster, the particles are wiped away and the surface is clean again. Unfortunately, for our astronauts and spacecraft, dust poses much more of a threat on other bodies such as on the moon and Mars due to the harsh, ‘sticky’ nature of the dust on those worlds. 

heic2408 — Photo Release

23 April 2024

In celebration of the 34th anniversary of the launch of the legendary NASA/ESA Hubble Space Telescope on 24 April, astronomers took a snapshot of the Little Dumbbell Nebula (also known as Messier 76, M76, or NGC 650/651) located 3400 light-years away in the northern circumpolar constellation Perseus. The photogenic nebula is a favourite target of amateur astronomers.

M76 is classified as a planetary nebula, an expanding shell of glowing gases that were ejected from a dying red giant star. The star eventually collapses to an ultra-dense and hot white dwarf. A planetary nebula is unrelated to planets, but has that name because astronomers in the 1700s using low-power telescopes thought this type of object resembled a planet.

M76 is composed of a ring, seen edge-on as the central bar structure, and two lobes on either opening of the ring. Before the star burned out, it ejected the ring of gas and dust. The ring was probably sculpted by the effects of the star that once had a binary companion star. This sloughed-off material created a thick disc of dust and gas along the plane of the companion’s orbit. The hypothetical companion star isn’t seen in the Hubble image, and so it could have been later swallowed by the central star. The disc would be forensic evidence for that stellar cannibalism.

The primary star is collapsing to form a white dwarf. It is one of the hottest stellar remnants known, at a scorching 120 000 degrees Celsius, 24 times our Sun’s surface temperature. 
The sizzling white dwarf can be seen as a pinpoint in the centre of the nebula. A star visible in projection beneath it is not part of the nebula.



Pinched off by the disc, two lobes of hot gas are escaping from the top and bottom of the ‘belt’ along the star’s rotation axis that is perpendicular to the disc. They are being propelled by the hurricane-like outflow of material from the dying star, tearing across space at two million miles per hour. That’s fast enough to travel from Earth to the Moon in a little over seven minutes! This torrential ‘stellar wind’ is ploughing into cooler, slower-moving gas that was ejected at an earlier stage in the star’s life, when it was a red giant. Ferocious ultraviolet radiation from the super-hot star is causing the gases to glow. The red colour is from nitrogen, and blue is from oxygen.


Given that our solar system is 4.6 billion years old, the entire nebula is a flash in the pan by cosmological timekeeping. It will vanish in about 15 000 years.


34 years of science and imagery

Since its launch in 1990 Hubble has made 1.6 million observations of over 53 000 astronomical objects. To date, the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute in Baltimore, Maryland holds 184 terabytes of processed data that are science-ready for use by astronomers around the world to use for research and analysis. A European mirror of the public data is hosted at ESA’s European Space Astronomy Centre (ESAC), in the European Hubble Space Telescope (eHST) Science Archive.

Since 1990, 44 000 science papers have been published from Hubble observations. This includes a record 1056 papers published in 2023, of which 409 were led by authors in the ESA Member States. The demand for using Hubble is so high it is currently oversubscribed by a factor of six.

Throughout its past year of science operations, new discoveries made using Hubble include finding water in the atmosphere of the smallest exoplanet to date, spotting a bizarre cosmic explosion far from any host galaxy, following spokes on the rings of Saturn and finding the unexpected home of the most distant and powerful fast radio burst yet seen. Hubble’s studies of the asteroid Dimorphos, the target of a deliberate NASA spacecraft collision in September 2022 to alter its trajectory, continued with the detection of boulders released by the impact.

Hubble has also continued to provide spectacular images of celestial targets including spiral galaxies, globular clusters and star-forming nebulae. A newly forming star was the source of a cosmic light show. Hubble imagery was also combined with infrared observations from the NASA/ESA/CSA James Webb Space Telescope to create one of the most comprehensive views of the Universe ever, an image of galaxy cluster MACS 0416.

Most of Hubble’s discoveries were not anticipated before launch, such as supermassive black holes, the atmospheres of exoplanets, gravitational lensing by dark matter, the presence of dark energy, and the abundance of planet formation among stars. Hubble will continue research in those domains, as well as capitalising on its unique ultraviolet-light capability to examine such things as Solar System phenomena, supernova outbursts, the composition of exoplanet atmospheres, and dynamic emission from galaxies. And Hubble investigations continue to benefit from its long baseline of observations of Solar System objects, variable stellar phenomena and other exotic astrophysics of the cosmos.

The performance characteristics of the James Webb Space Telescope were designed to be uniquely complementary to Hubble, and not a substitute. Future Hubble research also will take advantage of the opportunity for synergies with Webb, which observes the Universe in infrared light. Combined together, the complementary wavelength coverage of the two space telescopes expands on groundbreaking research in such areas as protostellar discs, exoplanet composition, unusual supernovae, cores of galaxies and chemistry of the distant Universe.

The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the Universe.

More information

The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

Image credit: NASA, ESA, STScI, A. Pagan (STScI)

Links

Contacts

Bethany Downer
ESA/Hubble Chief Science Communications Officer
Email: Bethany.Downer@esahubble.org

When it comes to its connection to the sky, Stonehenge is best known for its solar alignments. Every midsummer’s night tens of thousands of people gather at Stonehenge to celebrate and witness the rising Sun in alignment with the Heel stone standing outside of the circle. Six months later a smaller crowd congregates around the Heel stone to witness the midwinter Sun setting within the stone circle.

But a hypothesis has been around for 60 years that part of Stonehenge also aligns with moonrise and moonset at what is called a major lunar standstill. Although a correlation between the layout of certain stones and the major lunar standstill has been known about for several decades, no one has systematically observed and recorded the phenomenon at Stonehenge.

This is what we are aiming to do in a project bringing together archaeologists, astronomers and photographers from English Heritage, Oxford, Leicester and Bournemouth universities as well as the Royal Astronomical Society.

There is now an abundance of archaeological evidence that indicates the solar alignment was part of the architectural design of Stonehenge. Around 2500 BC, the people who put up the large stones and dug an avenue into the chalk seemed to want to cement the solstice axis into the architecture of Stonehenge.

Archaeological evidence from nearby Durrington Walls, the place where scientists believe the ancient people who visited Stonehenge stayed, indicates that of the two solstices it was the midwinter one that drew the largest crowd.

But Stonehenge includes other elements, such as 56 pits arranged in a circle, an earthwork bank and ditch, and other smaller features such as the four station stones. These are four sarsen stones, a form of silicified sandstone common in Wiltshire, that were carefully placed to form an almost exact rectangle encompassing the stone circle.

Only two of these stones are still there, and they pale in comparison to their larger counterparts as they are only a few feet high. So what could their purpose be?

Lunar standstill

The rectangle that they form is not just any rectangle. The shorter sides are parallel to the main axis of the stone circle and this may be a clue as to their purpose. The longer sides of the rectangle skirt the outside of the stone circle.

It is these longer sides that are thought to align with the major lunar standstill. If you marked the position of moonrise (or set) over the course of a month you would see that it moves between two points on the horizon. These southern and northern limits of moonrise (or set) change on a cycle of 18.6 years between a minimum and a maximum range – the so-called minor and major lunar standstills, respectively.

The major lunar standstill is a period of about one and a half to two years when the northernmost and southernmost moonrises (or sets) are furthest apart. When this happens the Moon rises (and sets) outside the range of sunrises and sets, which may have imbued this celestial phenomenon with meaning and significance.

The strongest evidence we have for people marking the major lunar standstill comes from the US southwest. The Great House of Chimney Rock, a multi-level complex built by the ancestral Pueblo people in the San Juan National Forest, Colorado, more than 1,000 years ago.

It lies on a ridge that ends at a natural formation of twin rock pillars – an area that has cultural significance to more than 26 native American tribal nations. From the vantage point of the Great House, the Sun will never rise in the gap between the pillars.

However, during a major standstill the Moon does rise between them in awe-inspiring fashion. Excavations unearthed preserved wood that meant researchers could date to the year episodes of construction of the Great House.

Of six cutting dates, four correspond to major lunar standstill years between the years AD1018 and AD1093, indicating that the site was renewed, maintained or expanded on consecutive major standstills.

Returning to southern England, archaeologists think there is a connection between the major lunar standstill and the earliest construction phase of Stonehenge (3000-2500 BC), before the sarsen stones were brought in.

Several sets of cremated human remains from this phase of construction were found in the southeastern part of the monument in the general direction of the southernmost major standstill moonrise, where three timber posts were also set into the bank. It is possible that there was an early connection between the site of Stonehenge and the Moon, which was later emphasized when the station stone rectangle was built.

The major lunar standstill hypothesis, however, raises more questions than it answers. We don’t know if the lunar alignments of the station stones were symbolic or whether people were meant to observe the Moon through them. Neither do we know which phases of the Moon would be more dramatic to witness.

A search for answers

In our upcoming work, we will be trying to answer the questions the major lunar standstill hypothesis raises. It’s unclear whether the Moon would have been strong enough to cast shadows and how they would have interacted with the other stones. We will also need to check whether the alignments can still be seen today or if they are blocked by woods, traffic and other features.

The Moon will align with the station stone rectangle twice a month from about February 2024 to November 2025, giving us plenty of opportunities to observe this phenomenon in different seasons and phases of the Moon.

To bring our research to life, English Heritage will livestream the southernmost Moonrise in June 2024, and host a series of events throughout the year, including talks, a pop-up planetarium, stargazing and storytelling sessions.

Across the Atlantic, our partners at the US Forest Service are developing educational materials about the major lunar standstill at Chimney Rock National Monument. This collaboration will result in events showcasing and debating the lunar alignments at both Stonehenge and at Chimney Rock.

Astrobiologists continue to work towards determining which biosignatures might be best to look for when searching for life on other worlds. The most common idea has been to search for evidence of plants that use the green pigment chlorophyll, like we have on Earth. However, a new paper suggests that bacteria with purple pigments could flourish under a broader range of environments than their green cousins. That means current and next-generation telescopes should be looking for the emissions of purple lifeforms.

“Purple bacteria can thrive under a wide range of conditions, making it one of the primary contenders for life that could dominate a variety of worlds,” said Lígia Fonseca Coelho, a postdoctoral associate at the Carl Sagan Institute (CSI) and first author of “Purple is the New Green: Biopigments and Spectra of Earth-like Purple Worlds,” published in the Monthly Notices of the Royal Astronomical Society: Letters.

According to NASA’s Exoplanet Archive, 5612 extrasolar planets have been found so far, as of this writing, and another 10,000 more are considered planetary candidates, but have not yet been confirmed. Of all those, there are just over 30 potentially Earth-like worlds, planets that lie in their stars’ habitable zones where conditions are conducive to the existence of liquid water on surface.

But Earth-like has a broad meaning, ranging from size, mass, composition, and various chemical makeups. While being within a star’s habitable zone certainly means there’s the potential for life, it doesn’t necessarily mean that life could have emerged there, or even if it did, the life on that world might look very different from Earth.

“While oxygenic photosynthesis gives rise to modern green landscapes, bacteriochlorophyll-based anoxygenic phototrophs can also colour their habitats and could dominate a much wider range of environments on Earth-like exoplanets,” Coelho and team wrote in their paper. “While oxygenic photosynthesis gives rise to modern green landscapes, bacteriochlorophyll-based anoxygenic phototrophs can also colour their habitats and could dominate a much wider range of environments on Earth-like exoplanets.”

The researchers characterized the reflectance spectra of a collection of purple sulfur and purple non-sulfur bacteria from a variety of anoxic and oxic environments found here on Earth in a variety of environments, from shallow waters, coasts and marshes to deep-sea hydrothermal vents. Even though these are collectively referred to as “purple” bacteria, they actually include a range of colors from yellow, orange, brown and red due to pigments  — such as those that make tomatoes red and carrots orange.

These bacteria thrive on low-energy red or infrared light using simpler photosynthesis systems utilizing forms of chlorophyll that absorb infrared and don’t make oxygen. They are likely to have been prevalent on early Earth before the advent of plant-type photosynthesis, the researchers said, and could be particularly well-suited to planets that circle cooler red dwarf stars – the most common type in our galaxy.

That means this type of bacteria might be more prevalent on more and a wider variety of exo-worlds.

On a world where these bacteria might be dominant, it would produce a distinctive “light fingerprint” detectable by future telescopes.

In their paper, Coelho and team presented models for Earth-like planets where purple bacteria might dominate the surface and show the impact of their signatures on the reflectance spectra of terrestrial exoplanets.

“Our research provides a new resource to guide the detection of purple bacteria and improves our chances of detecting life on exoplanets with upcoming telescopes,” the team wrote.

“We need to create a database for signs of life to make sure our telescopes don’t miss life if it happens not to look exactly like what we encounter around us every day,” said co-author Lisa Kaltenegger, CSI director and associate professor of astronomy at Cornell University, in a press release from Cornell.

Science & Exploration

23/04/2024
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In celebration of the 34th anniversary of the launch of the legendary NASA/ESA Hubble Space Telescope on 24 April, astronomers took a snapshot of the Little Dumbbell Nebula (also known as Messier 76, M76, or NGC 650/651) located 3400 light-years away in the northern circumpolar constellation Perseus. The photogenic nebula is a favourite target of amateur astronomers.

M76 is classified as a planetary nebula, an expanding shell of glowing gases that were ejected from a dying red giant star. The star eventually collapses to an ultra-dense and hot white dwarf. A planetary nebula is unrelated to planets, but has that name because astronomers in the 1700s using low-power telescopes thought this type of object resembled a planet.

M76 is composed of a ring, seen edge-on as the central bar structure, and two lobes on either opening of the ring. Before the star burned out, it ejected the ring of gas and dust. The ring was probably sculpted by the effects of the star that once had a binary companion star. This sloughed-off material created a thick disc of dust and gas along the plane of the companion’s orbit. The hypothetical companion star isn’t seen in the Hubble image, and so it could have been later swallowed by the central star. The disc would be forensic evidence for that stellar cannibalism.

The primary star is collapsing to form a white dwarf. It is one of the hottest stellar remnants known, at a scorching 120 000 degrees Celsius, 24 times our Sun’s surface temperature. 
The sizzling white dwarf can be seen as a pinpoint in the centre of the nebula. A star visible in projection beneath it is not part of the nebula.



Pinched off by the disc, two lobes of hot gas are escaping from the top and bottom of the ‘belt’ along the star’s rotation axis that is perpendicular to the disc. They are being propelled by the hurricane-like outflow of material from the dying star, tearing across space at two million miles per hour. That’s fast enough to travel from Earth to the Moon in a little over seven minutes! This torrential ‘stellar wind’ is ploughing into cooler, slower-moving gas that was ejected at an earlier stage in the star’s life, when it was a red giant. Ferocious ultraviolet radiation from the super-hot star is causing the gases to glow. The red colour is from nitrogen, and blue is from oxygen.


Given that our solar system is 4.6 billion years old, the entire nebula is a flash in the pan by cosmological timekeeping. It will vanish in about 15 000 years.


34 years of science and imagery

Since its launch in 1990 Hubble has made 1.6 million observations of over 53 000 astronomical objects. To date, the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute in Baltimore, Maryland holds 184 terabytes of processed data that are science-ready for use by astronomers around the world to use for research and analysis. A European mirror of the public data is hosted at ESA’s European Space Astronomy Centre (ESAC), in the European Hubble Space Telescope (eHST) Science Archive.

Since 1990, 44 000 science papers have been published from Hubble observations. This includes a record 1056 papers published in 2023, of which 409 were led by authors in the ESA Member States. The demand for using Hubble is so high it is currently oversubscribed by a factor of six.

Throughout its past year of science operations, new discoveries made using Hubble include finding water in the atmosphere of the smallest exoplanet to date, spotting a bizarre cosmic explosion far from any host galaxy, following spokes on the rings of Saturn and finding the unexpected home of the most distant and powerful fast radio burst yet seen. Hubble’s studies of the asteroid Dimorphos, the target of a deliberate NASA spacecraft collision in September 2022 to alter its trajectory, continued with the detection of boulders released by the impact.

Hubble has also continued to provide spectacular images of celestial targets including spiral galaxies, globular clusters and star-forming nebulae. A newly forming star was the source of a cosmic light show. Hubble imagery was also combined with infrared observations from the NASA/ESA/CSA James Webb Space Telescope to create one of the most comprehensive views of the Universe ever, an image of galaxy cluster MACS 0416.

Most of Hubble’s discoveries were not anticipated before launch, such as supermassive black holes, the atmospheres of exoplanets, gravitational lensing by dark matter, the presence of dark energy, and the abundance of planet formation among stars. Hubble will continue research in those domains, as well as capitalising on its unique ultraviolet-light capability to examine such things as Solar System phenomena, supernova outbursts, the composition of exoplanet atmospheres, and dynamic emission from galaxies. And Hubble investigations continue to benefit from its long baseline of observations of Solar System objects, variable stellar phenomena and other exotic astrophysics of the cosmos.

The performance characteristics of the James Webb Space Telescope were designed to be uniquely complementary to Hubble, and not a substitute. Future Hubble research also will take advantage of the opportunity for synergies with Webb, which observes the Universe in infrared light. Combined together, the complementary wavelength coverage of the two space telescopes expands on groundbreaking research in such areas as protostellar discs, exoplanet composition, unusual supernovae, cores of galaxies and chemistry of the distant Universe.

The Hubble Space Telescope has been operating for over three decades and continues to make ground-breaking discoveries that shape our fundamental understanding of the Universe.

 

More information
The Hubble Space Telescope is a project of international cooperation between ESA and NASA.

Release on esahubble.org

Contact:
ESA Media relations
media@esa.int

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