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

Only two of the station stones are still there. Credit: Drone Explorer/Shutterstock.

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.

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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Tremendous explosions in a galaxy close to the Milky Way are pouring material equivalent to around 50 million suns into its surroundings. Astronomers mapped this galactic pollution event in high resolution, obtaining important hints about how the space between galaxies becomes filled with chemical elements that eventually become the building blocks of new stars.

The findings came about when the international team studied NGC 4383, a spiral galaxy in the Coma Berenices constellation, using a Very Large Telescope (VLT) instrument called the Multi Unit Spectroscopic Explorer (MUSE). 

The search for extrasolar planets is currently undergoing a seismic shift. With the deployment of the Kepler Space Telescope and the Transiting Exoplanet Survey Satellite (TESS), scientists discovered thousands of exoplanets, most of which were detected and confirmed using indirect methods. But in more recent years, and with the launch of the James Webb Space Telescope (JWST), the field has been transitioning toward one of characterization. In this process, scientists rely on emission spectra from exoplanet atmospheres to search for the chemical signatures we associate with life (biosignatures).

However, there’s some controversy regarding the kinds of signatures scientists should look for. Essentially, astrobiology uses life on Earth as a template when searching for indications of extraterrestrial life, much like how exoplanet hunters use Earth as a standard for measuring “habitability.” But as many scientists have pointed out, life on Earth and its natural environment have evolved considerably over time. In a recent paper, an international team demonstrated how astrobiologists could look for life on TRAPPIST-1e based on what existed on Earth billions of years ago.

The team consisted of astronomers and astrobiologists from the Global Systems Institute, and the Departments of Physics and Astronomy, Mathematics and Statistics, and Natural Sciences at the University of Exeter. They were joined by researchers from the School of Earth and Ocean Sciences at the University of Victoria and the Natural History Museum in London. The paper that describes their findings, “Biosignatures from pre-oxygen photosynthesizing life on TRAPPIST-1e,” will be published in the Monthly Notices of the Royal Astronomical Society (MNRAS).

The TRAPPIST-1 system has been the focal point of attention ever since astronomers confirmed the presence of three exoplanets in 2016, which grew to seven by the following year. As one of many systems with a low-mass, cooler M-type (red dwarf) parent star, there are unresolved questions about whether any of its planets could be habitable. Much of this concerns the variable and unstable nature of red dwarfs, which are prone to flare activity and may not produce enough of the necessary photons to power photosynthesis.

With so many rocky planets found orbiting red dwarf suns, including the nearest exoplanet to our Solar System (Proxima b), many astronomers feel these systems would be the ideal place to look for extraterrestrial life. At the same time, they’ve also emphasized that these planets would need to have thick atmospheres, intrinsic magnetic fields, sufficient heat transfer mechanisms, or all of the above. Determining if exoplanets have these prerequisites for life is something that the JWST and other next-generation telescopes – like the ESO’s proposed Extremely Large Telescope (ELT) – are expected to enable.

But even with these and other next-generation instruments, there is still the question of what biosignatures we should look for. As noted, our planet, its atmosphere, and all life as we know it have evolved considerably over the past four billion years. During the Archean Eon (ca. 4 to 2.5 billion years ago), Earth’s atmosphere was predominantly composed of carbon dioxide, methane, and volcanic gases, and little more than anaerobic microorganisms existed. Only within the last 1.62 billion years did the first multi-celled life appear and evolve to its present complexity.

Moreover, the number of evolutionary steps (and their potential difficulty) required to get to higher levels of complexity means that many planets may never develop complex life. This is consistent with the Great Filter Hypothesis, which states that while life may be common in the Universe, advanced life may not. As a result, simple microbial biospheres similar to those that existed during the Archean could be the most common. The key, then, is to conduct searches that would isolate biosignatures consistent with primitive life and the conditions that were common to Earth billions of years ago.

As Dr. Jake Eager-Nash, a postdoctoral research fellow at the University of Victoria and the lead author of the study, explained to Universe Today via email:

“I think the Earth’s history provides many examples of what inhabited exoplanets may look like, and it’s important to understand biosignatures in the context of Earth’s history as we have no other examples of what life on other planets would look like. During the Archean, when life is believed to have first emerged, there was a period of up to around a billion years before oxygen-producing photosynthesis evolved and became the dominant primary producer, oxygen concentrations were really low. So if inhabited planets follow a similar trajectory to Earth, they could spend a long time in a period like this without biosignatures of oxygen and ozone, so it’s important to understand what Archean-like biosignatures look like.”

For their study, the team crafted a model that considered Archean-like conditions and how the presence of early life forms would consume some elements while adding others. This yielded a model in which simple bacteria living in oceans consume molecules like hydrogen (H) or carbon monoxide (CO), creating carbohydrates as an energy source and methane (CH₄) as waste. They then considered how gases would be exchanged between the ocean and atmosphere, leading to lower concentrations of H and CO and greater concentrations of CH₄. Said Eager-Nash:

“Archean-like biosignatures are thought to require the presence of methane, carbon dioxide, and water vapor would be required as well as the absence of carbon monoxide. This is because water vapor gives you an indication there is water, while an atmosphere with both methane and carbon monoxide indicates the atmosphere is in disequilibrium, which means that both of these species shouldn’t exist together in the atmosphere as atmospheric chemistry would convert all of the one into the other, unless there is something, like life that maintains this disequilibrium. The absence of carbon monoxide is important as it is thought that life would quickly evolve a way to consume this energy source.”

When the concentration of gases is higher in the atmosphere, the gas will dissolve into the ocean, replenishing the hydrogen and carbon monoxide consumed by the simple life forms. As biologically produced methane levels increase in the ocean, it will be released into the atmosphere, where additional chemistry occurs, and different gases are transported around the planet. From this, the team obtained an overall composition of the atmosphere to predict which biosignatures could be detected.

“What we find is that carbon monoxide is likely to be present in the atmosphere of an Archean-like planet orbiting an M-Dwarf,” said Eager-Nash. “This is because the host star drives chemistry that leads to higher concentrations of carbon monoxide compared to a planet orbiting the Sun, even when you have life-consuming this [compound].”

For years, scientists have considered how a circumsolar habitable zone (CHZ) could be extended to include Earth-like conditions from previous geological periods. Similarly, astrobiologists have been working to cast a wider net on the types of biosignatures associated with more ancient life forms (such as retinal-photosynthetic organisms). In this latest study, Eager-Nash and his colleagues have established a series of biosignatures (water, carbon monoxide, and methane) that could lead to the discovery of life on Archean-era rocky planets orbiting Sun-like and red dwarf suns.

Further Reading: arXiv