Monday, June 17, 2024

SPACE




How to see the 2024 nova explosion without a telescope
DW
YESTERDAY

Gearing up to witness the nova explosion of T Coronae Borealis this September? It promises to be a once-in-a-lifetime astronomical event.


An illustration of an event like a nova explosion showing a white dwarf and a red giant interacting
Image: NASA/CXC/M.Weis

It's not often that a dark spot in space illuminates our planet, but that is exactly what professional and amateur astronomers expect to happen in September when a once-in-a-lifetime nova explosion 3,000 light-years from Earth will light up our night sky.
What is a nova explosion?

A nova explosion is the dramatic instance of a star exploding as it interacts with another, nearby star. It's a one of many, repeated moments during the long, slow, death of two neighboring stars in the same system.

Astronomers are waiting for the fiery explosion of T Coronae Borealis, also dubbed the "Blaze Star" and known to astronomers as "T CrB".

The system contains two stars — a white dwarf and a red giant. The white dwarf is an incredibly dense remnant of a once larger star. It's about the size of planet Earth but with the same mass as our Sun.

Its neighbor, the red giant, is in its final years of existence and is slowly being stripped of hydrogen by the gravitational pull of the denser white dwarf.

This star "cannibalism" causes a tremendous buildup of pressure and heat, which eventually triggers a huge thermonuclear explosion. The explosion doesn't completely destroy the stars, however, and so this event repeats over time. It can carry on for hundreds of thousands of years.

For T CrB, this nova event happens roughly every 80 years — it's a like Halley's Comet event every 76 years — so, astronomers call T CrB a "recurrent" nova.

They believe T CrB's prior eruptions were observed as long ago as December 1787 and even October 1217 AD.


Is a nova the same as a supernova?

No. A supernova is the final explosion that utterly destroys stars. In a nova event, the dwarf star remains intact, which is why nova events typically repeat themselves.

Different nova events have different cycles, ranging from a few years to hundreds of thousands of years.

What does a nova look like?


The explosion of a nova blasts away star matter in a blinding light, but it won't look like a star explosion you see in the movies — thankfully, we're too far away to see this level of detail.

To the naked eye, the nova will instead look like a new star has appeared in the sky. People with high-powered telescopes will be able to see the nova's brightly colored luminosity in some detail.

Will we be able to see the nova without a telescope?


Yes! When T CrB erupts, its luminosity will increase dramatically, making it visible to the naked eye for several days.

The Northern Crown is a horseshoe-shaped curve of stars west of the Hercules constellation, ideally spotted on clear nights.

To find the Northern Crown, locate the two brightest stars in the Northern Hemisphere: Arcturus and Vega. Tracing a line between the two stars will lead you to the Northern Crown, where T CrB lies.

The European Space Agency told DW that all telescopes were already pointing towards T CrB, waiting to capture the event, but that there are no images as yet.
When will the nova be visible?

All signs point to the nova explosion happening in September 2024. However, novae can be unpredictable, so astrophysicists say it's difficult to know exactly when the T CrB nova will occur.

Have nova events been seen during history?


T CrB nova was last seen from Earth in 1946. The first recorded sighting of the T CrB nova was believed to be more than 800 years ago in 1217, when an abbot in the town of Ursberg, Germany, noted "a faint star that for a time shone with great light."

The abbot wrote the light lasted for "many days” and was thought to be a "wonderful sign." Other celestial events like comets were believed to be bad omens.

Astronomers have recorded supernova events much further back in history. The first sighting of a supernova goes back almost 2000 years to 185 CE, when Chinese astronomers saw a strange "guest star" appear in the night sky for eight months.

Edited by: Zulfikar Abbany

Sources:

NASA Astrophysics https://science.nasa.gov/astrophysics

NASA, Global Astronomers Await Rare Nova Explosion, June 2024 https://www.nasa.gov/centers-and-facilities/marshall/nasa-global-astronomers-await-rare-nova-explosion/

The recurrent nova T CrB had prior eruptions observed near December 1787 and October 1217 AD. Journal for the History of Astronomy, November 2023 https://doi.org/10.1177/00218286231200492


Fred Schwaller Science writer fascinated by the brain and the mind, and how science influences society@schwallerfred


Satellites to monitor marine debris from space


This is what emerges from a study led by the ICM-CSIC recently published in the prestigious journal Nature Communications



SPANISH NATIONAL RESEARCH COUNCIL (CSIC)

Map of the Mediterranean Sea showing the locations of marine debris accumulations detected thanks to the European satellite Copernicus Sentinel-2. 

IMAGE: 

MAP OF THE MEDITERRANEAN SEA SHOWING THE LOCATIONS OF MARINE DEBRIS ACCUMULATIONS DETECTED THANKS TO THE EUROPEAN SATELLITE COPERNICUS SENTINEL-2. EACH RED CIRCLE REPRESENTS AN ACCUMULATION DETECTED DURING THE OBSERVATION PERIOD FROM JUNE 2015 TO SEPTEMBER 2021. THE BLUE ZONES ON LAND CORRESPOND TO THE URBAN AND INDUSTRIAL AREAS OF THE COUNTRIES BORDERING THE MEDITERRANEAN SEA.

view more 

CREDIT: MANUEL ARIAS / ANDRÉS CÓZAR





Detecting marine debris from space is now a reality, according to a new study led by the Institut de Ciències del Mar (ICM-CSIC) and the University of Cadiz recently published in the prestigious journal Nature Communications. Until now, the amount of litter -mostly plastic- on the sea surface was rarely high enough to generate a detectable signal from space. However, using supercomputers and advanced search algorithms, the research team has demonstrated that satellites are an effective tool for estimating the amount of litter in the sea.

To carry out the work, funded by the European Space Agency (ESA), a six-year historical series of observations from the European Copernicus Sentinel-2 satellite in the Mediterranean Sea were analysed. In total, 300,000 images taken every 3 days at a resolution of 10 metres were scrutinised. The results reveal large aggregations of litter within floating structures scientifically known as ‘windrows’ that can be up to several kilometres long and result from the convergence of ocean currents and the effect of wind on the sea surface.

Although the satellite's sensors were not specifically designed to detect litter, their ability to identify plastic made it possible to map the most polluted areas in the Mediterranean. This map shows the main entry points for litter from the mainland and improves our understanding of the mechanisms that transport debris. The results indicate that the amount of floating plastic in the Mediterranean could cover an area of approximately 95 square kilometres over the period 2015-2021, which is equivalent to about 7,500 football pitches.

‘Until now, looking for aggregations of litter several metres in diameter on the ocean surface was like looking for needles in a haystack, as the formation of windrows requires the presence of a large amount of litter and little wind to prevent it from spreading,’ explains Manuel Arias (ICM-CSIC), one of the co-directors of the study.

From his side, Andrés Cózar, from the University of Cádiz, also co-director of the study, stresses that ‘the relevance and significance of the trails in terms of marine litter was unknown until now’, and welcomes the fact that automation through supercomputers and advanced search algorithms has made it possible to prove that it is possible to monitor the accumulation of marine litter from space over large areas and on a routine basis".

With an eye to future space missions, the research team suggests installing specific plastic detection sensors on satellites. According to the study, this would increase the ability to detect plastic in the ocean by a factor of 20. In addition, this information could be compared with other environmental factors to improve understanding of the mechanisms that transport plastic debris from land to sea, and better guide actions and regulations to combat this form of marine pollution that affects biodiversity, fish stocks and tourism.

Population density, a key factor

The study concludes that factors such as population density, geography and rainfall patterns have a significant influence on the accumulation of marine litter. For example, desert countries or cities contribute much less to the problem, while in areas with more rainfall, especially when torrential rains occur, the accumulation of litter resulting from emissions in the preceding days and weeks is much higher.

Finally, the study reveals that, in its majority, litter of continental origin is confined to the first 15 kilometres of sea from the coast, returning to the coast after a few days or months. ‘This confirms the notion that the distribution of plastic litter of continental origin and that generated by human activities directly in the sea behave and distribute differently,’ Arias explains.

The authors of the study illustrate the applicability of the new methodology with several real cases, such as the evaluation of the effectiveness of action plans against litter in the Tiber River in Rome (Italy), the identification of pollution hotspots related to maritime transport in the Suez Canal (Egypt) or the use of satellite observations to guide clean-up tasks in the waters of the Bay of Biscay (Spain).

Nevertheless, the study results show that satellite-based monitoring of marine pollution is feasible and promising for issues beyond plastic. For example, a sensor specifically dedicated to the detection and identification of floating objects could help address problems such as loss of cargo on ships, oil spills or search and rescue tasks at sea.

In addition to the University of Cadiz and the ICM-CSIC, the team is made up of researchers from the European Space Agency (ESA), ARGANS France, the Universitat Politècnica de Catalunya (Spain), the Consiglio Nazionale delle Ricerche (ISMAR-CNR, Italy), the Technical University of Crete (Greece), ARGANS Ltd. (UK), AIRBUS Defence and Space (France), the Joint Research Centre (JRC) of the European Commission, The Ocean Cleanup (The Netherlands), and ACRI-ST (France).

Cosmic leap: NASA swift satellite and AI unravel the distance of the farthest gamma-ray bursts



THE GRADUATE UNIVERSITY FOR ADVANCED STUDIES, SOKENDAI
Determining the Distance of Gamma-Ray Bursts with Machine Learning 

IMAGE: 

THIS ILLUSTRATION DEPICTS THE PROCESS OF DETECTING GAMMA-RAY BURSTS (GRBS) USING THE SWIFT OBSERVATORY AND ANALYZING THEIR EMISSIONS ON EARTH THROUGH ADVANCED MACHINE-LEARNING TECHNIQUES. THIS CUTTING-EDGE APPROACH ENABLES SCIENTISTS TO DETERMINE THE DISTANCES (REDSHIFT) OF THESE COSMIC PHENOMENA FOR WHICH THE DISTANCE IS UNKNOWN, HELPING UNRAVEL THE MYSTERIES OF THE UNIVERSE.

view more 

CREDIT: NASA, ADITYA NARENDRA, MARIA GIOVANNA DAINOTTI, AND AGNIESZKA POLLO




The advent of AI has been hailed by many as a societal game-changer, as it opens a universe of possibilities to improve nearly every aspect of our lives.

Astronomers are now using AI, quite literally, to measure the expansion of our universe.

Two recent studies led by Maria Dainotti, a visiting professor with UNLV’s Nevada Center for Astrophysics and assistant professor at the National Astronomical Observatory of Japan (NAOJ), incorporated multiple machine learning models to add a new level of precision to distance measurements for gamma-ray bursts (GRBs) – the most luminous and violent explosions in the universe.

In just a few seconds, GRBs release the same amount of energy our sun releases in its entire lifetime. Because they are so bright, GRBs can be observed at multiple distances – including at the edge of the visible universe – and aid astronomers in their quest to chase the oldest and most distant stars. But, due to the limits of current technology, only a small percentage of known GRBs have all of the observational characteristics needed to aid astronomers in calculating how far away they occurred.

Dainotti and her teams combined GRB data from NASA’s Neil Gehrels Swift Observatory with multiple machine learning models to overcome the limitations of current observational technology and more precisely estimate the proximity of GRBs for which the distance is unknown. Because GRBs can be observed both far away and at relatively close distances, knowing where they occurred can help scientists understand how stars evolve over time and how many GRBs can occur in a given space and time.

“This research pushes forward the frontier in both gamma-ray astronomy and machine learning,” said Dainotti. “Follow-up research and innovation will help us achieve even more reliable results and enable us to answer some of the most pressing cosmological questions, including the earliest processes of our universe and how it has evolved over time.”

AI Boosts Limits of Deep-Space Observation

In one study, Dainotti and Aditya Narendra, a final-year doctoral student at Poland’s Jagiellonian University, used several machine learning methods to precisely measure the distance of GRBs observed by the space Swift UltraViolet/Optical Telescope (UVOT) and ground-based telescopes, including the Subaru Telescope. The measurements were based solely on other, non distance-related GRB properties. The research was published Feb. 8 on the preprint server arXiv.

“The outcome of this study is so precise that we can determine using predicted distance the number of GRBs in a given volume and time (called the rate), which is very close to the actual observed estimates,” said Narendra.

Another study led by Dainotti and international collaborators has been successful in measuring GRB distance with machine learning using data by NASA’s Swift X-ray Telescope (XRT) afterglows from what are known as long GRBs. GRBs are believed to occur in different ways. Long GRBs happen when a massive star reaches the end of its life and explodes in a spectacular supernova. Another type, known as short GRBs, happen when the remnants of dead stars, such as neutron stars, merge gravitationally and collide with each other.

The novelty of this approach, Dainotti says, comes from using several machine-learning methods together to improve their collective predictive power. This method, called Superlearner, assigns to each algorithm a weight whose values range from 0 to 1, with each weight corresponding to the predictive power of that singular method.

“The advantage of the Superlearner is that the final prediction is always more performant than the singular models,” said Dainotti. “Superlearner is also used to discard the algorithms which are the least predictive.”

This study, which was published Feb. 26 in The Astrophysical Journal, Supplement Series, reliably estimates the distance of 154 long GRBs for which the distance is unknown and significantly boosts the population of known distances among this type of burst.

Answering Puzzling Questions on GRB Formation

A third study, published Feb. 21 in the Astrophysical Journal Letters and led by Stanford University astrophysicist Vahé Petrosian and Dainotti, used Swift X-ray data to answer puzzling questions by showing that the GRB rate – at least at small relative distances – does not follow the rate of star formation.

“This opens the possibility that long GRBs at small distances may be generated not by a collapse of massive stars, but rather by the fusion of very dense objects like neutron stars,” said Petrosian.

With support from NASA’s Swift Observatory Guest Investigator program (Cycle 19), Dainotti and her colleagues are now working to make the machine learning tools publicly available through an interactive web application.

Mysterious mini-Neptunes



NATIONAL INSTITUTES OF NATURAL SCIENCES
Mini-Neptunes with an elliptical orbits 

IMAGE: 

DIAGRAM OF DISCOVERED EXOPLANET ORBITS. THE ORBITS OF EXOPLANETS CLOSE TO THEIR PARENT STARS TEND TO BECOME CIRCULAR OVER TIME, BUT THREE OF THE NEWLY DISCOVERED EXOPLANETS, EXCEPT THE BOTTOM LEFT, HAVE MAINTAINED ELLIPTICAL ORBITS DESPITE BEING OVER A BILLION YEARS OLD.

view more 

CREDIT: ASTROBIOLOGY CENTER




This study discovered mini-Neptunes around four red dwarfs using observations from a global network of ground-based telescopes and the TESS space telescope. These four mini-Neptunes are close to their parent stars, and the three of them are likely to be in eccentric orbits.

Planets between the size of Earth and Uranus/Neptune, known as mini-Neptunes, are not found in our Solar System. However, mini-Neptunes are relatively common outside the Solar System and are promising targets for atmospheric characterization by the James Webb Space Telescope. What do mini-Neptunes look like?

This study discovered four transiting short-period mini-Neptunes (TOI-782 b, TOI-1448 b, TOI-2120 b, and TOI-2406 b) orbiting red dwarfs through follow-up observations with ground-based telescopes with MuSCATs (a series of Multicolor Simultaneous Camera for studying Atmospheres of Transiting exoplanets). These mini-Neptunes have radii about 2-3 times that of Earth and orbital periods of less than eight days. In addition, these radial velocity measurements of their parent stars, obtained with the IRD (InfraRed Doppler) on the Subaru telescope, indicate that the upper limit on the masses of these four planets is less than 20 times the mass of Earth. The relationship between the measured radii and the upper mass limits of these mini-Neptunes suggests that they are not rocky planets like Earth. Their interiors likely contain volatiles such as icy materials like H2O and atmospheres. 

    The team also found that at least three (TOI-782 b, TOI-2120 b, TOI-2406 b) of these four mini-Neptunes are likely to be in eccentric orbits. In general, the orbit of a short-period planet around a red dwarf should be circular due to tidal dissipation. However, three short-period mini-Neptunes around red dwarfs have maintained non-zero eccentricities for billions of years. One possible interpretation of this is that their interiors are not susceptible to tidal effects. The mass-radius relationship of these four mini-Neptunes suggests that they are not rocky planets. Thus, the interiors of these mysterious mini-Neptunes may be similar to those of Neptune. Short-period mini-Neptunes are promising targets for atmospheric observations with the James Webb Space Telescope. Further detailed follow-up observations are expected to improve our understanding of the internal compositions and atmospheres of short-period mini-Neptunes.

 

No comments:

Post a Comment