KREUZADER (Posts tagged astronomy)

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The possible disappearance of a massive star in the low-metallicity galaxy PHL 293B We investigate a suspected very massive star in one of the most metal-poor dwarf galaxies, PHL 293B. Excitingly, we find the sudden disappearance of the stellar...

The possible disappearance of a massive star in the low-metallicity galaxy PHL 293B

We investigate a suspected very massive star in one of the most metal-poor dwarf galaxies, PHL 293B. Excitingly, we find the sudden disappearance of the stellar signatures from our 2019 spectra, in particular the broad H lines with P Cygni profiles that have been associated with a massive luminous blue variable (LBV) star. Such features are absent from our spectra obtained in 2019 with the Echelle Spectrograph for Rocky Exoplanet- and Stable Spectroscopic Observation and X-shooter instruments of the European Southern Observatory’s Very Large Telescope. We compute radiative transfer models using cmfgen, which fit the observed spectrum of the LBV and are consistent with ground-based and archival Hubble Space Telescope photometry. Our models show that during 2001–2011, the LBV had a luminosity L* = 2.5–3.5 × 106 L⊙, a mass-loss rate M˙=0.005−0.020 M⊙ yr−1, a wind velocity of 1000 km s−1, and effective and stellar temperatures of Teff = 6000–6800 and T* = 9500–15 000 K. These stellar properties indicate an eruptive state. We consider two main hypotheses for the absence of the broad emission components from the spectra obtained since 2011. One possibility is that we are seeing the end of an LBV eruption of a surviving star, with a mild drop in luminosity, a shift to hotter effective temperatures, and some dust obscuration. Alternatively, the LBV could have collapsed to a massive black hole without the production of a bright supernova.

Source: academic.oup.com
astronomy space
Why boring could be good for this star’s two intriguing planets Astronomers have discovered two planets a little more massive than Earth orbiting a nearby star. Unlike many other stars hosting planetary systems, this one is relatively inactive — so...

Why boring could be good for this star’s two intriguing planets

Astronomers have discovered two planets a little more massive than Earth orbiting a nearby star. Unlike many other stars hosting planetary systems, this one is relatively inactive — so it doesn’t emit flares of energy that could hurt the chances of life existing on the planets.

“It’s the best star in close proximity to the Sun to understand whether its planets have atmospheres and whether they have life,” says Sandra Jeffers, an astronomer at Göttingen University in Germany who led the discovery team. The finding was published on 25 June in Science1.

The star, called GJ 887, is just under 3.3 parsecs (10.7 light years) from Earth, in the constellation Piscis Austrinus. It is the brightest red-dwarf star visible from Earth.

Red dwarfs are smaller and cooler than the Sun, and many have planets orbiting them. But most are very active, with magnetic energy roiling their surface and releasing floods of charged particles into space during eruptions known as stellar flares. Many famous planetary systems orbit active red-dwarf stars, such as Proxima Centauri, the closest star to the Sun, and TRAPPIST-1, which has seven Earth-sized worlds. Astronomers say the planets in these systems might not be able to support life, because their stars constantly blast them with powerful radiation.

By contrast, planets in the newfound system could survive relatively unscathed. “GJ 887 is exciting because the central star is so quiet,” says Jeffers. “That’s the exceptional part.”

Source: nature.com
astronomy space
A black hole with a puzzling companion The harvest of exceptional gravitational-wave events from LIGO’s and Virgo’s third observing run (O3) grows. A new signal published today comes from the merger of a 23-solar-mass black hole with an object 9...

A black hole with a puzzling companion

The harvest of exceptional gravitational-wave events from LIGO’s and Virgo’s third observing run (O3) grows. A new signal published today comes from the merger of a 23-solar-mass black hole with an object 9 times lighter. The second object is mysterious: its measured mass puts it in the so-called “mass gap” between the heaviest known neutron stars and the lightest known black holes. While the researchers cannot be sure about its true nature, one thing is clear: the observation of this unusual pair challenges the current understanding of how such systems are born and evolve.

Source: aei.mpg.de
gravitational astronomy astrophysics astronomy space
CfA Scientists Collaborate on New Study to Search the Universe for Signs of Technological Civilizations Harvard & Smithsonian and the University of Rochester are collaborating on a project to search the universe for signs of life via...

CfA Scientists Collaborate on New Study to Search the Universe for Signs of Technological Civilizations

Harvard & Smithsonian and the University of Rochester are collaborating on a project to search the universe for signs of life via technosignatures, after receiving the first NASA non-radio technosignatures grant ever awarded, and the first SETI-specific NASA grant in over three decades.

Researchers believe that although life appears in many forms, the scientific principles remain the same, and that the technosignatures identifiable on Earth will also be identifiable in some fashion outside of the solar system. “Technosignatures relate to signatures of advanced alien technologies similar to, or perhaps more sophisticated than, what we possess,” said Avi Loeb, Frank B. Baird Jr. Professor of Science at Harvard. “Such signatures might include industrial pollution of atmospheres, city lights, photovoltaic cells (solar panels), megastructures, or swarms of satellites.”

Knowing where to look for technosignatures hasn’t always been easy, making it difficult for researchers to obtain grants and a footing in mainstream astronomy. The surge of results in exoplanetary research—including planets in habitable zones and the presence of atmospheric water vapor—over the past five years has revitalized the search for intelligent life. “The Search for Extraterrestrial Intelligence (SETI) has always faced the challenge of figuring out where to look. Which stars do you point your telescope at and look for signals?” said Adam Frank, a professor of physics and astronomy at the University of Rochester, and the primary recipient of the grant. “Now we know where to look. We have thousands of exoplanets including planets in the habitable zone where life can form. The game has changed.”

The study, “Characterizing Atmospheric Technosignatures,” will initially focus on searching for two particular signatures that may indicate the presence of technological activities on extrasolar planetary bodies: solar panels and pollutants.

Source: cfa.harvard.edu
seti astronomy
Astronomers detect regular rhythm of radio waves, with origins unknown A team of astronomers, including researchers at MIT, has picked up on a curious, repeating rhythm of fast radio bursts emanating from an unknown source outside our galaxy, 500...

Astronomers detect regular rhythm of radio waves, with origins unknown

A team of astronomers, including researchers at MIT, has picked up on a curious, repeating rhythm of fast radio bursts emanating from an unknown source outside our galaxy, 500 million light years away.

Fast radio bursts, or FRBs, are short, intense flashes of radio waves that are thought to be the product of small, distant, extremely dense objects, though exactly what those objects might be is a longstanding mystery in astrophysics. FRBs typically last a few milliseconds, during which time they can outshine entire galaxies.

Source: news.mit.edu
astronomy radio astronomy
NASA’s New Horizons Conducts the First Interstellar Parallax Experiment For the first time, a spacecraft has sent back pictures of the sky from so far away that some stars appear to be in different positions than we see from Earth. More than four...

NASA’s New Horizons Conducts the First Interstellar Parallax Experiment

For the first time, a spacecraft has sent back pictures of the sky from so far away that some stars appear to be in different positions than we see from Earth.

More than four billion miles from home and speeding toward interstellar space, NASA’s New Horizons has traveled so far that it now has a unique view of the nearest stars. “It’s fair to say that New Horizons is looking at an alien sky, unlike what we see from Earth,” said Alan Stern, New Horizons principal investigator from Southwest Research Institute (SwRI) in Boulder, Colorado. “And that has allowed us to do something that had never been accomplished before — to see the nearest stars visibly displaced on the sky from the positions we see them on Earth.”

On April 22-23, the spacecraft turned its long-range telescopic camera to a pair of the closest stars, Proxima Centauri and Wolf 359, showing just how they appear in different places than we see from Earth. Scientists have long used this “parallax effect” – how a star appears to shift against its background when seen from different locations – to measure distances to stars.

Source: pluto.jhuapl.edu
nasa space astronomy new horizons proxima centauri brian may
K-State study finds that patterns formed by spiral galaxies show that the universe may have a defined structure, and that the early universe could have been spinning An analysis of more than 200,000 spiral galaxies has revealed unexpected links...

K-State study finds that patterns formed by spiral galaxies show that the universe may have a defined structure, and that the early universe could have been spinning

An analysis of more than 200,000 spiral galaxies has revealed unexpected links between spin directions of galaxies, and the structure formed by these links might suggest that the early universe could have been spinning, according to a Kansas State University study.

Lior Shamir, a K-State computational astronomer and computer scientist, presented the findings at the 236th American Astronomical Society meeting in June 2020. The findings are significant because the observations conflict with some previous assumptions about the large-scale structure of the universe.  

Source: k-state.edu
astronomy space cosmology
ESO Telescope Sees Signs of Planet Birth Observations made with the European Southern Observatory’s Very Large Telescope (ESO’s VLT) have revealed the telltale signs of a star system being born. Around the young star AB Aurigae lies a dense disc of...

ESO Telescope Sees Signs of Planet Birth

Observations made with the European Southern Observatory’s Very Large Telescope (ESO’s VLT) have revealed the telltale signs of a star system being born. Around the young star AB Aurigae lies a dense disc of dust and gas in which astronomers have spotted a prominent spiral structure with a ‘twist’ that marks the site where a planet may be forming. The observed feature could be the first direct evidence of a baby planet coming into existence.

Source: eso.org
astronomy european southern observatory space
ESO Instrument Finds Closest Black Hole to Earth A team of astronomers from the European Southern Observatory (ESO) and other institutes has discovered a black hole lying just 1000 light-years from Earth. The black hole is closer to our Solar System...

ESO Instrument Finds Closest Black Hole to Earth

A team of astronomers from the European Southern Observatory (ESO) and other institutes has discovered a black hole lying just 1000 light-years from Earth. The black hole is closer to our Solar System than any other found to date and forms part of a triple system that can be seen with the naked eye. The team found evidence for the invisible object by tracking its two companion stars using the MPG/ESO 2.2-metre telescope at ESO’s La Silla Observatory in Chile. They say this system could just be the tip of the iceberg, as many more similar black holes could be found in the future.

Source: eso.org
space astronomy european southern observatory black hole
Fast radio bursts could be far-flung magnetars, new evidence suggests In recent years, enigmatic events called Fast radio bursts (FRBs) have captivated radio astronomers. These brief but incredibly bright radio pulses last only a fraction of a...

Fast radio bursts could be far-flung magnetars, new evidence suggests

In recent years, enigmatic events called Fast radio bursts (FRBs) have captivated radio astronomers. These brief but incredibly bright radio pulses last only a fraction of a second, yet they’ve been found in distant galaxies across the universe. And although the discovery of the first FRB in 2007 caught researchers somewhat flat-footed, it ultimately led to many theories about what drives these strange pulses. There’s a problem, however: Astronomers have only seen FRB-like events in distant galaxies, which makes them hard to study in detail.

That seems to have changed last week.  

On April 28, two radio telescopes spotted a new FRB-like pulse originating from a flaring magnetar located some 30,000 light-years away, putting it firmly within the Milky Way. And just a few days later, they detected another burst from the same nearby object.

With the detection of these events, astronomers are optimistic they’ve spotted a nearby example of a possible source of distant FRBs. Namely, highly magnetic neutron stars.

Source: astronomy.com
radio astronomy astronomy space