Category Archives: Astronomy

ESO: Star orbiting supermassive black hole follows path predicted by Einstein

The latest ESO (European Southern Observatory) report:

ESO Telescope Sees Star Dance Around Supermassive Black Hole,
Proves Einstein Right

Observations made with ESO’s Very Large Telescope (VLT) have revealed for the first time that a star orbiting the supermassive black hole at the centre of the Milky Way moves just as predicted by Einstein’s theory of general relativity. Its orbit is shaped like a rosette and not like an ellipse as predicted by Newton’s theory of gravity. This effect, known as Schwarzschild precession, had never before been measured for a star around a supermassive black hole. This artist’s impression illustrates the precession of the star’s orbit, with the effect exaggerated for easier visualisation.

Observations made with ESO’s Very Large Telescope (VLT) have revealed for the first time that a star orbiting the supermassive black hole at the centre of the Milky Way moves just as predicted by Einstein’s general theory of relativity. Its orbit is shaped like a rosette and not like an ellipse as predicted by Newton’s theory of gravity. This long-sought-after result was made possible by increasingly precise measurements over nearly 30 years, which have enabled scientists to unlock the mysteries of the behemoth lurking at the heart of our galaxy.

“Einstein’s General Relativity predicts that bound orbits of one object around another are not closed, as in Newtonian Gravity, but precess forwards in the plane of motion. This famous effect — first seen in the orbit of the planet Mercury around the Sun — was the first evidence in favour of General Relativity. One hundred years later we have now detected the same effect in the motion of a star orbiting the compact radio source Sagittarius A* at the centre of the Milky Way. This observational breakthrough strengthens the evidence that Sagittarius A* must be a supermassive black hole of 4 million times the mass of the Sun,”

says Reinhard Genzel, Director at the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany and the architect of the 30-year-long programme that led to this result.

Located 26 000 light-years from the Sun, Sagittarius A* and the dense cluster of stars around it provide a unique laboratory for testing physics in an otherwise unexplored and extreme regime of gravity. One of these stars, S2, sweeps in towards the supermassive black hole to a closest distance less than 20 billion kilometres (one hundred and twenty times the distance between the Sun and Earth), making it one of the closest stars ever found in orbit around the massive giant. At its closest approach to the black hole, S2 is hurtling through space at almost three percent of the speed of light, completing an orbit once every 16 years.

“After following the star in its orbit for over two and a half decades, our exquisite measurements robustly detect S2’s Schwarzschild precession in its path around Sagittarius A*,”

says Stefan Gillessen of the MPE, who led the analysis of the measurements published today in the journal Astronomy & Astrophysics.

Most stars and planets have a non-circular orbit and therefore move closer to and further away from the object they are rotating around. S2’s orbit precesses, meaning that the location of its closest point to the supermassive black hole changes with each turn, such that the next orbit is rotated with regard to the previous one, creating a rosette shape. General Relativity provides a precise prediction of how much its orbit changes and the latest measurements from this research exactly match the theory. This effect, known as Schwarzschild precession, had never before been measured for a star around a supermassive black hole.

This simulation shows the orbits of stars very close to the supermassive black hole at the heart of the Milky Way. One of these stars, named S2, orbits every 16 years and is passing very close to the black hole in May 2018. This is a perfect laboratory to test gravitational physics and specifically Einstein’s general theory of relativity. Research into S2’s orbit was presented in a paper entitled “Detection of the Gravitational Redshift in the Orbit of the Star S2 near the Galactic Centre Massive Black Hole“, by the GRAVITY Collaboration, which appeared in the journal Astronomy & Astrophysics on 26 July 2018.

The study with ESO’s VLT also helps scientists learn more about the vicinity of the supermassive black hole at the centre of our galaxy.

“Because the S2 measurements follow General Relativity so well, we can set stringent limits on how much invisible material, such as distributed dark matter or possible smaller black holes, is present around Sagittarius A*. This is of great interest for understanding the formation and evolution of supermassive black holes,”

say Guy Perrin and Karine Perraut, the French lead scientists of the project.

This result is the culmination of 27 years of observations of the S2 star using, for the best part of this time, a fleet of instruments at ESO’s VLT, located in the Atacama Desert in Chile. The number of data points marking the star’s position and velocity attests to the thoroughness and accuracy of the new research: the team made over 330 measurements in total, using the GRAVITY, SINFONI and NACO instruments. Because S2 takes years to orbit the supermassive black hole, it was crucial to follow the star for close to three decades, to unravel the intricacies of its orbital movement.

The research was conducted by an international team led by Frank Eisenhauer of the MPE with collaborators from France, Portugal, Germany and ESO. The team make up the GRAVITY collaboration, named after the instrument they developed for the VLT Interferometer, which combines the light of all four 8-metre VLT telescopes into a super-telescope (with a resolution equivalent to that of a telescope 130 metres in diameter). The same team reported in 2018 another effect predicted by General Relativity: they saw the light received from S2 being stretched to longer wavelengths as the star passed close to Sagittarius A*.

“Our previous result has shown that the light emitted from the star experiences General Relativity. Now we have shown that the star itself senses the effects of General Relativity,”

says Paulo Garcia, a researcher at Portugal’s Centre for Astrophysics and Gravitation and one of the lead scientists of the GRAVITY project.

With ESO’s upcoming Extremely Large Telescope, the team believes that they would be able to see much fainter stars orbiting even closer to the supermassive black hole.

“If we are lucky, we might capture stars close enough that they actually feel the rotation, the spin, of the black hole,”

says Andreas Eckart from Cologne University, another of the lead scientists of the project. This would mean astronomers would be able to measure the two quantities, spin and mass, that characterise Sagittarius A* and define space and time around it.

“That would be again a completely different level of testing relativity,” says Eckart.

Links

=== Amazon Ad ===

The Planet Factory:
Exoplanets and the Search for a Second Earth

Carnival of Space #657 – NextBigFuture.com

NextBigFuture.com hosts the latest Carnival of Space.

Analysis of the images of black holes will provide characterization of the rings of photons surrounding them, which in turn will produce information about the black holes themselves . Credits: CFA via Universe Today and Carnival of Space

=== Amazon Ad ===

More Things in the Heavens:
How Infrared Astronomy Is Expanding Our View of the Universe

 

Videos: Night sky highlights for April 2020

** What’s Up: April 2020 Skywatching Tips from NASANASA JPL

What are some astronomy highlights in the sky in April 2020? This month, Venus visits the Pleiades; Mars, Jupiter and Saturn begin their breakup; and we ask, “What is the Moon illusion?” Additional information about topics covered in this episode of What’s Up, along with still images from the video, and the video transcript, are available at https://solarsystem.nasa.gov/whats-up…

** Tonight’s Sky: AprilSpace Telescope Science Institute

Clear April nights are filled with starry creatures. Near the Big Dipper, you will find several interesting binary stars. You can also spot galaxies like the Pinwheel Galaxy, M82, and M96—the last of which is an asymmetric galaxy that may have been gravitationally disrupted by encounters with its neighbors. Keep watching for space-based views of these celestial objects.

** What’s in the Night Sky April 2020Alyn Wallace

** What to see in the night sky: April 2020BBC Sky at Night Magazine

Pete Lawrence and Paul Abel guide us through April’s stargazing highlights.

=== Amazon Ad ===

The Planet Factory:
Exoplanets and the Search for a Second Earth

The Space Show this week – Mar.30.2020

The guests and topics of discussion on The Space Show this week:

1. Monday, March 30, 2020; 7 pm PDT (9 pm CDT, 10 pm EDT: No special programming.

2. Tuesday, March 31, 2020; 7 pm PDT (9 pm CDT, 10 pm EDT): Author Rod Pyle will talk about his latest commercial space work and more.

3. Wednesday, April 1, 2020: Hotel Mars TBA pre-recorded. See upcoming show menu on the home page for program details.

4. Thursday, April 2, 2020; 7-8:30 pm PDT (9-10:30 pm CDT, 10-11:30 pm EDT): No special programming.

5. Friday, April 3, 2020; 9:30-11 am PDT (11:30 am-1 pm CDT, 12:30-2 pm EDT): We welcome back Dr. David Kipping to discuss his work on the Earth as a telescope concept

6. Sunday, April 5, 2020; 12-1:30 pm PDT (3-4:30 pm EDT, 2-3:30 pm CDT): We welcome back Dennis Wingo to talk about his recent SLS history post and more.

Some recent shows:

** Sun, 03/29/2020 Dr. Paul Jaffe of the US Naval Research Laboratory (NRL) discussed space solar power.

** Fri, 03/27/2020Dr. Tina Highfill discussed “the BEA satellite economic analysis of the space industry”.

** Tue, 03/24/2020Robert Zimmerman talked about “multiple topics including SpaceX, SLS, COVID19 and more”.

** See also:
* The Space Show Archives
* The Space Show Newsletter
* The Space Show Shop

The Space Show is a project of the One Giant Leap Foundation.

The Space Show - David Livingston
The Space Show – David Livingston

== Amazon Ad ==

Moon Rush: The New Space Race

ESO: On exoplanet WASP-76b it rains metal cats and dogs

A new report from ESO (European Southern Observatory):

ESO Telescope Observes Exoplanet Where It Rains Iron

This illustration shows a night-side view of the exoplanet WASP-76b. The ultra-hot giant exoplanet has a day side where temperatures climb above 2400 degrees Celsius, high enough to vaporise metals. Strong winds carry iron vapour to the cooler night side where it condenses into iron droplets. To the left of the image, we see the evening border of the exoplanet, where it transitions from day to night.

Researchers using ESO’s Very Large Telescope (VLT) have observed an extreme planet where they suspect it rains iron. The ultra-hot giant exoplanet has a day side where temperatures climb above 2400 degrees Celsius, high enough to vaporise metals. Strong winds carry iron vapour to the cooler night side where it condenses into iron droplets.

One could say that this planet gets rainy in the evening, except it rains iron,

says David Ehrenreich, a professor at the University of Geneva in Switzerland. He led a study, published today in the journal Nature, of this exotic exoplanet. Known as WASP-76b, it is located some 390 light-years away in the constellation of Pisces.

This strange phenomenon happens because the ‘iron rain’ planet only ever shows one face, its day side, to its parent star, its cooler night side remaining in perpetual darkness. Like the Moon on its orbit around the Earth, WASP-76b is ‘tidally locked’: it takes as long to rotate around its axis as it does to go around the star.

On its day side, it receives thousands of times more radiation from its parent star than the Earth does from the Sun. It’s so hot that molecules separate into atoms, and metals like iron evaporate into the atmosphere. The extreme temperature difference between the day and night sides results in vigorous winds that bring the iron vapour from the ultra-hot day side to the cooler night side, where temperatures decrease to around 1500 degrees Celsius.

Not only does WASP-76b have different day-night temperatures, it also has distinct day-night chemistry, according to the new study. Using the new ESPRESSO instrument on ESO’s VLT in the Chilean Atacama Desert, the astronomers identified for the first time chemical variations on an ultra-hot gas giant planet. They detected a strong signature of iron vapour at the evening border that separates the planet’s day side from its night side.

Surprisingly, however, we do not see the iron vapour in the morning,

says Ehrenreich. The reason, he says, is that

it is raining iron on the night side of this extreme exoplanet.

[María Rosa Zapatero Osorio, an astrophysicist at the Centre for Astrobiology in Madrid, Spain, and the chair of the ESPRESSO science team, adds,]

The observations show that iron vapour is abundant in the atmosphere of the hot day side of WASP-76b

A fraction of this iron is injected into the night side owing to the planet’s rotation and atmospheric winds. There, the iron encounters much cooler environments, condenses and rains down.

This result was obtained from the very first science observations done with ESPRESSO, in September 2018, by the scientific consortium who built the instrument: a team from Portugal, Italy, Switzerland, Spain and ESO.

ESPRESSO — the Echelle SPectrograph for Rocky Exoplanets and Stable Spectroscopic Observations — was originally designed to hunt for Earth-like planets around Sun-like stars. However, it has proven to be much more versatile.

We soon realised that the remarkable collecting power of the VLT and the extreme stability of ESPRESSO made it a prime machine to study exoplanet atmospheres,

says Pedro Figueira, ESPRESSO instrument scientist at ESO in Chile.

What we have now is a whole new way to trace the climate of the most extreme exoplanets,”

concludes Ehrenreich.

This comic-book-style illustration by Swiss graphic novelist Frederik Peeters shows a close-up view of the evening border of the exoplanet WASP-76b. The ultra-hot giant exoplanet has a day side where temperatures climb above 2400 degrees Celsius, high enough to vaporise metals. Strong winds carry iron vapour to the cooler night side where it condenses into iron droplets. Theoretical studies show that a planet, like WASP-76b, with an extremely hot day side and colder night side would have a gigantic condensation front in the form of a cloud cascade at its evening border, the transition from day to night, as depicted here.

Links

=== Amazon Ad ===

More Things in the Heavens:
How Infrared Astronomy Is Expanding Our View of the Universe