Here is the latest ESO (European Southern Observatory) report:

Successful First Observations of Galactic Centre with GRAVITY
Black hole probe now working with the four VLT Unit Telescopes

eso1622a[1] — This artist’s impression shows stars orbiting the supermassive black hole at the centre of the Milky Way. In 2018 one of these stars, S2, will pass very close to the black hole and this event will be the best opportunity to study the effects of very strong gravity and test the predictions of Einstein’s general relativity in the near future. The GRAVITY instrument on the ESO Very Large Telescope Interferometer is the most powerful tool for measuring the positions of these stars in existence and it was successfully tested on the S2 star in the summer of 2016. The orbit of S2 is shown in red and the position of the central black hole is marked with a red cross. Credit: ESO/L. Calçada

A European team of astronomers have used the new GRAVITY instrument at ESO’s Very Large Telescope to obtain exciting observations of the centre of the Milky Way by combining light from all four of the 8.2-metre Unit Telescopes for the first time. These results provide a taste of the groundbreaking science that GRAVITY will produce as it probes the extremely strong gravitational fields close to the central supermassive black hole and tests Einstein’s general relativity.

The GRAVITY instrument is now operating with the four 8.2-metre Unit Telescopes of ESO’s Very Large Telescope (VLT), and even from early test results it is already clear that it will soon be producing world-class science.

eso1622b[1] — Image of the galactic centre. For the interferometric GRAVITY observations the star IRS 16C was used as a reference star, the actual target was the star S2. The position of the centre, which harbours the (invisible) black hole known as Sgr A*,with 4 million solar masses, is marked by the orange cross. Credit: ESO/MPE/S. Gillessen et al.

GRAVITY is part of the VLT Interferometer. By combining light from the four telescopes it can achieve the same spatial resolution and precision in measuring positions as a telescope of up to 130 metres in diameter. The corresponding gains in resolving power and positional accuracy — a factor of 15 over the individual 8.2-metre VLT Unit Telescopes — will enable GRAVITY to make amazingly accurate measurements of astronomical objects.

One of GRAVITY’s primary goals is to make detailed observations of the surroundings of the 4 million solar mass black hole at the very centre of the Milky Way [1]. Although the position and mass of the black hole have been known since 2002, by making precision measurements of the motions of stars orbiting it, GRAVITY will allow astronomers to probe the gravitational field around the black hole in unprecedented detail, providing a unique test of Einstein’s general theory of relativity.

This artist’s impression shows the orbits of stars around supermassive black hole at the centre of the Milky Way. In 2018 one of these stars, S2, will pass very close to the black hole and present the best opportunity to study the effects of very strong gravity and test the predictions of Einstein’s general relativity in the near future.

The GRAVITY instrument on the ESO Very Large Telescope Interferometer is the most powerful tool for measuring the positions of the S2 star in existence and it was successfully tested on the S2 star in summer 2016. The orbit of S2 is highlighted in red and the position of the central black hole is marked with a red cross. Credit: ESO/L. Calçada

In this regard, the first observations with GRAVITY are already very exciting. The GRAVITY team [2] has used the instrument to observe a star known as S2 as it orbits the black hole at the centre of our galaxy with a period of only 16 years. These tests have impressively demonstrated GRAVITY’s sensitivity as it was able to see this faint star in just a few minutes of observation.

Animation of the path that an incoming light ray traces through the GRAVITY instrument. Note the intricate design and complex interaction of the various components for the four telescopes. For interferometry to work, the light paths have to be superposed with a precision of a fraction of the wavelength – less than 1 micrometer. Credit: MPE

The team will soon be able to obtain ultra-precise positions of the orbiting star, equivalent to measuring the position of an object on the Moon with centimetre precision. That will enable them to determine whether the motion around the black hole follows the predictions of Einstein’s general relativity — or not. The new observations show that the Galactic Centre is as ideal a laboratory as one can hope for.

“It was a fantastic moment for the whole team when the light from the star interfered for the first time — after eight years of hard work,” says GRAVITY’s lead scientist Frank Eisenhauer from the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. “First we actively stabilised the interference on a bright nearby star, and then only a few minutes later we could really see the interference from the faint star — to a lot of high-fives.” At first glance neither the reference star nor the orbiting star have massive companions that would complicate the observations and analysis. “They are ideal probes,”explains Eisenhauer.

This early indication of success does not come a moment too soon. In 2018 the S2 star will be at its closest to the black hole, just 17 light-hours away from it and travelling at almost 30 million kilometres per hour, or 2.5% of the speed of light. At this distance the effects due to general relativity will be most pronounced and GRAVITY observations will yield their most important results [3]. This opportunity will not be repeated for another 16 years.

Notes

[1] The centre of the Milky Way, our home galaxy, lies on the sky in the constellation of Sagittarius (The Archer) and is some 25 000 light-years distant from Earth.

[2] The GRAVITY consortium consists of: the Max Planck Institutes for Extraterrestrial Physics (MPE) and Astronomy (MPIA), LESIA of Paris Observatory and IPAG of Université Grenoble Alpes/CNRS, the University of Cologne, the Centro Multidisciplinar de Astrofísica Lisbon and Porto (SIM), and ESO.

[3] The team will, for the first time, be able to measure two relativistic effects for a star orbiting a massive black hole — the gravitational redshift and the precession of the pericentre. The redshift arises because light from the star has to move against the strong gravitational field of the massive black hole in order to escape into the Universe. As it does so it loses energy, which manifests as a redshift of the light. The second effect applies to the star’s orbit and leads to a deviation from a perfect ellipse. The orientation of the ellipse rotates by around half a degree in the orbital plane when the star passes close to the black hole. The same effect has been observed for Mercury’s orbit around the Sun, where it is about 6500 times weaker per orbit than in the extreme vicinity of the black hole. But the larger distance makes it much harder to observe in the Galactic Centre than in the Solar System.

Uncategorized

“Venus” – A 4-part graphic novel

June 22, 2016 TopSpacer

Phil Plait reviewed Venus, the four part comic coming out in October: Rick Loverd comic book mini-series Venus features good science.

What would it take to colonize Venus?

The idea is a bit far-fetched right now, but in 100 years or more, who knows? It might be possible, if our circumstances drive us to try it … and that’s the premise for the four-part comic miniseries Venus, written by my friend Rick Loverd and published by Boom! Studios.

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So when Rick asked me to take a look at his comic about the crew of the Mayflower, a group of explorers who will be the first to attempt to live on the barely tamed surface of Venus, I was intrigued. Unsurprisingly to me, I liked it! It has a lot of comic-style derring-do coupled with a pretty firm basis in science, extrapolating from what we know today and seeing where it might take us.

More at VENUS #1 (OF 4) | BOOM! Studios Blog

Venus_001_Main_PRESS-666x1024[1] — *VENUS #1 Main Cover by W. Scott Forbes*

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Mars, Space Science, Space Systems

Mars rover Opportunity wrapping up study of Marathon Valley

June 21, 2016 TopSpacer

The Mars rover Opportunity, in operation since January 2004, continues to explore and make new discoveries. Here is its latest report:

Rover Opportunity Wrapping up Study of Martian Valley

IDL TIFF file — Mars Rover Opportunity’s Panorama of ‘Marathon Valley’ “Marathon Valley” on Mars opens to a view across Endeavour Crater in this scene from the Pancam of NASA’s Mars rover Opportunity. The scene merges many exposures taken during April and May 2016. The view spans from north (left) to west-southwest. Its foreground shows the valley’s fractured texture. Continue

“Marathon Valley,” slicing through a large crater’s rim on Mars, has provided fruitful research targets for NASA’s Opportunity rover since July 2015, but the rover may soon move on.

Opportunity recently collected a sweeping panorama from near the western end of this east-west valley. The vista shows an area where the mission investigated evidence about how water altered the ancient rocks and, beyond that, the wide floor of Endeavour Crater and the crater’s eastern rim about 14 miles (22 kilometers) away.

Marathon Valley lured the mission because researchers using NASA’s Mars Reconnaissance Orbiter had mapped water-related clay minerals at this area of the western rim of Endeavour Crater. The rover team chose the valley’s informal name because Opportunity’s arrival at this part of the rim coincided closely with the rover surpassing marathon-footrace distance in total driving since its January 2004 Mars landing.

“We are wrapping up our last few activities in Marathon Valley and before long we’ll drive away, exiting along the southern wall of the valley and heading southeast,” said Opportunity Principal Investigator Steve Squyres, of Cornell University, Ithaca, New York.

As Opportunity examined the clay-bearing rocks on the valley floor that were detected from orbit, the rover’s own observations of the valley’s southern flank revealed streaks of red-toned, crumbly material. The science team chose to investigate this apparently weathered material. The rover approached exposures of it to prepare for using the Rock Abrasion Tool, called the RAT. This tool grinds away a rock’s surface to expose the interior for inspection.

“What we usually do to investigate material that’s captured our interest is find a bedrock exposure of it and use the RAT,” Squyres said. “What we didn’t realize until we took a close-enough look is that this stuff has been so pervasively altered, it’s not bedrock. There’s no solid bedrock you could grind with the RAT.”

Instead, the rover exposed some fresh surfaces for inspection by scuffing some of the reddish material with a wheel.

Squyres said,

“In the scuff, we found one of the highest sulfur contents that’s been seen anywhere on Mars. There’s strong evidence that, among other things, these altered zones have a lot of magnesium sulfate. We don’t think these altered zones are where the clay is, but magnesium sulfate is something you would expect to find precipitating from water.

“Fractures running through the bedrock, forming conduits through which water could flow and transport soluble materials, could alter the rock and create the pattern of red zones that we see.”

As of June 14, Opportunity has driven 26.59 miles (42.79 kilometers). NASA’s Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, built the rover and manages the mission for NASA’s Science Mission Directorate, Washington. For more information about Opportunity, visit:

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You can find maps of where Opportunity has traveled at Mars Exploration Rover Mission: Opportunity Traverse Map Archive. This map shows its recent path as of June 17, 2016:

Astronomy, Exoplanets

Kepler space telescope spots newborn exoplanet around young star

June 21, 2016 TopSpacer

The Kepler observatory finds an unusual exoplanet:

NASA’s K2 Finds Newborn Exoplanet Around Young Star

Astronomers have discovered the youngest fully formed exoplanet ever detected. The discovery was made using NASA’s Kepler Space Telescope and its extended K2 mission, as well as the W. M. Keck Observatory on Mauna Kea, Hawaii. Exoplanets are planets that orbit stars beyond our sun.

PIA20690_hires[1] — K2-33b, shown in this illustration, is one of the youngest exoplanets detected to date. It makes a complete orbit around its star in about five days. These two characteristics combined provide exciting new directions for planet-formation theories. K2-33b could have formed on a farther out orbit and quickly migrated inward. Alternatively, it could have formed in situ, or in place. NASA’s Ames Research Center in California’s Silicon Valley manages the Kepler and K2 missions for NASA’s Science Mission Directorate. NASA’s Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado in Boulder.

The newfound planet, K2-33b, is a bit larger than Neptune and whips tightly around its star every five days. It is only 5 to 10 million years old, making it one of a very few newborn planets found to date.

“Our Earth is roughly 4.5 billion years old,” said Trevor David of Caltech in Pasadena, lead author of a new study published online June 20, 2016, in the journal Nature. “By comparison, the planet K2-33b is very young. You might think of it as an infant.”

David is a graduate student working with astronomer Lynne Hillenbrand, also of Caltech.

Planet formation is a complex and tumultuous process that remains shrouded in mystery. Astronomers have discovered and confirmed roughly 3,000 exoplanets so far; however, nearly all of them are hosted by middle-aged stars, with ages of a billion years or more. For astronomers, attempting to understand the life cycles of planetary systems using existing examples is like trying to learn how people grow from babies to children to teenagers, by only studying adults.

“The newborn planet will help us better understand how planets form, which is important for understanding the processes that led to the formation of Earth,” said co-author Erik Petigura of Caltech.

The first signals of the planet’s existence were measured by K2. The telescope’s camera detected a periodic dimming of the light emitted by the planet’s host star, a sign that an orbiting planet could be regularly passing in front of the star and blocking the light. Data from the Keck Observatory validated that the dimming was indeed caused by a planet, and also helped confirm its youthful age.

Infrared measurements from NASA’s Spitzer Space Telescope showed that the system’s star is surrounded by a thin disk of planetary debris, indicating that its planet-formation phase is wrapping up. Planets form out of thick disks of gas and dust, called protoplanetary disks, that surround young stars.

“Initially, this material may obscure any forming planets, but after a few million years, the dust starts to dissipate,” said co-author Anne Marie Cody, a NASA Postdoctoral Program fellow at NASA’s Ames Research Center in California’s Silicon Valley. “It is during this time window that we can begin to detect the signatures of youthful planets with K2.”

A surprising feature in the discovery of K2-33b is how close the newborn planet lies to its star. The planet is nearly 10 times closer to its star than Mercury is to our sun, making it hot. While numerous older exoplanets have been found orbiting very tightly to their stars, astronomers have long struggled to understand how more massive planets like this one wind up in such small orbits. Some theories propose that it takes hundreds of millions of years to bring a planet from a more distant orbit into a close one — and therefore cannot explain K2-33b, which is quite a bit younger.

The science team says there are two main theories that may explain how K2-33b wound up so close to its star. It could have migrated there in a process called disk migration that takes hundreds of thousands of years. Or, the planet could have formed “in situ” — right where it is. The discovery of K2-33b therefore gives theorists a new data point to ponder.

“After the first discoveries of massive exoplanets on close orbits about 20 years ago, it was immediately suggested that they could absolutely not have formed there, but in the past several years, some momentum has grown for in situ formation theories, so the idea is not as wild as it once seemed,” said David.

“The question we are answering is: Did those planets take a long time to get into those hot orbits, or could they have been there from a very early stage? We are saying, at least in this one case, that they can indeed be there at a very early stage,” he said.

Ames manages the Kepler and K2 missions for NASA’s Science Mission Directorate. NASA’s Jet Propulsion Laboratory in Pasadena, California, managed Kepler mission development. Ball Aerospace & Technologies Corporation operates the flight system with support from the Laboratory for Atmospheric and Space Physics at the University of Colorado at Boulder.