Phenominal new view of our galaxy’s core

Photo: Central bulge of the Milky Way Galaxy. ESO/VVV Consortium Acknowledgement: Ignacio Toledo, Martin Kornmesser
Central portion of the Milky Way: ESO/VVV Consortium – Acknowledgement: Ignacio Toledo, Martin Kornmesser

Using a whopping nine-gigapixel image from the VISTA infrared survey telescope at ESO’s Paranal Observatory, an international team of astronomers has created a catalogue of more than 84 million stars in the central parts of the Milky Way. This gigantic dataset contains more than ten times more more stars than previous studies and is a major step forward for the understanding of our home galaxy. The image gives viewers an incredible, zoomable view of the central part of our galaxy. It is so large that, if printed with the resolution of a typical book, it would be 9 meters long and 7 meters tall.

“By observing in detail the myriads of stars surrounding the centre of the Milky Way we can learn a lot more about the formation and evolution of not only our galaxy, but also spiral galaxies in general,” explains Roberto Saito (Pontificia Universidad Católica de Chile, Universidad de Valparaíso and The Milky Way Millennium Nucleus, Chile), lead author of the study.

Most spiral galaxies, including our home galaxy the Milky Way, have a large concentration of ancient stars surrounding the centre that astronomers call the bulge. Understanding the formation and evolution of the Milky Way’s bulge is vital for understanding the galaxy as a whole. However, obtaining detailed observations of this region is not an easy task.
“Observations of the bulge of the Milky Way are very hard because it is obscured by dust,” says Dante Minniti (Pontificia Universidad Catolica de Chile, Chile), co-author of the study. “To peer into the heart of the galaxy, we need to observe in infrared light, which is less affected by the dust.”

Photo: Center of the Milky Way with VISTA region indicated. ESO/Nick Risinger (skysurvey.org)
Central portion of the Milky Way with VISTA region indicated. ESO/Nick Risinger (skysurvey.org)

The large mirror, wide field of view and very sensitive infrared detectors of ESO’s 4.1-meter Visible and Infrared Survey Telescope for Astronomy (VISTA) make it by far the best tool for this job. The team of astronomers is using data from the VISTA Variables in the Via Lactea program (VVV), one of six public surveys carried out with VISTA. The data have been used to create a monumental 108 200 by 81 500 pixel color image containing nearly nine billion pixels. This is one of the biggest astronomical images ever produced. The team has now used these data to compile the largest catalogue of the central concentration of stars in the Milky Way ever created.

To help analyze this huge catalog the brightness of each star is plotted against its color for about 84 million stars to create a color–magnitude diagram. This plot contains more than ten times more stars than any previous study and it is the first time that this has been done for the entire bulge. Color–magnitude diagrams are very valuable tools that are often used by astronomers to study the different physical properties of stars such as their temperatures, masses and ages.

“Each star occupies a particular spot in this diagram at any moment during its lifetime. Where it falls depends on how bright it is and how hot it is. Since the new data gives us a snapshot of all the stars in one go, we can now make a census of all the stars in this part of the Milky Way,” explains Dante Minniti.

The new color–magnitude diagram of the bulge contains a treasure trove of information about the structure and content of the Milky Way. One interesting result revealed in the new data is the large number of faint red dwarf stars. These are prime candidates around which to search for small exoplanets using the transit method.

“One of the other great things about the VVV survey is that it’s one of the ESO VISTA public surveys. This means that we’re making all the data publicly available through the ESO data archive, so we expect many other exciting results to come out of this great resource,” concludes Roberto Saito. For access to much larger versions of these images, visit the ESO Web site.

Source: ESO News Release

Earth-sized planet discovered in Alpha Centauri system

European astronomers have discovered a planet with about the mass of the Earth orbiting a star in the Alpha Centauri system — the nearest to Earth. It is also the lightest exoplanet ever discovered around a star like the Sun. The planet was detected using the HARPS instrument on the 3.6-metre telescope at ESO’s La Silla Observatory in Chile. The results appeared online in the journal Nature on October 17, 2012.

Alpha Centauri is one of the brightest stars in the southern skies and is the nearest stellar system to our Solar System — only 4.3 light-years away. It is actually a triple star — a system consisting of two stars similar to the Sun orbiting close to each other, designated Alpha Centauri A and B, and a more distant and faint red component known as Proxima Centauri. Since the 19th century astronomers have speculated about planets orbiting these bodies, the closest possible abodes for life beyond the Solar System, but searches of increasing precision had revealed nothing. Until now.

“Our observations extended over more than four years using the HARPS instrument and have revealed a tiny, but real, signal from a planet orbiting Alpha Centauri B every 3.2 days,” says Xavier Dumusque (Geneva Observatory, Switzerland and Centro de Astrofisica da Universidade do Porto, Portugal), lead author of the paper. “It’s an extraordinary discovery and it has pushed our technique to the limit!”

The European team detected the planet by picking up the tiny wobbles in the motion of the star Alpha Centauri B created by the gravitational pull of the orbiting planet. The effect is minute — it causes the star to move back and forth by no more than 51 centimetres per second (1.8 km/hour), about the speed of a baby crawling. This is the highest precision ever achieved using this method.

Alpha Centauri B is very similar to the Sun but slightly smaller and less bright. The newly discovered planet, with a mass of a little more than that of the Earth, is orbiting about six million kilometres away from the star, much closer than Mercury is to the Sun in the Solar System. The orbit of the other bright component of the double star, Alpha Centauri A, keeps it hundreds of times further away, but it would still be a very brilliant object in the planet’s skies.

The first exoplanet around a Sun-like star was found by the same team back in 1995 and since then there have been more than 800 confirmed discoveries, but most are much bigger than the Earth, and many are as big as Jupiter. The challenge astronomers now face is to detect and characterise a planet of mass comparable to the Earth that is orbiting in the habitable zone around another star. The first step has now been taken.

“This is the first planet with a mass similar to Earth ever found around a star like the Sun. Its orbit is very close to its star and it must be much too hot for life as we know it,” adds Stéphane Udry (Geneva Observatory), a co-author of the paper and member of the team, “but it may well be just one planet in a system of several. Our other HARPS results, and new findings from Kepler, both show clearly that the majority of low-mass planets are found in such systems.”

Source: European Southern Observatory

Auroras delight night owls

Photo: Auroral display over Lake Erie. Photo by Christopher Christie.
Auroral display over Lake Erie. Photo by Christopher Christie.

A group of CAA members took advantage of beautiful night sky conditions to set up and observe from Medina County Parks’ Letha House Park — site of our Observatory. Among them was Christopher Christie. “I got home about 2:00 AM after a great, but cold night out at Letha House” he wrote. “I was starting to wind down around 3:00 AM when I noticed the Kp index was kicking up as the solar wind increased, it wasn’t much at the time but I kept an eye on it.”

He kept tabs on the situation. “About 3:30 the KP was up at 6, so I went to my front porch and didn’t see anything, but checked some of the other sites I use to check on the aurora and one showed a possibility of some moving in. So I went to the lake shore just inside Rocky River, and, well after about an hour and 175 images or so I was very happy.” We’re pretty pleased to see his results.

Auroral display over Lake Erie. White light at left-horizon is a passing boat. Photo by Christopher Christie.

It turns out Christie had tapped into the beginning of a big geomagnetic storm. By Saturday afternoon SpaceWeather.com was reporting that the storm continued to light the skies over nighttime areas of the globe and was expected to be active through Saturday night. Of course Saturday night brought clouds and rain to the Greater Cleveland Area. Still, it was a noteworthy event.

SpaceWeather.com explained, “The ongoing storm was triggered by a knot of south-pointing magnetism from the sun. During the early hours of Oct. 13, the knot bumped into Earth’s magnetic field, opening a crack in our planet’s magnetosphere. Solar wind poured in to fuel the auroras.”

CAA is on Facebook

Responding to popular demand, we have established a Facebook account for the Cuyahoga Astronomical Association. As of this date, the account is “live” but there is only a bare minimum amount of information and imagery there. Over the next days and weeks the presence will begin to flesh out. We hope the account will broaden the CAA’s reach and recognition and offer new avenues of communication. The username “cuyastro” has been set for Cuyahoga Astronomical Association (“CAA” is too short!). To visit us at Facebook, click here: facebook.com/cuyastro