Normal Stars & Star Clusters

A Cosmic Jekyll and Hyde

Image of Terzan 5 in optical and X-ray light
Terzan 5
Credit: X-ray: NASA/CXC/Univ. of Amsterdam/N.Degenaar, et al.; Optical: NASA, ESA

A double star system has been flipping between two alter egos, according to observations with NASA's Chandra X-ray Observatory and the National Science Foundation's Karl F. Jansky Very Large Array (VLA). Using nearly a decade and a half worth of Chandra data, researchers noticed that a stellar duo behaved like one type of object before switching its identity, and then returning to its original state after a few years. This is a rare example of a star system changing its behavior in this way.

Astronomers found this volatile double, or binary, system in a dense collection of stars, the globular cluster Terzan 5, which is located about 19,000 light years from Earth in the Milky Way galaxy. This stellar duo, known as Terzan 5 CX1, has a neutron star (the extremely dense remnant left behind by a supernova explosion) in close orbit around a star similar to the Sun, but with less mass.

Hunting for Stellar CMEs: The Chandra Success

Costanza Argiroffi
Costanza Argiroffi

We are pleased to welcome Costanza Argiroffi as a guest author. Costanza led the study reporting the first secure detection of a coronal mass ejection from a star other than the Sun. She is an astrophysicist from the University of Palermo, Italy, where she is from. Her main research field is the study of low-mass stars. She obtained her PhD from the University of Palermo in 2006, and during her studies spent a few months at the Smithsonian Astrophysical Observatory in Cambridge, MA. Then she worked as a postdoc and, since 2008, as a researcher at the University of Palermo.

Coronal Mass Ejections (CMEs) are large-scale expulsions of material previously confined in the atmosphere of a star. CMEs are among the most powerful magnetic phenomena occurring in the atmosphere of the Sun, reaching velocities of about 2 million miles per hour, masses of about 200,000 billion pounds, and kinetic energies equivalent to about 125 million Krakatoa eruptions.

Using data from NASA’s Chandra X-ray Observatory, we have made the first unambiguous detection of a CME by a star other than the Sun.

NGC 3079: Galactic Bubbles Play Cosmic Pinball with Energetic Particles

Image of NGC 3079
NGC 3079
Credit: X-ray: NASA/CXC/University of Michigan/J-T Li et al.; Optical: NASA/STScI

We all know bubbles from soapy baths or sodas. These bubbles of everyday experience on Earth are only a few inches across, and consist of a thin film of liquid enclosing a small volume of air or other gas. In space, however, there are very different bubbles — composed of a lighter gas inside a heavier one — and they can be huge.

The galaxy NGC 3079, located about 67 million light years from Earth, contains two "superbubbles" unlike anything here on our planet. A pair of balloon-like regions stretch out on opposite sides of the center of the galaxy: one is 4,900 light years across and the other is only slightly smaller, with a diameter of about 3,600 light years. For context, one light year is about 6 trillion miles, or 9 trillion kilometers.

Chandra Serves up Cosmic Holiday Assortment

This is the season of celebrating, and the Chandra X-ray Center has prepared a platter of cosmic treats from NASA's Chandra X-ray Observatory to enjoy. This selection represents different types of objects — ranging from relatively nearby exploded stars to extremely distant and massive clusters of galaxies — that emit X-rays detected by Chandra. Each image in this collection blends Chandra data with other telescopes, creating a colorful medley of light from our Universe.

Two Stars, Three Dimensions, and Oodles of Energy

V745

For decades, astronomers have known about irregular outbursts from the double star system V745 Sco, which is located about 25,000 light years from Earth. Astronomers were caught by surprise when previous outbursts from this system were seen in 1937 and 1989. When the system erupted on February 6, 2014, however, scientists were ready to observe the event with a suite of telescopes including NASA’s Chandra X-ray Observatory.

X-rays Reveal Temperament of Possible Planet-hosting Stars

illustration of planet orbiting a star
Illustration Credit: NASA/CXC/M.Weiss

A new study using data from NASA's Chandra X-ray Observatory and ESA's XMM-Newton suggests X-rays emitted by a planet's host star may provide critical clues to just how hospitable a star system could be. A team of researchers looked at 24 stars similar to the Sun, each at least one billion years old, and how their X-ray brightness changed over time.

Since stellar X-rays mirror magnetic activity, X-ray observations can tell astronomers about the high-energy environment around the star. In the new study the X-ray data from Chandra and XMM-Newton revealed that stars like the Sun and their less massive cousins calm down surprisingly quickly after a turbulent youth.

This artist's illustration depicts one of these comparatively calm, older Sun-like stars with a planet in orbit around it. The large dark area is a "coronal hole", a phenomenon associated with low levels of magnetic activity. The inset box shows the Chandra data of one of the observed objects, a two billion year old star called GJ 176, located 30 light years from Earth.

W51: Chandra Peers into a Nurturing Cloud

W51

In the context of space, the term 'cloud' can mean something rather different from the fluffy white collections of water in the sky or a way to store data or process information. Giant molecular clouds are vast cosmic objects, composed primarily of hydrogen molecules and helium atoms, where new stars and planets are born. These clouds can contain more mass than a million suns, and stretch across hundreds of light years.

The giant molecular cloud known as W51 is one of the closest to Earth at a distance of about 17,000 light years. Because of its relative proximity, W51 provides astronomers with an excellent opportunity to study how stars are forming in our Milky Way galaxy.

A new composite image of W51 shows the high-energy output from this stellar nursery, where X-rays from Chandra are colored blue. In about 20 hours of Chandra exposure time, over 600 young stars were detected as point-like X-ray sources, and diffuse X-ray emission from interstellar gas with a temperature of a million degrees or more was also observed. Infrared light observed with NASA's Spitzer Space Telescope appears orange and yellow-green and shows cool gas and stars surrounded by disks of cool material.

Watching a Volatile Stellar Relationship

R Aquarii
In biology, "symbiosis" refers to two organisms that live close to and interact with one another. Astronomers have long studied a class of stars – called symbiotic stars – that co-exist in a similar way. Using data from NASA’s Chandra X-ray Observatory and other telescopes, astronomers are gaining a better understanding of how volatile this close stellar relationship can be.

R Aquarii (R Aqr, for short) is one of the best known of the symbiotic stars. Located at a distance of about 710 light years from Earth, its changes in brightness were first noticed with the naked eye almost a thousand years ago. Since then, astronomers have studied this object and determined that R Aqr is not one star, but two: a small, dense white dwarf and a cool red, giant star.

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