Chandra Scientist Eleonora Nora Troja

Eleonora Nora Troja was born and raised in Palermo, Sicily. After completing her PhD at the University of Palermo, she moved to NASA Goddard Space Flight Center as a NASA Postdoctoral Program Fellow. Her main research interest is the study of gamma-ray bursts, and in particular the connection between short duration gamma-ray bursts, neutron star mergers and gravitational waves. Beside her studies, she also leads the Swift Guest Investigator Program and serves as co-chair for the Athena mission working groups.

What are gravitational waves?

Gravitational waves are ripples in the fabric of space and time. According to Einstein’s theory of general relativity, every moving object actually emits a tiny amount of gravitational waves, but the signal is usually too small for us to detect. In order for us to detect gravitational waves, we need to wait for catastrophic events like the collision of two neutron stars. This brings to the second question, what are neutron stars? Neutron stars are some of the most exotic and dense objects in our Universe. These stars weight as much as our Sun but they are much smaller in size. A neutron star can extend up to 15-17 miles across, this is more or less the size of Washington D.C.

This graphic shows two of five new pairs of supermassive black holes recently identified by astronomers using a combination of data from NASA's Chandra X-ray Observatory, the Wide-Field Infrared Sky Explorer Survey (WISE), the ground-based Large Binocular Telescope in Arizona, and the Sloan Digital Sky Survey (SDSS) Mapping Nearby Galaxies at APO (MaNGA) survey. This discovery could help astronomers better understand how giant black holes grow and how they may produce the strongest gravitational wave signals in the Universe, as described in our press release.

Each pair contains two supermassive black holes weighing millions of times the mass of the Sun. These black hole couples formed when two galaxies collided and merged with each other, forcing their supermassive black holes close together. While theoretical models have predicted such giant growing black hole pairings should be relatively abundant, they have been difficult to find.

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.

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.

Illustration of Chandra X-ray Observatory

This week marks the 18th anniversary of Chandra’s “First Light,” when the first publicly available images from NASA’s flagship X-ray mission were released back in 1999 . Week after week, month after month, year after year, Chandra continues to deliver amazing results and make truly extraordinary discoveries across space. Scientists know so much more about the Universe now than we did before this amazing telescope began its work.

Credit: Kristin Divona, NASA/CXC

Women have played a key role in observing solar eclipses and expanding our understanding of how the Sun, our nearest star, works.

The total solar eclipse that will take place over North America in a couple of weeks is a chance for millions of people to experience an exciting event (with proper viewing glasses to protect our sensitive eyes, of course!). Given the population's demographics, it stands to reason that about half of those who will be under the spectacle of totality will be women.

This is rather appropriate to reflect on. To quote the title of the best seller by Nicolas Kristof and Sheryl Dunn (by way of Mao Zedong), "women hold up half the sky." But women have been doing far more than just shouldering the weight of the heavens over the years. We have been actively studying the Sun, Moon, stars and beyond for millennia. Women have played a key role in observing solar eclipses and expanding our understanding of how the Sun, our nearest star, works.

In 1887, American astronomer Lewis Swift discovered a glowing cloud, or nebula, that turned out to be a small galaxy about 2.2 million light years from Earth. Today, it is known as the "starburst" galaxy IC 10, referring to the intense star formation activity occurring there.

More than a hundred years after Swift's discovery, astronomers are studying IC 10 with the most powerful telescopes of the 21st century. New observations with NASA's Chandra X-ray Observatory reveal many pairs of stars that may one day become sources of perhaps the most exciting cosmic phenomenon observed in recent years: gravitational waves.

Jeff McClintock

(A continuing series on how astrophysicists’ varied career paths. Pathways to the Stars -- I)

Jeff's Journey

Jeff McClintock is recognized around the world as one the pre-eminent experts on black holes. In 2009, he shared the American Astronomical Society’s prestigious Bruno Rossi prize, along with Ron Remillard and Charles Bailyn for his work on the measurement of the masses of black holes.

McClintock has also served on the board of directors for the Giant Magellan Telescope, a telescope under construction that when it is commissioned in 2022, will be the largest optical telescope in existence. As it turns out, Jeff has been interested in large telescopes for a long time, going back to his childhood in Port Orchard, Washington.

“I saw an ad in Popular Mechanics,” he remembered. “It said, ‘You can build a 100-power telescope for $1!’”

McClintock mailed in his dollar, and received two lenses in the mail.

“That was it. Two lenses. I inserted the lenses at the ends of a discarded 8-foot cardboard tube which had been used to store linoleum."

He didn’t have a mount for his telescope, so he put it on several chairs in the living room, and looked through it, at some lights across Port Orchard strait near Seattle.

“I could see blue lights across the bay, and read a sign. It was upside down! I took it up to the attic and looked at the moon. I was blown away!”

Inspired by the view of the craters on the moon, McClintock built a second telescope, a 6” reflector.

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.

What would happen if you took two galaxies and mixed them together over millions of years? A new image including data from NASA's X-ray Observatory reveals the cosmic culinary outcome.

Arp 299 is a system located about 140 million light years from Earth. It contains two galaxies that are merging, creating a partially blended mix of stars from each galaxy in the process.

However, this stellar mix is not the only ingredient. New data from Chandra reveals 25 bright X-ray sources sprinkled throughout the Arp 299 concoction. Fourteen of these sources are such strong emitters of X-rays that astronomers categorize them as "ultra-luminous X-ray sources," or ULXs.

These ULXs are found embedded in regions where stars are currently forming at a rapid rate. Most likely, the ULXs are binary systems where a neutron star or black hole is pulling matter away from a companion star that is much more massive than the Sun. These double star systems are called high-mass X-ray binaries.