Posted on by Nancy Atkinson

First Light Image for NuSTAR

Here is the first image taken by the newest space mission, NuSTAR, or the Nuclear Spectroscopic Telescope Array, the first space telescope with the ability to see the highest energy X-rays in our universe and produce crisp images of them.

“Today, we obtained the first-ever focused images of the high-energy X-ray universe,” said Fiona Harrison, the mission’s principal investigator. “It’s like putting on a new pair of glasses and seeing aspects of the world around us clearly for the first time.”

With the successful “first light” images, the mission will begin its exploration of the most elusive and energetic black holes — as well as other areas of extreme physics in our cosmos — to help in our understanding of the structure of the universe.

The first images show Cygnus X-1, a black hole in our galaxy that is siphoning gas off a giant-star companion. This particular black hole was chosen as a first target because it is extremely bright in X-rays, allowing the NuSTAR team to easily see where the telescope’s focused X-rays are falling on the detectors.

NuSTAR launched on June 13 and its lengthy mast, which provides the telescope mirrors and detectors with the distance needed to focus X-rays, was deployed on June 21. The NuSTAR team spent the next week verifying the pointing and motion capabilities of the satellite, and fine-tuning the alignment of the mast.

The mission’s primary observing program is expected to start in about two weeks. But before it does, the team will continue tests and point the NuSTAR at two other bright calibration targets: G21.5-0.9, the remnant of a supernova explosion that occurred several thousand years ago in our own Milky Way galaxy; and 3C273, an actively feeding black hole, or quasar, located 2 billion light-years away at the center of another galaxy. These targets will be used to make a small adjustment to place the X-ray light at the optimum spot on the detector, and to further calibrate and understand the telescope in preparation for future science observations.

Other targets for the mission include the burnt-out remains of dead stars, such as those that exploded as supernovae; high-speed jets; the temperamental surface of our sun; and the structures where galaxies cluster together like mega-cities.

“This is a really exciting time for the team,” said Daniel Stern, the NuSTAR project scientist. “We can already see the power of NuSTAR to crack open the high-energy X-ray universe and reveal secrets that were impossible to get at before.”

Lead image caption: NASA’s Nuclear Spectroscopic Telescope Array, or NuSTAR, has taken its first snapshots of the highest-energy X-rays in the cosmos (lower right), producing images that are much crisper than previous high-energy telescopes (example in upper right). NuSTAR chose a black hole in the constellation Cygnus (shown in the skymap on the left) as its first target due to its brightness. Image credit: NASA/JPL-Caltech

Posted on by Nancy Atkinson

NuSTAR Successfully Deploys Huge Mast

Nine days after launch — and right on schedule — the newest space mission has deployed its unique mast, giving it the ability to see the highest energy X-rays in our universe. The Nuclear Spectroscopic Telescope Array, or NuSTAR, successfully deployed its lengthy 10-meter (33-foot) mast on June 21, and mission scientists say they are one step closer to beginning its hunt for black holes hiding in our Milky Way and other galaxies.

“It’s a real pleasure to know that the mast, an accomplished feat of engineering, is now in its final position,” said Yunjin Kim, the NuSTAR project manager at the Jet Propulsion Laboratory. Kim was also the project manager for the Shuttle Radar Topography Mission, which flew a similar mast on the Space Shuttle Endeavor in 2000 and made topographic maps of Earth.

NuSTAR will search out the most elusive and most energetic black holes, to help in our understanding of the structure of the universe.

NuSTAR has many innovative technologies to allow the telescope to take the first-ever crisp images of high-energy X-ray, and the long mast separates the telescope mirrors from the detectors, providing the distance needed to focus the X-rays.

This is the first deployable mast ever used on a space telescope; the mast was folded up in a small canister during launch.

At 10:43 a.m. PDT (1:43 p.m. EDT) engineers at NuSTAR’s mission control at UC Berkeley in California sent a signal to the spacecraft to start extending the mast, a stable, rigid structure consisting of 56 cube-shaped units. Driven by a motor, the mast steadily inched out of a canister as each cube was assembled one by one. The process took about 26 minutes. Engineers and astronomers cheered seconds after they received word from the spacecraft that the mast was fully deployed and secure.

The NuSTAR team will now begin to verify the pointing and motion capabilities of the satellite, and fine-tune the alignment of the mast. In about five days, the team will instruct NuSTAR to take its “first light” pictures, which are used to calibrate the telescope.
Less than 20 days later, science operations are scheduled to begin.

“With its unprecedented spatial and spectral resolution to the previously poorly explored hard X-ray region of the electromagnetic spectrum, NuSTAR will open a new window on the universe and will provide complementary data to NASA’s larger missions, including Fermi, Chandra, Hubble and Spitzer,” said Paul Hertz, NASA’s Astrophysics Division Director.

NuSTAR launched on an Orbital Science Corporation’s Pegasus rocket, which was dropped from a carrier plane, the L-1011 “Stargazer,” also from Orbital.

Lead image caption: Artist’s concept of NuSTAR in orbit. NuSTAR has a 33-foot (10-meter) mast that deploys after launch to separate the optics modules (right) from the detectors in the focal plane (left). Image credit: NASA/JPL-Caltech

Source: JPL

Posted on by Nancy Atkinson

Black Hole Hunter Drops from a Plane, Zooms to Orbit

NASA's NuSTAR and its rocket drop from the carrier "Stargazer" plane. Image Credit: Orbital Sciences Corporation.

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The newest mission to hunt for black holes soared to orbit today after first dropping from an aircraft. NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) launched 16:00 UTC (12 noon EDT, 9 a.m. PDT). NuSTAR was strapped to an Orbital Sciences Pegasus rocket, both of which strapped to an L-1011 “Stargazer” aircraft. The plane left Kwajalein Atoll in the central Pacific Ocean one hour before launch. Then at 9:00:35 a.m. PDT the rocket dropped, free-falling for five seconds before firing its first-stage motor.

“NuSTAR will help us find the most elusive and most energetic black holes, to help us understand the structure of the universe,” said Fiona Harrison, the mission’s principal investigator at the California Institute of Technology in Pasadena.

Watch the video of the launch below.

About 13 minutes after the rocket dropped, NuSTAR separated from the rocket, reaching its final low Earth orbit. The first signal from the spacecraft was received at 9:14 a.m. PDT via NASA’s Tracking and Data Relay Satellite System.

“NuSTAR spread its solar panels to charge the spacecraft battery and then reported back to Earth of its good health,” said Yunjin Kim, the mission’s project manager at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “We are checking out the spacecraft now and are excited to tune into the high-energy X-ray sky.”

The mission’s unique telescope design includes a 33-foot (10-meter) mast, which was folded up in a small canister during launch. In about seven days, engineers will command the mast to extend, enabling the telescope to focus properly. About 23 days later, science operations are scheduled to begin.
“With its unprecedented spatial and spectral resolution to the previously poorly explored hard X-ray region of the electromagnetic spectrum, NuSTAR will open a new window on the universe and will provide complementary data to NASA’s larger missions, including Fermi, Chandra, Hubble and Spitzer,” said Paul Hertz, NASA’s Astrophysics Division Director.

Combining all the data from the telescopes together will provide a more complete picture of the most energetic and exotic objects in space, such as black holes, dead stars and jets traveling near the speed of light.

NuSTAR will use a unique set of eyes to see the highest energy X-ray light from the cosmos. The observatory can see through gas and dust to reveal black holes lurking in our Milky Way galaxy, as well as those hidden in the hearts of faraway galaxies.

In addition to black holes and their powerful jets, NuSTAR will study a host of high-energy objects in our universe, including the remains of exploded stars; compact, dead stars; and clusters of galaxies. The mission’s observations, in coordination with other telescopes such as NASA’s Chandra X-ray Observatory, which detects lower-energy X-rays, will help solve fundamental cosmic mysteries. NuSTAR also will study our Sun’s fiery atmosphere, looking for clues as to how it is heated.

Learn more about NuStar at the mission website.

Posted on by Nancy Atkinson

Newest X-Ray Observatory Will Hunt for Black Holes and More

An artist's concept of NuSTAR in space. Image credit: NASA/JPL-Caltech/Orbital Sciences

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The next launch of a NASA space mission is the Nuclear Spectroscopic Telescope Array, or NuSTAR. It study wide range of objects in space, from massive black holes to our own Sun, and will be the first space telescope to create focused images of cosmic X-rays with the highest energies.

“We will see the hottest, densest and most energetic objects with a fundamentally new, high-energy X-ray telescope that can obtain much deeper and crisper images than before,” said Fiona Harrison, the NuSTAR principal investigator, who has been working on this project for 20 years.

Meanwhile, NASA has cancelled another X-ray telescope, the Gravity and Extreme Magnetism Small Explorer (GEMS) X-ray telescope, an astrophysics mission that was going to launch in 2014 to observe the space near neutron stars and black holes. GEMS failed meet a the qualifications of a confirmation review and was heading to go over budget.

“The decision was made to non-confirm GEMS,” said Paul Hertz, director of NASA’s Astrophysic Division, at a meeting of the National Research Council’s Committee on Astronomy and Astrophysics. “The rationale was that the pre-confirmation cost and schedule growth was too large.” The project was going well over the initial cost of $105 million and was facing a delay in launch.

But NuSTAR is scheduled to launch on June 13 from the Kwajalein Atoll in the Pacific Ocean near the equator. The X-ray space telescope will initially take off on a L-1011 “Stargazer” aircraft, and then launch in midair into orbit on a Pegasus XL rocket from Orbital Sciences.

The mission has been awaiting launch since March, when NASA delayed its liftoff pending a review of the rocket.

NuSTAR will work with other telescopes in space now, including NASA’s Chandra X-ray Observatory, which observes lower-energy X-rays. Together, they will provide a more complete picture of the most energetic and exotic objects in space, such as black holes, dead stars and jets traveling near the speed of light.

This new observatory looks with X-rays similar to the X-rays used in hospitals and airports, but the telescope will have more than 10 times the resolution and more than 100 times the sensitivity of previous telescopes.

“NuSTAR uses several innovations for its unprecedented imaging capability and was made possible by many partners,” said Yunjin Kim, the project manager for the mission at NASA’s Jet Propulsion Laboratory in Pasadena, Calif. “We’re all really excited to see the fruition of our work begin its mission in space.”

NuSTAR has an innovative design using a nested shell of mirrors to provide better focus. It also has state-of-the-art detectors and a large 33-foot (10-meter) mast, which connects the detectors to the nested mirrors, providing the long distance required to focus the X-rays. This mast is folded up into a canister small enough to fit atop the Pegasus launch vehicle. It will unfurl about seven days after launch. About 23 days later, science operations will begin.
The mission will focus on studying the formation of black holes and investigate how exploding stars forge the elements that make up planets and people, along with study the Sun’s atmosphere.

Sources: JPL Space News (GEMS)

Posted on by Nancy Atkinson

New Image Shows Beautiful Violence in Centaurus A

Centaurus A in Far-infrared and X-rays. Credit: Far-infrared: ESA/Herschel/PACS/SPIRE/C.D. Wilson, MacMaster University, Canada; X-ray: ESA/XMM-Newton/EPIC

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The mysterious galaxy Centaurus A is a great place to study the extreme processes that occur near super-massive black holes, scientists say, and this beautiful new image from the combined forces of the Herschel Space Observatory and the XMM-Newton x-ray satellite reveals energetic processes going on deep in the galaxy’s core. This beautiful image tells a tale of past violence that occurred here.

The twisted disc of dust near the galaxy’s heart shows strong evidence that Centaurus A underwent a cosmic collision with another galaxy in the distant past. The colliding galaxy was ripped apart to form the warped disc, and the formation of young stars heats the dust to cause the infrared glow.

This multi-wavelength view of Centaurus A shows two massive jets of material streaming from a immense black hole in the center. When observed by radio telescopes, the jets stretch for up to a million light years, though the Herschel and XMM-Newton results focus on the inner regions.

At a distance of around 12 million light years from Earth, Centaurus A is the closest large elliptical galaxy to our own Milky Way.

“Centaurus A is the closest example of a galaxy to us with massive jets from its central black hole,” said Christine Wilson of McMaster University, Canada, who is leading the study of Centaurus A with Herschel. “Observations with Herschel, XMM-Newton and telescopes at many other wavelengths allow us to study their effects on the galaxy and its surroundings.”

Find more information on this image at ESA’s website.

Posted on by Tammy Plotner

Supernova G350 Kicks Up Some X-Ray Dust

Vital clues about the devastating ends to the lives of massive stars can be found by studying the aftermath of their explosions. In its more than twelve years of science operations, NASA's Chandra X-ray Observatory has studied many of these supernova remnants sprinkled across the Galaxy. Credit: X-ray: NASA/CXC/SAO/I.Lovchinsky et al, IR: NASA/JPL-Caltech

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Located some 14,700 light years from the Earth toward the center of our galaxy, a newly photographed supernova remnant cataloged as G350.1+0.3 is making astronomers scratch their heads. The star which created this unusual visage is suspected to have blown its top some 600 to 1,200 years ago. Although it would have been as bright as the event which created the “Crab”, chances are no one saw it due to the massive amounts of gas and dust at the Milky Way’s heart. Now NASA’s Chandra X-ray Observatory and the ESA’s XMM-Newton telescope has drawn back the curtain and we’re able to marvel at what happens when a supernova imparts a powerful X-ray “kick” to a neutron star!

Credit: X-ray: NASA/CXC/SAO/I.Lovchinsky et al, IR: NASA/JPL-Caltech
Photographic proof from Chandra and XMM-Newton are full of clues which give rise to the possibility that a compact object located in the influence of G350.1+0.3 may be the core region of a shattered star. Since it is off-centered from the X-ray emissions, it must have received a powerful blast of energy during the supernova event and has been moving along at a speed of 3 million miles per hour ever since. This information agrees with an “exceptionally high speed derived for the neutron star in Puppis A and provides new evidence that extremely powerful ‘kicks’ can be imparted to neutron stars from supernova explosions.”

As you look at the photo, you’ll notice one thing in particular… the irregular shape. The Chandra data in this image appears as gold while the infrared data from NASA’s Spitzer Space Telescope is colored light blue. According to the research team, this unusual configuration may have been caused by the stellar debris field imparting itself into the surrounding cold molecular gas.

These results appeared in the April 10, 2011 issue of The Astrophysical Journal. The scientists on this paper were Igor Lovchinsky and Patrick Slane (Harvard-Smithsonian Center for Astrophysics), Bryan Gaensler (University of Sydney, Australia), Jack Hughes (Rutgers University), Stephen Ng (McGill University), Jasmina Lazendic (Monash University Clayton, Australia), Joseph Gelfand (New York University, Abu Dhabi), and Crystal Brogan (National Radio Astronomy Observatory).

Original Story Source: NASA Chandra News Release.

Posted on by Amy Shira Teitel

NASA’s New Eyes in the Sky

An artist's concept of NuSTAR in space. Image credit: NASA/JPL-Caltech/Orbital

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On March 14, NASA will launch the Nuclear Spectroscopic Telescope Array or NuSTAR. This is the first time a telescope will focus on high energy X-rays, effectively opening up the sky for more sensitive study. The telescope will target black holes, supernova explosions, and will study the most extreme active galaxies. NuSTAR’s use of high-energy X-rays have an added bonus: it will be able to capture and compose the most detailed images ever taken in this end of the electromagnetic spectrum. 

NuSTAR’s eyes are two Wolter-I optic units; once in orbit each will ‘look’ at the same patch of sky. The Wolter-I mirror works by reflecting an X-ray twice, once off of an upper mirror shaped like a parabola and again off a lower mirror shaped like a hyperbola. The mirrors are nearly parallel to the direction of the incoming X-ray, reflecting most of the X-ray instead of absorbing it, but the slight angle allows for a very small collection area per surface. To get a full picture, mirrors of varying size are nested together.

Technicians work on NuSTAR this month at the Orbital Science Corporation in Dulles, Virginia. Image credit: NASA/JPL-Caltech/Orbital

Each of NuSTAR’s eyes, each unit, are made of 133 concentric shells of mirrors shaped from flexible glass like that found in laptop computer screens. This is an improvement over past missions like Chandra and XMM-Newton that both used high density materials such as Platinum, Iridium and Gold as mirror coatings. These materials achieve great reflectivity for low energy X-rays but can’t capture high energy X-rays.

Like human eyes, NuSTAR’s optical units are co-aligned to give the telescope a wider field of view and enable the capture of more sensitive images. These images will be made into detailed composites by scientists on the ground.

Also like human eyes, NuSTAR’s optical units need to be distanced from one another since X-ray telescopes require long focal lengths. In other words, the optics must be separated by several meters from the detectors. NuSTAR does this with a 33 foot (10 metre) long mast or boom between units.

Previous X-ray missions have accommodated these long focal lengths by launching fully deployed observatories on large rockets. NuSTAR won’t. It has a unique deployable mast that will extend once the payload is in orbit. This allows for a launch on the small Pegasus rocket. Undeployed, the telescope measures just 2 metres in length and one metre in diameter.

During its two-year primary mission, NuSTAR will map the celestial sky focussing on black holes, supernova remnants, and particle jets traveling near the speed of light. It will also look at the Sun. Observations of microflares could explain the temperature of the Sun’s corona. It will also search the Sun for evidence of a hypothesized dark matter particle to test a theory about dark matter.

NuSTAR's mast. Image credit: NASA/JPL-Caltech/Orbital

“NuSTAR will provide an unprecedented capability to discover and study some of the most exotic objects in the universe, from the corpses of exploded stars in the Milky Way to supermassive black holes residing in the hearts of distant galaxies,” said Lou Kaluzienski, NuSTAR program scientist at NASA Headquarters in Washington.

The telescope shipped from the Orbital Sciences Corporation in Dulles, Virginia to Vandenberg Air Force Base in California on January 27. There, it will be mated to its Pegasus launch vehicle on February 17. It will launch from underneath the L-1011 “Stargazer” aircraft on March 14 after taking off near the equator from Kwajalein Atoll in the Pacific.

Source: NASA

A Pegasus rocket launches from underneath a L-1011 "Stargazer" aircraft, just like NuSTAR will do in March. Image credit: NASA/JPL-Caltech/Orbital
Posted on by Jon Voisey

Different Supernovae; Different Neutron Stars

Artist concept of a neutron star. Credit: NASA
Artist concept of a neutron star. Credit: NASA

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Astronomers have recognized various ways that stars can collapse to undergo a supernova. In one situation, an iron core collapses. The second involves a lower mass star with oxygen, neon, and magnesium in the core which suddenly captures electrons when the conditions are just right, removing them as a support mechanism and causing the star to collapse. While these two mechanisms make good physical sense, there has never been any observational support showing that both types occur. Until now that is. Astronomers led yb Christian Knigge and Malcolm Coe at the University of Southampton in the UK announced that they have detected two distinct sub populations in the neutron stars that result from these supernova.

To make the discovery, the team studied a large number of a specific sub-class of neutron stars known as Be X-ray binaries (BeXs). These objects are a pair of stars formed by a hot B spectral class stars with hydrogen emission in their spectrum in a binary orbit with a neutron star. The neutron star orbits the more massive B star in an elliptical orbit, siphoning off material as it makes close approaches. As the accreted material strikes the neutron star’s surface it glows brightly in the X-rays, becoming, for a time, an X-ray pulsar allowing astronomers to measure the spin period of the neutron star.

Such systems are common in the Small Magellanic Cloud which appears to have a burst of star forming activity about 60 million years ago, allowing for the massive B stars to be in the prime of their stellar lives. It is estimated that the Small Magellanic Cloud alone has as many BeXs as the entire Milky Way galaxy, despite being 100 times smaller. By studying these systems as well the Large Magellanic Cloud and Milky Way, the team found that there are two overlapping but distinct populations of BeX neutron stars. The first had a short period, averaging around 10 seconds. A second group had an average of around 5 minutes. The team surmises that the two populations are a result of the different supernova formation mechanisms.

The two different formation mechanisms should also lead to another difference. The explosion is expected to give the star a “kick” that can change the orbital characteristics. The electron-captured supernovae are expected to give a kick velocity of less than 50 km/sec whereas the iron core collapse supernovae should be over 200 km/sec. This would mean the iron core collapse stars should have preferentially longer and more eccentric orbits. The team attempted to discern whether this too was supported by their evidence, but only a small fraction of the stars they examined had determined eccentricities. Although there was a small difference, it is too early to determine whether or not it was due to chance.

According to Knigge, “These findings take us back to the most fundamental processes of stellar evolution and lead us to question how supernovae actually work. This opens up numerous new research areas, both on the observational and theoretical fronts.

Posted on by Nancy Atkinson

More Details on the Black Hole that Swallowed a Screaming Star

Images from Swift's Ultraviolet/Optical (white, purple) and X-Ray telescopes (yellow and red) were combined to make this view of Swift J1644+57. Evidence of the flares is seen only in the X-ray image, which is a 3.4-hour exposure taken on March 28, 2011. Credit: NASA/Swift/Stefan Immler

Back in June we reported on the black hole that devoured a star and then hurled the x-ray energy across billions of light years, right at Earth. It was such a spectacular and unprecedented event, that more studies have been done on the source, known as Swift J1644+57, and the folks at the Goddard Space Flight Center mulitmedia team have produced an animation (above) of what the event may have looked like. Two new papers were published yesterday in Nature; one from a group at NASA studying the data from the Swift satellite and the Japanese Monitor of All-sky X-ray Image (MAXI) instrument aboard the International Space Station, and the other from scientists using ground-based observatories.

They have confirmed what happened was the result of a truly extraordinary event — the awakening of a distant galaxy’s dormant black hole as it shredded, sucked and consumed a star, and the X-ray burst was akin to the death screams of the star.

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In the new studies, detailed analysis of MAXI and Swift observations revealed this was the first time that a nucleus with no previous X-ray emission had ever suddenly started such activity. The strong X-ray and rapid variation indicated that the X-ray came from a jet that was pointed right at Earth.

“Incredibly, this source is still producing X-rays and may remain bright enough for Swift to observe into next year,” said David Burrows, professor of astronomy at Penn State University and lead scientist for Swift’s X-Ray Telescope instrument. “It behaves unlike anything we’ve seen before.”

The galaxy is so far away, it took the light from the event approximately 3.9 billion years to reach Earth (that distance was updated from the 3.8 billion light years reported in June).

The black hole in the galaxy hosting Swift J1644+57, located in the constellation Draco, may be twice the mass of the four-million-solar-mass black hole in the center of the Milky Way galaxy. As a star falls toward a black hole, it is ripped apart by intense tides. The gas is corralled into a disk that swirls around the black hole and becomes rapidly heated to temperatures of millions of degrees.

The innermost gas in the disk spirals toward the black hole, where rapid motion and magnetism create dual, oppositely directed “funnels” through which some particles may escape. Jets driving matter at velocities greater than 90 percent the speed of light form along the black hole’s spin axis.

This illustration steps through the events that scientists think likely resulted in Swift J1644+57. Credit: NASA/Goddard Space Flight Center/Swift

The Swift satellite detected flares from this region back on March 28, 2011, and the flares were initially assumed to signal a gamma-ray burst, one of the nearly daily short blasts of high-energy radiation often associated with the death of a massive star and the birth of a black hole in the distant universe. But as the emission continued to brighten and flare, astronomers realized that the most plausible explanation was the tidal disruption of a sun-like star seen as beamed emission.

“The radio emission occurs when the outgoing jet slams into the interstellar environment, and by contrast, the X-rays arise much closer to the black hole, likely near the base of the jet,” said Ashley Zauderer, from the Harvard-Smithsonian Center for Astrophysics in Cambridge, Mass, lead author of a study of the event from numerous ground-based radio observatories, including the National Radio Astronomy Observatory’s Expanded Very Large Array (EVLA) near Socorro, N.M.

“Our observations show that the radio-emitting region is still expanding at more than half the speed of light,” said Edo Berger, an associate professor of astrophysics at Harvard and a coauthor of the radio paper. “By tracking this expansion backward in time, we can confirm that the outflow formed at the same time as the Swift X-ray source.”

Swift launched in November 2004 and MAXI is mounted on the Japanese Kibo module on the ISS (installed in July 2009) and has been monitoring the whole sky since August 2009.

See more images and animations at the Goddard Space Flight Center Multimedia page.

Sources: Nature, JAXA, NASA

Posted on by Jon Voisey

Companion Stars Could Cause Unexpected X-Rays

Many types of main sequence stars emit in the X-ray portion of the spectra. In massive stars, strong stellar winds ripping through the extended atmosphere of the star create X-ray photons. On lower mass stars, magnetic fields twisting through the photosphere heat it sufficiently to produce X-rays. But between these two mechanisms, in the late B to mid A classes of stars, neither of these mechanisms should be sufficient to produce X-rays. Yet when X-ray telescopes examined these stars, many were found to produce X-rays just the same.

The first exploration into the X-ray emission of this class of stars was the Einstein Observatory, launched in 1978 and deorbited in 1982. While the telescoped confirmed that these B and A stars had significantly less X-ray emission overall, seven of the 35 A type stars still had some emission. Four of these were confirmed as being in binary systems in which the secondary stars could be the source of the emission, leaving three of seven with unaccounted for X-rays.

The German ROSAT satellite found similar results, detecting 232 X-ray stars in this range. Studies explored connections with irregularities in the spectra of these stars and rotational velocities, but found no correlation with either. The suspicion was that these stars simply hid undetected, lower mass companions.

In recent years, some studies have begun exploring this, using telescopes equipped with adaptive optics to search for companions. In some cases, as with Alcor (member of the popular visual binary in the handle of the big dipper), companion stars have been detected, absolving the primary from the expectation of being the cause. However, in other cases, the X-rays still appear to be coming from the primary star when the resolution is sufficient to spatially resolve the system. The conclusion is that either the main star truly is the source, or there are even more elusive, sub-arcsecond binaries skewing the data.

Another new study has taken up the challenge of searching for hidden companions. The new study examined 63 known X-ray stars in the range not predicted to have X-ray emission to search for companions. As a control, they also searched 85 stars without the anomalous emission. This gave a total sample size of 148 target stars. When the images were taken and processed, it uncovered 68 candidate companions to 59 of the total objects. The number of companions was greater than the number of parent stars since some look to exist in trinary star systems or greater.

Comparing the percent of companions around X-ray stars to those that didn’t, 43% of the X-ray stars appeared to have companions, while only 12% of normal stars were discovered to have them. Some of the candidates may be the result of chance alignments and not actual binary systems giving an error of about ±5%.

While this study leaves some cases unresolved, the increased likelihood of X-ray stars to have companions suggests that the majority of cases are caused by companions. Further studies by X-ray telescopes like Chandra could provide the angular resolution necessary to ensure that the emissions are indeed coming from the partner objects as well as search for companions to even greater resolution.