Chandra Sees Evidence for Possible Planet in Another Galaxy

M51/Whirpool Galaxy

Credit X-ray: NASA/CXC/SAO/R. DiStefano, et al.; 

Optical: NASA/ESA/STScI/Grendler; 

Illustration: NASA/CXC/M.Weiss

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Astronomers have found evidence for a possible planet candidate in the M51 ("Whirlpool") galaxy, potentially representing what would be the first planet seen to transit a star outside of the Milky Way. As reported in our latest press release, researchers used NASA's Chandra X-ray Observatory to detect the dimming of X-rays from an "X-ray binary", a system where a Sun-like star is in orbit around a neutron star or black hole. The authors interpret this dimming as being a planet passing in front of the neutron star or black hole.

The left panel of this graphic shows M51 in X-rays from Chandra (purple and blue) and optical light from NASA's Hubble Space Telescope (red, green, and blue). A box marks the location of the possible planet candidate, an X-ray binary known as M51-ULS-1. An artist's illustration in the right panel depicts the X-ray binary and possible planet. Material from the companion star (white and blue in illustration) is pulled onto the neutron star or black hole, forming a disk around the dense object (illustrated as red and orange). The material near the dense object becomes superheated, causing it to glow in X-ray light (white). The planet is shown beginning to pass in front of this source of X-rays.

Looking for the dimming of a star's light as something passes in front of it is called the transit technique. For years, scientists have discovered exoplanets using transits with optical light telescopes, which detect the range of light humans can see with their eyes and more. This includes both ground-based telescopes and space-based ones like NASA's Kepler mission. These optical light transit detections require very high levels of sensitivity because the planet is much smaller than the star it passes in front of, and, therefore, only a tiny fraction of the light is blocked.

M51-ULS-1 Transit Only

Animation Credit: NASA/CXC/A.Jubett

The scenario of a transit in an X-ray binary is different. Because a potential planet is close in size to the X-ray source around the neutron star or black hole, a transiting planet passing along Earth's line of sight could temporarily block most or all of the X-rays. This makes it possible to spot transits at greater distances — including beyond the Milky Way — than current optical light studies using transits. A separate graphic shows how X-rays from M51-ULS-1 temporarily decrease to zero during the Chandra observations.

While this is a tantalizing study, the case of an exoplanet in M51 is not ironclad. One challenge is that the planet candidate's large orbit in M51-ULS-1 means it would not cross in front of its binary partner again for about 70 years, thwarting any attempts for a confirming observation for decades. There is also the possibility that the dimming of X-rays is due to a passing cloud of gas near the M51-ULS-1, though the researchers think the data strongly favor the planet explanation.

Illustration Credit: NASA/CXC/M. Weiss

The paper describing these results appears in the latest issue of Nature Astronomy and is available online. The authors are Rosanne DiStefano (CfA), Julia Berndtsson (Princeton), Ryan Urquhart (Michigan State University), Roberto Soria (University of the Chinese Science Academy), Vinay Kashap (CfA), Theron Carmichael (CfA), and Nia Imara (now at the University of California at Santa Cruz). NASA's Marshall Space Flight Center manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science from Cambridge Massachusetts and flight operations from Burlington, Massachusetts.

Quick Look: Chandra Sees Evidence for Possible Planet in Another Galaxy

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Fast Facts for M51/Whirlpool Galaxy:

Scale: Image is about 6 arcmin (49,000 light years) across.
Category: Normal Galaxies & Starburst Galaxies
Constellation: Canes Venatici
Observation Date: 11 pointings between March 2000 and October 2012
Observation Time: 232 hours 10 minutes (9 days 16 hours 10 min)
Obs. ID: 353, 354, 1622, 3932, 13812-13816, 15496, 15553
Instrument: ACIS
Also Known As: NGC 5194, NGC 5195
References: DiStefano, R., et al., 2021, Nature Astronomy (Published); PDF Document
Color Code: X-ray: purple and blue; Optical: red, green, and blue
Distance Estimate: About 28 million light years

Source: NASA's Chandra X-Ray Observatory

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NGC 5195: NASA's Chandra Finds Supermassive Black Hole Burping Nearby

 NGC 5194
Credit  X-ray: NASA/CXC/Univ of Texas/E.Schlegel et al; Optical: NASA/STScI
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 X-ray close-up

  Credit  X-ray: NASA/CXC/Univ of Texas/E.Schlegel et al

Astronomers have used NASA's Chandra X-ray Observatory to discover one of the nearest supermassive black holes to Earth that is currently undergoing powerful outbursts, as described in our latest press release. This galactic burping was found in the Messier 51 galaxy, which is located about 26 million light years from Earth and, contains a large spiral galaxy NGC 5194 (also known by its nickname of the "Whirlpool"), merging with a smaller companion galaxy NGC 5195.

This main panel of this graphic shows M51 in visible light data from the Hubble Space Telescope (red, green, and blue). The box at the top of the image outlines the field of view by Chandra in the latest study, which focuses on the smaller component of M51, NGC 5195. 

The inset to the right shows the details of the Chandra data (blue) of this region. Researchers found a pair of arcs in X-ray emission close to the center of the galaxy, which they interpret as two outbursts from the galaxy's supermassive black hole (mouse over annotated image for additional information). The authors estimate that it took about one to three million years for the inner arc to reach its current position, and three to six million years for the outer arc.

Just outside the outer X-ray arc is a slender region of hydrogen emission detected in an optical image. This suggests that the X-ray emitting gas has "snow-plowed" or swept-up the hydrogen gas from the center of the galaxy. This is a clear case where a supermassive black hole is affecting its host galaxy, in a phenomenon that astronomers called "feedback." 

This arc of hydrogen gas contains what appears to be two or three small "HII regions." An HII (pronounced "H-two") region is created when the radiation from hot, young stars strips away the electrons from neutral hydrogen atoms (HI) to form clouds of ionized hydrogen (HII). This suggests that the outer arc has plowed up enough material to trigger the formation of new stars.

The outbursts of the supermassive black hole in NGC 5195 may have been triggered by the interaction of this galaxy with the large spiral galaxy in M51, causing gas to be disrupted and then funneled down towards the black hole.

These results were presented at the 227th meeting of the American Astronomical Society meeting in Kissimmee, Florida. They are also in a paper submitted to The Astrophysical Journal and the authors are Eric Schlegel (University of Texas at San Antonio), Christine Jones (Harvard-Smithsonian Center for Astrophysics), Marie Marachek (CfA), and Laura Vega (Fisk University and Vanderbilt University Bridge Program).

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, controls Chandra's science and flight operations. Swift is managed by NASA's Goddard Space Flight Center in Greenbelt, Maryland.

Fast Facts for NGC 5195:

Scale: Main image is about 6 x 10 arcmin (About 45,000 x 76,000 light years) Pullout image is 3 arcmin across (about 23,000 light years)
Category: Normal Galaxies & Starburst Galaxies
Coordinates (J2000): RA 13h 29m 59.9s | Dec +47° 15' 58.00"
Constellation: Canes Venatici
Observation Date: 11 pointings between Mar 2000 and Oct 2012
Observation Time: 232 hours 10 min. (9 days 16 hours 10 min)
Obs. ID: 353,354,1622,3932,13812-13816,15496,15553
Instrument: ACIS
References: Schlegel, E. et al, AAS 227, 5-8 Jan 2016
Color Code: X-ray (Blue); Optical (Red, Green, Blue)
Distance Estimate: About 26 million light years

Source: NASA’s Chandra X-ray Observatory

M51: Chandra Captures Galaxy Sparkling in X-rays

M51

Credit X-ray: NASA/CXC/Wesleyan Univ./R.Kilgard, et al; 

Optical: NASA/STScI

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Tour of M51

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Nearly a million seconds of observing time with NASA's Chandra X-ray Observatory has revealed a spiral galaxy similar to the Milky Way glittering with hundreds of X-ray points of light.

The galaxy is officially named Messier 51 (M51) or NGC 5194, but often goes by its nickname of the "Whirlpool Galaxy." Like the Milky Way, the Whirlpool is a spiral galaxy with spectacular arms of stars and dust. M51 is located about 30 million light years from Earth, and its face-on orientation to Earth gives us a perspective that we can never get of our own spiral galactic home.

By using Chandra, astronomers can peer into the Whirlpool to uncover things that can only be detected in X-rays. In this new composite image, Chandra data are shown in purple. Optical data from the Hubble Space Telescope are red, green, and blue.

Most of the X-ray sources are X-ray binaries (XRBs). These systems consist of pairs of objects where a compact star, either a neutron star or, more rarely, a black hole, is capturing material from an orbiting companion star. The infalling material is accelerated by the intense gravitational field of the compact star and heated to millions of degrees, producing a luminous X-ray source. The Chandra observations reveal that at least ten of the XRBs in M51 are bright enough to contain black holes. In eight of these systems the black holes are likely capturing material from companion stars that are much more massive than the Sun.

Because astronomers have been observing M51 for about a decade with Chandra, they have critical information about how X-ray sources containing black holes behave over time. The black holes with massive stellar companions are consistently bright over the ten years of Chandra observations. These results suggest that the high-mass stars in these X-ray sources also have strong winds that allow for a steady stream of material to flow onto the black hole.

A difference between the Milky Way and the Whirlpool galaxy is that M51 is in the midst of merging with a smaller companion galaxy seen in the upper left of the image. Scientists think this galactic interaction is triggering waves of star formation. The most massive of the newly formed stars will race through their evolution in a few million years and collapse to form neutron stars or black holes. Most of the XRBs containing black holes in M51 are located close to regions where stars are forming, showing their connection to the oncoming galactic collision.

Previous studies of the Whirlpool Galaxy with Chandra revealed just over 100 X-ray sources. The new dataset, equivalent to about 900,000 seconds of Chandra observing time, reveals nearly 500 X-ray sources. About 400 of these sources are thought to be within M51, with the remaining either being in front of or behind the galaxy itself.

Much of the diffuse, or fuzzy, X-ray emission in M51 comes from gas that has been superheated by supernova explosions of massive stars.

The new Chandra observations were presented at the 224th meeting of the American Astronomical Society in Boston, Mass. by Roy Kilgard of Wesleyan University in Middletown, Conn. NASA's Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA's Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory in Cambridge, Mass., controls Chandra's science and flight operations.

Fast Facts for Whirlpool Galaxy: 
 
Scale: Image is about 6 x 10 arcmin (About 52,000 x 87,000 light years) 
Category: Normal Galaxies & Starburst Galaxies
Coordinates (J2000): RA 13h 29m 55.7s | Dec +47° 13' 53" 
Constellation: Canes Venatici
Observation Date: 11 pointings between Mar 2000 and Oct 2012 
Observation Time: 232 hours 10 min (9 days 16 hours 10 min). 
Obs. ID: 353,354,1622,3932,13812-13816,15496,15553 
Instrument: ACIS
Also Known As: NGC 5194, NGC 5195 
References: Kilgard, R. et al, AAS 224, 1-5 June 2014 
Color Code: X-ray (Purple); Optical (Red, Green, Blue) 
Distance Estimate: About 30 million light years 

Source: NASA’s Chandra X-ray Observatory

The whirl of stellar life

M51 or NGC 5194

Copyright: ESA / Herschel / XMM-Newton. Acknowledgements: "Physical Processes in the Interstellar Medium of Very Nearby Galaxies" Key Programme, Christine Wilson

The Whirlpool Galaxy, also known as M51 or NGC 5194, is one of the most spectacular examples of a spiral galaxy. With two spiral arms curling into one another in a billowing swirl, this galaxy hosts over a hundred billion stars and is currently merging with its companion, the smaller galaxy NGC 5195.

Around 30 million light-years away, the Whirlpool Galaxy is close enough to be easily spotted even with binoculars. Using the best telescopes available both on the ground and in space, astronomers can scrutinise its population of stars in extraordinary detail.

In this image, observations performed at three different wavelengths with ESA’s Herschel and XMM-Newton space telescopes are combined to reveal how three generations of stars coexist in the Whirlpool Galaxy.

The infrared light collected by Herschel – shown in red and yellow – reveals the glow of cosmic dust, which is a minor but crucial ingredient in the interstellar material in the galaxy’s spiral arms. This mixture of gas and dust provides the raw material from which the Whirlpool Galaxy’s future generations of stars will take shape.

Observing in visible and ultraviolet light, astronomers can see the current population of stars in the Whirlpool Galaxy, since stars in their prime shine most brightly at shorter wavelengths than infrared. Seen at ultraviolet wavelengths with XMM-Newton and portrayed in green in this composite image are the galaxy’s fiercest stellar inhabitants: young and massive stars pouring powerful winds and radiation into their surroundings.

The image also shows the remains of previous stellar generations, which shine brightly in X-rays and were detected by XMM-Newton. Shown in blue, these sources of X-rays are either the sites where massive stars exploded as supernovae in the past several thousand years, or binary systems that host neutron stars or black holes, the compact objects left behind by supernovae.

 Source: ESA - Space Images

IN A STAR’S FINAL DAYS, ASTRONOMERS HUNT “SIGNAL OF IMPENDING DOOM”

A Large Binocular Telescope image which shows the supernova in M51 is available here for the media.

COLUMBUS, Ohio – An otherwise nondescript binary star system in the Whirlpool Galaxy has brought astronomers tantalizingly close to their goal of observing a star just before it goes supernova.

The study, submitted in a paper to the Astrophysical Journal, provides the latest result from an Ohio State University galaxy survey underway with the Large Binocular Telescope, located in Arizona.

In the first survey of its kind, the researchers have been scanning 25 nearby galaxies for stars that brighten and dim in unusual ways, in order to catch a few that are about to meet their end. In the three years since the study began, this particular unnamed binary system in the Whirlpool Galaxy was the first among the stars they’ve cataloged to produce a supernova.

The astronomers were trying to find out if there are patterns of brightening or dimming that herald the end of a star’s life. Instead, they saw one star in this binary system dim noticeably before the other one exploded in a supernova during the summer of 2011.

Though they’re still sorting through the data, it’s likely that they didn’t get any direct observations of the star that exploded – only its much brighter partner.

Yet, principal investigator Christopher Kochanek, professor of astronomy at Ohio State and the Ohio Eminent Scholar in Observational Cosmology, does not regard this first result as a disappointment. Rather, it’s a proof of concept.

“Our underlying goal is to look for any kind of signature behavior that will enable us to identify stars before they explode,” he said. “It’s a speculative goal at this point, but at least now we know that it’s possible.”

“Maybe stars give off a clear signal of impending doom, maybe they don’t,” said study co-author Krzystof Stanek, professor of astronomy at Ohio State, “But we’ll learn something new about dying stars no matter the outcome.”

Postdoctoral researcher Dorota Szczygiel, who led the study of this supernova, explained why the galaxy survey is important.

“The odds are extremely low that we would just happen to be observing a star for several years before it went supernova. We would have to be extremely lucky,” she said.

“With this galaxy survey, we’re making our own luck. We’re studying all the variable stars in 25 galaxies, so that when one of them happens go supernova, we’ve already compiled data on it.”
The supernova, labeled 2011dh, was first detected on May 31 and is still visible in telescopes. It originated from a binary star system in the Whirlpool Galaxy – also known as M51, one of the galaxies that the Ohio State astronomers have been observing for three years.

The system is believed to have contained one very bright blue star and one even brighter red star. From what the astronomers can tell, it’s likely that the red star is the one that dimmed over the three years, before the blue star initiated the supernova.

When the Ohio State researchers reviewed the Large Binocular Telescope data as well as Hubble Space Telescope images of M51, they saw that the red star had dimmed by about 10 percent over three years, at a pace of three percent per year.

Szczygiel believes that the red star likely survived its partner’s supernova.

“After the light from the explosion fades away, we should be able to see the companion that did not explode,” she said.

As astronomers gather data from more supernovae – Kochanek speculates that as many as one per year could emerge from their data set – they could assemble a kind of litmus test to predict whether a particular star is near death. Whether it’s going to spawn a supernova or shrink into a black hole, there may be particular signals visible on the surface, and this study has shown that those signals are detectable.

The team won’t be watching our sun for any changes, however. At less than 10 percent of the mass of the star in supernova 2011dh, our star will most likely meet a very boring end.

“There’ll be no supernova for our sun – it’ll just fizzle out,” Kochanek said. “But that’s okay – you don’t want to live around an exciting star.”

This research was supported by the National Science Foundation.

The Large Binocular Telescope is an international collaboration among institutions in the United Sates, Italy, and Germany. The LBT Corporation partners are: the University of Arizona on behalf of the Arizona University System; the Instituto nazionale di Astrofisica, Italy; the LBT Beteiligungsesellschaft, Germany, representing the Max Planck Society, the Astrophysical Institute of Potsdam, and Heidelberg University; the Ohio State University; and the Research Corporation, on behalf of the University of Notre Dame, University of Minnesota, and University of Virginia.

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Contact:

Christopher Kochanek, (614) 292-5954; Kochanek.1@osu.edu
Dorota Szczygiel, (614) 688-7426; Szczygiel.3@osu.edu

Written by Pam Frost Gorder, (614) 292-9475; Gorder.1@osu.edu