Hubble Spies Cosmic ‘David and Goliath’ in Gravitational Dance

Hubble Spies Cosmic ‘David and Goliath’ in Gravitational Dance

NGC 1512 resides in the southern constellation of Horologium and is roughly 39 million light-years away from Earth.

Also known as ESO 250-4, LEDA 14391 and IRAS 04022-4329, the galaxy spans 70,000 light years, nearly as much as our own Milky Way Galaxy.

It is classified as a barred spiral galaxy, named after the bar composed of stars, gas and dust slicing through its center.

The bar acts as a cosmic funnel, channeling the raw materials required for star formation from the outer ring into the heart of the galaxy.

This pipeline of gas and dust in NGC 1512 fuels intense star birth in the bright, blue, shimmering inner disc known as a circumnuclear starburst ring, which spans 2,400 light-years.

Both the bar and the starburst ring are thought to be at least in part the result of the cosmic scuffle between the two galaxies — a merger that has been going on for 400 million years.

NGC 1512 is also home to a second, more serene, star-forming region in its outer ring.

This ring is dotted with dozens of HII regions, where large swathes of hydrogen gas are subject to intense radiation from nearby, newly formed stars. This radiation causes the gas to glow and creates the bright knots of light seen throughout the ring.

Remarkably, NGC 1512 extends even further than we can see in this image — beyond the outer ring — displaying malformed, tendril-like spiral arms enveloping the elliptical galaxy NGC 1510 (also known as ESO 250-3, LEDA 14375 and IRAS F04018-4332).

These huge arms are thought to be warped by strong gravitational interactions with NGC 1510 and the accretion of material from it.

But these interactions are not just affecting NGC 1512; they have also taken their toll on the smaller of the pair.

The constant tidal tugging from its neighbor has swirled up the gas and dust in NGC 1510 and kick-started star formation that is even more intense than in NGC 1512.

This causes the galaxy to glow with the blue hue that is indicative of hot new stars.

NGC 1510 is not the only galaxy to have experienced the massive gravitational tidal forces of NGC 1512.

Observations made in 2015 showed that the outer regions of the spiral arms of NGC 1512 were indeed once part of a separate, older galaxy. This galaxy was ripped apart and absorbed by NGC 1512, just as it is doing now to NGC 151

Mars-to-Earth-Mass Planet May Lurk in Outer Solar System: Planet 10

Mars-to-Earth-Mass Planet May Lurk in Outer Solar System: Planet 10

In the paper, University of Arizona researchers Dr. Kathryn Volk and Professor Renu Malhotra present compelling evidence of a yet-to-be-discovered planetary body with a mass somewhere between that of Mars and Earth.

The mysterious mass has given away its presence — for now — only by controlling the orbital planes of a population of space rocks known as Kuiper Belt objects (KBOs).

While most KBOs — debris left over from the formation of the Solar System — orbit the Sun with orbital tilts that average out to what planetary scientists call the invariable plane of the Solar System, the most distant KBOs do not.

Their average plane, the authors discovered, is tilted away from the invariable plane by about 8 degrees.

In other words, something unknown is warping the average orbital plane of the outer Solar System.

“The most likely explanation for our results is that there is some unseen mass. According to our calculations, something as massive as Mars would be needed to cause the warp that we measured,” said Dr. Volk, lead author of the study.

The team analyzed the tilt angles of the orbital planes of more than 600 KBOs in order to determine the common direction about which these orbital planes all precess (precession refers to the slow change or ‘wobble’ in the orientation of a rotating object).

“KBOs operate in an analogous way to spinning tops,” Prof. Malhotra explained.

“Imagine you have lots and lots of fast-spinning tops, and you give each one a slight nudge. If you then take a snapshot of them, you will find that their spin axes will be at different orientations, but on average, they will be pointing to the local gravitational field of Earth.”

“We expect each of the KBOs’ orbital tilt angle to be at a different orientation, but on average, they will be pointing perpendicular to the plane determined by the sun and the big planets.”

“If one were to think of the average orbital plane of objects in the outer Solar System as a sheet, it should be quite flat past 50 AU,” Dr. Volk said.

“But going further out from 50 to 80 AU, we found that the average plane actually warps away from the invariable plane. There is a range of uncertainties for the measured warp, but there is not more than 1-2% chance that this warp is merely a statistical fluke of the limited observational sample of KBOs.”

“In other words, the effect is most likely a real signal rather than a statistical fluke.”

According to the calculations, an object with the mass of Mars orbiting roughly 60 AU from the Sun on an orbit tilted by about 8 degrees (to the average plane of the known planets) has sufficient gravitational influence to warp the orbital plane of the distant KBOs within about 10 AU to either side.

“The observed distant KBOs are concentrated in a ring about 30 AU wide and would feel the gravity of such a planetary mass object over time, so hypothesizing one planetary mass to cause the observed warp is not unreasonable across that distance,” Dr. Volk said.

This rules out the possibility that the postulated object in this case could be Planet Nine, predicted to be much more massive (about 10 Earth masses) and much farther out at 500 to 700 AU.

“That is too far away to influence these KBOs. It certainly has to be much closer than 100 AU to substantially affect the KBOs in that range,” Dr. Volk said.

Because a planet, by definition, has to have cleared its orbit of minor planets such as KBOs, the authors refer to the hypothetical mass as a planetary mass object.

The data also do not rule out the possibility that the warp could result from more than one planetary mass object.

“So why haven’t we found it yet? Most likely because we haven’t yet searched the entire sky for distant solar system objects,” the scientists said.

The most likely place a planetary mass object could be hiding would be in the galactic plane, an area so densely packed with stars that solar system surveys tend to avoid it.

“The chance that we have not found such an object of the right brightness and distance simply because of the limitations of the surveys is estimated to be to about 30%,” Dr. Volk said.

A possible alternative to an unseen object that could have ruffled the plane of outer KBOs could be a star that buzzed the Solar System in recent history.

“A passing star would draw all the ‘spinning tops’ in one direction,” Prof. Malhotra said.

“Once the star is gone, all the KBOs will go back to precessing around their previous plane.”

“That would have required an extremely close passage at about 100 AU, and the warp would be erased within 10 million years, so we don’t consider this a likely scenario.”

Hubble Space Telescope Sees ‘Hidden Galaxy’

Hubble Space Telescope Sees ‘Hidden Galaxy’

IC 342 is a spiral galaxy located in the constellation Camelopardalis, approximately 8.9 million light-years away.

The galaxy was discovered in 1895 by British astronomer William Frederick Denning.

Also known as UGC 2847, LEDA 13826 and Caldwell 5, it is one of the brightest galaxies in the IC 342/Maffei group of galaxies.

Although IC 342 is bright, it sits near the equator of the Milky Way’s galactic disc, where the sky is thick with glowing cosmic gas, bright stars, and dark, obscuring dust.

In order for astronomers to see its intricate spiral structure, they must gaze through a large amount of material contained within the Milky Way.

As a result IC 342 is relatively difficult to spot and image, giving rise to its intriguing nickname: the ‘Hidden Galaxy.’

In the Catalogue of Named Galaxies, IC 342 is called Stellivelatus Camelopardalis (star-veiled galaxy).

The galaxy is very active, as indicated by the range of colors visible in this Hubble image, depicting the very central region of the galaxy.

A beautiful mixture of hot, blue star-forming regions, redder, cooler regions of gas, and dark lanes of opaque dust can be seen, all swirling together around a bright core.

In 2003, astronomers confirmed this core to be a specific type of central region known as an HII nucleus — a name that indicates the presence of ionized hydrogen — that is likely to be creating many hot new stars.

The color image of IC 342 was made from separate exposures taken in the visible and UV regions of the spectrum with Hubble’s Wide Field Camera 3(WFC3).

Five filters were used to sample various wavelengths. The color results from assigning different hues to each monochromatic image associated with an individual filter.

Sun is Solar-Type Star After All

Sun is Solar-Type Star After All

The Sun’s activity, including sun-spot activity, levels of radiation and ejection of material, varies on an 11-year cycle, driven by changes in its magnetic field.

Other nearby solar-type stars have their own cycles, but the Sun does not seem to match their behavior.

Understanding the Sun’s cycle is one of the biggest outstanding problems in solar physics.

In a series of simulations of stellar magnetic fields, University of Montreal researcher Antoine Strugarek and co-authors found that the magnetic cycle of the Sun depends on its rotation rate and luminosity.

“This relationship can be expressed in terms of the so-called Rossby number,” they said.

“What we showed is that the Sun’s magnetic cycle is inversely proportional to this number.”

The researchers then compared the results of their simulations with available observations of cyclic activity in a sample of nearby solar-type stars.

They found that the cycle periods of the Sun and other solar-type stars all follow the same relationship with the Rossby number.

“The magnetic field of a star draws its energy from the flows of matter which animate its interior,” the authors explained.

“Thanks to the simulations, we now know that the rotation of the star influences the efficiency of the transfer of energy between these turbulent flows and the magnetic field.”

“The same phenomenon also determines the cycle period, which has been shown to decrease with the Rossby number, a dimensionless number widely used in geophysical fluid dynamics that measures the effects of centrifugal forces.”

“The discovery of such a scaling law for the period of the star magnetic cycle from self-consistent turbulent 3D simulations is a world first.”

The results demonstrate that the Sun is indeed a solar-type star, and also advance scientists’ understanding of how stars generate their magnetic fields.

“These results provide a new theoretical interpretation of stellar magnetic cycles, and place the Sun as the cornerstone of our understanding of the dynamics of stars,” the scientists said.

“By characterizing the magnetism of solar-type stars, our simulations will make it possible in particular to prepare the scientific return of the next European missions Solar Orbiter and PLATO.”

HD 3167d: New Super-Earth Discovered around Nearby Star

HD 3167d: New Super-Earth Discovered around Nearby Star

HD 3167 is a K0-type dwarf star, also designated as EPIC 220383386 and 2MASS J00345752+0422531.

The star has a radius and a mass roughly 86% that of the Sun, and is approximately 8 billion years old.

At a distance of just 149 light-years, HD 3167 is one of the closest and brightest stars hosting multiple transiting planets.

In September 2016, Vanderburg et al announced they had spotted two small, short-period planets — HD 3167b with a period of 0.95 days and HD 3167c with a period of 29.8 days — in orbit around the star.

Assisted by several telescopes and instruments, Christiansen et al confirmed the existence of HD 3167b and HD 3167c planets and discovered additional one, increasing the number of known planets in the system to three.

The newfound planet, named HD 3167d, is a super-Earth with a mass 6.9 times that of our home planet.

It whips around its parent star in just 8.5 days (between the orbits of the previously known planets).

The astronomers also precisely measured radii, masses, and densities of HD 3167b and HD 3167c.

With a mass of 5 Earth-masses and a radius approximately 1.7 times that of Earth’s, HD 3167b is a hot super-Earth with a likely rocky composition.

“The measured mass and radius of HD 3167b indicate a bulk density of 5.6 g/cm3; consistent with a predominantly rocky composition, but potentially having a thin envelope of hydrogen/helium or other low-density volatiles,” Dr. Christiansen and co-authors said.

HD 3167c is a warm sub-Neptune planet. It has a mass 9.8 times that of Earth’s and a radius 3 times that of Earth’s.

“The resulting bulk density of HD 3167c is 1.97 g/cm3. The mass and radius can be explained by a wide range of compositions, all of which include low-density volatiles such as water and hydrogen/helium,” the scientists said.

“HD 3167 promises to be a fruitful system for further study and a preview of the many exciting systems expected from the upcoming NASA TESS mission,” they concluded.

In a separate, independent study of the HD 3167 system, Gandolfi et al also reached the conclusion that HD 3167b is a rocky super-Earth and that HD 3167c is a low-density mini-Neptune.

KELT-11b: ‘Puffy’ Gas Giant Found 320 Light-Years Away

KELT-11b: ‘Puffy’ Gas Giant Found 320 Light-Years Away

KELT-11b is an extreme version of a gas planet, like Solar System’s Jupiter or Saturn, but is orbiting very close to its host star in an orbit that lasts less than 5 days.

“This planet is highly inflated, so that while it’s only a fifth as massive as Jupiter, it is nearly 40% larger, making it about as dense as styrofoam,” said Dr. Pepper, an astronomer and assistant professor of physics at Lehigh University.

“We were very surprised by the amazingly low density of this planet. It’s extremely big for its mass.”

The planet’s host star, KELT-11, is extremely bright, allowing precise measurement of the planet’s atmosphere properties and making it ‘an excellent testbed for measuring the atmospheres of other planets.’

Also known as HD 93396, the host star has started using up its nuclear fuel and is evolving into a red giant, so the planet will be engulfed by the star and not survive the next hundred million years.

KELT-11b was first spotted by the Kilodegree Extremely Little Telescope(KELT) survey, and is described in a study published in the Astronomical Journal ( preprint).

The planet is the third-lowest density exoplanet with a precisely measured mass and radius that has been discovered.

“KELT-11b is one of the most inflated planets known, with an exceptionally large atmospheric scale height (1,717 miles, or 2,763 km), and an associated size of the expected atmospheric transmission signal of 5.6%,” Dr. Pepper and co-authors said.

“These attributes make the KELT-11 system a valuable target for follow-up and atmospheric characterization, and it promises to become one of the benchmark systems for the study of inflated exoplanets.”

Supermassive Black Hole Found 35,000 Light-Years from Home

Supermassive Black Hole Found 35,000 Light-Years from Home

Though several other suspected runaway black holes have been seenelsewhere, none has so far been confirmed.

Now an international team of researchers has detected a supermassive black hole — with a mass of one billion times the Sun’s — being kicked out of its host galaxy.

“We estimate that it took the equivalent energy of 100 million supernovae exploding simultaneously to jettison the black hole,” said co-author Dr. Stefano Bianchi, from the Roma Tre University, Italy.

The images taken by the NASA/ESA Hubble Space Telescope provided the first clue that 3C 186, located 8 billion light-years away, was unusual.

“When I first saw this, I thought we were seeing something very peculiar,” said lead author Dr. Marco Chiaberge, from the Space Telescope Science Institute and Johns Hopkins University.

“When we combined observations from Hubble, Chandra X-ray Observatory, and the Sloan Digital Sky Survey, it all pointed towards the same scenario. The amount of data we collected, from X-rays to ultraviolet to near-infrared light, is definitely larger than for any of the other candidate rogue black holes.”

Hubble images of 3C 186 revealed a bright quasar, the energetic signature of an active black hole, located far from the galactic core.

“Black holes reside in the centers of galaxies, so it’s unusual to see a quasar not in the center,” Dr. Chiaberge said.

The astronomers calculated that the black hole has already traveled about 35,000 light-years from 3C 186’s center, which is more than the distance between the Sun and the center of the Milky Way.

And it continues its flight at a speed of 4.7 million mph (7.5 million km per hour). At this speed the black hole could travel from Earth to the Moon in 3 min.

Although other scenarios to explain the observations cannot be excluded, the most plausible source of the propulsive energy is that this supermassive black hole was given a kick by gravitational waves unleashed by the merger of two massive black holes at the centre of its host galaxy.

This theory is supported by arc-shaped tidal tails identified by the team, produced by a gravitational tug between two colliding galaxies.

According to the team’s theory, 1-2 billion years ago two galaxies — each with central, supermassive black holes – merged.

The black holes whirled around each other at the center of the newly-formed elliptical galaxy, creating gravitational waves that were flung out like water from a lawn sprinkler.

As the two black holes did not have the same mass and rotation rate, they emitted gravitational waves more strongly along one direction.

When the two black holes finally merged, the anisotropic emission of gravitational waves generated a kick that shot the resulting black hole out of the galactic center.

“If our theory is correct, the observations provide strong evidence that supermassive black holes can actually merge,” Dr. Bianchi said.

“There is already evidence of black hole collisions for stellar-mass black holes, but the process regulating supermassive black holes is more complex and not yet completely understood.”

The astronomers now want to secure further observation time with Hubble, in combination with the Atacama Large Millimeter/submillimeter Array and other facilities, to more accurately measure the speed of the black hole and its surrounding gas disc, which may yield further insights into the nature of this rare object.

Astronomers discover rare fossil relic of early Milky Way

Astronomers discover rare fossil relic of early Milky Way

Terzan 5, 19 000 light-years from Earth in the constellation of Sagittarius (the Archer) and in the direction of the galactic centre, has been classified as a globular cluster for the forty-odd years since its detection. Now, an Italian-led team of astronomers have discovered that Terzan 5 is like no other globular cluster known. The team scoured data from the Multi-conjugate Adaptive Optics Demonstrator [1], installed at the Very Large Telescope, as well as from a suite of other ground-based and space telescopes [2]. They found compelling evidence that there are two distinct kinds of stars in Terzan 5 which not only differ in the elements they contain, but have an age-gap of roughly 7 billion years [3].

The ages of the two populations indicate that the star formation process in Terzan 5 was not continuous, but was dominated by two distinct bursts of star formation. “This requires the Terzan 5 ancestor to have large amounts of gas for a second generation of stars and to be quite massive. At least 100 million times the mass of the Sun,” explains Davide Massari, co-author of the study, from INAF, Italy, and the University of Groningen, Netherlands.

Its unusual properties make Terzan 5 the ideal candidate for a living fossil from the early days of the Milky Way. Current theories on galaxy formation assume that vast clumps of gas and stars interacted to form the primordial bulge of the Milky Way, merging and dissolving in the process.

“We think that some remnants of these gaseous clumps could remain relatively undisrupted and keep existing embedded within the galaxy,” explains Francesco Ferraro from the University of Bologna, Italy, and lead author of the study. “Such galactic fossils allow astronomers to reconstruct an important piece of the history of our Milky Way.”

While the properties of Terzan 5 are uncommon for a globular cluster, they are very similar to the stellar population which can be found in the galactic bulge, the tightly packed central region of the Milky Way. These similarities could make Terzan 5 a fossilised relic of galaxy formation, representing one of the earliest building blocks of the Milky Way.

This assumption is strengthened by the original mass of Terzan 5 necessary to create two stellar populations: a mass similar to the huge clumps which are assumed to have formed the bulge during galaxy assembly around 12 billion years ago. Somehow Terzan 5 has managed to survive being disrupted for billions of years, and has been preserved as a remnant of the distant past of the Milky Way.

“Some characteristics of Terzan 5 resemble those detected in the giant clumps we see in star-forming galaxies at high-redshift, suggesting that similar assembling processes occurred in the local and in the distant Universe at the epoch of galaxy formation,” continues Ferraro.

Hence, this discovery paves the way for a better and more complete understanding of galaxy assembly. “Terzan 5 could represent an intriguing link between the local and the distant Universe, a surviving witness of the Galactic bulge assembly process,” explains Ferraro while commenting on the importance of the discovery. The research presents a possible route for astronomers to unravel the mysteries of galaxy formation, and offers an unrivaled view into the complicated history of the Milky Way.

Astronomers Create ‘Image’ of Dark Matter Bridge that Connects Galaxies

Astronomers Create ‘Image’ of Dark Matter Bridge that Connects Galaxies

“For decades, researchers have been predicting the existence of dark-matter filaments between galaxies that act like a web-like superstructure connecting galaxies together,” said Prof. Mike Hudson, from the Department of Physics and Astronomy at the University of Waterloo.

“This image moves us beyond predictions to something we can see and measure.”

Prof. Hudson and his colleague, Seth Epps, used a technique called weak gravitational lensing, an effect that causes the images of distant galaxies to warp slightly under the influence of an unseen mass such as a planet, a black hole, or in this case, dark matter.

The effect was measured in images from a multi-year sky survey at the Canada-France-Hawaii Telescope.

The researchers combined lensing images from more than 23,000 pairs of galaxies located approximately 4.5 billion light-years away to create a composite image that shows the presence of dark matter between the two galaxies.

The results show the dark matter filament bridge is strongest between systems less than 40 million light-years apart.

“By using this technique, we’re not only able to see that these dark matter filaments in the Universe exist, we’re able to see the extent to which these filaments connect galaxies together,” Epps said.

NASA science flights study effect of summer melt on Greenland ice sheet

NASA science flights study effect of summer melt on Greenland ice sheet

Operation IceBridge, NASA’s airborne survey of polar ice, is flying in Greenland for the second time this year, to observe the impact of the summer melt season on the ice sheet. The IceBridge flights, which began on August 27 and will continue until September 16, are mostly repeats of lines that the team flew in early May, so that scientists can observe changes in ice elevation between the spring and late summer. “Earlier in IceBridge’s history, we only surveyed the elevation of these glaciers once a year,” said Joe MacGregor, IceBridge’s deputy project scientist and a glaciologist with NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “But these glaciers experience the climate year-round. Now we’re starting to complete the picture of what happens to them as the year goes on, especially after most of the summer melting has already occurred, so we can measure their cumulative response to that melt.”

The image above, taken during a high-priority flight that IceBridge carried on Aug. 29, shows Helheim Glacier, with its characteristic wishbone-shaped channels, as seen from about 20,000 feet in the sky. Helheim is one of Greenland’s largest and fastest-melting glaciers. During the first week of the summer land ice campaign, IceBridge has also flown over glaciers along Greenland’s northwest, southeast and southwest coasts, and also over lines that the Ice, Cloud, and land Elevation Satellite (ICESat) flew over Greenland during its 2003-2009 period of operations, to observe how ice elevation has evolved since then. Future flights will cover critical areas in central and southern Greenland, such as the world’s fastest glacier, Jakobshavn Isbræ.

For this short, end-of-summer campaign, the IceBridge scientists are flying aboard an HU-25A Guardian aircraft from NASA’s Langley Research Center in Hampton, Virginia. The Guardian is a version of an early-generation Falcon 20 business jet, modified for service with the US Coast Guard and later acquired by NASA. It The plane carries a laser instrument that measures changes in the ice elevation, a high-resolution camera system to image the surface, and an instrument to infer the surface temperature. Due to the Guardian’s limited range, the flights will be shorter (3.5 hours long) than the 8-hour missions carried during IceBridge’s spring Arctic campaign, but the team expects to fly twice a day whenever possible.