Category Archives: Astronomy

The remnant of supernova 1987a, located in the Large Magellanic Cloud some 165,000 light years away.... [+] When they reach peak brightness, a type II (core-collapse) supernova will be more than twice as bright as a type Ia supernova ever will be, and will emit both neutrinos and light simultaneously, but that interact differently with their environment and hence arrive at different times.

On February 24, 1987, a spectacular signal was seen as never before. From 165,000 light-years away, the first signals from a recently destroyed star a core-collapse supernova arrived on Earth. Humans had witnessed supernovae before, both within the Milky Way and in galaxies beyond our own, but this one was special. The first hint of its arrival didn't come in the form of light, but rather in a signal never measured before: in the form of neutrinos.

It wasn't until hours later that the light arrived, corresponding to the extra time it took the shock wave occurring in the star's interior to reach the surface. Whereas light interacts with the material composing the progenitor star, neutrinos simply pass right through it, giving them a significant head start. For the first time, an astronomical event beyond our Solar System had emitted both light and particles that were observed on Earth. The era of Multi-Messenger Astronomy was born. Although it's still a term that few non-astronomers are familiar with, it truly is the future of studying the Universe.

Multiple neutrino events, reconstructed from separate neutrino detectors. In 1987, three independent... [+] detectors that were sensitive to energetic neutrinos and antineutrinos detected a total of 25 particles in a single burst spanning 13 seconds. A few hours later, the light arrived as well.

Originally, astronomy was confined to a very narrow regime: the only signals we were capable of receiving were in the form of visible light. Since that's what our eyes had adapted to see, those were the tools we had at our disposal to examine the Universe. For countless millennia, human eyes viewed the Sun, Moon, planets, stars, and the fuzzy, distant nebulae we now know to be galaxies as they slowly but surely migrated across the sky.

Even after the invention of the telescope, astronomy was still confined to what we could perceive in visible light. All the telescope did, essentially, was to enhance our light-gathering power by using mirrors and/or lenses to increase the light-collecting area far beyond the limits of even the most thoroughly dilated pupil. Instead of thousands of stars, these tools would reveal hundreds of thousands, millions, and eventually billions of them.

A map of star density in the Milky Way and surrounding sky, clearly showing the Milky Way, the Large... [+] and Small Magellanic Clouds (our two largest satellite galaxies), and if you look more closely, NGC 104 to the left of the SMC, NGC 6205 slightly above and to the left of the galactic core, and NGC 7078 slightly below. In visible light, only starlight and the presence of light-blocking dust is revealed, but other wavelengths have the capacity to reveal fascinating and informative structures far beyond what the optical part of the spectrum can.

Early on, only the brightest objects appeared to have color features; the others were so far away that only monochrome signals were perceptible.When photographic techniques became available and were applied to astronomy, however, it became possible toplace a color filter over the telescope, recording only light of a particular wavelength.

When multiple different wavelengths were sampled either at once or in rapid succession, the data that was collected could be combined to form a single color image. This technique was originally applied to terrestrial images, but was extended to astronomy in short order, enabling scientists to produce color images of objects in the night sky. Even today, the field of astrophotography is enjoyed by not only professionals, but tens of thousands of amateurs and hobbyists from across the world.

By taking three different photographs of the same object that collect data at three different... [+] wavelengths, colors (like red, green, and blue) can be assigned and added together, producing an image that looks true-to-life and in real color to our eyes. Astronomers not only use this technique, but have extended it to beyond the limits of our eyes by implementing multi-wavelength astronomy.

Still, this advance only leveraged the tiniest portion of the electromagnetic spectrum: visible light. In reality, there are many forms of light that are both higher in energy (and shorter in wavelength) as well as lower in energy (with longer wavelengths) that can be perceived and measured by the right type of telescope.

Today, we take advantage of all the different forms of light that there are to study the objects present in the Universe.

Whenever we look at an object in a different wavelength of light, we have the potential to reveal an entirely new class of information about it.

This multi-wavelength view of the nearby Andromeda galaxy shows what is revealed in radio, infrared,... [+] visible, ultraviolet, and X-ray light. Gas, dust, stars, and stellar remnants that emit light in different energies and at different temperatures can all be highlighted, dependent on which wavelength is chosen.

Even though we have different names for these various types of astronomical observing some of what we observe are rays (gamma-rays and X-rays), some are light (ultraviolet and visible), some are radiation (infrared) and some are waves (radio) they're all still light. From a physics point of view, we're collecting the same thing: photons, or quanta of light. We're just looking at light with different properties when we're doing any of these types of astronomy.

In other words, doing astronomy by collecting light of any type always involves the same type of messenger: the same type of information-carrier. However, there are other forms of astronomy, too, because the objects in the Universe doesn't just emit light. As they undergo all the various astrophysical processes that the Universe allows, they can emit a wide variety of classes of signal, including from fundamentally different messengers.

Cosmic rays, which are ultra-high energy particles originating from all over the Universe, strike... [+] protons in the upper atmosphere and produce showers of new particles. The fast-moving charged particles also emit light due to Cherenkov radiation as they move faster than the speed of light in Earth's atmosphere, and produce secondary particles that can be detected here on Earth.

Numerous classes of objects don't merely emit light, but also particles. From all over the sky, including from the Sun, we detect a wide variety of cosmic ray particles, including:

We've been collecting these types of particles from within the Solar System for extremely long periods of time, as arguably every time we encounter a meteor shower, we're witnessing particle showers in our atmosphere originating from past-and-present comets. The Sun emits a wide variety of cosmic rays. And recently, with sophisticated observatories like Kamiokande (and its successors) and IceCube, we're detecting both solar and cosmic neutrinos.

The Super-Kamiokande detector, the successor to the neutrino observatory responsive for 12 of the 25... [+] neutrinos seen in the nearby 1987 supernova, was able to produce this image of the Sun from the solar neutrinos alone.

Light and particles are each a completely independent type of "messenger" in astronomy, as they require fundamentally different techniques, equipment, and interpretations in order to make sense of the Universe. But the 2010s brought us something even more remarkable: a third type of fundamental messenger. On September 14, 2015, the first new signal arrived: in the form of gravitational waves.

Gravitational waves are the only signal ever directly detected that has no type of known, measured, Standard Model particle associated with it. They are generated whenever a massaccelerates through a region of space that changes in its curvature, but it's only the strongest, largest-amplitude signals of a specific frequency that we're able to detect. Using a large, extraordinarily precise laser interferometer, scientists are able to detect gravitational waves that correspond to a change in those arm lengths of no more than 10-19 meters: about 1/10,000th the width of a proton.

The LIGO Hanford Observatory for detecting gravitational waves in Washington State, USA, relies on... [+] two perpendicular, 4 km arms with lasers inside them to detect the passage of gravitational waves. When a wave passes through, one arm will contract while the other expands and vice versa, creating an oscillatory signal with an amplitude of just ~10^-19 meters.

With three fundamentally different types of astronomy, we've gained new windows on the Universe and new methods of gaining information about all that's out there. Light, particles, and gravitational waves are intrinstically different types of messengers for astronomers, with each class of signal revealing information about the Universe that the other two cannot.

But the most powerful examples of these various astronomical techniques occur when we're able to use more than one of them at the same time. When astronomers use the term "Multi-Messenger Astronomy," this is the key concept they're referring to: detecting the same object or event with either light and particles, light and gravitational waves, particles and gravitational waves, or all three together. As the sciences of traditional (light-based) astronomy, gravitational wave astronomy, and cosmic ray astronomy all advance, these multi-messenger events will reveal the Universe as never before.

Artists illustration of two merging neutron stars. The rippling spacetime grid represents... [+] gravitational waves emitted from the collision, while the narrow beams are the jets of gamma rays that shoot out just seconds after the gravitational waves (detected as a gamma-ray burst by astronomers). The aftermath of the neutron star merger observed in 2017 points towards the creation of a black hole.

In 2017, gravitational wave astronomers observed a signal unlike any other, which wound up corresponding to the merger of two neutron stars some 130 million light-years away. Almost simultaneously just two seconds after the gravitational wave signal ceased the first electromagnetic signal (in the form of gamma-rays) arrived. The first robust multi-messenger signal involving gravitational waves had been detected.

This is only going to get better with time and improved technology. When the next nearby supernova occurs, we'll certainly be able to detect both light and particles, and might even get gravitational waves, too. In fact, we had a candidate (that didn't pan out) for our first trifecta signal earlier this year. When a pulsar glitch is picked up by a gravitational wave detector, it will also be a multi-messenger signal. And when LISA, our next-generation gravitational wave detector comes online, we'll even be able to predict these cosmic mergers that LIGO and Virgo see today well in advance, giving ourselves plenty of lead time to make simultaneous observations of a possible multi-messenger event at that critical, "t=0" moment.

The primary scientific goal of the Laser Interferometer Space Antenna (LISA) mission is to detect... [+] and observe gravitational waves from massive black holes and galactic binaries with periods in the range of a tens of seconds to a few hours. This low-frequency range is inaccessible to ground-based interferometers because of the unshieldable background of local gravitational noise arising from atmospheric effects and seismic activity. Its arrival could herald a new, monumental advance in multi-messenger astronomy.

The three types of signals we know how to collect from the Universe light, particles, and gravitational waves all deliver fundamentally different types of information right to our front door. By combining the most precise observations we can take with each of these, we can learn more about our cosmic history than any one of these signal types, or "messengers," can provide in isolation.

We've already learned how neutrinos are produced in supernova, and how their travel path is less impeded by matter than light's is. We've already linked merging neutron stars with kilonovae and the production of the heaviest elements in the Universe. With multi-messenger astronomy still in its infancy, we can expect a deluge of new events and new discoveries as this science progresses throughout the 21st century.

Just as you can learn more about a tiger by hearing its growl, smelling its scent, and watching it hunt than you can from a still image alone, you can learn more about the Universe by detecting these fundamentally different types of messengers all at once. Our bodies might be limited in terms of the senses we can use in any given scenario, but our knowledge of the Universe is limited only by the fundamental physics governing it. In the quest to learn it all, we owe it to humanity to use every resource we can muster.

See the original post here:

This Is Why 'Multi-Messenger Astronomy' Is The Future Of Astrophysics - Forbes

Friday, November 15Venus and Jupiter hang low in the southwest after sunset this week. Venus, which shines at magnitude 3.9, stands 5 above the horizon 45 minutes after sunset. Jupiter glows two magnitudes fainter than Venus and lies 9 to its neighbors upper left, or about the span of your closed fist when held at arms length. If you track the two this week, youll notice that they appear to be on a collision course. The gap between the planets narrows by 1 each day, setting up a dramatic conjunction at the end of next week.

Saturday, November 16Although asteroid 4 Vesta reached opposition and peak visibility the night of November 11/12, the Full Moon was only a few degrees away that night and made finding the magnitude 6.5 space rock a serious challenge. Now that the Moon has moved well away and Vesta shines just as brightly as it did at opposition locating the asteroid through binoculars should prove much easier. The brightest asteroid lies in northeastern Cetus tonight, 3 west of the 4th-magnitude star Omicron () Tauri and 5 northeast of 3rd-magnitude Alpha () Ceti.

Sunday, November 17The Leonid meteor shower reaches its peak before dawn tomorrow morning. Although typically one of the years finer meteor showers, this years Leonid display suffers because it comes just a few days after Full Moon. A 65-percent-lit waning gibbous Moon shares the sky with the shower, drowning out the fainter shooting stars and rendering the brighter ones less impressive. Still, the Leonids produce more fireballs than most meteor showers, so it is still worth keeping an eye on the predawn sky.

Monday, November 18Uranus reached opposition and peak visibility three weeks ago, and it remains a tempting target all this week. The outer planet appears in the eastern sky after darkness falls and climbs highest in the south around 10 p.m. local time. The magnitude 5.7 world lies in southeastern Aries the Ram, near that constellations border with Pisces the Fish and Cetus the Whale. Although Uranus shines brightly enough to glimpse with the naked eye under a dark sky, use binoculars to locate it initially. The closest guide star is magnitude 4.4 Xi1 (1) Ceti, which lies 3.8 to the south-southeast. A telescope reveals the planets 3.7"-diameter, blue-green disk.

Tuesday, November 19Last Quarter Moon arrives at 4:11 p.m. EST. It rises in the eastern sky shortly before midnight local time and reaches its peak in the south around sunrise tomorrow morning, by which time it appears slightly less than half-lit. Our satellite resides among the background stars of Leo throughout this period, roughly 5 from the Lions brightest star, 1st-magnitude Regulus.

Original post:

The Sky This Week from November 15 to 24 - Astronomy Magazine

Thousands of SkiesSo far, astronomers have discovered thousands of exoplanets that pass in front of their stars from our point of view. With the right tools, astronomers can study light from the host stars that pass through the planets atmospheres. This can reveal information like the chemical makeup and temperatures of these atmospheres as well as what chemical reactions are taking place there.

The James Webb Space Telescope, currently scheduled to launch in 2021, will be able to study exoplanet atmospheres. But since JWST will split its time between multiple projects, it will only focus on studying the atmospheres of a few exoplanets. ARIEL, however, will observe the skies of about 1,000 exoplanets, from rocky planets to Jupiter-like gas giants.

Im really looking forward to the ability to place individual planets within a statistical context, says Mark Swain, an astrophysicist at NASAs Jet Propulsion Laboratory who is heading production of the CASE instrument. That is something which you need a large survey of exoplanets to do.

Understanding whether an exoplanet has clouds or hazes will help astronomers better interpret other information about the planets atmosphere, like chemical makeup and temperature, and figure out what physical and chemical processes are happening.

Also, understanding chemical compositions of exoplanet atmospheres might help decide which of two leading theories for how planets form is most likely correct. One theory suggests that planets will tend to have similar fractions of heavy elements as their host stars, while another implies that the heavy element fractions could be quite different.

Finally, studying the atmospheres of 1,000 planets should help astronomers find out whats typical and pick out interesting cases to delve into.

When we see a single planet, a big question is, Is this kind of like the others, or did something special happen here? Swain says. And thats a fundamental capability that ARIEL is going to give us.

Read the original post:

This spacecraft will detect if exoplanet skies are cloudy, hazy, or c - Astronomy Magazine

The mission

AMS-02 came to the ISS in 2011 on the space shuttle Endeavour. After it was attached to the outside of the ISS, operators planned was to run the experiment for only three years. But eight years later, the instrument is still operational but is in dire need of repairs.

AMS-02 is designed to search for antimatter and dark matter, allowing physicists to learn more about these mysterious substances. Since its installation, the instrument has challenged current thinking about physics as scientists analyze the cosmic particles it processes.

The instruments cooling pumps, which are essential for AMS-02 to continue running, have been failing for a few years now. When the pumps started to malfunction, engineers at NASA knew they needed to come up with a plan to fix them.

After four years, the repair plan is finally ready.

Were all very excited to stop talking about it and start executing, said Kenny Todd, the manager of International Space Station Operations Integration, at the press briefing on November 12.

Currently, the team is planning on four spacewalks to repair the pumps and upgrade AMS-02, but because of the complex nature of the tast, the last two have not been scheduled yet and a fifth excursion could be added.

During the first walk on Friday, Parmitano and Drew will be doing prep work for the upcoming excusrions, including adding handles on the outside of the ISS for stability when performing the walks and removing the debris shield thats currently protecting the instrument.

The next walk will be on November 22, but the real work on repairing AMS-02 wont begin until the third or fourth spacewalk.

One of the biggest challenges of repairing AMS-02 is that it wasnt designed to be repaired. Because of the expected three-year life span of the instrument, the initial design wasnt created with consideration for fitting spacesuit gloves into the instrument. Other devices, such as the Hubble Space Telescope, have been designed with the intention of astronauts fixing it from inside space suits.

To overcome a lot of these challenges, teams of engineers have been working to create tools and ways for the astronauts to work around the sharp corners of the instrument. They reached out to college programs as well, encouraging student engineers to design a tool that will help the astronauts cut zip ties inside AMS-02 and retrieve them safely in zero gravity.

Both Parmitano and Drew have been performing test repairs with the tools and NASA officials stated in the press briefing that they feel confident in the astronauts abilities to complete the task at hand.

The schedule for the spacewalks also brings challenges. Boeing will be performing orbital tests of their uncrewed capsule, Starliner, at the beginning of December. This could hit pause on the spacewalks as the crew turns their attention to the Starliner tests. Plus, on December 7, a SpaceX Cargo Dragon will be making a resupply run to the ISS, taking even more time away from the walks.

Here is the original post:

Watch live: Spacewalks to fix important Space Station instrument - Astronomy Magazine

Astronomers have measured the rotation of 1,418 galaxies and found that small ones are likely to spin on a different axis to large ones. The rotation was measured in relation to each galaxys closest cosmic filament.

This is a simulation showing a section of the Universe at its broadest scale; a web of cosmic filaments forms a lattice of matter, enclosing vast voids. Image credit: Greg Poole / Tiamat Simulation.

Cosmic filaments are massive thread-like formations, comprising huge amounts of matter, including galaxies, gas and dark matter.

They can be 500 million light-years long but just 20 million light-years wide.

At their largest scale, they divide the Universe into a vast gravitationally linked lattice interspersed with enormous dark matter voids.

The spine of cosmic filaments is pretty much the highway of galactic migration, with many galaxies encountering and merging along the way, said Dr. Charlotte Welker, a researcher at McMaster University, the ARC Centre of Excellence for Astrophysics in 3 Dimensions (ASTRO 3D) and ICRAR.

Using data gathered by the Sydney-AAO Multi-object Integral-field spectrograph (SAMI) at the Anglo-Australian Telescope, Dr. Welker and colleagues studied each of the target galaxies and measured its spin in relation to its nearest filament.

They found that smaller ones tended to rotate in direct alignment to the filaments, while larger ones turned at right angles.

The alignment changes from the first to the second as galaxies, drawn by gravity towards the spine of a filament, collide and merge with others, thus gaining mass.

The flip can be sudden. Merging with another galaxy can be all it takes, Dr. Welker said.

The result offers insight into the deep structure of the Universe, said Dr. Scott Croom, an ASTRO 3D principal investigator from the University of Sydney.

Virtually all galaxies rotate, and this rotation is fundamental to how galaxies form.

For example, most galaxies are in flat rotating disks, like our Milky Way. Our result is helping us to understand how that galactic rotation builds up across cosmic time.

The Milky Way, by the way, has a spin well aligned with its nearest cosmic filament, but belongs to a class of intermediate size galaxies that, over all, show no clear tendency towards parallel or perpendicular spins.

The findings were published in the Monthly Notices of the Royal Astronomical Society.

_____

C. Welker et al. The SAMI Galaxy Survey: First detection of a transition in spin orientation with respect to cosmic filaments in the stellar kinematics of galaxies. MNRAS, published online October 12, 2019; doi: 10.1093/mnras/stz2860

See original here:

Study: Direction in Which Galaxies Spin Depends on Their Mass | Astronomy - Sci-News.com

If there was a wormhole in the center of our galaxy, how could we tell? Two physicists propose that carefully watching the motions of a star orbiting the Milky Way's supermassive black hole might help scientists start to check. The researchers published the idea in a recent paper in the journal Physical Review D.

A wormhole is a hypothetical concept that connects two separate areas of space-time. Wormholes often appear in science fiction narratives like the 2014 film Interstellar as a convenient way to get from point A to point B in the vast universe. Physicists have many theories that describe how wormholes might behave, if they exist, but havent yet found any.

Traversing a wormhole

De-Chang Dai of Yangzhou University in China and Dejan Stojkovic of the University at Buffalo decided to tackle the question of how scientists might test whether a wormhole exists in the center of the Milky Way.

For this to be possible, the wormhole would have to be traversable. In this type of wormhole, space-time curves dramatically from either side of the wormhole to meet at a narrow mouth in the middle, which contains a black hole (such as, for example, the supermassive black hole in the center of the Milky Way).

A traversable wormhole allows information from one side, like light or the influence of gravity, to pass through to the other side.This is the key to the physicists proposal for checking whether theres a wormhole at the center of the Milky Way. If a wormhole connects the center of our galaxy to another distant region of the universe, objects close to our side of the wormhole would feel the gravitational pull of objects on the other side of the wormhole.

Tiny changes in gravity

The two researchers calculated that a star a few times the mass of our Sun orbiting on the other side of the hypothetical wormhole could affect the orbit of S2, a star that orbits close to our galaxys central black hole. The effect would be small, enacting a change in the expected gravitational acceleration of S2 that's about 10 million times weaker than the strength of gravity on Earth. With all the observations astronomers currently have of the star S2, they can only detect changes down to about 100 times that size.

So, the capabilities aren't quite there, but its not crazy far, says Stojkovic. With more observations of S2, he says, it might be possible to detect changes that tiny in a decade or so, if they exist.

The caveat is that just seeing a gravitational acceleration that small cant confirm whether the effect came through a wormhole or not. The effect could come from some object in the Milky Way (on our side of this hypothetical wormhole). If scientists do ever measure such a minute change in gravity on S2, theyll need to do a lot of modeling to understand where the gravitational effect could be coming from. If they can rule out all other possibilities that are more likely, Stojkovic says, then it might be a wormhole.

See original here:

How could we find a wormhole hiding in the Milky Way? - Astronomy Magazine

The full suite of what's present today in the Universe owes its origins to the hot Big Bang. More... [+] fundamentally, the Universe we have today can only come about because of the properties of spacetime and the laws of physics. Although the Universe is expanding, the total amount of Universe we can observe is increasing, too.

If you want to understand what the Universe is made of, what its fate is, or how long ago the Big Bang occurred, there are just two pieces of information you need. According to the science of physical cosmology, all you need to measure is:

and that information allows you to reconstruct the Universe's composition, history, and evolution as far into the future as you like.

Up until now, there's been a tremendous amount of controversy surrounding all of these issues, as different teams using different methods arrive at different answers. But they all have one thing in common: all of their measurements rely only on indirect methods of determining how the Universe has expanded over time. But with a new generation of telescopes arriving in the 2020s, astronomers will at last gain the capability to measure the expansion rate directly. Here's the incredible science behind it.

An ultra-distant view of the Universe shows galaxies moving away from us at extreme speeds. At those... [+] distances, galaxies appear more numerous, smaller, less evolved, and to recede at great redshifts compared to the ones nearby.

In an expanding Universe, the light that a distant galaxy emits will appear different than the light received by a faraway observer. At any particular instant, the light emitted by stars and galaxies will have certain properties. In particular, that light will behave like it's a sum of many different blackbodies the way perfectly dark objects radiate when they're heated to a certain temperature superimposed atop one another.

If this were the only light the Universe gave us to observe, measuring how the Universe expands would be extremely challenging. Even if we discovered clever methods to measure the distances to these far-flung objects, we still wouldn't be able to accurately measure the effects of the expanding Universe. As the Universe expands, the emitted light stretches as it travel from the source to the observer, but without knowing the intrinsic properties of that light, we couldn't measure the amount of stretching to any reasonable precision.

The farther a galaxy is, the faster it expands away from us and the more its light appears... [+] redshifted. A galaxy moving with the expanding Universe will be even a greater number of light years away, today, than the number of years (multiplied by the speed of light) that it took the light emitted from it to reach us. But we can only understand redshifts and blueshifts if we attribute them to a combination of motion (special relativistic) and the expanding fabric of space (general relativistic) contributions both.

Fortunately, our Universe isn't simply composed of stars and galaxies that radiate at a specific temperature; it's also made of atoms. Atoms have the spectacular property that they only absorb or emit radiation of extraordinarily specific wavelengths: wavelengths that correspond to the atomic and molecular transitions inherent to those specific atoms.

By taking the light from all objects, from our Sun to nearby stars to even the most distant galaxies and quasars, we can identify those absorption and emission features caused by the atoms within those objects. There are two effects the motion of the light source relative to the observer and the expansion of space over the course of the light's journey that combine to determine the amount that the distant light shifts by over the time that it travels to our instruments.

First noted by Vesto Slipher back in 1917, some of the objects we observe show the spectral... [+] signatures of absorption or emission of particular atoms, ions, or molecules, but with a systematic shift towards either the red or blue end of the light spectrum. When combined with the distance measurements of Hubble, this data gave rise to the initial idea of the expanding Universe: the farther away a galaxy is, the greater its light is redshifted.

By combining distance measurements with redshift measurements, we can reconstruct the expansion of the Universe. That's one of the major classes of methods used to measure how quickly the Universe expands, and it encompasses all sorts of different ways to measure the distance to a variety of objects.

When we combine all the data from the full suite of objects we can reliably measure both distances and redshifts to, we come up withsome very tight constraints on how the Universe has expanded over time. Because matter and radiation dilute in specific fashions as the Universe expands, while dark energy remains indistinguishable from a cosmological constant (with a constant energy density), we can use all of the information, combined, to learn what the Universe is made of, how fast it's expanding today, and how that expansion rate has evolved over time.

A plot of the apparent expansion rate (y-axis) vs. distance (x-axis) is consistent with a Universe... [+] that expanded faster in the past, but where distant galaxies are accelerating in their recession today. This is a modern version of, extending thousands of times farther than, Hubble's original work. Note the fact that the points do not form a straight line, indicating the expansion rate's change over time. The fact that the Universe follows the curve it does is indicative of the presence, and late-time dominance, of dark energy.

It's a monumental achievement for cosmology, and has given us answers (albeit, with uncertainties and controversies associated with them) to all of these questions to unprecedented precision. However, there's only so much confidence one can have in these indirect measurements. In astronomy, the objects we see are often so far away and so grand in scale that, on human timescales, we have no way to measure how they change in real-time.

If the fabric of space is like a ball of dough, and the individual galaxies within the Universe are like raisins, then the expanding Universe is like the dough when it leavens. The raisins (galaxies) all appear to move away from one another, with more distant raisins (galaxies) appearing to recede more quickly. But this observation is primarily due to the fact that the dough (Universe) is expanding. The raisins (galaxies) are actually stationary with respect to their local position; it's just that the dough (space) between them is expanding over time.

The 'raisin bread' model of the expanding Universe, where relative distances increase as the space... [+] (dough) expands. The farther away any two raisin are from one another, the greater the observed redshift will be by time the light is received. The redshift-distance relation predicted by the expanding Universe is borne out in observations, and has been consistent with what's been known all the way back since the 1920s.

This is why, by measuring the redshifts and distances to a slew of objects objects at a variety of different distances and redshifts we can reconstruct the expansion of the Universe over its history. The fact that a whole slew of disparate data sets are all consistent with not only one another but with an expanding, evenly filled Universe in the context of relativity, that gives us the confidence we have in our model of the Universe.

But, just as we didn't necessarily accept gravitational waves before they were directly measured by LIGO, there's still the possibility that we've made a mistake somewhere in inferring the properties of the Universe. If we could take a distant object, measure its redshift and distance, and then come back at a later time to see how its redshift and distance had changed, we'd be able to directly (instead of indirectly) measure the expanding Universe for the first time.

Given that our best model of the Universe is that it's 13.8 billion years old, it's easy to see how it could be challenging to measure an appreciable amount of expansion over timescales that human beings are capable of measuring. If we were to take the most distant galaxies and quasars we can measure objects that are tens of billions of light-years away we'd predict that the expected change in redshift-over-time is the equivalent of 1 cm/s per year.

Even with today's most powerful telescopes, we can only measure redshifts to a resolution of about 100-to-200 cm/s, which means we'd have to wait centuries to even begin to measure changes in how we view these distant objects. Despite the discovery of a large number of distant objects, we simply don't have the technological capabilities of making astronomical measurements to the needed precisions.

A comparison of the mirror sizes of various existing and proposed telescopes. When GMT and ELT come... [+] online, they will be the world's largest, at 25 and 39 meters in aperture, respectively.

But when we move from having 10-meter class telescopes to 30-meter class telescopes, with approximately:

the European Extremely Large Telescope (ELT) will likely be the first to make this measurement directly. With the recent new discoveries of many new ultra-distant quasars at a variety of redshifts (a trend that's expected to increase when the Large Synoptic Survey Telescope becomes operational), the ELT should be able to detect the expansion directly.

This diagram shows the novel 5-mirror optical system of ESO's Extremely Large Telescope (ELT).... [+] Before reaching the science instruments the light is first reflected from the telescope's giant concave 39-metre segmented primary mirror (M1), it then bounces off two further 4-metre-class mirrors, one convex (M2) and one concave (M3). The final two mirrors (M4 and M5) form a built-in adaptive optics system to allow extremely sharp images to be formed at the final focal plane. This telescope will have more light-gathering power and better angular resolution, down to 0.005", than any telescope in history.

The ELT is expected to come online in the mid-2020s, and should be capable of measuring the redshifts of individual objects with about a factor of 10 improvement in precision over today's best instruments. With thousands to tens of thousands of quasars expected to be discovered and well-measured at the large distances needed to see this effect, the ELT should be sensitive to changes in redshift that correspond to additional shifts of just 10 cm/s in overall magnitude.

This represents an improvement of a factor of 10-to-20 over existing telescopes, and means that if we wait just a decade (or perhaps a decade-and-a-half) once the ELT comes online at full power, we should be able to measure the expansion of the Universe directly.

Artist's impression of the Extremely Large Telescope (ELT) in its enclosure on Cerro Armazones, a... [+] 3046-metre mountaintop in Chile's Atacama Desert. The 39-meter ELT will be the largest optical/infrared telescope in the world, and much like the GMT, will be able to view almost the entire sky, excepting certain regions only visible from Earth's northern hemisphere.

The key term you'll want to remember as we move into the mid-2030s, the earliest possible time this detection could robustly be made, is redshift drift. By measuring how cosmic redshifts change over time something we've never been able to do to date we'll be able to test a magnificent array of aspects about our Universe. This includes:

By 2040 at the latest, we should be able to directly confirm the expansion of the Universe, putting our understanding of the cosmos to the ultimate test.

A simulation of the accuracy of the redshift drift experiment, which will be achieved by the ELT.... [+] The results strongly depend on the number of known bright quasars at a given redshift. This effect, first predicted in the 1960s, will finally fall within the realm of the directly measurable.

There's a terrible myth about science that is pervasive among the general public: that it's very risky to build a bigger, larger, more powerful apparatus to probe the Universe as never before. That if we go to higher energies, lower temperatures, larger apertures, or other scientific extremes, that our searches might be fruitless and we'll have wasted a tremendous amount of time, money, and effort that could be better spent.

The truth of the matter is that pushing the boundaries of what we're capable of discovering is how we gain the new knowledge that enables us to develop tomorrow's technologies. Whether we discover something new or not is for nature to decide; we have no control over that. What we do have control over is whether we invest in going where no human has ever gone before, in learning what humans have only speculated about, and in expanding the frontiers of what's possible on Earth.

For nearly a century, we've known that the Universe is expanding. In 20 years, tops, we'll have the direct evidence to know exactly how it's happening.

Originally posted here:

This Is How Astronomers Will Finally Measure The Universe's Expansion Directly - Forbes

NORTHAMPTON Internet from outer space. It sounds like a futuristic concept, but according to some astronomers, a planned network of thousands of satellites providing broadband service may actually threaten the future of astronomy.

On Monday, aerospace company SpaceX launched 60 Starlink satellites into orbit, adding on to 60 satellites that were released in May. The satellites currently in orbit are only the beginning of SpaceXs plans the company, headed by tech giant Elon Musk, has received U.S. Federal Communications Commission approval to launch 12,000 Starlink satellites and has requested an allowance of 30,000.

The satellites will provide fast, reliable internet to populations with little or no connectivity, according to a SpaceX press release, including those in rural communities and places where existing services are too expensive or unreliable. The satellite components will also quickly burn up in the Earths atmosphere.

But the futuristic venture has the potential to hide the night sky from both the naked eye and telescopes, according to some astronomers. James Lowenthal, an astronomy professor at Smith College, is among those to voice concerns over the project, primarily related to light pollution.

Were not sure if astronomy can survive in the era of large satellite constellations, Lowenthal said. It might actually be an existential threat.

Lowenthal regularly communicates with SpaceX as a member of the American Astronomical Societys Committee on Light Pollution, Radio Interference and Space Debris. The Starlink satellites raise concern on all three issues the committee looks at, Lowenthal said, though it is mainly focusing on light pollution. The committee has proposed modifications such as darkening the satellites to make them less reflective.

We astronomers need clear dark skies to do our work, and we need skies that are free of moving bright objects, enough at least for us to peer out into the universe and ask the questions we ask, he said.

Light pollution from cities and towns have made these dark skies harder to access, Lowenthal added, but astronomers have always been able to find remote locations such as deserts and mountaintops to conduct their research. But because the satellites would be scattered around the globe, astronomers would not be able to easily avoid them.

Daniela Calzetti, a professor and department head of astronomy at the University of Massachusetts Amherst, also said that Starlink can be in some cases pretty devastating to astronomy. Astronomers sometimes need to throw out observations due to satellite patterns on their images, she said, and with an increasing number of satellites in the sky, this issue will only grow.

There were times when there werent as many satellites, Calzetti said. Things are getting worse and worse.

The Committee on Light Pollution, Radio Interference and Space Debris has had cordial correspondence with SpaceX, Lownenthal said, and the company has expressed a willingness to communicate with us and commendable desire to help fix the problem, with the constraints that theyre still going to launch their satellites. SpaceX has not provided any concrete plans on how it will respond to the issues raised, according to Lowenthal.

A spokeswoman for SpaceX said that the company is actively working with leading astronomy groups from around the world to make sure their work isnt affected and is taking action to make the next wave of Starlink satellite bases black. If needed, the company will also adjust satellite orbits as needed to allow sensitive space observations, she said.

But a lack of international agreements governing the issue intensifies the problem, Calzetti said. As of now, no international law specifically limits parameters such as how many satellites a company can place into orbit.

Calzetti said that she sees the positive impact of the satellites providing more people with an internet connection, but greater regulation of these satellites is needed to ensure the right of people to have safe and reliable communications, and the right of other communities to be able to see the night sky.

Lowenthal said he also recognizes that improved internet access could make positive impacts on human life. But the potential impact of such satellites on the night sky could mean a tragic loss of humanitys ancient connections to the universe, he said.

In my view, Lowenthal said, its not just really up to some private company to take away all of humanitys view of nature at night without full discussion and input from a broad array of people and institutions, and everyone affected.

SpaceX anticipates Starlink will be available in the Northern U.S. and Canada in 2020 and achieve near global coverage of the populated world by 2021, according to the Starlink website.

View original post here:

The end of the night sky as we know it? Local astronomers see SpaceX as threat - GazetteNET

A new database from the American Association of Variable Star Observers enables astronomers (amateur and professional alike) to store data from any variable object in the sky.

A new era of variable star astronomy starts as the American Association of Variable Star Observers (AAVSO) now welcomes spectra from the AAVSO community. The new AAVSO Spectroscopic Database (AVSpec) offers the opportunity for observers worldwide to participate in scientific projects using their own spectroscopic equipment. Alongside light-curve data in AAVSOs photometric database, the AAVSO International Database (AID), spectra in AVSpec will provide new insights on the properties of variable stars, as well as opportunities for more exciting discoveries.

George and I looked at each other and both went huzzah! John Weaver explains of his eureka! moment in developing AVSpec, along with the help of George Silvis, long-time AAVSO volunteer and recent consultant. After three years of mind-bending work, AVSpec is now processing observation submissions and open to use. The database is open data, which means it is free of charge, so that both non-AAVSO and AAVSO members can access AVSpec to view and download the data contributed by AAVSO observers.

Spectroscopy is the study of electromagnetic radiation wavelengths, each of which is emittedby an object or produced through an objects interaction with other matter. In spectroscopy, a spectrum is a range of light separated into different wavelengths, each which projects a unique brightness.

The AAVSOs Spectroscopy Observing Section leader, Ryan Maderak, is responsible for AVSpec user resources and collaboration. He can elaborate at length on the ways in which observing spectra can answer questions poised in human minds since our collective eyes first gazed starward.

In short, Maderak says, the database will fully open the door to science that has only been possible on a restricted basis before now.

Beginner to experienced spectroscopists are encouraged to submit data to AVSpec. Crucial data can be observed and uploaded to the database with and without high-tech equipment.

Weaver, an astrophysicist working towards his Ph.D. in the evolution of galaxies, developed most of the code behind the database. He encourages those who want to increase their proficiency in spectroscopy to take a CHOICE course. The more data submitted by more observers, the better: Maderak stresses that, One piece at a time, our users build a foundation for original scientific results. Spectroscopic observer volunteers with interests in an array of astronomical objects increase the number of once-in-a lifetime events documented.

[AAVSO] understands that some observers may [see] a nova in outburst. That data is very, very, very important to catch, Weaver emphasizes. [The event] doesnt last for a long time. And once its gone, its gone.

This spectrum is of the variable star Theta Circini, taken on August 26, 2019, by AAVSO observer BHQ.

A key collaborator in the construction of AVSpec was an administrator of the Database of Be Star Spectra (BeSS), which archives professional and amateur spectra of Be stars. Before launching AVSpec, numerous volunteers from the AAVSO community tested the code and provided valuable feedback on tool functionality and observer training material. Essentially, AVSpec is a community project it was born through feedback from the AAVSO community, and will grow through continuous feedback and thanks to the communitys continuous support.

AAVSOs verification procedure contributes to setting AVSpec apart from other spectroscopic databases. All spectrasubmitted to the databaseare hand-verified.

The AAVSO is proud of the careful vetting of the data submitted to its databases, AAVSO CEO and Director Stella Kafka explains. Even the most experienced observers may submit discrepant data due to software glitches or unidentified instrumental defects. By checking every spectrum, we ensure high-quality data for the spectra to be of use in scientific projects. We also have the opportunity to give constructive feedback to our observers as they improve their observing, data reduction, and analysis skills. This is part of the scientific process.

As a repository of spectral data that has the backbone of an effective verification process and a strong community of dedicated observers collecting and submitting data on an array of celestial objects, AVSpec will be beneficial to astronomers and the scientific discoveries they make. It will even change the way research is conducted, since AVSpec is supported by a complementary repository of photometric data. More data than ever before can now be found at AAVSO.

This spectroscopic database, along with the educational material and manual accompanying it, is a long-awaited resource for the AAVSO community, Kafka affirms. We are excited to introduce a new chapter in the Associations long history of collecting data.

Go here to read the rest:

Do You Take Spectra? Here's Where to Store Your Data and Contribute to Science - Sky & Telescope

A dirty snowball or snowy dirtball (depending on which astronomer you're talking to) is hurtling towards the Earth at approximately 33 kilometres per second.

It's making astronomers across the globe very excited, because this isn't just any comet we've detected it's a comet from outside our solar system.

"Having an interstellar object around is the most incredibly exciting thing," said astronomer Michele Bannister of Queen's University Belfast.

"It's a piece of another star coming to visit us."

Here are some of the reasons 2I/Borisov has got stargazing scientists so excited.

'Oumuamua was the first interstellar object we detected, back in 2017.

(Supplied: European Southern Observatory/M. Kronmesser)

'Oumuamua was the first interstellar object we detected, back in 2017.

Supplied: European Southern Observatory/M. Kronmesser

The comet has been dubbed Borisov after the amateur astronomer Gennady Borisov who first detected it on August 30 this year.

The 2I in the comet's name stands for second interstellar, meaning it's the second interstellar object we've picked up entering the solar system.

The first was a mysterious cigar-shaped object dubbed 'Oumuamua, a Hawaiian word meaning "a messenger from afar arriving first", that visited us in 2017.

We know Borisov is an interstellar interloper because of the hyperbolic shape of its orbit, which indicates it's not gravitationally bound to the Sun, and the fast speed at which it is travelling.

"These things are sleeting through the solar system all the time, it's just we've finally got to the point where our technology can catch them," said astronomer Jonti Horner of the University of Southern Queensland.

"It would be foolish to imagine we're the only planetary system out there that's spitting things out into space, that's littering the cosmos."

That's because objects like Borisov and 'Oumuamua are a natural outcome of how planetary systems form and evolve, said Dr Bannister.

"Any given planetary system over its lifetime will eject trillions on trillions of these little worlds into the cosmos, and they just wander between the stars," she said.

"It's a galaxy that's not just filled with dark matter, not just filled with bright stars, it's actually filled with flying rocks."

There are a few reasons why we've been able to pick up Borisov on its way towards our Sun, unlike 'Oumuamua which we spotted on its way out of the solar system.

'Oumuamua's approach trajectory was behind the Sun, relative to the Earth, when it was on its way in, which meant our telescopes on Earth couldn't pick it up.

"Rule one of telescopes: you can't point them at the Sun," Dr Bannister said.

If we'd had a telescope on our orbit on the other side of the Sun, we could have had more warning of 'Oumuamua's approach, she said.

Borisov is a proper comet, whereas 'Oumuamua is what Dr Bannister said is best described as "the husk of a comet" with all its ices baked out.

Borisov is more active than 'Oumuamua, with its little coma of sublimating ices. Its brightness it's reflecting the Sun's light rather than emitting any visible light of its own means we can detect it at greater distances from our star.

At two or three kilometres across, it's bigger than 'Oumuamua, which is more the size of a single skyscraper at 200 to 300 metres across, which also helps us see Borisov.

"You actually see comet-type stellar objects for larger distances in the solar system, than you can see little rock-type stellar objects," Dr Bannister said.

The upshot of all this is that it gives astronomers more time to observe Borisov.

'Oumuamua was weird, Professor Horner said.

At first astronomers thought it was a comet.

Then they decided it was an asteroid.

And then some people went back to the comet theory.

And then, there was that whole other school of thought that it was an alien probe, possibly sent here on purpose.

Borisov has not caused any of the same controversy.

"It's the kind of thing where if it was coming in more slowly it would look just like a garden-variety comet," Professor Horner said.

Borisov looks very similar to comets found in our solar system, like this one, 67P/ChuryumovGerasimenko.

(Supplied: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA)

Borisov looks very similar to comets found in our solar system, like this one, 67P/ChuryumovGerasimenko.

Supplied: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA

Don't let the fact that Borisov looks very similar to comets formed in our solar system disappoint you.

"The fact that it's boring is exciting and interesting," Professor Horner said.

He said Borisov's similarity to our comets speaks to how universal the formation of cometary bodies is.

While we've seen a wide diversity of exoplanetary systems across the galaxy, Dr Bannister said, thanks to the efforts of instruments like the Kepler Space Telescope and the TESS (Transiting Exoplanet Survey Satellite), that doesn't mean our solar system is unique.

"What this is telling us is the chemistry that takes place in at least one of those systems, purely by random chance from the heavens, is the same as ours," she said.

"So maybe we're not different after all. Maybe we are in fact a remarkably common kind of solar system."

And that even plays into some of the crazy, science fiction-like ideas that people have come up with over the decades, about life being transferred from planetary system to planetary system by comets, Professor Horner said.

"Given these things are sleeting through the solar system all the time, the Earth will have been hit in the past by comets from another star system," he said.

Interstellar comet 2I/Borisov imaged by the Gemini Observatory.

(Supplied: Gemini Observatory/NSF/AURA)

Interstellar comet 2I/Borisov imaged by the Gemini Observatory.

Supplied: Gemini Observatory/NSF/AURA

Scientists have detected signs of water on Borisov, which we would expect, given that comets are predominantly mixtures of frozen water and other ices.

"So to get water on this thing is just confirmation that comets are comets are comets, wherever they are in the cosmos," Professor Horner said.

"But it's also cool to have water that originates around another star alien water."

Astronomers have also picked up evidence of cyanogens on Borisov, which again isn't that surprising, Dr Bannister said.

"Comets are full of cyanide, it's one of those things," she said.

The more time we get to train our telescopes on Borisov, means we can study in more detail the gas that's coming off it, Professor Horner said.

"If we can get good enough measurements of the gas around the comet, then we'll actually start to be able to dig into the nitty-gritty of the elemental abundances and also isotopic abundances," he said.

"Those might actually tell us a little bit more about the conditions this thing formed in, and maybe they'll reveal subtle differences between our comets and this comet."

'Oumuamua came a lot closer to Earth than Borisov will.

(Wikimedia Commons: nagualdesign; Tomruen)

'Oumuamua came a lot closer to Earth than Borisov will.

Wikimedia Commons: nagualdesign; Tomruen

Borisov will reach its closest approach to the Sun, or the perihelion of its orbit, on December 7, according to the International Astronomical Union.

At that time it will be about two astronomical units from both the Sun and us, or twice the average distance between the Earth and Sun.

"So it's outside the orbit of Mars," Dr Bannister said.

"Whereas 'Oumuamua was what we'd actually call a near-Earth asteroid, it came within 0.25 astronomical units of us."

You'll need a pretty big telescope to see Borisov.

(Flickr CC: Grand Canyon National Park)

You'll need a pretty big telescope to see Borisov.

Flickr CC: Grand Canyon National Park

Borisov is expected to get to a peak magnitude of 16 or 15, which will be a factor of 10,000 times too faint to see with the naked eye, Professor Horner said.

"You'd need probably at least a 10- or 12-inch [25 or 30cm] telescope [to see it], probably bigger than that in all honesty," he said.

If you don't have the equipment to look at it yourself, Professor Horner recommended getting along to your local astronomy group who might have the sort of telescopic equipment to be able to pick it up.

The best times to see Borisov will be during December and January, where it is expected to be at its brightest in the southern sky, before it begins its journey out of our solar system.

If you do get the opportunity to see Borisov, don't expect anything too amazing to look at, Dr Bannister said.

"This is a small, faint, fuzzy thing," she said, although it's been on a very impressive journey.

And could there by one more twist in Borisov's tale?

"We sometimes see comets of this sort coming in from the Oort Cloud [in our solar system] just shred themselves into a cloud of fragments at this point when they get heated," Dr Bannister said.

"Because this may have never been heated by a star before. It could have been travelling for billions of years, we have no way of knowing yet."

If you miss bidding Borisov a fond farewell, don't worry. Scientists are already calculating how to pay it a visit.

More here:

Arrival of interstellar object, comet 2I/Borisov, excites astronomers partly because of how familiar it is - ABC News