Wait long enough -- something like 4.5 billion years -- and we'll have a huge elliptical galaxy resulting from the merger of our own Milky Way with Andromeda (M31). I've always been fascinated with Andromeda because being the nearest large galaxy, and a fine spiral at that, it gives us a look at how our own galaxy must appear from the outside. Its faintness to the naked eye belies its size, an object considerably larger than the Moon from our perspective, though best seen, of course, on a Moonless night. And now we learn it is even bigger than we thought. The Absorption Map of Ionized Gas in Andromeda (Project AMIGA) is the source for this information. A new study coming out of this program uses Hubble data to map the vast gas envelope surrounding Andromeda, a diffuse halo of plasma extending 1.3 million light years from the galaxy and in some directions, as far as 2 million light years. To put this into perspective, Andromeda itself is 2.5 million light years away, meaning that our...

What happens when worlds collide? The question recalls the novel by Philip Wylie and Edwin Balmer, which appeared as a serial in Blue Book magazine beginning in 1932 and concluded the following year. The book version of When Worlds Collide appeared in 1933, and the movie, directed by Rudolph Maté, came out in 1951 in a George Pal production. I would wager that most Centauri Dreams readers have seen it. Let's hope we never share such a fate, but it's likely that collisions are commonplace in the late stages of planet formation, and many researchers believe that Earth's Moon was the result of the collision of our planet with a Mars-sized planet about 4.5 billion years ago. Scientists at Durham University and the University of Glasgow have recently developed computer simulations tracking atmosphere loss during such collisions using the COSMA supercomputer, which is part of the DiRAC High-Performance Computing facility in Durham. The work involves smoothed particle hydrodynamics...

I track brown dwarfs closely because they have so much to teach us about the boundary between planet and star. I’m also intrigued by what might be found on a planet orbiting one of these objects, though life seems unlikely. Brown dwarfs begin losing their thermal energy after formation and continue cooling the rest of their lives, a period I’ve seen estimated at only about 10 million years. We know nothing about how long abiogenesis takes -- not to mention how common it is -- but the outlook for brown dwarf planets and astrobiology seems bleak. It’s intriguing, though, that we’ve identified a number of brown dwarfs with planetary systems, including 2M1207b, MOA-2007-BLG-192Lb, and 2MASS J044144b, and in the latest news from the NEOWISE mission, we have two brown dwarfs that stand out for other reasons. What used to be the Wide-Field Infrared Survey Explorer would become a tool for the detection of near-Earth objects, but data from the earlier WISE incarnation is still turning up red...

"It's fair to say that New Horizons is looking at an alien sky, unlike what we see from Earth." Those are the words of Alan Stern (Southwest Research Institute), who is principal investigator for New Horizons. A breathtaking 7 billion kilometers from Earth, the spacecraft has just returned images showing the parallax effect for two nearby stars. That 'alien sky' would look pretty much the same to the human eye except in the case of the closest stars, but the displacement of both Proxima Centauri and Wolf 359 against the deep space background is apparent in the images below. Proxima Centauri, the nearest star to our own, is shown in the top image, with Wolf 359 in the following one. Image: This two-frame animation blinks back and forth between New Horizons and Earth images of each star, clearly illustrating the different view of the sky New Horizons has from its deep-space perch. Credit: NASA/Johns Hopkins Applied Physics Laboratory/Southwest Research Institute/Las Cumbres...

Some of the fastest outflows in nature are beginning to turn up in the phenomena known as Fast Blue Optical Transients (FBOTs). These are observed as bursts that quickly fade but leave quite an impression with their spectacular outpouring of energy. The transient AT2018cow was found in 2018, for example, in data from the ATLAS-HKO telescope in Hawaii, an explosion 10 to 100 times as bright as a typical supernova that appeared in the constellation Hercules. It was thought to be produced by the collapse of a star into a neutron star or black hole. Now we have a new FBOT that is brighter at radio wavelengths than AT2018cow, the third of these events to be studied at radio wavelengths. The burst occurred in a small galaxy about 500 million light years from Earth and was first detected in 2016. Let's call it CSS161010 (short for CRTS-CSS161010 J045834-081803), and note that it completely upstages its predecessors in terms of the speed of its outflow. The event launched gas and particles...

Our galaxy is 10,000 times more massive than Sagittarius, a dwarf galaxy discovered in the 1990s. But we're learning that Sagittarius may have had a profound effect on the far larger galaxy it orbits, colliding with it on at least three occasions in the past six billion years. These interactions would have triggered periods of star formation that we can, for the first time, begin to map with data from the Gaia mission, a challenge tackled in a new study in Nature Astronomy. The paper in question, produced by a team led by Tomás Ruiz-Lara (Instituto de Astrofísica de Canarias, Tenerife), argues that the influence of Sagittarius was substantial. The data show three periods of increased star formation, with peaks at 5.7 billion years ago, 1.9 billion years ago and 1 billion years ago, corresponding to the passage of Sagittarius through the Milky Way disk. The work is built around Gaia Data Release 2, examining the photometry and parallax information combined with modeling of observed...

Black holes are such exotic objects that they somehow suggest great distance. We're learning about the black holes at the center of many galaxies even as we're just beginning to catalog the location of smaller ones elsewhere. But we're also learning through gravitational wave studies about their interactions and have begun to find black holes closer to home. Thus the just announced discovery of a black hole 1,000 light years from Earth. A long way, to be sure, but the closest ever found to our planet. Evidence for the object comes from the MPG/ESO 2.2-metre telescope at ESO's La Silla Observatory in Chile, deduced by a team of astronomers led by Thomas Rivinius from observations of two companion stars. This is, in other words, a triple system, and one that can be seen with the naked eye at that. The system is located in Telescopium, its stars viewable without binoculars or telescope on a clear southern hemisphere night. In fact, here's where to look. Image: This chart shows the...

Back in January -- and boy does that seem like another era -- I wrote about the plan to look at two nearby stars with the help of the New Horizons spacecraft as well as observations from the general public. If you'd like to get involved, there is still time, but the date is fast approaching. Amateur equipment and digital cameras have reached the point where astronomy at a very high level can be conducted from small observatories and even back yards. Here's another chance to make the case for the value of such work. Tha planned observations take advantage of parallax, the apparent shift in position of nearby stars as measured using the radius of the Earth's orbit. Friedrich Bessel's groundbreaking work on stellar distances involved taking such measurements to calculate the distance of 61 Cygni, all this back in 1838. The apparent shift of the star against background stars allowed him to peg 61 Cygni's distance at 10 light years, reasonably close to the modern figure of 11.4. New...

The SPECULOOS-South Observatory at Cerro Paranal, Chile houses four 1-meter robotic telescopes, now deployed in the service of identifying rocky planets transiting low-mass stars and brown dwarfs. Acronym untanglement: SPECULOOS stands for Search for habitable Planets EClipsing ULtra-cOOl Stars. An early success here is the just reported discovery of a triple brown dwarf system, with an inner binary that is eclipsing and a widely separated brown dwarf companion. The inner binary is what is known as a double-lined system, meaning that spectral lines from both eclipsing stars are visible in the data. Data from the W. M. Keck Observatoy (Maunakea) and the 8-meter Very Large Telescope (VLT), each equipped with sensitive spectrometers, were used to confirm the discovery. Yesterday we saw how the analysis of a young exoplanet, DS Tuc Ab, could offer insights into how 'hot Neptunes' form. In a similar way, the brown dwarf triple system 2M1510A fills a needed gap in our data. A member of a...

Astronomy relies on so-called 'standard candles' to make crucial measurements about distance. Cepheid variables, for example, perhaps the most famous stars in this category, were examined by Henrietta Swan Leavitt in 1908 as part of her study of variable stars in the Magellanic clouds, revealing the relationship between this type of star's period and luminosity. Edwin Hubble would use distance calculations based on this relationship to estimate how far what was then called the 'Andromeda Nebula' was from our galaxy, revealing the true nature of the 'nebula.' In recent times, astronomers have used type Ia supernovae in much the same way, for comparing a source's intrinsic brightness with what is observed in the sky likewise determines distance. The most commonly described type Ia supernovae model occurs in binary systems where one of the stars is a white dwarf, and the assumption among astronomers has been that this category of supernova produces a consistent peak luminosity that can...

Wes Kelly has pursued a lifetime interest in flight through the air, in orbit and even to the stars. Known on Centauri Dreams as 'wdk,' Wes runs a small aerospace company in Houston (Triton Systems,LLC), founded for the purpose of developing a partially reusable HTOL launch vehicle for delivering small satellites to space. The company also provides aerospace engineering services to NASA and other customers, starting with contracts in the 1990s. Kelly studied aerospace engineering at the University of Michigan after service in the US Air Force, and went on to do graduate work at the University of Washington. He has been involved with early design and development of the Space Shuttle, expendable launch systems, solar electric propulsion systems and a succession of preliminary vehicle designs. With the International Space Station, he worked both as engineer and a translator or interpreter in meetings with Russian engineering teams on areas such as propulsion, guidance and control. In...

In a few short months, New Horizons will be almost 8 billion kilometers out, a distance that still boggles the mind until we remember that Voyager 1 has reached 22.2 billion kilometers (over 148 AU). Then, of course, we're humbled again with the thought that the inner Oort Cloud is thought to be between 2,000 and 5,000 AU from the Sun, with an outer edge that could extend as far as halfway to the nearest star. That star, Proxima Centauri, is 268,770 AU from us. As New Horizons hunts Kuiper Belt objects for the next flyby, the spacecraft is now being used to perform parallax studies to detect the apparent 'shift' in the relative position of nearby stars as compared with what we see on Earth. Earth's orbit is about 300 million kilometers in diameter, so we see that apparent shift by comparing observations taken half a year apart. That's a pretty decent baseline, but if we extend the baseline, as now with New Horizons, we can see better parallax effects, and thus tighten the distance...

Farewell to Spitzer after more than 16 years of infrared observations of the universe. We've recently looked at the observatory's accomplishments (see Looking Back at the Spitzer Space Telescope), but I want to run the photo below to celebrate the team that managed it. Image: Spitzer Project Manager Joseph Hunt stands in Mission Control at NASA's Jet Propulsion Laboratory in Pasadena, California, on Jan. 30, 2020, declaring the spacecraft decommissioned and the Spitzer mission concluded. Credit: NASA/JPL-Caltech. Meanwhile, we have the good news that the European Space Agency's CHEOPS (CHaracterising ExOPlanet Satellite), which was launched from Kourou (French Guiana) on December 18, has completed its early orbit phase, involving instrument tests and calibration, and has now opened its telescope cover, exposing the focal plane to starlight. The space observatory carries a 95-cm long baffle that shields its telescope from stray light and minimizes light contamination from sources like...

Cataclysmic variable stars (CVs) are binary phenomena, usually consisting of a white dwarf that is accreting material out of a nearby companion star. As you would imagine, a wide range of CVs in various stages of accretion and subsequent outburst can be detected. When the accretion disk around the white dwarf becomes unstable, we get what is known as a dwarf nova (DN), and in systems with orbital periods less than two hours, there can be much more violent outbursts, feeding off orbital resonances in the orbit of the two stars. Now we have a newly discovered cataclysmic variable (KSN:BS-C11a) in an interesting configuration, a white dwarf apparently feeding off a brown dwarf companion that is about 10 times less massive. The 'super-outburst' from the dwarf nova turned up in data from the decommissioned Kepler Space Telescope. Grad student Ryan Ridden-Harper (Australian National Observatory), lead author of the paper on this work, likes to refer to this cataclysmic variable as 'a...

Yesterday's post on the Spitzer Space Telescope leads naturally to the targets it produced for its successor. For when Spitzer's mission ends on January 30, we have the far more powerful James Webb Space Telescope, also operating at infrared wavelengths, in queue for a 2021 launch. In many ways, Spitzer has been the necessary precursor for JWST, for it was the need to operate a telescope at extremely low temperatures in order to maximize infrared sensitivity that drove Spitzer design. JWST must maintain its gold-coated beryllium mirror at similarly precise temperatures. With over 8,700 scientific papers published based on Spitzer findings, a number that will continue to grow for many years, a path has been charted that JWST will follow in the form of observations early in its mission. Consider WASP-18b, a gas giant of ten times Jupiter mass in a tight orbit around its star. Data from both Spitzer and Hubble showed in 2017 that the planet is laden with carbon monoxide and all but...

The Spitzer Space Telescope, which is to end its mission on January 30, has a special place in my memory. I was making a trip to the Jet Propulsion Laboratory as part of the research for my Centauri Dreams book when I noticed on a monitor a countdown -- still in days -- for the launch of Spitzer, then known as the Space Infrared Telescope Facility (SIRTF). The observatory was launched on the 25th of August, 2003. I remember hot Pasadena weather, a conversation with aerospace legend Adrian Hooke (he was a member of the Kennedy Space Center launch team for Apollo 9, 10, 11 and 12, among much else), a rousing talk with Humphrey "Hoppy" Price about interstellar possibilities. So many good conversations, some serious interviews, and a growing enthusiasm for interstellar flight. But Spitzer had my attention because it was the next mission, one of the Great Observatory missions which included the Hubble Space Telescope, the Compton Gamma Ray Observatory, the Chandra X-ray Observatory, and...

It's always breathtaking to see the band of the Milky Way under good viewing conditions. I remember so well the night I saw it best, about 20 years ago on a cold, absolutely clear night from a boat in the middle of Lake George. This is up in New York's Adirondacks, and when I glanced up as we crossed the lake heading back to our hotel, I was simply stunned by the vista. When you contemplate what you're looking at and think of yourself within that ghostly band, you feel somehow a deep connection to all the myriad processes that put us here as observing beings. Now we have another fine view of the Milky Way, this time from TESS. The scientists working data from the Transiting Exoplanet Survey Satellite have just given us a composite drawn from 208 TESS images taken during the mission's first year of science operations, which ended July 18. Have a look at the southern sky, and realize what while TESS has found 29 exoplanets thus far, another 1,000 or so are in candidate stage and being...

Congratulations to Gennady Borisov, the Crimean amateur who discovered the object now officially designated as 2I/Borisov (with a 0.65-metre telescope he built himself!). That 'I' in the designation points to the object's interstellar origins, and picks up the nomenclature used with the first interstellar object in our system, 1I/'Oumuamua. We've examined thousands of comets over the years but have found none with an orbit as hyperbolic as 2I/Borisov. That means that while the comet's trajectory is being affected by the Sun, it's not going to be captured by it. What's ahead: 2I/Borisov reaches perihelion on 7 December 2019, at which point it will be 2 astronomical units from the Sun and also 2 AU from Earth. It reaches its brightest levels in the southern sky in December and January and then heads back out toward the interstellar deep. So far, it appears that 2I/Borisov is a few kilometers in diameter, and we've also learned -- via the Gran Telescopio Canarias (Canary Islands) --...

The James Webb Space Telescope has been assembled for the first time, meaning its two halves -- the spacecraft and the telescope -- have been connected, following up earlier testing in which the two parts were temporarily connected by ground wiring. The latter took place almost a year ago, in September of 2018, allowing spacecraft and telescope test teams to begin working together as the process pointed to the physical connection that has now been achieved. The connection was completed at Northrop Grumman's facilities in Redondo Beach, California, with the telescope, its mirrors and science instruments, lifted by crane above the sunshield and spacecraft, which had already been combined. With the mechanical connection complete, the next step will be the electrical connection of the two halves and subsequent testng. Image: The fully assembled James Webb Space Telescope with its sunshield and unitized pallet structures (UPSs) that fold up around the telescope for launch, are seen...

As we've been talking about the limitations of giant telescopes in recent days -- and a possible solution in David Kipping's idea of a 'terrascope' -- it pays to keep in mind how our ability to collect light has changed over the years. Thus the figure below, which is drawn from a new paper from Daniel Apai and Tom Milster (both at the University of Arizona) and colleagues. Here we see four centuries of evolution for light-collecting power through refracting and reflecting telescopes, with the introduction of segmented mirrors making larger apertures possible. Image: This is Figure 1 from the paper (click to enlarge). Caption: Evolution of light-collecting area of ground-based (blue, green) and space-based (red) telescopes. The evolution is characterized by alternating stages of slow growth (when existing technology is scalable) and pauses (when existing technology cannot be scaled up). The data points represent the installation of the largest telescopes in their era and are connected...