Astronomy

Kuiper Belt Object Arrokoth, the farthest object ever explored by a spacecraft, likely tastes sweet — and soapy.

Bill Anders, who as an Apollo 8 astronaut was one of the first people to fly to the moon in 1968, was killed on June 7 when the vintage plane he was piloting crashed off the coast of Washington.

No one, presently, sees the Moon rotate like this.

Get out your

I’ve seen some pretty incredible things using my eyes.. First off of course, is the stunning sight of a dark star filled sky, then there is the incredible sight of the Andromeda Galaxy 2.5 million light years away. Planets too can of course be seen as they slowly move across the sky but it’s a little more unusual to see something that reminds us the Universe changes. Well, we have an opportunity  in just a few weeks time. The star T Corona Borealis (T CrB) will brighten about 1,500 times so it can be seen with the unaided eye. Miss it though and you will have to wait another 80 years!

It’s always exciting to see something new in the sky. It doesn’t happen all that often but when it does, well it’s definitely an opportunity to get out and enjoy the show. The event is a nova which translates from Latin meaning new. In astronomy, we talk of nova as a number of different phenomena which herald the appearance of something new which is visible in the sky. A supernova is a well known example marking a colossal stellar explosion.

In the case of TCrB it refers to a binary star system where a white dwarf star (the remains of a star like the Sun) is in orbit around another star. I should clarify that statement, they both orbit around a common centre of gravity. At a distance of 3,000 light years, it is one of the closest of its type and so when it goes into outburst, we will get to see it without  any telescope or binoculars, just the ‘Mark-1 eyeball.’ 

The process that leads to the sudden brightening is really quite fascinating. The white dwarf star is a much higher pull of gravity compared to its companion. As a result, it drags material from its stellar neighbour in a process known as accretion. Over time – and in the case of T CrB it takes about 80 years – hydrogen builds up on the white dwarf. The layer of hydrogen is heated up by the white dwarf causing it to heat to critically high temperatures, high enough to initiate hydrogen fusion. The layer of hydrogen detonates and gets ejected from the white dwarf in a brightly glowing, hot shell. Here on Earth, we see this as a sudden brightening of a previously rather inconspicuous star that would ordinarily need a telescope to see.

Nova are generally quite unpredictable, usually occurring once and often leading to the death of a star but in this case, it occurs every 80 years. We call this event a recurrent nova. Its outburst was first seen in 1866 by an astronomer called John Birmingham who, amusingly came from Ireland and not Birmingham. It was seen again in 1946 when there was a drop in brightness before the explosion and it is this drop in brightness that has just been observed over the last couple of months. 

This all points to the next nova event being imminent, perhaps just a month or two away so, if you like me, are keen to see this once in a lifetime event then it’s time to get your coat on and get outside. Unfortunately, because we don’t know exactly when it is going to occur the best approach is to simply become familiar with the sky in the region of the constellation Corona Borealis. 

Alphecca is the brightest star in a C-shaped pattern of stars: the constellation Corona Borealis. It’s near the bright star Arcturus on the sky’s dome. Credit: EarthSky

Thankfully, Corona Borealis is in a fairly ‘quiet’ part of the sky with not too many bright stars. To find it from where you are then use an app on a smartphone to locate Vega in Lyra and Arcturus in Bootes, Corona Borealis is approximately between the two and looks somewhat like a semicircle of stars. Get to know that part of the sky and become familiar with the stars visible to the naked eye. Keep watching over the weeks and months ahead (and of course keep an eye on Universe Today) and at some point soon, you will see a ‘new’ star appear just outside the semicircle. 

Good luck and clear skies. 

Source : Keep your eyes on the sky for a new star as “once in a lifetime” cosmic explosion looms

The post We’re Now Just Weeks Away from a Stellar Explosion You Can See With Your Own Eyes appeared first on Universe Today.

NASA's Mars Sample Return mission has faced quite a few hurdles, and the agency has selected ten studies to try and find more affordable and quicker means of going about the project.

We live in a Universe studded with black holes. Countless stellar mass and supermassive ones exist in our galaxy and most others. It’s likely they existed as so-called “primordial” black holes in the earliest epochs of cosmic history. Yet, there seems to be a missing link category: intermediate-mass black holes (IMBH). Astronomers have searched for these rare beasts for years and there’s only one possible observation thanks to gravitational-wave data. So, where are they?

IMBH might be hidden away in the hearts of globular clusters. But, given the tightly packed nature of those compact collections of stars, how would we know if they contained any IMBH? Teams of researchers in Japan and China came up with a couple of ways to search them out. One is to look for fast-moving stars ejected from globular clusters. The other is to do simulations of collisions of stars in the hearts of newly forming clusters. Both methods may point the way to more IMBH discoveries.

What Are Intermediate-mass Black Holes?

These rare objects are pretty much what their name says: black holes with masses somewhere between their stellar-mass cousins and the supermassive behemoths at the hearts of galaxies. They can contain as little as a thousand times the mass of the Sun, which would be fairly “small”, up to maybe a million solar masses. Beyond that are the supermassive monsters with millions or billions of times the mass of the Sun. The IMBH don’t come from supernova explosions, since there’s no massive star big enough to collapse to produce an IMBH. The birth of an IMBH should involve multiple massive objects coalescing together. This makes them more like their big supermassive black hole siblings.

So, where would such a collisional event happen? It would help if you had a dense agglomeration of stars tightly packed together. That describes globular clusters to a T. They’re crowded with stars, and likely have a good collection of very massive ones. Those are the stars that explode as supernovae and collapse down to produce a stellar-mass black hole. If enough of them exist in the cluster, they could merge and create an IMBH. Another suggestion to create an IMBH is for massive stars to collide to create a single more-massive object.

Many globular clusters orbit the core of the Milky Way Galaxy. Some of the densest ones have millions of stars pulled together by gravity. The cluster Messier 15 (M15) is a good example. It contains more than 100,000 stars crammed into an area of space about 175 light-years across. If runaway star collisions or stellar-mass black hole mergers occurred in M15, that could be enough to create an IMBH.

Simulating Globular Clusters and Intermediate-Mass Black Hole Growth

Another idea is to explore the formation of globulars to see if it produces any clues to the origins and existence of IMBH. That’s what a team of scientists at the University of Tokyo did. They created advanced simulations of star cluster formation to see if massive-star collisions could occur and lead to the birth of IMBH. It’s not an easy task. Previous simulations suggested stellar winds would blow away the needed masses to create these missing black holes.

“Star cluster formation simulations were challenging because of the simulation cost,” said team leader Michiko Fujii. “We, for the first time, successfully performed numerical simulations of globular cluster formation, modeling individual stars. By resolving individual stars with a realistic mass for each, we could reconstruct the collisions of stars in a tightly packed environment. For these simulations, we have developed a novel simulation code, in which we could integrate millions of stars with high accuracy.”

A simulated star cluster forming in a giant molecular cloud. Could this visualization help astronomers understand the formation of intermediate-mass black holes in clusters? Courtesy: Takaaki Takeda (VASA Entertainment, Inc.)

The resulting simulation run showed that runaway collisions brought very massive stars together. These are perfect candidates to end up as IMBH candidates. “Our final goal is to simulate entire galaxies by resolving individual stars,” Fujii points to future research. “It is still difficult to simulate Milky Way-size galaxies by resolving individual stars using currently available supercomputers. However, it would be possible to simulate smaller galaxies such as dwarf galaxies. We also want to target the first clusters, star clusters formed in the early universe. First clusters are also places where IMBHs can be born.”

Runaway Stars and IMBH

Okay, so simulations show that such IMBH could be possible in the globular cluster environment, but what’s the physical proof they actually exist? No one has actually detected the collisions of stellar-mass black holes inside a cluster to create an IMBH. Nor have they seen stellar collisions that might create a monster object — although the Japanese simulations proved they can happen. The trick now is to observe both types of event. Until that happens, astronomers can figure out if IMBH exist through indirect means.

A Chinese research team, led by Yang Huang of the University of the Chinese Academy of Sciences, recently posted a paper about a high-velocity star fleeing the scene of a collision in the heart of Messier 15. The star, called J0731+3717, was ejected by an encounter with an intermediate-mass black hole embedded very close to the center of the cluster.

J0731+3717 got tossed out on its high-speed journey about 21 million years ago. The team examined its metallicity (that is, its ratios of hydrogen and heavier elements (called “metals” by astronomers)) and found that it matches the stars in M15. The rogue star moves away from the cluster at a velocity of about 550 kilometers per second and once “lived” at a distance of about 1 AU from the cluster’s core. The team analyzed those measurements and did reverse orbital calculations of that star (and others within 5 kpc of the Sun). Based on their calculations, they concluded the star had a too-close encounter with an intermediate-mass black hole containing about 100 solar masses.

The team suggests that this method be used to prove the existence of other IMBH in similar environments. They conclude their paper with a look at future observations to prove the concept. “With the increasing power of ongoing Gaia and large-scale spectroscopic surveys, we expect to discover dozens of cases within the 5kpc volume and ten times more within a 10kpc volume, which should shed light on the understanding of the evolutionary path from stellar-mass BHs to SMBHs.”

For More Information

Simulations Yield New Intermediate Mass Black Holes Recipe
Medium and Mighty: Intermediate-mass Black Holes Can Survive in Globular Clusters
A High-velocity Star Recently Ejected by an Intermediate-mass Black Hole in M15

The post Globular Clusters Should Contain More Intermediate-mass Black Holes appeared first on Universe Today.

A Florida redbelly turtle casts a suspicious look as he is being photographed on the grounds of NASA's Kennedy Space Center in Florida. The redbelly turtle inhabits ponds, lakes, sloughs, marshes and mangrove-bordered creeks, in a range that encompasses Florida from the southern tip north to the Apalachicola area of the panhandle. Active year-round, it is often seen basking on logs or floating mats of vegetation. Adults prefer a diet of aquatic plants. The Center shares a boundary with the Merritt Island National Wildlife Refuge, which encompasses 92,000 acres that are a habitat for more than 331 species of birds, 31 mammals, 117 fishes, and 65 amphibians and reptiles. The marshes and open water of the refuge provide wintering areas for 23 species of migratory waterfowl, as well as a year-round home for great blue herons, great egrets, wood storks, cormorants, brown pelicans and other species of marsh and shore birds, as well as a variety of insects.

Virgin Galactic launched its seventh commercial spaceflight mission on June 8 during the final flight of its VSS Unity suborbital spaceplane.

SpaceX landed one of its Falcon 9 rockets for the 300th time tonight (June 7), notching the milestone during a Starlink satellite launch.

A kneecap and two teeth found in Germany have been identified as belonging to a new species of ape from 11.6 million years ago, thought to have weighed as little as 10 kilograms

A kneecap and two teeth found in Germany have been identified as belonging to a new species of ape from 11.6 million years ago, thought to have weighed as little as 10 kilograms

Jupiter and Earth's oceans have more in common than you might think.

An exotic molecule stabilized by intense pressure found in the icy depths of Neptune and Uranus could help explain a long-standing mystery.

SpaceX successfully launched its Starship rocket the day after Boeing’s Starliner craft made its first crewed flight, a sign that the space industry is hotting up

SpaceX successfully launched its Starship rocket the day after Boeing’s Starliner craft made its first crewed flight, a sign that the space industry is hotting up

Mexico and the southern US have seen extreme temperatures due to a heat dome, a weather phenomenon that will become more intense with climate change

Mexico and the southern US have seen extreme temperatures due to a heat dome, a weather phenomenon that will become more intense with climate change

The United States Air Force and U.S. Space Force conducted two routine test launches of unarmed intercontinental ballistic missiles this week from Vandenberg Space Force Base.