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Astronomers have discovered a pair of star-like objects orbiting each other extremely quickly, with an entire ‘year’ lasting just 1.9 Earth hours. Catchily named ZTF J2020+5033, the system consists of one object which is definitely a small star, and another that straddles the boundary between star and planet. The two objects appear to be very old, and understanding how they came to be orbiting so close together is teaching astronomers more about how solar systems change and evolve.

The planet-like object in the pair is classified as a Brown dwarf: a failed star without enough mass to jumpstart stellar fusion in its core. But this particular object is right on the boundary between a brown dwarf and a star, so astronomers can’t be sure which it is for sure, though they suspect the latter because it is so much dimmer than its partner.

The brown dwarf’s orbital period is seven times faster than the previous record-holding brown dwarf. It is so close to its partner that both could easily orbit each other inside our Sun. But a paper released this month suggests that they didn’t form like this.

“Both components must have been significantly larger when they were young than they are today, implying that the orbit has shrunk significantly,” the authors write.

Understanding that process is key to unlocking some of the secrets of solar system formation. The primary mechanism at work, they believe, is something called magnetic braking.

Stars have powerful magnetic fields. When solar flares and coronal mass ejections and other phenomena related to solar wind eject material from a star, the material is captured by the magnetic fields. It is carried out far from the star, eventually escaping altogether. But before it escapes, the material continues to spin with the star and its magnetic field. Just like a figure skater throwing their arms out to spin slower, this material slows a star’s spin.

In a binary system, the magnetic fields of both stars work together to slow their orbital period around each other, like two figure skaters holding hands with arms outreached.

Over millennia, not only do the stars lose mass, they also circle closer and closer together.

Current models used by astronomers suggest that magnetic braking is most pronounced in stars that are fully convective: they are massive enough that the convection zone of the star extends all the way into its interior.

But this binary pair is made up of two very small stars that are not fully convective.

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An illustration of the convective zone of massive stars. Credit: ESO.

“This strongly suggests that magnetic braking remains efficient below the fully convective boundary in at least some stars, contrary to the common assumption in many binary evolution models,” the paper argues.

That means that we might need to change how we think about the future evolution of binary pairs.

ZTF J2020+5033, for example, is expected to pass the Roche limit in 1.3 billion years, according to current models. At that time, the brown dwarf will be ripped apart by the gravity of its partner as it gets too close. But if magnetic braking is indeed in effect for these small stars, that timeline will come much faster, within just tens of millions of years.

The implications are clearly significant.

To get a better understanding of what’s going on, astronomers need to find more close-orbiting binary star-brown dwarf pairs, to make sure this isn’t just an outlier. But that’s easier said than done. Although they are expected to be common, brown dwarfs are so dim that they are difficult to find, resulting in what astronomers call a “brown dwarf desert” in their data sets.

Luckily, there are three new instruments that will excel at finding exactly these objects: Palomar Observatory’s wide-field infrared transient explorer (WINTER), which began operations in 2021; the Vera Rubin Observatory, expected to begin surveying in 2024; and the Nancy Grace Roman Space Telescope, launching in 2027.

Learn More:

Kareem El-Badry, Kevin B. Burdge, Jan van Roestel, and Antonio C. Rodriguez. “A transiting brown dwarf in a 2
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Solar Physics: Why study it? What can it teach us about finding life beyond Earth?

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Universe Today has investigated the importance of studying impact craters, planetary surfaces, exoplanets, and astrobiology, and what these disciplines can teach both researchers and the public about finding life beyond Earth. Here, we will discuss the fascinating field of solar physics (also called heliophysics), including why scientists study it, the benefits and challenges of studying it, what it can teach us about finding life beyond Earth, and how upcoming students can pursue studying solar physics. So, why is it so important to study solar physics?

Dr. Maria Kazachenko, who is a solar astrophysicist and assistant professor in the Astrophysical & Planetary Science Department at the University of Colorado, Boulder, tells Universe Today, “Solar physics studies how our Sun works, and our Sun is a star. Stars are building blocks of our Universe.  We are made of stardust. Stars provide energy for life. The Sun is our home star – it affects our life on Earth (space weather, digital safety, astronauts’ safety). Therefore, to be safe we need to understand our star. If we do not take our Sun into account, then sad things could happen. The Sun is the only star where we could obtain high-quality maps of magnetic fields, which define stellar activity. To summarize, studying the Sun is fundamental for our space safety and for understanding the Universe.”

The field of solar physics dates to 1300 BC Babylonia, where astronomers documented numerous solar eclipses, and Greek records show that Egyptians became very proficient at predicting solar eclipses. Additionally, ancient Chinese astronomers documented a total of 37 solar eclipses between 720 BC and 480 BC, along with keeping records for observing visible sunspots around 800 BC, as well. Sunspots were first observed by several international astronomers using telescopes in 1610, including Galileo Galilei, whose drawings have been kept to this day.

Presently, solar physics studies are conducted by both ground- and space-based telescopes and observatories, including the National Science Foundation’s (NSF) Daniel K. Inouye Solar Telescope located in Hawai’i and NASA’s Parker Solar Probe, with the latter coming within 7.26 million kilometers (4.51 million miles) of the Sun’s surface in September 2023. But with all this history and scientific instruments, what are some of the benefits and challenges of studying solar physics?

Dr. Kazachenko tells Universe Today that some of the scientific benefits of studying solar physics include “lots of observations; lots of science problems to work on; benefits from cross-disciplinary research (stellar physics, exoplanets communities)” with some of the scientific challenges stemming from the need to use remote sensing, sometimes resulting in data misinterpretation. Regarding the professional aspects, Dr. Kazachenko tells Universe Today that some of the benefits include “small and friendly community, large variety of research problems relying on amazing new observations and complex simulations, ability to work on different types of problems (instrumentation, space weather operation, research)” with some of the professional challenges including finding permanent employment, which she notes is “like everywhere in science”.

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Image of the Sun obtained by NASA’s Solar Dynamics Observatory (SDO) on June 20, 2013, with a solar flare discharging on the left side. (Credit: NASA/SDO)

As noted, the study of solar physics involves investigating space weather, which is when the solar wind interacts with the Earth, specifically with our magnetic field, resulting in the beautiful auroras observed in the high northern and southern latitudes. On occasion, the solar wind is strong enough to wreak havoc on satellites and even knock out power grids across the Earth’s surface. This was demonstrated with the Carrington Event on September 1-2, 1859, when fires at telegraph stations were reported across the globe, along with several strong aurora observations, as well. While this event occurred with the Earth’s magnetic field largely deflecting the incoming solar wind, life on this planet could be doomed without our magnetic field protecting us. Therefore, what can solar physics teach us about finding life beyond Earth?

Dr. Kazachenko tells Universe Today, “The Sun can tell us about stellar activity, including flares and coronal mass ejections that might be crucial
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Gravastars are an Alternative Theory to Black Holes. Here’s What They’d Look Like

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One of the central predictions of general relativity is that in the end, gravity wins. Stars will fuse hydrogen into new elements to fight gravity and can oppose it for a time. Electrons and neutrons exert pressure to counter gravity, but their stability against that constant pull limits the amount of mass a white dwarf or neutron star can have. All of this can be countered by gathering more mass together. Beyond about 3 solar masses, give or take, gravity will overpower all other forces and collapse the mass into a black hole.

While black holes have a great deal of theoretical and observational evidence to prove their existence, the theory of black holes is not without issue. For one, general relativity predicts that the mass compresses to an infinitely dense singularity where the laws of physics break down. This singularity is shrouded by an event horizon, which serves as a point of no return for anything devoured by the black hole. Both of these are problematic, so there has been a long history of trying to find some alternative. Some mechanism that prevents singularities and event horizons from forming.

One alternative is a gravitational vacuum star or gravitational condensate star, commonly called a gravastar. It was first proposed in 2001, and takes advantage of the fact that most of the energy in the universe is not regular matter or even dark matter, but dark energy. Dark energy drives cosmic expansion, so perhaps it could oppose gravitational collapse in high densities.

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Illustration of a hypothetical gravastar. Credit: Daniel Jampolski and Luciano Rezzolla, Goethe University Frankfurt

The original gravastar model proposed a kind of Bose-Einstein condensate of dark energy surrounded by a thin shell of regular matter. The internal condensate ensures that the gravastar has no singularity, while the dense shell of matter ensures that the gravastar appears similar to a black hole from the outside. Interesting idea, but there are two central problems. One is that the shell is unstable, particularly if the gravastar is rotating. There are ways to tweak things just so to make it stable, but such ideal conditions aren’t likely to occur in nature. The second problem is that gravitational wave observations of large body mergers confirm the standard black hole model. But a new gravastar model might solve some of those problems.

The new model essentially nests multiple gravastars together, somewhat like those nested Matryoshka dolls. Rather than a single shell enclosing exotic dark energy, the model has a layers of nested shells with dark energy between the layers. The authors refer to this model as a nestar, or nested gravastar. This alternative model makes the gravastar more stable, since the tension of dark energy is better balanced by the weight of the shells. The interior structure of the nestar also means that the gravitational waves of a nestar and black hole are more similar, meaning that technically their existence can’t be ruled out.

That said, even the authors note that there is no likely scenario that could produce nestars. They likely don’t exist, and it’s almost certain that what we observe as black holes are true black holes. But studies such as this one are great for testing the limits of general relativity. They help us understand what is possible within the framework of the theory, which in turn helps us better understand gravitational physics.

Reference: Jampolski, Daniel and Rezzolla, Luciano. “Nested solutions of gravitational condensate stars.” Classical and Quantum Gravity 41 (2024): 065014.

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Japan’s New H3 Rocket Successfully Blasts Off

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Japan successfully tested its new flagship H3 rocket after an earlier version failed last year. The rocket lifted off from the Tanegashima Space Center on Saturday, February 17, reaching an orbital altitude of about 670 kilometers (420 miles). It deployed a set of micro-satellites and a dummy satellite designed to simulate a realistic payload.

With the successful launch of the H3, Japan will begin transitioning away from the previous H-2A rocket which has been in service since 2001 and is set to be retired after two more launches. Several upcoming missions depend on the H3, so this successful test was vital.

The launch came after two days of delays because of bad weather. The H3 rocket, built by Mitsubishi Heavy Industries, is now set to become the main launch vehicle of Japan’s space program. The rocket’s first flight in March 2023 failed to reach orbit, which resulted in the loss of an Earth imaging satellite.

The successful launch and deployment of the satellites was a relief for JAXA and members of the project. A livestream of the launch and subsequent successful orbit insertion showed those in the JAXA command cheering and hugging each other.

“I now feel a heavy load taken off my shoulders,” said JAXA H3 project manager Masashi Okada, speaking at a press briefing after the launch. “But now is the real start for H3, and we will work to steadily improve it.”

H3 stands about 57-meter (187-feet) tall and is designed to carry larger payloads. The two microsatellites were deployed approximately 16 minutes and 43 seconds after liftoff. They included an Earth observation satellite named CE-SAT-IE, developed by Canon Electronics, and TIRSAT, an infrared Earth observation instrument that will observe the temperature of the Earth’s surface and seawater.

“We feel so relieved to be able to announce the good results,” JAXA President Hiroshi Yamakawa said at the briefing. Yamakawa added that the main goals of H3 are to secure independent access to space and allow Japan to be competitive as international demand for satellite launches continues to grow. “We made a big first step today toward achieving that goal,” he said.

Image of SLIM lander on moon
An image sent back by a mini-probe shows Japan’s SLIM lander on its side on the lunar surface. (JAXA / Takara Tomy / Sony Group / Doshisha Univ.)

The successful launch comes after two other recent successes for JAXA last month where the H-2A rocket successfully placed a spy satellite into orbit, and just days later JAXA’s robotic SLIM (Smart Lander for Investigating Moon) made the first-ever precise “pinpoint” Moon landing – although unfortunately the lander came down on its side. However, during the final stages of the descent two autonomous rovers were successfully deployed: a tiny hopping robot and the other designed to roll about the surface. Both have sent back pictures and can continue exploring and sending back information even if SLIM cannot be operated.

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